U.S. patent application number 10/162306 was filed with the patent office on 2003-12-04 for blower assembly with closed-loop feedback.
This patent application is currently assigned to Ametek, Inc.. Invention is credited to Abbassi, Sahil J., Anstine, William E., Gordon, Frederick A., Hower, Rodney N..
Application Number | 20030223877 10/162306 |
Document ID | / |
Family ID | 29583583 |
Filed Date | 2003-12-04 |
United States Patent
Application |
20030223877 |
Kind Code |
A1 |
Anstine, William E. ; et
al. |
December 4, 2003 |
Blower assembly with closed-loop feedback
Abstract
A closed-loop blower includes a blower assembly having a
motorized fan that draws ambient air in through an inlet and
exhausts air out an outlet. A control circuit is coupled to the
motorized fan and a pressure sensing device near the outlet
measures pressure of the exhaust air and generates a pressure
signal. The control circuit receives the pressure signal and
adjusts the speed of the motorized fan to obtain a desired pressure
at the outlet. Temperature and motor speed readings may also be
detected and input to the control circuit to adjust the speed of
the motor and thus the fan. An input device may be provided to
adjust the desired pressure values or the control circuit may be
programmed with the desired value.
Inventors: |
Anstine, William E.; (North
Canton, OH) ; Hower, Rodney N.; (Akron, OH) ;
Gordon, Frederick A.; (North Canton, OH) ; Abbassi,
Sahil J.; (Ravenna, OH) |
Correspondence
Address: |
Ray L. Weber
Renner, Kenner, Greive, Bobak, Taylor & Weber
Fourth Floor
First National Tower
Akron
OH
44308-1456
US
|
Assignee: |
Ametek, Inc.
|
Family ID: |
29583583 |
Appl. No.: |
10/162306 |
Filed: |
June 4, 2002 |
Current U.S.
Class: |
417/18 |
Current CPC
Class: |
A61M 2205/3368 20130101;
A61M 2205/3317 20130101; Y02B 30/70 20130101; A61M 16/0069
20140204; F04D 27/004 20130101; A61M 2016/0027 20130101; A61M
2205/3372 20130101; A61M 16/0066 20130101; A61M 16/024
20170801 |
Class at
Publication: |
417/18 |
International
Class: |
F04B 049/00 |
Claims
What is claimed is:
1. A closed-loop blower, comprising: a blower assembly having a
motorized fan that draws ambient air in through an inlet and
exhausts air out an outlet; a control circuit coupled to said
motorized fan; a pressure sensing device near said outlet to
measure pressure of the exhaust air, said pressure sensing device
generating a pressure signal; and said control circuit receiving
said pressure signal and adjusting the speed of said motorized fan
to obtain a desired pressure at said outlet.
2. The blower according to claim 1, further comprising: a
temperature sensing device associated with said blower assembly and
generating a temperature signal; and said control circuit receiving
said temperature signal to adjust said pressure signal and adjust
the speed of said motorized fan to obtain the desired pressure at
said outlet.
3. The blower according to claim 2, further comprising: at least
one Hall effect switch coupled to said motorized fan to generate a
speed signal; and said control circuit receiving said speed signal
to adjust the speed of said motorized fan.
4. The blower according to claim 1, further comprising: a
temperature sensing device associated with said blower assembly and
generating a temperature signal; at least one Hall effect switch
coupled to said motorized fan to generate a speed signal; and said
control circuit receiving said temperature, pressure and speed
signals to adjust the speed of said motorized fan to obtain the
desired pressure output.
5. The blower according to claim 4, further comprising: a second
pressure sensing device, not directly associated with the blower to
measure an end-use pressure signal; said control circuit receiving
said pressure signal and said end-use pressure signal to determine
a differential pressure; and said control circuit adjusting the
speed of said motorized fan to obtain a desired differential
pressure.
6. The blower according to claim 1, further comprising: an input
device for sending desired pressure value to said control
circuit.
7. A method for generating a desired pressure value from a blower
assembly that includes a motorized fan that draws in ambient air
through an inlet and exhausts air out an outlet, the method
comprising: inputting a set pressure value to a control circuit;
positioning a pressure sensing device near the outlet; generating a
pressure signal by said pressure sensing device; receiving said
pressure signal in said control circuit; and adjusting the speed of
the motorized fan by said control circuit depending upon the value
of said pressure signal to match said set pressure value.
8. The method according to claim 7, further comprising: measuring a
temperature value near the blower assembly; generating a
temperature signal representative of said temperature value;
receiving said temperature signal in said control circuit; and
adjusting said pressure signal based upon the value of said
temperature signal.
9. The method according to claim 8, further comprising: coupling at
least one Hall effect switch to the motorized fan to generate a
speed signal; receiving said speed signal in said control circuit;
and adjusting the speed of said motorized fan based upon said
pressure, temperature and speed signals.
10. The method according to claim 7, further comprising:
positioning a second pressure transducer away from said blower but
within the exhaust air flow; measuring a second pressure value at
said second pressure transducer to generating an end-use pressure
signal; receiving said end-use pressure signal and said pressure
signal in said control circuit to determine a differential pressure
value; and adjusting the speed of the motorized fan by said control
circuit to match said differential pressure value with said set
pressure value.
Description
TECHNICAL FIELD
[0001] The present invention relates to the art of blower
assemblies and more particularly a blower assembly that generates a
constant pressure value. Specifically, the present invention
relates to a blower assembly which monitors at least one pressure
transducer for generating a pressure signal that is used by a
controlling circuit coupled to the motor to adjust the motor speed
to obtain the desired constant pressure value.
BACKGROUND OF THE INVENTION
[0002] It is known to use blowers in many different applications
from vacuum cleaners to furnaces and other industrial applications.
Blowers may also be used in critical applications such as medical
equipment where the generation of a constant pressure is very
important.
[0003] Blower assemblies are housings which carry a motorized fan.
The housing has an inlet which allows for the drawing in of ambient
air which is redirected by the fan through an exhaust outlet. One
use for a blower in a medical application is for patients who have
sleep apnea. In such a condition, the sleeping patient unknowingly
ceases to breathe and in severe cases can suffocate one's self. In
order to prevent this, a blower is used in an assisted-breathing
apparatus to help regulate the breathing of the patient so as to
preclude cessation of respiration.
[0004] Prior blower assemblies used in medical applications used a
velocity feed-back loop to assist in the patient's breathing. Such
a system monitored the velocity of the air expelled by the fan
assembly and the velocity data was then used to regulate the motor
speed. However, such a system characteristic--exhaust velocity--has
been found to be inaccurate and unable to meet the system
requirements for critical medical applications. In particular, the
exhaust velocity values are not nearly as accurate as monitoring
the pressure which is believed to be the critical variable in such
applications.
[0005] Based upon the foregoing, there is a need in the art for a
closed loop pressure blower that utilizes a pressure reading to
generate the necessary information for controlling the speed of the
motor.
DISCLOSURE OF THE INVENTION
[0006] In light of the foregoing, it is a first aspect of the
present invention to provide blower assembly with closed-loop
feedback. The aspects of the invention which shall become apparent
as the detailed description proceeds are achieved by a blower
assembly having a motorized fan that draws ambient air in through
an inlet and exhausts air out an outlet; a control circuit coupled
to the motorized fan; a pressure sensing device near the outlet to
measure pressure of the exhaust air and generating a pressure
signal; and the control circuit receiving the pressure signal and
adjusting the speed of the motorized fan to obtain a desired
pressure at the outlet.
[0007] Another aspect of the invention which will become apparent
herein is obtained by A method for generating a desired pressure
value from a blower assembly that includes a motorized fan that
draws in ambient air through an inlet and exhausts air out an
outlet, the method comprising: inputting a set pressure value to a
control circuit; positioning a pressure sensing device near the
outlet generating a pressure signal by the pressure sensing device;
receiving said pressure signal in said control circuit; and
adjusting the speed of the motorized fan by said control circuit
depending upon the value of said pressure signal to match said set
pressure value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] For a complete understanding of the objects, techniques, and
structure of the invention, reference should be made to the
following detailed description and the accompanying drawings
wherein:
[0009] FIG. 1 is an elevational view, in partial cross-section, of
a blower assembly according to the present invention;
[0010] FIG. 2 is a plan view of the blower assembly interfaced with
a flow tube;
[0011] FIG. 3 is a schematic diagram of the blower assembly
according to the present invention;
[0012] FIG. 4 is a flow chart setting forth the control steps of
the blower assembly according to the present invention; and
[0013] FIG. 5 is a flow chart for setting flow variation of the
operational steps for the blower assembly according to the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014] Referring now to the drawings and more particularly to FIGS.
1 and 2. It can be seen that a closed-loop blower assembly
utilizing pressure feedback is designated generally by the numeral
10. The blower assembly 10 includes a housing 12 which may be of a
split construction that is assembled around the components of the
blower assembly. The split housing may be secured by snap-type
fasteners, by threaded fasteners or the like. The blower assembly
10 includes a motor 14 which as shown in the present drawing is a
brushless DC motor. However, it should be appreciated that other
types of motors could be used in the present invention. Such motors
include, but are not limited to, AC induction, switched reluctance
or universal brush type motors. It will be appreciated that
although a blower configuration is shown, it is well within the
scope of the present invention that the aspects taught herein are
equally applicable to a pump configuration. In any event, the motor
14 drives or rotates a shaft 16 which in turn rotates a fan 20. The
fan has an inlet 22 and a plurality of vanes 24. The housing 12
provides an opening 26 aligned with the inlet 22 for drawing in
ambient air which is then exhausted by the fan 20 through an
exhaust port 28. Although only a single port 28 is shown, it will
be appreciated that multiple ports could be provided.
[0015] A control circuit board assembly 30 is secured within the
housing 12 and in the present instance functions as a mounting
board for the motor 14. The control circuit board 30 provides a
power connector 32 which allows the blower assembly to receive and
distribute power as required and also to receive and output data
needed for operation of the blower assembly 10.
[0016] Referring now to FIG. 3, it can be seen that a schematic
diagram of the blower assembly 10 is presented. As noted
previously, the motor 14 and the fan 16 are associated with a
control circuit board 30. The control circuit 30 includes a
controller 40. The controller 40 provides the necessary hardware,
software and memory for controlling the operation of the motor 14
and thus the blower assembly 10. The controller 40 may be a
programmable micro-controller, a digital signal processor, or a
custom integrated circuit specifically designed to regulate motor
speed. In particular, the custom integrated circuit may be an
application specific integrated circuit or a field programmable
gate array. Any of the foregoing devices may be programmed to react
in a manner as required by each end-use application. Accordingly,
although the present invention is directed to maintaining a
specified pressure of air that is exhausted from the blower
assembly, it will be appreciated that the range of pressures or a
rate of pressure increase or decrease could be generated by the
present invention. As such, these custom programs may allow for
endless iterations for direct customization by application.
[0017] In order to obtain the particular control features of the
present invention, a pressure transducer 42 is positioned in the
housing 12 in close proximity to the exhaust port 28. The pressure
transducer may be a differential, absolute, or gauge pressure
transducer that generates an electrical output signal that is
received by the controller 40. Also providing input to the
controller 40, may be a thermistor 44 which is coupled to the motor
14 or related component. The thermistor 44 may detect ambient air
temperature or the temperature of temperature-critical components
that may adversely affect the pressure reading taken by the
pressure transducer 42. The temperature reading is input to the
controller 40 to make any necessary adjustments. At least one Hall
effect switch 46 may be coupled to the motor to detect the speed
thereof. This speed information is input to the controller 40 to
provide the necessary information for the speed of the motor at any
given moment. In the preferred embodiment, a set of three Hall
effect switches 46 are used to accurately determine rotor position
for proper commutation.
[0018] A second pressure transducer 48 may be placed in a flow tube
49 that is coupled to the exhaust port 28. The flow tube 49 is
associated with the end-use device coupled to the blower assembly.
Or the transducer 48 may be placed in any other desired location so
as to obtain a pressure differential reading. In other words, the
information generated by the second pressure transducer is compared
to the information generated by the first pressure transducer 42 by
the controller to adjust the speed of the motor 14 accordingly.
Data collected by the transducer 48 is transferred by a signal wire
or conduit 51 to the controller 40.
[0019] It will also be appreciated by one skilled in the art that
an input device 50 may allow for an end-user to establish a
particular operating pressure set point for the piece of equipment
to be associated with the blower assembly. This input can include a
single set point or a range of operating points to allow for
efficient operation of the motor of the equipment. The input device
50 may transfer data to the controller 40 via the power connector
32 or other similar connection device.
[0020] Referring now to FIG. 4 of the drawings an operational flow
chart employed by the controller 40 is designated generally by the
numeral 100. At a first step 102, pressure from the external
pressure transducer 42 is measured and this information is
converted to an electrical signal at step 104.
[0021] At step 106, a desired pressure input may be provided by the
control input device 50 or by a factory-set value programmed into
the controller 40. Additional information which is supplied to the
controller 40 is indicated at step 108 wherein a temperature may be
detected by the thermistor 44 at the power supply, ambient or other
internal control temperature. At step 110, the measured temperature
is converted to an electrical signal and sent to the controller 40.
Accordingly, at step 112, based upon the inputs received, the
controller 40 determines whether the measured pressure equals the
desired pressure, and if required, whether that pressure should be
adjusted based upon the temperature detected by the thermistor 44.
In the event that the pressure is to be adjusted based upon the
temperature, it will be appreciated that look-up tables contained
within the controller's memory may be utilized to provide an
adjustment factor to the pressure value desired. In any event, at
step 114, if the actual pressure is less than the desired pressure,
then at step 116 the controller 40 increases the motor speed by
increasing the pulse width modulation duty cycle of the power
applied to the motor. In a similar fashion, at steps 118 and 120 if
the pressure is at the desired level then the duty cycle is not
changed at step 120. Or, at step 122, if it is determined that the
actual pressure is more than the desired pressure then at step 124
the motor speed is decreased by decreasing the duty cycle. At step
126, the internal motor control adjusts the speed of the motor.
Accordingly, at step 128, the motor controls the speed of the
blower assembly or fluid pump, which corresponds to the pressure
output. The process then returns to step 102 to repeat the
foregoing steps.
[0022] Referring now to FIG. 5 a methodology is indicated by the
numeral 200 for utilizing the controller 40 and the associated
components for the purpose of obtaining a differential pressure
value for use with the blower assembly 10. In particular, at step
202, a pressure generated by an external source is measured by the
pressure transducer 42. At step 204, a second reference pressure is
measured by the pressure transducer 48. And then at step 206, these
signals are converted into an appropriate electrical signal and
sent to the controller 40.
[0023] Additional information which is input to the controller 40
is indicated at step 208, wherein a control signal may be input by
the device 50 to establish a desired pressure value for the
attached equipment. At step 210, a temperature value may be
measured by the thermistor 44 at the appropriate location
associated with the assembly 10. At step 212, the measured
temperature value is converted to an electrical signal and the
input and temperature information is submitted to the controller
for evaluation at step 214.
[0024] The controller 40 at step 214, measures the differential
pressure, that is the difference between the values read by the
pressure transducers 42 and 48, and compares the difference value,
which may be adjusted by the temperature value detected by the
thermistor 44, to the desired differential pressure value.
Accordingly, at step 216, if the actual differential pressure is
less than the desired differential pressure, then the controller at
step 218 increases the motor speed by increasing the duty cycle.
If, the pressure is the same as desired--or within a specified
range--at step 220, then the controller 40 instructs the motor to
maintain the normal operating duty cycle at step 222. If, however,
the actual differential pressure is more than desired, at step 224,
then the controller 40 decreases the motor speed at step 226 by
decreasing the duty cycle.
[0025] At step 228, the controller 40 adjusts the speed of the
motor and in turn the motor controls the speed of the fan or fluid
pump at step 230. Upon completion of step 230, the controller
returns the process step to 202 and the foregoing steps are
repeated.
[0026] Based upon the foregoing those skilled in the art will
appreciate the advantages of the present invention. By utilizing a
blower with integrated pressure sensing and feedback, precise
control of the blower output performance can be obtained. The
control pressure system includes a pressure sensing device or
devices which provide electrical output signals to the controller.
The controller may be programmed to react to changes in the input
signal from the pressure feedback device with appropriate
compensation for temperature and other variables. This may be
accomplished by the programming code of the controller 40 or by
alternating the pulse with modulation duty cycle submitted to the
motor until a predetermined pressure, or pressure range is
achieved.
[0027] In an application which requires a constant pressure source,
a restriction or blockage downstream from the blower will cause a
positive pressure differential as compared to the speed input
command setpoint. In this condition, the controller 40 program
forces the blower to slow down or brake, thereby reducing the
pressure output to the original setpoint. In this type of
application when there is a decrease in restriction, downstream
from the blower, a negative pressure differential as compared to
the speed input command setpoint would be detected. In this
condition, the controller program would cause the blower to
accelerate, thereby increasing the pressure output to the original
setpoint. From the foregoing, it can be seen that the present
invention is advantageous in that the controller coupled with the
pressure feedback devices and other monitoring components such as
motor speed and temperature can be programmed to react in a manner
as required by each individual application. Accordingly, a custom
program embedded in the controller allows for endless iterations
for direct customization by the end-use application.
[0028] Thus, it can be seen that the objects of the invention have
been satisfied by the structure and its method for use presented
above. While in accordance with the Patent Statutes, only the best
mode and preferred embodiment has been presented and described in
detail, it is to be understood that the invention is not limited
thereto or thereby. Accordingly, for an appreciation of the true
scope and breadth of the invention, reference should be made to the
following claims.
* * * * *