Method of aligning scroll compressor components

Information

  • Patent Grant
  • 6488489
  • Patent Number
    6,488,489
  • Date Filed
    Monday, February 26, 2001
    23 years ago
  • Date Issued
    Tuesday, December 3, 2002
    22 years ago
Abstract
An improved method of aligning the bearing components within a scroll compressor includes the step of mounting the crankcase to be an interference fit within the center shell, and having a surface abutting a true upper surface of the shell. This ensures that the axis of the bearing in the crankcase is idealized and centered on the center axis of the center shell. At the same time, the lower bearing is mounted on the lower end cap, and is also cut to be concentric with a force fit outer surface of the end cap. This ensures the lower bearing is also centered on the inner periphery of the center shell. Once it is ensured the center shell is true, then it is also thus ensured the upper and lower bearings are aligned on a common axis. An improved lower bearing structure with a reverse taper is also disclosed.
Description




BACKGROUND OF THE INVENTION




This invention relates to a method wherein the components adjacent the top and bottom of a scroll compressor are all aligned with regard to a common reference such that total alignment of the components can be more easily and accurately achieved.




Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor, first and second scroll members each include a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. A shaft is operably connected to one of the scroll members to cause that scroll member to orbit relative to the other. As the two scroll members orbit, compression chambers defined between the wraps of the two scroll members decrease in volume, compressing an entrapped refrigerant.




Historically, scroll compressors are mounted in a sealed housing. The housing includes a center shell and upper and lower end caps. The shaft which drives the orbiting scroll member is typically driven by an electric motor mounted within the center shell. The shaft extends along a rotational axis, and is operably connected to the orbiting scroll to cause orbiting movement of the orbiting scroll. Typically, the shaft is mounted in bearings adjacent upper and lower positions. The upper bearing is mounted within a crankcase, which supports the orbiting scroll member. The lower bearing is typically on an opposed side of the motor from the scroll members. Historically, a bearing support has extended radially inwardly from the center shell to support the lower end of the bearing.




More recently it has been proposed to mount the lower bearing in the scroll compressor on the lower end cap. Thus, in prior U.S. patent application Ser. No. 09/376,915, filed Aug. 18, 1999, and entitled “BEARING ASSEMBLY FOR SEALED COMPRESSOR”, and further in a co-pending application entitled “LOWER END CAP FOR SCROLL COMPRESSOR” filed on Jun. 1, 2001 and assigned Ser. No. 09/872,972, lower end cap structure for mounting a bearing has been disclosed.




Further, it has recently been proposed to force fit the crankcase into the center shell such that the position of the crankcase is ideally located relative to the center shell. Such structure has been disclosed in co-pending application Ser. No. 09/176,576, filed Oct. 21, 1998 and entitled “FORCE-FIT SCROLL COMPRESSOR ASSEMBLY” and now assigned U.S. Pat. No, 6,193,484.




However, the two ideas have never been proposed to be combined.




SUMMARY OF THE INVENTION




In the disclosed embodiment of this invention, the center shell is utilized as a point of reference to ideally position the lower bearing through the mount of a lower end cap, and the crankcase both at a location ideally determined and positioned by the common reference. In a preferred embodiment, the common reference is provided by the center shell. The center shell is machined to have carefully controlled end surfaces that are both perpendicular to the center axis of the center shell, and which are ideally close to being cylindrical. The initial shell formation can be slightly out of round (i.e., on the order of 1.0 mm), as it will be brought to complete roundness by the computer cut surfaces of both the crankcase and the lower end cap, and as will be explained below.




The lower end cap is machined such that it has mount surfaces which are both perpendicular to the lower bearing bore and a set radial spacing away from the axis of the lower bearing. When this lower end cap is mounted within this center shell, the bearing is thus ideally located relative to the center axis of the center shell.




Further, the crankcase is machined to have an idealized outer cylindrical surface, and a flat end face which abuts the end face of the center shell. When this crankcase is mounted in this center shell along with the lower end cap, it is assured that the crankcase and the lower end cap are both mounted at a proper orientation relative to each other. Since both the end cap and the crankcase are separately machined on their own to ensure that the axis of the bearing for the shaft that they each carry are true to the outer periphery of the individual component, it is also ensured that the two bearings are thus ideally located relative to each other. Once these two bearing mounts for the shaft are ideally determined, the other components of the scroll compressor come together easily and at assured aligned position.




Thus, the present invention provides a simplified method of ideally locating components within a scroll compressor such that it is assured they are properly located.




These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a cross-sectional view through the inventive scroll compressor.





FIG. 2A

is an enlarged view of circle portion


2


A from FIG.


1


.





FIG. 2B

is an enlarged view of circle portion


2


B from FIG.


1


.





FIG. 3

schematically shows the formation of a shell component.





FIG. 4A

shows the first step in assembly.





FIG. 4B

shows a subsequent step.





FIG. 4C

shows yet another step.





FIG. 4D

shows yet another step.





FIG. 5A

is a top view of an end cap.





FIG. 5B

shows an enlarged portion of one location on the

FIG. 5A

end cap.





FIG. 6

shows another feature of an inventive bearing.





FIG. 7

shows a feature of the

FIG. 6

embodiment.











DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT





FIG. 1

illustrates a scroll compressor


20


incorporating an orbiting scroll


22


and a non-orbiting scroll


24


. A driveshaft


26


is driven by a motor stator


28


through rotor


30


. The driveshaft is operatively connected to cause orbiting movement of the orbiting scroll


22


. The lower bearing


32


is mounted on an end cap


34


. A lower end


33


of the shaft


26


engages the lower bearing


32


. The end cap


34


has circumferentially spaced u-shaped portions


36


positioned radially inward of a lower end


38


of a center shell


40


. The lower end


38


of the center shell


40


has an axial end surface


39


which abuts a surface on the lower shell


34


, as will be explained below.




An inner periphery


41


of the center shell is formed to be close to an idealized cylinder to facilitate alignment, as will be explained below. An upper end cap


42


is secured to the center shell


40


. A crankcase


44


supports the orbiting scroll


22


, as known. An outer peripheral portion


46


of the crankcase


44


has an outer surface


47


which is force fit within the center shell


40


.




A bearing


48


is mounted within the crankcase


44


and supports an upper end of the shaft


26


. A radially outwardly extending lip


50


of the crankcase


44


abuts an end


52


of the housing


40


. As will be explained below, the combination of the force fit crankcase and the bearing mounted on the lower end plate provides assurance that the bearings


32


and


48


are located on an axis which is common by setting both bearings based upon a common reference.




As shown in

FIG. 2A

, the crankcase


44


has its outer periphery


47


force fit within the inner periphery


41


of the center shell


40


. The radially outwardly extending flange


50


abuts the end face


52


.




The downwardly facing surface


90


of the flange


50


is machined to be perpendicular to the center axis of the crankcase


47


. Moreover, the outer periphery


47


of the crankcase


44


is also machined to be concentric with the bearing mount


48


. Thus, by known computer control methods, Applicant ensures that the bore for the bearing


48


is concentric and ideally centered with the outer surface


47


and perpendicular to flange surface


90


. It should be understood that the surface


47


may have some discontinuities, however, it is generally cylindrical, and concentric with the center axis of the bearing


48


. Details of the preferred crankcase can be determined from U.S. Pat. No. 6,193,484.




Now, when the crankcase is mounted within the center shell


40


as is shown in

FIG. 2A

, due to the surface


90


abutting surface


52


, and due to the force fit


47


, one can be assured that the center axis of the bearing


48


is parallel and concentric with the interior axis of the center shell


40


.




At the same time, a similar end face


54


is formed on the lower end plate


34


. The axial end


39


of the lower end


38


of the center shell housing abuts the surface


54


. As with the crankcase, this ensures that the lower end cap


34


is properly orientated within the center shell


40


. Moreover, the outer periphery


91


of the portions


36


are sized to provide at least a slight force fit within the center shell


40


. Again, this ensures that the orientation of the lower end cap


34


within the center shell


40


is idealized and true.




The center axis of the bearing


32


is preferably cut, as will be explained below, such that it is concentric with the outer periphery of the sections


36


and perpendicular to surface


39


. This ensures that the bearing axis for bearing


32


is also based upon the center axis of the inner periphery


41


of the center shell


40


. By utilizing these two techniques, applicant thus ensures the bearing


48


is centered on and parallel to an axis which is determined based upon the same point of reference as the axis for the bearing


32


. Applicant thus ensures the bearings are more likely aligned than has been the case in the prior art.





FIG. 3

shows a machining operation


10


highly schematically. A shell preform


12


which becomes center shell


40


is initially formed into a generally cylindrical shell by rolling a portion of steel and then welding that steel into the perform and expanding from the inner diameter. An expanding mandrel


16


extends into the inner periphery of the shell


12


and ensures the inner periphery turns between centers of the lathe. The mandrel then brings the shell


12


to a pair of opposed machining lathes


14


which cut the end surfaces on the center shell. The operation for machining the shell is as known, and is within the skill of a worker in this art. The shell preform is thus formed into the center shell


40


, and as shown in

FIG. 4A

, the end surfaces


39


and


52


both define flat surfaces which are computer controlled to be quite close to being true flat parallel planes perpendicular to inner axis. Moreover, the inner periphery


41


is extremely close to being a true cylindrical bore. As mentioned above, the inner periphery


41


can be slightly out of round at this point, as the crankcase and lower end cap surfaces will bring it to being true once inserted.




In a first step of assembling the scroll compressor, the stator


28


is initially placed within the center shell, as shown in FIG.


4


A. The center shell may be heated to receive the stator, and then may then cool to secure itself onto the stator. Moreover, electrical connections are preferably made during the mounting of the stator, and as disclosed in co-pending U.S. patent application Ser. No. 09/415,122, filed on Oct. 8, 1999 and entitled “DEFORMED COMPRESSOR MOTOR WINDING TO ACCOMMODATE COMPONENTS”.




As shown in

FIG. 4B

, the next step is to then force the center shell


40


downwardly onto the lower end cap


34


. As described above, the lower end


38


of the center shell


40


provides a force fit onto the portions


36


, such that at this point the bearing


32


has its center axis ideally centered relative to the center axis of the housing shell


40


. At this time, the center shell may be tack welded to the lower end cap


34


to secure the two together for subsequent processing until final girth weld.




The next step is to mount the rotor


30


and shaft


26


within the bearing


32


and within the stator


28


, as shown in FIG.


4


C.




The next step is to force the crankcase


44


into the center shell


40


. With this forced movement, the flange


50


is brought against the end


52


. At this point, and since the bearing bore


48


has been previously cut to be a true concentric bore relative to the outer periphery


47


of the crankcase


44


, it can be ensured that the bearings


48


and


32


are both centered on an axis cut relative to a common reference, the center axis of the center shell


40


.




The components of the orbiting scroll and the non-orbiting scroll, including all the anti-rotation couplings, seals, etc., as are known are then placed within the compressor. The end cap


42


is then brought downwardly and the components are forced together and the upper end cap is tack welded. At that point, the end caps are welded to the center shell, securing the entire assembly.





FIG. 5A

shows the lower end cap


34


, with the bearing


32


. As can be appreciated, the u-shaped surfaces


36


are circumferentially spaced. The outer periphery


91


of these components is cut such that this outer periphery is true and concentric to the central axis X of the bearing


32


. As is explained in greater detail in co-pending U.S. patent application Ser. No. 09/376,915, filed Aug. 18, 1999 and entitled “BEARING ASSEMBLY FOR SEALED COMPRESSOR” this is ensured by cutting the center X of the bearing to be concentric with the outer surface


91


of the portions


39


.

FIG. 5B

shows another view of the outer surface


91


in the portion


36


.




In sum, by ensuring the centers of the bearings


32


and


48


are both cut and measured by computer controlled equipment to be concentric with a common reference Applicant ensures the two bearings are ideally located and aligned relative to each other. The present invention thus improves greatly upon the prior art.





FIG. 6

shows a bearing embodiment


300


wherein the bearing hub has an upper end


302


which is tapered laterally inwardly from a lower end


304


. When the bearing body


310


, as shown in

FIG. 7

, is inserted, the upper end is bent back as shown at


312


relative to the lower end


314


. The bearing body


310


is cylindrical, as shown. In the prior art, when the bearing was inserted, it bent the unsupported upper end radially outwardly, and resulted in the free end of the hub being bent outwardly, rather than being a cylindrical surface. Thus, this reverse tapering provides benefits. free end of the hub being bent outwardly, rather than being a cylindrical surface. Thus, this reverse tapering provides benefits.




Essentially, the computer cut concentric outer peripheral surfaces on the crankcase and the lower end cap ensure that the bearing bores are each equally spaced radially from the inner periphery of the center shell. At the same time, the flat surfaces ensure that the crankcase and lower end cap will be parallel to each other, such that the axes of their bearing bores will be concentric and parallel also.




Although a preferred embodiment of this invention has been disclosed, a worker in this art would recognize that modifications may come within the scope of this invention. For that reason the following claims should be studied to determine the true scope and content of this invention.



Claims
  • 1. A scroll compressor comprising:a first scroll member having a base and a generally spiral wrap extending from said base; a second scroll member having a base and a generally spiral wrap extending from its base, a shaft for driving said second scroll member to orbit relative to said first scroll member; a crankcase for supporting said second scroll member, said crankcase having an outer peripheral surface of a predetermined outer diameter, said outer peripheral surface of said crankcase being machined to be concentric with a bearing bore found at a central axis of said crankcase, said bearing bore receiving an upper bearing; a housing enclosing said shaft and said first and second scroll members and said crankcase, said housing including a center shell and upper and lower end caps; said lower end cap mounting a lower bearing for supporting a lower end of said shaft and said bearing bore in said crankcase mounting an upper bearing for supporting an upper end of said shaft; said lower bearing having a bearing axis which is cut to be concentric and parallel relative to an outer peripheral surface on said lower end cap, and said outer peripheral surface of said lower end cap being concentric with an inner peripheral surface of said center shell, and said outer peripheral surface of said crankcase being concentric with said inner peripheral surface of said center shell such that said upper and lower bearings are concentric with regard to each other.
  • 2. A scroll compressor as recited in claim 1, wherein said center shell has upper and lower axial ends which are cut to be parallel to each other, and said crankcase having a radially outwardly extending flange which abuts said upper end of said center shell and is cut to be perpendicular to said axis of said upper bearing such that said crankcase is properly aligned within said center shell, and said lower end cap having a surface which is cut to be perpendicular to said rotational axis of said bearing such that said lower end cap is properly mounted within said center shell, and such that said axes of said upper and lower bearings are aligned.
  • 3. A scroll compressor as recited in claim 1, wherein said lower bearing is initially formed to have a reverse taper such that insertion of said shaft into said lower bearing causes said reverse taper to move more towards a cylindrical surface.
  • 4. A scroll compressor comprising:a first scroll member having a base and a generally spiral wrap extending from said base; a second scroll member having a base and a generally spiral wrap extending from its base, a shaft for driving said second scroll member to orbit relative to said first scroll member; a housing enclosing said shaft and said first and second scroll members and a crankcase, said housing including a center shell and upper and lower end caps; said lower end cap mounting a lower bearing for supporting a lower end of said shaft and a bearing bore in said crankcase mounting an upper bearing for supporting an upper end of said shaft; said lower end cap mounting a bearing through a bearing hub, said bearing hub having an axially upper end which is tapered inwardly towards a central axis of said hub from an axially lower end, and a cylindrical bearing forced into said hub such that said upper end of said hub is bent back towards a more cylindrical surface with said lower end of said hub.
  • 5. A method of assembling a scroll compressor comprising the steps of:1) providing a center shell having a pair of opposed axial ends, said axial ends being cut to be parallel to each other, forming a crankcase having an outer peripheral surface which is generally cylindrical and centered on an axis, and provides a tight fit within a cylindrical inner surface of said center shell, said crankcase having a radially outwardly extending surface for abutting said axial end of said center shell, providing a lower end cap having an outer peripheral surface, sized to be a close fit within said cylindrical inner surface of said center shell, and said lower end cap having a face formed to be perpendicular to a central axis of a lower bearing mounted on said lower end cap; and 2) mounting said crankcase within said center shell and mounting said lower end cap within said center shell such that said axes of said crankcase and lower bearings are both concentric to a common point of reference.
  • 6. A method as recited in claim 5, wherein both said crankcase and said lower end cap are formed to have a surface perpendicular to an end surface of said center shell, such that when said crankcase and said lower end cap are mounted within said center shell, said crankcase and said lower end cap will both have said surfaces be parallel to each other, said crankcase having a bearing bore centered on an axis for receiving an upper bearing and such that said axes of the bearing bores formed in said crankcase and said lower end cap will be concentric and parallel.
US Referenced Citations (2)
Number Name Date Kind
5188520 Nakamura et al. Feb 1993 A
5564186 Hori et al. Oct 1996 A
Foreign Referenced Citations (4)
Number Date Country
59-28088 Feb 1984 JP
61-8487 Jan 1986 JP
61-250393 Nov 1986 JP
4-166688 Jun 1992 JP