Temperature-responsive controller for regulating ice production in a refrigerator unit

An automatic ice maker in an ice making compartment of a refrigerator includes an ice tray placed in the ice making compartment, a temperature sensing element for sensing the temperture of the ice tray, an ice removing driver for driving the ice tray so that ice is removed from it, and a controller for controlling the ice removing driver. The controller initiates one or more timing operations when the temperature sensed by the temperature sensing element falls to or below one of a plurality of set temperatures. When one of these timing operations runs to completion, the system determines that the ice making operation has been completed. The time period corresponding to each set temperature decreases with decreasing set temperatures.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a refrigerator incorporating an automatic ice 
maker. The ice maker includes a temperature sensing element which senses 
the temperature of an ice tray so that completion of an ice making 
operation is detected based on the temperature sensed by the temperature 
sensing element. 
2. Background Information 
In a refrigerator of the type described above, an ice maker according to 
the prior art assumes an ice making step has been completed when the 
temperature sensed by a temperature sensing element falls to a set 
temperature or below. When the ice is made, a drive mechanism is operated 
to remove ice from the ice tray. The automatic ice maker as described 
above is usually provided in an ice making compartment of the 
refrigerator. In this type of ice maker, when refrigerating efficiency is 
high in compartments of the refrigerator, the temperature sensed by the 
temperature sensing element may have fallen to the set temperature even 
when not all of the water in the ice tray has been frozen. To solve this 
problem, the above-mentioned set temperature is usually set at a 
relatively low temperature such as -15.degree. C. so that the complete 
freezing of the water in the ice tray is ensured even when the 
refrigerating efficiency is high, thereby preventing a faulty 
determination of the completion of the ice making step. 
However, when the refrigerating efficiency is lower for some reason (for 
example, because of the increase in the quantity of water to be frozen), 
the temperature sensed by the temperature sensing element does not fall to 
the set temperature even when all of the water in the ice tray is 
completely frozen. Since the ice maker will not sense completion of the 
ice making step in such a case, the ice removing operation cannot be 
performed and accordingly, ice cannot be reserved in an ice reservoir. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a refrigerator 
incorporating an automatic ice maker wherein the completion of ice making 
in the ice tray can be determined with reliability. 
The present invention relies upon the following concept: the water in the 
ice tray will freeze at 0.degree. C. or below even if the refrigerating 
efficiency is low in the compartments of the refrigerator; accordingly, 
when the sensed temperature is at or below this set temperature for a 
certain length of time, but higher than a low set temperature as in the 
prior art, the completion of the ice making can be determined with 
reliability. 
The present invention provides a refrigerator having an ice making 
compartment in which an ice maker is provided, the ice maker having an ice 
tray provided in the ice making compartment for containing an amount of 
water to be made into ice, a temperature sensing element for sensing the 
temperature of the ice tray, and ice removing drive means for driving the 
ice tray so that ice is removed from the ice tray. The invention also 
includes control means for controlling the ice removing drive means, the 
control means performing a timing operation when a temperature sensed by 
the temperature sensing element is at each one of a plurality of set 
temperatures or below, and the control means determining completion of the 
ice making operation based on the elapsing of a time period as measured by 
the timing operation, thereby operating the ice removing drive means. In 
this invention, the period of the timer operation corresponding to each 
set temperature decreases as the set temperature decreases. 
When the refrigerating efficiency is low, the sensed temperature does not 
fall much. The system provides for this behavior by initiating a first 
timing operation when the sensed temperature falls to or below a high set 
temperature. The system determines that the ice making step is completed 
based when the first timing operation runs to completion. In this case the 
completion of the ice making can be determined with reliability when the 
duration of the first timing operation is set to a sufficiently long 
period to allow for the completion of the ice making. 
When the refrigerating efficiency is high, the sensed temperature falls to 
or below a considerably low temperature by the time the ice making is 
completed. The system accounts for this behavior by initiating a second 
timing operation when the sensed temperature falls to or below the low set 
temperature. The system determines that the ice making operation is 
completed based when the second timing operation runs to completion. In 
this case the completion of the ice making operation can be determined 
with reliability and the time of detection of the ice making completion is 
shortened compared to the prior art arrangement. 
In a preferred embodiment, the control means is provided with two set 
temperatures, a first timer timing a long duration for the high set 
temperature condition and a second timer timing a short duration for the 
low set temperature condition. 
Also in a preferred embodiment, a storage compartment is provided over the 
ice making compartment and a water tank is provided in the storage 
compartment so that the water reserved in the water tank is supplied to 
the ice tray by a pump mechanism. In this embodiment, the period required 
for the ice making to be completed can be reduced since the water supplied 
to the ice tray is previously cooled in the storage compartment. 
The control means of the ice maker may be provided with a plurality of set 
temperatures. In this case the completion of the ice making is detected 
immediately when the sensed temperature falls to or below the lowest set 
temperature. The timing operation is initiated when the sensed temperature 
falls to or below the other set temperature or each one of the other set 
temperatures other than the lowest set temperature. The completion of the 
ice making is detected upon the completion of one of these timing 
operations. In this case the completion of the ice making can be 
determined with reliability when the timed periods are set to a value 
sufficiently long to allow for completion of the ice making. 
A method of making ice in a refrigerator comprises steps of supplying water 
to an ice tray provided in an ice making compartment, freezing the water 
in the ice tray by a chilled air supplied into the ice making compartment, 
initiating a timing operation when a sensed temperature of the ice tray 
falls to or below a one of a plurality of set temperatures, detecting 
completion of an ice making step based on the completion of one of these 
timing operations, and operating ice removing drive means so that ice is 
removed from the ice tray. In this invention, the period of the timer 
operation corresponding to each set temperature decreases as the set 
temperature decreases. 
Other objects of the present invention will become obvious upon 
understanding of the illustrative embodiments about to be described or 
will be indicated in the appended claims. Various advantages not referred 
to herein will occur to one skilled in the art upon employment of the 
invention in practice.

DETAILED DESCRIPTION OF THE INVENTION 
A fist embodiment of the present invention will be described with reference 
to FIGS. 1 to 4 of the accompanying drawings. Referring first to FIG. 2, a 
refrigerator cabinet 1 has therein an uppermost storage compartment 2, an 
ice making compartment 3 below the storage compartment 2, a vegetable 
compartment 4 below the ice making compartment 3, and a freezing 
compartment (not shown). Doors 5 to 7, respectively, are provided for 
these compartments. 
An automatic ice maker 8 is provided in the ice making compartment 3. A 
cartridge-type water tank 9 is disposed in the storage compartment 2. 
Water reserved in the water tank 9 is supplied to a water-receiving pan 
10. The water received by the pan 10 is supplied to an ice tray 13 of the 
ice maker 8 through a water supply hose 12 by a pump 11 so that a 
predetermined amount of water is supplied to the ice tray 13. 
In the automatic ice maker 8, the ice tray 13 is inverted and slightly 
twisted by a drive section 15 comprising a motor 14 (see FIG. 3) and 
reduction gear mechanism (not shown) after completion of an ice making 
step so that an ice removing operation is performed. The drive section 15 
serves as ice removing drive means. An ice reserving box 16 is disposed 
below the ice tray 13 in the ice making compartment 3 for receiving ice 
removed from the ice tray 13. A detecting lever 17 is extended from the 
drive section 15 for detecting an amount of ice reserved in the ice 
reserving box 16. A temperature sensing element 18 is mounted on the outer 
bottom of the ice tray 13 for sensing the temperature of the ice tray 13. 
Referring to FIG. 3, a microcomputer-based control circuit 19 as control 
means has an internal memory for storing a program for controlling an 
overall operation of the refrigerator and also has a program for 
controlling the automatic ice maker 8. The temperature sensing element 18 
senses the temperature of the ice tray 13 and generates a signal 
indicative of the temperature of the ice tray 13. The signal is supplied 
to the control circuit 19. The control circuit 19 controls drives the 
motor 14 of the drive section 15 and drives the pump 11 via drive circuits 
20 and 21, respectively. The control circuit 19 in the embodiment includes 
a first built-in timer (not shown) for timing a period which is initiated 
when the sensed temperature falls to or below a first set temperature 
T.sub.1 in FIG. 4. The control circuit 19 also includes a second built-in 
timer (not shown) for timing a period which is initiated when the sensed 
temperature falls to or below a second set temperature T.sub.2. 
In a preferred embodiment of the invention, the first set temperature 
T.sub.1 is set at -8.degree. C. and the second set temperature T.sub.2 at 
-13.5.degree. C., for example, so that the first set temperature T.sub.1 
is higher than the second set temperature T.sub.2. A timing period of the 
first timer is set to several hours (e.g., three hours) and the timing 
period of the second timer is set to a few minutes (e.g., one minute). 
The operation of the invention will now be described. The case where the 
refrigerating efficiency is high will first be described. Referring to 
FIG. 1, the pump 11 is driven so that a predetermined amount of water is 
supplied to the ice tray 13 (step S1). The water in the ice tray 13 is 
cooled by chilled air fed into the ice making compartment 3, causing the 
ice making to progress in the ice tray 13. The sensed temperature from the 
temperature sensing 18 falls as the ice making progresses, as shown in 
FIG. 4. The timing operation of the first timer is initiated when the 
sensed temperature reaches or falls below the first set temperature 
T.sub.1 (steps S2, S6-S8). Since the refrigerating efficiency is high, the 
sensed temperature falls further to the second set temperature before the 
completion of the timing operation of the first timer. When this occurs, 
the timing operation of the second timer is initiated (steps S2, S3). The 
completion of the ice making is determined when the timing operation of 
the second timer is completed several minutes later. When the ice making 
is completed, the ice tray 13 is reversed and twisted by the drive section 
15 so that ice is removed from the ice tray 13 (steps S4, S5). Water is 
supplied to the ice tray 13 again after completion of the ice removing 
operation (step S1), and the above-described ice making is repeated. The 
ice making is repeated until a predetermined amount of ice is reserved in 
the ice reserving box 16. 
In the case where the refrigerating efficiency is lower for some reason 
(for example, because of an increase in the quantity of water to be 
frozen), the sensed temperature does not fall to or below the second set 
temperature T.sub.2 even when all of the water in the ice tray 13 has been 
frozen, as shown in the right-hand portion of the graph of FIG. 4. As 
before, the timing operation of the first timer is initiated when the 
sensed temperature falls to or below the first set temperature T.sub.1 
(steps S2, S6-S8). When the timing operation of the first timer is 
completed several hours later the initiation of the timing operation, the 
completion of the ice making is determined and the ice removing operation 
is performed (steps S9, S5). Subsequently, water is resupplied to the ice 
tray 13 so that the ice making is repeated. 
In accordance with the above-described embodiment, the sensed temperature 
does not fall much when the refrigerating efficiency is low. In this case, 
the first timer initiates a first timing operation when the sensed 
temperature falls to or below the relatively high first set temperature 
T.sub.1. The completion of the ice making is determined when this first 
timed period elapses. Accordingly, the completion of the ice making can be 
determined with reliability when the duration of the first timed period is 
set at to period sufficient for completing the ice making (e.g., several 
hours). This solves the prior art problem that the ice cannot be reserved 
in the ice reserving box 16. Furthermore, when the refrigerating 
efficiency is high, the sensed temperature falls to the relatively low 
second set temperature T.sub.2 by the time the ice making is completed. In 
this case, the second timer initiates a second timing operation when the 
sensed temperature falls to or below the second set temperature. The 
completion of the ice making is determined when this second timed period 
elapses. Accordingly, the ice making can be detected with reliability when 
this second timed period is set at a short period (e.g., a few minutes). 
Consequently, the time when the completion of the ice making is determined 
is shortened compared to the prior art. 
FIGS. 5 and 6 illustrate a second embodiment of the invention. In the 
second embodiment, the completion of the ice making is determined 
immediately when the sensed temperature falls to or below a lowest set 
temperature T.sub.4 (-13.5.degree. C., for example), as shown in FIG. 6. 
In this embodiment, a single timer is provided for initiating a timing 
operation when the sensed temperature is at or below a set temperature 
T.sub.3 (-10.degree. C., for example) other than the lowest set 
temperature T.sub.4. 
In a preferred embodiment, set temperature T.sub.3 is -10.degree. C., set 
temperature T.sub.4 is -13.5.degree. C., and the timing period of the 
timer is set at one hour. 
The operation of the second embodiment of the invention will now be 
described. The case where the refrigerating efficiency is high will be 
described with reference to FIG. 5. The pump 1 is driven so that water is 
supplied to the ice tray 13 (step A1). The water in the ice tray 13 is 
cooled by chilled air fed into the ice making compartment, causing the ice 
making in the ice tray 13 to progress. The sensed temperature from the 
temperature sensing element 18 falls as the ice making progresses, as 
shown in FIG. 6. The timing operation of the timer is initiated when the 
sensed temperature falls to or below the set temperature T.sub.3 (steps 
A2-A5). Since the refrigerating efficiency is high, the sensed temperature 
falls further to reach the lowest set temperature T.sub.4 before the 
completion of the timing operation of the timer. Consequently, the 
completion of the ice making is determined, and the ice removing operation 
is performed (steps A3, A7). The water supply to the ice tray 13 is 
performed again after completion of the ice removing operation (step A1), 
and the above-described ice making is repeated. 
When the refrigerating efficiency is lowered for some reason (for example, 
because of an increase in the amount of water to be frozen), the sensed 
temperature does not fall to or below the lowest set temperature T.sub.4 
even when all of the water in the ice tray 13 has been frozen, as shown in 
the right-hand portion of the graph of FIG. 6. In this case, the timing 
operation of the timer is initiated when the sensed temperature reaches 
the set temperature T.sub.3 (steps A2-A6), and when the timing operation 
of the timer runs to completion (after, for instance, one hour), the 
completion of the ice making is determined and the ice removing operation 
is performed (steps A6, A7). 
Consequently, the same advantages can be achieved in the second embodiment 
as in the first embodiment. 
Although two set temperatures are provided in the foregoing embodiments, 
three or more set temperatures may be provided. 
The foregoing disclosure and drawings are merely illustrative of the 
principles of the present invention and are not to be interpreted in a 
limiting sense. The only limitation is to be determined from the scope of 
the appended claims.