U.S. patent application number 10/331509 was filed with the patent office on 2003-08-28 for apparatus and method of controlling linear compressor.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Choi, Jae-Young, Kim, Nam-Su, Kim, Tae-Duk.
Application Number | 20030161735 10/331509 |
Document ID | / |
Family ID | 27759813 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030161735 |
Kind Code |
A1 |
Kim, Nam-Su ; et
al. |
August 28, 2003 |
Apparatus and method of controlling linear compressor
Abstract
A linear compressor control apparatus including a position
detecting unit to detect the position of a piston and a
compensation unit to compensate for output distortion of the
position sensor. The compensation unit compensates for output
distortion of the position sensor, caused by internal temperature
of the linear compressor and load variation. Further, the
compensation unit separates a high frequency signal and a DC signal
from the output of the position detecting unit, and simultaneously
performs position and temperature detecting operations using the
separated high frequency signal and the DC signal.
Inventors: |
Kim, Nam-Su; (Seoul, KR)
; Kim, Tae-Duk; (Yongin-City, KR) ; Choi,
Jae-Young; (Seongnam-City, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon City
KR
|
Family ID: |
27759813 |
Appl. No.: |
10/331509 |
Filed: |
December 31, 2002 |
Current U.S.
Class: |
417/44.1 |
Current CPC
Class: |
F04B 2203/0405 20130101;
F04B 2201/0403 20130101; F04B 2201/0201 20130101; F04B 35/045
20130101 |
Class at
Publication: |
417/44.1 |
International
Class: |
F04B 049/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2002 |
KR |
2002-11026 |
Oct 10, 2002 |
KR |
2002-61895 |
Claims
What is claimed is:
1. An apparatus to control a linear compressor having a piston
reciprocating in a cylinder of the linear compressor, comprising: a
position detecting unit to detect a position of a piston
reciprocating in a cylinder of the linear compressor; and a
compensating unit to compensate for output distortion of the
position detecting unit due to internal temperature of the
compressor and load variation.
2. The linear compressor control apparatus according to claim 1,
wherein said position detecting unit detects the position of the
piston when alternating current (AC) power is supplied and detects
the internal temperature of the compressor when direct current (DC)
power is supplied.
3. The linear compressor control apparatus according to claim 2,
further comprising a power supply unit to selectively supply AC
power and DC power to the position detecting unit.
4. The linear compressor control apparatus according to claim 3,
wherein said power supply unit supplies the AC power to the
position sensor if the load is unstable and supplies the DC power
to the position sensor if the load is stable.
5. The linear compressor control apparatus according to claim 1,
wherein said compensation unit comprises: a temperature detecting
unit to detect the internal temperature of the linear compressor; a
resonance point shift detecting unit to detect the amount of shift
of a piston resonance point due to the load variation; a position
calculating unit to compensate for an error of a maximum stroke of
the piston detected by the position detecting unit according to the
internal temperature of the linear compressor and the amount of
shift of the piston resonance point; and an instruction value
calculating unit to output a drive instruction to drive the linear
compressor according to the maximum stroke compensated by the
position calculating unit.
6. The linear compressor control apparatus according to claim 5,
wherein said compensating unit further comprises a load amount
calculating unit to calculate the amount of load according to the
amount of shift of the piston resonance point and the instruction
value calculating unit drives the linear compressor by considering
the calculated load amount.
7. A method of controlling a linear compressor having a position
detecting unit to detect a position of a piston of the linear
compressor, comprising: supplying alternating current (AC) power to
the position detecting unit, detecting the position of the piston
according to an output of the position detecting unit, and
detecting a load according to the detected position of the piston;
supplying direct current (DC) power to the position detecting unit
and detecting internal temperature of the linear compressor
according to the output of the position detecting unit; and
compensating for output distortion of the position detecting unit
according to the detected internal temperature of the linear
compressor and the detected load.
8. The linear compressor control method according to claim 7,
wherein said internal temperature of the linear compressor is
detected when an activating time of the compressor is counted and a
counted activating time exceeds a preset time.
9. A method of controlling a linear compressor having a position
detecting unit to detect a position of a piston of the linear
compressor, comprising: detecting internal temperature of the
linear compressor; detecting the amount of shift of a resonance
point of the piston; compensating for an error of a maximum stroke
of the piston detected by the position detecting unit according to
the internal temperature of the linear compressor and the amount of
shift of the piston resonance point; and driving the linear
compressor according to the compensated maximum stroke.
10. An apparatus to control a linear compressor, comprising: a
position detecting unit to detect a position of a piston
reciprocating in a cylinder of the linear compressor; a power
supply unit to supply drive power to the position detecting unit;
and a compensating unit to compensate for output distortion of the
position detecting unit due to internal temperature of the linear
compressor.
11. The linear compressor control apparatus according to claim 10,
wherein said power supply unit supplies drive power obtained by
overlapping a high frequency signal for detecting the position of
the piston and a direct current (DC) voltage for detecting the
internal temperature of the linear compressor.
12. The linear compressor control apparatus according to claim 11,
wherein said power supply unit comprises: a high frequency signal
generating unit to generate the high frequency signal; a DC voltage
generating unit to generate the DC voltage with a predetermined
level; and an adder to overlap the DC voltage and the high
frequency signal.
13. The linear compressor control apparatus according to claim 10,
wherein said compensation unit comprises a low pass filter to
eliminate a high frequency component from an output of the position
detecting unit, and compensates for output distortion of the
position detecting unit using a signal whose high frequency
component is eliminated by the low pass filter.
14. The linear compressor control apparatus according to claim 13,
wherein said compensation unit comprises: a position calculating
unit to amplify the internal temperature information and then
correcting position information, if the temperature information
whose high frequency component is eliminated by the low pass filter
and the position information obtained from the output of the
position detecting unit have a linear relationship; and an
instruction value calculating unit to output a drive signal to
drive the linear compressor on the basis of the position
information which is corrected by the position calculating
unit.
15. The linear compressor control apparatus according to claim 13,
wherein said compensation unit further comprises: an instruction
value calculating unit to receive temperature information and
position information, respectively, correct the position
information according to the temperature information using a preset
lookup table, and output a drive signal to drive the compressor on
the basis of the corrected position information, if the temperature
information whose high frequency component is eliminated by the low
pass filter and the position information obtained from the output
of the position sensor have a non-linear relationship.
16. An apparatus to control a linear compressor, comprising: a
position detecting unit to detect a position of a piston
reciprocating in a cylinder of the linear compressor; a power
supply unit to supply drive power to the position detecting unit;
and a compensating unit to calculate the amount of shift of a
piston resonance point and a load from the position of the piston,
and compensate for output distortion of the position detecting unit
on the basis of the calculated load.
17. The linear compressor control apparatus according to claim 16,
wherein said power supply unit supplies alternating current (AC)
power to the position detecting unit.
18. The linear compressor control apparatus according to claim 5,
wherein the temperature detecting unit determines the variation of
the load according to a shift change rate of a resonance point
(.DELTA. resonance point shift data) and provides an AC supply
instruction to the power supply unit 14 when the load is unstable
so the power supply unit 14 supplies AC power, or the temperature
detecting unit 31 provides a DC supply instruction to the power
supply unit 14 when the load is stable so the power supply unit 14
supplies DC power.
19. An apparatus to control a linear compressor comprising: a high
frequency signal generating unit; a DC voltage generating unit; an
adder to add the outputs of both the high frequency signal
generating unit and the DC voltage generating unit; and a position
sensor to receive the output from the adder a provide two sensor
output signals.
20. The linear compressor control apparatus according to claim 19,
wherein the position sensor comprises: a magnetic core; and first
and second coils symmetrically would around the magnetic core.
21. The linear compressor control apparatus according to claim 19,
wherein the position sensor is connected at one end to the a high
frequency signal generating unit through a first resistor and at
another end to a potential through a second resistor.
22. The linear compressor control apparatus according to claim 21,
wherein the adder overlaps DC voltage and the high frequency signal
and supplies the overlapped voltage to the position sensor.
23. The linear compressor control apparatus according to claim 22,
further comprising: a rectifier to rectify one of the sensor output
signals; a differential amplifier to receive the rectified sensor
output signal from the position sensor and compare the rectified
signal with a preset reference signal to provide a difference
signal; a low pass filter to receive the difference signal and
provide position information; a peak detecting unit to receive the
position information and output the position information; and a
position calculating unit to receive the position information from
the peak detecting unit.
24. The linear compressor control apparatus according to claim 23,
further comprising: a low pass filter to receive the second sensor
output signal having a characteristic that a value thereof is
decreased if a surrounding temperature is increased, wherein a high
frequency signal of the second sensor output signal is varied
according to the position of the piston.
25. The linear compressor control apparatus according to claim 24,
wherein the low pass filter has a cutoff of several Hertz and
separates only a DC signal.
26. The linear compressor control apparatus according to claim 24,
further comprising: an amplifier to amplify the separated DC signal
and provide the amplified signal to the position calculating unit
as temperature information.
27. The linear compressor control apparatus according to claim 26,
wherein the position calculation unit corrects the position
information on the basis of the temperature information.
28. The linear compressor control apparatus according to claim 27,
further comprising: an instruction value calculating unit to
receive the temperature-corrected position information and convert
the temperature-corrected position information into digital
information; and a compressor driving unit driving the linear
compressor based on the digital information output received from
the instruction value calculating unit.
29. The linear compressor control apparatus according to claim 22,
further comprising: a rectifier to rectify one of the sensor output
signals; a differential amplifier to receive the rectified sensor
output signal from the rectifier and compare the rectified sensor
output signal with a preset reference signal to provide a
difference signal; a low pass filter to receive the difference
signal and provide position information; and a peak detecting unit
to receive the position information and output the position
information.
30. The linear compressor control apparatus according to claim 29,
further comprising: a low pass filter to output temperature
information from determined from the second sensor output signal
received from the position sensor, the temperature information
output having a characteristic that a value thereof is decreased if
a surrounding temperature is increased, wherein a high frequency
signal of the second sensor output signal is varied according to
the position of the piston.
31. The linear compressor control apparatus according to claim 30,
further comprising: an instruction value calculating unit to
receive the position information from the peak detecting unit and
the temperature information output from the low pass filter and
converts the position information and temperature information
signals into digital information, and corrects the position
information according to the digital temperature information; and a
compressor driving unit to drive the linear compressor according to
the information received from the instruction value calculating
unit.
32. The linear compressor control apparatus according to claim 31,
wherein the instruction value calculating unit uses a lookup table
to correct the position information by the temperature information
and the position information.
33. A linear compressor control apparatus comprising: a high
frequency signal generating unit to generate a high frequency
signal; a DC voltage generating unit to generate a DC voltage; an
adder to overlap the high frequency signal and the DC voltage
signal; and a position sensor to receive the output from the adder
and separate a high frequency signal and a DC signal to be used as
a position detection signal and a temperature detection signal,
respectively, such that position detection and temperature
detection are performed simultaneously.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Application
No. 2002-11026, filed Feb. 28, 2002, and Application No.
2002-61895, filed Oct. 10, 2002, in the Korean Intellectual
Property Office, the disclosures of which are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to an apparatus and
method of controlling a linear compressor, which compensates for
output distortion of a position sensor for detecting the position
of a piston.
[0004] 2. Description of the Related Art
[0005] FIG. 1 is a block diagram of a conventional apparatus to
control a linear compressor.
[0006] Referring to FIG. 1, the conventional control apparatus is
comprised of a magnetic core 10, first and second coils 12 and 13,
a signal processing unit 20 and a microcomputer 26. The magnetic
core 10 operates in conjunction with a mechanism whose position is
to be detected (not shown), the first and second coils 12 and 13
are symmetrically wound around the core 10, and the signal
processing unit 20 detects and outputs variations in position of
the core 10 using voltages induced to the first and second coils 12
and 13.
[0007] The signal processing unit 20 is comprised of a first
full-wave rectifying unit 21, a second full-wave rectifying unit
22, a differential amplifying unit 23, a filter unit 24, and a peak
detecting unit 25. The first full-wave rectifying unit 21 full-wave
rectifies voltage induced to the first coil 12, the second
full-wave rectifying unit 22 full-wave rectifies voltage induced to
the second coil 13, the differential amplifying unit 23 amplifies a
difference between voltages full-wave rectified by the first and
second full-wave rectifying units 21 and 22, the filter unit 24
eliminates a high-frequency component from a signal outputted from
the differential amplifying unit 23, and the peak detecting unit 25
detects the maximum and minimum values of a signal outputted from
the filter unit 24, and transmits the detected values to a
microcomputer 26.
[0008] The operation of the conventional linear compressor is
described below.
[0009] If the position of the core 10 is varied by a variation in
position of the mechanism whose position is to be detected with
alternating current (AC) having a frequency of several KHz applied
to the first and second coils 12 and 13 from the outside, voltages
in proportion to the variation in position of the core 10 are
induced to the first and second coils 12 and 13. The voltages
induced to the first and second coils 12 and 13 are full-wave
rectified by the first and second full-wave rectifying units 21 and
22 and the full-wave rectified voltages are inputted to input
terminals of the differential amplifying unit 23.
[0010] The differential amplifying unit 23 amplifies a difference
between the voltages full-wave rectified by the first and second
full-wave rectifying units 21 and 22, and outputs the amplified
difference to the filter unit 24. The filter unit 24 eliminates a
high-frequency component from the signal outputted from the
differential amplifying unit 23, and outputs the filtered signal to
the peak detecting unit 25. The peak detecting unit 25 detects a
peak of the signal outputted from the filter unit 24, that is, a
maximum stroke, and outputs the detected maximum stroke to the
microcomputer 26. The microcomputer 26 controls the stroke of the
linear compressor 1 according to the maximum stroke.
[0011] In the conventional linear compressor control apparatus, the
output control of the linear compressor is performed by controlling
the position of the piston on the basis of voltage values detected
by the first and second coils 12 and 13. However, as resistances of
the coils are increased according to a temperature, the output
value of the first and second coils 12 and 13 is also increased.
Further, the center of a resonance point of the piston is shifted
according to the variation of a load. At this time, if the center
of the resonance point of the piston moves away from the valve
relative to an initial assembled position, the output value is
decreased, while if the center thereof approaches the valve, the
output value is increased.
[0012] That is, the first and second coils 12 and 13 serve to
detect the position of the piston. In this case, the output value
of the first and second coils 12 and 13 is varied according to an
internal temperature of the compressor. Further, if the load is
varied unstably, the center of the resonance point of the piston is
shifted, so the output voltage may change.
[0013] As described above, if the position of the piston is
controlled using the voltage values detected by conventional first
and second coils, the center of the resonance point is shifted due
to the internal temperature of the compressor or the load
variation, so the output value of the coils at the same top
clearance is distorted, thus preventing an optimal top clearance
from being maintained. In the worst case, abnormal phenomena, such
as a collision of the piston of the compressor with the valve,
etc., may occur.
[0014] If the top clearance is set to be larger to avoid the
collision of the piston, the size of the compressor must be
increased in proportion to the increased top clearance so as to
obtain cooling power (output) of desired intensity, thereby causing
a burden in manufacturing a compressor.
SUMMARY OF THE INVENTION
[0015] Accordingly, it is an aspect of the present invention to
provide an apparatus and method of controlling a linear compressor,
which may compensate for a sensor output distorted due to an
internal temperature of the compressor or a load variation.
[0016] Additional aspects and 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.
[0017] The foregoing and/or other aspects of the present invention
are achieved by providing an apparatus to control a linear
compressor having a piston reciprocating in a cylinder of the
linear compressor, comprising: a position detecting unit to detect
a position of a piston reciprocating in a cylinder of the linear
compressor; and a compensating unit to compensate for output
distortion of the position detecting unit due to internal
temperature of the compressor and load variation.
[0018] The foregoing and/or other aspects of the present invention
are also achieved by providing a method of controlling a linear
compressor having a position detecting unit to detect a position of
a piston of the linear compressor, comprising: supplying
alternating current (AC) power to the position detecting unit,
detecting the position of the piston according to an output of the
position detecting unit, and detecting a load according to the
detected position of the piston; supplying direct current (DC)
power to the position detecting unit and detecting internal
temperature of the linear compressor according to the output of the
position detecting unit; and compensating for output distortion of
the position detecting unit according to the detected internal
temperature of the linear compressor and the detected load.
[0019] The foregoing and/or other aspects of the present invention
are also achieved by providing a method of controlling a linear
compressor having a position detecting unit to detect a position of
a piston of the linear compressor, comprising: detecting internal
temperature of the linear compressor; detecting the amount of shift
of a resonance point of the piston; compensating for an error of a
maximum stroke of the piston detected by the position detecting
unit according to the internal temperature of the linear compressor
and the amount of shift of the piston resonance point; and driving
the linear compressor according to the compensated maximum
stroke.
[0020] The foregoing and/or other aspects of the present invention
are also achieved by providing an apparatus to control a linear
compressor, comprising a position detecting unit to detect a
position of a piston reciprocating in a cylinder of the linear
compressor; a power supply unit to supply drive power to the
position detecting unit; and a compensating unit to compensate for
output distortion of the position detecting unit due to internal
temperature of the linear compressor.
[0021] The foregoing and/or other aspects of the present invention
are also achieved by providing an apparatus to control a linear
compressor, comprising: a position detecting unit to detect a
position of a piston reciprocating in a cylinder of the linear
compressor; a power supply unit to supply drive power to the
position detecting unit; and a compensating unit to calculate the
amount of shift of a piston resonance point and a load from the
position of the piston, and compensate for output distortion of the
position detecting unit on the basis of the calculated load.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] These and other aspects and advantages of the invention will
become apparent and more readily appreciated from the following
description of the preferred embodiments, taken in conjunction with
the accompanying drawings of which:
[0023] FIG. 1 is a block diagram of a conventional apparatus to
control a linear compressor;
[0024] FIG. 2 is a block diagram of an apparatus to control a
linear compressor according to an embodiment of the present
invention;
[0025] FIG. 3 is a circuit diagram to receive AC power for
detecting the position of a piston in the control apparatus of the
linear compressor of FIG. 2;
[0026] FIG. 4 is a circuit diagram to receive DC power for
detecting the internal temperature of the compressor in the control
apparatus of the linear compressor of FIG. 2;
[0027] FIG. 5 is a circuit diagram of a resonance point shift
detecting unit in the control apparatus of the linear compressor of
FIG. 2;
[0028] FIG. 6 is a graph illustrating errors of a sensor output due
to an internal temperature of the linear compressor of FIG. 2;
[0029] FIG. 7 is a graph illustrating compensated strokes
corresponding to the amount of shift of a resonance point according
to conditions of the control apparatus of the linear compressor of
FIG. 2;
[0030] FIG. 8 is a flowchart of a temperature detecting routine
according to an embodiment of the present invention;
[0031] FIG. 9 is a flowchart of a position calculating routine
according to an embodiment of the present invention;
[0032] FIG. 10 is a flowchart of a load amount calculating routine
according to an embodiment of the present invention;
[0033] FIG. 11 is a block diagram of another apparatus to control a
linear compressor according to another embodiment of the present
invention; and
[0034] FIG. 12 is a block diagram of a further apparatus to control
a linear compressor according to a modified embodiment of FIG. 11
to illustrate the operation of correcting position information
according to inputted temperature information by an instruction
value calculating unit of FIG. 11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] 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
like elements throughout. The embodiments are described below in
order to explain the present invention by referring to the
figures.
[0036] A first embodiment is described with respect to a case where
output distortion of a position sensor is compensated by
considering both an internal temperature of a compressor and a
load, and a second embodiment is described with respect to a case
where output distortion of a position sensor is compensated by
considering only an internal temperature of the compressor.
[0037] FIG. 2 is a block diagram of an apparatus to control a
linear compressor according to an embodiment of the present
invention. The same reference numerals as those of FIG. 1 are used
in FIG. 2 to designate the same or similar components.
[0038] Referring to FIG. 2, the linear compressor control apparatus
includes a magnetic core 10 to operate in conjunction with a
mechanism whose position is to be detected, and a position
detecting unit having first and second coils 12 and 13
symmetrically wound around the outer side of the core 10.
[0039] A position detecting unit 20 includes first and second
rectifying units 21 and 22, a differential amplifying unit 23, a
filter unit 24 and a peak detecting unit 25. The first rectifying
unit 21 full-wave rectifies a voltage induced to the first coil 12,
and the second rectifying unit 22 full-wave rectifies a voltage
induced to the second coil 13. The differential amplifying unit 23
amplifies a difference between voltages full-wave rectified by the
first and second rectifying units 21 and 22. The filter unit 24
eliminates a high-frequency component from an output signal of the
differential amplifying unit 23. The peak detecting unit 25 detects
a maximum stroke from an output signal of the filter unit 24.
[0040] The position detecting unit further includes a power supply
unit 14 to supply a alternating current (AC) power or direct
current (DC) power to one-side ends of the first and second coils
12 and 13 connected in series.
[0041] The linear compressor control apparatus of the present
invention comprises a compensating unit 30 to compensate for output
distortion of the position detecting unit due to the internal
temperature of the linear compressor and load variation.
[0042] The compensating unit 30 comprises a temperature detecting
unit 31, a resonance point shift detecting unit 32, a position
calculating unit 33, a load amount calculating unit 34 and an
instruction value calculating unit 35.
[0043] The power supply unit 14 serves to supply AC power to detect
the piston of the piston, or DC power to detect internal
temperature of the compressor. This power supply unit 14 supplies
one of the AC power and the DC power according to an output signal
of the temperature detecting unit 31.
[0044] The temperature detecting unit 31 determines the variation
of the load according to a shift change rate of a resonance point
(.DELTA. resonance point shift data) and provides an AC supply
instruction to the power supply unit 14 when the load is unstable,
so the power supply unit 14 supplies AC power, as illustrated in
FIG. 3. On the other hand, when the load is stable, the temperature
detecting unit 31 provides a DC supply instruction to the power
supply unit 14, so the power supply unit 14 supplies DC power, as
illustrated in FIG. 4.
[0045] A case where the power supply unit 14 supplies AC power is
modeled as illustrated in a circuit diagram of FIG. 3. AC power Vac
is supplied to one-side ends of the first and second coils 12 and
13 connected in series. Inductance L1 of the first coil 12 and
inductance L2 of the second coil 13 vary according to the variation
of the position of the core 10, which operates in conjunction with
the piston. Therefore, a voltage proportional to the variations of
the inductances L1 and L2 is outputted through resistors R1 and R2,
a rectifying diode D1 and a capacitor C. The output voltage is
induced to the first and second coils 12 and 13, respectively. The
induced voltages are provided to the first and second rectifying
units 21 and 22 and the temperature detecting unit 31 as
information used to detect the position of the piston.
[0046] A case where the power supply unit 14 supplies DC power is
modeled as illustrated in a circuit diagram of FIG. 4. In this
case, DC power Vdc is supplied to one-side ends of the first and
second coils 12 and 13 connected in series. Inductance L1 of the
first coil 12 and inductance L2 of the second coil 13 vary
according to the temperature of the linear compressor (internal
temperature of the linear compressor). Therefore, a voltage
proportional to the variations of the inductances L1 and L2 is
outputted through the resistors R1 and R2, the rectifying diode D1
and the capacitor C. The output voltage is induced to the first and
second coils 12 and 13, respectively. The induced voltages are
provided to the first and second rectifying units 21 and 22 and the
temperature detecting unit 31 as information used to detect the
temperature of the linear compressor.
[0047] The temperature detecting unit 31 converts a temperature
detecting signal corresponding to the induced voltages into digital
temperature data, and outputs the temperature data to the position
calculating unit 33.
[0048] If the power supply unit 14 supplies AC power, voltages
proportional to variation of the position of the core 10 are
induced to the first and second coils 12 and 13. The induced
voltages are full-wave rectified by the first and second rectifying
units 21 and 22, and then inputted to input terminals of the
differential amplifying unit 23. The differential amplifying unit
23 amplifies a difference between the inputted voltages and outputs
the amplified result to the filter unit 24. The filter unit 24
eliminates a high-frequency component from the amplified output
signal and outputs the eliminated result to both the resonance
point shift detecting unit 32 and the peak detecting unit 25. The
peak detecting unit 25 detects a maximum stroke of the piston and
outputs the detected result as maximum stroke data to the position
calculating unit 33.
[0049] FIG. 5 is a circuit diagram of the resonance point shift
detecting unit 32 according to an embodiment of the present
invention. The resonance point shift detecting unit 32 comprises an
operational amplifier OP, resistors Ra, Rb and Rc, and a capacitor
Ca.
[0050] The resonance point shift detecting unit 32 detects
resonance point shift data indicating a shifting state of the
center of the resonance point from the signal provided by the
filter unit 24, and outputs the resonance point shift data to the
position calculating unit 33 and the load amount calculating unit
34.
[0051] As illustrated in FIG. 6, as an internal temperature of the
compressor becomes high, a compensated sensor output S1, that is,
each of voltages induced to the first and second coils 12 and 13,
becomes larger than a sensor output S2 which is not compensated.
Therefore, as the internal temperature of the compressor becomes
high, an error of the sensor output becomes larger, thus requiring
a method of coping with such an error.
[0052] As illustrated in FIG. 7, the compensated strokes
corresponding to the amount of shift of the resonance point
increase. In this case, differences between suction pressure and
discharge pressure of the compressor satisfy the relation
G1>G2>G3>G4.
[0053] The position calculating unit 33 compensates for an error of
the top clearance using the maximum stroke data obtained by
converting the maximum stroke calculated on the basis of maximum
values and minimum values of the output signal of the filter unit
24 into digital data, the temperature data obtained by converting
the temperature detecting signal outputted from the temperature
detecting unit 31 into digital data, and the resonance point shift
data obtained by converting the resonance point shift signal
outputted from the resonance point shift detecting unit 32 into
digital data. Further, the position calculating unit 33 outputs
compensated top clearance information to the instruction value
calculating unit 35.
[0054] The load amount calculating unit 34 outputs an instruction
value determined according to the resonance point shift data
outputted from the resonance point shift detecting unit 32 and a
preset value to the instruction value calculating unit 35.
[0055] The instruction value calculating unit 35 outputs a drive
signal to drive the linear compressor 37 to the compressor driving
unit 36 according to the top clearance outputted from the position
calculating unit 33 and the instruction value outputted from the
load amount calculating unit 34.
[0056] The compressor driving unit 36 drives the linear compressor
37 according to the drive signal outputted from the instruction
value calculating unit 35.
[0057] A control method of the linear compressor control apparatus
having the above construction according to an embodiment of the
present invention is herein described below in detail.
[0058] FIG. 8 illustrates a temperature detecting routine performed
by the temperature detecting unit 31. First, when the power supply
unit 14 supplies AC power, the temperature detecting unit 31
calculates a shift change rate of the resonance point (.DELTA.
resonance point shift data) from the signal outputted from the
circuit of FIG. 3 at operation S10. In this case, the resonance
point shift change rate is calculated by the following
equation.
.DELTA. resonance point shift data=previous resonance point shift
data-current resonance point shift data
[0059] The temperature detecting unit 31 determines whether an
activating time of the linear compressor, which is counted using a
first counter (not shown), exceeds a preset time A at operation
S11. If the compressor activating time exceeds the preset time A,
the temperature detecting unit 31 determines whether the resonance
point shift change rate (.DELTA. resonance point shift data) is
less than a preset change rate B at operation S12. A time after the
time point of the determination is counted using a second counter
(not shown).
[0060] If the resonance point shift change rate is less than the
preset change rate B according to the determined result at
operation S12, the temperature detecting unit 31 determines whether
the counted time by the second counter reaches a preset time D at
operation S13. If the counted time by the second counter reaches
the preset time D, the temperature detecting unit 31 outputs a dc
signal DC to the power supply unit 14 to allow the power supply
unit 14 to supply DC power. In this way, as the DC power is
supplied, the temperature detecting unit 31 performs an operation
of providing temperature data obtained by converting a signal
proportional to the voltages induced to the first and second coils
12 and 13 into digital data to the position calculating unit 33,
that is, a temperature sensing operation at operation S14.
[0061] If the compressor activating time does not exceed the preset
time A at operation S11, if the resonance point shift change rate
(.DELTA. resonance point shift data) is not less than the preset
change rate B at operation S12, and if the counted time does not
reach the preset time D at operation S13, the temperature detecting
unit 31 outputs an ac signal AC to the power supply unit 14 to
allow the power supply unit 14 to supply AC power.
[0062] FIG. 9 illustrates a position calculating routine performed
by the position calculating unit 33. First, the position
calculating unit 33 receives the temperature data from the
temperature detecting unit 31, the resonance point shift data from
the resonance point shift detecting unit 32, and piston position
information, which is outputted from the peak detecting unit 25
when the power supply unit 14 supplies AC power, that is, maximum
stroke data at operation S20.
[0063] The position calculating unit 33 searches a lookup table for
a maximum stroke corresponding to the temperature data and the
resonance point shift data at operation S21. Then, the position
calculating unit 33 outputs the searched maximum stroke, that is, a
maximum stroke compensated according to the internal temperature of
the compressor and the amount of shift of the resonance point, to
the instruction value calculating unit 35 at operation S22. This
means that an error of the sensor output due to the internal
temperature of the compressor and the amount of shift of the
resonance point is corrected when the linear compressor is driven
with the compensated maximum stroke. Consequently, the error
correction of the sensor output results in the compensation of an
error of the top clearance.
[0064] The linear compressor has excellent characteristics in
variance of its capacity compared with conventional AC motors.
Therefore, the capacity of the linear compressor may be varied
appropriately according to load information calculated by the load
amount calculating unit 34.
[0065] FIG. 10 illustrates a load amount calculating routine
performed by the load amount calculating unit 34. First, the load
amount calculating unit 34 determines whether the activating time
of the compressor exceeds a preset time C at operation S30. If the
compressor activating time exceeds the preset time C, the load
amount calculating unit 34 compares resonance point shift
information, that is, the resonance point shift data received from
the resonance point shift detecting unit 32, with a preset value,
determines an instruction value corresponding to a load state, and
outputs the determined instruction value to the instruction value
calculating unit 35 at operation S31. If the compressor activating
time does not exceed the preset time C, the load amount calculating
unit 34 determines an instruction value for a normal load condition
in an initial operation of the compressor and outputs the
instruction value to the instruction value calculating unit 35 at
operation S32.
[0066] As described above, the instruction value calculating unit
35 outputs a drive instruction to drive the linear compressor to
the compressor driving unit 36 using the instruction value
determined according to the maximum stroke compensated by the
position calculating unit 33 and the load information calculated by
the load amount calculating unit 34.
[0067] The previous embodiment compensates for output distortion of
the position sensor by considering an internal temperature of the
compressor and the amount of a load, wherein the power supply unit
must alternately supply AC power and DC power according to the
condition of a load.
[0068] However, if a power supply period is short (for example, 120
Hz), a compensation process considering both of a temperature and a
load is complicated. Accordingly, in the following embodiment as
described below, drive power obtained by overlapping a DC voltage
and a high frequency signal is supplied to the position sensor so
as to simultaneously perform an operation of detecting the position
of a piston and an operation of detecting the internal temperature
of the compressor, a high frequency signal and a DC signal are
separated from the signal outputted from the position sensor, the
separated high frequency signal being used as a position detection
signal, and the separated DC signal is used as a temperature
detection signal, thus enabling position information and
temperature info information to be simultaneously obtained.
[0069] FIG. 11 is a block diagram of an apparatus to control a
linear compressor according to another embodiment of the present
invention. The linear compressor control apparatus of this
embodiment uses a manner of overlapping a signal used to obtain
position detection (signal with a frequency higher than several
KHz) and a signal used to obtain temperature detection (certain DC
voltage).
[0070] As illustrated in FIG. 11, the linear compressor control
apparatus of this embodiment includes a high frequency signal
generating unit 61, a DC voltage generating unit 63 and an adder 65
which supply power to a position sensor 67.
[0071] The position sensor 67 includes a magnetic core, and first
and second coils symmetrically wound around the outer side of the
magnetic core. The position sensor 67 is connected to resistors R1
and R2, and is connected to the adder 65 through the resistor
R1.
[0072] The high frequency signal generating unit 61 supplies a high
frequency signal (several KHz) to the adder 65, and the DC voltage
generating unit 63 supplies a certain DC voltage to the adder 65.
The adder 65 overlaps the certain DC voltage and the high frequency
signal, and supplies the overlapped voltage to the position sensor
67.
[0073] One output from the position sensor 67 is inputted to a
differential amplifier 69 through a rectifier 68. The differential
amplifier 69 compares a sensor output signal rectified by the
rectifier 68 and a preset reference signal. On the basis of the
comparison result, a difference between the two input signals is
calculated and a difference signal is outputted to a low pass
filter 71. A signal outputted from the low pass filter 71 is used
as position information. Such position information is a signal (for
example, 60 Hz) used to detect the position of the piston, which is
provided to a position calculating unit 79 through a peak detecting
unit 73.
[0074] The other output from the position sensor 67, having a
characteristic that its value is decreased if a surrounding
temperature is increased, is provided to a temperature detecting
low pass filter 75. In this case, a high frequency signal of the
output value is varied according to the position of the piston.
Therefore, a low pass filter having a cut-off frequency of several
Hz is used as the low pass filter 75. The low pass filter 75
separates only a DC signal from the inputted signal. The separated
DC signal is amplified to an appropriate level by an amplifier 77
for the purpose of signal processing. The amplified signal is
provided to the position calculating unit 79 as temperature
information.
[0075] The position calculating unit 79 corrects the position
information on the basis of the temperature information, and
provides the temperature-corrected position information to an
instruction value calculating unit 81. The instruction value
calculating unit 81 converts the temperature-corrected position
information into digital information, and outputs a control signal
to a compressor driving unit 83 to drive the compressor on the
basis of the digital position information. Accordingly, the
compressor driving unit 83 outputs a drive signal to the compressor
to drive the compressor.
[0076] However, as a temperature increases, the value of the
position information increases, while the value of the temperature
information decreases. The temperature information and the position
information must have a linear relationship in order for the
position calculating unit 79 to employ a manner in which the
position information is added to the amplified temperature
information to correct the position information.
[0077] Therefore, a modified embodiment shown in FIG. 12 is applied
to the present invention to provide against a case where the
temperature information and the position information do not have a
linear relationship.
[0078] FIG. 12 is a block diagram of another embodiment of an
apparatus to control a linear compressor according to a modified
embodiment of FIG. 11 to illustrate the operation of correcting
position information according to inputted temperature information
by an instruction value calculating unit of FIG. 11.
[0079] Referring to FIG. 12, the linear compressor control
apparatus employs a method in which a signal used to obtain
position detection (several KHz), generated by the high frequency
signal generating unit 61, and a signal used to obtain temperature
detection (certain DC voltage), generated by the DC voltage
generating unit 63, are overlapped by the adder 65, and the
overlapped signal is provided to the position sensor 67. One output
from the position sensor 67 passes through the rectifier 68, the
differential amplifier 69, the low pass filter 71 and the peak
detecting unit 73, and is provided to an instruction value
calculating unit 81a as position information. The other output from
the position sensor 67 passes through the low pass filter 75, and
is provided to the instruction value calculating unit 81a as
temperature information.
[0080] The instruction value calculating unit 81a converts the
position information and the temperature information into digital
information, respectively, and corrects the position information
according to the digital temperature information. In this case, the
instruction value calculating unit 81a uses a preset lookup table
to correct the position information by the temperature information
and the position information which have a non-linear relationship.
Temperature-corrected position information is provided to the
compressor driving unit 83. The compressor driving unit outputs a
drive signal to the compressor to drive the compressor.
[0081] Even though not described in the above embodiment, it is
possible to compensate for output distortion of the position sensor
by considering only a load variation, which may be easily
appreciated by those skilled in the field from the embodiment of
FIG. 2.
[0082] As described above, the present invention provides an
apparatus and method of controlling a linear compressor, which
compensates for distortion of a sensor output caused by the
shifting of the center of a resonance point due to internal
temperature of the compressor and load variation in driving the
linear compressor according to the position of a piston, thus
enabling the linear compressor to be controlled with an optimal top
clearance and consequently improving control accuracy. Further, the
present invention varies the capacity of the compressor
appropriately on the basis of load information obtained according
to resonance point shift data, thereby enabling the linear
compressor to actively cope with load variation by itself, and
consequently reducing power consumption.
[0083] Further, the present invention is advantageous in that a
high frequency signal and a DC voltage are overlapped to be
provided to a position sensor, a high frequency signal and a DC
signal are separated from an output of the position sensor, and the
separated high frequency signal and the DC signal are used as a
position detection signal and a temperature detection signal,
respectively, thus enabling position detection and temperature
detection to be simultaneously performed, and easily implementing
hardware for position and temperature detection.
[0084] 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 to the above embodiments
without departing from the principles and spirit of the invention,
the scope of which is defined in the claims and their
equivalents.
* * * * *