CA1069864A - Variable displacement compressor - Google Patents

Abstract

ABSTRACT

An axial piston, variable displacement, wobble plate gas or vapor compressor containing improvements in the capacity control system and in the drive plate and wobble plate mounting arrangements. A cam mechanism is driven by the drive shaft of the compressor, and at least one axially extending flange member is connected to the drive shaft. A lug is associated with a cam mechanism having a portion in spaced, juxtaposed relation with a surface on the flange, and a pivot link is attached at one end thereof to the flange and at the other end thereof to the lug. The lug is spaced from the axis of the drive shaft so that the cam mechanism is pivoted at a point not coincident with the drive shaft axis. No drive connection is provided at the drive shaft axis between the cam mechanism and the drive shaft, the link being positioned between the flange and the lug means so that the torque is transmitted from the drive shaft to the cam mechanism without producing a substantial bending moment on the pivot link.

Description

The present invention is directed to improvemen-ts in wobble plate compressors, especially those adapted for use in air conditioning apparatus, particularly for auto-motive applications.
This is a division of copending Canadian Patent Application Serial number 269,903, filed on January 18, 1977.
A principal object of the invention is to provide a reliable variable capacity unit at a reasonable cost. ~-One aspect o~ this objective has to do with an improved ~-wobble plate and drive plate mount which permits torque loads to be transmitted independently of the pivot linkage which connects the driving member to the drive plate.
Another aspect relates to the mechanism which anchors the wobble plate and still another to the balancing arrangement. ~`~
U~So Patent 3,861,829 (Roberts et al~, assigned to the same assignee as the present invention, describes ~ , .
a wobble plate compressor using controlled, under-piston gas pressure to vary the inclination of the wobble plate, which is supported on a universal joint. The present ~ ;~
invention is an improvement on Roberts et al in that the drive mechanism is designed to reduce loads on certain - ;
critical elements, such as the pivot linkage, and to simplify the unit, making it more compact and easier to ;~ assemble.
U.S~ Patent 3,552,886 (Olsen) shows a spherical bearing or hinge ball supporting the drive plate/wobble plate assembly.
U.S. Patents 2,980,025 (Wahlmark) and 2,964,Z34 (Loomis) both show the concept of pivoting the wobble plate assembly to a point spaced from the drive ax:is to maintain essentially constant clearance volume.
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Ac~ording to the present invention, there is provided a compressor includin~ means defining a plurality of gas working spaces each having a piston cooperating with suction and discharge ports to compress a fluid therein, a drive shaft, a cam mechanism driven by the drive shaft and a wobble plate driven by the cam mechanism in a nutating path about the drive shaft axis. Means operably connect between the wobble plate and the individual pistons to impart reciprocating drive to the pistons, the length of stroke being a function of the angle at which the wobble plate is supported relative to the drive axis~ Means is ~-connected to the drive shaft and includes at least one axially extending flange member. Lug means is associated with the cam mechanism and has a poxtion in spaced, juxt-aposed relation with a surface on the flange A pivot ` link is attached at one end thereof to the flange and at the other end thereof to the lug means. The lug means is spaced from the axis of the drive shaft so that the cam mechanism i5 pivoted at a point not coincident with the -drive shaft axis, there being no drive connection at the drive shaft axis between the cam mechanism and the drive shaft, the link being positioned between the flange and the lug means so that the torque is transmitted from the drive shaft to the cam mechanism without producing a substantial bending moment on the pivot link.
In the accompanying drawings:
` FIGURE 1 is an elevation view, partly in cross-`~ section, of a preferred embodiment of the present invention;
` FIGURE 2 is a rear elevation view, with portions of the head and valve plate broken away;
FIGURE 3 is a view ~ken alony the plane of line 3-3 of FIG~E 1 with the control valve removed;
FI~ 4 is a view ~en along the plane of line 4-4 . . .
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of FIGURE ].;

FIGURE S is a cross-section view taken along the plane of line 5-5 of FIGUR~ l;
FTGURE 6 is a cross-section view ~aken ~long the plane of line 6-6 of FIGURE 2;
FIGURE 7 is a cross-section view taken along the plane of line 7-7 of FIGURE 2;
FIGURE 8 is a cross-section view taken along the plane of line 8-8 of FIGURE l;
FIGURE 9 is a plan view of the underside of the head assembly; .
FIGURE lO is a cross-section view taken along the plane of line 10-10 of FIGURE 9;
FIGURE 11 is a partial cross-section view taken ~ :
along the plane of line ll-].l of FIGURE 9;
FIGURE 12 is a partial cross-section view taken along the plane of lin~ l2-l2 of FIGURE 9;

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I~IGURE 13 is a de~ailed view o~ the suction and discharge valve as~embly as vie~7ed from und~rnea~h the valve plate;
FIGURE 14 is a plan view o~ the valve plate;
FIGURE 15 is a cross-section view o~ the valve plate taken along the plane of line 15-15 of FIGUR~ 14;
FIGURE 16 is an elevation view o~ the cylinder block as viewed away from the valve plate;
FIGURE 17 is a cross section view taken along the plane of line 17-17 of FIGURE 16;
FIGURE 18 is a plan view of the drive plate assembly;
FIGURE 19 is a cross-section view of the drive plate assembly along the plane of line i9~19 of FIGURE 18; -~
.
FIGURE 20 is an elevation ~iew of the hinge ball;
- FI~7URE 21 is a perspective vie~i o~ the drive pla~e .. . . ..
assembly showing the hinge ball in different ~ositions prior to assembly; and FIGURE 22 is a detailed cross-section view of the lubricant flow interrupter assembly.
For pur~oses of this description, the compressor may be.regarded as being organized in a plurality of sub-assemblies. The mechanical Parts are all disposed within a housing A which is generally cylindrical in cro.ss section `~
and is provided with continuous side walls and opposed open ends into which the working parts are received. The other major subassemblies include a cylinder block B, a wobble --plate C, ~ drive plate D, a head assembly l~, the ~i.stons and associated conn~ctin~ rods ~, cayacity control unit ~, d~ive 0 / 4 ?. 7 1- P,~

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shafL ~ssembly ~l antl v~lve p:laL~ J.
A~ bes~ sho~n in ~IGI]RE 1, which is a ~r~ss section view, the cylind~r block B i~ provided with a ~lurality o spaced cylin~ers 10. The axes o~ the cylinders a~e parallel to the drive sha~t axis, but it is understood that it is possible to arrange such cylinders alon~ non~arallel a~es without departing from the principles of the invention~
Also, while five cylinders are shown, the actual number is a matter o choice in des~gn, although there is obviously some practical upper limit and the oper~tion of the design shown requires a~ least three cylinders since the control of the wobble plate position depend~ on the balancing forces resulting from the geometry of the wobble plate pivot point with respect to the drive axis.
The cylinder block B also includes a centrally located axial bore 12 (as shown at the left hand side of ..
.. . . .. .
FIGURE 1) forming a part of the lubrican~ distribu~ion system which is described in more de~ail below. There is also a counterbore 14 which receives the rear radial beari.ng 16, shown as the needle or roller bearing tyPe. Radial bearing 16 suppor~s the rear end of drive shaft 18. The terms "front", "rear" etc. are of course arbitrary; but in this description the front of the compressor is the right~
hand portion of FIGURE 1 and the rear of the compressor is the left-hand portion of FIGURE 1.
; The drive shaft 18 is supported at its front end by a fron~ radial bearing assembly 20. The housin~ A is provided with a central axial bore 22 ~7hich receiv~s the front radial bearin~ 20 and a co-mterbore 7.4 formi.n~ a ~ .
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CclVi~y 25 .~dcll)ted to accommoclate a seal assembly ~6 arld the small ~-hrust ~earin~ 28. The rl~sht hand end (as viewed in FIGllRE 1) of the housing is closed by a seal plat:e 30 which is secured by a plurality of machine screws 31 threaded into the annular sect;on 32 surroundlng cavity 2S at ~lle right hand end of the housing.
The drive shaft 18 has a central axial passage 34 which interconnects with a plurality of radial passages 35, 36 and 37 used to supply lubricating oil to the drive ~late D, front radial bearing 20, the thrust bearings and other critical parts. There is also an inclined passage 38 through the right hand end of the housing which provides a path for lubricating oil and`fluid communication between the interior - of the h~usîng and the seal cavity 25, said interior being identified by reference numeral 40 and sometimes referre~ to herein as the "crankcase'i. It should be noted that the ~`
crankcase is completely sealed except for the clearances be~ween the pistons and the cylinder walls and the passages for oil flow through the drive shaft to the bearings etc.
The seal assembly 26 at the right hand end of the drive shaft is fluid tight and designed to increase sealing as the -pressure rises within the crankcase, as communicated to the seal and bearing cavity through pas~age 33. Sealing contact is made between the rotating seal element 46 and the inside surface of the seal plate 30.
The drive shaft is driven by means o~ a pulley 48 having a generally bell sha~ed configuration and provided . .
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~;S`8~4 wlth V-belt cll~a~ing flaTI~e.s 50. 'I'he pulle~ i.s keye(t a~ 52 to the tapered section 53 of thc drive shaf~ 18 and held in place by a machine screw 54 at the end thereo~. Although the compressor i~s described as bein~, driven by a pulley, because one principal applica~ion for the compressor is in an autotnotive air conditioning sys~em driven by the accessory drive belt, it should be understood that any suitable drive means may be provided.
The piston and connecting rod assembly F includes pistons 56 connected to the wobble pla~e C by means,o connecting rods 60, each having ball shaped enlarged sections 61, 62 at opposite ends thereof which may be captured in sockets formed respectively in the pistons and wobble plate.
As viewed in FIGURE 1, the left hand end 61 o~ each connect-ing rod is secured to the underside of the pistons and received ~7ithin a complementary shaped socket 64 formed in a ..
thickened portio-n 65 of the ~iston 56 at the center thereof.
The o~posite ball shaped end 62 o the connecting rod is received within a complementary socket 66 formed,in the wobble plate C. This arrangement allows a number of degrees of freedom, in all directions, between the respective ends of the connecting rods both at the piston and at the wobble 'plate.
The wobble plate C is ro~atably supported on the drive plate assembly D (see FIGURFS 18-21) which includes an annular ~lange 67 extending radially from the drive shaft axis and an axial hub -sec~ion 68 wlli.ch is hollow and form2d with an internal spherical sur~ace 70 to receive the main ~ ' .

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~obble plate and drive plate bcaring m~m~er, r~.E~rred to herein as hinge ball 72. ~linge ball 72 is formed wi.th a bore 69 for drive shaft 18, oppose~l spherical surfaces 71 and opposed cylindrical surfaces 73 to al].ow insertion into t~le hub section 6~ as shown in FIGURE 21.
The wobble plate C is mounted for relative rotary movement with respect to the rotaT~ing drive plate assembly D
by means of three sets of bearings: the rear wobble ~late thrust bearing i4; the front wobble plate thrust bearing 76;
and the radial wobble plate bearing 78. The i~ner race of ~:
the radial bearing 78 is mounted on the OD 80 of the axia~ .
hub section 68 of the drive plate assembly so that the drive plate, which acts as a cam mechanism, can rotate freely with :~
respecT: to the wobble plate. In order to balance ~he assembly under d~namic conditions, a balance weight ring 81 of sub-stantial mass is secured to the nose o~ the hub section 68 by means of retaining ring 85. The wobble pla-te C is restrained against rotative movemenT by means o~ anchorin~ ball element ~.
82 and cooperating slippers or pads 83. When the compressor ~;~
is in stroke, the anchoring ball slides back and forth within a U-shaped track 84 attached to the lower portion of -the cylinder block B in slots 86 and 87 ~see FIGURES 3 and 5).
The drive shaft assembly including plate H, which is secured to and rotates ~7ith the drive shaft, is forTned from two stampings, the first of which (3ho~m at 90) is s~aced from surface 91 on the i.nsi~e of the housing by mean~s of a l~rge thru~t bearing asscTnbly 92. A second section 9~, which is inclined with rcspect to ~he (Irive shait (at the same angle a5 the ma~i.mum nclina~;on pro.i~ecl 07l~71-~tJL

for maximum stroke operation o~ the compressor) is attached to the drive shaft 18, such as by welding, and also where i~
is in contact with the first sta~ping 90. Joining the two sta~pings at the toP are a pair of spaced apart, rearwardly extending flanges 96, 98 (see FIGURE 8) which are adapted to support links 100, 102 connecting the drive pla~e assembly D
to the drive shaft assembly H.
The i~proved mechanism for mounting the drive plate D for pivotal movement with respect to the drive axis and the link plate assembly H constitutes an important aspect of the present invention. This arrangement virtually eliminates all torque applied through the links 100 and 102 which, because o~ their relatively small size, are not suitable as drive transmission elements. As best shown in FIGURES 4 and B, the flanges 96, 98 are joined to the front end of links 100, 102 by means of a pin 104, while the opposite end of each link is pivotally secured to a large lug 106 projecting from ~he front of the drive plate D by means of a pin 110. Since the links 100, 102 each have opposite faces in engagement with both the lug 106 on the drive plate and flanges 96, 98 on the link plate assembly, the torque is transmitted from flanges 96, 98 to the lu~ 106 on the drive plate without producing a bending moment on the links 100, 102.
Although forming no part of the invention claimed herein, another advantage of the compressor described herein is the fact that an oil pump i5 not required. Lubrication is accomplished by using discharge gas pressure as the driving force to circulate oil to the various bearings and seal assemblies which require a certain amount o~ lubrication for efficient operation. Oil is circulated through a hollow :

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dowel 112 received wi~hin central bore 12 in the cylinder block B. Dowel 112 extends throuyh khe valve plate J and serves to accurately locate the valve plate and head, as well as the various gaskets, with respect to the cylinder block. From the passage 114 in dowel 112, the oil flows through an oil interrupter assembly 116 which includes a stationary section 118 and a rotating section 120. As best shown in FIGURE 22, rotation of element 120 intermittently connects passage 122 in the s~ationary section with passage 124 in the rotating section, thus allowing flow of oil during the time the two passages are in registration with each other. This system controls the flow of the oil as it passes through the axial bore 34 through drive shaft 18 and then through radial passages 35, 36, and 37 to the front bearings and seal assembly. Without the interrupter, the `~;
oil return passage would permit an uncontrolled flow of discharge gas into the crankcase which would drive the . ~:
wobble plate to the m~imum stroke position and would make effective control of the displacernent impossible to achieve.
As will be described in more detail below, the ~-capacity control system G includes a valve member which ;-controls the pressure maintained within the crankcase 40 and therefore the angle of inclination of the wobble plate and drive plate assemblies. This aspect of the compressor of the present invention is disclosed and is also claimed in above-identified parent application Serial number 269,903.
The refrigerant vapor will flow by the piston rings to main~ain a certain amount of pressure within the crank case. High crankcase pressure, acting on the underside of the pistons, by virture of the articulated plvot point beinc3 spaced from the drive shaft axis, causes _ 9 _ .

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the drive plate c~nd wobble plate to move toward the vertical position, decreasing stroke and capacity. Conversely, reduction in crankcase pressure will cause the wobble plate and drive plate assemblies to move toward a more in~lined position, increasing stroke and capacity.
The wobble plate is never allowed to move com-pletely to a zero stroke position; otherwise there would be no vapor admitted to the gas working spaces and therefore nothing for the pistons to react against in order to ~orce the wobble ~late to an inclined position. To insure the minimum stroke necessary a stop pin 130 i5 located in th~
drive plate 68. The stop pin will engage the drive shaft at a point such that a minimum of 1-2% of stroke will always be maintained.
As best shown in FIGURE 9 and 10, which are, respectively, a bottom plan view looking at the underside of the head E and a cross-section view, the perimeter thereof is bounded by a downwardly extending skirt portion 140 which is adapted to seat against a similarly shaped gas~et (not shown) between the head and the valve plate J. Lugs 1~1, for attaching the head to the housing, extend from the edge thereof. Disposed inwardly from the skirt is a generally pentagonally shaped ri.b 142 having a series of lugs 144 thereon, through which the head bolts 146 extend, a V-shaped section 143 which forms a collectvr or sump for oil separated from the discharge gas, and a central boss 148 for receiving the hollow dowel 112 (FIGURE 1). It is also provided with a generally circular boss 150 which bridges one of the ski.rt , .

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side walls and rib 142 to provide a housing for th~ solen~i.d valve assembly 220, which is seated in bore 152, It should be noted at this point tha~ the inner rib 142 separates the discharge or high pressure region 145 from the suction or low pressure re~ion 147. Suction gas is admitted through port 156 into the outer region between the peripheral wall 140 and the interior wall 142, while discharge gas flows outwardly through discharge gas port 158 located at the upper left hand side o the interior section bounded by rib 142. 5ee also FIGURES 2, 6 and 7. A ~ort 159 for a standard pressure relief valve is located in the high pressure region.
On the outside surface of the head are the exterior connections for the suction and discharge lines. As shown in FIGURES 2 and 6~ a mounting plate 153 is bolted to the head at 154.
Projecting from the mounting plate are threaded connector fittings 149, 151 for the suction and discharge gas lines respectively. The high pressure relief valve 157 ~FIGURE 7) extends through port 159 into the high pressure plenum. It is well understood, if the compressor is used in an air-conditioning or refrigeration application the discharge line would connect to a condenser, an expansion device, an evaporator and the suction line, in series flow relation.
The head assembly has a series of inwardly project-ing lugs 160 which support an oil separator screen 162 (see FIGURES 1, 6 and 7) constructed o~ a mesh or screen-type material, between the valve plate 114 and the head in the high pressure region, A substantial portion of the lubri-cating oil coal~sces on the scr~en as it flows into the discharge 7,0ne l~ounde~l by rib 142 and drains by gravi ty into ~ 1 1 a pock~t shaped area 164 de~ined by wall section 143, which, although shown in FIGURE 9 at the four o'clock position, will actually be the lowest point within the interior of rib 142 when the compressor is oriented properly. As best shown in FIGURE 12, which is a cross-section view taken along the plane of line 12-12 of FIGURE 9, there is a drilled hole 166 communicating with the lower portion o~ the oil collecting pocket 164 and there is a shallow groove 168 (see also FIGURE 11) which ;s formed in a rib 172 extending from the pocket 164 to the boss 148 through which the hollow dowel extends. The groove 168 provides a channel for lubricating oil running from the pocket 164 to a crescent shaped relief section 174 cut in the interior waIl of the central boss ~ -148. From there it flows into a small cham~er 176 ~IGURE 1) adjacent the dowel 112 and then through the bore 114 to the space 180 between the dowel and the stationary flow interrupter element 118. The latter is fixed within a counterbore and urged axially to the right by means of the spring element 182 against the mating surface of the rotating oil interrupter element 120. As best showrl in FIGURE 22, t~ese elem~nts have passages 122, 124 which are spaced from the drive axis at th~ same radius. As passage 124 in the rotating interrupter element 120 comes into registration with the passage 122 in the stationary element 118 a small quantity of oil will flow to the axial bore 34 in the drive shaft 18 and then through the series of radial ports in the drive shaft, as earlier described.
The construction of the valve plate J and associated suction and discharge valves is best sho~m in FIGURES 2, 13, , , 9 8~ ~

14 ~nd 15. Xeferring to FI~URE 1~, the valve pla-~e ha4 a series of discharge ports 190 which communicate with the discharge zone 145 defined by the interior rib 142 of the head. A series of suction ports 192, are spaced radially outwardly from the discharge ports and communicate with suction region 147. Reed or flapper-type discharge valves 194 are secured to the top surface of t~e valve plate by rivets 196 which also hold suction v~lves 198 on the bottom of the valve plate.
Since the rivets extend through holes 199 below the bottom surface of the valve plate, a plurality of dimples 200 are formed in the top surface o the cylinder block to accomodate them. The suction valves 198, (FIGURE 13) which are formed with an arcuate section 202 overlying the suction ports 192 at the bottom surface of the valve plate, include a large elon~ated opening 204 in the center thereof to allow . . :
flow of gas to the discharge port 190. The discharge valves are furnished with individual valve stops 206 ~FIGURE 1) which limit the upward travel of the valves.
In FIGURE 14 it will be noted that the valve ~late is also provided with a small kidney shaped port 208, port 210 directly underneath it and another port 212 to the left of port 210 (FIGURES 14 and 15). These ports ~orm part of a gas flow path related to operation o~ the capacity control valve ~. The details o this arrangement will be described below.
The cylinder block, as best sho~m in FIGURES 16 and ]7 has a number o convex lands 21~ which en~age the ~ 4 machined inside surface 21~ of thc housirl~7 A The five cylinders 10 are equally spaced from each other, radially and circum~erentially. A passage 218 parallel to the cylinder axis, extends through the cylinder block and re~,isters with the kidney shaped opening 208 in the valve plate mentioned above. This passage transmits pressure existing with the crankcase 40 through the valve plate to a region which is on one side of the capacity control port 210 in valve plate J
and can be closed by the solenoid valve 220 (see FIGURE 5).
As best shown in FIGURE 5, solenoid valve 220 includes a housing 222, a coil 224 and an armature 226. The armature is connected to a valve member 228 located in the central region of a diaphragm 230. When the coil is energized~
the armature moves to the left pulling the valve member and uncovering control port 210. When de-energized, the diaphragm forces the valve member to the right, closing the port 210.
l~hen the solenoid valve is open, crankcase pressure is transmitted through passage 218 and port 208 into a circular chamber 232 between the diaphragm and the top surface of the valve plate adjacent to control port 210.
A suction responsive control valve 240 controls flow from the crankcase to the suction cavity (when the solenoid valve is open) and includes a sealed evacuated bellows 242 biased by spring 244 and a valve member 246 adapted to seat against the control port 210. Suction pressure is transmitted to the chamber 248 surrounding the bellows in the following manner.
With reference to FI~IIRE 16, the bore 250 in cylinder block B (which receives the suction pressure .

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control valve 240) is associated with a relieved area or undercut surface 252 (FIGURES 5, 16 and 17). This area forms a gas passage 253 between the valve plate and the block extending from port 212 in the valve plate, which is in registration with the distal portion thereof, to chamber 248 surrounding bellows 242. Port 212, in turn, is in registration with the suction plenum 147 in the head and is located a~ a point designated by 254 at (*) in FIGURE ~, just to the left of bore 152.
The higher pressure crankcase gas thus flows along the following path: from crankcase 40 through passage 218, diaphragm chamber 232, control port 210, bellows chamber 248, passage 253, port 21~ and into the suction plenum at pOillt 254.

Operation :~
I~ will be assumed that, initially, the co~pressor is in its ~ull stroke operation, substantially as depicted in FIGURE 1. . ::
As the pulley 48 is driven, torque is transmittçd ~ :
to the drive shaft 18. The link plate, connected to the drive shaft will rotate and the flanges 96, 98 transmit the torque through the links 100, 102 to the drive plate without producing a bending moment on the links. As the drive plate rotates, it acts as a cam driving the wobble plate in a nutating path. The anchor ball 82 slides back and forth in ~:
.~ track 8~ as pistons reciprocate in cylinders 10.
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~ 8 ~ 4 As described in the a~orementioned U. S. patent 3,861,829, the crankcase pressure, created by gas blowing by the pistons, is modulated to control the angle of the drive plate and therefore the length of stroke. The geometry of the pivot points of the links 100, 102 with respPct ~o the drive axis is such that an increase in crankcase pressure will act against the underside of the pistons, and the resultant force will cause the wobble plate to move to a more vertical position, decreasing stroke length and capacity.
Conversely, a decrease in crankcase pressure will allow the force of the gas in the working spaces to move the wobble plate to a more inclined position, increasing stroke length and capacity.
Thus hy controlling crankcase pressure, the capacity of the compressor may be precisely controlled in response to some external variable; in this case, suction pressure.
Assume now that the solenoid valve 220 is open and some predetermined suction pressure exists. Since this suction pressure is enveloping the bellows, as previously described, the position of the bellows valve member responds to suction pressure. If the suction pressure should rise9 due perhaps to an increase in the load, the bellows con~racts opening valve member 246. This allows more gas to flow through port 210 from the crankcase to suction, decreasing the crankcase pressure and increasin~ stroke length. If suction pressure drops, indicating reduced load, the bellows will expand because of spring 244 and reduce flow throug~h port 210 ~rom the crankcase to suction This, of coursc, will increase () / /~
~ O~ 4 cranlccase pressure reduciny, stroke len~h and capacity. The solenoid valve is basically an on-of control. When de-energized, i~ will close por~ 210 causing the crankcase pressure to rise and thus move the wobble plate to minimum stroke position. The stop-pin wlll not permit zero stroke and there will be permitted just enough recîprocation of the pistons to admit some gas to the working spaces, to maintain some flow of oil through the system, and to maintain suf~icient ~ressure differen~ial across ~he compressor so that it will go into stroke when the solenoid valve is energized.

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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A compressor comprising means defining a plurality of gas working spaces each having a piston cooper-ating with suction and discharge ports to compress a fluid therein; a drive shaft; a cam mechanism driven by said drive shaft; a wobble plate driven by said cam mechanism in a nutating path about the drive shaft axis; means operably connected between said wobble plate and the individual pistons to impart reciprocating drive to said pistons, the length of stroke being a function of the angle at which said wobble plate is supported relative to the drive axis; means connected to said drive shaft including at least one axially extending flange member; lug means associated with said cam mechanism having a portion in spaced, juxtaposed relation with a surface on said flange; a pivot link attached at one end thereof to said flange and at the other end thereof to said lug means, said lug means being spaced from the axis of said drive shaft so that said cam mechanism is pivoted at a point not coincident with said drive shaft axis, there being no drive connection at the drive shaft axis between said cam mechanism and said drive shaft, said link being positioned between said flange and said lug means so that the torque is transmitted from said drive shaft to said cam mechanism without producing a substantial bending moment on said pivot link.

2. A compressor as defined in claim, 1 including an anchoring ball attached to said wobble plate; and a track means receiving said anchoring ball for reciprocating motion to prevent rotation of said wobble plate with said cam mechanism, but still permit nutating motion thereof.

3. A Compressor as defined in claim 1 or 2 including a balance weight ring carried by said cam mechanism, said balance weight ring being located so as to compensate for an unbalanced condition of said cam mechanism as its position is changed relative to the drive shaft axis.