Washing machine with water control and associated method

Abstract

An automatic washing machine with water level control and associated method. In one embodiment, the washing machine comprises a tub for receiving a load of clothes, a water level sensor taking water level measurements during a water fill stage, and a controller. The controller controls a water valve that introduces water into the washing machine. The controller comprises a timer, a memory and a microprocessor. The microprocessor accesses a signature fill rate of the washing machine when unloaded, receives water level measurements from the sensor during the fill stage, and determines a measured fill rate. The microprocessor compares the measured fill rate to the signature fill rate and shut off the water valve when the measured fill rate is substantially equal to the signature fill rate.

Description

FIELD OF THE INVENTION

The present invention relates to a washing machine having a water level control and associated method.

BACKGROUND OF THE INVENTION

Many household appliances, such as, for example, clothes washers and dishwashing machines are equipped with water conservation devices, including water level controls. These devices may require user input in the form of selection of a cycle type, or cycle duration or estimate of water level required based on the load.

Conventional top-load washing machines, for example, include a pressure switch that is either fixed or variable to determine the water level when filling the washing machine. In a variable pressure switch, the user controls and may vary the fill water level by selecting a setting on an associated dial every time the washing machine is used. Often, however, the user guesses incorrectly the appropriate fill level or fails to reset or adjust the water level for each clothes load. This leads to over-consumption of water and inefficient energy use for heating the water.

Federal regulations provide manufacturer incentives, for example in the form of energy credits, to develop more water and energy efficient machines, reducing hot water consumption. Recognizing that reliance on the user to correctly determine and remember to reset the water level switch is not an effective method to conserve energy, regulatory agencies do not give credits toward energy use limits to manufacturers of washing machines that have user-controlled water level features.

Therefore, water-conserving washing machines that do not rely on the user to determine the water fill level are desirable.

SUMMARY OF THE INVENTION

In one embodiment, the invention provides a method for controlling a water fill level of a washing machine. The method comprises loading the washing machine with a wash load, initiating a water fill stage, counting the water fill time, and measuring the water level. A measured fill rate is determined from the measured water level and water fill time, and compared to a signature fill rate, which is characteristic of the washing machine when unloaded. When the measured fill rate is equal to the signature fill rate, the water fill stage is terminated.

Another embodiment of the invention provides a washing machine that comprises a tub for receiving a load of clothes, a water level sensor taking water level measurements during a water fill stage, and a controller. The controller controls a water valve that introduces water into the washing machine. The controller comprises a timer, a memory and a microprocessor. The microprocessor accesses a signature fill rate of the washing machine when unloaded, receives water level measurements from the sensor during the fill stage, and determines a measured fill rate. The microprocessor compares the measured fill rate to the signature fill rate and shut off the water valve when the measured fill rate is substantially equal to the signature fill rate.

Another embodiment of the invention provides a method for controlling a water fill level of a washing machine. The method comprises measuring a fill rate of the washing machine during a water fill stage when the machine contains a wash load in an inner tub. The measured fill rate is compared to a predetermined signature fill rate of the washing machine when unloaded, and the water fill stage is terminated when the measured fill rate is equal to the signature fill rate.

Yet another embodiment provides a method for controlling a water fill level of a washing machine. The method comprises turning on a water valve to start a water fill stage, monitoring a water fill rate during the water fill stage, measuring fluctuations in the water fill rate, determining a steady state fill rate, and turning off the water valve.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.

FIG. 1 is a partially cut-away perspective view of a washing machine according to the present invention;

FIG. 2 is a partial sectional view of the washing machine of FIG. 1;

FIG. 3 is a flow chart of the controller logic according to the present invention;

FIG. 4 is a schematic control diagram according to the present invention; and

FIG. 5 is a representative graph of water level versus fill time.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

FIGS. 1 and 2 illustrate an embodiment of the washing machine 100 according to the invention. The washing machine includes a housing 110, an inner tub 102, and an outer tub 104. The inner 102 tub includes perforations 107 through which water enters the inner tub 102 from the outer tub 104. The inner tub includes an agitator 106 connected to a motor and transmission system 108. A wash load 112 is introduced into the inner tub 102 for washing.

Referring to FIGS. 1 and 4, the washing machine includes a control console 116 with a user-operable control panel 114. The control console 116 houses a controller 118, which includes a microprocessor 120, storage memory 140, and a timer 142. The controller 118 receives a user input 122 through the control panel 114. The user input 122 includes wash cycle selection and wash cycle modifiers, such as wash and/or rinse temperature and clothes type. The controller 118 controls the water valves 124 to turn water flow on and off and to adjust the hot and cold water flow for a user-selected temperature setting.

The controller 118 communicates with a water level sensor 126. The water level sensor 126 may be a continuously variable water level sensor 130, such as a commercially available LL series sensor from Honeywell Sensing and Control, Milpitas, Calif., or any other type of water level sensor, including a commercial radio frequency sensor, a proximity sensor, and the accurate radio frequency sensor disclosed in copending U.S. patent application Ser. No. ______, entitled “Liquid Level Sensor for Appliance and Associated Method”, which is incorporated herein by reference in its entirety. The radio frequency sensor 128 is mounted on the outer tub 104. The water level sensor 126, 128 is programmed to periodically, for example at preset time intervals, or continuously check the water level, and send an analog or digital signal that indicates the water level to the microprocessor 120 of the controller 118.

In operation, the user loads the washing machine 100 with the wash load 112 and initiates a washing cycle using the control panel 114. It is understood that any complete wash cycle includes a water fill stage. The user's input is conveyed from the control panel 114 to the controller 118, which controls the progression of the washing cycle. At the water fill stage, the controller 118 opens the water valves 124 and starts counting fill time as water enters the outer tub 104. The first few seconds of the fill time up to “t₁” correspond to filling the lower portion 132 of the outer tub 104 up to a water level “H₁”, as shown in a representative graph of water level versus fill time in FIG. 5. The initial fill time up to t₁ depends on each machine's geometry and the water pressure, and can be typically about 20-30 seconds. The initial portion of the graph up to time t₁ is substantially linear, and, therefore, the slope of the graph, which represents the fill rate and is equal to tan α₁, is substantially constant. During this part of the fill stage, the controller 118 may calibrate the washing machine 100 to either determine and store in memory 140 the initial fill rate tan α₁, or modify a fill rate tan α₂, which is factory-set. As water starts entering the inner tub 102, water eventually reaches the wash load 112. The wash load 112 gradually absorbs water and possibly reorients itself under the weight of the absorbed water, thus affecting the fill rate and generally interacting with the water level to cause nonlinear fluctuations in the fill rate. The water level versus fill time graph is, therefore, non-linear during this part of the water fill stage, until the wash load 112 is fully submerged in water, at time t₂ corresponding to water level H₂. After time t₂, that is, after full submersion of the wash load 112, the water level versus fill time graph becomes linear again, with slope defined by tan α₂, where α₂, and α₂ are typically equal or have a known relation, which can be used for calibration purposes. The actual values of the slope tan α₁ and tan α₂, are characteristics of the geometry and dimensions of the inner tub 102, the outer tub 104 and other features of the washing machine 100, and provide a signature for the washing machine 100. Each washing machine's signature can be determined by the manufacturer and stored in the microprocessor 120 at the factory. The signature fill rate can also be modified during calibration as described above.

To promote full submersion of the wash load 112 during the water fill stage, the controller 118 periodically actuates the agitator 106 during the fill time between t₁ and t₂. The agitator 106 causes the wash load 112 to be more evenly distributed and uniformly wetted inside the inner tub 102. Thus, sudden discontinuities or spikes in the water level and fill rate are minimized or avoided, increasing the reliability of the water level measurements.

The microprocessor 120 receives the water level data from the water level sensor 126 and determines a measured fill rate, which is represented by tan β at time t₃, where t₃ is a representative measurement time between t₁ and t₂ in the graph of FIG. 5. When the measured fill rate at time t₂ becomes substantially equal to the signature fill rate tan α₂ which is factory preset or modified during calibration from tan α₁, the wash load 112 is fully submerged and the controller 118 shuts off the water valves 124 and terminates the water fill stage.

A flow chart of the water level control is depicted in FIG. 3. The process starts at 150 with user input, the wash cycle progresses to the water fill stage at 152, and the controller 118 turns on the water valves 124 and begins counting time at 154. The sensor 126 measures the water fill level and communicates with the controller 118 at 164. The controller 118 determines the fill rate at 156. The measured fill rate is compared with the signature fill rate tan α₂ at 158. If those two values are not equal, the process continues. If those values are equal, the controller 118 turns off the water valves 124 at 160 and the wash cycle continues. In one embodiment, the controller may perform a calibration at 157 to determine or modify the signature fill rate tan α₂, by determining tan α₁ and using the known relation between α₁ and α₂.

It will be appreciated that the water level versus time graph of FIG. 5 is merely illustrative. The shape and the characteristics of the graph depend on a variety of factors, which may include, in addition to the dimensions and shape of the inner and outer tubs 102, 104, water temperature and water pressure. The water fill rate generally includes an initial stage for the time interval from 0 to t₁ a transient stage between t₁ and t₂, and a steady state beyond t₂. The controller 118 monitors the fill rate until a steady state is reached at t₂, and at that time, it shuts the water valves 124. The onset of the steady state condition can be determined by comparing the measured fill rate to a signature fill rate as discussed above, or by determining that the fill rate ceases to fluctuate and remains substantially constant.

While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible that are within the scope of this invention. Accordingly, the invention is not restricted except in light of the attached claims and their equivalents.

Claims

1. A method for controlling a water fill level of a washing machine, the method comprising: loading the washing machine with a wash load; initiating a water fill stage; counting the water fill time; measuring the water level; determining a measured fill rate from the measured water level and water fill time; comparing the measured fill rate to a signature fill rate characteristic of the washing machine when unloaded; and terminating the water fill stage when the measured fill rate is equal to the signature fill rate.

2. The method of claim 1, wherein measuring the water level includes obtaining water level measurements using a water level sensor.

3. The method of claim 1, further comprising agitating the wash load.

4. The method of claim 1, further comprising presetting the signature fill rate.

5. The method of claim 1, further comprising modifying the signature fill rate by determining a fill rate during an initial portion of the water fill stage.

6. The method of claim 5, wherein determining the fill rate during the initial portion of the water fill stage comprises: counting the water fill time during the initial portion of the water fill stage; and measuring the water level during the initial portion of the water fill stage.

7. The method of claim 1, further comprising calibrating the washing machine by modifying and storing the signature fill rate.

8. The method of claim 4, further comprising calibrating the washing machine by modifying and storing the signature fill rate.

9. An automatic washing machine comprising: a tub for receiving a load of clothes; a water level sensor operable to take water level measurements during a water fill stage; and a controller controlling a water valve that introduces water into the washing machine, the controller comprising a timer, a memory and a microprocessor, wherein the microprocessor accesses a signature fill rate of the washing machine when unloaded, receives the water level measurements from the sensor during the water fill stage, the microprocessor being programmed to determine a measured fill rate, compare the measured fill rate to the signature fill rate and shut off the water valve when the measured fill rate is substantially equal to the signature fill rate.

10. The washing machine of claim 9, wherein the water level sensor is a continuously variable pressure sensor.

11. The washing machine of claim 9, wherein the water level sensor is a proximity sensor.

12. The washing machine of claim 9, wherein the water level sensor is a radio frequency sensor.

13. A method for controlling a water fill level of a washing machine, the method comprising: measuring a fill rate of the washing machine during a water fill stage, the machine containing a wash load in an inner tub; comparing the measured fill rate to a signature fill rate of the washing machine when unloaded; and terminating the water fill stage when the measured fill rate is equal to the signature fill rate.

14. The method of claim 13, further comprising agitating the wash load.

15. The method of claim 13, further comprising: calibrating the washing machine before water reaches the wash load in the inner tub; and modifying the signature fill rate by determining a fill rate during an initial portion of the water fill stage.

16. The method of claim 15, wherein determining the fill rate during the initial portion of the water fill stage comprises: counting the water fill time during the initial portion of the water fill stage; and measuring the water level during the initial portion of the water fill stage.

17. The method of claim 15, further comprising presetting the signature fill rate in the machine.

18. A method for controlling a water fill level of a washing machine having a wash load, the method comprising: turning on a water valve to start a water fill stage; monitoring a water fill rate during the water fill stage; measuring fluctuations in the water fill rate; determining a steady state fill rate; and turning off the water valve.

19. The method of claim 18, wherein determining a steady state fill rate comprises measuring substantial ceasing of fill rate fluctuations.

20. The method of claim 18, wherein determining a steady state fill rate further comprises: comparing the monitored water fill rate to a predetermined fill rate; and determining that the monitored water fill rate is substantially equal to the predetermined fill rate.