WO 2006/085866 PCT/US2005/003819
COMPRESSOR SLIDE VALVE LUBRICATION
BACKGROUND OF THE INVENTION
[0001] The invention relates to compressors. More
particularly, the invention relates to refrigerant
compressors.
[0002] Screw-type compressors are commonly used in air
conditioning and refrigeration applications. In such a
compressor, intermeshed male and female lobed rotors or screws
are rotated about their axes to pump the working fluid
(refrigerant) from a low pressure inlet end to a high pressure
outlet end. During rotation, sequential lobes of the male
rotor serve as pistons driving refrigerant downstream and
compressing it within the space between an adjacent pair of
female rotor lobes and the housing. Likewise sequential lobes
of the female rotor produce compression of refrigerant within
a space between an adjacent pair of male rotor lobes and the
housing. The interlobe spaces of the male and female rotors in
which compression occurs form compression pockets
(alternatively described as male and female portions of a
common compression pocket joined at a mesh zone). In one
implementation, the male rotor is coaxial with an electric
driving motor and is supported by bearings on inlet and outlet
sides of its lobed working portion. There may be multiple
female rotors engaged to a given male rotor or vice versa.
[0003] When one of the interlobe spaces is exposed to an inlet
port, the refrigerant enters the space essentially at suction
pressure. As the rotors continue to rotate, at some point
during the rotation the space is no longer in communication
with the inlet port and the flow of refrigerant to the space
is cut off. After the inlet port is closed, the refrigerant is
compressed as the rotors continue to rotate. At some point
during the rotation, each space intersects the associated
outlet port and the closed compression process terminates. The
1

WO 2006/085866 PCT/US2005/003819
inlet port and the outlet port may each be radial, axial, or a
hybrid combination of an axial port and a radial port.
[0004] It is often desirable to temporarily reduce the
refrigerant mass flow through the compressor by delaying the
closing off of the inlet port (with or without a reduction in
the compressor volume index) when full capacity operation is
not required. Such unloading is often provided by a slide
valve having a valve element with one or more portions whose
positions (as the valve is translated) control the respective
suction side closing and discharge side opening of the
compression pockets. The primary effect of an unloading shift
of the slide valve is to reduce the initial trapped suction
volume (and hence compressor capacity); a reduction in volume
index is a typical side effect. Exemplary slide valves are
disclosed in U.S. Patent Application Publication No.
20040109782 Al and U.S. Patent Nos. 4,249,866 and 6,302,668.
SUMMARY OF THE INVENTION
[0005] According to one aspect of the invention, a compressor
has an unloading slide valve. The valve has a valve element
having a range between a first condition and a second
condition, the second condition being unloaded relative to the
first condition. A first surface of the valve element is in
sliding engagement with a second surface of the housing during
movement between the first and second conditions. The
compressor includes means for lubricating the first and second
surfaces.
[0006] In various implementations, the means may include a
passageway through or along a support for the valve element
extending into a discharge plenum. The means may include a
passageway through or along the housing. The means may be
provided in a remanufacturing of a compressor or the
reengineering of a compressor configuration from an initial
baseline configuration.
2

WO 2006/085866 PCT/US2005/003819
[0007] The details of one or more embodiments of the invention
are set forth in the accompanying drawings and the description
below. Other features, objects, and advantages of the
invention will be apparent from the description and drawings,
and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a longitudinal sectional view of a
compressor.
[0009] FIG. 2 is a transverse sectional view of a discharge
plenum of the compressor of FIG. 1, taken along line 2-2 and
showing a slide valve support.
[0010] FIG. 3 is a sectional view of a slide valve assembly of
the discharge plenum of FIG. 2 in a fully loaded condition,
taken along line 3-3.
[0011] FIG. 4 is a view of the slide valve of FIG. 3 in a
relatively unloaded condition.
[0012] FIG. 5 is a view of a first alternative slide valve
support.
[0013] FIG. 6 is a view of a second alternative slide valve
support.
[0014] FIG. 7 is a partial schematic view of a third
alternative slide valve support installed.
[0015] FIG. 8 is a view of the alternative slide valve support
of FIG 7.
[0016] FIG. 9 is a partial schematic view of a fourth
alternative slide valve support installed.
[0017] FIG. 10 is a partial schematic view of a slide valve
lubrication passageway in a rotor housing.
[0018] Like reference numbers and designations in the various
drawings indicate like elements.
3

WO 2006/085866 PCT/US2005/003819
DETAILED DESCRIPTION
[0019] FIG. 1 shows a compressor 20 having a housing assembly
22 containing a motor 24 driving rotors 2 6 and 28 having
respective central longitudinal axes 500 and 502. In the
exemplary embodiment, the rotor 26 has a male lobed body or
working portion 30 extending between a first end 31 and a
second end 32. The working portion 30 is enmeshed with a
female lobed body or working portion 34 of the female rotor
28. The working portion 34 has a first end 35 and a second end
36. Each rotor includes shaft portions (e.g., stubs 39, 40,
41, and 42 unitarily formed with the associated working
portion) extending from the first and second ends of the
associated working portion. Each of these shaft stubs is
mounted to the housing by one or more bearing assemblies 44
for rotation about the associated rotor axis.
[0020] In the exemplary embodiment, the motor is an electric
motor having a rotor and a stator. One of the shaft stubs of
one of the rotors 26 and 28 may be coupled to the motor's
rotor so as to permit the motor to drive that rotor about its
axis. When so driven in an operative first direction about the
axis, the rotor drives the other rotor in an opposite second
direction. The exemplary housing assembly 22 includes a rotor
housing 48 having an upstream/inlet end face 49 approximately
midway along the motor length and a downstream/discharge end
face 50 essentially coplanar with the rotor body ends 32 and
36. Many other configurations are possible.
[0021] The exemplary housing assembly 22 further comprises a
motor/inlet housing 52 having a compressor inlet/suction port
53 at an upstream end and having a downstream face 54 mounted
to the rotor housing downstream face (e.g., by bolts through
both housing pieces) . The assembly 22 further includes an
outlet/discharge housing 56 having an upstream face 57 mounted
to the rotor housing downstream face and having an
outlet/discharge port 58. The exemplary rotor housing,
4

WO 2006/085866 PCT/US2005/003819
motor/inlet housing, and outlet housing 56 may each be formed
as castings subject to further finish machining.
[0022] Surfaces of the housing assembly 22 combine with the
enmeshed rotor bodies 30 and 34 to define inlet and outlet
ports to compression pockets compressing and driving a
refrigerant flow 504 from a suction (inlet) plenum 60 to a
discharge (outlet) plenum 62 (FIG.2). A series of pairs of
male and female compression pockets are formed by the housing
assembly 22, male rotor body 30 and female rotor body 34. Each
compression pocket is bounded by external surfaces of enmeshed
rotors, by portions of cylindrical surfaces of male and female
rotor bore surfaces in the rotor case and continuations
thereof along a slide valve, and portions of face 57.
[0023] FIG. 2 shows further details of the exemplary flowpath
at the outlet/discharge port 58. A check valve 70 is provided
having a valve element 72 mounted within a boss portion 74 of
the outlet housing 56. The exemplary valve element 72 is a
front sealing poppet having a stem/shaft 76 unitarily formed
with and extending downstream from a head 78 along a valve
axis 520. The head has a back/underside surface 80 engaging an
upstream end of a compression bias spring 82 (e.g., a metallic
coil). The downstream end of the spring engages an
upstream-facing shoulder 84 of a bushing/guide 86. The
bushing/guide 86 may be unitarily formed with or mounted
relative to the housing and has a central bore 88 slidingly
accommodating the stem for reciprocal movement between an open
condition (not shown) and a closed condition of FIG. 2. The
spring 82 biases the element 72 upstream toward the closed
condition. In the closed condition, an annular peripheral
seating portion 90 of the head upstream surface seats against
an annular seat 92 at a downstream end of a port 94 from the
discharge plenum.
[0024] For capacity control/unloading, the compressor has a
slide valve 100 having a valve element 102. The valve element
5

WO 2006/085866 PCT/US2005/003819
102 has a portion 104 along the mesh zone between the rotors
(i.e., along the high pressure cusp). The exemplary valve
element has a first portion 106 (FIG. 3) at the discharge
plenum and a second portion 108 at the suction plenum. The
valve element is shiftable to control compressor capacity to
provide unloading. The exemplary valve is shifted via linear
translation parallel to the rotor axes.
[0025] FIG. 3 shows the valve element at an upstream-most
position in its range of motion. In this position, the
compression pockets close relatively upstream and capacity is
a relative maximum (e.g., at least 90% of a maximum
displacement volume for the rotors, and often about 99%). FIG.
4 shows the valve element shifted to a downstream-most
position. Capacity is reduced in this unloaded condition
(e.g., to a displacement volume less than 40% of the FIG. 3
displacement volume or the maximum displacement volume, and
often less than 30%). In the exemplary slide valve, shifts
between the two positions are driven by a combination of
spring force and fluid pressure. A main spring 120 biases the
valve element from the loaded to the unloaded positions. In
the exemplary valve, the spring 120 is a metal coil spring
surrounding a shaft 122 coupling the valve element to a piston
124. The piston is mounted within a bore (interior) 126 of a
cylinder 128 formed in a slide case element 130 attached to
the outlet case. The shaft passes through an aperture 132 in
the outlet case. The spring is compressed between an underside
134 of the piston and the outlet case. A proximal portion 136
of the cylinder interior is in pressure-balancing fluid
communication with the discharge plenum via clearance between
the aperture and shaft. A headspace 13 8 is coupled via
electronically-controlled solenoid valves 140 and 142 (shown
schematically) to one of: a high pressure fluid source 144 at
or near discharge conditions (e.g., to an oil separator); and
a low pressure drain/sink 150 which may be at or near suction
6

WO 2006/085866 PCT/US2005/003819
conditions (e.g., an oil return). A port 146 is schematically
shown in the cylinder at the headspace at the end of a conduit
network connecting the valves 140 and 142. In an exemplary
implementation, the portions of the conduit network may be
formed within the castings of the housing components.
[0026] The loaded position/condition of FIG. 3 can be achieved
by coupling the headspace 13 8 to the source 144 and isolating
it from drain/sink 150 by appropriate control of valves 140
and 142. The unloaded position/condition of FIG. 4 can be
achieved by coupling the headspace 138 to the drain/sink 150
and isolating it from source 144 by appropriate control of
valves 140 and 142. Intermediate (partly loaded) positions,
not shown, can be achieved by alternating connection of
headspace 13 8 to either the source 144 or the drain/sink 150
using appropriately chosen spans of time for connection to
each, possibly in combination with isolating the headspace 13 8
from both source 144 and drain/sink 150 for an appropriately
chosen span of time (e.g., via appropriate modulation
techniques).
[0027] Returning to FIG. 2, the interfitting of the slide
valve element 102 and the rotor housing is seen. The slide
valve element 102 has a circular cylindrical exterior surface
portion 200 singly convex. This is closely accommodated within
a rotor housing bore defined by a circular cylindrical
interior surface portion 2 02 extending from the rotor housing
end surface 50. During loading and unloading, there is linear
sliding interaction between the surfaces 200 and 202. FIG. 2
further shows concave circular cylindrical exterior surface
portions 206 and 208 of the element 102 in close proximity to
the lobes of the rotors 26 and 28, respectively. The sliding
interaction between the surfaces 200 and 202 may potentially
damage one or both of the surfaces 200 and 202. It may,
accordingly, be desirable to provide additional support for
the valve element 102 and to provide lubrication.
7

WO 2006/085866 PCT/US2005/003819
[0028] To provide additional support to the valve element 102,
a shelf-like support member 220 (FIG. 2) is located in the
discharge plenum 62. The exemplary support 22 0 includes a
mounting flange 222 fastened against the rotor housing
discharge end surface 50. Extending from the opposite surface
of the flange 222, is a sleeve segment 224 unitarily formed
therewith. The sleeve 224 has an upper/inboard surface 225
locally aligned with the surface 202 to combine therewith to
engage the surface 200. The sleeve has first and second
longitudinal edges 226 and 228 and a distal end or rim 230. An
exemplary circumferential span along the surface 200 between
the edges 226 and 228 is 90-180°, more narrowly 120-160°.
[0029] The support 220 may further include features for
assisting in lubrication of the sliding interaction between
the surface 200 on the one hand and the surfaces 202 and 225
on the other hand. One feature involves declination of the
edges 226 and 228 toward the element 102. As refrigerant flow
540 exits the compression pockets and passes beyond the
surfaces 206 and 208, entrained oil may fall onto the edge
surfaces 226 and 228. The declination directs this oil between
the surfaces 200 and 225. As the valve reciprocates during
cycles of loading and unloading, some of this oil is further
passed upstream and downstream to lubricate the interaction
between the surfaces 200 and 202. Exemplary declination is at
least 5° (approximately 10° being shown). Additional volumes
of oil accumulation on surfaces 226 and 228 can be achieved by
increasing the declination even more (e.g., to 30-45°).
Alternatively, additional volumes of oil accumulation can be
achieved using multi-faceted surfaces with at least the
surfaces in closest proximity to valve 102 having greater
declination (e.g., such surfaces 340 and 342 in FIG. 5
discussed below).
[0030] Yet further lubrication features may be incorporated
into the support 220. These features may supplement or replace
8

WO 2006/085866 PCT/US2005/003819
the leakage/seepage flow from the edges into the fine
clearance between slide valve surface 200 and support surface
225. These features may more substantially direct lubricant
flow. FIG. 5 shows an alternative support 320 having a flange
322 and a sleeve segment 324. The junction between the concave
cylindrical portion of the inboard/upper surface 326 and the
upstream face 328 of the flange 322 has a bevel 330. A small
amount of oil can become trapped in this bevel (e.g., a 15°
bevel 4mm in length) to maintain lubrication. Oil initially
collected on one or both edges will flow down the lateral
sides of the channel (formed by the bevel and the adjacent
rotor housing face) to accumulate in the bottom and lubricate
the surface 200 (and therefrom the surfaces 202 and 326).
[0031] FIG. 5 further shows a circumferential channel 332 in
the surface 326 slightly recessed from the distal end 334 of
the sleeve segment. The channel 332 joins the edges 336 and
338 to partially receive oil collected by the edges. The
exemplary edges are doubly faceted with each having a
laterally outboard portion 340 at a relatively shallow
declination (e.g., 10°) and a portion 342 inboard thereof and
more declined (e.g., at an angle of 30°).
[0032] FIG. 6 shows yet another alternative support 420 having
a flange 422 and a sleeve segment 424. The sleeve 424 has an
inboard/upper surface 426. A bevel 430 is formed at the
junction with the flange upstream surface 428. Along each of
the edges 436 and 438, and inboard of a face 440, a relieved
area 442 extends. However, first the relieved area does not
reach the distal end 434 but terminates just before it. The
relieved area also extends through the flange 422 to
communicate with the bevel. Thus, in operation, the relieved
areas 442 due to unrelieved distal portions 444 may trap a
substantial accumulation of oil against the valve element.
This oil may then be directed to the bevel 430 to provide
greater circumferential coverage.
9

WO 2006/085866 PCT/US2005/003819
[0033] FIG. 7 shows an alternative support 460 wherein the
flange 464 is partially immersed in an oil accumulation 466 in
the discharge plenum. One or more passageways 468 extend from
one or more inlets 469 low on the periphery of the flange
(e.g., one passageway on each side). The passageways extend
through the flange and into the rotor housing 48 to outlet
ports 470 in the bore surface 202. The exemplary ports 470 are
near the junctions of the slide valve element surface 200 and
the surface 206 at one side and 208 at the other. The closer
physical proximity of the ports 470 to suction conditions
helps cause a pressure-induced flow 560 of oil to lubricate
the surfaces 200 and 202. FIG. 8 shows intermediate ports 472
in the upstream face of the flange which align with associated
intermediate ports (not numbered) on the rotor case end face
50.
[0034] FIG. 9 shows an alternative support 480 wherein, for
ease of machining, a passageway 481 is formed by an open
channel 482 in the flange suction side surface (closed by the
face 50) in combination with an open channel 484 in the rotor
case bore extending along a bottom end of the surface 202. the
passageway has an inlet 486 and an outlet 488.
[0035] FIG. 10 shows an alternate embodiment wherein a
passageway 490 extends solely through the rotor housing from
an inlet port 491 in the surface 50 below the surface of the
accumulation 466 and to an outlet port 492 in the surface 202.
For this construction, the support (not shown) is optional.
[0036] One or more embodiments of the present invention have
been described. Nevertheless, it will be understood that
various modifications may be made without departing from the
spirit and scope of the invention. For example, in a
reengineering or remanufacturing situation, details of the
existing compressor configuration may particularly influence
or dictate details of the implementation. Accordingly, other
embodiments are within the scope of the following claims.
10

WO 2006/085866 PCT/US2005/003819
CLAIMS
What is claimed is:
1. A compressor apparatus (20) comprising:
a housing (22) having first (53) and second (58) ports
along a flow path;
one or more working elements (26; 28) cooperating with
the housing to define a compression path between suction (60)
and discharge (62) locations along the flow path;
an unloading slide valve (100) having a valve element
(102) having a range between a first condition and a second
condition, the second condition being unloaded relative to the
first condition, a first surface (200) of the valve element
(102) in sliding engagement with a second surface (202) of the
housing (22) during movement between the first and second
conditions; and
means for lubricating the first (200) and second (202)
surfaces.
2. The apparatus of claim 1 wherein:
the range is a range of linear translation;
the second surface (202) is in a rotor case (48); and
the means is at least partially formed on a support (220;
320; 420; 460; 480) extending from a downstream face (50) of
said rotor case (48) into a discharge plenum (62).
3. The apparatus of claim 2 wherein the means comprises
declined edges (226, 228; 336, 338; 436, 438) of a sleeve
segment extending from a mounting flange.
4. The apparatus of claim 3 wherein:
the sleeve segment has a generally concave cylindrical
upper surface (225; 326; 426) extending into the mounting
flange; and
11

WO 2006/085866 PCT/US2005/003819
the means includes a bevel at a junction of the upper
surface and an upstream face of the mounting flange.
5. The apparatus of claim 4 wherein:
the means includes an at least partially circumferential
channel in the upper surface.
6. The apparatus of claim 1 wherein:
the means comprises longitudinal channels formed along
edges of a support and cooperating with the valve element to
trap oil.
7. The compressor of claim 1 wherein the one or more working
elements include:
a male-lobed rotor (26) having a first rotational axis
(500); and
a female-lobed rotor (28) having a second rotational axis
(502) and enmeshed with the male-lobed rotor.
8. The compressor of claim 7 wherein:
in the first condition, the compressor is at least at 90%
of a maximum displacement volume; and
in the second condition, compressor is at less than 40%
of the first condition displacement volume.
9. The apparatus of claim 1 wherein:
the means comprises a passageway extending from a
discharge end face (50) of a rotor case (48) of the housing
(22).
10. A method for remanufacturing a compressor (20) or
reengineering a configuration of the compressor comprising:
providing an initial such compressor or configuration
having:
12

WO 2006/085866 PCT/US2005/003819
a housing (22);
one or more working elements (26; 28) cooperating
with the housing to define a compression path between
suction (60) and discharge (62) locations; and
an unloading slide valve (100) having a valve
element (102) having a range between a first condition
and a second condition, the second condition being
unloaded relative to the first condition, a first surface
(200) of the valve element (102) in sliding engagement
with a second surface (202) of the housing (22) during
movement between the first and second conditions; and
adapting such compressor or configuration to include
means for lubricating the first (200) and second (202)
surfaces.
11. The method of claim 10 wherein:
the adapting includes modifying a support extending (220;
320; 420; 460; 480) into a discharge plenum (62).
12. The method of claim 11 wherein the modifying comprises
adding a channel in an upper surface of the support.
13. The method of claim 11 wherein the adding comprises
adding a passageway (490) through a rotor case (48) of the
housing (22).
14. The method of claim 11 wherein the adding comprises
adding a passageway (468; 481; 490) at least partially through
a rotor case (48) of the housing (22) generally upward from a
port (469; 486; 491) positioned to be within an oil
accumulation in the discharge plenum (62).
13

A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between
a first condition and a second condition, the second condition being unloaded relative to the first condition. A first surface (200) of
the valve element (102) is in sliding engagement with a second surface (202) of the housing (22) during movement between the first
and second conditions. The compressor includes means for lubricating the first (200) and second (202) surfaces.