Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Reexamination Certificate
2001-11-21
2003-04-01
Oda, Christine (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
C417S044110
Reexamination Certificate
active
06541953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for detecting the shaking of stroke of a linear compressor, and more particularly, to an apparatus for detecting the shaking of the stroke of a linear compressor, which is capable of operating a linear compressor at the maximum efficiency point by detecting the shaking of the stroke using the amount of change in the phase differences of the stroke and current, and a method therefor.
2. Description of the Background Art
In general, a compressor increases the pressure of refrigerant vapor so that the refrigerant vapor evaporated by an evaporator can be easily condensed. Refrigerant circulates in a freezer, repeating processes of condensation and evaporation and carries heat from a cold place to a warm place due to the operation of the compressor.
Various types of compressors are used. However, the most efficient compressor is a linear compressor. The linear compressor compresses vapor by a piston that moves reciprocally in a cylinder to thus increase pressure. When the linear compressor is used in a refrigerator or an air conditioner, it is possible to change a compression ratio by changing a stroke voltage applied to the linear compressor, to thus control variable cooling capacity.
FIG. 1
is a block diagram showing the structure of a control apparatus of a conventional linear compressor.
As shown in
FIG. 1
, the control apparatus of the linear compressor includes a linear compressor
30
, for controlling the cooing capacity (the caloric value taken away by surroundings when 1 Kg of refrigerant evaporates, while passing through the evaporator and performing a cooling operation), whose unit is Kcal/Kg, by changing the stroke due to the reciprocating motion of a piston, which is caused by the stroke voltage according to an initial stroke reference value, a voltage/current detector
40
for detecting the voltage and the current generated by the linear compressor
30
as the stroke increases due to the stroke voltage, a stroke calculator
50
for calculating the stroke using the voltage and the current detected from the voltage/current detector
40
, a comparator
10
for receiving the stroke reference value calculated by the stroke calculator
50
at a predetermined point of time and the initial stroke reference value, comparing the stroke reference value with the initial stroke reference value, and outputting a comparison signal, and a stroke controller
20
for increasing or decreasing the stroke voltage according to the comparison signal of the comparator and applying the stroke voltage to the linear compressor
30
.
In the linear compressor according to the conventional technology, the principle of the operation of the apparatus for detecting the shaking of the stroke will now be described with reference to FIG.
1
.
When the stroke voltage according to the initial stroke reference value set by a user is output, the stroke varies according to the reciprocating motion of the piston inside the cylinder of the linear compressor
30
. Accordingly, refrigerant gas inside the cylinder is discharged to a condenser through a discharge valve, to thus control the cooling capacity of the linear compressor. At this time, the voltage/current detector
40
detects the voltage and the current generated by the linear compressor
30
as the stroke increases due to the stroke voltage of the stroke controller
20
and inputs the detected voltage an current to the stroke calculator
50
. Then, the stroke calculator
50
calculates the stroke at the predetermined point of time using the voltage and the current, which are detected by the voltage/current detector
40
and outputs the calculated value to the comparator
10
.
The stroke is calculated as follows.
STROKE
=
1
α
∫
(
V
M
-
R
a
c
i
-
L
ⅆ
i
ⅆ
t
)
ⅆ
t
wherein, &agr;, V
M
, R
ac
, and
L
ⅆ
i
ⅆ
t
refer to a constant for converting electrical force into mechanical force, a voltage between both ends of a motor, a loss value due to resistance such as copper loss and core loss, and a voltage applied to an inductor in the motor, respectively.
The comparator
10
compares the stroke at the predetermined point of time, which is output from the stroke calculator
50
with the initial stroke reference value set by the user and inputs the comparison value to the stroke controller. The stroke controller
20
changes the stroke voltage according to the comparison value and applies the stroke voltage to the linear compressor
30
.
At this time, the stroke controller
20
increases the stroke voltage when the stroke at the predetermined point of time, which is calculated by the stroke calculator
50
, is smaller than the initial stroke reference value and reduces the stroke voltage when the stroke at the predetermined point of time is larger than the initial stroke reference value, to thus control the stroke voltage applied to the linear compressor
30
.
The stroke controller
20
obtains difference between the previous stroke value of the linear compressor
30
and the stroke value at the predetermined point of time and determines that the shaking of the stroke (a phenomenon where the performance of the piston becomes unstable due to the characteristic of the compressor when the same input is applied by the specific stroke in a state where disturbance, that is, change in a voltage or noise does not exist) when the difference is no less than a reference value for determining whether the shaking of the stroke is detected. The stroke controller
20
obtains the difference between the previous current generated by the linear compressor
30
and the current at the predetermined point of time and determines that the shaking of the stroke occurs when the difference is no less than the reference value for determining whether the shaking of the stroke is detected. Accordingly, the stroke controller
20
increases or reduces the stroke voltage applied to the linear compressor
30
.
That is, when the shaking of the stroke is detected in the air conditioner or the refrigerator that requires the large cooling capacity due to the controlling of a temperature by a user, the stroke controller
20
increases the stroke voltage so that the linear compressor
30
operates right above an area, in which the stroke shakes. When the shaking of the stroke is detected in the case where the small cooling capacity is required, the stroke controller
20
reduces the stroke voltage so that the linear compressor
30
operates right below the area, in which the stroke shakes.
However, according to the control apparatus of the conventional linear compressor, the maximum efficiency point of the operation of the compressor cannot be found out due to the change in an external voltage or external noise without being caused by the characteristic of the compressor because the shaking of the stroke is detected by the amount of change in the stroke or the current.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an apparatus for detecting the shaking of stroke of a linear compressor, which is capable of preventing the linear compressor from mis-operating due to change in an external voltage or noise by detecting the shaking of the stroke by the amount of change in the phase differences of the stroke and current, and a method therefor.
Another object of the present invention is to provide an apparatus for detecting the shaking of stroke of a linear compressor, which is capable of preventing the linear compressor from mis-operating due to change in an external voltage or noise by detecting the shaking of the stroke by the amount of change the phase differences of a voltage and current, and a method therefor.
Still another object of the present invention is to provide an apparatus for detecting the shaking of stroke of a linear compressor, which is capable of preventing the linear compressor from mis-operating due to change in an external voltage or noise by detecting the shaking of the strok
Hwang Min Kyu
Lee Chel Woong
Lee Jae Chun
Yoo Yoo Jae
Fleshner & Kim LLP
He Amy
LG Electronics Inc.
Oda Christine
LandOfFree
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