Information
-
Patent Grant
-
6694990
-
Patent Number
6,694,990
-
Date Filed
Monday, October 15, 200122 years ago
-
Date Issued
Tuesday, February 24, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Gulakowski; Randy
- Perrin; Joseph L.
Agents
- Rideout, Jr., Esq.; George L.
- Armstrong Teasdale LLP
-
CPC
-
US Classifications
Field of Search
US
- 134 56 D
- 134 57 D
- 134 58 D
- 134 992
- 134 105
- 134 113
-
International Classifications
-
Abstract
An apparatus and method for operating a dishwasher in a variable dry cycle mode is provided. The dishwasher includes a wash chamber, a heater element located within the wash chamber, a rinse aid product dispenser, and a fan unit for circulating air. The method comprises determining a temperature of the wash chamber, determining an amount of rinse aid product in the dispenser, and, based upon the determined temperature and the amount of rinse aid product, determining an optimized heater element cycle and an optimized fan unit cycle.
Description
BACKGROUND OF INVENTION
This invention relates generally to dishwashers, and more particularly, to drying cycles for dishwashers.
Typically, known dishwashers include a cabinet housing a wash chamber wherein dishes, flatware, cups and glasses, etc. are loaded onto roller-equipped racks. Washing fluid is circulated throughout the wash chamber according to a pre-designated wash cycle executable by a control mechanism. Often, the wash cycle concludes with a dry cycle that operates a heating element located within the wash chamber, as well a forced air convection system that circulates ambient air through dishwasher vents to remove humidity from the wash chamber and dry the items located therein. Conventionally, the dry cycle consists of operating the heater element and the circulation fan for a fixed time period and opening the vent for a predetermined time period. See, for example, U.S. Pat. No. 3,908,681.
While in most cases, fixed duration heating cycles may adequately dry items in the dishwasher, certain operating conditions can render the dry cycle inadequate and/or undesirable. For example, water temperature variations in dishwasher rinse cycles, which may occur for various reasons, may lead to incompletely dried items at the end of the cycle or completely dried items well in advance of when the cycle ends. Also, rinse aid products are now available that may affect the amount of time required to dry items in the dishwasher. See, for example, U.S. Pat. No. 6,210,600 B1. Hence, the presence or absence of the rinse aid may result in dry cycles that are excessive or inefficient, respectively.
In light of stringent new energy efficiency requirements and expectations, inefficient dry cycles are undesirable for both manufacturers and consumers alike.
SUMMARY OF INVENTION
In one aspect, a method for controlling a dry cycle for a dishwasher including a wash chamber and a heater element in the wash chamber is provided. The method comprises sensing a temperature of the wash chamber, and energizing the heater element for a time dependent upon the sensed temperature.
In another aspect, a method for operating a dishwasher in a variable dry cycle mode is provided. The dishwasher includes a wash chamber, a heater element located within the wash chamber, a rinse aid product dispenser, and a fan unit for circulating air. The method comprises determining a temperature of the wash chamber, determining an amount of rinse aid product in the dispenser, and, based upon the determined temperature and the amount of rinse aid product, determining an optimized heater element cycle and an optimized fan unit cycle.
In yet another aspect, a method for operating a dishwasher in a variable dry cycle is provided. The dishwasher includes a wash chamber, a heater element in the wash chamber, a rinse aid product dispenser, a fan, and a controller. The method comprises determining operating conditions of the wash chamber and the rinse aid dispenser, and operating the heater element and the fan to execute an energy efficient dry cycle dependent upon the determined conditions of the wash chamber and the rinse aid product dispenser.
In a further aspect, a dishwasher is provided which comprises a wash chamber, a thermistor for determining a temperature of said wash chamber, a heater element located within said wash chamber, and a controller operatively coupled to said heater element and to said thermistor, said controller configured to operate the heater element for a selected time period determined by a thermistor reading.
In still a further aspect, a dishwasher is provided which comprises: a wash chamber, a thermistor for determining a temperature of said wash chamber, a heater element located within said wash chamber, a fan unit, and a controller operatively coupled to said heater element, to said thermistor, and to said fan unit. The controller is configured to execute a variable dry cycle wherein the heater element is energized for a selected time period determined by a thermistor reading and the fan is energized for a selected time period determined by the thermistor reading.
In yet an additional aspect, a dishwasher is provided which comprises a wash chamber, a thermistor for determining a temperature of said wash chamber, a heater element located within said wash chamber, a fan unit, a rinse aid product dispenser, a transducer operatively coupled to said rinse aid product for determining an amount of rinse aid product in the dispenser, and a controller operatively coupled to said heater element, to said thermistor, to said fan unit, and to said transducer. The controller is configured operate an energy efficient dry cycle wherein said fan unit and said heater element are energized for a time determined in response to signals from said thermistor and said transducer.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1
is a side elevational view of an exemplary dishwasher system partially broken away.
FIG. 2
is a schematic block diagram of the dishwasher system shown in FIG.
1
.
FIG. 3
is a flow chart of a variable dry cycle method executable by the system shown in FIG.
2
.
DETAILED DESCRIPTION
FIG. 1
is a side elevational view of an exemplary domestic dishwasher system
100
partially broken away, and in which the present invention may be practiced. It is contemplated, however, that the cycle described herein may be practiced in other types of dishwashers and dishwasher systems beyond dishwasher system
100
described and illustrated herein. Accordingly, the following description of dishwasher
100
is for illustrative purposes only, and the invention is in no way limited to use in a particular type of dishwasher system, for example dishwasher system
100
.
Dishwasher
100
includes a cabinet
102
having a tub
104
therein and forming a wash chamber
106
. Tub
104
includes a front opening (not shown in
FIG. 1
) and a door assembly
120
hinged at its bottom
122
for movement between a normally closed vertical position (shown in
FIG. 1
) wherein wash chamber
106
is sealed shut for washing operation, and a horizontal open position (not shown) for loading and unloading of dishwasher contents. Upper and lower guide rails
124
,
126
are mounted on tub side walls
128
and accommodate upper and lower roller-equipped racks
130
,
132
, respectively. Each of upper and lower racks
130
,
132
is fabricated from known materials into lattice structures including a plurality of elongate members
134
, and each rack
130
,
132
is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outside wash chamber
106
, and a retracted position (shown in
FIG. 1
) in which the rack is located inside wash chamber
106
. Conventionally, a silverware basket (not shown) is removably attached to lower rack
132
for placement of silverware, utensils, and the like that are too small to be accommodated by upper and lower racks
130
,
132
.
A control panel (not shown in
FIG. 1
) is integrated into an escutcheon
136
that is mounted to door assembly
120
, or in further and/or alternative embodiments control selectors, (e.g., buttons, switches or knobs) or control displays, etc. may be mounted at a convenient location on an outer face
138
of door assembly
120
. The control panel and associated selectors and displays are coupled to known control circuitry (not shown) and control mechanisms (not shown in
FIG. 1
) for operating a fluid circulation assembly (not shown in
FIG. 1
) that circulates water and dishwasher fluid in dishwasher tub
104
. The fluid circulation assembly is located in a machinery compartment
140
located below a bottom sump portion
142
of tub
104
.
A lower spray-arm-assembly
144
is rotatably mounted within a lower region
146
of wash chamber
106
and above tub sump portion
142
so as to rotate in relatively close proximity to lower rack
132
. A mid-level spray-arm assembly
148
is located in an upper region of wash chamber
106
and is located in close proximity to upper rack
130
and at a sufficient height above lower rack
132
to accommodate a largest item, such as a dish or platter (not shown), that is expected to be placed in lower rack
132
and washed in dishwasher system
100
. In a further embodiment, an upper spray arm assembly (not shown) is located above upper rack
130
at a sufficient height to accommodate a tallest item expected to be placed in upper rack
130
, such as a glass (not shown) of a selected height.
Lower and mid-level spray-arm assemblies
144
,
148
and the upper spray arm assembly are fed by the fluid circulation assembly, and each spray-arm assembly includes an arrangement of discharge ports or orifices for directing washing liquid onto dishes located in upper and lower racks
130
,
132
, respectively. The arrangement of the discharge ports in at least lower spray-arm assembly
144
provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of lower spray-arm assembly
144
provides coverage of dishes and other dishwasher contents with a washing spray. In various alternative embodiments, mid-level spray arm
148
and/or the upper spray arm are also rotatably mounted and configured to generate a swirling spray pattern above and below upper rack
130
when the fluid circulation assembly is activated and door assembly
120
is properly closed to seal wash chamber
106
for operation.
During operation, and at the conclusion of a wash cycle, a dry cycle mode of operation is typically commenced that energizes a resistive heating element (not shown in
FIG. 1
) to warm the air inside wash chamber
106
and a known fan unit (not shown in
FIG. 1
) for assisted convective airflow in wash chamber
106
to remove humidity from wash chamber
106
and dry washed items located therein. In one embodiment, the fan unit is attached to door assembly
120
and mixes moist air from wash chamber
106
with dry ambient air and forces the mixed air through a vent tube (not shown) in door assembly
120
according to known techniques. Air is discharged from the vent tube at a lower end of door assembly
120
and condensation from the air is collected and returned to dishwasher sump portion
142
. The circulating air has been found to be a considerable aid to drying items in wash chamber
106
in a timely fashion.
In further and/or alternative embodiments, fan units may be employed in addition to, or in lieu of, the above-described fan unit attached to dishwasher door assembly
120
. A variety of forced air circulation fans in different locations in dishwashers are found in the art, and references to fan and fan unit shall refer collectively to any fan element employed to assist in drying items in wash chamber
106
. In other words, the inventive concepts described herein shall apply equally to various types of fan elements operable in a dry cycle mode of operation, rather than referring exclusively to a single fan element in a single location, such as the door mounted fan arrangement described above.
FIG. 2
is a block diagram of a dishwasher control system
150
for use with dishwasher
100
(shown in FIG.
1
). Control system
150
includes a controller
152
which may, for example, be a microcomputer
154
coupled to a dishwasher user interface input
156
. An operator may enter instructions or select desired dishwasher cycles and features via user interface input
156
, and a display
158
coupled to microcomputer
154
displays appropriate messages, indicators, a timer, and other known items of interest to dishwasher users. A memory
160
is also coupled to microcomputer
154
and stores instructions, calibration constants, and other information as required to satisfactorily complete a selected dishwasher cycle. Memory
160
may, for example, be a random access memory (RAM). In alternative embodiments, other forms of memory could be used in conjunction with RAM memory, including but not limited to electronically erasable programmable read only memory (EEPROM).
Power to system
150
is supplied to controller
152
by a power supply
174
configured to be coupled to a power line L. Analog to digital and digital to analog convertors (not shown) are coupled to controller
152
to implement controller inputs and executable instructions to generate controller output to a fluid circulation assembly
162
according to known methods. Fluid circulation assembly
162
includes a water pump, water heater, water filters, etc. to deliver washing fluids and rinses to spray-arm assemblies
144
,
148
(shown in FIG.
1
). In response to manipulation of user interface input
156
, controller
152
monitors various operational factors of the dishwasher, and executes operator selected functions and features according to known methods. Of course, controller
152
may be used to control other dishwasher elements and functions beyond that specifically described herein.
Controller
152
operates the various components of fluid circulation assembly in a designated wash cycle familiar to those in the art, including dispensation of a known rinse aid product from a rinse aid product dispenser
164
in the final stages of the wash cycle. The rinse aid product is a known, commercially available composition, used separately from a detergent composition, to prevent spots and film formation on wash articles.
A transducer
166
is coupled to rinse aid dispenser
164
for signaling controller
152
of operating conditions of rinse aid product dispenser
164
, which is influential on the efficacy of a dishwasher dry cycle. As used herein, transducer
166
is broadly defined as any device or component capable of detecting a presence or amount of rinse aid product in dispenser
164
. For example, in an illustrative embodiment, transducer
166
is a known level switch that is tripped when the rinse aid product falls below a specified level. In alternative embodiments, transducer
166
may comprise a known gauge mechanism, an optical system, or other type of sensor mechanism to determine the presence and/or amount of rinse aid product in dispenser
164
.
A thermistor
168
is also inputted to controller
152
and is used to monitor a temperature of wash chamber
106
(shown in FIG.
1
). As used, herein, thermistor
168
is broadly defined as any temperature sensing element for determining an operating temperature of dishwasher
100
prior to commencement of a dishwasher dry cycle, which also is influential on the efficacy of the dry cycle. In an illustrative embodiment thermistor
168
is a known resistive element with a temperature variant resistance value. In other words, the resistance of the element fluctuates with the temperature of the element according to a known relationship, and by monitoring the voltage across thermistor
168
, the temperature of thermistor
168
may be determined.
In an illustrative embodiment, thermistor
168
is located in dishwasher door assembly
120
(shown in
FIG. 1
) and in fluid communication with wash chamber
106
to monitor temperature conditions. In another embodiment, thermistor
168
is located in wash chamber
106
(shown in
FIG. 1
) itself to monitor operating temperature conditions of dishwasher
100
(shown in
FIG. 1
) in use. Conventionally thermistors are used for a variety of purposes in dishwasher operation, including but not limited to sensing of water temperature conditions to ensure, for example sanitation requirements of the wash cycle, and in a third embodiment, one of these existing thermistors may provide thermistor
168
. For example, the thermistor in different embodiments is thermally coupled with water exiting the water pump to sense the temperature of the water in dishwasher tub
104
(shown in
FIG. 1
) and is located, for example, in a bottom of tub
104
and in fluid communication with the water stream discharged from a water pump inside dishwasher
100
, or mounted to a pipe (not shown) to sense the water temperature before it exits the water pump.
It is contemplated that other temperature sensing components may be used in lieu of temperature sensitive resistive elements in thermistor
168
without departing from the scope of the present invention.
Once appropriately calibrated, signals supplied from rinse aid transducer
166
and thermistor
168
are used by controller
152
to determine an optimized dishwasher dry cycle wherein controller
152
operates a resistive heating element
170
and a vent fan unit
172
for mixing and circulating air to remove humidity from wash chamber
106
in a manner consistent with sensed operating conditions of transducer
166
and thermistor
168
. Thus, items in wash chamber
106
may be appropriately dried in an energy inefficient manner. As will be seen, and unlike conventional dishwasher using fixed time dry cycles, controller
152
operates a dry cycle of a varying length depending on input conditions of the dishwasher through thermistor
168
and transducer
166
.
For example, in an illustrative embodiment, a dry cycle mode is determined by a final rinse water temperature, and whether or not rinse aid product is present in rinse aid dispenser
164
when the dry cycle mode is entered. On-time duration values for heater element
170
and fan
172
are stored in controller memory
160
and indexed by microcomputer
154
according to input condition signals supplied by thermistor
168
and transducer
166
. For example, a portion of an exemplary control scheme is set forth in the following look up table:
TABLE 1
|
|
Final Rinse
Rinse Aid
Heater
Fan
|
Temperature
Present
On-time
On-time
|
|
155° F.
No
12 minutes
24 minutes
|
155° F.
Yes
8 minutes
18 minutes
|
170° F.
Yes
0 minutes
15 minutes
|
|
Thus, for example, if the temperature of wash chamber
106
is determined by controller
152
to be 155° F. as sensed by thermistor
168
, and transducer
166
indicates that rinse aid product is present in dispenser
164
, microcomputer
154
selects a heater time duration value of 8 minutes and a fan time duration value of 18 minutes from controller memory
160
, and heater element
170
and fan
172
are energized accordingly. As the sensed temperature increases prior to energizing heater element
170
and fan
172
, the heater-on time duration value and fan on-time duration value decrease, thereby conserving energy by applying only as much energy as dictated by operating conditions to adequately dry dishes and items therein. Also, time duration values are less when rinse aid product is present than when it is not. Excessive energy consumption of fixed time dry cycles conventionally employed in known dishwashers are therefore substantially eliminated.
Using the methodology set forth above, memory
160
may be located with maps or tables of various operating conditions and specific time duration values corresponding to sensed conditions for selection and execution by controller
152
. Microcomputer
154
, in a further embodiment, may interpolate between values in the look up table to determine appropriate time duration values for heater element
170
and
172
. In yet another embodiment, microcomputer
154
directly calculates, according to derived or empirically determined mathematical relationships, optimal energy efficient heater element and fan on-time duration values for energy efficient operation in a dry cycle mode. In still another embodiment, controller memory
160
is loaded with offset constants to add or subtract to a pre-selected time duration value for heater element
170
and fan
172
, thereby adjusting operation of heater element
170
and fan
172
as conditions dictate.
In a slightly more sophisticated approach, memory
160
is loaded with alternative values such as those set forth below:
TABLE 2
|
|
Final Rinse
Rinse Aid
Heater Element
Fan
|
Temperature
Volume
Pulses
On-time
|
|
|
0° C. to 45° C.
>2 cc
17
30
|
0° C. to 45° C.
<2 cc
20
30
|
45° C. to 55° C.
>2 cc
12
30
|
45° C. to 55° C.
<2 cc
19
20
|
55° C. to 65° C.
>2 cc
6
20
|
55° C. to 65° C.
<2 cc
13
10
|
65° C. to 70° C.
>2 cc
3
10
|
65° C. to 70° C.
<2 cc
10
10
|
>70° C.
>2 cc
0
10
|
>70° C.
<2 cc
7
10
|
|
Thus, under the above control scheme heater element on time (in terms of controller pulses rather than elapsed time) is less when rinse aid volume is above 2 cubic centimeters, and is more when rinse aid volume is less than 2 cubic centimeters at a given temperature. Also, heater element pulses decrease as the sensed temperature increases. Fan on-time is generally independent of rinse aid volume, but decreases as the sensed temperature increases.
Therefore, heater element
170
is operated for a reduced time, thereby producing less heat, as the temperature of wash chamber
106
increases, and is operated for an increased time, thereby generating more heat into wash chamber
106
as the temperature falls. Additionally, heater element
170
is operated for a reduced time at a given temperature when there is more than 2 cubic centimeters of rinse aid product in dispenser
164
, thereby indicating sufficient levels of rinse aid product in the final rinse cycle that accordingly reduces a drying time of items in wash chamber
106
, and heater element
170
is operated for an increased time at the same temperature when less than 2 cubic centimeters of rinse aid product is present in dispenser
164
, thereby indicating insufficient amounts of rinse aid product in the final rinse cycle that accordingly increases a drying time for items in wash chamber
106
. As such, heat is apportioned more commensurate with needs than in conventional systems, and unnecessary heating is generally avoided. Likewise, air circulation is apportioned more commensurate with needs than in conventional systems, and unnecessary air circulation is generally avoided. Thus, controller
152
executes a smart dry cycle taking into account the necessary considerations that govern energy efficiency. As compared to fixed time duration dry cycles executed in known dishwashing systems, control system
150
provides an economical, energy efficient alternative.
It should now be apparent that many variations of look up tables beyond those described may be employed in alternative embodiments while achieving at least some of the advantages of the instant invention and without departing from the scope of the present invention.
FIG. 3
is a flow chart of a method
200
executable by controller
152
(shown in
FIG. 2
) to accomplish the foregoing advantages of an energy efficient variable length dishwasher dry cycle.
Once the activated by a user, such as with user interface input
156
(shown in FIG.
2
), controller
152
begins by inputting
204
a temperature of dishwasher
100
(shown in FIG.
1
). In illustrative embodiments, this may be accomplished by reading
206
a sensed temperature signal indicative of a temperature of wash chamber
106
, or by reading
208
a signal indicative of a water temperature in a final rinse cycle. These signals may be generated by thermistor
168
(shown in
FIG. 2
) for processing by microcomputer
154
(shown in FIG.
2
).
After inputting
204
a temperature signal, controller
152
also inputs
210
a condition of rinse aid product dispenser
164
(shown in FIG.
2
). In illustrative embodiments, this may be accomplished by reading
212
a signal from transducer
166
or microcomputer
154
may calculate or regulate
214
an amount of rinse aid product being used in operation of the dishwasher.
Once dishwasher temperature and rinse aid volume are sensed, calculated or otherwise determined, controller
152
determines
216
a heater on-time duration value and also determines
218
a fan on-time duration value. In accordance with exemplary embodiments, respective time duration values are calculated
220
,
222
by controller
152
or selected
224
,
226
from a look up table, such as those described above. Once the heater element on-time duration value and fan on-time duration value are determined, controller
152
energizes and operates
228
,
230
the respective heater element and fan unit accordingly for a time corresponding to the determined duration values.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
Claims
- 1. A dishwasher comprising:a wash chamber; a thermistor for determining a temperature of said wash chamber; a heater element located within said wash chamber for heating air in said wash chamber, and a controller operatively coupled to said heater element and to said thermistor, said controller configured to operate the heater element for a selected dry cycle time period determined by a thermistor reading of a final rinse water temperature.
- 2. A dishwasher in accordance with claim 1, the controller comprising a processor and a memory, said memory including a plurality of heater element dry cycle operation values for a plurality of thermistor readings.
- 3. A dishwasher in accordance with claim 1 further comprising a rinse aid product dispenser and a transducer operatively coupled to said rinse aid product dispenser.
- 4. A dishwasher in accordance with claim 3, said controller further configured to operate the heater element for a selected dry cycle time period based upon the transducer reading.
- 5. A dishwasher comprising:a wash chamber; a thermistor for determining a temperature of said wash chamber; a heater element located within said wash chamber; a fan unit; and a controller operatively coupled to said heater element, to said thermistor, and to said fan unit, said controller configured to execute a variable dry cycle wherein the heater element is energized for a selected time period determined by a thermistor reading of a final rinse water temperature and the fan is energized for a selected time period determined by the thermistor reading.
- 6. A dishwasher comprising:a wash chamber a thermistor configured to determine a final rinse water temperature; a heater element located within said wash chamber; a fan unit; a rinse aid product dispenser; a transducer operatively coupled to said rinse aid product for determining an amount of a rinse aid product in the dispenser; and a controller operatively coupled to said heater element, to said thermistor, to said fan unit, and to said transducer, said controller configured to execute an energy efficient dry cycle wherein said fan unit and said heater element are energized for a time determined in response to the final rinse water temperature and signals from said transducer.
US Referenced Citations (18)
Foreign Referenced Citations (3)
Number |
Date |
Country |
07100089 |
Apr 1995 |
JP |
08019501 |
Aug 1996 |
JP |
11206688 |
Aug 1999 |
JP |