U.S. patent application number 11/010851 was filed with the patent office on 2006-06-15 for air compressor control.
This patent application is currently assigned to Bendix Commercial Vehicle Systems LLC. Invention is credited to David J. Pfefferl, Roger L. Sweet.
Application Number | 20060127224 11/010851 |
Document ID | / |
Family ID | 35789245 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127224 |
Kind Code |
A1 |
Sweet; Roger L. ; et
al. |
June 15, 2006 |
Air compressor control
Abstract
Controlling air compressors based on a temperature of air
compressed by the air compressor. A temperature of air compressed
by the air compressor is sensed. The sensed compressed air
temperature is compared with a predetermined threshold temperature.
The air compressor is deactivated when the sensed temperature
exceeds the threshold temperature. The threshold temperature may be
selected to inhibit carbon formation caused by oil thermal
breakdown.
Inventors: |
Sweet; Roger L.; (Berlin
Heights, OH) ; Pfefferl; David J.; (Broadview
Heights, OH) |
Correspondence
Address: |
CALFEE HALTER & GRISWOLD, LLP
800 SUPERIOR AVENUE
SUITE 1400
CLEVELAND
OH
44114
US
|
Assignee: |
Bendix Commercial Vehicle Systems
LLC
|
Family ID: |
35789245 |
Appl. No.: |
11/010851 |
Filed: |
December 13, 2004 |
Current U.S.
Class: |
417/32 |
Current CPC
Class: |
F04B 2205/10 20130101;
F04B 2205/05 20130101; F04B 49/065 20130101 |
Class at
Publication: |
417/032 |
International
Class: |
F04B 49/10 20060101
F04B049/10 |
Claims
1. A method of controlling an air compressor, comprising: a)
sensing a temperature of air compressed by an air compressor; b)
comparing a sensed temperature of compressed air with a
predetermined threshold temperature; c) deactivating the air
compressor when the sensed temperature exceeds the threshold
temperature.
2. The method of claim 1 wherein the temperature of air compressed
by the air compressor is sensed in a compressor port.
3. The method of claim 1 wherein the temperature of air compressed
by the air compressor is sensed at a compression chamber.
4. The method of claim 1 wherein the temperature of air compressed
by the air compressor is sensed by a temperature sensor mounted in
a compressor unloader valve that is in fluid communication with a
compression chamber.
5. The method of claim 1 wherein the threshold temperature is
selected to inhibit carbon formation caused by oil breakdown.
6. The method of claim 1 wherein the air compressor is deactivated
by bypassing a governor.
7. The method of claim 1 wherein the air compressor is deactivated
by providing a shutdown air control signal to the compressor when
the sensed temperature exceeds the threshold temperature.
8. An apparatus for sensing a temperature of air compressed by an
air compressor, comprising: a) a valve assembly for selectively
opening and closing a passage to a compression chamber; and b) a
temperature sensor supported by a component of the valve assembly
for sensing a temperature of air in the valve assembly.
9. The apparatus of claim 8 wherein the valve assembly is an
unloader control valve assembly.
10. An air compressor, comprising: a) a housing; b) a head mounted
to the housing such that the head and the housing define a
compression chamber and a fluid passage in communication with the
compression chamber; c) a piston disposed in the compression
chamber for compressing air in the compression chamber; and d) a
temperature sensor positioned to measure a temperature of air
compressed by the piston.
11. The air compressor of claim 10 wherein the temperature sensor
is substantially isolated from the head and the housing.
12. The air compressor of claim 10 wherein the temperature sensor
is disposed in the fluid passage.
13. The air compressor of claim 10 further comprising a valve
assembly disposed in the fluid passage, wherein the temperature
sensor is supported by a component of the valve assembly.
14. The air compressor of claim 10 further comprising an unloader
control valve assembly disposed in the fluid passage, wherein the
temperature sensor is supported by a component of the unloader
valve assembly.
15. An air compressor controller, comprising: a) an input for
receiving compressor air temperature signals; b) a comparing
component for comparing the air temperature signals with a
threshold temperature signal value; c) an output that provides an
air compressor deactivation signal when the compressor air
temperature signal exceeds the threshold temperature signal
value.
16. The air compressor controller of claim 15 wherein the comparing
component is defined by circuitry of a microprocessor.
17. The air compressor controller of claim 15 wherein the comparing
component comprises a temperature to voltage converter component
and a voltage comparator.
18. An air compressor controller, comprising: a) an input for
receiving compressor air temperature signals; b) memory for storing
a compressor control algorithm; c) a processor for applying the
compressor control algorithm to the compressor air temperature
signals, wherein the processor provides an air compressor
deactivation signal when the compressor air temperature signal
exceeds the threshold temperature signal value; d) an output for
communicating the compressor deactivation signal to deactivate the
compressor.
19. The controller of claim 18 wherein the threshold temperature is
selected to inhibit carbon formation caused by oil breakdown.
20. A controller for an air compressor, comprising: a) an input for
receiving compressor air temperature signals; b) an input for
receiving reservoir air pressure signals; c) a temperature to
voltage converter component that converts compressor air
temperature signals to voltage signals; d) a pressure to voltage
converter component that converts air pressure signals to voltage
signals; and e) a voltage comparator component that provides a
deactivation signal when voltage signals provided to the voltage
comparator by the temperature to voltage converter component and
the pressure to voltage converter component are outside threshold
limits.
21. A method of controlling an air compressor, comprising: a)
sensing a pressure of compressed air in a reservoir; b) comparing a
sensed pressure of the compressed air in the reservoir with a
predetermined threshold pressure; c) activating the air compressor
when the compressed air in the reservoir is less than the threshold
pressure; d) sensing a temperature of air compressed by the air
compressor; e) comparing a sensed temperature of the air compressed
by the air compressor with a predetermined threshold temperature;
and f) deactivating the air compressor when the sensed temperature
exceeds the threshold temperature and the sensed pressure is above
the threshold pressure.
22. The method of claim 21 further comprising comparing the sensed
pressure of compressed air in the reservoir with a predetermined
control pressure that is greater than the threshold pressure and
deactivating the air compressor when the sensed temperature exceeds
the threshold temperature and the sensed pressure is above the
threshold pressure.
23. The method of claim 21 wherein the temperature of the air
compressed by the air compressor is sensed in a compressor outlet
port.
24. The method of claim 21 wherein the temperature of the air
compressed by the air compressor is sensed at a compression
chamber.
25. The method of claim 21 wherein the temperature of the air
compressed by the air compressor is sensed by a temperature sensor
mounted in a compressor unloader valve that is in fluid
communication with a compression chamber.
26. The method of claim 21 wherein the threshold temperature is
selected to inhibit carbon formation caused by oil thermal
breakdown.
27. An air compressor controller, comprising: a) an input for
receiving compressor air temperature signals and reservoir pressure
signals; b) memory for storing a compressor control algorithm; c) a
processor for applying the compressor control algorithm to the
compressor air temperature signals and the reservoir pressure
signals, wherein the processor provides an air compressor
activation signal when the compressed air in the reservoir is less
than a predetermined threshold pressure and provides an air
compressor activation signal when the sensed temperature exceeds
the threshold temperature and the sensed pressure is above the
threshold pressure; and d) an output for communicating the
compressor activation signal and the compressor deactivation signal
to control the compressor.
28. The controller of claim 27 wherein the threshold temperature is
selected to inhibit carbon formation caused by oil breakdown.
29. A vehicle air supply system, comprising: a) reservoir for
storing compressed air; b) an air compressor in fluid communication
with the reservoir for providing compressed air to the reservoir;
c) a temperature sensor positioned to sense a temperature of the
compressed air; d) a controller linked to the air compressor, the
controller compares a sensed temperature of the air compressed by
the air compressor with a predetermined threshold temperature and
deactivates the air compressor when the sensed temperature exceeds
the threshold temperature.
30. The system of claim 29 wherein the controller activates the air
compressor when an air pressure in the reservoir is less than a
predetermined threshold pressure and the sensed temperature exceeds
the threshold temperature.
31. The system of claim 29 further comprising a control valve
coupled to a compressor unloader, wherein the controller controls
the control valve to selectively apply an air signal to the
compressor unloader to selectively deactivate the compressor.
32. An air compressor controller, comprising: a) input means for
receiving compressor air temperature signals; b) storage means for
storing a compressor control algorithm; c) processing means for
applying the compressor control algorithm to the compressor air
temperature signals, wherein the processor provides an air
compressor deactivation signal when the compressor air temperature
signal exceeds the threshold temperature signal value; d) output
means for communicating the compressor deactivation signal to
deactivate the compressor.
33. An air compressor, comprising: a) compressing means for
compressing air; and b) sensing means for sensing a temperature of
air compressed by the compressing means.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates generally to air compressor
control in an internal combustion engine, and more particularly, to
controlling activation and deactivation of an air compressor based
on a temperature of compressed air.
BACKGROUND OF THE INVENTION
[0002] Modern trucks contain air compressors which are used to
charge an air tank from which air-powered systems, such as service
brakes, windshield wipers, air suspension, etc., can draw air. In a
typical trucking application, an air compressor can run in a loaded
or activated state a large percentage of the time. Systems have
been developed to reduce the amount of time the air compressor is
activated. For example, systems have been developed that activate
the compressor when pressure in a reservoir drops below a first
predetermined value, and deactivates the compressor when pressure
in the reservoir reaches a second, higher predetermined value.
[0003] U.S. Pat. No. 6,036,449 to Nishar et al. discloses an air
compressor control that monitors the pressure in the reservoir and
the head metal temperature of the compressor. When the reservoir is
of a pressure between the two set pressures and is in a loaded
state, the air compressor will be unloaded after a set time
interval that is based on a compressor head metal temperature to
maintain threshold temperatures of the compressor head metal within
a suitable range. Additionally, the compressor head is evaluated
such that whenever the compressor head temperature exceeds a
predetermined threshold temperature the air compressor is placed in
an unloaded state until the compressor head temperature drops below
the predetermined threshold temperature. The head metal temperature
is controlled to prevent excessive heating of the head.
SUMMARY
[0004] The present application relates to controlling air
compressors based on a temperature of air compressed by the air
compressor. In one method of controlling an air compressor, a
temperature of air compressed by the air compressor is sensed. The
sensed compressed air temperature is compared with a predetermined
threshold temperature. The air compressor is deactivated when the
sensed temperature exceeds the threshold temperature. In one
embodiment, the air compressor is deactivated when the sensed
temperature exceeds the threshold temperature and a sensed
reservoir pressure is above the threshold pressure. In one
embodiment, the threshold temperature is selected to inhibit carbon
formation caused by oil breakdown.
[0005] The temperature of the compressed air may be sensed at a
variety of locations. For example, the temperature of the
compressed air may be sensed in a compressor port, such as an
exhaust port, or an unloader valve port. The temperature of the
compressed air may be sensed in a compression chamber. In one
embodiment, the temperature of the compressed air is sensed by a
temperature sensor mounted in a compressor unloader valve that is
in fluid communication with a compression chamber.
[0006] One air compressor that is adapted for control based on a
temperature of the compressed air includes a housing, a head, a
piston, and a temperature sensor. The head is mounted to the
housing, such that the head and the housing define a compression
chamber and a fluid passage in communication with the compression
chamber. The piston is disposed in the compression chamber for
compressing air in the compression chamber. The temperature sensor
is positioned to measure a temperature of air compressed by the
piston. In one embodiment, the temperature sensor is substantially
isolated from the head and the housing.
[0007] One air compressor controller includes an input, a memory, a
processor, and an output. The input receives compressor air
temperature signals. The memory stores a compressor control
algorithm. The processor applies the compressor control algorithm
to the compressor air temperature signals. The processor provides
an air compressor deactivation signal when the compressor air
temperature signal exceeds the threshold temperature signal value.
The output communicates the compressor deactivation signal to
selectively deactivate a controlled air compressor. Alternatively,
the controller can be comprised of discrete electronic components
with no processor or memory. For example, the controller could
comprise one temperature component integrated circuit could convert
input signals to voltages and one voltage comparator component
could control the output based on voltage thresholds.
[0008] One vehicle air supply system includes a reservoir, an air
compressor, a temperature sensor, and a controller. The reservoir
stores compressed air provided by the compressor. The temperature
sensor is positioned to sense a temperature of the compressed air.
The controller is linked to the compressor. The controller compares
a sensed temperature of the air compressed by the air compressor
with a predetermined threshold temperature and deactivates the air
compressor when the sensed temperature exceeds the threshold
temperature. In one embodiment, the controller activates the
compressor when an air pressure in the reservoir is less than a
predetermined threshold pressure and the sensed temperature exceeds
the threshold temperature.
[0009] Further advantages and benefits will become apparent to
those skilled in the art after considering the following
description and appended claims in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic illustration of a vehicle air supply
system;
[0011] FIG. 2 is a flow chart that illustrates a method of
controlling an air compressor based on a temperature of compressed
air;
[0012] FIG. 3 is a schematic illustration of a vehicle air supply
system;
[0013] FIG. 4 is a flow chart that illustrates a method of
controlling an air compressor based on a temperature of compressed
air and a reservoir pressure;
[0014] FIG. 5 is a schematic illustration of a compressor
controller;
[0015] FIG. 5A is a schematic illustration of a compressor
controller;
[0016] FIG. 6 is a schematic illustration of a compressor; and
[0017] FIG. 7 is an illustration of an unloader valve.
DETAILED DESCRIPTION
[0018] The present invention is directed to controlling activation
and deactivation of an air compressor 10 based on a temperature of
compressed air. The present invention can be implemented in a wide
variety of different vehicle air supply systems. FIG. 1 illustrates
an example of one such vehicle air supply system 12.
[0019] The illustrated air supply system 12 includes an air
compressor 10, a reservoir 16, a governor 18, and an air dryer 20.
The air compressor 10 includes a housing 11, a head 13, and a
piston 15. The head 13 is mounted to the housing 11 such that the
head and the housing define a compression chamber 17. The piston 15
reciprocates in the compression chamber 17 to compress air in the
compression chamber in a known manner. The compressor 10 may be
driven by a vehicle crank shaft (not shown). The compressor 10
receives air from an air source 22, such as an engine air intake.
The compressor 10 compresses the air and provides the compressed
air to the reservoir 16. In the air system illustrated by FIG. 1,
the governor 18 places the compressor 10 in an activated or loaded
state when the pressure in the reservoir 16 falls below a
predetermined minimum pressure and places the compressor in a
deactivated or unloaded state when the pressure in the reservoir
reaches a predetermined maximum pressure. In the example
illustrated by FIG. 1, the governor 18 places the compressor 10 in
an unloaded state by providing an air signal to a compressor
unloader 24. The compressor unloader may take a variety of
different forms. For example, the unloader 24 may be a mechanism
that holds an inlet valve 25 open, or may be a separate valve
assembly 54 (shown in FIGS. 6 and 7).
[0020] FIG. 2 illustrates a method of controlling the air
compressor 10 based on a temperature of air compressed by the air
compressor. A temperature T.sub.A of air compressed by the air
compressor is sensed 30. The sensed compressed air temperature
T.sub.A is compared 32 with a predetermined threshold temperature
T.sub.H. If the sensed air temperature T.sub.A is greater than the
predetermined threshold temperature T.sub.H, the compressor is
deactivated 34 or unloaded. If the sensed air temperature T.sub.A
is less than the predetermined threshold temperature T.sub.H, the
compressor is allowed to be activated 36 or loaded.
[0021] In the exemplary embodiment, the compressor 10 is lubricated
by oil. For example, the compressor 10 may be lubricated by oil of
the engine that drives the compressor. When the engine oil gets too
hot, the oil may break down and carbon will form. Carbon formation
may damage the compressor and/or clog lines 37 in the air supply
system, such as a line between the compressor 10 and the reservoir
16. In one embodiment, the predetermined threshold temperature
T.sub.H is set to prevent the formation of carbon. In one example,
the predetermined threshold temperature or the compressed air may
be set in the range of 325 to 400 degrees Fahrenheit measured in
the compressor outlet passage. For example, the predetermined
threshold temperature T.sub.H could be set at 375 degrees
Fahrenheit measured in the compressor outlet passage 46.
[0022] In one embodiment, the compressor is maintained in the
deactivated state until the sensed air temperature falls below a
predetermined lower boundary temperature T.sub.L. The difference
between the threshold temperature T.sub.H and the lower boundary
temperature T.sub.L prevents the compressor from being rapidly
cycled between the activated and deactivated states. In one
embodiment, the compressor is allowed to be activated as soon as
the sensed compressed air temperature T.sub.A falls below the upper
control temperature T.sub.H.
[0023] FIG. 3 illustrates a compressor control circuit 40 that
controls a compressor 10 in an air supply system 12 based on a
temperature of compressed air. The illustrated control circuit 40
includes a controller 42, a temperature sensor 44, and a control
valve 47. The temperature sensor 44 is positioned to sense a
temperature of the compressed air. The temperature sensor 44 can be
positioned at a variety of positions to sense the temperature of
compressed air provided by the compressor. In the embodiment
illustrated by FIG. 3, the temperature sensor 44 is positioned in
the compressor outlet passage 46 to measure the temperature of the
compressed air in the outlet port port. Additional examples of
locations for the temperature sensor include in the compression
chamber 17, in an exhaust port 50, in a line 37 that couples the
compressor 10 to the reservoir 16, and in an unloader valve 54
(FIG. 6).
[0024] In the exemplary embodiment, the temperature sensor 44 is
positioned, such that the temperature sensor is substantially
isolated from structures with significant mass, such as the head 13
and the housing 11. Substantially isolating the temperature sensor
44 from the head 13 and the housing 11 provides a more accurate
measure of the temperature of the compressed air. If the
temperature sensor is thermally coupled to the head 13 or the
housing 11, the temperature sensor 44 will sense the temperature of
the head or the housing, rather than the temperature of the
compressed air. The temperature of the compressed air cannot
accurately be correlated from the temperature of the head 13 or the
housing 11. The head 13 and the housing 11 have a large thermal
mass that heats up or cools down over a substantial period of time.
As a result, there is a significant lag in changes in the head or
housing temperature due to the changes in the compressed air
temperature. In addition, the head and the housing are typically
cooled by the engine cooling system. The engine cooling system
typically operates to control the temperature of the engine,
regardless of the temperature of the compressed air. As a result,
head or housing temperature controlled by the engine cooling system
is independent of the temperature of the compressed air. As such,
an accurate estimate of the compressed air temperature cannot be
obtained by measuring the temperature of the head 13 or the housing
11. The temperature sensor 44 senses a temperature of the
compressed air and provides a signal that is indicative of the
sensed temperature to the controller 42.
[0025] Referring to FIG. 3, the illustrated control valve 47
includes an inlet 54 that is coupled to the reservoir 16 and an
outlet that is coupled to the unloader 24. The controller 42
controls the control valve 47 to selectively communicate an air
signal from the reservoir 16 to the unloader selectively deactivate
the compressor 10. For example, the controller may open the control
valve to provide the air signal to the unloader when the sensed
temperature exceeds the predetermined threshold temperature T.sub.H
to place the compressor in an unloaded state. The controller may
close the control valve when the sensed temperature is below the
predetermined threshold temperature to allow the compressor to be
placed in an loaded state. In one embodiment, the control valve is
a solenoid controlled valve.
[0026] In the illustrated embodiment, the path from the reservoir
16, through the control valve 47, to the unloader 24 is parallel to
the path from the reservoir 16, through the governor 18, to the
unloader. As a result, the control valve 46 may operate to bypass
the governor 18 and deactivate the compressor 10 when the sensed
compressed air temperature exceeds the predetermined threshold
temperature under the control of the controller 42.
[0027] In one embodiment, the air compressor 10 is activated when
an air pressure P.sub.R in the reservoir 16 is less than a
predetermined minimum pressure P.sub.L and the sensed temperature
T.sub.A exceeds the threshold temperature T.sub.H. In the example
illustrated by FIG. 3, a pressure sensor 60 senses the pressure in
the reservoir 16. The pressure sensor 60 provides a signal to the
controller 42. In this embodiment, the controller 42 deactivates
the compressor 10 when the compressed air temperature is above the
predetermined threshold temperature and the reservoir pressure is
above the predetermined minimum pressure. In this embodiment, the
controller 42 does not deactivate the compressor 10 when the
compressed air temperature T.sub.A is above the predetermined
threshold temperature T.sub.H and the reservoir pressure P.sub.R is
below the predetermined minimum pressure. This keeps the pressure
in the reservoir from falling below the predetermined minimum
pressure P.sub.L. The predetermined minimum pressure set by the
controller 42 may be different than the predetermined minimum
pressure set by the governor 18.
[0028] FIG. 4 illustrates a method of controlling an air compressor
based on a compressed air temperature and a reservoir pressure. In
the method illustrated by FIG. 4, upper and lower compressor
control temperatures T.sub.H, T.sub.L and upper and lower reservoir
pressures P.sub.H, P.sub.L are set 70. For example, the compressor
control temperatures and pressures may be read from memory. In the
exemplary embodiment, the upper compressor control temperature
T.sub.H is selected to prevent the formation of carbon and the
lower control temperature T.sub.L corresponds to an acceptable
compressed air temperature. For example, the upper and lower
control temperatures T.sub.H, T.sub.L may be 375 degrees Fahrenheit
and 325 degrees Fahrenheit respectively, measured at an outlet 46
of the air compressor 10. The upper compressor control pressure
P.sub.H may correspond to a safe upper operating pressure of the
reservoir and the lower control pressure temperature P.sub.L may be
selected to ensure that there is enough air in the reservoir to
operate the air powered systems. In one embodiment, the state
(activated or deactivated) is initially determined or set. The
compressor 10 may initially be set 72 to the activated state. After
the initial temperature and pressure control values are set, a
compressor control loop 74 repeats each time a predetermined time
delay elapses. In the compressor control loop, the temperature of
air compressed by the air compressor is sensed 76. The pressure of
compressed air in the reservoir is sensed 78. The sensed
temperature is compared 80 to the upper control temperature T.sub.H
and the sensed pressure is compared 82, 83 to the lower control
pressure P.sub.L. The air compressor is activated 84, 85 when the
sensed pressure is less than the lower control pressure P.sub.L
regardless of the sensed temperature. The air compressor is
deactivated 86 when the sensed temperature exceeds the upper
control temperature T.sub.H and the sensed pressure is above the
lower control pressure P.sub.L. If the temperature T.sub.A is less
than the upper control temperature T.sub.H and the pressure P.sub.R
is greater than the lower control pressure P.sub.L, the pressure
P.sub.R is compared 87 to the upper control pressure P.sub.H. If
the pressure P.sub.R is greater than the upper control pressure
P.sub.H, the compressor 10 is deactivated 88. If the pressure
P.sub.R is less than the upper control pressure P.sub.H, the
compressor is maintained in its current state (activated or
deactivated). The control loop is repeated to control the
activation and deactivation of the compressor. In one embodiment,
the method illustrated by FIG. 4 is performed by a governor and an
electronic controller. In another embodiment, the method
illustrated by FIG. 4 is performed by a controller that processes
both pressure and temperature signals. In this embodiment, the
governor may be eliminated.
[0029] In one embodiment of the method illustrated by FIG. 4, once
the compressor is deactivated, activation is delayed to prevent
rapid cycling between the activated and deactivated states. For
example, if the compressor is deactivated due to a sensed elevated
compressed air temperature, activation of the compressor may be
delayed until the sensed pressure reaches the lower control
pressure P.sub.L, even though the sensed compressed air temperature
may have fallen below the lower control temperature T.sub.L.
[0030] FIG. 5 is a schematic illustration of a controller 42 that
can be used to control the compressor based on a temperature of air
compressed by the compressor. For example, the controller could be
used to perform the methods illustrated by FIGS. 2 and 4. The
controller 42 illustrated in the example of FIG. 5 includes an
input 90, memory 92, a processor 94, and an output 96. The input 90
receives compressor air temperature signals 98 and/or reservoir
pressure signals 100. The memory 92 stores a compressor control
algorithm and predetermined values, such as upper and lower control
temperature values and/or upper and lower. Examples of compressor
control algorithms are illustrated by FIGS. 2 and 4. The processor
94 applies the compressor control algorithm to the compressor air
temperature signals and/or the reservoir pressure signals to
produce output signals 102. In the embodiment illustrated by FIG.
6, the output signals 102 are provided from the controller output
96 to the control valve 46 (FIG. 3). Examples of output signals 102
include an air compressor activation signal that causes the
compressor to be activated and an air compressor deactivation
signal that causes the compressor to be deactivated.
[0031] FIG. 5A illustrates another example of a controller 42'. The
controller 42' includes an input 103 from a thermocouple or other
temperature measuring device, a temperature to voltage converter
component 105, an input 104 from a pressure transducer or other
pressure measuring device and a pressure to voltage converter
component 106. The input 103 receives compressor air temperature
signals 98. The input 104 receives reservoir pressure signals 100.
The temperature to voltage converter component 105 converts
compressor air temperature signals to voltage signals 109. The
pressure to voltage converter component 106 converts reservoir
pressure signals to voltage signals 110. The voltage comparator 107
provides a deactivation signal 111 when voltage signals provided to
the voltage comparator by the voltage converters are outside
threshold limits.
[0032] Referring to FIGS. 6 and 7, in one embodiment the
temperature of air compressed by the air compressor 10 is sensed by
a temperature sensor 44 mounted in an unloader valve assembly 54
that is in fluid communication with the compression chamber 17. The
illustrated unloader valve assembly 54 includes a stationary member
112, a moveable member 114, and a biasing member 116, such as a
spring. The biasing member 116 biases the moveable member 114 away
from the stationary member and into engagement with a valve seat
118. When the moveable member 114 is in engagement with the valve
seat 118, an unloader passage 120 through head 13 is closed and the
compressor 10 is in an activated state. An air control signal is
selectively communicated to a control port 120 of the unloader
valve assembly 54 by the governor and/or the control valve 46. When
the air control signal is applied to the unloader valve assembly,
the moveable member 114 is forced out of engagement with the valve
seat by the air control signal against the force applied by biasing
member. When the moveable member 114 is not in engagement with the
valve seat 118, the unloader passage 120 is open and the compressor
10 is in a deactivated state.
[0033] In the example of FIG. 7, the moveable member 114 includes
an opening 122 to a cavity 124. The stationary member 112 extends
into the cavity 124. Air is compressed and forced into the cavity
124 and around the fixed member 112. In the example of FIG. 7, the
temperature sensor 44 is mounted to the stationary member in the
cavity 124. For example, a bore 126 may be provided through the
stationary member and the temperature sensor 44 is passed through
the bore 126 and positioned at an end 128 of the stationary member.
Positioning the temperature sensor 44 in the unloader valve
assembly positions the temperature sensor in close proximity to the
compression chamber 17 and substantially isolates the temperature
sensor from large heat sinking components, such as the housing and
the head. This close proximity to the compression chamber and
substantial isolation from the head and housing provides an
accurate measure of the temperature of the air in the compression
chamber. In addition, changes in temperature in the compression
chamber are quickly sensed by the temperature sensor 44, due to the
close proximity to the compression chamber and isolation from the
housing 11 and head 13.
[0034] The temperature sensor 44 can be positioned at a variety of
other positions to sense the temperature of compressed air provided
by the compressor. The temperature sensor 44 may be positioned in
the outlet port 46, in the exhaust port, in the compression chamber
17, or in lines 37 that couple the compressor 10 to the reservoir
16, and in an unloader valve 54. In the exemplary embodiment, the
temperature sensor is substantially isolated from large heat
sinking components, such as the head and the housing. Isolating the
temperature sensor 44 from large heat sinking components
significantly shortens the time required for changes in the
temperature of the of the compressed air to be sensed by the
temperature sensor.
[0035] While the invention has been described with reference to
specific embodiments, it will be apparent to those skilled in the
art that may alternatives, modifications, and variations may be
made. Accordingly, the present invention is intended to embrace all
such alternatives, modifications, and variations that may fall
within the spirit and scope of the appended claims.
* * * * *