U.S. patent application number 10/822699 was filed with the patent office on 2005-01-13 for linear compressor and control method thereof.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Kim, Nam-su.
Application Number | 20050008511 10/822699 |
Document ID | / |
Family ID | 33448363 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050008511 |
Kind Code |
A1 |
Kim, Nam-su |
January 13, 2005 |
Linear compressor and control method thereof
Abstract
A linear compressor having a core combined to one end of a
piston to detect a position of the piston reciprocally moving up
and down, and a bobbin having a first sensor coil and a second
sensor coil that detect the position of the core. A controller
determines the state of a load on the piston by measuring the time
the core takes to exit and enter the bobbin from an inhale stroke
through a compression stroke of the piston and control a position
of the piston based on the measured state of the load. A method for
controlling the operation of the linear compressor including timing
the core driven by a piston through a stroke cycle, receiving the
time and computing a load on the piston, outputting a piston
position signal based on the load computed, and controlling a
piston stroke according to the piston position signal, by varying
the power driving the linear compressor.
Inventors: |
Kim, Nam-su; (Seoul,
KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-Si
KR
|
Family ID: |
33448363 |
Appl. No.: |
10/822699 |
Filed: |
April 13, 2004 |
Current U.S.
Class: |
417/416 ;
417/44.11 |
Current CPC
Class: |
F04B 2201/0201 20130101;
F04B 2203/0402 20130101; F04B 35/045 20130101; F04B 2201/0206
20130101; F04B 49/065 20130101 |
Class at
Publication: |
417/416 ;
417/044.11 |
International
Class: |
F04B 049/06; F04B
017/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2003 |
KR |
2003-46207 |
Claims
What is claimed is:
1. A linear compressor having a core combined to one end of a
piston to detect a position of the piston reciprocally moving up
and down, and a bobbin having a first sensor coil and a second
sensor coil detecting the position of the core, comprising: a
controller determining a state of a load of the piston by measuring
time that the core takes to exit and enter the bobbin from an
inhale stroke through a compression stroke of the piston and
controlling a position of the piston on a basis of the determined
state of the load.
2. The linear compressor according to claim 1, wherein the core has
a length shorter than one half of the length of the first sensor
coil and the second sensor coil in series.
3. The linear compressor according to claim 1, wherein the
controller increases a top clearance of the piston if the time that
the core takes to exit and enter the bobbin increases over a
predetermined critical time.
4. The linear compressor according to claim 1, further comprising:
a first branch comprising the first sensor coil and a predetermined
first dividing resistor connected in series; a second branch
comprising the second sensor coil and a predetermined second
dividing resistor connected in series; a power source applied to
the first branch and the second branch; and a voltage comparator
with input voltages applied from the first dividing resistor and
the second dividing resistor.
5. The linear compressor according to claim 4, wherein the voltage
comparator receives input voltages applied from the terminals of
each of the first sensor coil and the second sensor coil.
6. The linear compressor according to claim 4, wherein the
controller determines the state of the load on the piston based on
the time that the piston takes to be positioned near the bottom
dead center making output of the voltage comparator 0, so as to
control the position of the piston.
7. The linear compressor according to claim 5, wherein the
controller determines the state of the load on the piston on a
basis of difference of time that the piston takes to be positioned
near the bottom dead center making output of the voltage comparator
0, so as to control the position of the piston.
8. A control method of a linear compressor having a core combined
to one end of a piston to detect a position of the piston
reciprocally moving up and down, and a bobbin having a first sensor
coil and a second sensor coil detecting the position of the core,
comprising: measuring a time that the core takes to exit and enter
the bobbin from an inhale stroke through a compression stroke of
the piston; and controlling a position of the piston by determining
state of a load on the piston on a basis of the time that the core
takes to exit and enter the bobbin.
9. The control method of the linear compressor according to claim
8, further comprising forming a length of the core to be shorter
than a half of length of the first sensor coil and the second
sensor coil connected in series.
10. The control method of the linear compressor according to claim
8, further comprising increasing a top clearance of the piston if
the time that the core takes to exit and enter the bobbin increases
above a predetermined critical time.
11. A method for controlling an operation of a linear compressor,
comprising: timing a core driven by a piston through a stroke
cycle; receiving the time and computing a load on the piston;
outputting a piston position signal based on the load computed; and
controlling a piston stroke according to the piston position
signal, by varying the power driving the linear compressor.
12. The method of claim 11, wherein the controlling further
comprises controlling the piston stroke, wherein the piston stroke
is increased as the load increases and the piston stroke is
decreased as the load decreases.
13. The method of claim 11, wherein the controlling further
comprises if the load computed is greater than a predetermined
critical load amount, then increasing a top clearance of the
piston.
14. The method of claim 11, wherein timing the core is based on the
elapsed time when the core exits the sensor coil aperture during a
compression stroke, and then enters the sensor coil aperture during
an inhale stroke of the piston.
15. The method of claim 11, wherein timing the core is based on the
elapsed time when the core enters the sensor coil aperture during a
compression stroke, and then exits the sensor coil aperture during
an inhale stroke of the piston.
16. A linear compressor piston control device, comprising: a bobbin
defining an aperture; a sensor coil disposed in the bobbin; a core
attached to a piston disposed coaxially in the aperture of the
bobbin, wherein the core is less than one half the length of the
sensor coil; a controller controlling a position of the piston by
determining a load based on signals from the sensor coil sensing
the position of the core.
17. The control device according to claim 16, wherein the
controller determines the load based on the elapsed time when the
core exits the sensor coil aperture during a compression stroke and
then enters the sensor coil aperture during an inhale stroke of the
piston.
18. The control device according to claim 17, further comprising
the controller adjusting a top clearance of the piston based on the
elapsed time.
19. The control device according to claim 18, wherein the
controller increases the top clearance if the elapsed time is above
a predetermined critical time.
20. The control device according to claim 16, wherein the sensor
coil includes a first sensor coil and a second sensor coil.
21. The control device according to claim 20, wherein the first
sensor coil and the second sensor coil have the same number of
turns, size and inductance value.
22. The control device according to claim 21, wherein the control
device further comprises: a first branch having a first
predetermined dividing resistor connected in series with the first
sensor coil; a second branch having a second predetermined dividing
resistor connected in series with the second sensor coil.
23. The control device according to claim 22, further comprising: a
voltage comparator that receives voltage inputs from the first
branch and the second branch and outputs a comparator signal; a
digital signal processor that receives the comparator signal and
sends an output signal to the controller based on the comparator
signal.
24. The control device according to claim 23, wherein the
controller determines the load by measuring the time that elapses
between the comparator signal equaling 0 a first time during a
compression stroke and the comparator signal equaling 0 a second
time during an inhale stroke.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2003-46207, filed Jul. 8, 2003, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a linear compressor and a
control method thereof. A linear compressor is widely used to
compress coolant in a freezing cycle such as in equipment like a
refrigerator, freezer, etc. The linear compressor measures the
magnitude of a stroke of a piston, and controls an operation of the
piston by applying a current to a driving motor of the linear
compressor based on an analysis of the measured magnitude of the
stroke.
[0004] 2. Description of the Related Art
[0005] FIG. 1 is a cross-sectional view of a position detection
sensor for a piston of a conventional linear compressor. As
illustrated in FIG. 1, the position detection sensor comprises a
bobbin 100, a sensor coil 101, a core support 102, and a core
103.
[0006] The bobbin 100 includes the sensor coil 101 inside, and the
sensor coil 101 is connected in series to a first sensor coil 101a
and a second sensor coil 101b each having the same inductance
value, size, and number of turns. The core support 102 is made of
non-magnetic material and supports the core 103 and is combined to
the piston (not shown).
[0007] As the core 103 combined to the piston of the compressor
reciprocally moves back and forth along an inner hole of the bobbin
100, a predetermined reactance is generated in the sensor coil 101
according to reciprocal movement of the piston.
[0008] FIG. 2 is a diagram of a conventional position detection
circuit for the piston of the conventional linear compressor. As
illustrated in FIG. 2, two serial sensor coils 101 are connected in
parallel with two serial dividing resistors Ra and Rb, and a
triangle pulse is input as a power source 105. A difference of
voltages divided by the dividing resistors Ra and Rb is amplified
by an amplifier 104 to detect a maximum output voltage according to
the piston in which the core 103 moves back and forth starting from
a center point between the first sensor coil 101a and the second
sensor coil 101b. An analog signal processor 106 receives an output
pulse from the amplifier 104 and detects the position of the piston
through a predetermined signal process.
[0009] FIG. 3 illustrates an output pulse from the amplifier 104 in
FIG. 2 according to the reciprocal movement of the piston of the
linear compressor. As illustrated in FIG. 3, the output voltage
from the amplifier (line "a") has a linear output property for the
reciprocal movement of the piston. The position of the piston can
be detected with the output voltage because the output voltage is
proportional to the position of the piston.
[0010] However, the sensor circuit of the conventional linear
compressor may vary the angle of slope of the linear graph
according to external environmental conditions such as temperature
and pressure. If the sensor circuit of the conventional linear
compressor follows the linear property represented by a small angle
of the slope like a line "b" due to the external environmental
conditions, the piston controlled according to a steady operation
when in a high cooling capacity may collide with a valve of a
cylinder.
[0011] The conventional linear compressor uses a control method for
controlling the reciprocal movement of the piston by determining a
state of a load on the linear compressor based on a measured
temperature or a measured driving current for a motor. The
conventional control method of determining the state of the load on
the linear compressor may respond to a change of the load on the
piston late. Additionally it is hard to measure the temperature and
the driving current accurately in a linear compressor, even if
measuring points for the temperature and the driving current are
properly selected.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an aspect of the present invention to
provide a linear compressor outputting cooling power actively and
controlling a stroke of a piston by determining state of a load on
the piston accurately regardless of an external environment.
[0013] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
[0014] The foregoing and/or other aspects of the present invention
are achieved by providing a linear compressor having a core
combined to one end of a piston to detect a position of the piston
reciprocally moving up and down, and a bobbin having a first sensor
coil and a second sensor coil detecting the position of the core,
comprising a controller determining state of a load of the piston
by measuring an elapsed time for the core to exit and enter the
bobbin from an inhale stroke through a compression stroke of the
piston and controlling a position of the piston based on the
measured state of the load.
[0015] According to an aspect of the invention, the core has a
length shorter than one half of the length of the first sensor coil
and the second sensor coil in series.
[0016] According to an aspect of the invention, the controller
increases a top clearance of the piston if the amount of time taken
for the core to exit and enter the bobbin increases greatly over a
predetermined critical time.
[0017] According to an aspect of the invention, the linear
compressor includes a first branch including the first sensor coil
and a predetermined first dividing resistor connected in series, a
second branch including the second sensor coil and a predetermined
second dividing resistor connected in series, a power source
applied to the first branch and the second branch, and a voltage
comparator with voltage inputs applied to the first dividing
resistor and the second dividing resistor.
[0018] According to an aspect of the invention, the voltage
comparator has voltage inputs applied to the opposite terminals of
each of the first sensor coil and the second sensor coil.
[0019] According to an aspect of the invention, the controller
determines the state of the load on the piston on a basis of
difference of time taken for the piston to be positioned near the
bottom dead center making output of the voltage comparator zero (0)
so as to control the position of the piston.
[0020] According to an aspect of the invention, the controller
determines the state of the load on the piston on a basis of
difference of time taken for the piston to be positioned near the
bottom dead center making output of the voltage comparator zero
(0), so as to control the position of the piston.
[0021] According to another aspect of the present invention, the
above and other aspects may be also achieved by providing a control
method of a linear compressor having a core combined to one end of
a piston to detect a position of the piston reciprocal moving up
and down, and a bobbin having a first sensor coil and a second
sensor coil detecting the position of the core, including measuring
time taken for the core to exit and enter the bobbin from an inhale
stroke through a compression stroke of the piston; and controlling
a position of the piston by determining state of a load on the
piston on a basis of the time taken for the core to exit and enter
the bobbin.
[0022] According to an aspect of the invention, the control method
of the linear compressor further comprising forming length of the
core to be shorter than a half of length of the first sensor coil
and the second sensor coil connected in series.
[0023] According to another aspect of the present invention, the
above and other aspects may be achieved by providing the control
method of the linear compressor including increasing a top
clearance of the piston if the time taken for the core to exit and
enter the bobbin increases greatly than a predetermined critical
time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above and/or other aspects and advantages of the present
invention will become apparent and more readily appreciated from
the following description of the embodiments, taken in conjunction
with the accompany drawings of which:
[0025] FIG. 1 is a cross-sectional view of a position detection
sensor for a piston of a conventional linear compressor;
[0026] FIG. 2 is a diagram of a position detection circuit for the
piston of the conventional linear compressor;
[0027] FIG. 3 illustrates an output waveform from an amplifier in
FIG. 2 according to reciprocal movement of the piston of the linear
compressor;
[0028] FIG. 4 is a cross-sectional view of a position detection
sensor for a piston of a linear compressor according to an
embodiment of the present invention;
[0029] FIG. 5 is a block diagram of a position detection circuit
for the piston of the linear compressor according to an embodiment
of the present invention;
[0030] FIGS. 6A-6C and 7A-7C are input waveforms of a voltage
comparator according to reciprocal movement of the linear
compressor;
[0031] FIG. 8 is a control block diagram of the linear compressor
according to an embodiment of the present invention; and
[0032] FIG. 9 is an output waveform of the voltage comparator
according to a position of the piston of the linear compressor
according to the embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0033] Reference will now be made in detail to the embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to the
like elements throughout. The embodiments are described below to
explain the present invention by referring to the figures.
[0034] FIG. 4 is a cross-sectional view of a position detection
sensor for a piston of a linear compressor according to an
embodiment of the present invention. As illustrated in FIG. 4, the
position detection sensor comprises a bobbin 1, a sensor coil 2, a
core support 3, and a core 4.
[0035] The bobbin 1 includes a sensor coil 2 inside, and the sensor
coil 2 comprises a first sensor coil 2a and a second sensor coil
2b. The first sensor coil 2a and the second sensor coil 2b have the
same inductance value, size, and number of turns and are connected
in series. The core support 3 is made of non-magnetic material and
supports the core unit 4 and is combined to the piston (not
shown).
[0036] The core unit 4 comprises a core 4a having a short
predetermined length. In this embodiment, the length of the core 4a
is less than one half of the length of the sensor coil 2 comprising
the first sensor coil 2a and the second sensor coil 2b. The core
support 3 connects the core 4a with the piston so that the core 4a
can move according to the reciprocal movement of the piston.
[0037] As the core 4a combined to the piston of the compressor
reciprocally moves back and forth along an inner hole of the bobbin
1, a predetermined reactance is generated in the sensor coil 2
according to the reciprocal movement of the core 4a within the
sensor coil 2.
[0038] The core 4a moves reciprocally, centering around the first
sensor coil 2a through a complete cycle of the piston. Further the
core 4a is adjusted to reach near the second sensor coil 2b through
a middle point between the first sensor coil 2a and the second
sensor coil 2b (will be referred as a coil origin) when the piston
arrives in a top dead center. Also, the size of the bobbin and the
piston should be preferably configured so that the core 4a can come
out of the bobbin 1 during an expansion stroke. Alternatively, this
cycle may be reversed so that the core 4a exits the bobbin 1 during
an inhale stroke.
[0039] If the state of the load on the linear compressor turns into
an overloaded state, a stroke of the piston comes out of the bobbin
1 in an expansion stroke.
[0040] Such change of the state of the load can be determined by
measuring time taken for the center point of the core 4a to exit
and enter the bobbin 1.
[0041] A controller 13 as shown in FIG. 5, measures the time that
the core 4a takes to exit and enter the bobbin 1 to determine the
state of the load. In a case of overload, the controller 13 applies
a high current to a driving motor of the linear compressor.
[0042] However, in case of an extreme overload, the top clearance
of the piston may be increased by a partial amount of the load
calculated and controlled by the controller when the change of the
measured load is greater than a predetermined critical amount of
the load. A reason for increasing the top clearance is that the
overcontrolled piston may collide with a valve of the linear
compressor if the state of the overload turns into the state of a
steady load abruptly as the magnitude of the stroke of the piston
during the overload increases. Accordingly, it is beneficial to
prevent an abnormal operation of the piston by setting the top
clearance of the piston to a value that is adequate over a broad
load range.
[0043] The position of the piston may be controlled by determining
the state of the load by measuring the time that the core 4a takes
to exit and enter the bobbin 1. Hereinbelow, a method to measure
the time that the core 4a takes to exit and enter the bobbin 1 will
be described. FIG. 5 is a block diagram of a position detection
circuit for the piston of the linear compressor according to the
embodiment of the present invention.
[0044] As illustrated in FIG. 5, the position detection circuit
comprises a first sensor coil 2a, a second sensor coil 2b, a first
dividing resistor R1, a second dividing resistor R2, a power source
10, a voltage comparator 11, a digital signal processor 12, and a
controller 13.
[0045] The power source 10 applies power to a first branch having
the first sensor coil 2a and the first dividing resistor R1
connected in series, and to a second branch having the second
sensor coil 2b and the second dividing resistor R2 connected in
series.
[0046] The voltage comparator 11 receives voltages taken from a
terminal of each of the first dividing resistor R1 and the second
dividing resistor R2 as a comparison signal V+ and a comparison
signal V-, respectively. Also, the voltage comparator 11 may
receive voltage taken from the opposite terminals of each of the
first sensor coil 2a and the second sensor coil 2b.
[0047] The digital signal processor 12 transmits a rectangular
pulse to the controller 13 according to an output of the voltage
comparator 11, and then the controller 13 controls a driving motor
(not shown) of the linear compressor on the basis of the
rectangular pulse.
[0048] FIGS. 6A through 6C and 7A through 7C are input waveforms of
a voltage comparator according to reciprocal movement of the piston
of the linear compressor.
[0049] FIG. 6A represents a triangle pulse from the power source
10, and FIG. 6B represents waveforms input to a positive terminal
and a negative terminal of the voltage comparator 11.
[0050] FIG. 6B represents the input waveform of the voltage
comparator 11 when a center point of the upper core 4a (will be
referred to as a core origin) passes a middle point between the
first sensor coil 2a and the second sensor coil 2b (will be
referred to as a coil origin), or when the piston reaches near a
top dead center by a compression stroke. If the triangle pulse is
applied from the power source 10, an inductance L2 of the second
sensor coil 2b becomes greater than an inductance L1 of the first
sensor coil 2a. Accordingly, the input waveform V- input into the
negative terminal of the voltage comparator 11 has a time delay
longer than the time delay of the input waveform V+ input into the
positive terminal of the voltage comparator 11.
[0051] As illustrated in FIG. 6C, the digital signal processor 12
generates a rectangular waveform Vd having high level when the
input waveform V+ of the positive terminal of the voltage
comparator 11 is greater than the input waveform V- of the negative
terminal.
[0052] FIGS. 7A through 7C are waveforms when the core origin is
inclined toward the first sensor coil 2a from the coil origin. In
this case, the inductance L1 of the first sensor coil 2a becomes
greater than the inductance L2 of the second sensor coil 2b.
Accordingly, the input waveform V+ input into the positive terminal
of the voltage comparator 11 has a longer time delay. FIG. 7B
illustrates input waveforms of the voltage comparator 11 in such
case, and FIG. 7C illustrates a rectangular waveform Vd outputted
from the digital signal processor 12 corresponding to the waveforms
in FIG. 7B.
[0053] FIG. 9 is a waveform output from the voltage comparator 11
according to a position of the piston of the linear compressor
according to this embodiment of the present invention.
[0054] As illustrated in FIG. 9, a waveform "c" has two zero points
corresponding to the input waveforms illustrated in FIGS. 6B and
7B.
[0055] If the core origin of the core 4a passes the coil origin,
the output waveform V.sub.0 of the voltage comparator 11 has a
second zero point, and it has a first zero point if the core origin
of the core 4a comes out of the bobbin 1.
[0056] FIG. 8 is a control block diagram of the linear compressor
according to an embodiment of the present invention. Hereinbelow,
the embodiment of the present invention will be described in
reference to FIGS. 4 through 8.
[0057] At operation S1, the time for the core origin of the core 4a
to exit and enter the bobbin 1 according to an inhale stroke of the
piston is measured, or the time that is taken for the output
V.sub.0 of the voltage comparator 11 having the first zero point to
have the first zero point again according to the compression stroke
is measured. Then, at operation S2, the state of the load on the
piston can be determined based on the measured result.
[0058] In operation S4, the controller 13 checks the trend of the
load. If the load decreased, the controller 13 will control the
stroke of the piston to decrease accordingly in operation S3,
however, if the state of the load is determined to be the overload,
it is decided whether the amount of the change of the load is
greater than the amount of the predetermined critical load at
operation S4 then the controller must adjust the top clearance of
the piston in operation S5.
[0059] The controller 13 increases the driving current for the
driving motor to increase the stroke of the piston if the state of
the load is determined to be the overload at operation S6. However,
the piston may collide with the valve as the piston becomes
uncontrollable with a big stroke because the driving current for
the driving motor increases when the increased amount of the load
is greater than the amount of the critical load, or because a
controlled velocity of the motor becomes lower than a changing
velocity of the load when the state of the load turns into the
steady state suddenly.
[0060] Accordingly, when the magnitude of the change of the load is
great, it is desirable to change the magnitude of the stroke slowly
by setting a target magnitude of the controlled stroke greater than
the present magnitude of the stroke by some amount rather than to
change the magnitude of the stroke of the piston abruptly by
increasing the driving current for the driving motor. However, the
collision of the piston and the valve may be prevented by
increasing the top clearance by adjusting the target magnitude of
the controlled stroke at operation S5.
[0061] The linear compressor according to this embodiment of the
present invention detects the amount of the load and controls the
cooling power based on the detected amount of the load.
[0062] Waveforms "c" and "d" in FIG. 9 are the output waveforms
V.sub.0 of the voltage comparator 11 when the external
environmental conditions of the sensor such as the temperature and
the pressure change. The waveform "d" illustrates that the zero
point does not vary even if the external conditions changed
compared to the waveform "c". Accordingly, it can be inferred that
the external environment does not affect the zero points, which
enables accurate determining the state of the load and controlling
the position of the piston based on the zero points.
[0063] This embodiment provides the present invention a control of
high quality on the stroke of the piston by determining the state
of the load regardless of the external environment.
[0064] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in this embodiment without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
* * * * *