System for Transporting Lubricating Oil in a Compressor

The present invention relates to a compressor lubricating oil transport system that uses configurations applied to the rotating shaft and to the rotor of the electric motor to provide oil transportation for the purpose of lubricating the bearings of said rotating shaft and for purposes of cooling the upper region of the coils of said electric motor.

As is known to those skilled in the art, hermetic compressors (usually reciprocating), provide for the use of lubricating oil to reduce friction and wear between moving components and, in particular, moving components that integrate the functional compression unit of the hermetic compressor, such as, for example, the eccentric shaft, the central rotating shaft, support bearings, among others. Lubricating oil is usually stored in a reservoir in the lower inner portion of the airtight housing.

In this sense, it is mandatory that the lubricating oil, stored in the lower portion of the hermetic compressor housing, be transported to the moving elements that integrate the compression functional units (moving parts) of the hermetic compressor. Thus, it is common to take advantage of the movement of the compressor's own rotating shaft to transport or pump this lubricating oil to the regions where the oil is needed.

As illustrated in, said compressor comprises a housing, said housing being commonly hermetic, and an electric motor formed by a rotorand stator. In addition, a rotating shaftis operated in association with the rotorof the electric motor; the rotorcomprising at least one internal wallthat faces the rotating shaft. It is worth noting that it is common to have an interference assembly between the rotorand the rotating shaftin order to be able to transmit the torque generated by the electric motor for the compression mechanism.

Additionally, a compressor blockis provided in order to partially accommodate the rotating shaft. An oil pumpis coupled to the shaft-rotor set and partially immersed in an oil reservoirdisposed in the lower portion of the housingof the compressor.

For proper operation of the mechanical systems of the compressor, the rotating shaftis provided with radial bearings, such as, for example, the radial bearingsand, arranged in different positions in relation to said rotating shaft. The radial bearingsandmust receive lubrication from the lubricating oil of the oil reservoir.

As can be seen in more detail infor the purpose of understanding the lubrication system commonly used in hermetic compressors, it is possible to divide the rotating shaftinto a lower region, an upper regionand a rotating region. Said lower regionhas the function of housing by interference the oil pumpdisposed in the oil reservoir; said rotating region, bounded by the housing of the shaft in the blockand by the portion interfering with the rotor, contains a duct, an openingand an external helical channelwhich together feed with lubricating oil the radial bearingsandlocated, respectively, at the end of the rotating regionand in the upper regionof the rotating shaft.

It is common in the art that the lubricating oil transport is performed by a lubricating oil pump, which acts in cooperation with the rotating shaft of the compressor that transports the oil with the aid of mechanical drag. In order to allow lubricating oil to enter the rotating shaft, the oil pumpis provided with a holein the lower region and, by centrifugal force, raises that oil until it finds the duct, which further accelerates the fluid. The helical channel, located outside the rotating region, has a mechanical pumping function, by dragging against the housing of the shaft in the compressor block.

A secondary function performed by the lubricating oil is to remove heat from the electromechanical assembly and assist in its transmission to the environment outside the compressor through the hermetic housing. In most compressors, this oil flow is a result of the excess pumping of lubricating oil to the bearings which naturally returns to the bottom of the hermetic housing. However, it is also possible to direct part of the oil flow to specific points of the motor, promoting additional cooling that reduces the temperature of these components and, therefore, increases the life of the compressor as a whole.

For example, the document U.S. Pat. No. 9,217,434, entitled “COMPRESSOR HAVING DRIVE SHAFT WITH FLUID PASSAGES”, published on Oct. 18, 2012, presents a compressor that comprises a rotating shaft that presents several oil transport channels located internally to said shaft. The channels presented in this document make it possible to transport lubricating oil from an oil reservoir located at the bottom of the compressor housing to the top of the electric motor, with this flow being specifically applied to the cooling of the motor coils. It is noted that the same oil flow that runs through these internal channels is applied in the lubrication of bearings that support moving parts of the compressor.

However, it is observed that the use of the oil flow that is carried through the channels internal to the rotating shaft, both for cooling purposes and for lubrication purposes, can cause failures in the oil supply, which would lead to problems in the lubrication of the bearings. In addition, there may be a reduction in the pumping pressure, since the flow of oil in the internal channels is diffuse, being divided along the rotating shaft.

In addition, document KR547434, entitled “A COOLING STRUCTURE OF END-COIL FOR HERMETIC COMPRESSOR”, published on Oct. 24, 2005, describes a compressor equipped with a rotor, an axis and a passage channel, this passage carrying lubricating oil from a pumping element. A concavity element is provided and comprises a series of radial openings that aim to distribute the flow of lubricating oil in the lower part of the stator. The purpose of the lubricating oil flow is to reduce the temperature/heat removal from the coils.

However, the solution proposed in this document does not allow to cool the upper part of the coils, which would continue without an additional oil flow. The durability of electrical insulators would continue to be determined by the hottest point of the coils at the top.

Additionally, the document U.S. Pat. No. 9,617,985, entitled “HERMETIC RECIPROCATING COMPRESSOR”, published on Oct. 31, 2013, describes a compressor that comprises a shaft, said shaft being provided with a helical channel that allows the lubricating oil to rise up to the top of the shaft. Additionally, an orifice is provided in the upper part of the shaft, said orifice being in communication with an eccentric part. The fundamental feature of this document is the fact that the external helical channel communicates directly with the oil pump mounted on the bottom of the shaft with the sole purpose of providing lubricating oil for the hermetic compressor bearings.

However, this document does not describe a system in which the external channels in the shaft cooperate with the channel system in the rotor to ensure an oil flow to the bearings without the amount of oil supplied by the pumping system to the bearings being impaired.

Further, document U.S. Pat. No. 3,560,116, entitled “ENCLOSED MOTOR-COMPRESSOR, PARTICULARLY A SMALL REFRIGERATION MACHINE”, published on Feb. 2, 1971, discloses a channelto provide oil from the chambertoward the upper coil ends. The channelextends longitudinally with a rearward inclination. However, the channelis not a radial channel and is not arranged around the circumferential channel, but in communication with the channelin a longitudinal direction.

In addition, document U.S. Pat. No. 4,400,142, entitled “MOTOR-COMPRESSOR UNIT”, published on Aug. 23, 1983, discloses a rotor with a circumferential channel and one channel in communication with the circumferential channel in a longitudinal direction, but not surrounding the circumferential channel. Though this document appears to comprise a concavity, it does not extend over part of the rotating surface in contact with the internal surface of the rotor of the motor.

Additionally, document U.S. Pat. No. 3,276,677, entitled “LUBRICATION SYSTEM FOR COMPRESSOR SHAFT JOURNALS”, published on Oct. 4, 1966, discloses a rotor with a circumferential channeland one channel in communication with the circumferential channelin a longitudinal direction, but not surrounding the circumferential channel. Though this document appears to comprise a concavity, it does not extend over part of the rotating surface in contact with the internal surface of the rotorof the motor.

An objective of the present invention is to provide a lubricating oil transport system that avoids the problems of the state of the art.

Such objective is achieved by means of system for transporting lubricating oil in a compressor, comprising:

Conveniently, the system according to the present invention consists of the fact that the concavity has a helicoid shape.

Additionally, the system according to the present invention consists of the fact that the circumferential channel has an external diameter smaller than the external diameter of the rotating shaft housing in the compressor block.

In addition, the system according to the present invention consists of the fact that the radial channel outlet is inscribed in a circle with a diameter larger than the outer diameter of the rotating shaft housing in the compressor block.

Furthermore, the system according to the present invention consists of the fact that the concavity has an annular shape and the rotor does not need the circumferential channel, communicating the radial channel directly with said annular-shaped concavity.

Additionally, the system according to the present invention consists of the fact that the rotating shaft does not need the concavity, directly communicating the restricting hole to the circumferential channel.

The present invention also provides a system for transporting lubricating oil in a compressor, comprising:

Conveniently, the system according to the present invention consists of the fact that the radial channel outlet is inscribed in a circle with a diameter larger than the outer diameter of the rotating shaft housing in the compressor block.

Additionally, the system according to the present invention consists of the fact that there is a partial juxtaposition between the entrance of the radial channel and the outer diameter of the circumferential channel.

Thus, the main objective of the present invention is to reveal a lubricating oil transport system in a hermetic compressor that uses configurations applied to the rotating shaft and applied to the rotor of the electric motor.

Furthermore, the present invention also aims to reveal a lubricating oil transport system in a hermetic compressor that allows the provision of oil transport for the purpose of lubricating support bearings and for the purpose of cooling the upper region of the electric motor coils.

Finally, it is the objective of the present invention to provide a lubricating oil transport system in a hermetic compressor that does not present lubricating oil flow failures or lubricating oil pumping pressure drop.

The system may include a rotor configured for asynchronous induction motors, wherein the circumferential and radial oil channels are formed by stacking a plurality of magnetic steel laminations. Each lamination is angularly rotated by a composite angle comprising a skew angle and an interlock angle, enabling continuous radial channels to be formed from stamped cutouts. This arrangement improves manufacturability and oil flow performance.

In accordance with the general objectives of the present invention, a lubricating oil transport system is provided in a hermetic compressor for cooling the upper coils of the electric motor in addition to the normal lubricating oil transport system for the bearings and moving parts, as shown in.

According to, the lubricating oil transport system of the present invention is defined by the fact that the rotating shaftcomprises at least one concavity, said concavityextends over part of the rotating surface, and a restrictor hole, said holecommunicates the concavitywith the internal region of the rotating shaft. The concavityand the restrictor holeare responsible for diverting a portion of lubricating oil, coming from the oil pump, from the internal region of the rotating shaft.

Said concavity, in general, defines a type of recess formed in the rotating surfaceof the rotating shaft, such concavitybeing partially closed by the inner wallof the rotor. Thus, for the lubricating oil be transported, the rotating surfaceinteracts with the inner wallof the rotor, forming a type of pumping mechanism that operates by centrifugal force, depending on the operation of the compressor.

According to, the rotorfurther comprises a circumferential channeland at least one radial channelextending through the inner wallof the rotor. Said circumferential channelcooperates with the radial channel, equally distributing the flow of lubricating oil provided by the concavity, regardless of the angular position of the rotorin relation to the rotating shaftand, consequently, in relation to the concavity. According to, the maximum diameter of the circumferential channelmust be smaller than the minimum outer diameter of the rotating shafthousing in the compressor block, in order to limit the vertical displacement of the rotating shaft-rotorset in relation to the compressor block. On the other hand, the length of the radial channelmust be dimensioned in such a way that its outlet is inscribed in a larger diameter than the same external diameter of the rotating shafthousing in the compressor block, in order to ensure unrestricted flow of oil through the spaceformed between the aluminum ringof the rotorand the compressor block, even under conditions where the vertical clearance between the rotorand the rotating shafthousing in the block compressoris too small.

In a first preferred embodiment, the concavityhas a helicoid shape, extending in a spiral over part of the rotating surface. The recess must open towards the circumferential channel. This circumferential channelalso communicates with at least one radial channel.

The number of concavitiesand restrictor holesdepend on the cooling need of the stator, where the electric motor coils are housed.illustrate several views of the rotating shaft. Likewise, the number of radial channelsin the rotor must allow the free flow of oil into spaceand in a way provide a symmetry of the rotor, in order to leave it balanced, as illustrated in.

In a second possible embodiment, illustrated in, the concavityhas an annular shape, extending around the rotating surface. In this configuration, at least one upward radial channelis provided in the inner wallof the rotorwhich communicates with the concavityof the rotating shaft. In this case, the rotormay or may not have the circumferential channelon its inner wall.illustrates the rotorprovided with only the radial channel. The restrictor holeis responsible for diverting part of the oil pumped by the pumpto the annular concavity, said concavitymakes the distribution of this oil flow until it finds the upward radialchannel, exiting into spaceand finally being thrown against the coils of stator on the top of the electric motor. In addition,illustrates the configuration of the rotorfor carrying out this second embodiment.

In a third alternative embodiment, illustrated in, there is no concavityon the rotating surface, only the restricted holeremaining for communication with the internal part of the rotating shaft. In this embodiment, at least one longitudinal channelis provided on the inner wallof the rotor, said longitudinal channelcommunicating with the circumferential channellocated at a height of the rotorat the same level as the restrictor hole. Said circumferential channel, provided on the inner wall of the rotor, ensures that a specific angular positioning of rotorwith rotating shaftis not necessary in order to align the restrictor holewith the radial channel.illustrates rotorin this third embodiment.

In any constructive situation of the rotor, preferably two or more radial channelsare applied to the inner wall, said channelsdisposed in order to guarantee the symmetry of the rotorand avoid problems of unbalance. These radial channelscan and should follow the rotation angle of the aluminum bars of the rotorcage and being obtained directly from the stamping of the rotorblades.

The previous embodiments can be applied to compressors whose oil pumpis mounted by internal or external interference to the lower regionof the rotating shaft, or even by interference in relation to the internal wallof the rotor, the deviation of oil for cooling the coil being carried out by the restrictor holeprovided on the rotating shaft.

A fourth embodiment is illustrated in. This embodiment is only used in hermetic compressors in which the oil pumpis mounted by interference in relation to the internal wallof the rotor. In this embodiment, the rotating shaftdoes not need the restrictor hole, which can remain with the original oil pumping system. In this way, the oil diversion for cooling the motor coils takes place in a section of the inner wallbetween the upper part of the oil pumpand the lower regionof the rotating shaft, through a circumferential channel. The channel circumferential has a height h, illustrated in. This circumferential channelcommunicates with at least one upward longitudinal channel, which takes this oil flow into spaceand, subsequently, to the coils located at the top of stator of the electric motor, as shown in.

The circumferential channelcan be obtained directly by stacking sheets of electric steel. However, this will cause the height h to be an integer multiple of the thickness of the blade of the electric rotor steel. If this height h results in an oil flow deviated for the cooling of the electric motor coils that affects the flow required for the lubrication of the radial bearingsand, for example, an additional restriction can be provided by the partial juxtaposition of the outside diameter of the circumferential channelwith the diameter of the upward longitudinal channel, as represented by the dimension dr in the detail of.

In a further aspect of the invention, in which the rotor is configured for an asynchronous induction motor, the radial channelsand the circumferential channelare formed by stacking a plurality of stamped magnetic steel laminations. Each lamination includes a pattern comprising a central region that defines the circumferential channeland several circular cutouts positioned radially said circumferential channel. When stacked, these circular cutouts align to form radial channels, which serve as oil conduits extending from the circumferential channeltoward the rotor periphery.

To properly align the bar slots and maintain mechanical symmetry, each rotor lamination in the stack is rotated by a composite angle β relative to the one beneath it. The rotation angle β is defined as the sum of: (i) a lamination skew angle “Δα,” based on a skew angle “α” defined by the greater of the stator slot pitch and rotor slot pitch, and (ii) an interlock angle “φ,” based on the number and arrangement of rotor bars to compensate for lamination slit asymmetries. Skew and interlock angles are well-known design parameters in rotor lamination for induction motors. The lamination skew angle Δα is employed to reduce cogging torque and acoustic noise during motor operation. The interlock angle φ is used to compensate for geometric asymmetries introduced during the stamping process and helps ensure optimal rotor stack straightness. These angles are commonly combined to define the total rotation angle β applied between successive laminations during rotor assembly. As such, the specific calculation methods and construction techniques associated with skew and interlock angles need not be detailed herein.

For example, for a rotor stack height of 47.5 mm using laminations of 0.5 mm thickness, and a skew angle α=15°, the lamination skew angle is calculated as Δα=15°×0.5/47.5=0.1579°. If the rotor has 28 bars and an interlock index k=3, the interlock angle becomes φ=360°×3/28=38.5714°. The final rotation per lamination is thus β=Δα+φ=38.7293°.

The number of radial channels “nr” is selected to be an integer close to 360/β to ensure uniform distribution and symmetry, optimizing cooling performance and mechanical balance of the rotor. For the example above, 360/β≈9.3, so nr may be selected as either 9 or 10. In this context, the angle between adjacent radial channelsis defined as θ=360/nr. Therefore, the radial channelsare ideally spaced every 40° (for nr=9, as illustrated in) or 36° (for nr=10, as illustrated in).

The stacking orientation of each lamination is always performed by rotating each lamination in the same angular direction as the skewed rotor bar slots, as such, the radial channel pitch is always the same as the skewed rotor bar slots. However, depending on the relationship between θ and β, the resulting arrangement of the radial channel pitch will visually differ:

If θ>β, the radial channel pitch visually appears to follow the same angular direction as the skewed rotor bar slots, defining a “forward pitch” configuration ().