U.S. patent application number 09/966827 was filed with the patent office on 2003-04-03 for vibration detection in a transport refrigeration system through current sensing.
Invention is credited to Sullivan, Dennis Wayne.
Application Number | 20030061825 09/966827 |
Document ID | / |
Family ID | 25511912 |
Filed Date | 2003-04-03 |
United States Patent
Application |
20030061825 |
Kind Code |
A1 |
Sullivan, Dennis Wayne |
April 3, 2003 |
VIBRATION DETECTION IN A TRANSPORT REFRIGERATION SYSTEM THROUGH
CURRENT SENSING
Abstract
A current sensor positioned on a power line monitors current
draw associated with an electrical motor driven shaft based device,
such as a scroll compressor. Mechanical vibrations in the scroll
compressor force stress on the motor shaft of the scroll
compressor, directly influencing current draw. By monitoring
current draw, vibrations resulting from problems in the compressor,
such as a broken mounting bracket, can be detected. A controller
receives the current values and indicates if a current value
exceeds a threshold current value or if a plurality of current
values exceed a threshold value.
Inventors: |
Sullivan, Dennis Wayne;
(Elbridge, NY) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD
SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
25511912 |
Appl. No.: |
09/966827 |
Filed: |
September 28, 2001 |
Current U.S.
Class: |
62/126 ;
62/230 |
Current CPC
Class: |
F04C 23/008 20130101;
F25B 2700/151 20130101; F04C 28/28 20130101; F25B 1/04 20130101;
F04C 18/0215 20130101; B60H 1/3225 20130101; F25B 49/005
20130101 |
Class at
Publication: |
62/126 ;
62/230 |
International
Class: |
F25B 049/00; F25B
001/00 |
Claims
What is claimed is:
1. A refrigeration system comprising: a compressor, a condenser, an
evaporator and an expansion device for circulating a refrigerant;
and at least one sensor used to sense at least one system value
representative of a level of vibration in a component of said
refrigeration system.
2. The refrigeration system as recited in claim 1 wherein said
compressor is a scroll compressor.
3. The refrigeration system as recited in claim 1 wherein said
component is said compressor.
4. The refrigeration system as recited in claim 3 wherein said
system value is a current value being delivered to a motor of said
compressor.
5. The refrigeration system as recited in claim 4 wherein said
compressor is mounted to a container unit by a mounting bracket,
said at least one current sensor sensing an increase in said at
least one current value and said level of vibration when said
mounting bracket is broken.
6. The refrigeration system as recited in claim 1 further including
a controller which receives said at least one system value, and
said system value is a current value.
7. The refrigeration system as recited in claim 6 wherein said
controller indicates when said at least one current value exceeds a
threshold current value.
8. The refrigeration system as recited in claim 6 wherein said
controller indicates when a plurality of said at least one current
value exceeds a threshold current value in a timeframe.
9. The refrigeration system as recited in claim 1 wherein said
refrigeration system is incorporated into a transport refrigeration
unit.
10. The refrigeration system as recited in claim 1 wherein said
component is an electrical motor driven shaft based device.
11. A transport refrigeration system comprising: a compressor to
compress a refrigerant to a high pressure, said compressor being
provided with an electric current to drive a motor of said
compressor; a heat rejecting heat exchanger for cooling said
refrigerant; an expansion device for reducing said refrigerant to a
low pressure; a heat accepting heat exchanger for evaporating said
refrigerant; a refrigeration container for being cooled by said
heat accepting heat exchanger; and at least one current sensor to
sense at least one current value representative of a level of
vibration being delivered to said compressor motor.
12. The transport refrigeration system as recited in claim 11
wherein said compressor is a scroll compressor.
13. The transport refrigeration system as recited in claim 11
wherein said at least one current value is current draw associated
with said compressor.
14. The transport refrigeration system as recited in claim 11
wherein said compressor is mounted to a container unit by a
mounting bracket, said at least one current sensor sensing an
increase in said at least one current value and said level of
vibration when said mounting bracket is broken.
15. The transport refrigeration system as recited in claim 11
further including a controller which receives said current
value.
16. The transport refrigeration system as recited in claim 15
wherein said controller indicates when said at least one current
value exceeds a threshold current value.
17. The transport refrigeration system as recited in claim 15
wherein said controller indicates when a plurality of said at least
one current value exceeds a threshold current value in a
timeframe.
18. The transport refrigeration system as recited in claim 11
wherein said component is an electrical motor driven shaft based
device.
19. A method for monitoring operation of a refrigeration system
comprising the steps of: (1) providing a refrigerant cycle
including a compressor, a heat accepting heat exchanger, an
expansion device and a heat rejecting heat exchanger, supplying
electric current to a motor for driving said compressor; (2)
monitoring a current draw to said compressor motor, and detecting
when said current draw exceeds predetermined conditions; and (3)
identifying undue vibration is said compressor when said monitored
current exceeds said predetermined value in step (2).
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to a transport
refrigeration system employing a current sensor used to detect
unacceptably high levels of mechanical vibrations associated with
an electrical motor drive shaft based device, such as a scroll
compressor.
[0002] A current sensor positioned on a power line leading to a
system component in a transport refrigeration product monitors
current in the component. In prior transport refrigeration
products, the current sensor monitors current to determine system
operation states and to perform self-diagnostic tests to determine
if a system component is working properly. If a component is not
working properly or is turned off, the system current is less than
what the system current would be if the component is working
properly or is turned on. When the current sensor detects this, the
current values are displayed on a display/keypad interface to
indicate the system operating state to the system user.
[0003] Vibration within a compressor can be indicative of a problem
with the compressor or with the overall refrigeration system. To
date, there has been no simple and effective way of identifying
undue levels of vibration. As an example, problems within the
compressor, such as a broken mounting bracket, can result in
mechanical vibrations increasing to high levels. It would be
desirable that a warning signal be sent in the event that such
levels are occurring.
[0004] Problems such as mentioned above are particularly desirable
detected early on in transport refrigeration systems. A transport
refrigeration system is typically utilized on a vehicle
transporting refrigerated cargo, such as frozen foods and
perishable cargo. If this system is associated with a failing
compressor, the entire cargo could be lost.
SUMMARY OF THE INVENTION
[0005] Applicant has recognized that high vibration in an
electrical motor driven shaft based device will result in
detectable current peaks. The present invention relates to a
transport refrigeration system employing a current sensor used to
detect unacceptably high levels of mechanical vibrations associated
with an electrical motor driven shaft based device, and in
particular a compressor employed as part of a transport
refrigeration system.
[0006] A power source supplies power to the compressor of a
transport refrigeration system. A current sensor positioned on at
least one of the power line legs monitors current draw associated
with the compressor. Compressor vibrations force stress on the
compressor motor shaft, directly influencing the current draw. As
vibrations in the compressor increases, the current draw associated
with the compressor increases. By monitoring the current draw
associated with the compressor, unacceptably high levels of
mechanical vibrations resulting from problems in the compressor,
such as a broken mounting bracket, can be detected.
[0007] The current values monitored by the current sensor are
received by a controller. If the current sensor detects a current
value exceeding a threshold current value, the controller indicates
that the compressor is undergoing excess vibrations. Alternatively,
the controller indicates when the current sensor detects a
plurality of current peaks exceeding a threshold current value in a
time frame. A warning signal or corrective action can then be
taken.
[0008] Accordingly, the present invention provides a transport
refrigeration system employing a current sensor used to detect
unacceptably high levels of mechanical vibrations associated with a
compressor. Preferably, the system is utilized with a scroll
compressor used in a transport refrigeration system.
[0009] These and other features of the present invention will be
best understood from the following specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The various features and advantages of the invention will
become apparent to those skilled in the art from the following
detailed description of the currently preferred embodiment. The
drawing that accompany the detailed description can be briefly
described as follows:
[0011] FIG. 1 illustrates a schematic diagram of a refrigerant
cycle;
[0012] FIG. 2 illustrates a schematic diagram of a scroll
compressor utilized in a transport refrigeration system including a
current sensor to detect current draw associated with the scroll
compressor.
[0013] FIG. 3 illustrates a graphic illustration of current values
which exceed a predetermined current value; and
[0014] FIG. 4 illustrates a graphic illustration of a predetermined
number of current peaks exceeding a predetermined current value in
a predetermined time frame.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] FIG. 1 schematically illustrates a refrigeration cycle 20.
The refrigeration cycle 20 consists of a compressor 22, a heat
rejecting heat exchanger (a condenser) 24, an expansion device 26,
and a heat accepting heat exchanger (an evaporator) 28.
[0016] Refrigerant is circulated though the closed circuit
refrigeration cycle. The refrigerant exits the compressor 22 at
high pressure and enthalpy. As the refrigerant flows through the
condenser 24 at high pressure, it loses heat and enthalpy, exiting
the condenser 24 with low enthalpy and high pressure. As the
refrigerant passes through the expansion device 26, the pressure of
the refrigerant drops. After expansion, the refrigerant passes
through the evaporator 28 and exits at a high enthalpy and low
pressure. After the refrigerant passes through the compressor 22,
it is again at high pressure and enthalpy, completing the
refrigeration cycle 20. As shown schematically, the refrigerant
cycle 20 is preferably included as part of a transport
refrigeration system, such as commonly utilized to cool a
transported refrigerated container 29. As is known, such systems
are typically incorporated into containers carried by trucks,
ships, rail, or other sources, to transport perishable and frozen
goods, such as frozen food.
[0017] As shown schematically in FIG. 2, the compressor 22 is
secured by a mounting bracket 30 to the transport container 29.
Although a compressor 22 is disclosed, it is to be understood that
any electrical motor driven shaft based device can be employed. The
compressor 22 is preferably a scroll compressor driven by a power
source 36. Three power line legs 38A, 38B, and 38C supply "three
phase power" from the power source 36 to the scroll compressor 22.
Although a three phase power supply is illustrated and described,
it is to be understood that this invention would extend to single
phase power.
[0018] A current sensor 40 monitors the current in power line leg
38A. However, it is to be understood that two or all of the power
leg lines 38A, 38B and 38C can be monitored by current sensors 40.
Preferably, the current sensor 40 includes a resistor 44 and an
internal coil 42. However, other types of current sensors 40 can be
used.
[0019] There is a direct relationship between the current draw
associated with the scroll compressor 22 and the mechanical
vibrations within the compressor 22. Compressor 22 problems, either
external or internal, apply vibration on the motor shaft 48 of the
compressor 22, increasing current draw associated with compressor
22. For example, a broken mounting bracket 30 results in vibrations
on the shaft 48 of the compressor 22, increasing the current drawn
on the compressor 22. By monitoring the current draw with a current
sensor 40, problems such as a broken mounting bracket 30 can be
detected.
[0020] The current values monitored by the current sensor 40 are
received by a controller 46. As shown in FIG. 3, if the current
sensor 40 detects a current value greater than a threshold current
value of X amps, the controller 46 indicates this to a user, such
as by signal 50. As illustrated, the controller 46 indicates excess
vibrations at points 1, 2 and 3. The current threshold value X is
dependent on the system requirements. Alternatively, as illustrated
in FIG. 4, if the current sensor 40 detects a plurality of current
values above threshold current value X amps in time frame Y
seconds, the controller 46 indicates this to a user. In the
illustrated embodiment, 6 readings higher than X amps in Y seconds
is an indication of excess vibrations. The predetermined amount and
intensity of the current values depend on the system
requirements.
[0021] The transport refrigeration system of the present invention
including a current sensor 40 for detecting vibrations can be used
with any transport refrigeration system, including ships, trains,
trailers and trucks. Even though it is disclosed that the current
sensor 40 detects current, and thus vibrations, in the compressor
22, it is to be understood that the current sensor 40 can detect
vibrations in other components of the transport refrigeration
system. The current sensor 40 can be utilized in any electrical
motor driven shaft based device. Further, while it is current which
identifies the vibrations, it should be understood that other
characteristics within the operation of the compressor could be
indicative of vibration and could be sensed and utilized to
identify undue vibration in accordance with the teaching of this
invention.
[0022] The foregoing description is only exemplary of the
principles of the invention. Many modifications and variations of
the present invention are possible in light of the above teachings.
The preferred embodiments of this invention have been disclosed,
however, so that one of ordinary skill in the art would recognize
that certain modifications would come within the scope of this
invention. It is, therefore, to be understood that within the scope
of the appended claims, the invention may be practiced otherwise
than as specially described. For that reason the following claims
should be studied to determine the true scope and content of this
invention.
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