WO2022031239A1

WO2022031239A1 - A capacitance type liquid level sensor for a compressor

Info

Publication number: WO2022031239A1
Application number: PCT/TH2020/000055
Authority: WO
Inventors: Jakrapong SAENGKHUMSUK; Woraphan RUNGRUANG
Original assignee: Siam Compressor Industry Co., Ltd.
Priority date: 2020-08-05
Filing date: 2020-08-05
Publication date: 2022-02-10

Abstract

The present invention discloses a capacitance type liquid level sensor (40) for a compressor 1 comprising: an airtight terminal (50); and a liquid level detecting part (60) which is attached to the airtight terminal (50). The liquid level detecting part (60) includes a pair wires (62,62) and a wire supporting body (64) which is attached to the airtight terminal (50) and configured to arrange the pair wires (62,62) at specific intervals so as to increase a length of each wire (62).

Description

TITLE OF THE INVENTION

A CAPACITANCE TYPE LIQUID LEVEL SENSOR FOR A COMPRESSOR

FIELD OF INVENTION

The present invention relates to a capacitance type liquid level sensor for a compressor.

BACKGROUND OF THE INVENTION

It is known that an oil sensor includes two parallel plate-shaped electrodes to act as a capacitor that connect to conductive pins and are placed at a desired oil height position inside a compressor shell, as disclosed in Japanese Patent Publication No. JP5838408B2 hereinafter called PTL1.

The capacitance value depends on the factors of these parallel plate-shaped electrodes, namely an area of a plate-shaped electrode and a gap between these electrodes. As such, for the purpose of increasing the capacitance value, it is necessary to increase the area of the plateshaped electrode and to reduce the gap between these electrodes.

In particular, as a space to place the oil sensor in the compressor is limited, it is not easy to increase the area of the plate-shaped electrode. In case that a measured value of the capacitance value is very small, for example a few picofarad (pF), the measured value is affected by an electrical noise and the opportunity that the measured value receives interference by the electrical noise increases.

Therefore, the development of a capacitance type liquid level sensor for a compressor, that reduces interference by the electrical noise and detects an accurate measured value, is required.

CITATION LIST

Patent Literature

PTL 1 : Japanese Patent Publication No. JP58384O8B2

SUMMARY OF THE INVENTION

It is an objective of the present inventions to provide a capacitance type liquid level sensor for a compressor, that has a simple structure as well as that reduces interference by the electrical noise and detects an accurate measured value.

In order to achieve the above objective, an embodiment of the present invention provides a capacitance type liquid level sensor for a compressor comprising: an airtight terminal through which conductive members pass, and the conductive members are insulated and airtightly secured to the airtight terminal; and a liquid level detecting part which is attached to the airtight terminal and detects a liquid level, which includes a pair wires which is electrically connected to the conductive members, and a wire supporting body which is attached to the airtight terminal and configured to arrange the pair wires at specific intervals so as to increase a length of each wire.

According to the embodiment of the present invention, firstly, since the wire supporting body is configured to arrange the pair wires at specific intervals so as to increase a length of each wire, it is possible that the length of each wire is increased and the specific intervals between the pare wires is made smaller.

As such, even if a space to place the capacitance type liquid level sensor in the compressor is limited, it is possible to increase the measured value of the capacitance value. As a result, since a larger measured value of the capacitance value is detected, it is possible to reduce interference by the electrical noise and detect an accurate measured value.

Secondly, the capacitance type liquid level sensor includes the airtight terminal and the liquid level detecting part having the pair wires and the wire supporting body, and thereby the capacitance type liquid level sensor is formed in a simple structure.

Therefore, it is possible for the capacitance type liquid level sensor with a simple structure to reduce interference by the electrical noise and detect an accurate measured value.

BRIEF DESCRIPTION OF DRAWINGS

The principle of the present invention and its advantages will become apparent in the following description taking in consideration with the accompanying drawings in which: FIG.l is an explanation view illustrating a schematic configuration of a compressor 1 including a capacitance type liquid level sensor 40 according to a first embodiment of the present invention;

FIG.2A is an enlarged view of a lower portion of the compressor 1 in FIG.1 ;

FIG.2B is an enlarged view of a lower portion of the compressor 1 in FIG.l when viewed from an oblique direction;

FIG.3A is a schematic view of the capacitance type liquid level sensor 40 according to the first embodiment of the present invention;

FIG.3B is a schematic view of the liquid level detecting part 60 in FIG.3A when viewed from an oblique direction; FIG.4A is a perspective view of the liquid level detecting part 70 of the capacitance type liquid level sensor 40’ according to a second embodiment of the present invention;

FIG.4B is a side view of the liquid level detecting part 70 in FIG.4A;

FIG.5 is a view for explaining the mounting state of the capacitance type liquid level sensor 40 according to a second embodiment, to the compressor;

FIG.6A is an explanation view of a liquid level detecting part 80 of the capacitance type liquid level sensor 40” according to a third embodiment of the present invention;

FIG.6B is the explanation view of the liquid level detecting part 80 in FIG.6A, when viewed from a different direction; and

FIG.7 is an explanation view of a variation of a liquid level detecting part of the capacitance type liquid level sensor 40 according to the first embodiment

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.l to FIG.8.

[First embodiment]

FIG.l is an explanation view illustrating a schematic configuration of a compressor 1 according to a first embodiment. For the purpose of explaining the inside of the compressor 1, FIG.1 shows that a half of a sealed container 10 is removed from the compressor 1.

The compressor 1 is a fluid machine configured to compress and discharge a fluid (e.g., gas refrigerant), and can be a component of a refrigeration cycle apparatus, for example, in a refrigerator, a freezer, an automatic vending machine, an air-conditioning apparatus, a refrigeration unit, and a water heater. The compressor 1 according to the first embodiment is a vertically-mounted shell compressor 1.

As shown in FIG.l, the compressor 1 includes a sealed container 10, a suction pipe 19 mounted penetratingly a top portion of the sealed container 10, a discharge pipe 15 discharging the fluid to the outside, a compression element 30 configured to compress a fluid (low-pressure gas refrigerant), and a motor element 20 configured to drive the compression element 30 are housed in the sealed container 10.

The upper portion of the compression element 30 is fixed and supported by a middle shell 10a. The scroll compression element 30 is the middle shell 10a of the sealed container 10 through shrink fit or other method. A sub-frame 12 is provided below the motor element 20. The sub-frame 12 is fixed to the inner circumferential surface of the sealed container 10. An oil sump 14 is formed on a bottom portion 10b of the sealed container 10. A refrigerating machine oil lubricating sliding parts such as bearings is accumulated in the oil sump 14.

The suction pipe 19 configured to suck a fluid (low-pressure gas refrigerant) into the compression element 30 from outside is connected to a top portion of the sealed container 10. The discharge pipe 15 configured to discharge the fluid (high-pressure gas refrigerant) to the outside of the compressor 1 is connected to a side face of the sealed container 10.

The compression element 30 is housed in the sealed container 10 and configured to be driven by a rotating shaft portion (not shown) of the motor element 20. The compression element 30 includes a fixed scroll (not shown) and an orbiting scroll (not shown). The fixed scroll is fixed to the middle shell 10a at a lower end portion of the fixed scroll. The discharge port configured to discharge a compressed fluid is formed in a central part of the fixed scroll. The orbiting scroll is configured to orbit opposed to the fixed scroll without rotating, by a non-illustrated Oldham mechanism. The orbiting scroll is configured to orbit opposed to the fixed scroll.

The motor element 20 includes an electric motor stator 22 fixed to the inner circumferential surface of the sealed container 10 through shrink fit or other method, an electric motor rotor (not shown) rotatably housed on an inner circumferential side of the electric motor stator 22, and a rotating shaft portion (not shown) fixed to the electric motor rotor through shrink fit or other method. The electric motor stator 22 is connected to a glass terminal (not shown) via lead wires. The electric motor stator 22 is supplied with electric power from outside via the glass terminal and lead wires. The electric motor rotor is configured to rotate as electric power is supplied to the electric motor stator 22 and transmit a driving force to the orbiting scroll through the rotating shaft portion.

A pump element 18 such as a positive displacement pump is installed at a lower end of the rotating shaft portion. The pump element 18 supplies the refrigerating machine oil accumulated in the oil sump 14 to the sliding parts such as the main bearing. The pump element 18 is mounted on the sub-frame 12 and supports the rotating shaft portion in the axial direction on an upper end surface of the pump element 18.

As shown in FIG.l, FIG.2A and FIG.2B, a capacitance type liquid level sensor 40 is arranged in a lower portion of the sealed container 10. The capacitance type liquid level sensor 40 is installed so as to extend inward from an inner wall surface of the sealed container 10 in a horizontal direction as well as not to interfere with the pump element 18.

The capacitance type liquid level sensor 40 detects a level of the liquid (refrigerating machine oil) which is accumulated in the oil sump 14. Namely, based on the measured capacitance value which is detected by the capacitance type liquid level sensor 40, the level corresponding to the measured capacitance value is calculated.

As shown in FIG.3A and FIG.3B, the capacitance type liquid level sensor 40 for a compressor 1 includes an airtight terminal 50 and a liquid level detecting part 60 which is attached to the airtight terminal 50.

In an embodiment, the airtight terminal 50 is a glass terminal, but is not limited thereto. For example, a ceramic airtight terminal may be used as the airtight terminal 50 of the embodiment. The airtight terminal 50 includes a circular cap shaped body 52, and a pair of conductive members 54,54 which are connection pins.

As shown in FIG.3A, the circular cap shaped body 52 is formed in a cap shape so as to open on one side thereof, and is formed to be larger in cross section on an opening side. When tiie circular cap shaped body 52 is installed into the sealed container 10, the opening side with the larger diameter is positioned inside the sealed container 10 for the purpose of preventing the circular cap shaped body 52 from passing through the hole of the side wall of a bottom portion 10b of the sealed container 10.

The periphery of the circular cap shaped body 52 of the glass terminal is fitted in the hole of the flat surface of the side wall of a bottom portion 10b of the sealed container 10. And a welded portion is formed there by resistance welding. Each of the conductive members 54,54 is integrally held in the circular cap shaped body 52 with a glass portion (not shown) interposed therebetween.

That is, the glass portion exists between the conductive members 54,54 and the circular cap shaped body 52. Because the glass portion is made of glass with an insulation property, even if the circular cap shaped body 52 and the conductive members 54,54 are both made of metal, each of the conductive members 54,54 is protected against short circuits. As such, the airtight terminal 50 through which conductive members 54,54 pass, and the conductive members 54,54 are insulated and airtightly secured to the airtight terminal 50.

As shown in FIG.3 A and FIG.3B, the liquid level detecting part 60 includes a pair wires 62,62 which are electrically connected to the conductive members 54,54 and a wire supporting body 64 which is attached to the airtight terminal 50 and configured to arrange the pair wires 62,62 at specific intervals so as to increase a length of each wire 62. The liquid level detecting part 60 is attached to the airtight terminal 50 and detects a liquid level.

In the embodiment, the wire supporting body 64 is made of PBT (Polybutylene terephthalate) and includes a columnar body 64a and a base 64b which is attached to the airtight terminal 50. The columnar body 64a is formed to extend from the base 64b. A pair grooves (not shown) for the pair wires 62,62 are formed on an outer peripheral surface of the columnar body 64a of the wire supporting body 64, so that the pair wires 62,62 are wound around the columnar body 64a and are arranged at specific intervals each other.

In the embodiment, each of the pair wires 62,62 is a conductor wire and made by copper, but is not limited thereto. For example, the wire 62 may be aluminum.

The capacitance value of the liquid level detecting part 60 of the first embodiment is expressed by a following formula:

In the formula, “d” is a distance between the pair wires 62,62. “2a” is a diameter of the wire 62. “1” is a length of the wire 62.

As such, it is possible to increase the capacitance value of the liquid level detecting part 60 of the first embodiment, by increasing the distance (d) between the pair wires 62,62 and/or the length (1) of the wire 62 or by decreasing the diameter (2a) of the wire 62.

According to the first embodiment of the present invention, since the wire supporting body 64 is configured to arrange the pair wires 62,62 at specific intervals so as to increase a length of each wire 62, it is possible that the length of each wire 62 is increased and the specific intervals between the pare wires 62,62 is made smaller.

Even if a space to place the capacitance type liquid level sensor 40 in the compressor 1 is limited, it is possible to increase the measured value of the capacitance value. As a result, since a larger measured value of the capacitance value is detected, it is possible to reduce interference by the electrical noise and detect an accurate measured value.

Furthermore, the capacitance type liquid level sensor 40 includes the airtight terminal 50 and the liquid level detecting part 60 having the pair wires 62,62 and the wire supporting body 64, and thereby the capacitance type liquid level sensor 40 is formed in a simple structure.

Therefore, it is possible for the capacitance type liquid level sensor 40 with a simple structure to reduce interference by the electrical noise and detect an accurate measured value.

As shown in FIG.l, FIG.2A and FIG.2B, in the first embodiment, the capacitance type liquid level sensor 40 is installed so as to extend inward from an inner wall surface of the sealed container 10 in a horizontal direction as well as not to interfere with the pump element 18, but is not limited thereto. For example, the liquid level detecting part 60 may be extended upward from the airtight terminal 50 in the compressor 1. According to this constitution, it is possible to expand the measurement range of the liquid level in the oil sump 14.

[Second embodiment]

A wire supporting body 74 of a liquid level detecting part 70 of a capacitance type liquid level sensor 40’ according to second embodiment will be describe with reference to FIG.4A, FIG.4B and FIG.5. In FIG.4A and FIG.4B, the airtight terminal 50 is omitted because the capacitance type liquid level sensor 40’ according to second embodiment can use the airtight terminal 50. The wire supporting body 74 is made of PBT (Polybutylene terephthalate).

As shown in FIG.4A, FIG.4B and FIG.5, the wire supporting body 74 includes two plates 74a,74a, a support 74b which is provided between the two plates 74a, 74a, and a base 74c. The base 74c is provide on the outside of the two plates 74a,74a and configured to be attached to the airtight terminal 50. Each of the two plates 74a,74a includes multiple pairs of openings 76,76 through which the pair wires 72,72 pass. Moreover, the support 74b supports the two plates 74a,74a so that the pair wires 72,72 are arranged at specific intervals and in parallel with one another as well as travel several times between the two plates 74a,74a.

As shown in FIG.4A, each plate 74a is formed in a disk shape. The multiple pairs of openings 76,76 are arranged along a periphery of the plate 74a so that the pair wires 72,72 are arranged at specific intervals and in parallel with one another. By the pair wires 72,72 travel several times between the two plates 74a,74a, the length of the each wire 72 is increased.

Also, the capacitance type liquid level sensor 40 of the second embodiment is installed so as to extend inward from an inner wall surface of the sealed container 10 in the horizontal direction as well as not to interfere with the pump element 18.

According to the second embodiment, in comparison with tire first embodiment, a contact area between one liquid drop and the surfaces of the wires 72,72 to which the one liquid drop adheres becomes small. As such, even if the liquid drops adhere to the surface of the wire 72, the liquid drops easily drop from the surface of each wire 72.

Moreover, the distance between plurality of the pair wires 72,72 is larger than the distance between the pair wires 72,72, and thereby the liquid drops more easily drop from the surface of each wire 72.

Furthermore, since the pair wires 72,72 are arranged at specific intervals and in parallel with one another as well as travel several times between the two plates 74a,74a, it is possible to increase the measured value of the capacitance value. Therefore, according to the capacitance type liquid level sensor 40’ of the second embodiment, it is possible to further reduce interference by the electrical noise to detect a more accurate measured value.

[Third embodiment]

A wire supporting body 84 of a liquid level detecting part 80 of a capacitance type liquid level sensor 40” according to third embodiment will be describe with reference to FIG.6A and FIG.6B. In FIG.6A and FIG.6B, regarding a base of the wire supporting body 84 for the third embodiment, the base which is configured to be attached to the airtight terminal 50 is omitted. The wire supporting body 84 is made of PBT (Polybutylene terephthalate).

As shown in FIG.6A and FIG.6B, the wire supporting body 84 excluding the base is a substantially U-shaped member and includes two bar-shaped members 84a,84a which extend within the compressor 1, and a base (not shown). Each of two bar-shaped members 84a,84a includes multiple pairs of openings 86,86 through which the pair wires 82,82 pass. Moreover, the two bar-shaped members 84a,84a are formed so that the pair wires 82,82 are arranged at specific intervals and in parallel with one another as well as travel several times between the two bar-shaped members 84a,84a.

Also, the capacitance type liquid level sensor 40 of the third embodiment is installed so as to extend inward from an inner wall surface of the sealed container 10 in the horizontal direction as well as not to interfere with the pump element 18.

According to the third embodiment, the pair wires 82,82 are arranged at specific intervals and in parallel with one another as well as travel several times between the two bar-shaped members 84a, 84a. As such, since the number of times when the pair wires 82,82 travel between the two bar-shaped members 84a,84a is limited due to the restriction on the positions of the installation of the openings 86,86, there is a possibility that the length of the wire 82 of the third embodiment is shorter that the length of the wire 82 of the second embodiment.

However, in comparison with the second embodiment, the liquid drops more easily drop from the surface of each wire 82. Therefore, according to the capacitance type liquid level sensor 40 of the third embodiment, it is possible to detect a more accurate measured value.

[Variation] 0 In the wire supporting body 64 of the first embodiment, the sharp of a member around which the pair wires 62,62 are wound, is formed as a columnar body. As a variation, as shown in FIG.7, the sharp of the member around which the pair wires 62,62 are wound, may be formed as a square column-shape body. Moreover, if the pair wires can be wound around the wire supporting body and be arranged at specific intervals each other, the sharp of the member around which the pair wires 62,62 may be a pentagonal column-shaped body, a hexagonal columnshaped body, etc.

Although specific embodiments of the invention have been disclosed and described as well as illustrated in the companying drawings, it is simply for the purpose of better understanding of the principle of the present invention and it is not as a limitation of the scope and spirit of the teaching of the present invention. Adaption and modification to various structures such as design or material of the invention, mounting mechanism of various parts and elements or embodiments are possible and apparent to a skilled person without departing from the scope of the present invention which is to be determined by the claims.

List of reference:

1 : compressor

10: sealed container

10a: middle shell

10b: bottom portion 12: sub-frame

14: oil sump

15: discharge pipe 18: pump element 19: suction pipe 20: motor element

22: electric motor stator

24: electric motor rotor

30: compression element

40, 40’, 40”: capacitance type liquid level sensor

50: airtight terminal

52: circular cap shaped body

54: conductive member

60: liquid level detecting part

62: wire

64: wire supporting body

70: liquid level detecting part

72: wire

74: wire supporting body 74a: plate

74b: support

74c: base

76: opening

80: liquid level detecting part

82: wire

84: wire supporting body 84a: bar-shaped member 86: opening

Claims

1. A capacitance type liquid level sensor (40;40’ ;40”) for a compressor (1) comprising: an airtight terminal (50) through which conductive members (54,54) pass, and the conductive members (54,54) are insulated and airtightly secured to the airtight terminal (50); and a liquid level detecting part (60;70;80) which is attached to the airtight terminal (50) and detects a liquid level, which includes a pair wires (62,62;72,72;82,82) which is electrically connected to the conductive members (54,54), and a wire supporting body (64;74;84) which is attached to the airtight terminal (50) and configured to arrange the pair wires (62,62;72,72;82,82) at specific intervals so as to increase a length of each wire (62;72;82).

2. The capacitance type liquid level sensor (40;40’;40”) of claim 1, wherein the liquid level detecting part (60;70;80) is extended upward from the airtight terminal (50) in the compressor (1).

3. The capacitance type liquid level sensor (40) of claim 1 , wherein the wire supporting body (64) includes a columnar body, and wherein the pair wires (62,62) are wound around the columnar body and are arranged at specific intervals each other.

4. The capacitance type liquid level sensor (40’) of claim 1, wherein the wire supporting body (74) includes two plates (74a,74a) and a support (74b) which is provided between the two plates (74a,74a), wherein each of the two plates (74a,74a) includes multiple pairs of openings (76,76) through which the pair wires (72,72) pass, and wherein the support (74b) supports the two plates (74a,74a) so that the pair wires (72,72) are arranged at specific intervals and in parallel with one another as well as travel several times between the two plates (74a,74a).

5. The capacitance type liquid level sensor (40”) of claim 1, wherein the wire supporting body (84) includes two bar-shaped members (84a,84a) which extend within the compressor (1), wherein each of two bar-shaped members (84a,84a) includes multiple pairs of openings (86,86) through which the pair wires (82,82) pass, and wherein the two bar-shaped members (84a,84a) are formed so that the pair wires (82,82) are arranged at specific intervals and in parallel with one another as well as travel several times between the two bar-shaped members (84a, 84a).