US20050254977A1

US20050254977A1 - Hermetic compressor and refrigeration unit

Info

Publication number: US20050254977A1
Application number: US11/125,031
Authority: US
Inventors: Toru Aya; Katsunori Onobayashi
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp
Priority date: 2004-05-13
Filing date: 2005-05-09
Publication date: 2005-11-17

Abstract

A hermetic compressor comprises a hermetic container, an electric motor and a compressing mechanism installed inside of the hermetic container, lubricating oil and refrigerant gas enclosed within the hermetic container, a first temperature detector disposed to a predetermined location within the hermetic container, and a second temperature detector disposed to a location adjacent to a surface of the lubricating oil in the hermetic container. The predetermined location where the first temperature detector is disposed is one of a location near an upper end and another location near a lower end within a space inside the hermetic container, and an amount of the lubricating oil in the hermetic container is determined according to temperatures detected by the first temperature detector and the second temperature detector.

Description

FIELD OF THE INVENTION

The present invention relates to a hermetic compressor for compressing refrigerant, and a refrigeration unit provided with the same.

BACKGROUND OF THE INVENTION

A hermetic compressor constructed of a compressing mechanism and an electric motor sealed hermetically inside a hermetic container of welded structure is hitherto known as one kind of compressor. One such example is disclosed in Japanese Patent Unexamined Publication, No. H06-159274. Hermetic compressors of this kind are highly reliable and used widely for air conditioners and refrigerators since they do not leak refrigerant, and eliminate a possibility of allowing entry of moisture and the like.
The above hermetic compressor requires electric power to be supplied to the motor inside the hermetic container. For this purpose, it is provided with a so-called hermetic terminal having a high resistance to pressure and air-tightness welded to the hermetic container, so that the electric power is supplied to the motor through this hermetic terminal.
The above hermetic compressor supplies lubricating oil stored in the hermetic container to the compressing mechanism, bearing and the like components for lubrication. However, the lubricating oil inside the hermetic container is discharged from the compressor with compressed gaseous refrigerant. Normally, an amount of the lubricating oil in the hermetic container is maintained properly because the lubricating oil circulates through a refrigerant circuit and returns again to the compressor.
There is a possibility, however, that the compressor runs short of the amount of stored lubricating oil, and this leads to a deficiency in lubrication since the amount of stored oil varies depending on its operating condition.
There is a disclosure of contrivance to deal with the above problem, which uses a temperature detector to check a level of oil surface inside the hermetic container, and to protect the compressor by detecting a shortage in the amount of the stored lubricating oil. In other words, it is a technique to prevent the compressor from being damaged by carrying out protective operations such as stopping the compressor and retrieving the lubricating oil from the refrigerant circuit when the temperature detector detects a decrease in the oil surface. An example of such technique is disclosed in Japanese Patent Unexamined Publication, No. 2001-12351.
The above technique had a problem, however, that the temperature detector is unable to make a determination as to whether temperatures detected at two measuring points represent a temperature of the lubricating oil or a temperature of the refrigerant gas when there is no difference between these temperatures. In other words, it was unable to determine whether or not amount of the lubricating oil is sufficient.
There is another technique to deal with the above problem, which proposes installation of a temperature detector at a location where a temperature of the refrigerant gas is detectable at all the time. This technique is disclosed, for example, in Japanese Patent Unexamined Publication, No. 2001-32772.
As discussed above, there proposed number of techniques in air conditioners for detecting an oil surface of the lubricating oil in order to control an amount of the lubricating oil inside the compressor. These techniques of detecting oil surface use a method of monitoring the oil surface based upon a difference in temperature of measuring points inside the hermetic container of the compressor.
In order to detect a level of the oil surface inside the hermetic container, however, it is necessary to dispose a plurality of temperature detectors or the like components within the hermetic container, and to deliver signals of the temperature detectors or the like to the outside of the hermetic container. In order to fulfill these requirements, a conventional compressor is provided with a plurality of temperature detectors or the like components mounted securely to the inside of hermetic container, and a plurality of hermetic terminals disposed separately to the hermetic container for connection of the temperature detectors and delivering their signals to the outside. Or, the plurality of temperature detectors may be connected to a single hermetic terminal or the like. Because of the above reason, the compressor has a problem that its structure is complex and the additional terminals give rise to a failure in the hermetic seal of the hermetic container.
It also has another problem that the oil temperature detectors detect the oil surface erroneously due to a splash of the lubricating oil over the oil temperature detectors even when an actual oil surface remains below them, since they are disposed in an exposed manner within the hermetic container.

SUMMARY OF THE INVENTION

A hermetic compressor of the present invention comprises a hermetic container, an electric motor and a compressing mechanism installed inside the hermetic container, lubricating oil and refrigerant gas enclosed within the hermetic container, a first temperature detector disposed to a predetermined location within the hermetic container, and a second temperature detector disposed to a location adjacent to a surface of the lubricating oil in the hermetic container.
The predetermined location where the first temperature detector is disposed is one of a location near an upper end and another location near a lower end within a space inside the hermetic container, and an amount of the lubricating oil in the hermetic container is determined according to temperatures detected by the first temperature detector and the second temperature detector.
The invention can hence provide the hermetic compressor of a simple structure with capabilities of detecting a level of the oil surface inside the hermetic container accurately, and improving reliability of a refrigeration unit equipped with this compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a refrigerant circuit of a refrigeration unit according to a first embodiment of the present invention;
FIG. 2 is a structural diagram of a hermetic compressor according to the first embodiment of the present invention;
FIG. 3 is an enlarged view of a principal portion of the hermetic compressor according to the first embodiment of the present invention;
FIG. 4 is a structural diagram of a hermetic compressor according to a second embodiment of the present invention; and
FIG. 5 is an enlarged view of a principal portion of the hermetic compressor according to the second embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Description is provided hereinafter of the preferred embodiments of the present invention with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a diagram illustrating a refrigerant circuit of a refrigeration unit according to the first embodiment of the present invention. The refrigeration unit of the present embodiment is provided with refrigerant circuit 10 which constitutes an air conditioner for conditioning room air, as shown in FIG. 1.
Refrigerant circuit 10 is so constructed that a circulating direction of refrigerant is reversible in a manner that operation of it can be switched between a refrigeration cycle and a heat-pump cycle. Refrigerant circuit 10 is provided with compressor 11. A discharging side of compressor 11 is connected to first port 13 a of four-way diverter valve 13 through refrigerant tubing 21. Second port 13 b of four-way diverter valve 13 is connected with one end of outdoor heat exchanger 14 through refrigerant tubing 22. The other end of outdoor heat exchanger 14 is connected with expansion valve 15 through refrigerant tubing 23.
Expansion valve 15 is connected with one end of indoor heat exchanger 18 through refrigerant tubing 24. The other end of indoor heat exchanger 18 is connected with fourth port 13 d of four-way diverter valve 13 through refrigerant tubing 25. Third port 13 c of four-way diverter valve 13 is connected to the inflow side of compressor 11 through refrigerant tubing 26.
Four-way diverter valve 13 is constructed in a switchable manner between one state in which first port 13 a is in continuity with second port 13 b and third port 13 c is in continuity with fourth port 13 d (i.e., the state shown with solid lines in FIG. 1), and another state in which first port 13 a is in continuity with fourth port 13 d and second port 13 b is in continuity with third port 13 c (i.e., the state shown with dotted lines in FIG. 1).
Compressor 11 is formed into a completely hermetic structure. Description is provided hereinafter of the structure of compressor 11. FIG. 2 is a structural diagram of the hermetic compressor according to the first embodiment of this invention.
As shown in FIG. 2, compressor 11 comprises compressing mechanism 31 and electric motor 32 contained in a cylindrically-formed hermetic container 30, and it is formed into a dome-like shape suitable for high pressure. Hermetic container 30 is provided with discharge pipe 34 on its upper end for delivering compressed refrigerant gas, as it corresponds to refrigerant tubing 21 in FIG. 1.
Compression mechanism 31 is comprised of a so-called rolling piston type, and it is fixed to hermetic container 30. Compression mechanism 31 has intake pipe 33 connected to it through accumulator 36 for suctioning the refrigerant gas. This intake pipe 33 corresponds to refrigerant tubing 26 in FIG. 1. In addition, compression mechanism 31 is coupled to electric motor 32 via drive shaft 35, and rotatory driven by electric motor 32.
Drive shaft 35 is provided with a centrifugal pump and a refueling path, though not shown in the figure, and they are disposed in a manner to penetrate through compressing mechanism 31. The centrifugal pump is located at the lower end of drive shaft 35, and it pumps up lubricating oil 38 stored in the bottom of hermetic container 30 by the rotary motion of drive shaft 35. On the other hand, the above-said refueling path is formed internally along an axis of drive shaft 35 so as to supply lubricating oil 38 pumped up by the centrifugal pump to the individual sliding members.
Description is provided next of a structure distinctive of compressor 11. FIG. 3 shows an enlarged view of a principal portion of the first embodiment of this invention.
As shown in FIG. 2 and FIG. 3, compressor 11 comprises first temperature detector 39 a disposed to the upper part inside hermetic container 30 for detecting a temperature of the refrigerant gas. In addition, compressor 11 comprises second temperature detector 39 b disposed near oil surface 37 of lubricating oil 38 for detecting a temperature of lubricating oil 38.
First temperature detector 39 a is disposed to hermetic terminal 12 mounted to the upper part of hermetic container 30 in a location corresponding to the interior of hermetic container 30. This first temperature detector 39 a is mounted directly to hermetic terminal 12. Second temperature detector 39 b is disposed to a lower space of hermetic container 30 in a location corresponding to a lower boundary of the oil surface inside hermetic container 30.
Hermetic terminal 12 comprises discoidal base 42 secured by welding to hermetic container 30 and three electrode pins 43 penetrating base 42. Each of electrode pins 43 is fixed to base 42 with insulator 44 made of glass to maintain insulation from base 42.
One ends of the individual electrode pins 43 are connected with first oil temperature detector 39 a and second oil temperature detector 39 b, and the other ends are connected to signal conductors (not shown). The other ends of the individual electrode pins 43 are thus in continuity with controller 50.
Controller 50 is provided with determiner 51 for determining an amount of the lubricating oil. Determiner 51 determines excess or deficiency in the amount of the lubricating oil based on detection signals of first temperature detector 39 a and second temperature detector 39 b. More specifically, determiner 51 determines that the lubricating oil is deficient when a temperature detected by first temperature detector 39 a matches another temperature detected by second temperature detector 39 b.
In other words, first temperature detector 39 a regularly detects a temperature of the refrigerant gas since it is disposed to the upper part within compressor 11.
On the other hand, second temperature detector 39 b normally detects a temperature of lubricating oil 38 because it is disposed to the location adjacent to the lower boundary of the oil surface. Therefore, second temperature detector 39 b is surrounded by the refrigerant gas and detecting its temperature if the detected temperature of second temperature detector 39 b comes to match the temperature detected by first temperature detector 39 a. Determiner 51 thus determines it as deficiency of the lubricating oil.
In the case of high-pressure dome-like compressor here, temperatures of the lubricating oil and the refrigerant gas are approximately 60 deg-C. and 80 deg-C. respectively during the operation, and there is hence a distinctive difference between them. Although these values vary depending on the operating condition since they are representative of only one mode, there is never an instance that the temperature of the lubricating oil comes into a close approximation to the temperature of the refrigerant gas.
A level of oil surface 37 inside hermetic container 10 varies during the operation because the lubricating oil is discharged from the compressor together with the discharged refrigerant. As a result, the temperature detected by second temperature detector 39 b changes from a low temperature range to a high temperature range across a transition range, according to decrease in the amount of the lubricating oil. It is hence possible to determine any change of oil surface 37 of lubricating oil 38 by comparing the temperature in the transition range or the high temperature range with another temperature detected by first temperature detector 39 a which constantly monitors the temperature in the high temperature range.
According to this embodiment, as described above, the compressor of a simple structure is yet capable of determining a surface of the lubricating oil accurately based on a difference of the temperatures detected by the two temperature detectors.

Second Embodiment

FIG. 4 is a structural diagram of a hermetic compressor according to the second embodiment of the present invention, and FIG. 5 is an enlarged view of a principal portion of the same hermetic compressor. A refrigeration unit has a similar refrigerant circuit as that illustrated in FIG. 1 in the above first embodiment, and details of it will therefore be skipped. Moreover, like reference marks are used to designate like components as those of the first embodiment, and their explanations are also skipped.
As shown in FIG. 4 and FIG. 5, first temperature detector 40 a is disposed to a lower part inside a space in hermetic container 30 of compressor 11 for detecting a temperature of lubricating oil 38. In addition, second temperature detector 40 b is disposed to a location adjacent to oil surface 37 of lubricating oil 38 for detecting a temperature of lubricating oil 38.
First temperature detector 40 a detects the temperature of the lubricating oil at all the time since it is disposed to the lowest location in hermetic container 30. Second temperature detector 40 b is disposed to a lower space of hermetic container 30 in the location corresponding to a lower boundary of the oil surface inside hermetic container 30.
Hermetic terminal 12 comprises discoidal base 42 secured by welding to hermetic container 30 and three electrode pins 43 penetrating base 42. Each of electrode pins 43 is fixed to base 42 with insulator 44 made of glass to maintain insulation from base 42.
One ends of the individual electrode pins 43 are connected with first oil temperature detector 40 a and second oil temperature detector 40 b, and the other ends are connected to signal conductors (not shown). The other ends of the individual electrode pins 43 are thus in continuity with controller 50.
Controller 50 is provided with determiner 51 for determining an amount of the lubricating oil. Determiner 51 determines excess or deficiency in the amount of the lubricating oil based on detection signals of first temperature detector 40 a and second temperature detector 40 b. More specifically, determiner 51 determines that the lubricating oil is deficient when a temperature detected by first temperature detector 40 a does not match another temperature detected by second temperature detector 40 b.
In other words, first temperature detector 40 a always detects a temperature of the lubricating oil since it is disposed to the lowest location within hermetic container 30. On the other hand, second temperature detector 40 b normally detects the temperature of lubricating oil 38 because it is disposed to the location adjacent to the lower boundary of the oil surface.
Therefore, the two temperatures detected by first temperature detector 40 a and second temperature detector 40 b normally match with each other because they both detect temperature of the same lubricating oil. When the lubricating oil decreases below a predetermined level, however, second temperature detector 40 b comes to detect a temperature of the refrigerant gas. As a result, determiner 51 determines that the lubricating oil is deficient when the temperatures detected by first temperature detector 40 a and second temperature detector 40 b become unmatched.
In the case of high-pressure dome-like compressor here, temperatures of the lubricating oil and the refrigerant gas are approximately 60 deg-C. and 80 deg-C. respectively during the operation, and there is hence a distinctive difference between them. Although these values vary depending on the operating condition since they are representative of only one mode, there is never an instance that the temperature of the lubricating oil comes into a close approximation to the temperature of the refrigerant gas.
A level of oil surface 37 inside hermetic container 10 varies during the operation because the lubricating oil is discharged from the compressor together with the discharged refrigerant. As a result, the temperature detected by second temperature detector 40 b changes from a low temperature range to a high temperature range across a transition range, according to decrease in the amount of the lubricating oil. It is hence possible to determine any change of oil surface 37 of lubricating oil 38 by comparing the temperature in the transition range or the high temperature range with another temperature detected by first temperature detector 40 a which constantly monitors the temperature in the low temperature range.
According to this embodiment, as described above, the compressor of a simple structure is yet capable of determining a surface of the lubricating oil accurately based on a difference of the temperatures detected by the two temperature detectors.

Claims

1. A hermetic compressor comprising:

(a) a hermetic container;

(b) an electric motor installed inside of the hermetic container;

(c) a compressing mechanism disposed within the hermetic container and driven by the electric motor;

(d) lubricating oil enclosed inside of the hermetic container for lubricating the compressing mechanism;

(e) refrigerant gas enclosed inside of the hermetic container, and serving as a medium forming a refrigeration cycle;

(f) a first temperature detector disposed to a predetermined location inside the hermetic container; and

(g) a second temperature detector disposed to a location adjacent to an oil surface of the lubricating oil inside of the hermetic container,

wherein the predetermined location is one of a location near an upper end and another location near a lower end within a space inside the hermetic container, and an amount of the lubricating oil in the hermetic container is determined according to temperatures detected by the first temperature detector and the second temperature detector.

2. The hermetic compressor according to claim 1, wherein the second temperature detector is disposed to a location where it is immersed in or exposed above the lubricating oil depending on an operating condition of the hermetic compressor.

3. The hermetic compressor according to claim 1, wherein the amount of the lubricating oil is determined normal when the second temperature detector detects a temperature of the lubricating oil, and the amount is determined deficient when the second temperature detector detects a temperature of the refrigerant gas.

4. The hermetic compressor according to claim 1, wherein the first temperature detector is disposed to a location near the upper end in the hermetic container for detecting a temperature of the refrigerant gas.

5. The hermetic compressor according to claim 4, wherein the amount of the lubricating oil is determined deficient when temperatures detected by the first temperature detector and the second temperature detector match with each other.

6. The hermetic compressor according to claim 1, wherein the first temperature detector is disposed to a location near the lower end in the hermetic container for detecting a temperature of the lubricating oil.

7. The hermetic compressor according to claim 6, wherein the amount of the lubricating oil is determined deficient when temperatures detected by the first temperature detector and the second temperature detector do not match with each other.

8. The hermetic compressor according to claim 1 further comprising a hermetic terminal disposed to the hermetic container, wherein the first temperature detector and the second temperature detector are connected to the hermetic terminal.

9. The hermetic compressor according to claim 8, wherein the hermetic terminal includes three pins, and one end of the first temperature detector and one end of the second temperature detector are connected together to one of the three pins.

10. A refrigeration unit including a hermetic compressor, the hermetic compressor comprising:

(a) a hermetic container;

(b) an electric motor installed inside of the hermetic container;