Note: Descriptions are shown in the official language in which they were submitted.
1~7~8S7
REFRIGER~NT COMPRESSOR
LUBRICATION SYSTEM
This invention relates to refrigerant
compressor lubrication systems and more particularly
to passive type lubrication systems for refrigerant
compressors with swash or wobble plate drive mech-
anisms using oil entrained in the refrigerant to
lubricate-the mechanism's critical bearing surfaces.
Lubrication systems for refrigerant com-
pressors with wobble or swash plate drive mechanisms
have advanced from using splash and/or pressurized
oil circulation such as by a pump to a simpler
less-costly passive type system using oil entrained
in the refrigerant to lubricate the compressor's
critical rotating bearing surfaces, i.e. those of
the wobble or swash plate. However, the conventional
passive type lubrication system normally relies on
the compressor mechanism being located in a crankcase
which may be formed as part of the compressor's
refrigerant circuit, i.e. the compressor's suction
or discharge refrigerant passages. Thus, the
conventional passive type lubrication system is
not normally adaptable to compressors of the type
wherein refrigerant gas pressure is developed in
the crankcase and must be vented to the compressor
suction circuit to maintain optimum compressor
performance and/or as a matter of crankcase pressure
control to control compressor displacement.
According to the present invention, the
venting of the crankcase in the latter type of
compresæor is advantageously utilized to provide
adequate lubrication of the compressor mechanism's
critical bearings surfaces under all operating
conditions and in a simple low-cost passive manner
not re~uiring an oil pump or some other form of
pressurized oil supply. The present invention is
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11'76857
disclosed in its preferred form in a variable
displacement axial piston refrigerant compressor
whose displacement is varied automatically according
to demand by controlling the refrigerant gas pressure
differential between the crankcase and compressor
suction with a demand responsive valve which
operates to bleed or vent the crankcase to suction
to effect the desired displacement control.
According to the present invention, the crankcase-
suction vent is formed with bleed or vent passagemeans connecting the crankcase to compressor suction
between the critical bearing surfaces of the
compressor drive mechanism to lubricate same by
entrained lubricant in the gaseous refrigerant while
also causing some of the entrained lubricant to be
separated by centrifugal action at the bearing
surfaces and returned to the crankcase for further
compressor lubrication usage. As a result, the
amount of lubricant actually delivered to the
compressor suction and available for circulation in
the refrigerant circuit served by the compressor is
substantially reduced so that an amount of lubricant
returned to the crankcase by such centrifugal action
may be retained therein and always available for
such further compress~r~s lubrication.
These and other ob~ects, advantages and
features of the present invention will become more
apparent from the following description and drawing
in which:
Figure 1 is a cross-sectional view of a
variable displacement re~rigerant compressor of the
variable angle wobble plate type having incorporated
therein the preferred embodiment of the passive
lubrication system according to the present invention.
This figure further includes a schematic of an
automotive air conditioning system in which the
compressor is connected.
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Figure 2 is an enlarged cross-sectional
view taken generally along the line 2-2 in Figure 1.
Figure 3 is an enlarged cross-sectional
view of the control valve arrangement in Figure 1.
5Figure 4 is an enlarged view of portions
of the control valve arrangement in Figure 3O
Referring to Figure 1, there is shown a
variable displacement refrigerant compressor 10 of
the variable angle wobble plate type connected in
an automotive air conditioning system having the
normal condenser 12, orifice tube 14, evaporator 16
and accumulator 18 arranged in that order between
the compressorls discharge and suction sides. The
compressor 10 comprises a cylinder block 20 having
a head 22 and a crankcase 24 sealingly clamped to
opposite ends thereof. A drive shaft 26 is supported
centrally in the compressor at the cylinder block 20
and crankcase 24 by radial needle bearings 28 and 30,
respectively, and is axially retained by a thrust
washer 32 inward of the needle bearing 28 and a
thrust needle bearing 34 inward of the radial needle
bearing 30. The drive shaft 26 extends through the
crankcase 24 for connection to an automotive
engine (not shown~ by an electromagnetic clutch 36
which is mounted on the crankcase and is driven from
the engine by a belt 38 engaging a pulley 40 on
the clutch.
The cylinder block 20 has five axial
cylinders 42 extending therethrough (only one being
shown), which are equally angularly spaced about
and equally radially spaced from the axis of drive
shaft 26. The cylinders 42 extend parallel to the
drive shaft 26 and a piston 44 having seals 46 is
mounted for reciprocal sliding movement in each of
the cylinders. A separate piston rod 48 connects
the backside of each piston 44 to a non-rotary
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ring-shaped wobble plate 50 received about the drive
shaft 26. Each of the piston rods 48 is connected
to its respective piston 44 by a spherical rod end
52 which is xetained in a socket 54 on the backside
of the piStOII by a retainer 56 that is swaged in
place. The opposite end of each piston rod 48 is
connected to the wobble plate 50 by a similar
spherical rod end 58 which is retained in a socket
60 on the wobble plate by a split retainer ring 62
which has a snap fit with the wobble plate.
The non-rotary wobble plate 50 is mounted
at its inner diameter 64 on a journal 66 of a rotary
drive plate 68 and is axially retained thereon
against a thrust needle bearing 70 by a thrust
washer 71 and snap ring 72. As shown in Figure 2,
the drive plate 68 is pivotally connected at its
journal 66 by a pair of pivot pins 74 to a sleeve 76
which is slidably mounted on the drive shaft 26,
the pins being mounted in aligned bores 78 and 80
in opposite sides of the journal 66 and radially
outwardly extending bosses 82 on the sleeve 76
respectively with the common axis of the pivot pins
intersecting at right angles with the axis of the
drive shaft 16 to permit angulation of the drive
plate 68 and wobble plate 50 relative to the
drive shaft.
The drive shaft 26 is drivingly connected
to the drive plate 68 by a lug 84 which extends
freely through a longitudinal slot 86 in the
sleeve 76. The drive lug 84 is threadably connected
at one end to the drive shaft 26 at right angles
thereto and extends radially outward past the
journal 66 where it is provided with a guide slot 88
for guiding the angulation of the drive plate 68
and wobble plate 50. The drive lug 84 has flat-
sided engagement on one side thereof at 90 with an
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ear 92 formed integral with the drive plate 68 and
is retained thereagainst by a cross pin 94 which
is at right angles to the drive shaft and is
slidable in and guided by the guide slot 88 as the
sleeve 76 moves along the drive shaft 26. The
cross pin 94 is retained in place on the drive
plate 68 at its ear 92 by being provided with an
enlarged head 96 at one end which engages the lug
at one side of the slot 88 and being received
adjacent the other end in a cross-hole 98 in the
drive plate ear 92 where it is retained by a snap
ring 100. The wobble plate 50 while being
angularable with the rotary drive plate 68 is
prevented from rotating therewith by a guide pin
102 on which a ball guide 104 is slidably mounted
and retained on the wobble plate. The guide pin
102 is press-fitted at opposite ends in the
cylinder block 20 and crankcase 24 parallel to the
drive shaft 26 and the ball guide 104 is retained
between semi-cylindrical guide shoes 106 (only one
being shown) which are slidably mounted for recip-
rocal radial movement in the wobble plate 50.
; The drive lug arrangement for the drive
plate 68 and the anti-rotation guide arrangement
for the wobble plate 50 are like that disclosed in
greater detail in U.S. Patent Nos. 4,175,915 and
4,297,085 respectively assigned to the assignee of
this invention. With such arrangements, there i8
provided essentially constant top-dead-center pos-
itions for each of the pistons 44 by the pin fol-
lower 94 which is movable radially with respect to
the drive lug 84 along its guide slot or cam track -
88 as the sleeve 76 moves along the drive shaft 26
while the latter is driving the drive plate 68
through the drive lug 84 and drive plate ear 92
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8S~
in the direction indicated by the arrow in Figure 2.
As a result, the angle of the wobble plate S0 is
varied with respect to the axis of the drive shaft
26 between the solid line large angle position shown
in Figure 1 which is full-stroke to the zero angle
phantom-line position shown which is zero stroke
to thereby infinitely vary the stroke of the
pistons and thus the displacement or capacity of
the compressor between these extremes. As shown
in Figure 1, there is provided a split ring return
spring 107 which is mounted in a groove on the
drive shaft 26 and has one end that is engaged by
the sleeve 76 during movement to the zero wobble
angle position and is thereby conditioned to initiate
return movement.
The working ends of the cylinders 42 are
covered by a valve plate 108 which together with an
intake or suction valve disk 110 and an exhaust
or discharge valve disk 112 located on opposite
sides thereof are clamped to the cylinder block 20
between the latter and the head 22. The head 22
is provided with a suction cavity or chamber 114
which is connected through an external port 116
to receive gaseous refrigerant from the accumulator
18 downstream of the evaporator 16. The suction
cavity 114 is open to an intake port 118 in the
valve plate 108 at the working end of each of the
cylinders 42 where the refrigerant is admitted to
the respective cylinders on their suction stroke
each through a reed valve 120 ormed integral with
the suction valve disk 110 at these locations.
Then on the compression stroke, a discharge port 122
open to the working end of each cylinder 42 allows
the compressed refrigerant to be discharged into
a discharge cavity or chamber 124 in the head 22
by a discharge reed valve 126 which is fo~med
85~
integral with the discharge valve disk 112 at these
locations, the extent of opening of each of the
discharge reed valves being limited by a rigid
back-up strap 128 which is riveted at one end to
the valve plate 108. The compressor's discharge
cavity 124 is connected ~o deliver the compressed
gaseous refrigerant to the condenser 12 from whence
it is delivered through the orifice tube l~ back
to the evaporator 16 to complete the refrigerant
circuit as shown in ~igure l.
The wobble plate angle and thus compressor
displacement is controlled by controlling the refrig-
erant gas pressure in the sealed interior 129 of
the crankcase behind the pistons.44 relative to
the ~uction pressure. In this type of control,
the angle of the wobble plate is determined by a
force balance on the pistons wherein a slight eleva-
tion of the crankcase-suction pressure differential
above a set suction pressure control point creates
a net force on the pistons that results in a turning
moment about the ~obble plate pivot pins 74 that
acts to reduce the ~obble plate angle and thereby
reduce the compressor capacity. For such control
one practice is to emplo~ a control valve which is
automatically actuated by a bellows or diaphragm
biased by compressor suction pressure and operates
: when the air conditioning capacity demand is high
and the resultin~ suction pressure rises above the
control point so as to maintain a bleed or vent from
30 .crankcase to suct;:on so that there is no crankcase-
suction pressure differential. ~s a result, the
wobble plate 50 will then angle to its full stroke
large angle position shown in Fi~ure 1 establishing
maximum displacement. On the other hand, when the
air conditioning capacity demand is lowered and
the suction pressure ~alls to the control point,
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the control val~e wlth its suction pressure bias
then operates to close off the crankcase vent
connection ~ith suction and either provide communi-
cation between the compressor discharge and the
crankcase or allo~ the pressure therein to increase
as a result o~ gas blow-hy past the pistons. This
has the effect of increasing the crankcase.suction
pressure differential which on slight elevation
creates a net force on the pistons that results in
a turning moment about the wobble plate pivot pins
74 that reduces the wobble plate.angle and thereby
reduces the compressor displacement. But another
more advanced control practice is to use the variable
displacement control.~alve arrangement generally
designated as 130.which is responsive to compressor
discharge pressure as.~ell as suction pressure to
' automatically control the compressor displacement
or capacity accordin~ to demand, In the latter
control valve arrangement.as in the former, there
is venting of the crankcase to compressor suction
to control the crankcase pressure and thereby the
; compressor displacement and such ~enting is utilized
` . b~ the present invention to provide adequate
. lubrication of the campressor~s critical bearing
surfaces under all operating conditions and in a
simple low_cost passiVe mannex not re~uiring
an oil pump or some other foxm of pressurized oil
supply.
The preferred embodiment of the passive
3a lubrication system of the present invention is shown
incorporated in the advanced control valve arrange-
ment 130 and to understand the improved lubrication
system it is helpful to also fully understand this
control valving and its operation. As shown in
Figures 1 and 3, the control valve arrangement 130
comprises a valve housing 132 which in the preferred
... . . . .. ..
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embodiment is formed integrally in the head 22 and
has a stepped blind bore 133 having an open external
end 134 through the periphery of the head 22 and a
closed internal end 135 with stepped and progressively
smaller bore portions designated 136, 138, 140
and 142. The intermost and largest diameter bore
portion 136 is open thxough a radial port 144 and
a passage 146 in the head 22 to the suction cavity
114 which is also in the compressox's head. The
present invention is incorporated in the control
valve arrangement by connecting the adjacent and
smaller diameter bore portion 138 to the interior 129
of the crankcase through lubrication-vent passage
means formed by a radial port 148 in the head 22, -
a port lS0 in the ~alve plate 108, passageways 152
and 154 in the cylinder block 20, a central axial
passage 156 and intersecting radial passage 158
in the drive sha~t 26, a central axial passage 160
in one of the drive plate pivot pins 74 and along
the drive plate journal 66 past the wobble plate 50
and through its thrust needle bearing 70 (see
Figures 2 and 3~. ~s will be described in more
detail later, the crankcase ~ent path thus provided
apart from its crankcase pressure control function
- 25 effects by such routin~ assured lubrication of the
wobble plate mechanismls critical rotating bearing
surfaces. Referring meant~me back to the valve, ~he
adjacent and smaller diameter bore port1on 140 of
the valve housin~ is also connected to the interior
3Q 129 of the crankcase 24 but in a direct route through
a radial port 162 in head 22, a port 164 in valve
plate 108 and a passa~e 166 in the cylinder block 20.
The adjacent and smallest diameter bore portion-142
at the closed end 136 of the stepped ~alve body
bore is directly open to the discharge cavity 124
through a radial port 168 in the head.
:1176857
A cup-shaped valve bellows cover 170
having a closed outer end 172 and an open inner
end 174 is sealingly inserted in a fixed position
in the open end 134 of the housing's stepped bore
133 at the large diameter bore portion 136 with the
positioning thereof determined by a cylindrical
flange 176 on the cover engaging a shoulder 178
at the stepped outer end of the large diameter
bore portion 136 as best seen in Figure 3. Sealing
thereof is provided by an O-ring 180 which is
received in an internal groo~e in the large bore
portion 136 and sealingly contacts with a cylin-
drical land 182 of the bellows cover 170. Retention
of the bellows cover 170 i9 provided by a snap ring
, 15 184 which is received in an interior groove in the
bore end }34 and engages the outer side of the
bellows cover flange 176. Thus, the bellows
~; cover 170 has its closed end 172 positioned in
; and closing the open end 134 of the va;ve housing
132 and its open end 174 ~acing inward toward the
closed end 135 o~ the valve housing.
An evacuated bellows 186 is concentrically
located within the bellows cover 170 and is seated
against the latter's closed end 172. The bellows
2~5 186 has a cup-shaped corrugated thin-wall-metal
casing 187 which at its closed and seated end
receives a spring seat member }88, The other end
of the bellows casing 187 is sealingly closed by
an end member 190 through which an output rod 191
centrally extends and is sealingly fixed thereto.
The bellows 186 is evacuated so as to expand and
contract in response to pressure changes within a
surrounding annular pressure control cell 192 which
is formed by the exterior of the bellows and the
interior of the bellows cover 170 and is continu-
ously open through a radial port 194 in the bellows
~176857
cover 170 to the suction pressure communicatingport 144 of the control valve housing 132. A
compression coil spring 196 is located in the
bellows and extends between the bellow's two
rigid end members 188 and 190. The thus captured
spring 196 normally maintains the bellows in an
extended position producing an outward force on the
output rod 191. The output rod 191 is tapered at
its inner end 200 for guided movement in a blind
bore 202 in the interior seat member 188 on con-
traction of the bellows. The exterior and opposite
end 206 of the output rod 191 is pointed and seats
in a coupling pocket 208 of an actuating valve
pin member 210, The actuating valve pin mem~er 210
at its opposite end i8 formed with a reduced valve
needle or stem portion 212 and is sealingly slidably
supported for reciprocal movement along an inter-
mediate constant diameter portion or length 214
thereof in a central axial bore 216 formed in a
stepped spool-shaped cylindrical valve body 218
mounted in the valve housin~ bore 133 inward of the
bellows 186.
The valve body 218 is formed with a
cylindrical land 219 which is press-fitted in the
open end 174 of the bellows cover 170, this land
extending sufficiently within the open end of the
valve bellows cover to provide an axially adjustable
sealed juncture which is operable to provide cali-
bration of the bellows unit. Moreover, a conical
compression coil spring 220 is concentrically
positioned intermediate the bellows end member 190
and the outer end of the valve body 218 and acts
to hold the bellows 186 in seating engagement with
the bellows cover 170. With such arrangement,
the pointed exterior end 206 of the bellows force
output rod 1~1 automatically aligns and couples
11
~176S57
with the val~e pin pocket 208 in the actuating valve
pin member 210 whereby the bellows output rod and
the actuating valve pin member are conditioned
to move axially in unison.
The central valve body 218 is sealingly
received and positioned in the respective pro-
gressively smaller diameter bore portions 138, 140
and 142 by progressively smaller diameter land
portions 221, 222 and 224 formed on the valve body
which each have an O-ring seal 226, 228 and 230
respectively received in an annular groove therein
and sealingly engaging the respective valve body
bore portions. The O-ring 226 at the large diameter
land portion 221 thus'seals off the bellows pressure
control cell 192 wh$ch'is open to suction pressure
; and also cooperates with the O-ring seal 228 at
the adjacent smaller diameter valve body land 222
to seal off an annular chamber 232 at the bore
portion 138 which is indirectly open throu~h the
port 148 to the cr~ikcase through the vent passage
provided by the pXesent invention. The O-ring seal
228 also cooperates with the O-ring-æeal 230 at the
adjacent smaller diameter val~e body land 224 to
seal off an annular chamber 234 extending about
the spool valve body at the bore portion 140 which
is directly open to the'crankcase through the port 162.
The valve body O~ring seal 230 also seals off the
closed end 136 of the valve body bore which is
directly open at its smalles't diameter bore portion
142 through the port 168 to the discharge cavity 124.-
The central bore 216 through the midportionof the valve body 218 joins at its end nearest
the bellows with a counterbore 236 which in turn
joins with a larger counterbore 238 that is open
to the bellows pressure control cell 192 and thus
to compressor suction. The counterbore 236 forms
12
~176857
an annular crankcase bleed or vent valve passage 240
which extends about the actuating valve pin member
portion 214 and is connected by a pair of diametri-
cally aligned radial ports 242 to the chamber 232
and thus to the crankcase. The larger diameter
counterbore 238 is open to the crankcase vent valve
passage 240 and slidably supports an enlarged cylin-
drical head portion 244 formed on the actuating
valve pin member 210 at the bellows end thereof.
The enlarged valve pin member head portion 244
operates to control crankcase venting and is pro-
vided for that purpose with a tapered step 246
where it joins with the long cylindrical pin
portion 214. The tapered step 246 provides a valve
face which is engageable with a conical valve seat
248 forming the step between the valve body counter-
; bores 236 and 238 to close the crankcase vent
valve passage 240 as shown in ~igure 4 and des-
cribed in more deta~l later. Alternatively, the
,20 valve face 246 is movable off the valve seat 248
to first open the crankcase ~ent valve passage 240
to the counterboxe 238 and thence upon slight
further movement the val~e head 244 uncovers a pair
of longitudinally extending passages 250 ~n the
-25 counterbore 238 ~hich are then effective to connect
the crankcase vent valve passage 240 with the bellows
pressure control ceIl 192 and thus with the compressor
suction cavity 114.-
The central bore 216 in the valve body 218
~oins at its oppos~te end'with'a lar~er diametervalve body bore 252 ~hich is closed at one end by
a tapered step 253'extending ~rom the actuator
valve pin member port~on 214 and receives at its
other end a crankcase charge valve body member 254.
The crankcase charge valve body member 254 is press-
fitted in the val~e body bore'252 to form on one
13
~L176857
side thereof and within the valve body a cavity 256
which extends about the actuator valve pin member
portion 214 and is open through a radial port 258
in the valve body to the outwardly located chamber
234 and thus to the crankcase. The crankcase
charge valve body member 254 also cooperates with
the small diameter valve body portion 224 and its
O-ring seal 230 to ~orm with the closed end 135
of the valve housing bore a chamber 260 which is
open through the radial port 168 in the valve
housing to the compressor discharge cavity 124.
The crankcase charge valve body member
254 is formed with a bell-shaped valve cavity 262
which is exposed through an open end 264 to the
discharge pressure connected chamber 260 and is
openable at the other end to a central crankcase
charge valve port 266 that receives the smaller
diameter stem portion 212 of the actuating valve pin
member 210 and opens to the chamber 256 communi-
cating with the crankcase. Mounted in the crank-
case charge valve body member 254 in the caYity 262
is crankcase charge valving comprising a large ball
segment 268 and a small ball segment 270 which are
welded together and are biased by a conical coil
compression spring 272 so that the large ball
segment 268 is held against the end of actuating
valve pin member stem portion 212 and normally
seats on the complementary shaped portion of the
bell-shaped cavity 262 to close the crankcase
charge valve port 266. The spring 272 is seated
at its opposite and enlarged end on a spunover
-annular edge 274 of the valve body member 254 which
defines the opening 264 to the valve cavity and
there being mounted thereover a screen 275 to
filter out foreign matter. The conical spring's
smaller end has a slightly smaller diameter than
14
~176857
the smaller ball segment 270 allowing this spring
end to be snap fastened for capture between the
large and small ball segments. This facilitates
the universal movement of the unitary ball valve
element 268, 270 with respect to the spring 272
so that the large ball valve element 268 will
mate with its valve seat sufficiently to insure
their sealing relation when the valve is in its
closed postion shown in ~igure 3 and so that the
ball valve element 268 will remain in alignment
during valve opening movement to its full open
position shown in ~igure 4 in which condition the
refrigerant gas at discharge pressure is allowed
to ~low through the crankcase charge valve port
past the actuating valve pin member stem portion
212 to the crankcase.'
In addition to the spring biasing force
acting to close the valve element 268 on the crank-
case charge valve port 266 and also simultaneously
20 'open the crankcase vent valve port 240 by acting
through the valve elements 268, 270 on the actuating
; valve pin member 210 to effect the open position
of-its vent valve end 244, there is effected a
.
gas discharge pressure bias achieved by the dis-
charge pressure in cavity 260 acting on the unbal-
anced upstream side of the movable crankcase charge
valve segments 268, 270. This discharge pressure
bias at the crankcase chargîng end of the control
val~e arrangement is used to depress the compressor's
displacement control point with increasing discharge
pressure in addition to the discharge pressure being
made available through the opening of the crankcase
charge val~e port 266 by the controlling charge
valve elements"26'8,270 to charge the crankcase to
achieve decreased compressor displacement as described
in more detail later,
~176857
16
The large ball valve segment 268 is
caused to move off its valve seat and open the
crankcase charge valve port 266 against the force
of spring 272 and the variable discharge pressure
bias by expansion of the suction pressure and
spring biased bellows 186 acting through the
actùating valve pin member 210 which at the same
time acts at its valve head 244 to close the crank-
case bleed valve port-240. On the other hand,
these crankcase charge and crankcase vent valve
: operations are reversed by contraction of the suction
pressure biased bellows 186 assisted by the dis-
charge pressure bias at the crankcase charge valve 268.
Describing now the operation of the
variable displac,ement compressor control valve
arrangement 130 in the system, gaseous refrigerant
leaving the accumulator 18 at low pressure enters
the compressorls suction cavity 114 and is discharged
to the compressox~s dischar~e cavity 124 and thence
to the condenser 12 at a certain rate dependent
on the compressor~s ~obble plate angle. At the
same time, the gaseous re~rigerant at suction
pressure is transmitted-at the compressor to-the
bellows cell 192 to act on the evacuated bellows 186
which tends to expand in response to a decrease in
the suction pressure thus acting thereon to provide
a force on the bellows output rod 191 which urges
movement o~ the actuating valve pin m2mber 210
toward the position s~own'in ~igure 4 closing the
crankcase vent valve port 240 and simultaneously
opening the crankcase charge valve port 266. On
the other hand, the gaseous refrigerant discharge
pressure at the compressor is at the same time
transmitted to the valve chamber 260 to act on the
ball valve arrangement 268, 270 in opposition to
bellows expansion to urge closing of the crankcase
16
~76~3S7
charge valve port 266 and simultaneous opening
of the crankcase vent valve port 240 as shown in
Figure 3. These variable pressure biases are in
addition to the spring biases which act to normally
condition the control valve arrangement 130 so as
to close the crankcase charge valve port 266 and
; simultaneously open the crankcase vent valve port
240 to thereby normally effect maximum compressor
displacement by establishing zero crankcase-suction
pressure differential. The objective is~ts ~tch the
compressor displacement with the air conditioning
demand under all conditions so that the evaporator
16 is kept just above the freezing temperature
tpressure) without cycling the compressor on and
off with the clutch 36 and with the optimum being
to maintain as cold an evaporator as can be achieved
at higher ambients without evaporator freeze and at
lower ambients, as high an evaporator temperature
as can be maintained while still supplying some
de-humidification. To this end, the control point
for the control valve arrangement 130 determining
displacement change is selected so that when the
air conditioning capacity demand is high, the suction
pressure at the compressor after the pressure drop
from the evaporator 16 will be above the control
point (e.g. 170~210 k~a~. The control valve arrange-
ment 130 is calibrated at assembly at the bellows
186 and with the spring biases so that the then
existing dischar~e~suction pressure differential
acting on the control valve arrangement is su~ficiently
high to maintain same in the cond~tion shown in
~igure 3 closing the crankcase charge valve port
266 and opening the crankcase vent valve port 240.
The control valve arrangement 130 will then maintain
a bleed or vent from the crankcase to suction while
simultaneously closing off discharge pressure thereto
17
~L176857
18
so that no crankcase-suction pressure differential
is developed and as a result, the wobble plate 50
will remain in its maximum angle position shown
in solid line in Figure 1 to provide maximum com-
pressor displacement. Then when the air conditioningcapacity demand reduces and the suction pressure
reaches the control point, the resulting change in
the discharge-suction pressure differential acting
on the control valve arrangement 130 will condition
its valving to then open the crankcase charge valve
port 266 and simultaneously close the crankcase
bleed port 240 and thereby elevate the crankcase-
suction pressure differential. The angle of the
wobble plate 50 is controlled by a force balance
on the pistons 44 80 only a slight elevation (e.g.
40-100 kPa) o~ the crankcase-suction pressure is
effective to create a net force on the pistons that
results in a moment about the wobble plate pivot
axis that reduces the wobble plate angle and
thereby the compressor displacement. Moreover, in
that the control valve bellows 186 in addition to
being acted on by the~suction control pressure has
to also overcome discharge pressure in expanding
to elevate the crankcase-suction pressure differential
to reduce compressor disp~acement, the displacement
change control point is thus depressed with increasing
discharge pressure (higher ambients). In th~t the
refrigerant flow rate, and in turn suction line
pressure drop, increases with increasing discharge
pressure (higher ambients) the control valve will
depress the control point proportional to the dis-
charge pressure and likewise suction line pressure
drop. This compressor displacement compensating
feature permits controlling at the compressor suction
while maintaining a nearly constant evaporator pres-
sure (temperature) above freezing which has been
found to result in substantially better high load
performance and reduced power consumption at low
ambients on a yearly basis.
18
~176~357
In the above type of compressor as in some
other reciprocating piston type compressors and
engines with crankcase-to-suction venting but
without the lubrication-venting arrangement of the
present invention, most if not all the oil that is
added to the crankcase for lubrication will become
entrained in the gas therein and be discharged from
the cylinders because of the venting to suction.
On the other hand, some of the oil that is discharged
is returned to the crankcase via the piston rings
scraping the cylinder walls and/or the operating
pressure differential blowing the oil past the
piston rings. ~ccording to the present invention,
the lubrication-vent passage means formed by the
ports and pas5ages 148, 150, 152, 154, 156, 158
and 160 route the venting of the crankcase 24 to the
compressor's suction cavity 114 through the rotating
bearing surfaces o~ the wob~le plate 50, i.e. those
at the thrust needle bearing 70-and at the journal
66 which supports the wobble plate at its inner
diameter 64. The arrows shown in Tigures 1 and 2
depict the circulation o~ the re~rigerant within the
compressor wherein the:entxained oil is also made
available to lubricate the drive shaft~s two radial
needle bearings 28 and 30 and the rubbing or sliding
surfaces of the variable angle wobble plate mechanism
in the crankcase, The venting path thus provided
forces the pressurized gaseous refrigerant with the
oil entrained therein to flow radially in~ardly
3Q through the wobble plateks anti-friction bearing,
i.e. the thrust needle bearing 70, and also along
or through the drive plate ~ournal 66 at the inner
diameter 64 of the wobble plate 50 to reach the
vent passage 160 to the compressor's suction cavit~
114 in the wobble platepivot at the one pivot pin
thus assuring lubrication of these critical rotating
19
~176~357
bearing surfaces. Moreover, the entrained oil is
caused to separate by centrifugal action at these
rotating bearing surfaces and be returned to the
crankcase for further compressor lubrication usage.
As a result, the amount of oil actually delivered
with such venting to the compressor suction cavity
and available for discharge ~rom the compressor
at the discharge cavity to the refrigerant circuit
is substantially reduced so that some amount of the
oil returned to the crankcase by the centrifugal
action is retained therein and always available
for further lubrication of the compressor mechanism
and particularly its critical bearing surfaceæ.
This as~ures that under all compressor operating
conditions, some amount of oil will be retained
in the crankcase for lubrication of the mechanism's
critical bearin~ surfaces. Moreover, the amount of
oil permitted to circulate in the refrigeration
system external to the compressor is minimized which
results in a substantial improvement in air condi-
tionin~ performance.
The above~described preferred embodiment
is illustrative of the invention which may be modi-
fied within the scope of the appended claims.
