JPH09236338A - Heat pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pump capable of improving cooling efficiency of a motor. SOLUTION: There are provided a refrigerant circulation closing flow passage 1 including first and second stage compressors 4, 5, an oil separation recovery unit 6, a condenser 7, a first expansion valve 8, and an evaporator 9, a motor cooling flow passage 3 for cooling a motor 14 for driving the compressors 4, 5 with a refrigerant, and an oil supply flow passage 2 reaching from a lower part of the oil separation recovery unit 6 to oil injection portions of the compressors 4, 5 through an oil cooler 11. The motor cooling flow passage 3 is branched from the circulation closing flow passage 1 on a primary side of the first expansion valve 8 and is extended to reach the oil cooler 11 after passage through a second expansion valve 13 and the motor 14, and is passed heat exchangeably with oil in the oil cooler 11 and is communicated with an intermediate flow passage located between the first stage compressor 4 and the second stage compressor 5. There is further provided a temperature sensitive cylinder 15 on the secondary side motor cooling flow passage 3 of the oil cooler 11 for adjusting an opening of a second expansion valve 13 such that the overheating of the refrigerant is detected and the same overheating at the detection position is zero or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pump of a type in which a stator portion of a motor for driving a compressor is cooled with a refrigerant (herein, a refrigerator is also included).

[0002]

2. Description of the Related Art Conventionally, a motor for driving a compressor is arranged in a suction part of a compressor, and sucked refrigerant gas is sucked into the compressor through a gap between a stator part and a rotor part of the motor. A heat pump employing a one-stage semi-hermetic compressor for cooling a motor is well known (Japanese Patent Laid-Open No. 1-1999).
237389).

A heat pump shown in FIG. 3 is known (Japanese Patent Laid-Open No. 7-180917). This heat pump includes a low pressure side first stage compressor 21, a high pressure side second stage compressor 22, a condenser 23, an economizer 24, and a first expansion valve 2.
5, and a closed circulation flow path 27 for the refrigerant including the evaporator 26
And a stator portion of a motor 29 that branches from the closed circulation flow path 27 on the primary side of the first expansion valve 25 and drives the first-stage and second-stage compressors 21 and 22 via the second expansion valve 28. And a motor cooling passage 30 communicating with the gas confining space in the rotor chamber that does not communicate with either the suction port or the discharge port of the second-stage compressor 22.

Also, the circulation closed flow path 2 on the secondary side of the evaporator 26 is provided.
7, a first temperature sensitive cylinder 31 is provided, and a second temperature sensitive cylinder 32 is provided in the motor cooling flow path 30 on the secondary side of the motor 29, and the degree of superheat of the refrigerant at each location is detected. The openings of the first and second expansion valves 25 and 28 are adjusted so that the degree of superheat of the refrigerant at each detection position becomes zero or more. Furthermore, the primary side of the economizer 24 branches from the closed circulation flow path 27, passes through the third expansion valve 33, and passes through the economizer 24 so as to exchange heat with the refrigerant in the closed circulation flow path 27. A third temperature sensitive cylinder 36 for detecting the degree of superheat of the refrigerant is also provided in the secondary side portion of the economizer 24 in the flow path 35 leading to the intermediate flow path 34 that communicates the stage compressors 21 and 22, and the same as above. In addition, the opening degree of the third expansion valve 33 is adjusted so that the degree of superheat at this detection position becomes zero or more.

[0005]

Among the conventional heat pumps described above, in the case of the heat pump described in JP-A-1-237389, the motor is cooled by the refrigerant that is vaporized by the evaporator and becomes a gas state. However, there is a problem that the cooling efficiency of the motor is poor because the gas is cooled by a gas having a smaller heat transfer coefficient than liquid.

On the other hand, in the case of the heat pump shown in FIG. 3, the liquid refrigerant is supplied to the motor 29 through the motor cooling flow passage 30 and the refrigerant is evaporated while passing through the motor 29, so that the motor 29 is driven. Since the cooling medium is used to cool the motor 29, the refrigerant liquid having a larger heat transfer coefficient than the refrigerant gas is used, and the latent heat when the refrigerant liquid evaporates is used. It can be said that the cooling efficiency of the motor is better than that in the case of cooling the motor. However, in this heat pump, the motor 29
Since the refrigerant that has exited is directly injected into the gas confined space of the compressor 22, the refrigerant is injected near the outlet in the motor 29 so as not to cause liquid compression that causes damage to the compressor 22. It must be completely gasified.

FIG. 4 shows how the state of the refrigerant changes in the motor 29.
In reality, almost all of the liquid is in the lower portion as shown by the hatched portion, but the ratio of the gas state increases as it approaches the outlet portion, and the motor 29 comes out in a superheated state, for example, at a superheat degree of 5 ° C. , Injected into each compressor. Therefore, near the outlet of the motor 29, the refrigerant is almost in a gas state, and the cooling efficiency in the vicinity of the outlet of the motor 29, actually, in the upper portion is reduced, and the upper portion of the motor 29 has an abnormally high temperature. . The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a heat pump capable of improving cooling efficiency of a motor.

[0008]

In order to solve the above problems, the present invention provides at least an oil separation / recovery device, a condenser, a first expansion valve, and an evaporator in addition to a one-stage or multiple-stage compressor. A circulating closed flow path of the refrigerant including the flow path, a motor cooling flow path for cooling the motor that drives the compressor with the refrigerant, and a bearing of the compressor from at least an oil cooler through a lower portion of the oil separation and recovery device. In a heat pump provided with an oil supply flow path leading to an oil injection point such as a shaft seal portion and a rotor chamber, the motor cooling flow path is branched from the circulation closed flow path on the primary side of the first expansion valve. , The second expansion valve, the motor, the oil cooler, the oil in the oil cooler to allow heat exchange with the oil cooler, and the suction of the compressor closest to the evaporator. Between the port and the outlet of the compressor closest to the oil separator While communicating with a space that does not communicate with either the inlet or the outlet, the degree of superheat of the refrigerant is detected in the motor cooling flow path on the secondary side of the oil cooler, and the refrigerant at the detection position A temperature sensitive cylinder for adjusting the opening degree of the second expansion valve is provided so that the degree of superheat becomes zero or more.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a heat pump according to the present invention, which includes a closed circulation flow path 1 for a refrigerant, an oil supply flow path 2, and a motor cooling flow path 3. The circulation closed flow path 1 includes a low pressure side first stage compressor 4, a high pressure side second stage compressor 5, an oil separation / recovery device 6, a condenser 7, a first expansion valve 8 and an evaporator 9, and is well known. Of the heat pump cycle. Further, on the secondary side of the evaporator 9, there is provided a first temperature sensitive tube 12 for detecting the degree of superheat of the refrigerant here, and the first temperature sensitive tube 12 is arranged so that the degree of superheat becomes zero or more. Thus, the opening degree of the first expansion valve 8 is adjusted.

The oil supply flow path 2 extends from the oil retaining portion 10 below the oil separation / recovery device 6, passes through the oil cooler 11, and then the first
Stages, 2nd stage compressors 4, 5 Bearings / shaft seals, rotor chambers, and other oiling points were reached, and after cooling oil was injected into these oiling points, they were collected and provided for recycling. It is a thing. The motor cooling flow path 3 branches off from the closed circulation flow path 1 on the primary side of the first expansion valve 8, and is connected to the second expansion valve 13 and the first expansion valve 8.
Through the stator portion of the motor 14 that drives the first and second stage compressors 4 and 5, and further through the oil cooler 11 to the intermediate flow path between the first stage compressor 4 and the second stage compressor 5. I am joining.
In the oil cooler 11, heat exchange is performed between the refrigerant flowing through the motor cooling flow path 3 and the oil flowing through the oil supply flow path 2, the refrigerant takes heat from the oil, and the oil is cooled. Further, the motor cooling passage 3 on the secondary side of the oil cooler 11 is provided with a second temperature sensitive tube 15 for detecting the degree of superheat of the refrigerant in the passage, and the degree of superheat is zero or more. Therefore, the opening degree of the second expansion valve 13 is adjusted by the second temperature sensing cylinder 15.

As described above, in this heat pump, the refrigerant flowing through the motor cooling flow path 3 is not completely evaporated at the place where the motor 14 is exited, but is completely evaporated at the place where the oil cooler 11 is exited. Therefore, the motor 14 can be efficiently cooled by the liquid-state refrigerant having a larger heat transfer coefficient than the gas-state refrigerant. Further, even near the outlet of the motor 14, most of the refrigerant is in a liquid state, and the latent heat at the time of evaporation of the refrigerant can be sufficiently used for cooling the motor 14, so that the cooling efficiency is further improved.

Further, since the oil is cooled by the refrigerant in the oil cooler 11, it is not necessary to separately provide a cooling medium such as cooling water for oil cooling outside the heat pump, and the structure is simple. Besides, it can be used in a place where there is no cooling water source.
In addition, in FIG. 1, the motor cooling flow path 3 is shown to be joined to the intermediate flow path, but the present invention is not limited to this, and the joining portion of the motor cooling flow path 3 is It may be at any position between the suction port of the first-stage compressor 4 and the discharge port of the second-stage compressor 5 and as long as it does not communicate with either the suction port or the discharge port. .

FIG. 2 shows another heat pump according to the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals.
In this heat pump, the merging portion is positioned so as to communicate with the gas confining space in the rotor chamber that does not communicate with either the suction port or the discharge port of the second stage compressor 5. With such a configuration, as in the heat pump shown in FIG. 1, the cooling efficiency can be improved with a simple configuration, and it can be used in a place where there is no cooling water source.

[0014]

As is apparent from the above description, according to the present invention, at least an oil separation / recovery device, a condenser, a first expansion valve, and an evaporator are provided in addition to the one-stage or multi-stage compressor. A circulating closed flow path of the refrigerant including the flow path, a motor cooling flow path for cooling the motor that drives the compressor with the refrigerant, and a bearing of the compressor from at least an oil cooler through a lower portion of the oil separation and recovery device. In a heat pump provided with an oil supply flow path leading to an oil injection point such as a shaft seal portion and a rotor chamber, the motor cooling flow path is branched from the circulation closed flow path on the primary side of the first expansion valve. , The second expansion valve, the motor, the oil cooler, the oil in the oil cooler to allow heat exchange with the oil cooler, and the suction of the compressor closest to the evaporator. Between the port and the outlet of the compressor closest to the oil separator Mouth, along with communicating the space without communicating to any of the discharge port, to detect the degree of superheat of the refrigerant in the motor cooling flow path of the secondary side of the oil cooler,
A temperature sensitive tube is provided to adjust the opening degree of the second expansion valve so that the degree of superheat of the refrigerant at the detection position becomes zero or more.

As described above, in this heat pump, since the motor is cooled by the refrigerant having a large liquid state ratio up to the outlet of the motor, the cooling efficiency of the motor can be improved. Further, since the oil in the oil cooler is cooled by a refrigerant used by the heat pump itself, that is, a so-called own refrigerant, it is not necessary to introduce cooling water from the outside from a pipe, and a simple structure can be obtained. The heat pump can be used even in a place where there is no cooling water source.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a heat pump according to the present invention.

FIG. 2 is a diagram showing an overall configuration of another heat pump according to the present invention.

FIG. 3 is a diagram showing an overall configuration of a conventional heat pump.

FIG. 4 is a diagram showing how the state of the refrigerant changes in the motor.

[Explanation of symbols]

1 Circulation Closed Flow Path 2 Oil Supply Flow Path 3 Motor Cooling Flow Path 4, 5 First Stage, Second Stage Compressor 6 Oil Separation and Recovery Device 7 Condenser 8 First Expansion Valve 9 Evaporator 11 Oil Cooler 13th 2 expansion valve 14 motor 15 second temperature sensitive tube

Claims (1)

[Claims] 1. A closed circulation flow path of a refrigerant including at least an oil separation / recovery device, a condenser, a first expansion valve, and an evaporator, in addition to a one-stage or a plurality of stages of compressor, and the compressor. A motor cooling flow path for cooling the motor with the refrigerant, and an oil supply from the lower part of the oil separation and recovery device through at least the oil cooler to the bearing / shaft seal part of the compressor, the oiling place such as the rotor chamber. A heat pump provided with a flow path, wherein the motor cooling flow path is branched from the circulation closed flow path on the primary side of the first expansion valve, passes through the second expansion valve, the motor, and then the oil cooler. To pass through the oil cooler so that heat can be exchanged with the oil in the oil cooler, and the suction port of the compressor closest to the evaporator and the discharge of the compressor closest to the oil separation / collector. A space that does not communicate with either the suction port or the discharge port with the outlet While communicating with each other, the degree of superheat of the refrigerant is detected in the motor cooling flow path on the secondary side of the oil cooler, and the second expansion valve is opened so that the degree of superheat of the refrigerant at the detection position becomes zero or more. A heat pump characterized by being formed by providing a temperature sensitive tube for adjusting the degree.