Monitoring device and monitoring procedure

Abstract

A monitoring device for monitoring lubricating oil (20) in a compressor (10), the monitoring device comprising: a first capacitance detector (100) arranged in the compressor (10) and completely immersed in the lubricating oil (20) in the compressor (10) and adapted to detect a first capacitance value C 11 to detect; a calculation unit for calculating a relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) according to the first capacitance value C detected by the first capacitance detector (100) 11 ; and a determination unit for monitoring according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil (20) in the compressor (10) is abnormal, the monitoring device further comprising: a second capacity detector (200) arranged vertically in the compressor (10), where the calculation unit based on the calculated relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) and a second capacity value C 21 detected by the second capacitance detector (200) arranged vertically in the compressor (10), calculates a depth H to which the second capacitance detector (200) is immersed in the lubricating oil (20) in the compressor (10), wherein: the relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) is calculated according to formula (1): ε r = C 11 C 10 where C 10is a capacitance value detected by the first capacitance detector (100) in vacuum, characterized in that the depth H to which the second capacitance detector (200) is immersed in the lubricating oil (20) is calculated according to formula (2): H = L ∗ ( C 21 − C 20 ) ( ε r − 1 ) ∗ C 20 where C 20 is a capacitance value detected by the second capacitance detector (200) in air, and L is the length of the second capacitance detector (200) in a vertical direction.

Description

Technical field

[0001] The present invention relates to the technical field of detection, and more particularly relates to a monitoring device and a monitoring method for monitoring lubricating oil in a compressor. background

[0002] To reduce compressor wear and extend the compressor's service life, some compressors incorporate a sufficient amount of lubricating oil into the compressor to ensure adequate lubrication for the various components. However, if the quality of the lubricating oil in a compressor deteriorates, this could in reality lead to a loss of the lubricating function of the lubricating oil in the compressor.

[0003] Indications of the quality of lubricating oil in a compressor include the degree of dilution of the lubricating oil, foreign matter introduced into the lubricating oil, oxidation or carbonization of the lubricating oil, etc.

[0004] If the dilution degree of lubricating oil in a compressor is too high, i.e., if too much refrigerant has been entrained into the lubricating oil in the compressor, this will result in the concentration of the lubricating oil in the compressor becoming too low. This causes a reduction in the viscosity of the lubricating oil. Once the viscosity of the lubricating oil is reduced, serious wear of the compressor bearings will result. Therefore, once the dilution degree of the lubricating oil exceeds a warning value, the compressor must be stopped immediately or the dilution degree of the lubricating oil must be reduced. In the prior art, part of the refrigerant that has been entrained into the lubricating oil can generally be evaporated out by heating the lubricating oil to thereby reduce the dilution degree of the lubricating oil.

[0005] If foreign matter, such as iron fragments that have fallen off the compressor bearings, is introduced into the lubricating oil, this increases wear on the compressor components. Once iron fragments have entered the lubricating oil, the compressor must be stopped immediately, and the iron fragments must be removed from the lubricating oil.

[0006] When lubricating oil oxidizes or carbonizes, the lubricating oil loses its lubricating function, which in turn leads to rapid wear of the compressor and a shortening of the compressor's service life. Once lubricating oil oxidizes or carbonizes, the compressor must be stopped immediately and the lubricating oil replaced with new lubricating oil.

[0007] In summary, to ensure that a compressor can operate safely, the quality of lubricating oil in the compressor must be continuously monitored in real time.

[0008] Regarding the continuous real-time monitoring of lubricating oil quality in a compressor, the prior art generally monitors lubricating oil quality by measuring the viscosity, density, or impurities of the lubricating oil. However, a prior art monitoring device for monitoring lubricating oil quality by measuring viscosity, density, or impurities is very expensive, costing between 400,000 and 1.6 million CNY. Furthermore, the installation of such a prior art monitoring device is very complex, and large amounts of data must be processed, resulting in slow detection speeds. Currently, such a monitoring device is only suitable for laboratory testing and cannot yet be used industrially.

[0009] JP H02 - 291 484 A deals with monitoring devices for monitoring lubricating oil in a compressor. Brief description of the invention

[0010] The object of the present invention is to solve at least one aspect of the above-mentioned problems and disadvantages of the prior art.

[0011] An object of the present invention is to provide a monitoring device and a monitoring method for the continuous real-time monitoring of lubricating oil in a compressor, which can conveniently and precisely monitor the quality or the quality and level of the lubricating oil in the compressor.

[0012] A monitoring device for monitoring lubricating oil in a compressor is provided. The monitoring device includes: a first capacitance detector disposed in the compressor and completely immersed in the lubricating oil in the compressor; a calculation unit for calculating a relative dielectric constant ε r of the lubricating oil in the compressor according to a first capacitance value C detected by the first capacitance detector 11 ; and a determination unit for monitoring according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil in the compressor is abnormal.

[0013] The monitoring device further includes: a second capacitance detector arranged vertically in the compressor. The calculation unit calculates, based on the calculated relative dielectric constant ε rof lubricating oil in the compressor and a second capacity value C 21 detected by the second capacitance detector arranged vertically in the compressor, a depth H to which the second capacitance detector is immersed in the lubricating oil in the compressor; and the determination unit monitors, based on the calculated depth H, whether the level of the lubricating oil in the compressor is lower than a safe level value.

[0014] The relative dielectric constant ε r of the lubricating oil in the compressor is calculated according to formula (1): εr=C11C10 where C 10 is a capacitance value detected by the first capacitance detector in vacuum.

[0015] The depth H to which the second capacitance detector is immersed in the lubricating oil is calculated according to formula (2): H=L∗(C21−C20)(εr−1)∗C20 where C20 is a capacitance value detected by the second capacitance detector in air, and L is the length of the second capacitance detector in a vertical direction.

[0016] According to a further embodiment of the present invention, the determining unit monitors whether the calculated relative dielectric constant ε r is greater than a previously determined dielectric constant value, and if the calculated relative dielectric constant ε ris greater than the predetermined dielectric constant value, the determination unit determines that the quality of the lubricating oil in the compressor is abnormal; and / or the determination unit monitors whether the calculated depth H is less than a predetermined depth value, and if the calculated depth H is less than the predetermined depth value, the determination unit determines that the level of lubricating oil in the compressor is lower than a safe level value.

[0017] According to another embodiment of the present invention, the first capacitance detector is a parallel plate capacitance detector or a cylindrical capacitance detector, and the second capacitance detector is a parallel plate capacitance detector or a cylindrical capacitance detector.

[0018] According to another embodiment of the present invention, the first capacitance detector is installed substantially horizontally on a bottom wall of an oil tank in the compressor.

[0019] According to another embodiment of the present invention, the second capacitance detector is installed vertically on a side wall of the oil tank in the compressor.

[0020] According to another practical embodiment of the present invention, a lower end of the second capacitance detector is in contact with a bottom wall of the oil tank in the compressor.

[0021] According to another embodiment of the present invention, the first capacitance detector and the second capacitance detector are two physically separate components or are integrated to form a one-piece component.

[0022] A monitoring method for monitoring lubricating oil in a compressor is provided. The monitoring method includes the following steps: Calculating a relative dielectric constant ε r of lubricating oil in a compressor according to a first capacity value C 11 , which was detected by a first capacitance detector completely immersed in the compressor, and monitoring, according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil in the compressor is abnormal.

[0023] The above-mentioned method further includes: Calculating, on the basis of a second capacitance value C 21 , which was detected by a second capacitance detector arranged vertically in the compressor, and the calculated relative dielectric constant ε rof lubricating oil in the compressor, a depth H to which the second capacitance detector is immersed in the lubricating oil in the compressor.

[0024] In the above-mentioned method, the relative dielectric constant ε r of the lubricating oil in the compressor is calculated according to formula (1): εr=C11C10 where C 10 is a capacitance value detected by the first capacitance detector in vacuum.

[0025] In the above-mentioned method, the depth H to which the second capacitance detector is immersed in the lubricating oil is calculated according to formula (2): H=L∗(C21−C20)(εr−1)∗C20 where C 20 is a capacitance value detected by the second capacitance detector in air, and L is the length of the second capacitance detector in a vertical direction.

[0026] According to a further embodiment of the present invention, in the above-mentioned method, when the calculated relative dielectric constant ε r is greater than a predetermined dielectric constant value, the quality of lubricating oil in the compressor is determined to be abnormal; and / or if the calculated depth H is less than a predetermined depth value, the level of lubricating oil in the compressor is determined to be lower than a safe level.

[0027] According to a further embodiment of the present invention, the above-mentioned method further includes: switching off the compressor when the calculated relative dielectric constant ε r is greater than a previously specified dielectric constant value or if the calculated depth H is less than a previously specified depth value.

[0028] According to a further embodiment of the present invention, in the above-mentioned method, the first capacitance detector is a parallel plate capacitance detector or a cylindrical capacitance detector, and the second capacitance detector is a parallel plate capacitance detector or a cylindrical capacitance detector.

[0029] According to another embodiment of the present invention, in the above-mentioned method, the first capacitance detector is installed substantially horizontally on a bottom wall of an oil tank in the compressor.

[0030] According to another embodiment of the present invention, in the above-mentioned method, the second capacitance detector is installed vertically on a side wall of the oil tank in the compressor.

[0031] According to another embodiment of the present invention, in the above-mentioned method, a lower end of the second capacitance detector is in contact with a bottom wall of the oil tank in the compressor.

[0032] According to a further embodiment of the present invention, in the above-mentioned method, the first capacitance detector and the second capacitance detector are two physically separate components or are integrated to form a one-piece component.

[0033] In the monitoring device and method in the various practical embodiments of the present invention set forth above, the capacitance detectors enable convenient and precise monitoring of the quality of lubricating oil in a compressor. Furthermore, continuous real-time detection of the lubricating oil level can be performed to realize simultaneous detection of the quality and level of lubricating oil. The monitoring device reduces monitoring costs and increases monitoring accuracy.

[0034] The following description of the present invention with reference to the accompanying drawings will clarify further objects and advantages of the present invention and can provide a thorough understanding of the present invention. Description of the enclosed drawings Fig.1 shows a schematic sectional view of a compressor according to an embodiment of the present invention, showing a first capacitance detector and a second capacitance detector. Fig. 2 shows a 3D view of the second capacitance detector in Fig. 1. Fig. 3 shows a curve diagram of a detected level of lubricating oil in a container, which is determined by the first capacitance detector and the second capacitance detector in Fig. 1 was detected, and an actual level of lubricating oil in the container. Fig. 4 shows a graph of a relationship between a dilution of the lubricating oil and a relative dielectric constant of the lubricating oil. Detailed description

[0035] The technical solution of the present invention is explained in more detail below according to embodiments with reference to the accompanying drawings. Throughout the description, identical or similar reference numerals denote identical or similar components. The following explanation of embodiments of the present invention with reference to the accompanying drawings serves to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0036] Furthermore, in the following detailed description, for ease of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. However, it will be apparent that one or more embodiments could be implemented without these specific details. In other instances, well-known structures and devices are embodied as illustrations to simplify the accompanying drawings.

[0037] As stated above, to ensure that a compressor can operate safely, the quality of lubricating oil in the compressor must be continuously monitored in real time. According to an overall technical concept of the present invention, a monitoring device for monitoring lubricating oil in a compressor is provided. The monitoring device includes: a first capacitance detector disposed in the compressor and completely immersed in lubricating oil in the compressor; a calculation unit for calculating a relative dielectric constant ε r of the lubricating oil in the compressor according to a first capacitance value C detected by the first capacitance detector 11 ; and a determination unit for monitoring according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil in the compressor is abnormal.

[0038] In actual applications, if the lubricating oil level in the compressor is too low, the operational reliability of the compressor will be compromised. If the lubricating oil level in the compressor is too low, it will be impossible to supply a sufficient amount of lubricating oil to various components of the compressor, and as a result, the various components of the compressor will not be sufficiently lubricated. Consequently, the wear of the various components of the compressor will be accelerated, thereby shortening the service life of the compressor. Therefore, once the lubricating oil level in the compressor is lower than a warning level, it is necessary to immediately shut down the compressor and add a sufficient amount of lubricating oil to the compressor.

[0039] Regarding continuous real-time monitoring of the lubricating oil level in the compressor, the prior art generally monitors the lubricating oil level in a compressor using a pressure differential detector or a magnetic floating ball. However, since the pressure in the compressor can reach up to 45 bar, this will damage the pressure differential detector or the magnetic floating ball. Furthermore, because the operating conditions inside the compressor are very complex (e.g., foaming, temperature instability, significant pressure fluctuations, and significant density changes), it becomes impossible for the pressure differential detector or the magnetic floating ball to accurately detect the lubricating oil level in the compressor.

[0040] In view of the above, the monitoring device mentioned above further includes: a second capacitance detector arranged vertically in the compressor. The calculation unit calculates, based on the calculated relative dielectric constant ε r of the lubricating oil in the compressor and a second capacity value C 21 detected by the second capacitance detector arranged vertically in the compressor, a depth H to which the second capacitance detector is immersed in the lubricating oil in the compressor; the determining unit monitors, based on the calculated depth H, whether the level of the lubricating oil in the compressor is lower than a safe level value.

[0041] According to a technical concept of the present invention, a monitoring method for monitoring lubricating oil in a compressor is provided. The monitoring method includes the following steps: calculating a relative dielectric constant ε r of the lubricating oil in the compressor according to a first capacity value C 11 , which was detected by a first capacitance detector completely immersed in the compressor, and monitoring, according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil in the compressor is abnormal.

[0042] According to another technical concept of the present invention, the above-mentioned monitoring method further includes the steps of: calculating, on the basis of a second capacitance value C 21, which was detected by a second capacitance detector arranged vertically in the compressor, and the calculated relative dielectric constant ε r of the lubricating oil in the compressor, a depth H to which the second capacitance detector is immersed in the lubricating oil in the compressor, and monitoring, based on the calculated depth H, whether the level of the lubricating oil in the compressor is lower than a safe level value.

[0043] Fig. 1 shows a schematic sectional view of a compressor according to an embodiment of the present invention, wherein a first capacitance detector 100 and a second capacitance detector 200 are shown.

[0044] In one embodiment of the present invention, a monitoring device for monitoring lubricating oil 20 in a compressor 10 is disclosed. As Fig.1, the monitoring device in the illustrated embodiment mainly includes a first capacitance detector 100, a second capacitance detector 200, a calculation unit (not shown), and a determination unit (not shown).

[0045] How Fig. 1, in one embodiment of the present invention, the first capacitance detector 100 is arranged in the compressor 10 and is completely immersed in the lubricating oil 20 in the compressor 10. Thus, the calculation unit of the monitoring device can calculate a relative dielectric constant ε r of the lubricating oil 20 in the compressor 10 according to a first capacitance value C detected by the first capacitance detector 100 11 Calculate the relative dielectric constant ε r of the lubricating oil 20 in the compressor 10 can be calculated according to formula (1): εr=C11C10 where C 10is a capacitance value detected by the first capacitance detector 100 in vacuum.

[0046] In the embodiments of the present invention, the determination unit of the monitoring device monitors according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil 20 in the compressor 10 is abnormal.

[0047] The following is a brief description of the principles of monitoring according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil 20 in the compressor 10 is abnormal.

[0048] Generally, indicators of the quality of lubricating oil in a compressor include dilution of the lubricating oil, foreign matter entering the lubricating oil, oxidation or carbonization of the lubricating oil, etc.

[0049] If the dilution of the lubricating oil in a compressor is too high, i.e., if too much refrigerant is entrained into the lubricating oil in the compressor, the concentration of the lubricating oil in the compressor becomes too low. This causes a reduction in the viscosity of the lubricating oil; once the viscosity of the lubricating oil is reduced, it leads to severe wear of the compressor bearings.

[0050] The relative dielectric constant of coolant is much greater than the relative dielectric constant of pure lubricating oil. Therefore, if an excessive amount of coolant is introduced into the lubricating oil, the relative dielectric constant of the lubricating oil (or a mixture of lubricating oil and coolant) will be significantly increased, and as a result, the above-mentioned and continuously detected relative dielectric constant ε rof the lubricating oil is greater than a previously set dielectric constant value (or a dielectric constant warning value). As soon as the above-mentioned and continuously detected relative dielectric constant ε r of the lubricating oil is greater than the previously set dielectric constant value, the monitoring device will issue an alarm and immediately shut down the compressor or reduce the dilution of the lubricating oil. For example, part of the refrigerant entrained in the lubricating oil can be evaporated by heating the lubricating oil to reduce the dilution of the lubricating oil, thereby reducing the relative dielectric constant ε r of the lubricating oil is reduced to a value below the warning value.

[0051] If foreign matter is introduced into the lubricating oil, for example, if iron fragments that have fallen off the compressor bearings are introduced into the lubricating oil, this increases the wear of the compressor components. Since the relative dielectric constant of iron fragments is much greater than the relative dielectric constant of pure lubricating oil, the relative dielectric constant of the lubricating oil increases significantly once iron fragments have entered the lubricating oil. As a result, the above-mentioned and continuously detected relative dielectric constant ε r of the lubricating oil is greater than a previously set dielectric constant value (or a dielectric constant warning value). As soon as the above-mentioned and continuously detected relative dielectric constant ε rIf the lubricating oil concentration exceeds the warning value, the monitoring device will trigger an alarm and immediately shut down the compressor. Once the compressor is shut down, the iron fragments must be removed from the lubricating oil.

[0052] When lubricating oil is oxidized or carbonized, it loses its lubricating function, leading to rapid wear of the compressor. Once lubricating oil is oxidized or carbonized, its relative dielectric constant ε decreases. r steeply, and as a result, the above-mentioned and continuously detected relative dielectric constant ε r of the lubricating oil is greater than a previously set dielectric constant value (or a dielectric constant warning value). As soon as the above-mentioned and continuously detected relative dielectric constant ε rIf the lubricating oil level exceeds the warning value, the monitoring device will trigger an alarm and immediately shut down the compressor. Once the compressor shuts down, the lubricating oil must be replaced with new lubricating oil.

[0053] How Fig. 1, the first capacitance detector 100 in the illustrated embodiment may be a parallel plate capacitance detector having a pair of parallel electrode plates facing each other.

[0054] Table 1 below shows a capacitance value that was detected when the Fig. 1 was immersed in a certain pure fatty oil (the temperature of the fatty oil was 18°C), and a relative dielectric constant of the fatty oil was calculated based on the detected capacitance value. Table 1 Nr. 1 2 3 4 5 6 7 8 9 10 Average value Detected capacitance value 11,714 11,708 11,721 11,712 11,754 11,712 11,734 11,75 11,772 11,763 11,734 Calculated relative dielectric constant 3,1498 3,1729 3,1576 3,2017 3,1842 3,1628 3,15515 3,159 3,162 3,193 3,1708

[0055] From Table 1 above, it is clearly seen that the average value of the relative permittivity of the pure fatty oil detected by the first parallel-plate capacitance detector 100 provided in the present invention is 3.1708. The actual relative permittivity of the pure fatty oil is 3.20. As can be seen, the detection result of the above-mentioned first capacitance detector 100 is substantially accurate, and the first capacitance detector 100 can be used to detect the relative permittivity of lubricating oil in the compressor.

[0056] Fig. 2 shows a schematic 3D view of the second capacitance detector 200 in Fig. 1.

[0057] As in the Fig. 1 and Fig.2, in the illustrated embodiment, both the first capacitance detector 100 and the second capacitance detector 200 are parallel-plate capacitance detectors. However, it should be noted that the present invention is not limited to the illustrated embodiment; the first capacitance detector 100 and the second capacitance detector 200 could also be any other type of capacitance detector, for example, cylindrical capacitance detectors.

[0058] As in the Fig. 1 and Fig. As shown in Figure 2, the second capacitance detector 200 in the illustrated embodiment has a pair of parallel electrode plates 210 and 220 facing each other. The length of the second capacitance detector 200 is L, the width of the second capacitance detector 200 is W, and the distance between the pair of electrode plates 210 and 220 is d.

[0059] As in the Fig. 1 and Fig.2, the second capacitance detector 200 in the illustrated embodiment is arranged vertically in the compressor 10, and the depth to which the second capacitance detector 200 is immersed in the lubricating oil 20 in the compressor 10 is H, as shown in Fig. 1 shown.

[0060] Thus, the calculation unit of the monitoring device can, based on the calculated relative dielectric constant ε r of the lubricating oil 20 in the compressor 10 and a second capacity value C 21 detected by the second capacitance detector 200, calculate the depth H to which the second capacitance detector 200 is immersed in the lubricating oil 20 in the compressor 10.

[0061] The depth H to which the second capacitance detector 200 is immersed in the lubricating oil 20 is calculated according to formula (2): H=L∗(C21∗C20)(εr−1)∗C20 where C 20is a capacitance value detected by the second capacitance detector 200 in air, and L is the length of the second capacitance detector 200 in a vertical direction.

[0062] In the embodiments of the present invention, the determination unit of the monitoring device monitors whether the level of the lubricating oil 20 in the compressor 10 is lower than a safe level value based on the calculated depth H.

[0063] Fig. 3 is a graph showing a detected level of a specific fatty oil in a container obtained using the first capacitance detector 100 and the second capacitance detector 200 in Fig. 1 was detected and shows a real level of fatty oil in the container.

[0064] As in Fig.3, the x-axis indicates capacitance values detected by the second capacitance detector 200. The capacitance values detected by the second capacitance detector 200 increase as the level of fatty oil in the container increases.

[0065] As in Fig. 3, the y-axis indicates detected levels of the fatty oil in the container, which were calculated based on the relative dielectric constants of the fatty oil detected by the first capacitance detector 100 and capacitance values detected by the second capacitance detector 200.

[0066] As from Fig. 3, the difference between the detected level of the fatty oil in the container, which is determined using the first capacitance detector 100 and the second capacitance detector 200 in Fig.1 and the actual level is very small, which indicates that the detection of the level of the fatty oil in the container using the first capacitance detector 100 and the second capacitance detector 200 in Fig. 1 is precise and reliable, so that its use for detecting the level of the lubricating oil 20 in the compressor 10 is possible without restriction.

[0067] In one embodiment of the present invention, as in Fig. 1, the first capacitance detector 100 is installed substantially horizontally on a bottom wall of an oil tank in the compressor 10. Thus, it can be ensured that the first capacitance detector 100 is always completely immersed in the lubricating oil 20 in the compressor 10.

[0068] In one embodiment of the present invention, as described in Fig.1, the second capacity detector 200 is installed vertically on a side wall of the oil tank in the compressor 10. Thus, the second capacity detector 200 can be conveniently installed vertically in the compressor 10.

[0069] In one embodiment of the present invention, as in Fig.1, a lower end face of the second capacitance detector 200 is in contact with a bottom wall of the oil tank in the compressor 10. Thus, the detected level H is equal to the level of the lubricating oil 20 in the compressor 10. However, the present invention is not limited to the illustrated embodiment. The lower end face of the second capacitance detector 200 may be located above the bottom wall of the oil tank in the compressor 10 and need not be in contact with the bottom wall of the oil tank in the compressor 10. In this case, the sum of the detected level H and the gap distance between the lower end face of the second capacitance detector 200 and the bottom wall of the oil tank in the compressor 10 is equal to the level of the lubricating oil 20 in the compressor 10.

[0070] In the Fig.In the embodiment shown in Figure 1, the first capacitance detector 100 and the second capacitance detector 200 are two independent components that are physically separated. However, the present invention is not limited to the illustrated embodiment. The first capacitance detector 100 and the second capacitance detector 200 may also be integrated into a single component.

[0071] In another embodiment of the present invention, a monitoring method for monitoring lubricating oil in a compressor is disclosed. The monitoring method includes the following steps: Calculating a relative dielectric constant ε r of lubricating oil 20 in a compressor 10 according to a first capacity value C 11 , which was detected by a first capacitance detector 100, and monitoring according to the calculated relative dielectric constant ε rwhether the quality of the lubricating oil 20 in the compressor 10 is abnormal.

[0072] In one embodiment of the present invention, the monitoring method further includes: Calculate, based on the calculated relative dielectric constant ε r of the lubricating oil 20 in the compressor 10 and a second capacity value C 21 detected by the second capacitance detector 200 arranged vertically in the compressor 10, a depth H to which the second capacitance detector 200 is immersed in the lubricating oil 20 in the compressor 10.

[0073] In another embodiment of the present invention, the above-mentioned monitoring method may further include the following step: immediate shutdown of the compressor 10 if the calculated relative dielectric constant ε ris greater than a previously specified dielectric constant value, or if the calculated depth H is less than a previously specified depth value.

[0074] As stated above, an important factor related to the quality of the lubricating oil in the compressor is the dilution of the lubricating oil. If the dilution of the lubricating oil in the compressor is too high, i.e., an excessive amount of refrigerant has been entrained into the lubricating oil in the compressor, the concentration of the lubricating oil in the compressor will consequently become too low. This causes a reduction in the viscosity of the lubricating oil. Once the viscosity of the lubricating oil is reduced, it leads to serious wear of the compressor bearings. Therefore, once the dilution of the lubricating oil exceeds a warning value, it is necessary to immediately shut down the compressor or reduce the dilution of the lubricating oil.

[0075] Therefore, it is necessary to continuously monitor the dilution of the lubricating oil in real time. Based on numerous tests, the inventors of the present application have discovered that a certain functional relationship exists between the dilution of the lubricating oil and the relative dielectric constant of the lubricating oil. Thus, the dilution of the lubricating oil can be monitored by monitoring the relative dielectric constant of the lubricating oil.

[0076] Fig. Figure 4 shows a graph of the relationship between the dilution of lubricating oil and the relative dielectric constant of lubricating oil.

[0077] As in Fig.As shown in Figure 4, the present inventors have discovered, based on numerous tests, a relationship between the relative dielectric constant of lubricating oil and the dilution of lubricating oil under various operating conditions. The relationship between them can be expressed as the following functional relationship (x represents the dilution of the lubricating oil, and y represents the relative dielectric constant of the lubricating oil): y=0.0003x2+0.0416x+2.8374 where x is in the range from 0% to 100%.

[0078] As can be seen from the Fig.As can be seen from the relationship curve diagram shown in Figure 4, as the dilution x of lubricating oil increases, the relative dielectric constant value y of the lubricating oil also increases accordingly. Thus, a warning value for the relative dielectric constant of the lubricating oil can be calculated according to a known warning value for the dilution of the lubricating oil (the maximum allowable value during normal operation) and the functional relationship (3). Once the relative dielectric constant of the lubricating oil is higher than the calculated warning value, it is necessary to immediately shut down the compressor or heat the lubricating oil to reduce the dilution of the lubricating oil.

[0079] However, lubricating oil dilution is only one of the parameters for assessing lubricating oil quality. During a real-world application, the quality of the lubricating oil in a compressor can also be monitored with reference to other parameters (such as viscosity, density, or impurities) of the lubricating oil, thereby determining a warning value for the relative dielectric constant. Thus, the relative dielectric constant of the lubricating oil can be measured, and the quality of the lubricating oil can be determined based on the relative dielectric constant and the warning value.

[0080] Those skilled in the art will appreciate that the embodiments described above are all demonstrative. Furthermore, those skilled in the art could make improvements thereto. The structures described in the various embodiments can be freely combined, provided there are no conflicts in structures or principles.

[0081] Although the present invention has been explained with reference to the accompanying drawings, the embodiments disclosed in the accompanying drawings are intended to demonstrate preferred embodiments of the present invention and should not be construed as limiting the present invention.

[0082] Although some embodiments of the overall inventive concept discussed herein have been presented and explained, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the overall inventive concept. The scope of the present invention is defined by the claims and their equivalents.

[0083] It should be noted that the word "includes" does not exclude other elements or steps, and the words "a" do not exclude plural meanings. Furthermore, no reference signs in the claims should be construed as limiting the scope of the present invention.

Claims

[1] A monitoring device for monitoring lubricating oil (20) in a compressor (10), the monitoring device comprising: a first capacitance detector (100) arranged in the compressor (10) and completely immersed in the lubricating oil (20) in the compressor (10) and adapted to detect a first capacitance value C 11 to detect; a calculation unit for calculating a relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) according to the first capacitance value C detected by the first capacitance detector (100) 11 ; and a determination unit for monitoring according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil (20) in the compressor (10) is abnormal, the monitoring device further comprising: a second capacity detector (200) arranged vertically in the compressor (10), where the calculation unit based on the calculated relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) and a second capacity value C 21 detected by the second capacitance detector (200) arranged vertically in the compressor (10), calculates a depth H to which the second capacitance detector (200) is immersed in the lubricating oil (20) in the compressor (10), wherein: the relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) is calculated according to formula (1): εr=C11C10 where C 10 is a capacitance value detected by the first capacitance detector (100) in vacuum, characterized bythat the depth H to which the second capacitance detector (200) is immersed in the lubricating oil (20) is calculated according to formula (2): H=L∗(C21−C20)(εr−1)∗C20 where C 20 is a capacitance value detected by the second capacitance detector (200) in air, and L is the length of the second capacitance detector (200) in a vertical direction. [2] Monitoring device according to claim 1, wherein: the determination unit monitors whether the calculated relative dielectric constant ε r is greater than a predetermined dielectric constant value, and determines that the quality of the lubricating oil (20) in the compressor (10) is abnormal if the calculated relative dielectric constant ε r is greater than the previously determined dielectric constant value; and / or the determination unit monitors whether the calculated depth H is less than a predetermined depth value, and determines that the level of the lubricating oil (20) in the compressor (10) is lower than a safe level value if the calculated depth H is less than the predetermined depth value. [3] Monitoring device according to claim 1, wherein: the first capacitance detector (100) is a parallel plate capacitance detector or a cylindrical capacitance detector; the second capacitance detector (200) is a parallel plate capacitance detector or a cylindrical capacitance detector. [4] Monitoring device according to claim 1, wherein: the first capacitance detector (100) is installed substantially horizontally on a bottom wall of an oil tank in the compressor (10). [5] Monitoring device according to claim 1, wherein: the second capacity detector (200) is installed vertically on a side wall of an oil tank in the compressor (10). [6] Monitoring device according to claim 5, wherein: a lower end of the second capacitance detector (200) is in contact with a bottom wall of the oil tank in the compressor (10). [7] Monitoring device according to claim 1, wherein: the first capacitance detector (100) and the second capacitance detector (200) are two physically separate components or are integrated to form a one-piece component. [8] A monitoring method suitable for monitoring lubricating oil (20) in a compressor (20) comprising the following steps: Calculating a relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) according to a first capacity value C 11, which was detected by a first capacitance detector (100) which is completely immersed in the compressor (10), and monitoring according to the calculated relative dielectric constant ε r whether the quality of the lubricating oil (20) in the compressor (10) is abnormal, the monitoring method further comprising: Calculate, based on a second capacitance value C 21 , which was detected by a second capacitance detector (200) arranged vertically in the compressor (10), and the calculated relative dielectric constant ε r of the lubricating oil (20) in the compressor (10), a depth H to which the second capacitance detector (200) is immersed in the lubricating oil (20) in the compressor (10), wherein: the relative dielectric constant ε r of the lubricating oil (20) in the compressor (10) is calculated according to formula (1): εr=C11C10 where C 10is a capacitance value detected by the first capacitance detector (100) in vacuum, characterized by that the depth H to which the second capacitance detector (200) is immersed in the lubricating oil (20) is calculated according to formula (2): H=L∗(C21−C20)(εr−1)∗C20 where C 20 is a capacitance value detected by the second capacitance detector (200) in air, and L is the length of the second capacitance detector (200) in a vertical direction. [9] Monitoring method according to claim 8, wherein: if the calculated relative dielectric constant ε r is greater than a predetermined dielectric constant value, the quality of the lubricating oil (20) in the compressor (10) is determined to be abnormal; and / or if the calculated depth H is less than a previously determined depth value, the level of the lubricating oil (20) in the compressor (10) is determined to be lower than a safe level. [10] The monitoring method of claim 8, further comprising: Switching off the compressor (10) when the calculated relative dielectric constant ε r is greater than a previously specified dielectric constant value or if the calculated depth H is less than a previously specified depth value. [11] Monitoring method according to claim 8, wherein: the first capacitance detector (100) is a parallel plate capacitance detector or a cylindrical capacitance detector; the second capacitance detector (200) is a parallel plate capacitance detector or a cylindrical capacitance detector. [12] A monitoring method according to claim 8, wherein: the first capacitance detector (100) is installed substantially horizontally on a bottom wall of an oil tank in the compressor (10). [13] Monitoring method according to claim 8, wherein: the second capacity detector (200) is installed vertically on a side wall of an oil tank in the compressor (10). [14] A monitoring method according to claim 13, wherein: a lower end of the second capacitance detector (200) is in contact with a bottom wall of the oil tank in the compressor (10). [15] Monitoring method according to claim 8, wherein: the first capacitance detector (100) and the second capacitance detector (200) are two physically separate components or are integrated to form a one-piece component.

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