Patent Grant
12098721
This application claims priority to European Application No. 21181153.4 filed Jun. 23, 2021, the entire disclosure of which is incorporated herein by reference.
The current application relates to improving sealing and compliance in a scroll compressor, wherein such compressor could be used, for example, in refrigeration systems. In particular, the current application provides improved sealing between a low-pressure portion of the scroll-compressor and a high-pressure portion of the scroll compressor.
A compressor is an apparatus, which reduces the volume of a fluid by increasing the pressure of the fluid. In most common applications, the fluid is a gas.
Compressors are used, for example, in refrigeration systems. In a common refrigeration system, a refrigerant is circulated through a refrigeration cycle. Upon circulation, the refrigerant undergoes changes in thermodynamic properties in different parts of the refrigeration system and transports heat from one part of the refrigeration system to another part of the refrigeration system. The refrigerant is a fluid, i.e. a liquid or a vapour or gas. Examples of refrigerants may be artificial refrigerants like fluorocarbons. However, in recent applications, the use of carbon dioxide, CO2, which is a non-artificial refrigerant, has become more and more important, because it is non-hazardous to the environment. The present description illustrates the functionality of the compressor in connection with a refrigeration system. However, this is only one example and the described functionality could be used in various systems and different kinds of fluids, not only refrigerants.
A typical scroll compressor comprises a high-pressure side and a low-pressure side. At the low-pressure side the fluid enters the scroll compressor via a suction port, for example from a refrigeration cycle. The fluid is provided to a means for compressing, where it will be compressed. The compressed fluid will then be provided to the high-pressure side. At the high-pressure side compressed fluid is collected and leaves the scroll compressor via a discharge port, for example back to the refrigeration cycle. Compressing the refrigerant in the means for compressing reduces the volume of the refrigerant, while increasing its pressure and temperature.
Within the case of the compressor, the high-pressure side and the low-pressure side are separated from one another. A passage from the low-pressure side to the high-pressure side is formed by the means for compressing. In other words, the means for compressing may form a transition area from the low-pressure side to the high-pressure side.
In a scroll compressor, the means for compressing is formed by a scroll set, which comprises scroll plates, typically a stationary scroll plate and an orbiting scroll plate. Each of these scroll plates has a base plate and a projection in form of a spiral wrap, which extends from the base plate. In the assembled scroll compressor, the projections are interleaved, so that when the orbiting scroll plate moves relatively to the stationary scroll plate, refrigerant received from the suction port will be enclosed between the base plates and the interleaved projections. During the relative motion, the refrigerant will be moved within the interleaved projections from the outside of the interleaved spiral wraps towards the center of the scroll plates, i.e. the center of the projections. Thereby, the refrigerant will be compressed. When the compressed refrigerant reaches the center of the scroll plates, i.e. the center of the interleaved projections, the compressed refrigerant can be ejected from the scroll set through an opening in the base plate of the stationary scroll plate and into a high-pressure side of the scroll compressor from where the compressed refrigerant can be discharged through the discharge port.
The compression of the refrigerant increases the pressure of the refrigerant inside the scroll set. As such, the scroll set forms the passage or transition area between the low-pressure side of the scroll compressor and the high-pressure side of the scroll compressor. Sealing of compression chambers formed within the scroll set occurs by ease of lubricant, which lubricates the scroll plates, in particular their spiral wrap-shaped projections and the side of their base plates, which comprise said projections.
Further, the passage from the low-pressure side of the scroll compressor to the high-pressure side of the scroll compressor needs to be sealed, in order to prevent leakage. In a typical compressor, as is for example illustrated in
An axial gap has a quite large gap size of approximately 1 mm. Caused by manufacturing variations and deformation of the components of the scroll compressor due to pressure differential during operation, the size of the axial gap may change during operation of the compressor. Thereby, gap sizes of 0.2 to 1 mm are common. Such a change of the gap size causes wear at the seal and may create leakage in case that the seal is not capable of tightly sealing the axial gap. For example, for large gap sizes of approximately 1 mm, the seal may be squeezed into the gap, when the compressor operates at conditions with high pressure differential between low-pressure side and high-pressure side.
Hence, there is a need in the art for improving sealing of the high-pressure side and the low-pressure side in a scroll compressor.
The above-mentioned need is fulfilled by a scroll compressor according to the current invention. The scroll compressor comprises a case, which has a high-pressure side and a low-pressure side.
Further, the scroll compressor comprises a stationary scroll plate, which has a base plate with a first side. The first side comprises at least one projection, which forms a spiral wrap. In some preferred embodiments, the first side may be referred to as bottom side. Further, the base plate comprises a second side, which has a first annular protrusion. In some preferred embodiments, the second side may be referred to as top side. The first and second sides of the base plate may oppose each other.
Also, the scroll compressor comprises a pilot plate for separating the high-pressure side of the case from the low-pressure side of the case. The pilot plate abuts the second side of the stationary scroll plate, wherein the pilot plate has a first side with a second annular protrusion. The first annular protrusion of the second side of the stationary scroll plate and the second annular protrusion of the pilot plate may be in close proximity to one another. In this regard, close proximity means that the first and second protrusions are placed close towards one another but do barely not contact each other, thereby creating a small gap between the first protrusion and the second protrusion. For example, the first and second protrusions may be interleaved but do not contact one another. Alternatively, it may be possible that portions of the first and second protrusions contact each other, but this contact does not form a hermetically sealed interface. Accordingly, a small gap still is formed between the first and second protrusions, which is at least permeable to gas. The interleaved arrangement of the stationary scroll plate and the pilot plate provides for a floating connection between the stationary scroll plate and the pilot plate. Thereby, the stationary scroll plate is not tightly fixed at the pilot plate. Instead, the floating connection allows the stationary scroll plate to perform slight movements relatively to the pilot plate.
The first annular protrusion of the stationary scroll plate may extend axially from the second side of the stationary scroll plate and the second annular protrusion of the pilot plate may extend axially from the first side of the pilot plate.
Because of the arrangement of the first and second annular protrusions, is the gap formed between the first annular protrusion and the second annular protrusion is a radial gap. In this regard, radial refers to a direction perpendicular to the axial direction, which is for example given by the height of the compressor. This radial gap is formed by the radial space between axial extending surfaces of the first and second annular protrusions. This is different to the prior art, in which an axial gap is formed between radially extending surfaces of a stationary scroll plate and of a boundary.
In order to provide for best results, the first annular protrusion and the second annular protrusion may form concentric rings. Furthermore, the inner diameter of the first annular protrusion of the stationary scroll plate and the outer diameter of the second annular protrusion of the pilot plate may have approximately the same size, so that they provide for a small radial gap between the first and second annular protrusions. This way, the second annular protrusion may be located within the circular area formed by the first annular protrusion of the stationary scroll plate. Alternatively, the outer diameter of the first annular protrusion of the stationary scroll plate and the inner diameter of the second annular protrusion of the pilot plate may have approximately the same size. This way, the first annular protrusion may be located within the circular area formed by the second annular protrusion of the pilot plate.
Further, the scroll compressor comprises a seal, which seals said radial gap between the first annular protrusion and the second annular protrusion.
Providing first and second protrusions at the second side of the stationary scroll plate and the first side of the pilot plate, respectively, provides for an arrangement of the stationary scroll plate and the pilot plate, which separates the high-pressure side and the low-pressure side and replaces the axial gap with a radial gap, which is smaller in size. As such, a smaller gap can more easily be sealed and reduces seal deformation and improves the reliability of the seal. Furthermore, an axial gap as known in the art can change its size during operation of the compressor due to the pressure differential across the boundary between the low-pressure side and the high-pressure side because the increased pressure differential across the boundary may push the boundary towards the stationary scroll plate in the axial direction. In the compressor according to the current invention, the influences of the increased pressure differential on the radial gap are neglectable, since the radial gap does not change its size when the relative position between the pilot plate and the stationary scroll plate changes axially.
In the following, further preferred embodiments of the current invention are described.
In a preferred embodiment, the seal has an annular shape with an L-shaped cross-section. The annular shape allows for sealing the radial gap over the entire circumference of the first annular protrusion. The L-shaped cross-section may have a first leg and a second leg. The first leg may extend from an annular body of the annular seal into the center of its annular shape. The second leg may extend from the annular body of the annular seal in an angle of approximately 90 degree with respect to the first leg. Thereby, the first and second legs may form the L-shaped cross-section of the seal. The first leg may contact the second annular protrusion of the pilot plate and the second leg may contact the first annular protrusion of the stationary scroll plate. For example, the first leg may abut a front surface of the second annular protrusion and the second leg may abut a side of the first annular protrusion. Alternatively, for example if the inner diameter of the first annular protrusion is smaller than the inner diameter of the second annular protrusion, the first leg may abut a front surface of the first annular protrusion and the second leg may abut a side of the second annular protrusion.
Further, a step may be located between the first leg and the second leg at the side which forms the 90-degree angle between the first and second legs. Said step between the first and second legs may improve the durability of the seal. The step may stiffen the seal, so that it is prevented from being squeezed into the radial gap.
Further, a taper may be added to the first leg, i.e. the leg that abuts the front surface of either of the protrusions. Adding a taper means that at least one side of the first leg may be tapered. Thereby, the first leg may have a wedge-like shape. A wedge-shaped leg may have a surface that forms an inclined plane with respect to the approximately 90 degree between the first leg and the second leg. For example, the inclined plane may have an angle of approximately 5 degree. The taper may be added to the exterior surface of the leg, i.e. the surface that abuts the front surface of either of the protrusions. Alternatively or additionally, the taper may be added to the surface of the leg that opposes the aforementioned surface that abuts the front surface of the protrusion, i.e. the taper may be added to the surface of the leg that faces away from the front surface of the annular protrusion. Such a tapered surface may improve the fit of the seal to the respective protrusion and may reduce buckling of the seal.
In a preferred embodiment, a ring may be placed at the radial gap between the first annular protrusion and the second annular protrusion, thereby creating another radial gap between the respective protrusion and the respective leg of the seal and an axial gap between the other protrusion and the other leg. The ring may have a rectangular cross-section. The L-shaped seal may further comprise an annular recess opposite to the step. The ring may be placed within said recess. The ring may float within the first annular protrusion. Thereby, the ring may reduce the maximum radial gap that the seal needs to seal, which further improves the sealing. The ring may be made of a material which has a similar thermal expansion property as the stationary scroll plate. Preferably, the ring may be a metal ring. However, also non-metal materials, which have similar thermal expansion properties, are also possible.
In a preferred embodiment, the seal may be assembled on a seal plate. The seal plate may be made from a material with similar thermal expansion properties as the stationary scroll plate, preferably steel or cast iron. Assembling the seal on a seal plate may provide improved stability of the seal, in particular a stable form of the seal. When fabricating the seal, the exterior surfaces are fine-prepared after the seal is pressed to the seal plate, thereby reducing the magnitude of seal shrinkage when the temperature of the seal drops, because size reduction of the seal is limited by the sealing plate.
In a preferred embodiment, the seal may be made from a non-metal material. Examples of such materials may be synthetic polymers preferably composed of polyamides, such as nylon, polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK) or polyimide-based plastics (e.g. Vespel).
In a preferred embodiment, the second side of the stationary scroll plate may further comprise a third annular protrusion having a smaller diameter than the first annular protrusion and the first side of the pilot plate may further comprise a fourth annular protrusion having smaller diameter than the second annular protrusion. In the assembled scroll compressor, the third annular protrusion and the fourth annular protrusion may be in close proximity to one another, as has been described earlier with respect to the first and second annular protrusions. Between the third annular protrusion and the fourth annular protrusion, a radial gap is formed, similar what has been described with respect to the radial gap formed between the first and second annular protrusions. Additionally, to the aforementioned seal, which may be referred to as first seal, the compressor may further comprise a second seal. Then, the radial gap between the first and second annular protrusions may be sealed by the first seal and the radial gap between the third and fourth annular protrusions may be sealed by the second seal.
Further, an intermediate pressure cavity may be formed between the first side of the pilot plate and the second side of the stationary scroll plate as well as the first, second, third and fourth protrusions. As such, the first and second annular protrusions in conjunction with the first seal may form a first barrier, which separates the intermediate pressure cavity from the low-pressure side. Similarly, the third and fourth protrusions in conjunction with the second seal may form a second barrier, which separates the intermediate pressure cavity from the high-pressure side. In the intermediate pressure cavity, the pressure may be higher than the pressure in the low-pressure side, but lower than the pressure in the high-pressure side. Further, by sealing the radial gap between the first and second annular protrusions, the first seal may seal the intermediate pressure cavity from the low-pressure side. Also, by sealing the radial gap between the third and fourth annular protrusions, the second seal may seal the intermediate pressure cavity from the high-pressure side.
Besides the stationary scroll plate, the compressor may also comprise an orbiting scroll plate. The orbiting scroll plate and the stationary scroll plate may form a means for compressing. The stationary scroll plate may comprise an opening, which forms an outlet of the means for compressing and the pilot plate may comprise a corresponding opening. Both openings may form a channel from the means for compressing to the high-pressure side. Via this channel, compressed fluid, which exits the means for compressing, may be provided to the high-pressure side. As such, the barrier formed by the third and fourth protrusions in conjunction with the second seal separates the intermediate pressure cavity also from the channel between the means for compressing and the high-pressure side. The second seal may have any of the abovementioned configurations that have been described for the first seal.
Further, a bleed hole may be provided that connects the intermediate pressure cavity at least temporarily during operation of the scroll compressor to a compression chamber formed in a scroll set of the scroll compressor in order to provide for pressure balancing.
The abovementioned preferred embodiments are not mutually exclusive. This means that features described for some preferred embodiments may also be utilized in some other preferred embodiments unless it is clear from the description that these features cannot be combined.
In the drawings, like reference characters generally refer to the same parts throughout the different drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.
In the following description, various embodiments of the invention are described with reference to the following drawings, in which:
The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.
Between the stationary scroll plate 120 and the boundary 140, i.e. between the top surface of the stationary scroll plate 120 and the bottom surface of the boundary 140, a gap 145 is formed. The gap 145 is along the axial direction of the z direction as defined by the case no of the scroll compressor wo and indicated in
In a typical scroll compressor, the stationary scroll plate is floating with respect to the boundary, so that the stationary scroll plate cannot be fixed directly at the boundary (e.g. by welding or fastening with a fastening means) in order to keep the gap manageable. However, such axial gaps are rather large, which leads to shortened lifetimes of the seal.
As can be seen in the detailed enlarged section of
In the embodiment depicted in
The radial gaps formed between the first and second protrusions 222, 242 and the third and fourth protrusions 224, 244, respectively, are sealed by annular seals 250 and 255, respectively.
Between the first and second protrusions 222, 242 and the third and fourth protrusions 224, 244, an intermediate pressure cavity 260 is formed by the stationary scroll plate 220 and the pilot plate 240. Said intermediate pressure cavity 260 may have a pressure higher than the low-pressure side, but smaller than the high-pressure side. Further, a bleed hole (not shown) may be provided which connects the intermediate pressure cavity 260 with a compression chamber formed between the stationary scroll plate 220 and the orbiting scroll plate 230 at least temporarily during the operation of the scroll compressor 200.
The stationary scroll plate 500 comprises a first annular protrusion 505 and a third annular protrusion 525 on its second side and a spiral wrap 510 at its first side. In
The pilot plate 515 is placed above the stationary scroll plate 500 and comprises a second annular protrusion 520 and a fourth annular protrusion 530 on its first side. In
The first and second annular protrusions 505, 520 are in close proximity to one another and form a radial gap. The radial gap is sealed by a first annular seal 550. Also, the third and fourth annular protrusions 525, 530 are in close proximity to one another and form another radial gap. Said radial gap is sealed by a second annular seal 555, Between the pilot plate, the stationary scroll plate and the first, second, third, and fourth protrusions, an intermediate pressure cavity 545 is formed.
In
Within the interleaved scroll plates, the means for compressing 570 is formed. The means for compressing 570 is connected to the high-pressure side 585 via a channel 575, which is formed by corresponding openings in the stationary scroll plate and the pilot plate. The intermediate pressure cavity is sealed from the low-pressure side 580 by ease of the first seal and sealed from the channel 575 between the means for compressing and the high-pressure side 585 by ease of the second seal.
The seal 705a depicted in
Caused by forces created during compressor operation, like e.g. thermal deformation, the seal 705a can buckle either upwards or downwards. Typical seals may be made from synthetic polymers, for example Teflon, while the stationary scroll plate and the pilot plate may be made from cast iron. Teflon has a thermal expansion coefficient, which is five times the thermal expansion coefficient of cast iron. When the operating temperature increases, the expansion of the seal is restricted by the stationary scroll plate, which generates compressive stress inside the seal. This compressive stress may lead to buckling as is depicted in
In the configuration of the scroll compressor according to the current invention, the seal is not only restricted by the annular protrusion of the stationary scroll plate, but also by the annular protrusion of the pilot plate. This is illustrated in
What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the scope of the appended claims.
| Number | Date | Country | Kind |
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| 21181153 | Jun 2021 | EP | regional |
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| Number | Date | Country | |
|---|---|---|---|
| 20220412348 A1 | Dec 2022 | US |
