U.S. patent application number 10/769707 was filed with the patent office on 2004-09-23 for compressor vibration protection system.
Invention is credited to McCroskey, William W., Millet, Hank E., Rajendran, Natarajan.
Application Number | 20040184928 10/769707 |
Document ID | / |
Family ID | 24052795 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040184928 |
Kind Code |
A1 |
Millet, Hank E. ; et
al. |
September 23, 2004 |
Compressor vibration protection system
Abstract
A compressor assembly includes a compressor, a controller, a
gateway and a system controller. The controller includes a
vibration sensor and monitors operational characteristics of the
compressor. The gateway is in communication with the controller,
the system controller is in communication with the controller
through the gateway.
Inventors: |
Millet, Hank E.; (Piqua,
OH) ; Rajendran, Natarajan; (Centerville, OH)
; McCroskey, William W.; (Sidney, OH) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
24052795 |
Appl. No.: |
10/769707 |
Filed: |
January 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10769707 |
Jan 30, 2004 |
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09977552 |
Oct 15, 2001 |
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09977552 |
Oct 15, 2001 |
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09515802 |
Feb 29, 2000 |
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6302654 |
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Current U.S.
Class: |
417/278 |
Current CPC
Class: |
F04C 2240/603 20130101;
F04C 29/0014 20130101; F04C 2270/86 20130101; F04C 18/0215
20130101; F04C 2270/02 20130101; G05B 2219/37435 20130101; F04C
2270/18 20130101; G05B 23/0235 20130101; F04C 29/02 20130101; F04C
23/001 20130101; F04C 2270/19 20130101; G05B 23/0291 20130101; G05B
23/0286 20130101; F04C 2270/12 20130101; F04C 28/28 20130101; G05B
2223/06 20180801; F04C 2270/90 20130101; F04C 28/26 20130101; F04C
23/008 20130101; G05B 9/02 20130101; F04C 29/04 20130101 |
Class at
Publication: |
417/278 |
International
Class: |
F04B 049/00 |
Claims
What is claimed is:
1. A compressor comprising: a housing; a fluid compression
mechanism disposed on said housing; and a controller mounted on
said housing and including a vibration sensor, said controller
operable to control compressor capacity and monitor operational
characteristics of said compressor.
2. The compressor of claim 1, wherein said controller includes a
circuit board and said vibration sensor is disposed on said circuit
board.
3. The compressor of claim 1, wherein said vibration sensor
includes an electrical switch.
4. The compressor of claim 3, wherein said electrical switch is
operable upon minimum displacement.
5. The compressor of claim 3, wherein said vibration sensor
includes an RC filter.
6. The compressor of claim 1, wherein said controller creates an
event history.
7. The compressor of claim 1, wherein said controller includes a
microprocessor.
8. The compressor of claim 1, wherein said controller includes a
first counter operable to continuously count vibration pulses
during a predetermined period of time, a second counter operable to
count between a lower time limit and an upper time limit, and a
limit condition flag operable between an on condition and an off
condition, said limit condition flag trigger at said on condition
when the number of pulses during said predefined time period
exceeds a pulse limit, said limit condition flag at said off
condition when said pulses counted during said predetermined period
of time is less than said pulse limit, wherein said second counter
counts toward said upper limit when said condition limit flag is at
said on condition and counts toward said lower limit when said
limit condition flag is at said off condition, wherein a vibration
trip condition is reached when said second counter counts to said
upper limit.
9. The compressor of claim 1, wherein said vibration sensor
includes a ball and spring wire mounted in a bore.
10. The compressor of claim 9, wherein a sensitivity of said
vibration sensor is defined by a stiffness of said spring and a
mass of said ball.
11. The compressor of claim 8, wherein said stiffness of said
spring is a function of a diameter, length and material of said
spring.
12. The compressor of claim 10, wherein said mass of said ball is a
function of its material and diameter.
13. A cooling system including: a compressor; a controller mounted
on said compressor and including a vibration sensor, said
controller operable to control a capacity of said compressor and
monitor operational characteristics of said compressor; and a
communication gateway associated with said controller.
14. The cooling system of claim 13, further comprising a system
controller in communication with said controller through said
communication gateway.
15. The cooling system of claim 13, wherein said controller
includes said communication gateway.
16. The cooling system of claim 13, wherein said controller
includes a circuit board and said vibration sensor is disposed on
said circuit board.
17. The cooling system of claim 13, wherein said vibration sensor
includes an electrical switch.
18. The cooling system of claim 17, wherein said electrical switch
is operable upon minimum displacement.
19. The cooling system of claim 17, wherein said vibration sensor
includes an RC filter.
20. The cooling system of claim 13, wherein said controller creates
an event history.
21. The cooling system of claim 13, wherein said controller
includes a microprocessor.
22. The cooling system of claim 13, wherein said controller
includes a first counter operable to continuously count vibration
pulses during a predetermined period of time, a second counter
operable to count between a lower time limit and an upper time
limit, and a limit condition flag operable between an on condition
and an off condition, said limit condition flag trigger at said on
condition when the number of pulses during said predefined time
period exceeds a pulse limit, said limit condition flag at said off
condition when said pulses counted during said predetermined period
of time is less than said pulse limit, wherein said second counter
counts toward said upper limit when said condition limit flag is at
said on condition and counts toward said lower limit when said
limit condition flag is at said off condition, wherein a vibration
trip condition is reached when said second counter counts to said
upper limit.
23. The cooling system of claim 13, wherein said vibration sensor
includes a ball and spring wire mounted in a bore.
24. The cooling system of claim 23, wherein a sensitivity of said
vibration sensor is defined by a stiffness of said spring and a
mass of said ball.
25. The cooling system of claim 22, wherein said stiffness of said
spring is a function of a diameter, length and material of said
spring.
26. The cooling system of claim 24, wherein said mass of said ball
is a function of its material and diameter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 09/977,552 filed on Oct. 15, 2001, which is a
division of U.S. patent application Ser. No. 09/515,802 filed on
Feb. 29, 2000 (now U.S. Pat. No. 6,302,654). The disclosures of the
above applications are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the control and protection
of compressors. More particularly, the present invention relates to
a compressor control and protection system which combines
compressor temperature control, phase protection, vibration
protection, oil level control and protection, pressure sensing and
pulse width modulation control.
BACKGROUND AND SUMMARY OF THE INVENTION
[0003] Scroll type machines are becoming more and more popular for
use as compressors in both refrigeration as well as air
conditioning applications due primarily to their capability of
extremely efficient operation. Generally, these machines
incorporate a pair of intermeshed spiral wraps, one of which is
caused to orbit relative to the other so as to define one or more
moving chambers which progressively decrease in size as the travel
from an outer suction port toward a center discharge port. The
means for causing the orbiting of one of the scroll members is in
many cases an electrical motor. The electric motor operates to
drive the one scroll member via a suitable drive shaft affixed to
the motor rotor. In a hermetic compressor, the bottom of the
hermetic shell normally contains an oil sump for lubricating and
cooling purposes.
[0004] Scroll compressors depend upon a number of seals to be
created to define the moving or successive chambers. One type of
seal which must be created are the seals between opposed flank
surfaces of the wraps. These flank seals are created adjacent to
the outer suction port and travel radially inward along the flank
surface due to the orbiting movement of one scroll with respect to
the other scroll. Additionally sealing is required between the end
plate of one scroll member and the tip of the wrap of the other
scroll member. Because scroll compressors depend upon the seals
between flank surfaces of the wraps and the seals between the end
plates and opposing wrap tips, suction and discharge valves are
generally not required.
[0005] While the prior art scroll machines are designed to run
trouble free for the life of the scroll machine, it is still
necessary to monitor the operation of the compressor and
discontinue its operation when specific criteria have been
exceeded. Typical operational characteristics which are monitored
include the discharge temperature of the compressed refrigerant,
the temperature of the motor windings, three-phase reverse
rotational protection, three-phase missing phase/single phase
protection and an anti-short cycle. The monitoring of these
characteristics and the methods and devices for monitoring these
characteristics have been the subject of numerous patents.
[0006] Recently, it has been found that by monitoring the
vibrational characteristics of the scroll machine, it is possible
to predict problems with a scroll machine before these problems
result in a failure to the entire system. For instance, in a
refrigeration or air conditioning system which incorporates
numerous scroll machines, the abnormal vibration of one of the
scroll machines can result in a fracture of the refrigeration tube
associated with that individual scroll machine. The fracture of
this tube will result in a total loss of the system refrigerant,
possible damage to property, expensive repairs and in some cases
could be hazardous. Assignee's U.S. Pat. No. 5,975,854, the
disclosure of which is incorporated herein by reference, disclosed
a device which is capable of independently monitoring the
vibrational characteristics of an individual scroll machine.
[0007] Accordingly, what is needed is a system which is capable of
communicating with and monitoring the operational characteristics
of a compressor and/or a group of compressors. The system should
have the ability to monitor all aspects of the operational
characteristics of each of the compressor as well as having the
ability to communicate with a central monitoring system to identify
current or possible problems associated with the individual
compressor. The central monitoring system can be a centralized rack
gateway which communicates with each individual compressor, a
rack/system control that acts as a gateway to communicate with each
individual compressor or an Internet web server that communicates
with a gateway associated with each compressor.
[0008] The present invention provides the art with an advanced
compressor control and protection system. The advanced compressor
control and protection system incorporates internally integrated
sensing, protection and control functions not provided by the prior
art motor protection modules in use today. The control and
protection system of the present invention integrates these
functions with the compressor for improved overall system cost,
reliability and value and thus provides improved compressor
protection, simpler system wiring, diagnostics and communications.
The advanced compressor control and protection system of the
present invention provides a common hardware platform for a broad
range of compressor modules. The system of the present invention
provides a reduction in cost due to common electronics platform for
all sensing and control functions, higher reliability due to
improved protection because of common logic incorporating a
multiplicity of sensor and status information as well as reduction
in cost and improved reliability due to reduction in field wiring
of individual stand-alone protection systems.
[0009] The present invention utilizes a low-cost communications
enabling approach using intermediate communications protocol to
facilitate use of adapters and gateways for virtually any
communications network with minimal cost burden on non-network
applications. Multiple sensors are adapted for use internally
within the compressor which provide signals which are analogous to
the actual physical quantities being measured. Examples are
discharge temperature, motor winding temperatures, gas pressure
(suction, discharge) and differential pressures, liquid level,
liquid refrigerant, relative percentage of liquid refrigerant
versus oil and others.
[0010] Other advantages and objects of the present invention will
become apparent to those skilled in the art from the subsequent
detailed description, appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0012] FIG. 1 is a vertical cross-sectional view through the center
of a scroll type refrigeration compressor incorporating the control
and protection system in accordance with the present invention;
[0013] FIG. 2 is a top plan view of the compressor shown in FIG.
1;
[0014] FIG. 3 is a perspective view of the electrical enclosure
shown in FIG. 2;
[0015] FIG. 4 is a side view of the compressor protection and
control subsystem shown in FIG. 3;
[0016] FIG. 5 is a functional block diagram of the compressor
protection and control subsystem shown in FIG. 3;
[0017] FIG. 6 is a top plan view of the preferred implementation of
the vibration sensor which can be incorporated into the compressor
protection and control subsystem shown in FIG. 4;
[0018] FIG. 7 is a side cross sectional view of the vibration
sensor shown in FIG. 5;
[0019] FIG. 8 is a vertical cross-sectional view of a compressor
having a capacity control system;
[0020] FIG. 9 is a vertical cross-sectional view of a compressor
having a liquid injection system;
[0021] FIG. 10 is a plan cross-sectional view of a compressor
having an oil injection system;
[0022] FIG. 11 is a schematic illustration of the gateway options
available for the compressor;
[0023] FIG. 12 is a schematic representation of a control system
for a plurality of compressors using various gateways;
[0024] FIG. 13 is a schematic representation of another control
system for a plurality of compressors using various gateways;
[0025] FIG. 14 is a schematic representation of another control
system for a plurality of compressors using various gateways;
[0026] FIG. 15 is an oil sensor used with the compressor;
[0027] FIG. 16 is another oil sensor used with the compressor;
and
[0028] FIG. 17 is a functional block diagram of the compressor
protection and control subsystem for a semi-hermetic
compressor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0030] Referring now to the drawings in which like reference
numerals designate like or corresponding parts throughout the
several views, there is shown in FIGS. 1 and 2 a scroll compressor
which incorporates the compressor protection and control subsystem
in accordance with the present invention which is designated
generally by reference numeral 10. While the compressor protection
and control subsystem is being illustrated for exemplary purposes
in association with a hermetic scroll compressor, it is within the
scope of the present invention to use the compressor protection and
control subsystem with other rotary compressors also. Compressor 10
comprises a generally cylindrical hermetic shell 12 having welded
at the upper end thereof a cap 14 and at the lower end thereof a
base 16 having a plurality of mounting feet (not shown) integrally
formed therewith. Cap 14 is provided with a refrigerant discharge
fitting 18 which may have the usual discharge valve therein (not
shown). Other major elements affixed to the shell include a
transversely extending partition 22 which is welded about its
periphery at the same point that cap 14 is welded to shell 12, a
main bearing housing 24 which is suitably secured to shell 12, a
lower bearing housing 26 also having a plurality of radially
outwardly extending legs each of which is also suitably secured to
shell 12 and an electrical enclosure 28 (FIG. 2). A motor stator 30
which is generally square in cross-section but with the corners
rounded off is press fitted into shell 12. The flats between the
rounded corners on the stator provide passageways between the
stator and shell, which facilitate the return flow of lubricant
from the top of the shell to the bottom.
[0031] A drive shaft or crankshaft 32 having an eccentric crank pin
34 at the upper end thereof is rotatably journaled in a bearing 36
in main bearing housing 24 and a second bearing 38 in lower bearing
housing 26. Crankshaft 32 has at the lower end a relatively large
diameter concentric bore 40 which communicates with a radially
outwardly inclined smaller diameter bore 42 extending upwardly
therefrom to the top of crankshaft 32. Disposed within bore 40 is a
stirrer 44. The lower portion of the interior shell 12 defines an
oil sump 46 which is filled with lubricating oil to a level
slightly above the lower end of a rotor 48, and bore 40 acts as a
pump to pump lubricating fluid up the crankshaft 32 and into
passageway 42 and ultimately to all of the various portions of the
compressor which require lubrication.
[0032] Crankshaft 32 is rotatively driven by an electric motor
including stator 30, windings 50 passing therethrough and rotor 48
press fitted on the crankshaft 32 and having upper and lower
counterweights 52 and 54, respectively.
[0033] The upper surface of main bearing housing 24 is provided
with a flat thrust bearing surface 56 on which is disposed an
orbiting scroll member 58 having the usual spiral vane or wrap 60
on the upper surface thereof. Projecting downwardly from the lower
surface of orbiting scroll member 58 is a cylindrical hub having a
journal bearing 62 therein and in which is rotatively disposed a
drive bushing 64 having an inner bore 66 in which crank pin 32 is
drivingly disposed. Crank pin 32 has a flat on one surface which
drivingly engages a flat surface (not shown) formed in a portion of
bore 66 to provide a radially compliant driving arrangement, such
as shown in assignee's U.S. Pat. No. 4,877,382, the disclosure of
which is hereby incorporated herein by reference. An Oldham
coupling 68 is also provided positioned between orbiting scroll
member 58 and bearing housing 24 and keyed to orbiting scroll
member 58 and a non-orbiting scroll member 70 to prevent rotational
movement of orbiting scroll member 58. Oldham coupling 68 is
preferably of the type disclosed in assignee's co-pending U.S. Pat.
No. 5,320,506, the disclosure of which is hereby incorporated
herein by reference.
[0034] Non-orbiting scroll member 70 is also provided having a wrap
72 positioned in meshing engagement with wrap 60 of orbiting scroll
member 58. Non-orbiting scroll member 70 has a centrally disposed
discharge passage 74 which communicates with an upwardly open
recess 76 which in turn is in fluid communication with a discharge
muffler chamber 78 defined by cap 14 and partition 22. An annular
recess 80 is also formed in non-orbiting scroll member 70 within
which is disposed a seal assembly 82. Recesses 76 and 80 and seal
assembly 82 cooperate to define axial pressure biasing chambers
which receive pressurized fluid being compressed by wraps 60 and 72
so as to exert an axial biasing force on non-orbiting scroll member
70 to thereby urge the tips of respective wraps 60, 72 into sealing
engagement with the opposed end plate surfaces. Seal assembly 82 is
preferably of the type described in greater detail in U.S. Pat. No.
5,156,539, the disclosure of which is hereby incorporated herein by
reference. Non-orbiting scroll member 70 is designed to be mounted
to bearing housing 24 in a suitable manner such as disclosed in the
aforementioned U.S. Pat. No. 4,877,382 or U.S. Pat. No. 5,102,316,
the disclosure of which is hereby incorporated herein by
reference.
[0035] Referring now to FIG. 3, electrical enclosure 28 includes an
electrical case 84, a compressor protection and control subsystem
86 and a cover 88. Electrical case 84 is mounted to shell 12 using
a plurality of studs 90 (FIG. 2) which are resistance welded to
shell 12. Compressor protection and control subsystem 86 is mounted
within electrical case 84 using a pair of mounting screws 92.
Compressor protection and control subsystem 86 is connected to the
various components of compressor 10 using wiring which has been
omitted from the Figures for purposes of clarity. The connections
for compressor protection and control subsystem 86 will be
discussed in greater detail below. Compressor protection and
control subsystem 86 includes a status display 94 which indicates
the status of protection and control subsystem 86 and thus the
operating status of compressor 10. Cover 88 is attached to
electrical enclosure 84 using a plurality of screws 98. Cover 88
defines an aperture 100 which aligns with status display 94 to
enable an individual to determine the operating status of
compressor 10 without having to remove cover 88. Status display 94
is capable of displaying numbers and some alpha characters to
indicate the various fault codes associated with compressor
protection and control subsystem 86.
[0036] Referring now to FIGS. 4 and 5, a side view of compressor
protection and control subsystem 86 is shown in FIG. 4 and a
functional block diagram of compressor protection and control
subsystem 86 is shown in FIG. 5. Compressor protection and control
subsystem 86 includes status display 94 as well as terminals 102
through 136 some of which are connected to internally integrated
sensors which are in turn connected to a control block 138.
Terminals 102 and 104 are connected to a high pressure cut off
switch 140 and a low pressure cut off switch 142 through an
isolated pressure switch sensing monitor 144. High pressure cut off
switch 140 will notify compressor protection and control subsystem
86 of a higher than acceptable pressure reading for compressor 10
and low pressure cut off switch 142 will notify compressor
protection and control subsystem 86 of a lower than acceptable
pressure reading for compressor 10.
[0037] Terminal 106 is connected to a pressure sensor 146 which
monitors the discharge pressure of compressor 10. Terminal 108 is
connected to a pressure sensor 148 which monitors the suction
pressure of compressor 10. Terminal 110 is connected to a
temperature sensor 150 which monitors the temperature of the
discharge gas of compressor 10. Terminal 112 is connected to an oil
level sensor 152 which monitors the oil level sump 46 of compressor
10. Input from sensors 146-152 are connected to terminals 106-112,
respectively, through an analog to digital converter 154 prior to
being input to control block 138.
[0038] Terminals 114, 116, and 118 are connected to a first, a
second and a third phase wiring, 156-160, for compressor 10 in
order to monitor the status of the three-phase power supply for
compressor 10. Wirings 156-160 are connected to control block 138
and terminals 114-118 through an isolation and signal conditioner
162. Terminals 120 and 122 are connected to a group of motor
temperature sensors 164 through a PTC Input circuit 166. Terminal
124 is connected to a compressor control system 168 which indicates
that all monitored systems are acceptable and compressor 10 is free
to operate.
[0039] Vibration detection can be added to compressor protection
and control subsystem 86 by incorporating a preferred vibration
sensor 180 within compressor protection and control subsystem 86 as
shown in dashed lines in FIG. 4. Vibration sensor 180 is shown in
FIGS. 6 and 7 and it comprises a cover 182, a contractor ring 184,
a terminal rod 186, a spring wire 188, a ball 190, and an end cap
192. Cover 182 is a generally rectangular shaped plastic component
defining a internal circular bore 194. Contractor ring 184 is fit
within an enlarged portion of bore 194 and rests against a shoulder
196 formed by bore 194. Terminal rod 186 extends through a side
wall of cover 182. Terminal rod 186 is welded to contractor ring
184 such that the end of terminal rod 186 extending through cover
182 can be utilized as a solder point for vibration sensor 180.
[0040] Spring wire 188 is an L-shaped wire member which has one end
of the L extending through the side wall of cover 182 and the
opposite end of the L extending axially down the center line of
circular bore 194 such that the end of spring wire 188 terminates
in approximately the center of contractor ring 184. Ball 190
includes a radially extending bore 198 which extends from the outer
surface of ball 190 to approximately the center of ball 190.
Preferably, ball 190 and spring wire 188 are assembled by inserting
spring wire 188 into bore 198 and applying a strong permanent epoxy
or by other methods known well in the art. The end of spring wire
188 which extends out of cover 182 is used as a solder point for
vibration sensor 180. End cap 192 is attached to cover 182 by use
of a permanent set epoxy which seals bore 194 and thus protects the
electrical contacts of vibration sensor 180.
[0041] Preferably, spring wire 188 is made from spring quality
steel or music wire, ball 190 is made form stainless steel (either
302 or 304) and contractor ring 184 is made from a seamless 304
stainless steel hollow tubular stock. Contractor ring 184 and ball
190 are preferably plated with gold up to a thickness of 0.000015
inches to prevent oxidation. In the preferred method of
fabricating, spring wire 188 and contractor ring 184 are molded in
place. Ball 190 is then secure to spring wire 188 and then end cap
192 is assembled.
[0042] Ball 190 and spring wire 188 comprise a simple spring-mass
system. Spring wire 188 has the dual purpose of serving as one
electrical terminal and also to act as the stiffness member of the
spring-mass system. Vibration sensor 180 is located on the circuit
board for compressor protection and control subsystem 86 and is
most sensitive to vibration in the plane which is perpendicular to
the long axis of vibration sensor 180 or the long axis of spring
wire 188. Sensor 180 is actually a form of electrical switch which
requires a minimum displacement before the momentary circuit
closures or pulses begin to appear. A sensor input network block
includes an RC filter which reduces the noise content of the
signal.
[0043] In a given orientation, the response of vibration sensor 180
is governed by the stiffness of spring wire 188 and the mass of
ball 190. System response is measured in terms of the amplitude of
oscillations of ball 190 when vibration sensor 180 is attached to
compressor 10. In principle, sensor 180 is designed to have a
natural frequency close to the operating frequency of compressor
10. Preferably the natural frequency of sensor 180 is maintained on
the higher side of the operating frequency of compressor 10 to
eliminate nuisance trips. By controlling parameters such as the
stiffness of spring wire 188, the mass of ball 190 and the gap
between ball 190 and contractor ring 184, it is possible to design
sensor 180 to trigger only above a specific value of input
vibration. In this context, triggering is said to occur when ball
190 contacts ring 184. The stiffness of spring wire 188 is a
function of the diameter, length and material of spring wire 188,
the mass of ball 190 is a function of its material and its
diameter. Thus, by making variations in these parameters, it is
possible to change the response curve of sensor 180. The
sensitivity of sensor 180 is determined by the gap between ball 190
and contact ring 184 and how close the natural frequency of sensor
180 is to the operating frequency of compressor 10. If the two
frequencies are close, the system may be over sensitive; i.e. a
small change in input vibration amplitude will result in a
significant change in output vibration of movement of ball 190.
Similarly, if the two frequencies are far apart, the system may be
under sensitive and require a larger input vibration amplitude to
cause a small change in output vibration or movement of ball 190.
Computer studies and parallel experimental work has determined that
a preferred sensor 180 will trigger at input signal levels of 10-15
mils of input vibration. This preferred design is insensitive to
input vibration under 8 mils.
[0044] One issue which needs to be addressed with vibration sensor
180 is it must have the ability to distinguish between a true
excessive vibration condition and the normal transient vibrations
experienced during start up, flooded start, shut down and the like.
Compressor protection and control subsystem module 86 preferably
includes a first counter which continuously counts any pulses or
triggering that are present using a 10 second time interval. If the
number of pulses counted during any 10 second interval exceeds a
predetermined number, a limit condition flag is turned on.
Conversely, if the number of pulses counted during any 10 second
interval is less than a predetermined number, the limit condition
flag is turned off. Compressor protection and control subsystem 86
implements a second counter which is an up-down counter. It is
clocked by an internal 1 second clock. The counter is limited to 0
counts in the down direction and 120 counts in the up direction. If
the condition limit flag is turned on, the counter counts up. If
the limit condition flag is turned off, the counter counts down. If
at any time the count reaches 120, control and protection module 86
turns off the control relay and sets status display 94 to indicate
a "vibration trip condition". Recycling of power to compressor
protection and control subsystem 86 is required to clear this
condition and reset the counter to 0.
[0045] Control block 138 of compressor protection and control
subsystem 86 can also be used to control other various and perhaps
optional systems incorporated into compressor 10. Terminal 126 is
designed to be connected to a solenoid control system 210 which in
turn is connected to an unloading control for a compressor for
controlling the capacity of a compressor 214 shown in FIG. 8.
Compressor 214 is identical to compressor 10 except for the
incorporation of a capacity control system 216 which is controlled
by control block 138.
[0046] Terminal 128 is designed to be connected to a solenoid
control system 218 which is, in turn, connected to a liquid
injection system 222 for controlling the liquid injection for a
compressor 224 shown in FIG. 9. Compressor 224 is identical to
compressor 10 except for the incorporation of liquid injection
system 222.
[0047] Terminal 130 is designed to be connected to a solenoid
control system 226 which is, in turn, connected to an oil injection
system 230 for controlling oil injection for a compressor 234 shown
in FIG. 10. Compressor 234 is identical to compressor 10 except for
the incorporation of oil injection system 230.
[0048] Terminal 132 is designed to be connected to a heater control
system 236 which is, in turn, connected to a crankcase heater 238
for heating the lubricating oil in sump 46 of compressor 10 as
shown in FIG. 1.
[0049] While FIGS. 8-10 each show a separate system added to
compressor 10, it is within the scope of the present invention to
include one or more of systems 216, 222 or 230 if desired.
[0050] Communication with control block 138 of compressor
protection and control subsystem 86 is provided by a communication
interface or gateway 250 which communicates with control block 138
through terminals 134 and 136. DC voltage to power the various
sensors is provided a power supply system 252. Gateway 250 uses
Motorola's Serial Peripheral Interface (SPI) for communicating with
bridge or gateway modules. Motorola's SPI was designed to allow
communications between a microcontroller and integrated circuits on
a board providing expanded peripheral functions. Another bus, the
I.sup.2C is similar to the SPI and was developed by
Signetics/Philips Semiconductor. By using one of these buses, the
only hardware required for connection to a pluggable gateway board
is a suitable connector. By taking this approach, the system
communications protocol is limited only by the gateways made
available.
[0051] The SPI and I.sup.2C are the lowest cost approaches to
providing communications and all that is needed is an adapter or a
gateway. The preferred embodiment uses a serial interface using
RS-485. The protocol used by the advanced compressor control and
protection system of the present invention for either the simple
SPI-to-gateway communications or in the case of an RS-485 based
local network application is a master-slave protocol. The system
control is the master when the local RS-485 interface is used. If
another protocol is required, the gateway module acts as the master
on the compressor control interface side.
Node Address Assignments
[0052] There are 32 node addresses to specify the target node.
Address 0 is reserved for master broadcast messages. Address 31 is
reserved for messages to the bus master. The remaining addresses
are available for slave nodes. The Node Address is contained in the
five most significant bits of Byte 0.
Message Types
[0053] The message type is contained in the least significant three
bits of Byte 0. Eight message types are defined as follows:
[0054] 1. Slave Status Request--This message is used by the system
master to interrogate a slave node for its status. The addressed
slave responds with one or more Status Reply messages. This message
has a packet length of zero (0).
[0055] 2. Status Reply--This message is used by slave nodes as a
reply to Slave Status Request messages from the system master.
[0056] 3. Control Commands--A Command Control message is used to
control the actuator outputs of a slave node. Packet zero (0) of
this message type is always a single byte and is used as a hardware
reset command. All bits set to 1's generate a hardware reset in the
slave node.
[0057] 4. Configuration Request--The Configuration Read message is
used by the system master to command a slave node to send its
configuration data by means of one or more data packets contained
in Configuration Data messages. This message has a packet length of
zero (0).
[0058] 5. Configuration Data--The Configuration Data message is
used to send data packets containing the slave node's configuration
data when the slave node has received a Configuration Read message.
This is typically data stored in the slave node's EEROM of Flash
Memory storage. It causes information which identifies the node
type, serial number, date of manufacture, event histories, etc.
[0059] 6. Sensor Read Request--The Sensor Read message is sent by
the system master to command the slave node to send its sensor
data. This message has a packet length of zero (0).
[0060] 7. Sensor Data--This message type is sent by a slave node in
response to the Sensor Read message from the system master.
[0061] 8. Receipt Response--The Receipt Response message is sent by
a slave node in response to messages from the system master which
do not require data to be returned. This data packet is always a 1
byte ACK or NAK.
Packet Number
[0062] A message type may have up to 8 packets. Each packet may be
1 to 32 bytes in length and is sent in a separate message. The
first message sent has the packet number set to the number of
packets to be sent. Each subsequent message has the packet number
decremented. The last message contains the last packet to be sent
and is packet number zero (0).
[0063] The packet Number is contained in the most significant 3
bits of Byte 1.
Packet Length
[0064] The Packet Length specifies the length of the Data Packet in
each message. The Packet Length is contained in the least
significant 5 bits of Byte 1. Each message contains a data packet
with up to 31 data bytes. The only exception is a packet length of
zero (0) bytes. In this case there is no data packet in the
message.
Node Types
[0065] Node definitions can be created for any component in a
system that is capable of supporting communications. A good example
would be a refrigeration case control. Or if partitioning of the
system is desired, node definitions for individual or groups of
sensors and actuators would make sense. These definitions would
define the specific messages and their content as required for the
particular devices. This document release focuses on the compressor
node only.
Compressor Node
[0066] The compressor node utilizes all message types available.
The Configuration data message type 5 is used to transfer the
compressor configuration data between the system master and each
compressor node. The compressor is shipped with the data
preconfigured. The system master may send a Configuration Request
to a selected compressor node and get an image of the stored data.
It may modify that data or it may construct a completely new image
and send it to the compressor for storage by sending it in the
appropriate series of Configuration Data packets. Typical
configuration variables are listed below.
Configuration Data List
[0067] Compressor Information
[0068] Compressor Model Code
[0069] Compressor Serial Number
[0070] Application
[0071] Application Temperature Range
[0072] Refrigerant Code
[0073] Oil Code
[0074] Oil Charge
[0075] Customer Information
[0076] Customer Name
[0077] Customer Model Number
[0078] Control Configuration
[0079] Anti Short Cycle Time
[0080] Discharge Pressure Cut-in
[0081] Discharge Pressure Cut-out
[0082] Discharge Pressure Sensor Option Enabled
[0083] Discharge Trip Time
[0084] Discharge Multiplier
[0085] Discharge Divider
[0086] Discharge Temperature Cut-out
[0087] Oil Add Set Point
[0088] Oil Stop Add Set Point
[0089] Oil Trip Set Point
[0090] Oil On Time
[0091] Oil Off Time
[0092] Oil Add Period
[0093] Shake Limit (pulses/10 second period.)
[0094] Shake Count (number of periods)
[0095] Suction Pressure Low Limit
[0096] Suction Pressure High Limit
[0097] Suction Multiplier
[0098] Suction Divider
[0099] Suction Pressure Sensor Option
[0100] Additional information in the Configuration Data category is
certain history information as listed below.
[0101] Event History
[0102] Compressor Cycles
[0103] Compressor On Time
[0104] Discharge Pressure Trips
[0105] Discharge Temperature
[0106] Motor Trips
[0107] Oil Trips
[0108] Suction Pressure Limit Trips
[0109] Shake Limit Trips
[0110] Events Since Cleared
[0111] Using the above described protocol, some typical sensor data
which would be sent in response to a sensor data request would be
as detailed below.
[0112] Anti Short Cycle Time--32 bit unsigned (mS)
[0113] Discharge Pressure Cut-in--32 bit signed (up to 6553.5 kPa,
res. 0.1 kPa)
[0114] Discharge Pressure Cut-out--32 bit signed (up to 6553.5 kPa,
res. 0.1 kPa)
[0115] Discharge Trip Time--16 bit unsigned (res. 0.01 S)
[0116] Discharge Multiplier--32 bit unsigned
[0117] Discharge Divider--32 bit unsigned
[0118] Suction Pressure Cut-in--32 bit signed (+,-3276.7 kPa, res.
0.1 kPa)
[0119] Oil Stop Add--16 bit unsigned
[0120] Suction Pressure Cut-out--32 bit signed (+,-3276.7 kPa, res.
0.1 kPa)
[0121] Suction Multiplier--32 bit unsigned
[0122] Suction Divider--32 bit unsigned
[0123] Oil Add--16 bit unsigned
[0124] Oil Trip--16 bit unsigned
[0125] Oil On Time 32 bit unsigned (mS)
[0126] Oil Off Time--32 bit unsigned (mS)
[0127] Oil Add Period--16 bit unsigned (0.01 S)
[0128] Vibration Limit--16 bit unsigned--pulses/10 s
[0129] Vibration Count--8 bit unsigned--10 s periods
[0130] Referring now to FIG. 11, compressor 10 is illustrated
showing the Serial Peripheral Interface (SPI) for connecting
compressor protection and control subsystem 86 of compressor 10 to
a central control system 254. Using the SPI interface and the
gateway, subsystem 86 of compressor 10 can be controlled by and
communicate with a master network. The connection and communication
with the master network is preferably through LonWorks but other
network connections such as SPi, CANBus, Device Net,
Internet/intranet, BAC net or a Proprietary connection can be
established. FIG. 12 illustrates the network system when a
centralized rack gateway 256 is utilized to communicate with a
group of compressors 10, FIG. 13 illustrates the network system
when a rack/system control 258 acts as the gateway for
communicating with a group of compressors 10 and FIG. 14
illustrates the network system when an Internet web server 260 or a
local Intranet server 262 is utilized to communicate with
individual Ethernet gateways associated with each compressor
10.
[0131] One problem associated with the development of the advanced
compressor control and protection system was an accurate oil level
sensor applicable to compressors. The requirements for the sensor
included that it have no moving parts, that it be compatible with
the environment of the interior of the compressor in the sump and
that its costs be competitive with current day float based sensors.
Two concepts were deemed to have merit. First, self-heated
thermistor with temperature compensation had the potential to be
simple, reliable and low cost and second, capacitance was
considered as a potentially reliable, accurate and low cost
approach as well.
[0132] A capacitance based sensor 300 shown in FIG. 15 is one
option for an oil sensor. There is a large enough dielectric
constant of oil versus refrigerant gas to be able to derive a
usable signal. The volume construction of such a device having a
consistent capacitance from unit to unit without calibration is
feasible if the electrodes are arranged coaxially. Sensor 300 is
comprised of a hollow stainless tube 302 with a small coaxially
positioned rod 304.
[0133] A multiple thermocouple liquid level sensor 320 is shown in
FIG. 16. Sensor 320 comprises an unevenly heated thermocouple array
322. Sensor 320 requires a compensation for the effect of different
gas densities by using a separate unevenly heated thermocouple pair
which is always disposed within the suction gas of the compressor.
A mathematical model was developed using the output from the
thermocouple disposed in the gas to correct the output of the
thermocouple disposed in the lubricant for variation pressure and
temperature of the suction gas over the compressor's operating
envelope.
[0134] Referring now to FIG. 17, a system schematic for a
compressor protection and control subsystem 86' for use with a
semi-hermetic rotary compressor is disclosed. Subsystem 86', shown
in FIG. 17, is similar to subsystem 86 shown in FIG. 5 except for
the addition of control for an oil switch 300. A semi-hermetic
rotary compressor is similar to a hermetic rotary compressor except
that the shell for the semi-hermetic rotary compressor is bolted
together rather than being welded as shown for shell 12. in
addition, the semi-hermetic rotary compressor is typically equipped
with a positive displacement lubricant pump which maintains an oil
pressure within the lubrication system for the semi-hermetic rotary
compressor. A pressure sensor monitors the pressure for the
lubrication system with the pressure sensor communicating with
control block 138 through a pair of terminals 302 and 304. Logic
within control block 138 monitors the lubrication after lubrication
pressure is determined to be low or inadequate for a specified
period of time. The time delay used for controlling the compressor
for a lack of sufficient oil pressure avoids problems associated
with mis-trips caused to varying oil pressure. The function and
operation of the remainder of compressor protection and control
subsystem 86' is the same as that described above for compressor
protection and control subsystem 86.
[0135] While the above detailed description describes the preferred
embodiment of the present invention, it should be understood that
the present invention is susceptible to modification, variation and
alteration without deviating from the scope and fair meaning of the
subjoined claims.
* * * * *