US3584980A - Two-speed compressor - Google Patents

Abstract

A refrigerant compressor having a two-speed compressor motor therein for driving a compression mechanism selectively at a relatively high speed and at a relatively low speed to effect capacity control. For example, a two-winding four-pole motor would, during two-pole operation, rotate at about 3,600 r.p.m., and during four-pole operation at about 1,800 r.p.m. A two-stage pump is provided for cooperating with the crankshaft to provide for adequate lubrication of the crankshaft bearing surfaces during both high-speed and low-speed operation of the compressor motor.

Description

United States Patent 2,217,460 10/1940 Trassl 318/224 2,575,716 11/1951 Kilgore 318/224 3,034,030 5/1962 Rosenschold et al. 318/224 X 2,243,615 5/1941 Werner etal. .0 62/215 2,274,943 3/1942 Touborg 230/206 Primary Examiner-Robert M. Walker Attorney-Molinare, Allegretti, Newitt & Witcoff ABSTRACT: A refrigerant compressor having a two-speed compressor motor therein for driving a compression mechanism selectively at a relatively high speed and at a relatively low speed to effect capacity control. For example, a two-winding four-pole motor would, during two-pole operation, rotate at about 3,600 rpm, and during four-pole operation at about 1,800 rpm. A two-stage pump is provided for cooperating with the crankshaft to provide for adequate lubrication of the crankshaft bearing surfaces during both highspeed and low-speed operation of the compressor motor.

TWO-SPEED COMPRESSOR BACKGROUND OF THE INVENTION This invention relates to a hermetic refrigerant compressor utilizing a motor operable at different predetermined increments for driving the compression mechanism so as to effect capacity control. In another aspect, this invention relates to a hermetic refrigerant compressor having a motor operable at different fixed increments, for example, full-speed and halfspeed, with a two-stage pump associated with the crankshaft for assuring adequate lubrication at both speeds of operation.

Refrigerant compressors have generally been designed to operate at a relatively constant speed. In use, the load on the refrigeration system in which the compressor is utilized may vary, resulting in several off-on cycles as well as inefficient operation of the compressor unless the capacity of the compressor can be varied to comply with system variation. One method of effecting capacity control has been to bypass discharge gases from the discharge line directly to the suction line or suction side of the refrigeration system--a highly inefficient method. Still another arrangement requires the use of capacity control valving and solenoids within or in association with the compressor in order to vent the discharge of cylinders to the suction manifold. This method is more efficient than the discharge gas bypass arrangement, but still less efficient than desired.

An object of the present invention is to provide an improved refrigerant compressor employing a compressor motor operable at different fixed increments of speed for effecting capacity control.

Another object of this invention is to provide an improved hermetic compressor having a drive motor operable at different fixed increments of speed, such compressor including multistage pump means to assure adequate lubrication of the crankshaft bearing surfaces during all operating speeds. Other objects and advantages of the present invention will become more apparent hereinafter.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing illustrates a preferred embodiment of the invention in which like numerals refer to like elements and in which:

FIG. 1 is a side elevational view, partially in section and with parts broken away, of a hermetic refrigerant compressor embodying the present invention;

FIG. 2 is an enlarged cross-sectional view of the two-stage pump mechanism of the present invention;

FIG. 3 is a bottom view of the two-stage pump mechanism of FIG. 2; and

FIG. 4 is a cross-sectional view of the pump impeller.

DETAILED DESCRIPTION OF THE INVENTION Referring'to FIG. I, there is illustrated'a compressor embodying the present invention. The compressor comprises a gastight, hermetically enclosed outer casing or housing including anupper shell 12 and alower shell 14 integrally joined to one another, as, for example, by welding. To the bottom of the exterior surface of thelower shell 14 are welded a plurality oflegs 16 by means of which legs the compressor may be supported in an upright position within a condensing unit or an air-conditioning unit.

Supported within the outer casing ofthecompressor 10 is acompression mechanism 18 which includes a compressor block having acrankcase portion 20 and amotor flange portion 22. An annular sleeve 24 made from sheet metal surrounds thecrankcase portion 20 of the compressor block and cooperates therewith to define an annulardischarge gas cavity 23 in the compression mechanism. Aheat shield 26 is disposed about the annular sleeve in spaced relationship thereto. Y

The annular sleeve 24 includes an out-turnedupper flange 28. Secured to thelower shell 14 of the outer casing is anannular flange member 29. Spring means 32 cooperate between theflange 28 andflange member 29 for resiliently supporting thecompression mechanism 18 within the outer casing ofcompressor 10.

Provided within the compressor block are a plurality of radially orientedcylinders 30. Though a four-cylinder compressor is illustrated, it will be understood that the present invention may be used in a hermetic refrigerant compressor having other cylinder configurations. Cylinder sleeve orliners 33 are provided in each of the cylinders and a piston 34 is slidably mounted for reciprocation within each of thecylinder liners 33. Each piston 34 has mounted therein awrist pin 36 upon which is journaled one end of a connectingrod 38. The other end of each connectingrod 38 is affixed -to theeccentric portion 40 of drive shaft orcrankshaft 42.

Provided at the end of eachcylinder 30 for closing the end of each cylinder cavity is a valve assembly 60. The valve assemblies 60 each comprise a discharge valve unit and a suction valve unit operable in a known manner. Each valve assembly 60 is held in place in the end of acylinder 30 by a cylinder head orcap 62. A Belleville spring 64 and aretaining ring 66 cooperate with thecylinder head 62 to maintain the head in position closing the end of the cylinder. Theannular space 23 provided within the compression mechanism between the compressor block and the sleeve 24 communicates each of the cylinders and receives the discharge gases from the cylinders and conveys them to thedischarge line 72.

Thedrive shaft 42 is disposed in an upright position within thecompression mechanism 18 and is connected at its upper end to therotor 44 of theelectric drive motor 46. The motor includes astator 48 which is supported within themotor flange portion 22 of the compressor block and therotor 44 which is inductively connected to thestator 48.

Enclosing the top of themotor 46 is anend cap 50 which is suitably connected to top of themotor flange portion 22 of the compressor block.

Drive shaft 42 is journaled at its lower end within alower bearing 52 mounted in lower bearinghead 54. Thelower bearing head 54 is maintained in position by a suitable wedge-lock spring or retainingring 56 seated within an annular groove in thelower crankcase portion 20 of the compressor block. Intermediate its ends thedrive shaft 42 is journaled within the spacedbearings 57 and 58 in the hub portion or partition porpartment defined between the outer casing and the compression mechanism below theflange 29. The gas passes from the first compartment into a second compartment or annular space defined between theflanges 29 and 28 and then into a third compartment defined between the outer casing and the top of thecompression mechanism 18. From the third compartment, the suction gas passes through the opening 51 in the top of theend cap 50 over theelectric motor 46 for cooling same and then through theopenings 76 in the compressor block into thecylinders 30. The gases are compressed within the cylinders and forced through the valve assemblies 60 into the annulardischarge gas cavity 23. From the annulardischarge gas cavity 23, the compressed gas passes through thedischarge line 72 to the condenser of the refrigeration system in which the compressor is utilized.

A plurality ofterminals 78 are provided in the top of theupper shell 12 in order to conduct electric current from a suitable source to theelectric motor 46 and to provide for connection of suitable motor protection while preserving the hermetic nature of the compressor.

In larger size refrigerant compressor, for example, on the order of l0-ton capacity and four cylinders, it is sometimes difficult to employ mechanical unloaders because of balance and control problems. A unique solution to the problem of capacity control in such compressors is to provide a multipole electric motor operable at different fixed increments of speed by which the capacity of the refrigeration system can be varied. For example, a four-pole two-winding electric motor can be utilized to provide full capacity during two-pole operation and one-half capacity during four-pole operation. The characteristics of one form of motor embodying the present invention would be as follows:

HIGH SPEED (2 P018) Minimum Minimum motor Torque, speed efficiency, Remarks 1b./t Voltage r.p.m. percent Maximum load 31. 25 187 3, 235 79. 31. 25 240 3, 420 88 31. 25 264 3, 450 88 Rated load 25 187 3, 340 84 25 240 3, 460 90 25 264 3, 480 90 Minimum flow rate 19. 5 187 3, 420 87. 5 19. 5 240 3, 490 91 19. 5 264 3, 510 90. 5

LOW SPEED (4 Pole) Minimum Minimum motor Torque, speed etficiency, Remarks 1b.llt. Voltage r.p.m. percentMaximum load 26. 5 187 1, 620 79. 5 26.5 240 1, 710 88 26. 5 264 1, 725 88 Rated load 25 187 1, 670 84 25 240 1, 730 90 25 264 1, 740 90 Minimum flow rate 4 16 187 1, 710 87. 5 16 240 1, 745 91 16 264 1, 750 90. 5

it is seen that in such motor the minimum speed during high-speed or two-pole operation would be on the order of 3,2353,5 rpm. At half-speed or four-pole operation the motor speed would be on the order of 1,620] ,750 rpm.

It has been found that by taking advantage of total refrigeration system characteristics and reducing the maximum load requirement during low-speed operation, minimum required efficiencies of not less than about 80 percent can be maintained during both high-speed and low-speed operation with a less expensive motor design than, say, a constant torque twospeed motor.

in use, the known pump means of the prior compressors would function satisfactorily in the novel compressors of this invention during high-speed operation, but provided inadequate lubrication during low-speed operation. Thehermetic compressor 10 of the present invention has been provided with unique two-stage pump means 80 for assuring adequate lubrication of the crankshaft bearing surfaces during both high-speed and low-speed operation. The upright drive shaft orcrankshaft 42 is provided with a longitudinally disposedpump passage 81 which has at its upper end radially disposedpassages 82 and 84 for lubricating the bearing surfaces between thecrankshaft 42 andbearings 57 and 58. The

'passages 83 and 85 communicate with the upper end of thepump passage 81 to vent refrigerant from the pump passage at startup of the compressor. Lubricant is supplied to thelower bearing 52 through the radially disposedpassage 86.

Disposed in an opening in the bottom of thelower bearing head 54 and fixedly secured thereto is athrust plate 90.Openings 91 in thethrust plate 90 provide inlet opening means for communicating the rotating elements of two-stage pump 80 with lubricant in the sump defined between the compression mechanism and thelower shell 14. Lubricant passes from the openings 9lthrough aninlet opening 92in'the pump impeller 93 into radially disposed or transversely disposedpassage 94 in thepump impeller 93. Thepassage 94 provides for the first-stage pressurization of the ingested lubricant. Lubricant is discharged frompassage 94 into theannular space 96 between therotating pump impeller 93 and the inner wall of thelower bearing head 54. Theimpeller 93 is connected to thedrive shaft 42 by suitable fastening means, for example, machine screws 98. The lubricant passes from theannular space 96 through atransverse passage 100 in the fixedthrust plate 90 and then upwardly through acentral passage 102 in thepump impeller 93 into arecess 103 in the bottom of the drive shaft. Fromrecess 103, the lubricant passes into the radially disposedpassage 86 and then into thepump passage 81 for transfer to the crankshaft bearing surfaces. A secondstage pressurizing of the lubricant is effected in the passage in operation it has been found that the lubricant will be supplied to the radially disposedoutlets 86, 84 and 82 during both high-speed and low-speed operation of the compressor under desired pressure. The use of a conventional single-stage pump was found inadequate to supply desired lubricant pressure during low-speed operation.Screen 110 is affixed to the lower bearing head to prevent impurities in the sump from entering the two-stage pump 80.

Referring to FIGS. 2, 3 and 4 there is better illustrated the details of the two-stage pump of the present invention. Thethrust plate 90 has fouropenings 91 therein which serve as inlet openings for communicating the two-stage pump with the oil in the sump. A continuousannular groove 112 is provided in the top of thethrust plate 90 for providing continuous feed of lubricant to thepump impeller 93. Provided in thethrust plate 90 in a plane generally transverse or at right angles to the axes of the fouropenings 91 is abore 100. Thepump impeller 93 of the two-stage pump rests upon the thrust plate during normal operation. Thepump impeller 93 is fixed to the drive shaft orcrankshaft 42 for rotation therewith by means of the fastening means 98. Lubricant will be ingested through thepassages 91 in thethrust plate 90, into theannular groove 112 in the top of the thrust plate, through the inlet opening 92 in thepump impeller 93 into the radially disposedpassage 94 of thepump impeller 93 where the first-stage pressurization occurs. The lubricant will then pass from the radially disposedpassage 94 through passage means defined in part byannular chamber 96 between theimpeller 93, washer or thrustplate 90 andlower bearing head 54, thebore 100 in thethrust plate 90 and the axially alignedupright bore 102 in theimpeller 93 for passage through the second-stagepressurized passage 86 into the upright axially offsetpassage 81. The two-stage pump of the present invention functions effectively during both high-speed and low-speed operation of the compressor motor to provide adequate lubricant pressurization during all modes of operation. A minimum number of components are required to be added to the compressor mechanism while maintaining the desired lubrication.

There has been provided by the present invention a hermetic compressor utilizing a motor for driving the compression mechanism within the compressor selectively at different fixed increments of speed was to provide for capacity control without auxiliary components such as capacity control valving and solenoids. In one presently preferred form, the motor is a two-winding four-pole motor, with two-pole operation providing the higher speed (about 3600 rpm.) and four-pole operation providing the lower speed (about 1,800 (r.p.m.). The hermetic compressor is further provided with a novel two-stage pump means which will maintain desired pressurized lubrication during both high-speed and low-speed operation of the compressor motor.

While there has been shown and described a presently preferred embodiment of the invention, it will be obvious that otherembodiments will be apparent to those skilled in the art. lt is, therefore, intended that the invention be limited only within the scope of the appended claims.

We claim:

1. in a refrigerant compressor including compression mechanism within a sealed outer casing, said compression mechanism including an upright crankshaft means having at least one longitudinally extending pump passage thereinoffset from the rotational axis of the crankshaft means for supplying lubricant to surfaces to be lubricated. motor means within the outer casing for actuating the compression mechanism, and a lubricant sump in the compressor. the improvement characterized by said motor means comprising a four-pole two-winding drive motor for driving the compression mechanism at a first high speed and a second lower speed to control capacity of the compressor, two-pole operation providing said high speed and four-pole operation providing said lower speed, and a two-stage pump mechanism operatively driven by the drive motor for assuring adequate lubrication whether the drive motor is operating at said high speed or said lower speed, said pump mechanism including means defining first inlet opening means offset from the rotational axis of the crankshaft means for ingesting lubricant from the sump, a first-stage pressurizing opening transversely disposed in said crankshaft means, said first-stage pressurizing opening communicating with said first inlet opening means, a second-stage pressurizing opening transversely disposed in said crankshaft means, passage means communicating with said first-stage pressurizing opening with said second-stage pressurizing opening, said second-stage pressurizing opening also communicating with said pump passage, the two-stage pump mechanism assuring adequate lubrication of said surfaces to be lubricated at said lower speed operation of said drive motor.

2. A refrigerant compressor as in claim 1 wherein the means defining first inlet opening means comprises a thrust washer fixed in said compression mechanism below the crankshaft means and having at least one axially offset inlet opening therein, said thrust plate having a transversely disposed bore separate from said inlet opening, said transversely disposed bore defining a portion of said passage means.

3. A refrigerant compressor as in claim 2 wherein the crankshaft means includes crankshaft and a pump impeller connected thereto, said first-stage pressurizing opening being in said pump impeller.

4. A refrigerant compressor as in claim 3 wherein said passage means includes an axial bore in said crankshaft which communicates at one end with an axial bore in said thrust washer that in turn communicates with the tranversely disposed bore in the thrust washer, whereby lubricant ingested through said inlet opening passes through the first-stage pressurizing opening, passage means, and second-stage pressurizing opening to the pump passage.

5. A refrigerant compressor as in claim 3 wherein the passage means includes an annular chamber defined between the thrust washer, pump impeller and compression mechanism, said annular chamber communicating with said first-stage pressurizing opening and said transversely disposed bore in said thrust washer.

6. A refrigerant compressor as in claim 5 wherein the thrust washer has a continuous annular groove in the top surface thereof communicating with the inlet opening means, the top surface of the thrust washer abutting the bottom surface of the pump impeller, said annular groove providing continuous feed of lubricant from the inlet opening means to said first-stage pressurizing opening in the pump impeller.

Claims (6)

1. In a refrigerant compressor including compression mechanism within a sealed outer casing, said compression mechanism including an upright crankshaft means having at least one longitudinally extending pump passage therein offset from the rotational axis of the crankshaft means for supplying lubricant to surfaces to be lubricated, motor means within the outer cAsing for actuating the compression mechanism, and a lubricant sump in the compressor, the improvement characterized by said motor means comprising a four-pole two-winding drive motor for driving the compression mechanism at a first high speed and a second lower speed to control capacity of the compressor, two-pole operation providing said high speed and four-pole operation providing said lower speed, and a two-stage pump mechanism operatively driven by the drive motor for assuring adequate lubrication whether the drive motor is operating at said high speed or said lower speed, said pump mechanism including means defining first inlet opening means offset from the rotational axis of the crankshaft means for ingesting lubricant from the sump, a first-stage pressurizing opening transversely disposed in said crankshaft means, said first-stage pressurizing opening communicating with said first inlet opening means, a second-stage pressurizing opening transversely disposed in said crankshaft means, passage means communicating with said first-stage pressurizing opening with said second-stage pressurizing opening, said second-stage pressurizing opening also communicating with said pump passage, the two-stage pump mechanism assuring adequate lubrication of said surfaces to be lubricated at said lower speed operation of said drive motor.

2. A refrigerant compressor as in claim 1 wherein the means defining first inlet opening means comprises a thrust washer fixed in said compression mechanism below the crankshaft means and having at least one axially offset inlet opening therein, said thrust plate having a transversely disposed bore separate from said inlet opening, said transversely disposed bore defining a portion of said passage means.

3. A refrigerant compressor as in claim 2 wherein the crankshaft means includes crankshaft and a pump impeller connected thereto, said first-stage pressurizing opening being in said pump impeller.

4. A refrigerant compressor as in claim 3 wherein said passage means includes an axial bore in said crankshaft which communicates at one end with an axial bore in said thrust washer that in turn communicates with the tranversely disposed bore in the thrust washer, whereby lubricant ingested through said inlet opening passes through the first-stage pressurizing opening, passage means, and second-stage pressurizing opening to the pump passage.

5. A refrigerant compressor as in claim 3 wherein the passage means includes an annular chamber defined between the thrust washer, pump impeller and compression mechanism, said annular chamber communicating with said first-stage pressurizing opening and said transversely disposed bore in said thrust washer.

6. A refrigerant compressor as in claim 5 wherein the thrust washer has a continuous annular groove in the top surface thereof communicating with the inlet opening means, the top surface of the thrust washer abutting the bottom surface of the pump impeller, said annular groove providing continuous feed of lubricant from the inlet opening means to said first-stage pressurizing opening in the pump impeller.

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