U.S. patent number 3,890,798 [Application Number 05/496,897] was granted by the patent office on 1975-06-24 for refrigerator control apparatus.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Ryoichi Fujimoto, Fumiyuki Inose, Kenji Maio, Kazuo Takasugi, Norio Yokozawa.
United States Patent |
3,890,798 |
Fujimoto , et al. |
June 24, 1975 |
Refrigerator control apparatus
Abstract
A refrigerator control apparatus comprising an electronic timer
including first, second and third counters in which clock signals
are applied to the input stage of the first counter, the output
from the first counter is applied to the input stages of the second
and third counters, the overload time of a compressor is controlled
by a timing signal picked up from an intermediate stage of the
first counter, the suspension time of the compressor is controlled
by a timing signal picked up from the output stage of the second
counter, the defrosting suspension time is controlled by a timing
signal picked up from the output stage of the third counter, and
the output pulses of the first counter are counted by the third
counter only during the running of the compressor.
Inventors: |
Fujimoto; Ryoichi (Tochigi-ken,
JA), Takasugi; Kazuo (Higashiyamato, JA),
Inose; Fumiyuki (Kokubunji, JA), Maio; Kenji
(Kokubunji, JA), Yokozawa; Norio (Fuchu,
JA) |
Assignee: |
Hitachi, Ltd.
(JA)
|
Family
ID: |
14860520 |
Appl.
No.: |
05/496,897 |
Filed: |
August 12, 1974 |
Foreign Application Priority Data
|
|
|
|
|
Nov 5, 1973 [JA] |
|
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48-123436 |
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Current U.S.
Class: |
62/155; 62/156;
62/234; 62/157; 62/276 |
Current CPC
Class: |
F25D
21/006 (20130101); F25B 49/00 (20130101); H02H
7/08 (20130101); F25B 2700/151 (20130101); F25D
2700/12 (20130101) |
Current International
Class: |
F25D
21/00 (20060101); H02H 7/08 (20060101); F25B
49/00 (20060101); F25d 021/06 () |
Field of
Search: |
;62/155,156,159,234,276 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Perlin; Meyer
Attorney, Agent or Firm: Craig & Antonelli
Claims
We claim:
1. A refrigerator control apparatus comprising: an electronic timer
including first, second and third counters, a clock signal being
applied to the input stage of said first counter, the output of
said first counter being applied to the input stage of said second
counter; means for picking up a first timing signal from a
predetermined stage of said first counter; means for picking up a
second timing signal from the output stage of said second counter;
means for picking up a third timing signal from the output stage of
said third counter; means for controlling the overload time of a
compressor in response to said first timing signal; means for
controlling the suspension time of said compressor in response to
said second timing signal; means for controlling the defrosting
suspension time in response to said third timing signal; and means
for applying the output of said first counter to said third counter
during the running time of said compressor.
2. A refrigerator control apparatus according to claim 1, further
comprising means for picking up a fourth timing signal from a
predetermined stage of said third counter, means for controlling a
maximum defrosting time in response to said fourth timing signal,
and means for applying the output of said first counter to said
third counter during the defrosting cycle.
3. A refrigerator control apparatus comprising: first, second and
third counters each including a multiple of stages of flip-flops
connected in cascade; means for applying a clock signal to the
input stage of said first counter; means for applying the output
from the output stage of said first counter to the input stage of
said second counter; devices to be controlled including a
compressor drive motor and a defrosting heater; first and second
drive means for driving said compressor drive motor and said
defrosting heater respectively; first and second flip-flops
producing outputs for controlling said first and second drive
means; a temperature sensor for detecting the reaching of a
predetermined temperature of the inner space of the refrigerator;
an overload sensor for detecting an overcurrent in said compressor;
a defrosting completion sensor for detecting the completion of a
defrosting operation; a first OR gate impressed with the outputs
from said first and second flip-flops; a first AND gate impressed
with the output from the output stage of said first counter and the
output of said first OR gate, said first AND gate applying its
output to the input stage of said third counter; means for picking
up a first timing signal from a predetermined stage of said first
counter; means for picking up a second timing signal from the
output stage of said second counter; means for picking up a third
timing signal from the output stage of said third counter; a second
AND gate impressed with the output of said overload sensor and said
first timing signal from said first counter; a second OR gate
impressed with the output of said second AND gate and the output of
said temperature sensor, said second OR gate producing an output
for resetting said first flip-flop and said second counter; means
for setting said first flip-flop in response to said second timing
signal from said second counter; means for setting said second
flip-flop in response to said third timing signal from said third
counter; and means for resetting said second flip-flop in response
to the output from said defrosting completion sensor.
4. A refrigerator control apparatus according to claim 3, further
comprising means for picking up a fourth timing signal from a
predetermined stage of said third counter and a third OR gate
impressed with said fourth timing signal and the output of said
defrosting completion sensor, said third OR gate producing an
output for resetting said second flip-flop.
5. A refrigerator control apparatus according to claim 3, further
comprising means for applying the output of said second flip-flop
to said second OR gate.
6. A refrigerator control apparatus according to claim 3, further
comprising a fan motor to be controlled, third drive means for
driving said fan motor, a third flip-flop producing an output for
controlling said third drive means, means for setting said third
flip-flop in response to the output from said first flip-flop, and
means for resetting said third flip-flop in response to the output
of said second flip-flop.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a refrigerator control apparatus
employing an electronic timer for controlling the time of starting
and stopping of the compressor, initiation and termination of a
defrosting operation and other functions considered required of a
refrigerator.
2. Description of the Prior Art
A conventional widely used timer of this type is such that a timing
signal is obtained by counting clock pulses derived from a signal
of predetermined frequencies such as from a power supply of
commercial frequencies, and such a timing signal is used to control
various devices including a clock.
The timing control required of a refrigerator includes:
1. CONTROL OF A TIME PERIOD DURING WHICH AN EXCESSIVE CURRENT FLOWS
IN THE STARTING OF THE COMPRESSOR (HEREINAFTER REFERRED TO AS THE
"COMPRESSOR OVERLOAD TIME");
2. CONTROL OF A TIME PERIOD FROM A TIME POINT WHEN THE COMPRESSOR
IS STOPPED TO A TIME POINT WHEN IT IS REACTUATED (HEREINAFTER
REFERRED TO AS THE "COMPRESSOR SUSPENSION TIME");
3. CONTROL OF A TIME PERIOD BEFORE STARTING OF A DEFROSTING PROCESS
(HEREINAFTER REFERRED TO AS THE "DEFROSTING SUSPENSION TIME");
AND
4. CONTROL OF A MAXIMUM DEFROSTING TIME PERMITTED UNTIL COMPLETION
OF DEFROSTING.
The periods of time involved in (1), (2), (3) and (4) above are on
the order of several seconds, several minutes, several to several
tens of hours and several tens of minutes respectively.
Even though a timer may be provided for each of the different types
of timing controls, the multiplication of as many different types
of timers as the types of timing signals involved is not desirable
from the viewpoint of not only economy but reliability.
Further, the amount of frost grown on the cooling system of the
refrigerator is generally proportional to the running time of the
compressor. The automatic starting of defrosting following a
predetermined defrosting suspension time poses no problem as far as
the starting and stopping of the compressor is effected at regular
intervals of time. Irregular time intervals of compressor
operation, however, which may be caused by a prolonged state of an
open door or changes in the environmental temperature, leads to
such an inconvenience that a defrosting operation is started long
before or after a predetermined running time of the compressor,
thus making it impossible to start the defrosting process at an
optimum time point.
SUMMARY OF THE INVENTION
A first object of the invention is to provide an economical and
reliable refrigerator control apparatus which permits various types
of timing control with a timer comprising only a few counters.
Another object of the invention is to provide a refrigerator
control apparatus which is capable of optimum defrosting operation
by accumulating the running time of the compressor.
In order to achieve the above-mentioned objects, there is provided
according to the invention a refrigerator control apparatus
comprising an electronic timer including first, second and third
counters; in which clock pulses are applied to the input stage of
the first counter, the output from the first counter is applied to
the input stages of the second and third counters, the compressor
overload time is controlled by a timing signal picked up from a
predetermined stage of the first counter, the compressor suspension
time is controlled by a timing signal picked up from the output
stage of the second counter, a maximum defrosting time is
controlled by a timing signal picked up from a predetermined stage
of the third counter, the defrosting suspension time is controlled
by a timing signal picked up from the output stage of the third
counter, and the output pulses of the first counter are counted by
the third counter only during the running of the compressor.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram showing the refrigerator control
apparatus according to an embodiment of the invention.
FIG. 2 is a block diagram showing an actual construction of the
control circuit included in the apparatus of FIG. 1.
FIG. 3 is a block diagram showing an actual example of a more
detailed construction of the control circuit of FIG. 2.
FIG. 4 is a block diagram showing an example of the actual
construction of the timer shown in FIG. 3.
FIG. 5 is a waveform diagram for explaining the operation of the
timer of FIG. 4.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Referring to FIG. 1 showing a schematic diagram of an embodiment of
the invention, reference numeral 1 shows a power source, numeral 2
a motor for driving a compressor which cools the space inside of
the refrigerator, numeral 3 a fan motor for circulating cool air
inside of the refrigerator, and numeral 4 a defrosting heater for
melting frost grown on the cooling system. Reference numerals 20,
30 and 40 show control elements comprising semiconductor switch
elements for controlling the on-off operation of the compressor
drive motor 2, fan motor 3 and defrosting heater 4 respectively.
Numerals 21, 31 and 41 show signal lines for turning on and off the
control elements 20, 30 and 40 respectively. Reference numeral 5
shows a control circuit including an electronic timer, numeral 6 a
power source circuit therefor, and numeral 7 a clock pulse
generator circuit for applying clock pulses to the timer circuit.
Numeral 8 shows a sensor circuit for applying a signal to the
control circuit 5 and includes means for detecting temperatures in
the refrigerator and current in the circuits.
The control operations in the embodiment under consideration are
effected as follows:
1. When the compressor drive motor 2 is actuated by turning on the
control element 20, the control circuit 5 detects the duration of
the starting current (which is usually several times the normal
operating current (which is usually several times the normal
operating current) which is in turn detected by the overload sensor
in the sensor circuit 8. If the duration of the starting current is
longer than that under normal conditions, it is decided that the
apparatus is in an overloaded condition so that the control element
20 is immediately turned off thereby to stop the compressor drive
motor 2.
2. It is only after a predetermined period of time following the
turning off of the control element 20 that the compressor drive
motor 2 is actuated again. When after the lapse of the
predetermined period of time the control element 20 is turned on
and the compressor drive motor 2 is started again, the compressor
drive motor 2 continues to run if it has been started normally. In
the event that the starting current is abnormally long, by
contrast, the control element 20 is turned off again thereby to
stop the compressor drive motor 2, with the result that the
compressor drive motor 2 is prohibited from being started until the
lapse of a predetermined period of time.
3. When, after the control element 20 is turned on, the inner space
of the refrigerator is cooled to a predetermined temperature by the
continuous operation of the compressor drive motor 2, the control
element 20 is turned off and the compressor drive motor 2 is
stopped in response to a signal produced by a temperature sensor in
the sensor circuit 8. It is only after the lapse of a predetermined
period of time following the turning off of the control element 20
that the compressor drive motor 2 is actuated again.
4. The operating time of the compressor drive motor 2, which is
interrupted in accordance with the signal from the temperature
sensor as mentioned in (3) above, is accumulated by the control
circuit 5. When the accumulated time exceeds a predetermined length
of time, say, 24 hours, the defrosting heater 4 is energized by the
control element 40 to remove the frost formed on the cooling
system.
5. Upon completion of the defrosting operation, the defrosting
completion sensor in the sensor circuit 8 turns off the control
element 40 and the defrosting heater 4 is turned off, so that the
defrosting operation is finished and a normal operating condition
is regained. In order to prevent a case in which a failure of the
defrosting completion sensor causes a prolonged energization of the
defrosting heater 4 to overheat the inner space of the
refrigerator, the normal refrigerator operation is regained by the
control element 5, which turns off the defrosting heater 4 after a
predetermined period of time even in the absence of a signal from
the defrosting completion sensor.
By the way, when the defrosting heater 4 is turned off and the
compressor drive motor 2 is turned on, the control element 30 is
turned on thereby to drive the fan motor 3.
It will be noted from the foregoing description that the control
operations require a number of timing signals concerned with:
as to (1), the compressor overload time .tau..sub.OL for protecting
the compressor from an overloaded condition,
as to (2) and (3), the compressor suspension time .tau..sub.OFF
which continues from the stoppage of the compressor to the next
actuation thereof,
as to (4), the accumulated operating time or defrosting suspension
time .tau..sub.H before the starting of a defrosting process,
and
as to (5), a maximum defrosting time .tau..sub.M.
These four types of timing signals are generated by the timer
circuit 50 in the control circuit 5 shown in FIG. 2. In other
words, application of clock pulses from the clock pulse generator
circuit 7 to the timer circuit 50 causes timing signals to be
produced from predetermined stages of the timer circuit 50. These
timing signals combine with signals from the temperature sensor 81,
the overload sensor 82 and the defrosting completion sensor 83 to
control the flip-flops 22, 32 and 42 corresponding to the control
elements 20, 30 and 40 respectively.
Referring to FIG. 3 showing an actual example of the construction
of the control circuit of FIG. 2, R-S flip-flops 22 and 32 and a
trigger flip-flop 42 correspond to the compressor drive motor 2,
fan motor 3 and the defrosting heater 4 of FIG. 1 respectively and
apply outputs to drivers 23, 33 and 43 for driving the control
elements 20, 30 and 40 respectively. Numerals 51, 52 and 53 show
counters each of which comprises multiple stages of
cascade-connected flip-flops, for example, 11, 11 and 4 stages for
the counters 51, 52 and 53 respectively. The clock pulses from the
clock pulse generator circuit 7 are applied first to the first
stage of the counter 51. The counter 51 produces a signal at an
intermediate stage thereof and sends it out to the output line 54.
Also, the counter 51 produces an output at the final stage and
applies it through an output line 55 to the first stage of the
counter 53 and, through the AND gate 71, to the first stage of the
counter 52. The counter 52 sends out outputs to output lines 56 and
57 by way of its intermediate and final stages respectively. The
counter 53 counts output pulses from the counter 51 and produces
its own output by way of the output line 58. A signal from the
reset input line 59 is adapted to be applied to the counter 53 to
clear it. A signal from the temperature sensor 81 is applied
through OR gate 24 to the reset terminal R of the R-S flip-flop 22
and changes to "1" state when the temperature in the refrigerator
reaches a predetermined level, say, -22.degree.C. The signal from
the overload sensor 82 is applied through the AND gate 25 and the
OR gate 24 to the reset terminal R of the R-S flip-flop 22 and
turns to "1" state when an overloaded condition of the compressor
drive motor 2 is detected. The output signal from the defrosting
completion sensor 83 is applied through the OR gate 43 to the reset
terminal of the trigger flip-flop 42 and is changed to "1" state
upon completion of a defrosting operation.
On the other hand, the signal on the output line 54 of the counter
51 is applied to an input terminal of the AND gate 25, while the
output signal on the output line 56 of the counter 52 is applied
through the OR gate 43 to the reset terminal R of the flip-flop 42
of trigger type. The output from the flip-flop 42 on the output
line 57 is applied to the trigger terminal T of the flip-flop 42 of
trigger type. The signal on the output line 58 of the counter 53 is
applied to the set terminal S of the R-S flip-flop 22, while the
signal on the reset input line 59 of the counter 53 is obtained
from the OR gate 24. These signals on the output lines 54, 56, 57
and 58 represent the compressor overload time .tau..sub.OL, miximum
defrosting time .tau..sub.M, defrosting suspension time .tau..sub.H
and compressor suspension time .tau..sub.OFF to be controlled
respectively.
Output signals from the output terminals Q of the R-S flip-flop 22
and the flip-flop 42 of trigger type are applied through the OR
gate 72 to an input terminal of the AND gate 71.
The output signal from the output terminal Q of the flip-flop 42 of
trigger type is applied through the OR gate 24 to the reset
terminal R of the R-S flip-flop 22.
The output signal from the output terminal Q of the R-S flip-flop
22 is applied to the set terminal S of the R-S flip-flop 32, while
the output from output terminal Q of the flip-flop 42 of trigger
type is applied to the reset terminal R of the R-S flip-flop 32, so
that the fan motor 3 shown in FIG. 1 is driven at the time of
starting the compressor and is stopped at the time of starting
defrosting.
The control operation of the circuit shown in FIG. 3 will be
explained in detail below.
First, let us consider a case in which the cooling operation is
initiated by starting the compressor drive motor 2. The temperature
in the refrigerator is higher than a predetermined level of, say,
-22.degree.C, the frost formed remains unremoved and the output
signals of the temperature sensor 81 and the defrosting completion
sensor 83 are in the state of "0."
Therefore, at a given time when a "1" signal is produced on the
output line 58 of the counter 53 and applied to the set terminal of
the R-S flip-flop 22, the flip-flop 22 is set so that the control
element 20 shown in FIG. 1 is turned on through the driver 23 and
signal line 21 thereby to start the compressor drive motor 2. If
the compressor drive motor 2 is normal, a starting current flows
for a short period (5 seconds or less), followed by a constant
operating current, with the result that the compressor drive motor
2 enters a normal operation phase and begins to cool the inner
space of the refrigerator. In the event that the compressor drive
motor 2 is locked for some reasons or other including an overloaded
condition of the compressor drive motor 2, on the other hand, a
starting current several times as large as the operating current
continues to flow. If the overload sensor 82 is arranged to produce
a "1" signal in the presence of current several times as large as
the operating current, it is possible to detect any overloaded
condition from a logical product or the result of application of
the outputs from the overload sensor 82 and the output line 54 of
the counter 51, that is, a signal representing the compressor
overload time .tau..sub.OL.
In other words, even when the output state of the output line 54
changes to "1" after the lapse of several seconds, say, 5 seconds,
the output of the AND gate 25 changes to "1" if the output of the
overload sensor 82 is "1," that is, if the overloaded condition is
sustained, with the result that the R-S flip-flop 22 is reset
thereby to stop the compressor drive motor 2. The compressor drive
motor 2 is not restarted until the R-S flip-flop 22 is set as a
result of change-over of the output line 58 of the counter 53
representing the compressor suspension time .tau..sub.OFF to "1"
state. In view of the fact that an overload time is determined on
the basis of the output from the output line 54 of the counter 51,
the information stored in the counter 51 is required to be zero at
the very instant of starting the motor. If each of the counters 51,
52 and 53 is provided with cascade-connected multiple stages of
flip-flops as shown in FIG. 5 in such a way that the output of a
given flip-flop changes its state at the time of the input fall, a
change in the output state of a stage indicates output fall of all
the preceding stages. In FIG. 5, clock pulses are shown by symbol
CP and outputs of respective stages by A, B and C. For this reason,
the information stored in the counter 51 is zero the very instant
that the compressor drive motor 2 is started as a result of the R-S
flip-flop 22 being set in response to a "1" signal produced on
output line 58 of the counter 53, thus making it possible to
produce a proper timing signal at the output line 54 without any
special operations.
The counter 53 counts the time, say, seven minutes during which the
compressor drive motor 2 remains stationary, that is, the
compressor suspension time .tau..sub.OFF. For this purpose, the
counter 53 is cleared by the reset signal on the reset input signal
line 59 leading to the R-S flip-flop 22.
Limiting the clearing operation to the counter 53 results in a
variation in the compressor suspension time equivalent to the
information stored in the counter 51 at that time, thus affecting
the temperature of the refrigerator inner space. If the compressor
suspension time is lengthened, for example, the refrigerator
temperature rises. However, changes in the temperature of the
refrigerator inner space, which are compensated for in the next
temperature control cycle in accordance with the lengthened or
shortened compressor suspension time, need not be controlled as
strictly as the compressor overload time.
The counter 52 is provided for the purpose of accumulating the
running time of the compressor drive motor 2. To achieve this
purpose, outputs from the output terminals Q of the R-S flip-flop
22 and trigger flip-flop 42 are applied through the OR gate 72 to
an input terminal of the AND gate 71. As a result, when the output
of the trigger flip-flop 42 is "0," that is, when the refrigerator
is not defrosting, output pulses from the counter 51 are counted by
the counter 52, only if the output of the flip-flop 22 is "1," that
is, if the compressor drive motor 2 is running.
When the accumulated running time of the compressor drive motor 2,
that is, the defrosting suspension time .tau..sub.H reaches a
predetermined value, say, 24 hours, the output line 57 of the
counter 52 produces a "1" signal and the trigger flip-flop 42 is
set. The output of the trigger flip-flop 42 resets the R-S
flip-flop 22 and turns on the defrosting heater 4 of FIG. 1 thereby
to start a defrosting operation, while at the same time stopping
the compressor drive motor 2. When the output of the defrosting
completion sensor 83 changes to "1" state, the trigger flip-flop 42
is reset through the OR gate 43 thereby to end the defrosting
operation. The defrosting completion sensor 83 comprises such an
element as a thermistor and depends for its operation on the
measurement of the temperature of the evaporator. In spite of the
"0" state of the output of the R-S flip-flop 22, the counter 52
continues its counting operation even during the defrosting
operation because of the "1" state of the output of the trigger
flip-flop 42.
Therefore, even if the defrosting completion sensor 83 produces no
"1" output after a prolonged period, the lapse of a predetermined
period of time, that is, the maximum defrosting time .tau..sub.M
after the start of defrosting causes the counter 53 to produce a
"1" output at its output line 56, so that the trigger flip-flop 42
is reset through the OR gate 43 thereby to stop the defrosting
operation.
It will be understood from the above explanation that according to
the present invention a plurality of types of timing signals
required are obtained with a minimum number of counters, resulting
in a great advantage for practical applications. The minimum
required number of stages of counters is the one required for
setting the maximum defrosting suspension time (about 24 hours for
the present case, which is the accumulated running time of the
compressor drive motor 2 before starting a defrosting cycle), which
is set by the counters 51 and 52. Since the input to the compressor
suspension time counter 53 is connected to the output of the
counter 51, several stages or actually 3 or 4 stages in addition to
the minimum required number of stages of counters 51 and 52 suffice
for the purpose of the counter 53. Since only the counter 53 is
cleared for the purpose of counting the compressor suspension time
without clearing the counter 51, a small error occurs of the
accumulated running time of the compressor drive motor 2 which is
counted by the counter 52. However, it is as small as about 40
seconds and poses no problem for the proper control of the
refrigerator.
Further, the apparatus according to the invention is so arranged
that a defrosting cycle is started when a predetermined accumulated
running time of the compressor drive motor 2 is reached, thereby
making possible elimination of defrosting waste as well as optimum
defrosting timing.
It will thus be seen that according to the invention the electronic
circuit arrangement of a refrigerator control apparatus requiring a
number of timing signals is most simplified on the one hand and an
optimum defrosting operation is made possible by starting a
defrosting cycle on the basis of the accumulation of the compressor
running time, thereby leading to a great industrial value.
* * * * *