Patent Description:
In a refrigeration system, components (such as bearings) of compressor need to be lubricated by oil. In a substantially oil-free compressor, the refrigeration system itself is not provided with an oil separator, and the system delivers a liquid refrigerant in a condenser to a bearing chamber or bearing lubrication pipeline of the compressor. Due to the characteristics of lubricating oil, it will not accumulate in the condenser, but will accumulate at bottom of an evaporator and bottom of an inner shell of the compressor. In order to improve the reliability of the bearings in the compressor, this oil-rich refrigerant (also called gas-liquid two-phase refrigerant) needs to be delivered to the bearing chamber or bearing lubrication pipeline of the compressor. In this type of system, there are certain requirements for the amount and pressure of the returned refrigerant to ensure that enough oil can reach positions of the bearing chamber or bearing lubrication pipeline of the compressor where lubrication is desired.

<CIT> discloses a pre-start bearing lubrication system employing an accumulator. Just before shutdown, or at least prior to a significant pressure equalization in a refrigeration system, an accumulator containing oil is isolated from the rest of the refrigeration system in such a way that oil is at a pressure that is higher than the pressure of the rest of the system. The oil in the accumulator is maintained in a state of higher pressure while the refrigeration system is shutdown with the aid of a spring-loaded piston. Preliminary to start up of the refrigeration system, the pressurized oil is placed in fluid communication with structure requiring lubrication.

An object of at least the preferred embodiments of the present invention is to solve or at least alleviate the problems existing in the prior art.

According to a first aspect, a refrigeration system is provided, which includes: a compressor, a condenser, a throttling device, and an evaporator, all of which are connected in sequence to form a cooling circuit, in which the refrigeration system further includes an oil recovery system which includes:.

Optionally, the oil-containing position in the refrigeration system is in an oil-collecting cavity inside the compressor or in the evaporator.

A first one-way valve that only allows a fluid to flow from the oil-containing position to the first port is provided on the first pipeline or on an end cover at an end of the operation chamber, and a second one-way valve that only allows the fluid to flow from the second port to the bearing chamber or the bearing lubrication pipeline of the compressor is provided on the second pipeline or the end cover.

Optionally, the main piston is configured to be driven by an electric actuator.

Optionally, the main piston is connected to a first side of a control piston through a connecting rod, there is a first control chamber at the first side of the control piston and a second control chamber at a second side of the control piston; the first control chamber and the second control chamber are alternatively connected to a first pressure fluid source and a second pressure fluid source, and there is a sufficient pressure difference between the first pressure fluid source and the second pressure fluid source, thereby driving the control piston to reciprocate together with the main piston to perform the extraction stroke and the discharge stroke.

Optionally, the first control chamber is located between a back side of the main piston and the first side of the control piston, and the control piston has a larger area of action than the main piston.

Optionally, the first pressure fluid source is from the evaporator, and the second pressure fluid source is from the condenser.

Optionally, the evaporator is connected to the first control chamber through a first valve and is connected to the second control chamber through a second valve, and the condenser is connected to the first control chamber through a third valve and is connected to the second control chamber through a fourth valve; or.

Optionally, the refrigeration system further includes:.

Optionally, the oil recovery system further includes an additional operation chamber, and the additional operation chamber includes a first port communicating with the oil-containing position in the refrigeration system through a third pipeline, and a second port communicating with the bearing chamber or the bearing lubrication pipeline of the compressor through a fourth pipeline; and
an additional main piston in the additional operation chamber, in which the additional main piston is connected to the second side of the control piston through a connecting rod, the second control chamber is located between a back side of the additional main piston and the second side of the control piston, and the control piston has a larger area of action than the additional main piston; when the main piston is performing the extraction stroke, the additional main piston performs the discharge stroke to deliver the oil-containing refrigerant from the additional operation chamber to the bearing chamber or the bearing lubrication pipeline of the compressor, and when the main piston is performing the discharge stroke, the additional main piston performs the extraction stroke to extract the oil-containing refrigerant in the oil-containing position in the refrigeration system to the additional operation chamber.

According to another aspect, an oil recovery method for a refrigeration system is also provided, which includes:.

The device and method according to the embodiments of the present invention can provide refrigerant with sufficient oil content to the bearing chamber or the bearing lubrication pipeline of the compressor.

With reference to the accompanying drawings, the content of the present invention will become easier to understand. It can be easily understood by those skilled in the art that these drawings are only for illustrative purpose, and are not intended to limit the scope of protection of the present invention as set out in the appended claims. In addition, similar numbers in the drawings are used to denote similar components, in which:.

First, referring to <FIG>, the structure of a refrigeration system will be introduced. The refrigeration system includes: a compressor <NUM>, a condenser <NUM>, a throttling device <NUM>, and an evaporator <NUM>, all of which are connected in sequence to form a cooling circuit. The compressor <NUM> includes a compressor inlet <NUM>, a compressor outlet <NUM> and a bearing chamber or bearing lubrication pipeline <NUM> of the compressor. The compressor outlet <NUM> is connected to the condenser <NUM> through a pipeline, and the condenser <NUM> is connected to the throttling device <NUM> through a pipeline. The throttling device <NUM> is, for example, an expansion valve, and the throttling device <NUM> is connected to the evaporator <NUM>. Finally, the evaporator <NUM> is connected to the compressor inlet <NUM> to form the cooling circuit.

In the refrigeration system, the compressor <NUM> may be an oil-free or substantially oil-free compressor, and the compressor <NUM> itself does not include an oil circuit. Therefore, the refrigeration system is also provided with an oil recovery system. The oil recovery system includes: an operation chamber <NUM>, which includes a first port <NUM> and a second port <NUM>, in which the first port <NUM> communicates with an oil-containing position in the refrigeration system through a first pipeline <NUM>, and the second port <NUM> communicates with the bearing chamber or bearing lubrication pipeline <NUM> of the compressor <NUM> through a second pipeline <NUM>. In the illustrated embodiment, the operation chamber <NUM> is defined by a cylinder <NUM> and an end cover <NUM> at one end of the cylinder <NUM>, and the end cover <NUM> is provided with a first port <NUM> and a second port <NUM>. A main piston <NUM> is arranged in the operation chamber <NUM>, and the main piston <NUM> reciprocates in the operation chamber to perform an extraction stroke and a discharge stroke. In the extraction stroke, an oil-containing refrigerant in the oil-containing position in the refrigeration system is extracted to the operation chamber <NUM>. In the discharge stroke, the oil-containing refrigerant in the operation chamber <NUM> is delivered to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor, thereby delivering the refrigerant with a certain oil concentration and pressure to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor for lubrication, anti-corrosion protection and cooling. It should be understood that as the main piston <NUM> reciprocates, the above-mentioned extraction stroke and discharge stroke are repeated at a certain cycle. In the illustrated embodiment, the first port <NUM> of the operation chamber <NUM> is connected to a port <NUM> of the evaporator <NUM> through the first pipeline <NUM>. The port <NUM> may be an additional port of the evaporator <NUM>, and is not an inlet or outlet of the evaporator <NUM> which is connected to the throttling device <NUM> or the compressor inlet <NUM>. In some embodiments, the port <NUM> of the evaporator <NUM> may be located at bottom of the evaporator <NUM> so as to recover the oil-rich refrigerant (also called gas-liquid two-phase refrigerant) at the bottom of the evaporator to the compressor <NUM>. The so-called extraction stroke refers to a stroke in which the main piston <NUM> moves toward the left to extract the refrigerant in the evaporator <NUM> into the operation chamber <NUM>, and the so-called discharge stroke refers to a stroke in which the main piston <NUM> moves toward the right to discharge the refrigerant in the operation chamber <NUM> to the bearing chamber or bearing lubrication pipeline of the compressor.

The oil-containing position refers to a position in the refrigeration system where there is a refrigerant with a certain oil concentration. Although in the illustrated embodiment, the interior of the evaporator <NUM> is used as a specific example of the oil-containing position, it should be understood that there are more options for the oil-containing position in the refrigeration system, such as at an oil-collecting cavity inside the compressor <NUM>, at an economizer (if exists) of the refrigeration system or other evaporators, etc., as long as there is a refrigerant with a certain oil concentration at that position.

The first pipeline <NUM> or the first port <NUM> is provided with a first one-way valve <NUM> that only allows fluid to flow from the oil-containing position (that is, the interior of the evaporator <NUM>) to the first port <NUM> of the operation chamber <NUM>, and the second pipeline <NUM> or the second port <NUM> is provided with a second one-way valve <NUM> that only allows fluid to flow from the second port <NUM> of the operation chamber <NUM> to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor <NUM>, so that a reverse flow of the refrigerant fluid can be avoided. In an example useful for understanding the invention, valves that can be opened and closed, such as solenoid valves, may be provided on the first pipeline <NUM> and the second pipeline <NUM>, in which the valve on the first pipeline is opened and the valve on the second pipeline is closed during the extraction stroke, whereas the valve on the second pipeline is opened and the valve on the first pipeline is closed during the discharge stroke. In the embodiment of <FIG>, the main piston <NUM> is connected to an electric actuator <NUM> through the connecting rod <NUM>, and is therefore driven by the electric actuator <NUM> to perform the extraction stroke and the discharge stroke. The electric actuator <NUM> may be, for example, a linear motor or the like.

Now with continued reference to <FIG>, some modifications of the refrigeration system will be introduced. In the structure of <FIG>, instead of the electric actuator <NUM>, two streams of fluid with a pressure difference are used to drive the main piston <NUM>. Specifically, the main piston <NUM> is connected to a first side of a control piston <NUM> through the connecting rod <NUM>. The first side of the control piston <NUM> has a first control chamber <NUM>, and a second side of the control piston <NUM> has a second control chamber <NUM>. The main piston <NUM>, the connecting rod <NUM> and the control piston <NUM> form an entirety, which is referred to as a piston assembly <NUM>. The first control chamber <NUM> and the second control chamber <NUM> are alternatively connected to a first pressure fluid source and a second pressure fluid source. The first pressure fluid source and the second pressure fluid source have a sufficient pressure difference, thereby driving the control piston <NUM> and the main piston <NUM> (i.e., the piston assembly <NUM>) to reciprocate together so as to perform the extraction stroke and the discharge stroke. More specifically, for example, in the extraction stroke, the first pressure fluid source with a larger pressure is communicated to the first control chamber <NUM>, and the second pressure fluid source is communicated to the second control chamber <NUM>, so that the control piston <NUM> drives the main piston <NUM> to move toward the left together to extract the oil-containing refrigerant from the evaporator <NUM> to the operation chamber <NUM>. In the discharge stroke, the first pressure fluid source with a larger pressure is communicated to the second control chamber <NUM>, and the second pressure fluid source is communicated to the first control chamber <NUM>, so that the control piston <NUM> drives the main piston <NUM> to move toward the right together to discharge the oil-containing refrigerant from the operation chamber <NUM> to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor. In the illustrated embodiment, the operation chamber <NUM>, the first control chamber <NUM> and the second control chamber <NUM> are defined by the same cylinder <NUM>, which includes a portion with a smaller cross section at an end close to the operation chamber <NUM> and a portion with a larger cross section at an end close to the second control chamber. The end of the cylinder <NUM> close to the operation chamber <NUM> is covered by a first cylinder head <NUM>, on which the first port <NUM> and the second port <NUM> are provided, and the end of the cylinder <NUM> close to the second control chamber is covered by a second cylinder head <NUM>. The first control chamber <NUM> is located between a back side of the main piston <NUM> and the first side of the control piston <NUM>, and the control piston <NUM> has a larger area of action (action area of fluid pressure) than the main piston <NUM>. In the extraction stroke and the discharge stroke, the main piston <NUM> is always located in the portion of the cylinder with the smaller cross section, and the control piston <NUM> is always located in the portion of the cylinder with the larger cross section. In an alternative embodiment, the operation chamber <NUM>, the first control chamber <NUM> and the second control chamber <NUM> may be separated and defined by different cylinders, and the first control chamber <NUM> may also not be communicated to the back side of the main piston <NUM>. The first pressure fluid source and the second pressure fluid source may be selected from any position in the refrigeration system, as long as the first pressure fluid source and the second pressure fluid source have a sufficient pressure difference. Alternatively, the first pressure fluid source and the second pressure fluid source may also be external fluid sources independent from the refrigeration system itself. In the illustrated embodiment, the first pressure fluid source is from the evaporator <NUM>, and the second pressure fluid source is from the condenser <NUM>. Specifically, an additional port <NUM> of the condenser <NUM> is communicated to a port <NUM> of the second control chamber <NUM> through a first pipeline <NUM> of the condenser, and is communicated to a port <NUM> of the first control chamber <NUM> through a second pipeline <NUM> of the condenser. The first pipeline <NUM> of the condenser and the second pipeline <NUM> of the condenser are respectively provided with a first control valve <NUM> and a second control valve <NUM>. On the other hand, an additional port <NUM> of the evaporator <NUM> is communicated to the port <NUM> of the first control chamber <NUM> through a first pipeline <NUM> of the evaporator, and is communicated to the port <NUM> of the second control chamber <NUM> through a second pipeline <NUM> of the evaporator. The first pipeline <NUM> of the evaporator and the second pipeline <NUM> of the evaporator are respectively provided with a third control valve <NUM> and a fourth control valve <NUM>. The first control valve <NUM>, the second control valve <NUM>, the third control valve <NUM>, and the fourth control valve <NUM> communicate with a controller. The controller is configured to open the second control valve <NUM> and the fourth control valve <NUM> and close the first control valve <NUM> and the third control valve <NUM> during the extraction stroke, thereby introducing the fluid in the condenser <NUM> into the first control chamber <NUM> and introducing the fluid in the evaporator <NUM> into the second control chamber <NUM>, which therefore drives the piston assembly <NUM> composed of the main piston <NUM>, the connecting rod <NUM> and the control piston <NUM> to move toward the left. The controller is also configured to open the first control valve <NUM> and the third control valve <NUM> and close the second control valve <NUM> and the fourth control valve <NUM> during the discharge stroke, thereby introducing the fluid in the condenser <NUM> into the second control chamber <NUM> and introducing the fluid in the evaporator <NUM> into the first control chamber <NUM>, which therefore drives the piston assembly <NUM> to move toward the right. The above process is repeated again and again.

With continued reference to <FIG>, this embodiment differs from the embodiment shown in <FIG> in that two three-way valves <NUM> and <NUM> are used to replace the four control valves in <FIG>. Specifically, the evaporator <NUM> is connected to the first control chamber <NUM> and the second control chamber <NUM> respectively through a first three-way valve <NUM>, and the condenser <NUM> is connected to the first control chamber <NUM> and the second control chamber <NUM> respectively through a second three-way valve <NUM>. The first three-way valve <NUM> and the second three-way valve <NUM> communicate with the controller. In the extraction stroke, the first three-way valve <NUM> is adjusted to communicate the evaporator <NUM> with the second control chamber <NUM>, and the second three-way valve <NUM> is adjusted to communicate the condenser <NUM> with the first control chamber <NUM>. In the discharge stroke, the first three-way valve <NUM> is adjusted to communicate the evaporator <NUM> with the first control chamber <NUM>, and the second three-way valve <NUM> is adjusted to communicate the condenser <NUM> with the second control chamber <NUM>.

With continued reference to <FIG>, this embodiment differs from the embodiment shown in <FIG> in that a four-way valve <NUM> is used to replace the four control valves in <FIG>. Specifically, the evaporator <NUM>, the condenser <NUM>, the first control chamber <NUM> and the second control chamber <NUM> are connected by the four-way valve <NUM>. In the extraction stroke, the four-way valve <NUM> is adjusted to communicate the evaporator <NUM> with the second control chamber <NUM> and communicate the condenser <NUM> with the first control chamber <NUM>. In the discharge stroke, the four-way valve <NUM> is adjusted to communicate the evaporator <NUM> with the first control chamber <NUM> and communicate the condenser <NUM> with the second control chamber <NUM>.

In some embodiments, the refrigeration system further includes: a sensor, which is configured to sense the position of the control piston <NUM> or the main piston <NUM>; and a controller communicating with the sensor, in which the controller is configured to operate at least one valve (e.g., the control valves <NUM>, <NUM>, <NUM> and <NUM> in the embodiment of <FIG>, or the three-way valves <NUM> and <NUM> in the embodiment of <FIG>, or the four-way valve <NUM> in the embodiment of <FIG>) based on the position of the control piston <NUM> or the main piston <NUM> provided by the sensor so that the first control chamber and the second control chamber are alternatively connected to the first pressure fluid source and the second pressure fluid source, thereby performing the extraction stroke and the discharge stroke. Various types of proximity sensors or contact sensors may be used as the sensor; for example, optical sensors, magnetic sensors and the like may be used. The sensor may be, for example, mounted on the cylinder wall, on the end cover and/or on the piston assembly <NUM>.

With continued reference to <FIG>, another embodiment of the refrigeration system will be introduced. In the embodiment shown in <FIG>, the oil recovery system further includes an additional operation chamber <NUM>. The additional operation chamber <NUM> includes a third port <NUM> that communicates with the oil-containing position (taking the evaporator <NUM> as an example) in the refrigeration system through a third pipeline <NUM>, and a fourth port <NUM> that communicates with the bearing chamber or bearing lubrication pipeline <NUM> of the compressor through a fourth pipeline <NUM>. Similarly, a third one-way valve <NUM> is provided on the third pipeline <NUM> or the third port <NUM>, and third one-way valve <NUM> only allows for a flow of fluid from the evaporator <NUM> to the additional operation chamber <NUM>. A fourth one-way valve <NUM> is provided on the fourth pipeline <NUM> or the fourth port <NUM>, and the fourth one-way valve <NUM> only allows for a flow of fluid from the additional operation chamber <NUM> to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor. The additional operation chamber <NUM> has an additional main piston <NUM>, which is connected to the second side of the control piston <NUM> through a connecting rod <NUM>, and the second control chamber <NUM> is located between the back side of the additional main piston <NUM> and the second side of the control piston <NUM>. In the illustrated embodiment, the cylinder <NUM> defines portions with a smaller cross section at both ends and a portion with a larger cross section in the middle. The cylinder <NUM> is covered by the first cylinder head <NUM> and the second cylinder head <NUM> at both ends, and the second cylinder head <NUM> includes a first port <NUM> and a second port <NUM>. In the extraction stroke and the discharge stroke, the main piston <NUM> and the additional main piston <NUM> move in the portions with the smaller cross section at both ends of the cylinder, and the control piston <NUM> moves in the portion with the larger cross section in the middle. The control piston <NUM> has a larger area of action (i.e., cross-sectional area) than the main piston <NUM> and the additional main piston <NUM>. In the illustrated embodiment, the main piston <NUM> has substantially the same area of action as the additional main piston <NUM>. With this arrangement, when the main piston <NUM> is performing the extraction stroke, the additional main piston <NUM> performs the discharge stroke to deliver the oil-containing refrigerant from the additional operation chamber <NUM> to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor; and when the main piston <NUM> is performing the discharge stroke, the additional main piston <NUM> performs the extraction stroke to extract the oil-containing refrigerant in the oil-containing position in the refrigeration system to the additional operation chamber <NUM>. Therefore, unlike the structures of <FIG> in which the oil-containing refrigerant is delivered to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor only during the discharge stroke, in the embodiment shown in <FIG>, the oil-containing refrigerant will be continuously delivered to the bearing chamber or bearing lubrication pipeline <NUM> of the compressor.

Claim 1:
A refrigeration system, comprising: a compressor (<NUM>), a condenser (<NUM>), a throttling device (<NUM>), and an evaporator (<NUM>), all of which are connected in sequence to form a cooling circuit, wherein the refrigeration system further comprises an oil recovery system comprising:
an operation chamber (<NUM>), which comprises a first port communicating with an oil-containing position in the refrigeration system through a first pipeline (<NUM>), and a second port communicating with a bearing chamber or a bearing lubrication pipeline (<NUM>) of the compressor through a second pipeline (<NUM>); and
a main piston (<NUM>) in the operation chamber (<NUM>), the main piston reciprocating in the operation chamber to perform an extraction stroke and a discharge stroke; wherein in the extraction stroke, an oil-containing refrigerant in the oil-containing position in the refrigeration system is extracted to the operation chamber; and in the discharge stroke, the oil-containing refrigerant in the operation chamber is delivered to the bearing chamber or the bearing lubrication pipeline (<NUM>) of the compressor;
characterised in that a first one-way valve (<NUM>) that only allows a fluid to flow from the oil-containing position to the first port (<NUM>) is provided on the first pipeline (<NUM>) or on an end cover (<NUM>) at an end of the operation chamber (<NUM>), and a second one-way valve (<NUM>) that only allows the fluid to flow from the second port (<NUM>) to the bearing chamber or the bearing lubrication pipeline (<NUM>) of the compressor is provided on the second pipeline (<NUM>) or the end cover.