US3760478A

US3760478A - Method for assembling a rotary sliding vane compressor

Info

Publication number: US3760478A
Application number: US00185994A
Authority: US
Inventors: L Harlin
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1971-10-04
Filing date: 1971-10-04
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25
Also published as: AU464004B2; FR2155583A5; JPS5550198B2; GB1383034A; AU4645872A; DE2248647A1; BR7206524D0; CA965064A; JPS4844805A; IT986855B

Abstract

An optimum clearance is established at the contact point of the compressor''s rotor and cylinder, within which cylinder the rotor is eccentrically rotated to provide a crescent-shaped compression chamber, to minimize friction at that point while at the same time minimizing leakage therethrough from the high to the low pressure side of the compression chamber. This is achieved by initially coating the rotor''s cylindrical surface with a selflubricating material, such as TEFLON. Thereafter, when assembling the compressor, the cylinder is pivoted relative to the rear bearing plate until it engages the rotor and provides a contact point with zero clearance. To maintain this precise alignment, holes are then drilled and reamed through the front plate and into the cylinder and through the cylinder and into the rear plate, after which dowel pins are driven into the holes. When the compressor subsequently operates in its intended environment and under normal operating conditions, thermal diferentials between the rotor and cylinder may cause expansion of at least one of those elements as a result of which the self-lubricating material wears until a desired very close sealing fit, with minimum friction, is established at the contact point thereby optimizing the clearance thereat.

Description

Harlin Sept. 25, 1973 METHOD FOR ASSEMBLING A ROTARY SLIDING VANE COMPRESSOR [75] Inventor: Lester E. Harlin, York, Pa. [73] Assignee: Borg-Warner Corporation, Chicago,

Ill.

[22] Filed: Oct. 4, 1971 [21] App]. No.: 185,994

[52] US. Cl 29/156.4 R, 29/434, 29/558 [51] lnt. Cl B23p 15/00 [58] Field of Search 29/l56.4, 156.4 WL,

[56] References Cited UNITEDSTATES PATENTS 3,011,449 12/1961 Ernst 418/71 2,467,121 4/1949 Ferris 29/156.4 R 3,642,388 2/1972 Maistrelli.. 418/30 3,552,895 1/1971 Bayley 418/178 3,415,058 12/1968 Underwood et al. 418/30 3,190,183 6/1965 Walker et al. 418/178 3,193,190 7/1965 Lindberg 418/86 Primary ExaminerCharles W. Lanham Assistant Examiner-M. J. Keenan Attorney-Donald W. Banner et a1.

[5 7 ABSTRACT An optimum clearance is established at the contact point of the compressors rotor and cylinder, within which cylinder the rotor is eccentrically rotated to provide a crescent-shaped compression chamber, to minimize friction at that point while at the same time minimizing leakage therethrough from the high to the low pressure side of the compression chamber. This is achieved by initially coating the rotors cylindrical surface with a self-lubricating material, such as TEF LON. Thereafter, when assembling the compressor, the cylinder is pivoted relative to the rear bearing plate until it engages the rotor and provides a contact point with zero clearance. To maintain this precise alignment,

holes are then drilled and reamed through the front plate and into the cylinder and through the cylinder and into the rear plate, after which dowel pins are driven into the holes. When the compressor subsequently operates in its intended environment and under normal operating conditions, thermal diferentials between the rotor and cylinder may cause expansion of at least one of those elements as a result of which the selflubricating material wears until a desired very close sealing fit, with minimum friction, is established at the contact point thereby optimizing the clearance thereat.

8 Claims, 4 Drawing Figures METHOD FOR ASSEMBLING A ROTARY SLIDING VANE COMPRESSOR BACKGROUND OF THE INVENTION I This invention relates generally to a rotary compressor of the sliding vane type and more particularly to an arrangement and an assembling method for enhancing the compressors performance, capacity, efficiency and reliability. The invention is especially attractive when practiced with respect to a rotary sliding vane compressor adapted for use in an automotive air-conditioning system and will be described in that environment.

In a rotary compressor, vanes are slidably received in slots of a rotor revolving within a cylindrical wall of a cylinder and about a rotational axis offset oreccentric relative to the walls axis. At the point of closest spacing between the rotor and cylinder (called the contact point), very little clearance is provided in order that a crescent-shaped compression chamber is formed between the rotor and cylindrical wall and between parallel spaced front and rear bearing plates respectively positioned adjacent to the two sides of the cylinder. The

vanes bear against the cylindrical wall as the rotor rotates so that gas introduced into one end or side (called the low pressure side)'of the compression chamber is compressed and discharged from the other end or high pressure side at a higher pressure. For maximum capacity and efficiency, it is important that the clearance at the contact point be minimized to effectively seal or isolate the high and low pressure sides of the compression chamber from each other. The greater the clearance at the contact point, the greater will be the leakage through that point fromthe high to the low pressure side of the, compression chamber, and the greater will be the loss of compression.

Some contact point clearance is necessary, however, in the previously developed compressors since otherwise metal-to-metal contact and friction would take place, resulting in unnecessary wear and very likely in premature compressor failure. Even though a substantial clearance may be provided when the compressor is manufactured, under severe operating conditions high temperatures may cause metal expansion to the extent that undesired metal-to-metal contact and friction still develops at the contact point. Hence, in the past it was expedient to design a rotary compressor, particularly one that was to be employed in an automobile as part of an air-conditioning system, to have a contact point clearance large enough so that under all operating conditions, to which the compressor may be subjected, metal-to-metal contact and consequent compressor failure would be avoided. Any time there is a complete loss of contact point clearance, compressor failure is likely to occur. In order'to accommodate the extreme conditions under which a compressor may operate, the objective of zero leakage at the contact point therefore had to be sacrificed or compromised.

In addition to the need for unnecessarily large contact point clearances in prior compressors, a problem also exists in maintaining the alignment or registration of the cylinder and the front and rear bearing plates, in which plates the rotor is joumalled. When gases are compressed by a rotary compressor, very high forces develop within the compression chamber and they tend to shift or pivot the cylinder relative to one or both of the bearing plates. Such undesired misalignment may occur even though the plates and cylinder are held together by several large bolts or studs and nuts. Shifting is possible because of the necessary dimensional variations between the bolts and studs and the holes through which they extend. As a result, the rather large contact point clearance originally built into a rotary compressor may even become larger due to shifting of the compressor parts relative to each other.

The present invention is calculated to overcome these shortcomings of prior rotary compressors by providing a novel assembling method which ensures and maintains an optimum contact point clearance to achieve less leakage than previously obtainable while at the same time introducing no significant friction.

It is, therefore, an object of the invention to provide a unique arrangement for optimizing the contact point clearance in a rotary sliding vane compressor.

It is another object to provide a more efficient rotary compressor with improved sealing properties and enhanced immunity of the moving parts against metal-tometal contact and consequent metal wear.

A further object is to provide a compressor that is more reliable and immune to failure than those previously developed.

An additional goal is to provide a method for assembling the uniquely constructed compressor so that precise alignment of the compressors parts will always be retained under the most severe operating conditions.

SUMMARY OF THE INVENTION In accordance with one aspect of the invention, a method is disclosed for assembling a rotary sliding vane compressor wherein a slottedrotor, with an external cylindrical surface of self-lubricating material, has its drive shaft joumalled in bearings of parallel spaced front and rear bearing plates to rotatably mount the rotor eccentrically within an internal cylindrical wall of a cylinder positioned between the bearing plates thereby to provide, between the cylindrical surface and wall and between the bearing plates, a crescent-shaped compression chamber having high and low pressure sides sealed from each other, and in which dowel pins extend between the cylinder and front and rear plates to maintain their alignment and to prevent any shifting of those three elements relative to each other. The novel method comprises the steps of rotatably mounting the drive shaft in the bearing of the rear plate, and positioning the cylinder around the rotor and adjacent to the rear plate. Thereafter the cylinder is pivoted relative to the rear plate to establish a contact point, between the rotors cylindrical surface and the cylinders cylindrical wall, that provides a line-to-line sealing fit withzero clearance. The front and rear plates, cylinder and rotor are then held in assembled relationship, after which at least one hole is drilled and reamed parallel to the rotors axis and through portions of the front plate and the cylinder, and at least one other hole is drilledand reamed parallel to the rotors axis and through portions of the cylinder and the rear plate. A dowel pin is then driven into each of the holes.

DESCRIPTION OF THE DRAWINGS The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description in conjunction with the accompanying drawings in which like reference numbers identify like elements, and in which:

FIGS. 1 and 2 are different section views of a rotary sliding vane compressor constructed in accordance with the present invention, the FIG. 1 view being taken along section line 1-1 in FIG. 2 while the sectional view of FIG. 2 is taken along section line 2-2 in FIG. 1; and,

FIGS. 3 and 4 are exploded, perspective views illustrating the novel manner in which the compressor of FIGS. 1 and 2 is assembled.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT To simplify the explanation of the invention, the structure and operation of the disclosed compressor will initially be described without regard to the novel assembling method concept. The compressor has a casing which includes a cylinder 11 having an internal cylindrical wall or bore 12 extending therethrough, a front bearing plate 15, and a rear bearing plate 16, all assembled and secured together in a manner to be described. Casing 10 provides or defines a closed cylindrical cavity formed by cylindrical wall 12 and

bearing plates

15 and 16 which serve as parallel spaced end walls for the cavity. A rotor assembly 20 (see especially FIG. 2) is rotatably mounted eccentrically within wall 12 and includes a slotted rotor 21 having a series of four slots 22 arranged circumferentially and each extending along a plane parallel to the rotors axis. The closed end of each slot may be referred to, for convenience, as the bottom end. Each of a series of four reciprocating vanes or blades 23 is slidably mounted in a respective one of slots 22. For reasons to be explained, the cylindrical surface of rotor 21 is coated or bonded with a layer 21a of self-lubricating material, such as TEFLON.

The eccentric positioning of rotor assembly 20 is obtained by rotatably mounting rotor 21 on an axis offset with respect to the axis of cylindrical wall 12. As is best seen in FIG. 2, at the contact point (indicated by reference numeral 24) between coating 21a and cylindrical wall 12 there is essentially zero clearance. A seal is thus created at contact point 24 so that the open space bounded by rotor 21, cylinder 11 and

bearing plates

15 and 16 provides a crescent-shaped compression chamber, identified by the numeral 25. Rotor 21 and casing 10 are made so that the dimension between the parallel rotor faces 26 and 27 is slightly less than the spacing between

bearing plates

15 and 16. In this way, very small restrictive clearances (denoted by the reference numbers 28 and 29) are established between the rotor faces and bearing plates to permit rotor 21 to rotate freely without any metal-to-metal contact, thereby minimizing friction between the flat surfaces of the rotor and bearing plates.

Rotor 21 has a drive shaft 30 journalled in bearings 31 and 32 affixed to bearing

plates

15 and 16 respectively. The left end of shaft 30 (as viewed in FIG. 1) projects outwardly of front bearing plate 15 so that the shaft may be driven. Since the illustrated embodiment is especially adapted for automotive use, it is contemplated that a V-belt pulley and clutch mechanism (not shown) would be coupled to the left end of shaft 30 to permit the compressor to be driven by the engine fan belt or accessory drive belt of the automobile. The disclosed compressor may, of course, be employed in many different environments and may be used in other than refrigeration or air-conditioning systems to compress a variety of different gaseous fluids. Whatever the driving means, it may conveniently be coupled to drive shaft 30.

While shaft 30 and rotor 21 are fixed with respect to each other, a small amount of axial movement of those elements may occur within the limits defined by the separation between

bearing plates

15 and 16. As illustrated in FIG. 1, rotor 21 is centered between

walls

15 and 16 and, accordingly, clearances 28 and 29 are equalized. As will be described later, the equalization of the clearances will be retained in the presence of axial forces tending to decenter the rotor.

The compressor is designed to operate when rotor assembly 20 revolves in a clockwise direction as viewed in FIG. 2, during which time vanes 23 firmly bear against cylindrical wall 12 and establish fluid-tight sealed connections thereto. In operation, suction refrigerant gas from the evaporator of the automotive airconditioning system is admitted to an inlet 35 formed in cylinder 11. As is shown in FIG. 2, this refrigerant gas flows into the suction portion of compression chamber 25. As the rotor is driven clockwise, the gas is'trapped between two adjacent vanes 23 and carried forward toward the discharge area. As this occurs, the volume between the adjacent vanes is reduced thereby resulting in a corresponding increase in pressure of the gas. A discharge valve assembly 36 is located in the discharge zone for assuring proper compression of the gases issuing from three rows of outlet or discharge ports 37 in cylinder 11 and for preventing reverse flow of gases back into compression chamber 25. Valve assembly 36 is of the reed type comprising three valve reeds 38 respectively held in place by three valve guards or stops 39. The compressed refrigerant gas emanating from ports 37 flows into a chamber 42 defined by cylinder 11 and a cover plate 43.

The processing of the high pressure gas after it is delivered to chamber 42 will be considered later. At this juncture it is desirable to describe the lubricating system in the compressor. Briefly, pressurized oil is supplied to all of the moving components and bearing surfaces to provide proper lubrication and to assist in isolating the high and low pressure sides of the compression chamber from each other. In addition, oil is delivered to the bottom ends of slots 22 to force vanes 23 outwardly and toward wall 12.

More particularly, a reservoir of oil or sump 44 is provided in the lower portion of a shell 46, the open end of which is attached and hermetically sealed to a mounting ring 47 in turn affixed to casing 10.

Oil passages

49 and 51, formed in plate 16 and mounting ring 47 respectively, and pick-up tube 52 to establish a flow path between the oil sump and the inlet of an oil pump 54 which is secured to plate 16 by four cap screws 55 and preferably is of the conventional internal gear-type having a freely rotatable internally-toothed outer gear 56 driven by an externally-toothed inner gear 57 eccentrically positioned within gear 56. A preferred construction of oil pump 54 is shown in detail in copending U.S. Pat. application Ser. No. 160,694, filed July 8, 1971 in the name of Lester E. I-Iarlin, and assigned to the present assignee. Reference may be made to that application for a more detailed illustration of oil pump 54. The right end of drive shaft 30 (as viewed in FIG. 1) projects outwardly from casing 10 and is keyed to inner gear 57 to drivingly connect the shaft to the gear.

The upper end of passage 49 communicates to the pump inlet, while the pump outlet fluidly connects to the axially extending, large cross section bore 68 in drive shaft 30.

Hence when drive shaft 30 is driven, inner gear 57 likewise rotates and effects pumping of oil from sump 44 to axial bore 68. The pressurized oil may flow through the entire length of bore 68 without appreciably dropping in pressure due to the bores large cross section. Since the oil pressure is the same throughout passage 68, it effectively constitutes a source of pressurized oil.

A single radially extending passage 69 in shaft 30 couples oil source 68 to a circumferential annular groove 71 which in turn communicates, via a series of four radially extending passages 72 drilled in rotor 21, to the bottom ends of slots 22. With this construction, the high pressureoil exiting from oil pump 54 is delivered to the slots behind vanes 23 thereby to impel the vanes toward and in sealed engagement with cylindrical wall 12. The magnitude of the oil pressure is set so that during start-up the pressurized oil alone will be sufficient to cause the vanes to move out of their slots and establish fluid-tight connections with the cylindrical wall. Preferably, the pressure level will be just adequate to make the required sealed contact between the vane tips and cylindrical wall, but yet will not cause undue strain on the vanes and needless wear.

Since the oil pump is driven by drive shaft 30, the oil pressure fed to slots 22 would normally tend to increase linearly as the rotor speed increases. In the illustrated compressor, the rate at which the oil pressure increased with RPM is reduced so that the pressure tends to level off to a constant magnitude. This is desirable inasmuch as centrifugal force, which also acts to push each of the vanes against wall 12, increases with RPM. By effectively limiting the extent to which the oil pressure increases from start-up to maximum rotor speed, the total force (ascontributed by both the oil pressure and by centrifugal action) holding each of the vanes against the cylindrical wall may be maintained within a relatively narrow acceptable range and will never be excessive. The upper limit of the range, which prevails at maximum, speed, will be less than that which would cause undue strain, friction and wear on the vanes.

The rate, at which the oil pressure in the bottom of slots 22 would otherwise increase as speed increases, is reduced by decreasing the efficiency of oil pump 54 with RPM. This is achieved, in accordance with the teachings of the aforementioned copending US. Pat. application Ser. No. 160,694, by sizing or dimensioning the passageway extending between oil sump 44 and the pump inlet in order to cause cavitation, the amount of which increases with rotor speed. In other words, during high speed operation oil cannot flow into pump 54 fast enough, thus effecting a vacuum or void in the pump which gives rise to a reduction in the rate of oil pressure increase as speed increases. The faster the operation, the greater will be the vacuum created and the smaller will be the rate of pressure increase.

Automatic centering or balancing of rotor 21 between bearing plates 15 and '16 is accomplished in accordance with the teachings of copending US Pat. application Ser. No. 163,194, filed July 16, 1971 in the name of Alfred 6. Mount, and assigned to the present assignee. Briefly, the rotor is embraced by a pair of hydrostatic bearing cavities the pressure in each of which 6 varies, anytime the rotor shifts off center, in a compensating sense to return the rotor to its home or center position. In the illustrated case the cavities take the form of annular shaped depressions or recesses, denoted by

reference numerals

75 and 76, in rotor faces 26 and 27. Oil flows to cavity 75 from oil passage or source 68 by way of radially extending bore 77 and circumferential annular groove 78 in shaft 30. Similarly, radially extending passage 81 and circumferential groove 82 in shaft 30 communicate oil passage 68 to hydrostatic bearing cavity 76. Passages 77 and 81 have relatively small cross sections so that they will function as flow control orifices. In this way, the oil flow to each of

cavities

75 and 76 experiences a substantial pressure drop in the associated orifice 77, 81.

After reaching cavity 75, the oil then flows radially outward along rotor face 26 and through restrictive clearance 28 to compression chamber 25. By the same token, oil flows out of bearing cavity 76 and radially outward along rotor face 27 and through restrictive clearance 29 to the compression chamber. While no significant pressure drop occurs in

cavities

75 and 76, appreciable pressure drops will be experienced by the oil flow through each of clearances 28 and 29. The magnitude of each pressure drop will be inversely proportional to the size of the clearance. In other words, the closer a rotor face is to its adjacent bearing plate, the greater will be the resistance presented to the oil flow and the greater will be the pressure drop imparted to the oil in flowing through that clearance.

A hydrostatic force is produced in each cavity75, 76 depending on the lubricant pressure in the cavity and the area of the cavity. Orifices 77 and 81 and

cavities

75 and 76 may be dimensioned and shaped so that under normal conditions equal pressure drops occur in the orifices and in the two clearances 28, 29, as a result of which equal pressures and hydrostatic forces are established in the cavities to center rotor 21 between bearing

plates

15 and 16. If the rotor tends to move away from its centered location (due, for example, to some external axial force on shaft 30), the pressure drop increases in one of clearances 28, 29 and at the same time reduces in the other such that the rotor is forced back to its home position..To elucidate, assume that rotor 21 tends to move to the right as viewed in FIG. 1. In that case, clearance 29 becomes smaller while clearance 28 enlarges. Accordingly, an increased pressure drop occurs in clearance 29 and a decreased pressure drop is introduced in clearance 28. Since the pressures are the same where the oil emerges from the two clearances (namely, at the radially outermost portions of the rotor faces) and flows into the compression chamber, increased and decreased pressure drops in clearances 29 and 26 respectively means that the pressure in cavity 76 must increase while that in cavity 75 decreases. Rotor 21 will thus be forced back to its central location whereupon the forces on the rotor will once again be balanced.

The lubricant flowing through clearances 28 and 29 and into compression chamber 25 entrains into the refrigerant gas during compression, as a consequence of which the high pressure gas flowing through valve assembly 36' and into chamber 42 is heavily laden with oil. This entrained oil must be removed from the gas because substantial quantities of oil in the discharge gas reduces the heat transfer in the condenser and evaporator. Also, 'it is muchmoredifficult to'supply a sufficient amount of oil to the compression chamber to attain the necessary sealing between the rotor and chamber surfaces.

Oil separation in the disclosed compressor takes place within shell 46. A passageway formed by

openings

85, 86 and 87 in cylinder 11, rear bearing plate 16 and mounting ring 47, respectively, together with tube 88 communicates chamber 42 to the extreme end of shell 46. Tube 88 extends through an oil separating filter screen 89 comprised of gas permeable material, such as coarse mesh metal fibers as in a scouring pad. The periphery of separator 89 has the same contour as that of the shell so that its edges fit against the internal diameter of the shell. In this way, separator 89 constitutes a partition to define two

different chambers

91 and 92 within shell 46. Element 93 serves as a support bracket for separator 89, while element 94 constitutes a baffle.

In operation of the oil separator, the discharge gas together with the entrained oil flows out of chamber 42 and into chamber 91 through the conduit provided by

bores

85, 86 and 87 and tube 88. At that point the velocity of the gas is greatly reduced as it expands into a much larger volume. In expanding, the gas strikes the end of shell 46 and reverses direction as a consequence of which most of the oil separates on the rear surface of the shell and flows down into sump 44. The gas with the remaining oil, after striking the shell and reversing its flow direction, now heads toward the front of the compressor passing through oil separator 89 where the residual oil coalesces and runs down into reservoir 44. The discharge gas flowing into chamber 92 will thus be oil-free. A discharge oulet 95 mounted on shell 46 permits the gas to flow out of chamber 92. Baffle 94 prevents the turbulent gas from reaching and stirring up oil pool 44 and re-entraining oil back into the gas.

Consideration will now be given to the particular manner in which the compressor is assembled in accordance with the method concept of the invention. Rear bearing plate 16, with oil pump 54 anchored thereto by cap screws 55 and facing downward, is horizontally positioned(as shown in FIG. 3) and held in a jig, not shown. Rotor assembly 20 is then added by inserting the appropriate end of drive shaft 30 into bearing 32 of rear plate 16, after which cylinder 11 is placed around the rotor and on top of plate 16. Precise and critical spacing of cylinder 1 1 with respect to rotor 21 is facilitated by means of a locating pin 101 which is extended through a hole 102, bored in a reduced thickness ear or lug portion 11a of cylinder 11, and into a threaded opening 103 in rear plate 16. The diameter of pin 101 is less than that of hole 102 so that the pin may be passed freely through that hole and then screwed into tapped hole 103. With this arrangement, cylinder 11 may be pivoted in a horizontal plane around a pivot point provided by pin 101. By pivoting cylinder 11 relative to rear plate 16, cylindrical wall 12 may be brought into engagement with the coating 21a of selflubricating material on the rotors cylindrical surface, thereby establishing at contact point 24 a line-to-line sealing fit with zero clearance.

Front plate is now placed over cylinder 11 so that the upper end of shaft 30 (as viewed in FIG. 3) is received by bearing 31. It is then necessary to temporarily hold the bearing plates, cylinder and rotor in assembled relationship. This is made possible by three subassembly bolts 105 each of which may be inserted through a pair of aligned

openings

106 and 107 in plate 15 and cylinder 11 respectively and then screwed into a tapped hole 108 of rear plate 16. Of course, the diameters of

holes

106 and 107 are sufficiently large to permit bolts to be extended therethrough and screwed into rear plate 16 regardless of the relative positions of the cylinder and rear plate.

With bolts 105 drawn tight, casing 10 and rotor assembly 20 will be firmly held together. Those elements must now be secured in such a way that the established zero clearance contact point 24 cannot be altered during subsequent operation in the presence of strong forces, developed during compression, which tend to shift cylinder 1 1 with respect to the bearing plates. This is a key step in the assembling procedure and is carried out by extending dowel pins, with extremely tight fits, between the cylinder and front and rear plates and along axes parallel to the rotors axis. Specifically, two holes 111 are drilled and reamed from the top of (as viewed in FIG. 3) and through front plate 15 and the reduced thickness ear portions 11b of cylinder 11. A third hole 113 is drilled and reamed from the top of and through the reduced thickness portion 11c and rear plate 16. The two dowel pins 115 are then driven into respective ones of holes 111 from the top of the front plate, and the third dowel pin 117 is driven from the top of the cylinder through hole 113. The dowel pins thus fit extremely snub or tight within their associated holes, as a consequence of which absolutely no shifting of the cylinder relative to either one of the bearing plates is possible. Misalignment therefore cannot occur during operation when gases are compressed, and the desired zero clearance at the contact point'will not be disturbed. The assembled casing and rotor are then removed from the jig.

The oil separator is assembled within shell 46 and mounting ring 47 is secured, such as by brazing, to the open end of the shell. Rigidly affixed to mounting ring 47 are six circumferentially arranged main assembly studs 119. Shell 46 and the assembled oil separator may be attached to the casing, rotor assembly and oil pump, while at the same time additional holding forces are provided, by inserting studs 119 through respective ones of the six large, unnumbered openings in each of

plates

15 and 16 and cylinder 11. Each stud 119 is capped by a nut 121, see especially FIG. 1. In this way, not only is the shell and oil separator affixed to the remainder of the compressor, but of more importance the six large main assembly studs 119 and nuts 121 provide additional forces to hold the assembled compressor together and to prevent any axial movement of the compressor parts with respect to each other. Cover plate 43, not shown in FIGS. 3 and 4, may be mounted to cylinder 11 at any convenient step in the assembling procedure.

When the completely assembled compressor is subsequently placed in operation in the location and in the system for which it was designed, for example underneath the hood of an automobile when designed for use in an automotive ainconditioning system, metal expansion caused by high operating temperatures may tend to bind the rotor and cylinder at contact point 24, because of the zero clearance thereat, but this will be precluded by the presence of TEFLON coating 21a which will wear until a desired very close sealing fit, with minimum friction, is established at the contact point. As a consequence, once the compressor functions in its normal environment it automatically wears or laps itself in to a high degree of refinement or accuracy so that the clearance will be optimized to achieve an extremely close fit at the contact point, thereby maintaining the high and low pressure sides of the compression chamber isolated from each other while at the same time introducing minimum friction at the contact point to maximize the compressors capacity, efficiency and reliability.

In the event that the compressor is subjected to unusually severe operating conditions such that metal expansion occurs beyond that normally experienced, an additional amount of coating 21a will wear off thus avoiding binding of the rotor and cylinder and preventing compressor failure that may otherwise result due to complete loss of the contact point clearance. The coating TEF LON thus also furnishes insurance against compressor failure.

The invention provides, therefore, a unique method for assembling a rotary sliding vane compressor in which an optimum contact point clearance is established and maintained in order to minimize both friction'and leakage at that point, thereby to enhance the compressors performance, capacity, efficiency and reliability. Certain. features disclosed herein are described and claimed in a copending divisional application, Ser. No. 3l8,308,filed Dec. 26, 1972.

While a particular embodiment of the invention has been shown and described, modifications may be made, and it is intended in the appended claims to cover all such modifications as may fall within the true spirit and scope of the invention.

l. A method for assembling a rotary sliding vane compressor wherein a slotted rotor, with an external cylindrical surface'of self-lubricating material, has its drive shaft journalled in bearings of parallel spaced front and rear bearing plates torotatably mount the rotor eccentric ally within an internal cylindrical wall of a cylinder positioned between the bearing plates thereby to provide, between the cylindrical surface and wall and between the bearing plates, a crescent-shaped compression chamber having high and low pressure sides sealed from each other, and in which dowel pins extend between the cylinder and front and rear plates to maintain their alignment and to prevent any shifting of those three elements relative to each other, the method comprising the steps of:

rotatably mounting the drive shaft in the bearing of the rear plate;

positioning the cylinder around the rotor and adjacent to the rear plate;

pivoting the cylinder relative to the rear plate to establish a contact point, between the rotors cylindrical surface and the cylinders cylindrical wall, that provides a line-to-line sealing fit with zero clearance;

holding the front and rear plates, cylinder and rotor in assembled relationship; drilling and reaming at least one hole parallel to the rotors axis and through portions of the front plate and the cylinder, and drilling and reaming at least one other hole parallel to the rotors axis and through portions of the cylinder and rear plate; and driving a dowel pin into each of the holes.

2. A method according to claim 1 in which at least one of the holes, through which the dowel pins are driven, is drilled through the front plate and into the cylinder, while at least one other hole is drilled through the cylinder and into the rear plate.

3. A method according to claim 1 in which, prior to the drilling and reaming steps, a plurality of subassembly bolts are extended through the front plate and cylinder and screwed into the rear plate to hold the plates, cylinder and the rotor in assembled relationship.

4. A method according to claim 3 in which, after the dowel pinsare driven into place, a plurality of main assembly studs are extended through the plates and cylinder and are then capped with nuts to provide additional forces to hold the assembled compressor together.

5. A method according to claim 1 in which the cylinder is pivoted relative to the rear plate, to establish the zero clearance contact point between the rotor and cylinder, by means of a locating pin extended through the cylinder and into the rear plate.

6. A method according to claim 1 in which the enumerated steps are performed while the plane of the rear plate is generally horizontally positioned such that the cylinder and front plate must be mounted above and on top of the rear plate.

7. A method according to claim 1 in which the selflubricating material constitutes a coating of TEF LON.

8. A method according to claim 1 in which, when the compressor operates in its intended environment and under normal operating conditions, thermal differentials between the rotor and cylinder may cause expansion of at least one of those elements as a result of which the self-lubricating material on the rotors cylinrical surface wears until a desired very close sealing fit, with minimum friction, is established at the contact point.

Claims

1. A method for assembling a rotary sliding vane compressor wherein a slotted rotor, with an external cylindrical surface of self-lubricating material, has its drive shaft journalled in bearings of parallel spaced front and rear bearing plates to rotatably mount the rotor eccentrically within an internal cylindrical wAll of a cylinder positioned between the bearing plates thereby to provide, between the cylindrical surface and wall and between the bearing plates, a crescent-shaped compression chamber having high and low pressure sides sealed from each other, and in which dowel pins extend between the cylinder and front and rear plates to maintain their alignment and to prevent any shifting of those three elements relative to each other, the method comprising the steps of: rotatably mounting the drive shaft in the bearing of the rear plate; positioning the cylinder around the rotor and adjacent to the rear plate; pivoting the cylinder relative to the rear plate to establish a contact point, between the rotor''s cylindrical surface and the cylinder''s cylindrical wall, that provides a line-to-line sealing fit with zero clearance; holding the front and rear plates, cylinder and rotor in assembled relationship; drilling and reaming at least one hole parallel to the rotor''s axis and through portions of the front plate and the cylinder, and drilling and reaming at least one other hole parallel to the rotor''s axis and through portions of the cylinder and rear plate; and driving a dowel pin into each of the holes.

3. A method according to claim 1 in which, prior to the drilling and reaming steps, a plurality of sub-assembly bolts are extended through the front plate and cylinder and screwed into the rear plate to hold the plates, cylinder and the rotor in assembled relationship.

4. A method according to claim 3 in which, after the dowel pins are driven into place, a plurality of main assembly studs are extended through the plates and cylinder and are then capped with nuts to provide additional forces to hold the assembled compressor together.

7. A method according to claim 1 in which the self-lubricating material constitutes a coating of TEFLON.

8. A method according to claim 1 in which, when the compressor operates in its intended environment and under normal operating conditions, thermal differentials between the rotor and cylinder may cause expansion of at least one of those elements as a result of which the self-lubricating material on the rotor''s cylinrical surface wears until a desired very close sealing fit, with minimum friction, is established at the contact point.