Oil return structure of compressor and centrifugal machine and air conditioner comprising same

Abstract

The application discloses a kind of oil return structure of compressor and centrifugal machine, air conditioner comprising the oil return structure.Compressor has box, and box is provided with oil return port and air inlet hole, and the inside of box is communicated with oil tank through oil return port;Air inlet hole introduces medium into box to improve the pressure inside box.By setting oil return port and air inlet hole on the box, medium is introduced into the box by air inlet hole to increase the pressure inside the box, and the lubricating oil accumulated at the bottom of the compressor box is pressed out of the oil return port by the effect of pressurization, and smoothly drained back into the oil tank, improving the oil return efficiency of the compressor, preventing the compressor from oil shortage wear due to poor oil return.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature regulation, in particular to a compressor oil return structure, a centrifugal machine comprising the same and an air conditioner. BACKGROUND

[0002] In a centrifugal machine set, many rotating parts need to be lubricated and cooled by lubricating oil to ensure normal operation. The lubricating oil circulates in the oil circuit system of the machine set to complete the lubrication of each rotating part. When the lubricating oil flows, it may accumulate in some parts of the oil circuit and cannot participate in the oil circuit circulation. When the accumulated lubricating oil is too much, it will cause insufficient oil circulation in the system and cannot ensure the normal lubrication of all rotating parts. Therefore, an oil return structure needs to be provided at a part where lubricating oil is prone to accumulate to help the accumulated lubricating oil return to the oil circuit circulation system to meet the oil demand.

[0003] For a single-compressor centrifugal machine set, the accumulated lubricating oil can be returned by gravity to meet the normal operation demand of the machine set. However, for a multi-compressor machine set, especially a series heat pump centrifugal machine set, because the oil circuit system is long and there are many oil storage parts, a large amount of lubricating oil accumulates at the bottom of the compressor box. When the oil is returned by gravity or other low-efficiency oil return structure, the oil return may be not smooth or difficult, which cannot ensure sufficient oil circulation in the system and may cause the compressor to be damaged due to dry grinding and seizure of the rotating shaft, directly affecting the normal operation of the machine set. SUMMARY

[0004] The present application provides a compressor oil return structure, a centrifugal machine comprising the same and an air conditioner. The oil return port and the air inlet hole are arranged on the compressor box. The medium is introduced into the box through the air inlet hole to increase the pressure inside the box. The lubricating oil accumulated at the bottom of the compressor box is pressed out of the oil return port by the pressure effect and smoothly flows back into the oil tank, improving the oil return efficiency of the compressor, preventing the compressor from being damaged due to poor oil return, and improving the reliability of the machine set operation.

[0005] To solve the above problems, according to one aspect of the present application, an embodiment of the present application provides a compressor oil return structure. The compressor has a box. The box is provided with an oil return port and an air inlet hole. The inside of the box is communicated with an oil tank through the oil return port. The air inlet hole introduces medium into the box to increase the pressure inside the box.

[0006] In some embodiments, an adjusting device is arranged on the air inlet hole to control the opening degree of the air inlet hole.

[0007] In some embodiments, the oil return structure has a control device and a detection device, the adjusting device and the detection device are connected with the control device respectively, and the control device controls the adjusting device according to the detection result of the detection device.

[0008] In some embodiments, the detection device includes a liquid level detection unit, the liquid level detection unit detects the liquid level height in the tank, and the control device controls the adjusting device according to the liquid level height.

[0009] In some embodiments, the detection device includes a pressure detection unit, the pressure detection unit detects the pressure value in the tank, and the control device controls the adjusting device according to the pressure value.

[0010] In some embodiments, the detection device includes a temperature detection unit, the temperature detection unit detects the oil temperature in the tank, and the control device controls the adjusting device according to the oil temperature.

[0011] In some embodiments, the tank is provided with a heating device, and the control device controls the heating device according to the oil temperature.

[0012] In some embodiments, a separation device is arranged between the oil tank and the oil return port, and the separation device separates the medium entering the oil tank.

[0013] According to another aspect of the present application, embodiments of the present application provide a centrifugal machine, which comprises a compressor and the above-mentioned oil return structure.

[0014] According to another aspect of the present application, embodiments of the present application provide an air conditioner, which comprises the above-mentioned centrifugal machine.

[0015] The present application improves the oil return efficiency of the oil return structure by using the effect of pressurization, and compared with the traditional gravity oil return structure, the present application can overcome the shortcomings of low oil return efficiency and slow oil return speed of the series unit or other long oil path and oil accumulation unit, and realize high-efficiency and stable oil return. By arranging the adjusting device, the adjusting device is used to control the introduced medium, the appropriate amount of medium is introduced in time, the internal pressure range is reasonably adjusted, the abnormal operation of the components caused by the excessive pressure in the tank is prevented, and the system medium shortage caused by the excessive introduction of the medium can also be avoided. By arranging the heating device, the auxiliary heating is started in time, the viscosity of the accumulated lubricating oil is reduced, the flowability of the lubricating oil is enhanced, the lubricating oil is more easily returned, and the oil return efficiency is further improved.

[0016] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, and the content of the specification can be implemented, the following preferred embodiments of the present application are described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1Fig. 1 is a top view of an oil return structure according to an embodiment of the present application.

[0018] wherein:

[0019] 1, tank; 11, oil return port; 12, air inlet hole; 2, shaft; 3, bearing; 4, heating device; 5, liquid level sensor; 6, adjusting device; 7, oil tank; 8, separating device. DETAILED DESCRIPTION

[0020] To further clarify the technical means and effects taken by the present application to achieve the intended purpose, the following describes the specific embodiments, structures, features and effects according to the present application in detail with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0021] In the description of the present application, it should be clear that the terms "vertical", "transverse", "longitudinal", "front", "back", "left", "right", "up", "down", "horizontal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not mean that the device or element referred to must have a particular orientation or position, and therefore cannot be understood as a limitation on the present application.

[0022] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] The present embodiment provides an oil return structure of a compressor, as shown in Figure 1 The compressor has a tank 1, and the tank 1 is provided with an oil return port 11 and an air inlet hole 12. The tank 1 is an irregular part, generally cast, and mainly functions to support and protect the internal shaft 2 and bearing 3 and other parts. The tank 1 is internally machined with an oil passage for lubricating oil to circulate. When the lubricating oil flows through the bearing 3, it can not only provide a certain oil film thickness to suspend the shaft 2 and prevent dry grinding between the shaft 2 and the bearing 3 to avoid shaft damage, but also can take away the heat generated by the rotation of the shaft 2 to reduce the temperature of the shaft 2 and the bearing 3. The bearing 3 is a hollow rotating part, and the inner surface is coated with babbitt alloy to protect the stable rotation of the shaft 2. The oil tank 7 can be an external oil tank outside the compressor. The lubricating oil stored in the oil tank 7 is pumped into the high oil tank of the compressor tank 1 by the oil pump Figure 1The lubricating oil flows to the bearing 3 through the compressor internal oil circuit, lubricates the bearing 3, and finally deposits at the bottom of the casing 1. In order to avoid the continuous deposition of lubricating oil at the bottom of the casing 1 and cause the oil tank 7 to be insufficient, the oil return port 11 is arranged on the casing 1, the oil tank 7 is connected to the oil return port 11 through a pipeline, and the inside of the casing 1 is communicated, so that the lubricating oil deposited at the bottom of the casing 1 can flow back to the oil tank 7 through the pipeline, supplement the oil amount of the oil tank 7, and ensure that the oil tank 7 has sufficient lubricating oil to supply the high-position oil tank of the compressor casing 1.

[0024] Optionally, the oil tank 7 is arranged at a position lower than the position of the oil return port 11, and the height difference between the two positions is used to make the lubricating oil flow back to the oil tank 7 naturally. Further, the oil return port 11 is arranged on the side wall of the casing 1, and the height of the oil return port 11 from the bottom wall of the casing 1 is reasonably arranged according to the need of the internal oil storage amount of the compressor, so as to ensure that the compressor has a certain amount of oil storage. When the liquid level height of the deposited lubricating oil exceeds the height of the oil return port 11, the lubricating oil can flow back naturally under the action of gravity; when the liquid level height of the lubricating oil drops below the height of the oil return port 11, the lubricating oil stops flowing back and maintains the current liquid level height.

[0025] In order to improve the oil return efficiency and overcome the situation of difficult oil return, the air inlet hole 12 is arranged on the casing 1, the air inlet hole 12 is communicated with the inside of the casing 1, and the medium is introduced into the casing 1 through the air inlet hole 12 to increase the pressure inside the casing 1. For example, in a serial heat pump centrifugal unit, the air inlet hole 12 can introduce the high-temperature and high-pressure refrigerant discharged from the exhaust port of the compressor or the adjacent compressor or other suitable compressor into the casing 1 to increase the pressure of the space inside the casing 1. With the increase of the internal pressure of the casing 1, the lubricating oil accumulated at the bottom of the casing 1 is pressed out of the oil return port 11 under the high pressure and flows back to the oil tank 7 through the pipeline.

[0026] By introducing the high-temperature and high-pressure refrigerant discharged from the compressor through the air inlet hole 12, the accumulated lubricating oil can also be heated, which further improves the oil return efficiency. Specifically, the viscosity of the lubricating oil changes with the change of the oil temperature, and the viscosity of the lubricating oil decreases and the flowability increases when the temperature rises. By heating the accumulated lubricating oil with the high-temperature refrigerant, the viscosity of the lubricating oil decreases, which is convenient for flowing out of the oil return port 11. Optionally, as shown in Figure 1 , the air inlet hole 12 is arranged on the side wall opposite to the position of the oil return port 11, and one way of refrigerant gas is introduced. The high-temperature and high-pressure refrigerant gas presses the lubricating oil accumulated at the bottom of the casing 1 from one side of the air inlet hole 12 to the side of the oil return port 11, which further improves the oil return rate. Through the above arrangement, the internal pressure of the casing is increased, the high-efficiency and stable oil return of the oil return structure can be realized, and the reliability of the unit is improved.

[0027] As a specific embodiment, as shown in Figure 1As shown, the regulating device 6 is arranged on the air inlet hole 12, and the opening degree of the air inlet hole 12 is controlled by the regulating device 6. Alternatively, the air inlet hole 12 can be connected with the regulating device 6 through a pipeline, or the regulating device 6 is directly connected with the air inlet hole 12. When the oil accumulated on the bottom of the box 1 is excessive, the regulating device 6 acts, and the medium is introduced into the box 1 from the air inlet hole 12 to pressurize the accumulated oil to discharge it. When the accumulated oil drops to a certain position, the regulating device 6 acts, and the medium stops entering the box 1, and the box 1 is no longer continuously pressurized, and the accumulated oil mainly relies on gravity to return. Alternatively, the regulating device 6 can be an adjusting valve or an electromagnetic valve and the like. In addition to controlling opening and closing, the executing component can also be controlled by opening degree to adjust the flow rate or flow when the medium flows in.

[0028] As a specific embodiment, the oil return structure has a control device and a detection device, and the regulating device and the detection device are connected with the control device, and the control device controls the regulating device according to the detection result of the detection device. For example, in a serial heat pump centrifugal unit, the control device can be an electric control box of the unit, and the detection device can be a temperature sensing bag, a liquid level sensor, a pressure sensor or a multifunctional sensor and the like. The detection component converts the temperature signal, the liquid level signal, the pressure signal and the like into an electric signal, and sends the electric signal to the electric control box. After receiving the electric signal, the electric control box analyzes and judges, and sends an instruction signal to the executing component such as the regulating valve, and controls the executing component to act to control whether the medium is introduced or not.

[0029] Alternatively, the detection device includes a liquid level detection unit, which can detect the liquid level of the oil accumulated on the bottom of the box. For example, Figure 1As shown, the liquid level detecting unit can be a liquid level sensor 5. The liquid level sensor 5 is in communication with the inside of the tank 1, and detects the liquid level of the accumulated lubricating oil at the bottom of the tank 1 in real time, and transmits the liquid level value to the control device. A liquid level threshold H can be preset in the control device. When the liquid level sensor 5 detects that the liquid level of the accumulated lubricating oil is h, and h is greater than or equal to H, the control device sends an opening instruction signal of the regulating device 6, and transmits the signal to the regulating device 6. After receiving the opening signal, the regulating device 6 acts to allow the high-temperature and high-pressure refrigerant to enter the tank 1 through the air inlet hole 12. When the liquid level sensor 5 detects that the liquid level h is less than H, the control device sends a closing instruction signal of the regulating device 6, and transmits the signal to the regulating device 6. After receiving the closing signal, the regulating device 6 acts to stop introducing the refrigerant into the tank 1. The liquid level sensor 5 can be set to monitor the liquid level of the accumulated oil in real time, so that the oil return structure can introduce high-pressure refrigerant through the air inlet hole to pressurize the oil return in time, and prevent the oil tank from running out of oil due to low oil return rate and continuous increase of accumulated oil when relying only on gravity oil return. Alternatively, the liquid level detected by the liquid level detecting unit can be used as the first judging factor for the control device to determine whether the regulating device needs to introduce the medium. In this way, the oil return structure can be ensured to return oil in time, and excessive accumulation of oil can be avoided.

[0030] As a specific embodiment, the detecting device includes a pressure detecting unit, which detects the pressure value in the tank, and the control device controls the regulating device according to the pressure value detected by the pressure detecting unit. For example, Figure 1When the lubricating oil accumulated in the box 1 is excessive, the control device sends an opening signal to the adjusting device 6 according to the detection signal of the liquid level sensor 5, the adjusting device 6 opens the flow path to make the high-temperature and high-pressure refrigerant enter the box 1 through the air inlet hole 12 to increase the air pressure in the internal space of the box 1. The box 1 is provided with shaft 2, bearing 3 and other components, and the increase of the air pressure in the internal space of the box 1 will generate a certain axial force on the shaft 2, which may cause the shaft 2 to deviate or vibrate excessively during movement. At the same time, the excessive pressure in the box 1 will also hinder the normal oil return of the oil return port 11. A pressure detection unit is arranged to detect the pressure in the box 1 in real time and send the detection result to the control device. The pressure threshold P can be preset in the control device. When the pressure detection unit detects that the pressure value p in the box 1 is less than P, the control device controls the adjusting device 6 to keep the flow path open, and the high-temperature and high-pressure refrigerant continues to flow in. When the pressure detection unit detects that the pressure value p in the box 1 is greater than or equal to P, the control device sends an instruction signal to close the adjusting device 6, and the signal is transmitted to the adjusting device 6. After receiving the closing signal, the adjusting device 6 stops introducing the high-temperature and high-pressure refrigerant into the box 1. In this way, the reliable operation of the compressor can be effectively protected, and the eccentric movement or abnormal vibration of the rotating shaft can be prevented, thereby avoiding damage to the parts. Optionally, the preset pressure threshold can be reasonably set according to the evaporation pressure of the refrigerant under different working conditions, for example, the preset pressure threshold is set to be 20-40KPa higher than the evaporation pressure. By setting a reasonable preset pressure threshold, the internal pressure of the box can be ensured to be conducive to the return of the lubricating oil to the oil tank, and the normal operation of other components is not affected. Optionally, the pressure value detected by the pressure detection unit can be used as the first judgment factor for the control device to determine whether the adjusting device needs to be closed. When the pressure value is used as the first judgment factor for stopping the introduction of the medium, the normal operation of the internal components of the compressor can be effectively protected.

[0031] As a specific embodiment, the detection device includes a temperature detection unit that detects the temperature of the oil accumulated in the box, and the control device controls the adjusting device according to the oil temperature. When the compressor is running, the refrigerant will be dissolved in the lubricating oil to a certain extent, and the solubility of the refrigerant in the lubricating oil is related to the temperature of the lubricating oil. When the temperature changes, the solubility also changes. When the temperature rises to a certain range, the refrigerant gradually dissolves in the lubricating oil, i.e. the refrigerant is limitedly dissolved in the lubricating oil; when the oil temperature reaches a certain value, the refrigerant no longer continues to dissolve, at which time the limited dissolution changes to complete dissolution, and the temperature corresponding to the complete dissolution is the complete dissolution temperature. When the solubility of the refrigerant is too large, the viscosity of the lubricating oil is already low enough, and there is no need to continue to inject the refrigerant. If the refrigerant continues to be injected, it will cause waste of the refrigerant and affect the amount of refrigerant required for normal operation of the unit. For example, when the temperature of the lubricating oil is lower than the complete dissolution temperature, the control device controls the adjusting device to keep the flow path open, and the high-temperature and high-pressure refrigerant continues to flow in. When the temperature of the lubricating oil is higher than the complete dissolution temperature, the control device sends an instruction signal to close the adjusting device, and the signal is transmitted to the adjusting device. After receiving the closing signal, the adjusting device stops introducing the high-temperature and high-pressure refrigerant into the box 1. In this way, the reliable operation of the compressor can be effectively protected, and the eccentric movement or abnormal vibration of the rotating shaft can be prevented, thereby avoiding damage to the parts.Figure 1 When the lubricating oil stored in the box 1 is excessive, the control device sends an opening signal to the adjusting device 6 according to the detection signal of the liquid level sensor 5, and the adjusting device 6 opens the flow path to make the high-temperature and high-pressure refrigerant enter the box 1 through the air inlet hole 12 to increase the air pressure in the internal space of the box 1. A temperature detection unit is arranged to detect the temperature of the lubricating oil at the bottom of the box 1 in real time and send the detection result to the control device. A temperature threshold T can be preset in the control device. When the oil temperature t detected by the temperature detection unit is less than T, the control device controls the adjusting device 6 to keep the flow path open, and the high-temperature and high-pressure refrigerant continues to be introduced into the box 1. When the oil temperature t detected by the temperature detection unit is greater than or equal to T, the control device sends an instruction signal to close the adjusting device 6, and the signal is transmitted to the adjusting device 6. After receiving the closing signal, the adjusting device 6 stops introducing the high-temperature and high-pressure refrigerant into the box 1. In this way, the refrigerant can be fully utilized to reduce the viscosity of the stored lubricating oil and enhance its flowability, and the lubricating oil can be returned to the oil tank, and at the same time, more refrigerant is not occupied for oil return. Alternatively, the preset temperature threshold can be reasonably set according to the complete dissolution temperature of the refrigerant, for example, the preset temperature threshold is set to be 5-10℃ lower than the complete dissolution temperature, and the refrigerant is used efficiently. Alternatively, the oil temperature detected by the temperature detection unit can be used as the first judgment factor for the control device to determine whether the adjusting device needs to be closed. When the oil temperature value is used as the first judgment factor for stopping the introduction of the medium, the demand for refrigerant during the normal operation of the unit can be effectively prevented from being affected by the excessive introduction of the refrigerant.

[0032] As a specific embodiment, a heating device is arranged in the box, and the control device controls the heating device according to the oil temperature. The lubricating oil is heated by the heating device to further reduce the viscosity of the lubricating oil and improve its flowability. For example, Figure 1As shown, the heating device 4 is arranged in the box 1. Optionally, the heating device 4 is arranged at the bottom of the box 1. Arranging the heating device at the bottom of the box can directly heat the lubricating oil accumulated at the bottom of the box, so that the oil temperature is raised faster and the heating efficiency is improved. Specifically, a heating temperature threshold T1 can be preset in the control device. When the oil temperature t detected by the temperature detection unit is less than T1, the control device can send a heating instruction signal to the heating device 4. After receiving the instruction signal, the heating device 4 enters the working state and emits heat to heat the oil. When the oil temperature t detected by the temperature detection unit is greater than or equal to T1, the control device sends a stop heating instruction signal to the heating device. After receiving the signal, the heating device stops working and no longer heats the oil. Heating the lubricating oil can help the oil temperature reach the preset temperature threshold T1 earlier, so that the injection of the refrigerant is stopped in time, the amount of the injected refrigerant is reduced, and the influence of the use of the refrigerant on the efficiency of the compressor is reduced. At the same time, when the heating device heats the lubricating oil to a certain temperature, part of the refrigerant dissolved in the lubricating oil can evaporate into the box, so that the pressure in the box is increased and the oil return efficiency is improved. Therefore, the heating device can help reduce the viscosity of the accumulated oil and improve the flowability, and can also evaporate the refrigerant in the accumulated oil to help increase the pressure in the box. Therefore, the heating device can be used alone to improve the oil return effect, that is, the heating device is started alone without introducing a medium to heat the accumulated oil and promote rapid oil return. Optionally, the heating device can be an electric heating component. Using the electric heating component can quickly increase the temperature of the accumulated oil and help smooth oil return. When the electric heating device is used, additional energy consumption is increased, and the overall energy efficiency of the unit is reduced. Therefore, the electric heating device needs to be set according to the actual demand, and can be used as a short-time or auxiliary oil return auxiliary means.

[0033] As a specific embodiment, as shown in Figure 1 As shown, the separation device 8 is arranged between the oil return port 11 of the compressor and the oil tank 7. After the high-temperature and high-pressure refrigerant is introduced into the box 1, part of the refrigerant is dissolved in the accumulated oil. If the accumulated oil directly returns to the oil tank 7 and is used for lubricating the compressor bearing, the low viscosity of the lubricating oil can cause the surface oil film to be too thin or the oil film to be not formed, which affects the lubrication effect and causes operation problems. Therefore, the accumulated oil discharged from the box 1 needs to be separated to separate the refrigerant in the lubricating oil and return the refrigerant to the refrigerant flow path. The separation device 8 can separate the medium introduced into the oil tank 7.

[0034] The application also provides a centrifugal machine comprising the above-mentioned oil return structure. The application of the above-mentioned oil return structure in the centrifugal machine can avoid the problem of insufficient circulating oil amount caused by low oil return efficiency and ensure the reliable operation of the centrifugal machine set. Especially in a long-pipeline centrifugal machine set such as a serial heat pump centrifugal machine set, the oil return structure can return oil in time and effectively.

[0035] The application also provides an air conditioner comprising the centrifugal machine.

[0036] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present application still belongs to the scope of the technical solution of the present application. It is easy for those skilled in the art to understand that the above advantageous technical features can be freely combined and superimposed without conflict.

Claims

1. A structure for returning oil of a compressor, characterized by, The compressor has a box body, an oil return port and an air inlet hole are arranged on the box body, and the inside of the box body communicates with an oil tank through the oil return port; the air inlet hole introduces medium into the box body to increase the pressure inside the box body; An adjusting device is arranged on the air inlet hole, and the adjusting device controls the opening degree of the air inlet hole; The oil return structure has a control device and a detection device, the detection device includes a temperature detection unit, the temperature detection unit detects the oil temperature inside the box body, and the control device controls the adjusting device according to the oil temperature; When the oil temperature is less than a preset temperature threshold, the control device controls the adjusting device to keep the air inlet hole open to heat the oil inside the box body; when the oil temperature is greater than or equal to the preset temperature threshold, the control device controls the adjusting device to close the air inlet hole.

2. The oil return structure according to claim 1, characterized by The adjusting device and the detection device are connected with the control device respectively, and the control device controls the adjusting device according to the detection result of the detection device.

3. The oil return structure according to claim 2, characterized by The detection device includes a liquid level detection unit, the liquid level detection unit detects the liquid level height inside the box body, and the control device controls the adjusting device according to the liquid level height.

4. The oil return structure according to claim 3, characterized by The detection device includes a pressure detection unit, the pressure detection unit detects the pressure value inside the box body, and the control device controls the adjusting device according to the pressure value.

5. The oil return structure according to claim 1, characterized by The box body is provided with a heating device, and the control device controls the heating device according to the oil temperature.

6. The oil return structure according to any one of claims 1 to 5, characterized by A separation device is arranged between the oil tank and the oil return port, and the separation device separates the medium entering the oil tank.

7. A centrifuge comprising a compressor, characterized in that, The centrifugal machine further comprises the oil return structure according to any one of claims 1-6.

8. An air conditioner characterized by comprising: The air conditioner comprises the centrifugal machine according to claim 7.

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