US20130186440A1

US20130186440A1 - Appliance with turbidity sensor assisted time interval determination

Info

Publication number: US20130186440A1
Application number: US13/355,690
Authority: US
Inventors: Joel Charles Boyer; Satish Kumar Raju Buddharaju; Errin Gnadinger; John Dries
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2012-01-23
Filing date: 2012-01-23
Publication date: 2013-07-25

Abstract

The present subject matter provides an appliance with features for determining a time interval for liquid flowing into and/or out of the appliance. For example, a flow of liquid into and/or out of a wash chamber of the appliance is initiated, and a first time is noted. A turbidity sensor is monitored until the sensor detects liquid or air respectively, and a second time is logged. A time interval is calculated based at least in part on the first time and the second time.

Description

FIELD OF THE INVENTION

The present subject matter relates generally to appliances and related methods that use a turbidity sensor to determine a time interval for liquid entering and/or exiting the appliances.

BACKGROUND OF THE INVENTION

With continued pressure on natural resources, appliance manufacturers have focused on efficiency in implementing new designs. Accordingly, appliance manufacturers have scrutinized the amount of electricity, the amount of detergent, and the amount of water used by their appliances because these are all important factors in providing efficient and environmentally sensitive machines. In particular, one approach for improving efficiency involves controlling and/or monitoring the amount of water used in various cycles of the appliances.
In order to accurately determine the amount of liquid (e.g., water) used during various cycles, a dishwasher appliance can rely on a predetermined estimate of the rate at which liquid enters and/or exits the appliance—i.e., the appliance's fluid fill rate and fluid drain rate. The dishwasher appliance can utilize such predetermined fluid fill and drain rates to estimate the amount of liquid in the appliance. For example, the dishwasher may permit liquid to flow into the appliance for a predetermined amount of time in order to fill the appliance with a particular volume of liquid (the time being chosen based upon the predetermined fluid fill and drain rates).
However, variations in consumers' water valves, drain pumps, plumbed inlet flow rate, plumbed inlet pressure, and/or certain geometric constraints can cause significant variation in the actual fill and drain rates between appliances. Thus, the actual fill and drain rates can be significantly different (e.g., greater or less) than the predetermined estimate of the appliance's fill and drain rates. Because the actual fill and drain rates can vary between appliances, the predetermined estimate of the appliance's fill and drain rates are generally very conservative and are often chosen such that the appliance overfills with liquid in order to ensure an adequate amount of liquid is provided to the appliance during operation. Such overfill can result in excessive and unnecessary water usage.
Previously, to avoid relying on predetermined estimated fill and drain rates, a flow meter has been used to measure the actual amount of liquid entering and/or exiting the appliance and, in turn, calculate actual fill and drain rates. However, such flow meters can add to the overall cost of producing the appliance. Also, flow meters can require calibration in order to accurately measure the amount of water entering and/or exiting the appliance. Calibrations can be time consuming and inconvenient. Further, flow meters can malfunction and require repair in order to function properly.
Accordingly, an appliance that determines the amount of liquid in the appliance would be useful. Also, an appliance that determines the amount of liquid in the appliance without relying on predetermined estimated fill and drain rates would be useful. In addition, an appliance that determines the amount of liquid in the appliance without relying on a flow meter would be useful. An appliance that can determine the amount of liquid in the appliance without requiring additional measuring devices would be particularly useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In a first embodiment, a dishwasher appliance is provided with a cabinet that defines a wash chamber. The cabinet includes a sump positioned adjacent a bottom of the cabinet. The sump is configured for collecting liquid in the wash chamber. A rack assembly is slidably received into the wash chamber and configured for receipt of articles for cleaning. A spray arm assembly is also provided for applying the liquid to the articles in the rack assembly. An inlet is also provided that is configured for selectively adding liquid to the wash chamber of the cabinet. A turbidity sensor is disposed within the sump of the cabinet and configured for measuring a turbidity of fluid in the sump. A processing device is in communication with the inlet and the turbidity sensor. The processing device is configured for adjusting the inlet in order to initiate the flow of liquid into the wash chamber of the cabinet, noting a first time, t₁, that corresponds to the step of adjusting, detecting liquid with the turbidity sensor, logging a second time, t₂, that corresponds to the step of detecting, and determining a time interval based at least in part on t₁and t₂.
In a second embodiment, a method for operating an appliance is provided. The method includes initiating a flow of a liquid into a sump of the appliance, noting a first time, t₁, that corresponds to about the step of initiating, detecting the liquid with a turbidity sensor, logging a second time, t₂, that corresponds to about the step of detecting, and determining a time interval based at least in part upon t₁and t₂.
In a third embodiment, a method for operating an appliance is provided. The method includes initiating a flow of a liquid out of a sump of the appliance, noting a first time, t₁, that corresponds to about the step of initiating, detecting air with a turbidity sensor, logging a second time, t₂, that corresponds to about the step of detecting, and determining a time interval based at least in part upon t₁and t₂.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 provides a perspective view of a dishwasher appliance according to an exemplary embodiment of the present subject matter.

FIG. 2 is a side cross-sectional view of the exemplary dishwasher appliance of FIG. 1.

FIG. 3 provides a cross-sectional view of a sump of the exemplary dishwasher appliance of FIG. 2.

FIG. 4 illustrates an exemplary method for operating a dishwasher appliance according to an embodiment of the present subject matter.

FIG. 5 illustrates an additional exemplary method for operating a dishwasher appliance according to an embodiment of the present subject matter.

DETAILED DESCRIPTION OF THE INVENTION

The present subject matter provides an appliance with features for determining a time interval for liquid flowing into and/or out of the appliance. For example, a flow of liquid into and/or out of a wash chamber of the appliance is initiated, and a first time is noted. A turbidity sensor is monitored until the sensor detects liquid or air respectively, and a second time is logged. A time interval is calculated based at least in part on the first time and the second time. Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
FIGS. 1 and 2 depict an exemplary domestic dishwasher appliance 100 that may be configured in accordance with aspects of the present disclosure. For the particular embodiment of FIG. 1, the dishwasher 100 includes a cabinet 102 that extends between a front 114 and a back 116. The cabinet 102 also extends between a top 110 and a bottom 112. The cabinet 102 has a tub 104 therein that defines a wash chamber 106. The tub 104 includes a front opening (not shown) and a door 120 hinged at its bottom 122 for movement between a normally closed, vertical position (shown in FIGS. 1 and 2), wherein the wash chamber 106 is sealed shut for washing operation, and a horizontal, open position for loading and unloading of articles from the dishwasher. Latch 123 is used to lock and unlock door 120 for access to chamber 106. Tub 104 also includes (e.g., defines) a sump 200 positioned adjacent bottom 112 of cabinet 102 and configured for receipt of a liquid (e.g., water, detergent, washing fluid, and/or any other suitable fluid) during operation of appliance 100.
An inlet 160 is positioned adjacent sump 200 of appliance 100. Inlet 160 is configured for directing liquid into sump 200. Inlet 160 may receive liquid from, e.g., a water supply (not shown) or any other suitable source. In alternative embodiments, inlet 160 may be positioned at any suitable location within appliance 100 such that inlet 160 directs liquid into tub 104. Inlet 160 may include a valve (not shown) such that liquid may be selectively directed into tub 104. Thus, for example, during the cycles described below, inlet 160 may selectively direct water and/or washing fluid into sump 200 as required by the current cycle of the appliance 100.
Rack assemblies 130 and 132 are slidably mounted within the wash chamber 106. Each of the rack assemblies 130, 132 is fabricated into lattice structures including a plurality of elongated members 134. Each rack 130, 132 is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outside the wash chamber 106, and a retracted position (shown in FIGS. 1 and 2) in which the rack is located inside the wash chamber 106. A silverware basket (not shown) may be removably attached to rack assembly 132 for placement of silverware, utensils, and the like, that are otherwise too small to be accommodated by the racks 130, 132.
The dishwasher 100 further includes a lower spray-arm assembly 144 that is rotatably mounted within a lower region 146 of the wash chamber 106 and above a tub sump portion 142 so as to rotate in relatively close proximity to rack assembly 132. A mid-level spray-arm assembly 148 is located in an upper region of the wash chamber 106 and may be located in close proximity to upper rack 130. Additionally, an upper spray assembly 150 may be located above the upper rack 130.
The lower and mid-level spray- arm assemblies 144, 148 and the upper spray assembly 150 are fed by a fluid circulation assembly 152 for circulating water and dishwasher fluid in the tub 104. The fluid circulation assembly 152 may include a drain pump 220 located in a machinery compartment 140 located below the bottom sump portion 142 of the tub 104, as generally recognized in the art. Each spray- arm assembly 144, 148 includes an arrangement of discharge ports or orifices for directing washing liquid onto dishes or other articles located in rack assemblies 130 and 132. The arrangement of the discharge ports in spray- arm assemblies 144, 148 provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of the lower spray-arm assembly 144 provides coverage of dishes and other dishwasher contents with a washing spray.
The dishwasher 100 is further equipped with a controller 137 to regulate operation of the dishwasher 100. The controller may include a memory and microprocessor, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor.
The controller 137 may be positioned in a variety of locations throughout dishwasher 100. In the illustrated embodiment, the controller 137 may be located within a control panel area 121 of door 120 as shown. In such an embodiment, input/output (“I/O”) signals may be routed between the control system and various operational components of dishwasher 100 along wiring harnesses that may be routed through the bottom 122 of door 120. Typically, the controller 137 includes a user interface panel 136 through which a user may select various operational features and modes and monitor progress of the dishwasher 100. In one embodiment, the user interface 136 may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface 136 may include input components, such as one or more of a variety of electrical, mechanical or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface 136 may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. The user interface 136 may be in communication with the controller 137 via one or more signal lines or shared communication busses.
It should be appreciated that the subject matter disclosed herein is not limited to any particular style, model, or other configuration of dishwasher, and that the embodiment depicted in FIGS. 1 and 2 is for illustrative purposes only. For example, instead of the racks 130, 132 depicted in FIG. 1, the dishwasher 100 may be of a known configuration that utilizes drawers that pull out from the cabinet and are accessible from the top for loading and unloading of articles. In addition, it should be understood that the subject matter disclosed herein is not limited to dishwasher appliances and may be utilized in, e.g., washing machine appliances.
FIG. 3 provides a cross-sectional view of sump 200 of dishwasher appliance 100. Sump 200 extends between a top 206 and a bottom 208. Sump 200 includes a reservoir 230 configured for receipt of liquid during operation of appliance 100. Drain pump 220 is positioned adjacent bottom 208 of sump 200 and is in fluid communication with reservoir 230 of sump 200. Thus, liquid disposed in sump 200 may be selectively removed (i.e., drained) from sump 200 by drain pump 220.
Sump 200 also includes a turbidity sensor 210. Turbidity sensor 210 is configured for measuring turbidity of a fluid in reservoir 230 of sump 200. For example, turbidity sensor 210 may output a signal (e.g., a voltage or current) to controller 137 corresponding to a turbidity of liquid measured by turbidity sensor 210. Turbidity sensor 210 can also be used to provide an output signal indicative of when sump 200 is empty. More specifically, turbidity sensor 210 can be used to determine when sensor 210 is measuring air as oppose to a liquid. Similarly, turbidity sensor 210 can be used to determine when sensor 210 is measuring both air and a liquid.
A drain level 204 is shown in FIG. 3. Drain level 204 corresponds to a level of liquid that remains in reservoir 230 of sump 200 after activation of drain pump 220. For example, drain pump 220 may not be capable of removing all liquid from reservoir 230 of sump 200. Thus, a volume of liquid that fills sump 200 to drain level 204 represents a carryover volume, V_cthat can remain in sump 200 despite activation of drain pump 220 to remove liquid from reservoir 230. V_cmay be measured in order to accurately determine the amount of liquid remaining in sump 200 after activation of drain pump 220. For example, during design or manufacture of sump 200, V_cmay be measured or calculated.
A fill level 202 is also shown in FIG. 3. Fill level 202 corresponds to a level of liquid used in any particular cycle of appliance 100. As will be understood by those skilled in the art, fill level 202 may vary. For example, the specific fill level 202 for any particular cycle may depend on the current cycle (e.g., wash or rinse) of the appliance 100, the relative dirtiness of articles being washed by appliance 100, and/or the amount of articles being washed by appliance 100. Thus, fill level 202 may be higher than as shown, even extending above sump 200, and is represented in FIG. 3 by way of example only. Accordingly, a volume of liquid that fills sump 200 to fill level 202 represents a prime volume, V_p, of liquid disposed in the appliance 100 during a given cycle of operation of appliance 100. V_pmay be measured in order to accurately determine the amount of liquid in sump 200 during operation of appliance 100. For example, during design or manufacture of sump 200, V_pmay be measured or calculated. Alternatively, V_pmay be calculated based upon a fluid flow rate as described in greater detail below.
As described above, the output of turbidity sensor 210 changes with corresponding changes in the turbidity of fluid being measured by turbidity sensor 210 and with changes between measuring a liquid versus measuring air or a liquid and air. Accordingly, turbidity sensor 210 has a different output depending upon whether it is measuring liquid, air, or a combination of liquid and air. For example, when turbidity sensor 210 is exposed to washing fluid (e.g., water and/or detergent), the output of turbidity sensor 210 is significantly different compared to the output of turbidity sensor 210 when exposed to air or liquid and air as can occur as the liquid level changes.
As may be seen in FIG. 3, turbidity sensor 210 has a detection range 212. Turbidity sensor 210 can only measure turbidity of fluid disposed within the detection range 212. Detection range 212 includes a maximum detection height 214 and a minimum detection height 216. The minimum detection height 216 corresponds to a height below which the turbidity sensor 210 cannot measure the turbidity of fluid. For example, during filling of reservoir 230 with liquid from inlet 160, output of turbidity sensor 210 will change when the liquid reaches the minimum detection height 216 because when liquid passes the minimum detection height 216, turbidity sensor 210 begins to measure the turbidity of the liquid instead of only air.
Accordingly, a volume of liquid that fills the sump 200 to minimum detection height 216 corresponds to a turbidity sensor fill volume, V_tsf, of liquid—i.e. the amount of liquid that must be placed into appliance 100 and/or sump 200 before turbidity sensor 210 detects a change between measuring only air versus measuring both air and liquid. V_tsfmay be measured in order to accurately determine the amount of liquid in sump 200 below minimum detection height 216. For example, during design or manufacture of sump 200, V_tsfmay be measured or calculated. In alternative embodiments, V_tsfmay correspond to any suitable volume that turbidity sensor 210 may reliably detect during filling of sump 200 with liquid, e.g., a volume of liquid that fills reservoir 230 to maximum detection height 214.
The maximum detection height 214 of turbidity sensor 210 corresponds to a height above which the turbidity sensor 210 cannot be used to detect changes in the level of liquid in the appliance 100. However, during draining of sump 200, turbidity sensor 210 may determine when liquid in sump 200 drops below maximum detection height 214. For example, during draining of reservoir 230 from fill level 202, output of turbidity sensor 210 will change when liquid (e.g., washing fluid) passes the maximum detection height 214 and the turbidity sensor 210 is exposed to air and liquid instead of just liquid.
Accordingly, a volume of liquid that fills sump 200 to maximum detection height 214 corresponds to a turbidity sensor drain volume, V_tsd—i.e. the volume of liquid that must remain in sump 200 for turbidity sensor 210 to measure only liquid rather than only air or air and liquid. V_tsdmay be measured in order to accurately determine the amount of liquid in sump 200 at the maximum detection height 214. For example, during design or manufacture of sump 200, V_tsdmay be measured or calculated. In alternative embodiments, V_tsdmay correspond to any suitable volume that turbidity sensor 210 may reliably detect during draining of sump 200, e.g., a volume of liquid that fills reservoir 230 to minimum detection height 214.
FIG. 4 illustrates an exemplary method 400 for operating a dishwasher appliance, e.g., appliance 100. In method 400, a time interval, Δt, is provided. Δt can be used to estimate the amount of liquid (e.g., water) entering appliance 100. Knowledge of the amount of liquid in appliance 100 can permit appliance 100 to operate more efficiently by utilizing an optimum amount of liquid for any particular cycle of the appliance 100. For example, if dishwasher 100 has a small load of articles in wash chamber 106, less water is needed to clean such a load compared to a large load of articles. Thus, appliance 100 can use less water to clean such a load. Method 400 can provide an accurate estimate of the amount of liquid entering appliance 100. Also, method 400 utilizes turbidity sensor 210 to calculate Δt. By utilizing turbidity sensor 210 rather than another additional sensor (e.g., a flow meter), appliance 100 can be more reliable and/or cheaper to produce.
Controller 137 may be programmed to complete or perform the steps of method 400. At 410, a flow of liquid into sump 200 of appliance 100 is initiated. For example, controller 137 may initiate the flow of liquid by adjusting inlet 160. However, initiating the flow of liquid into sump 200 may be accomplished via any suitable method.
At 420, a first time, t₁, is recorded. For example, controller 137 may record t₁when inlet 160 is adjusted at 410 and liquid begins to flow into sump 200. Thus, t₁corresponds to about a time when liquid begins flowing into sump 200.
At 430, output from turbidity sensor 210 is monitored. Based on output of turbidity sensor 210, at 440, it is determined whether turbidity sensor 210 is still detecting only air or is also detecting a liquid. As discussed above, the output of turbidity sensor 210 changes with corresponding changes in the turbidity of fluid being measured by turbidity sensor 210 as well as changes from air to liquid or vice versa. Accordingly, turbidity sensor 210 will have a different output when exposed to liquid from inlet 160 compared to just air. Thus, controller 137 may detect a change in turbidity sensor 210 output as liquid passes the minimum detection line 216 and infer that turbidity sensor 210 is now sensing liquid and air.
At 450, a second time, t₂, is recorded. For example, controller 137 may record t₂when turbidity sensor 210 detects liquid from inlet 160 in step 440. Thus, t₂may correspond to about a time when liquid from inlet 160 fills reservoir 230 of sump 200 to minimum detection height 216, which corresponds to fluid fill volume V_tsf.
At 460, time interval, Δt, is calculated as
Δt _□ =t ₂ −t ₁. (1)
However, alternative formulas may also be used to calculate Δt. Δt is calculated at 460 to provide a measured value for the amount time needed for liquid entering sump 200 via inlet 160 to reach minimum detection level 216. With accurate Δt, appliance 100 may permit a specific amount of liquid to enter into sump 200 through inlet 160.
At 470, Δt is compared to a stored value. Thus, controller 137 may compare Δt to the stored value. At 480, if Δt is significantly different from stored value, controller 137 may replace the stored value with Δt. The stored value may be used, e.g., to estimate the amount of liquid entering sump 200. However, the stored value may be replace with Δt that has been calculated to more accurately reflect time needed for liquid to enter the sump 200 via inlet 160.
In additional embodiments, steps 410-450 may be repeated to generate a plurality of t₁and a plurality of t₂. For example, steps 410-450 may be repeated two, three, four, five, or more times in order to generate a respective number of t₁and t₂. At 460, the plurality of t₁and the plurality of t₂may be used to calculate Δt. By utilizing the plurality of t₁and the plurality of t₂at 460, Δt may be averaged and thus be more accurate.
In alternative embodiments, at 430, rather than detecting liquid from inlet 160 reaching minimum detection height 216, turbidity sensor 210 is calibrated such that liquid filling sump 200 to maximum detection height 214 results in a specific output (e.g., voltage or current) from turbidity sensor 210. Controller 137 may receive such specific output from turbidity sensor 210 and determine that liquid from inlet 160 has filled sump 200 to maximum detection height 214. For example, as detection range 212 is submerged in liquid from inlet 160 and the liquid approaches the maximum detection height 214, output from turbidity sensor 210 may approach the specific output, and controller 137 may infer that turbidity sensor 210 is detecting only liquid and, therefore, liquid has reached maximum detection height 214 and fills volume V_tsf.
In additional alternative embodiments, at 460, rather than Δt, a fluid fill rate, F_fill, is calculated as
$\begin{matrix} ? ? indicates text missing or illegible when filed & (2) \end{matrix}$
where V_tsfis the turbidity sensor fill volume and V_cis the carryover volume. Alternative formulas may also be used to calculate F_fill. F_fillmay be calculated at 460 to provide a measured value for rate at which liquid enters sump 200 via inlet 160. Thus, with accurate F_fill, appliance 100 may permit a specific amount of liquid into sump 200 through inlet 160.
As discussed above, V_Pmay be calculated based upon a fluid flow rate. For example, with F_fillmeasured using the above method 400, F_fillmay be used to calculate V_p. For example, controller 137 may adjust inlet 160 such that liquid is entering sump 200. As will be understood by those skilled in the art, with F_fillknown, controller 137 may permit liquid to enter sump 200 for a specific amount of time such that a particular V_pfills reservoir 230.
FIG. 5 illustrates another exemplary method 500 for operating a dishwasher appliance, e.g., appliance 100. In method 500, an additional time interval, Δt_a, is calculated. Δt_acan be used to estimate the amount of liquid (e.g., water or washing fluid) exiting appliance 100. Knowledge of the amount of liquid exiting appliance 100 can permit appliance 100 to operate more efficiently by utilizing an optimum amount of liquid for any particular cycle of the appliance 100. For example, if dishwasher 100 has a small, relatively clean load of articles in wash chamber 106, washing fluid used to clean such articles may be relatively clean at an end of the wash cycle. Because the washing fluid is relatively clean, the washing fluid can also be used to rinse the articles by adding a small amount of clean water to the washing fluid. Method 500 can be used to estimate the amount of washing fluid exiting appliance 100 prior to adding the clean water for rinsing. Also, method 500 also utilizes turbidity sensor 210 to calculate Δt_a. By utilizing turbidity sensor 210 rather than another additional sensor (e.g., a flow meter), appliance 100 can be more reliable and/or cheaper to produce.
Controller 137 may be programmed to complete or perform the steps of method 500. At 510, a flow of liquid out of sump 200 of appliance 100 is initiated. For example, controller 137 may activate drain pump 220 in order to begin draining reservoir 230 of liquid when liquid fills reservoir 230 to fill level 202. However, initiating the flow of liquid out of sump 200 may also be accomplished via any other suitable method.
At 520, an additional first time, t_1a, is recorded. For example, controller 137 may record t_1awhen drain pump 220 is activated at 510 and liquid begins to flow out of sump 200. Thus, t_1acorresponds to about a time when liquid begins flowing out of sump 200.
At 530, an output from turbidity sensor 210 is monitored. Based on output of turbidity sensor 210, at 540, it is determined whether turbidity sensor 210 is detecting liquid. For example, controller 137 may determine whether turbidity sensor 210 is still sensing only liquid disposed in sump 200 or whether drain pump 220 has removed sufficient liquid from reservoir 230 such that at least part of detection range 212 of turbidity sensor 210 is exposed to air.
As discussed above, the output of turbidity sensor 210 changes with corresponding changes in the turbidity of fluid being measured by turbidity sensor 210 as well as changes from air to liquid or vice versa. Accordingly, turbidity sensor 210 will have a different output when exposed to liquid compared to just air. Thus, controller 137 may detect a change in turbidity sensor 210 output as liquid drains passed the maximum detection height 214 and at least a portion of detection range 212 of turbidity sensor 210 is exposed to air to infer that turbidity sensor 210 is now sensing air and liquid rather than only liquid.
At 550, an additional second time, t_2a, is recorded. For example, controller 137 may record t_2awhen turbidity sensor 210 detects air at 540. Thus, t_2amay correspond to about a time when drain pump 220 has removed liquid from sump 200 such that the level of liquid in the sump 200 passes the maximum detection height 214, which corresponds to fluid drain volume V_tsd.
At 560, an additional time interval, Δt_a, is calculated as
Δt _a□ =t _2a −t _1a. (3)
However, alternative formulas may also be used to calculate Δt_a. Δt_ais calculated at step 560 to provide a measured value for the amount of time necessary for liquid to exit sump 200 via drain pump 220. With accurate Δt_a, appliance 100 may drain a specific amount of liquid from sump 200.
At 570, Δt_ais compared to a stored value. Thus, controller 137 may compare Δt_ato the stored value. At 580, if Δt_ais significantly different from stored value, controller 137 may replace the stored value with Δt_a. The stored value may be used, e.g., to estimate the amount of liquid exiting sump 200. However, the stored value may be replaced with Δt_athat has been calculated to more accurately reflect time needed for liquid to exit sump 200 via drain pump 220.
In additional embodiments, steps 510-550 may be repeated to generate a plurality of t_1aand a plurality of t_2a. For example, steps 510-550 may be repeated two, three, four, five, or more times in order to generate a respective number of t_1aand t_2a. At 560, the plurality of t_1aand the plurality of t_2amay be used to calculate Δt_a. By utilizing the plurality of t_1aand the plurality of t_2aat 560, Δt_amay be averaged and thus be more accurate.
In alternative embodiments, at 530, rather than detecting liquid draining from sump 200 passing maximum detection height 214, turbidity sensor 210 is calibrated such that turbidity sensor 210 sensing only air throughout detection range 212 results in a specific output (e.g., voltage or current) from turbidity sensor 210. Controller 137 may receive such specific output from turbidity sensor 210 and determine that drain pump has drained sump 200 of liquid such that liquid has drained passed the minimum detection height 216. For example, as detection range 212 drains of liquid, output from turbidity sensor 210 may approach the specific output, and controller 137 may infer that turbidity sensor 210 is exposed to only air, and, therefore liquid has drained passed the minimum detection height 216.
In additional alternative embodiments, at 560, rather than Δt_a, a fluid drain rate, F_drain, is calculated as
$\begin{matrix} F_{drain} - \frac{V_{p} - V_{tsf}}{t_{2 c} - t_{1 c}} & (4) \end{matrix}$
where V_tsdis the turbidity sensor drain volume and V_pis the prime volume. Alternative formulas may also be used to calculate F_drain. F_drainmay be calculated at step 560 to provide a measured value for the rate at which drain pump 220 removes liquid from sump 200. With accurate F_drain, appliance 100 may drain a specific amount of liquid from sump 200.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

What is claimed is:

1. A dishwasher appliance comprising:

a cabinet defining a wash chamber, said cabinet including a sump positioned adjacent a bottom of said cabinet, the sump configured for collecting liquid in the wash chamber;

a rack assembly slidably received into the wash chamber and configured for receipt of articles for cleaning;

a spray arm assembly for applying the liquid to the articles in said rack assembly;

an inlet configured for selectively adding liquid to the wash chamber of said cabinet;

a turbidity sensor disposed within the sump of said cabinet and configured for measuring a turbidity of fluid in the sump; and

a processing device in communication with said inlet and said turbidity sensor, wherein said processing device is configured for:

adjusting said inlet in order to initiate the flow of liquid into the wash chamber of said cabinet;

noting a first time, t₁, that corresponds to said step of adjusting;

detecting liquid with said turbidity sensor;

logging a second time, t₂, that corresponds to said step of detecting; and

determining a time interval based at least in part on t₁and t₂.

2. The dishwasher appliance of claim 1, wherein said processing device is further configured for calculating a fluid flow rate based at least in part on t₁and t₂.

3. The dishwasher appliance of claim 2, wherein said processing device is further configured for comparing the fluid flow rate to a stored fluid flow rate.

4. The dishwasher appliance of claim 3, wherein said processing device is further configured for replacing the stored fluid flow rate with the fluid flow rate if the stored fluid flow rate is significantly different from the fluid flow rate.

5. The dishwasher appliance of claim 1, wherein said processing device is further configured for repeating said steps of adjusting, noting, detecting, and logging in order to generate a plurality of t₁and a plurality of t₂, said processing device determining the time interval based at least in part on the plurality t₁and the plurality of t₂.

6. The dishwasher appliance of claim 1, further comprising a drain configured for draining the sump of said cabinet of liquid, wherein said processing device is further configured for:

opening said drain in order to initiate a flow of the liquid out of the sump of said cabinet;

recording an additional first time, t_1a, that corresponds to about said step of opening;

sensing air with said turbidity sensor;

chronicling an additional second time, t_2a, that corresponds to about said step of sensing;

establishing an additional time interval based at least in part on t_1aand t_2a.

7. The dishwasher appliance of claim 6, wherein said processing device is further configured for computing an additional fluid flow rate based at least in part on t_1aand t_2a.

8. The dishwasher appliance of claim 7, wherein said processing device is further configured for comparing the additional fluid flow rate to an additional stored fluid flow rate.

9. The dishwasher appliance of claim 6, wherein said processing device is further configured for repeating said steps of opening, recording, sensing, and chronicling in order to generate a plurality of t_1aand a plurality of t_2a, said processing device determining the additional fluid flow rate based at least in part on the plurality of t_1aand plurality of t_2a.

10. A method for operating an appliance, the method comprising:

initiating a flow of a liquid into a sump of the appliance;

noting a first time, t₁, that corresponds to about said step of initiating;

detecting the liquid with a turbidity sensor;

logging a second time, t₂, that corresponds to about said step of detecting; and

determining a time interval based at least in part upon t₁and t₂.

11. The method of claim 10, further comprising calculating a fluid flow rate of the liquid based at least in part upon t₁and t₂.

12. The method of claim 11, further comprising comparing the fluid flow rate to a prior fluid flow rate.

13. The method of claim 11, further comprising replacing the prior fluid flow rate with the fluid flow rate if the prior fluid flow rate is significantly different from the fluid flow rate.

14. The method of claim 10, further comprising:

repeating said steps of adjusting, noting, detecting, and logging in order to generate a plurality of t₁and a plurality of t₂; and

determining the time interval based at least in part on the plurality of t₁and the plurality of t₂.

15. A method for operating an appliance, the method comprising:

initiating a flow of a liquid out of a sump of the appliance;

noting a first time, t₁, that corresponds to about said step of initiating;

detecting air with a turbidity sensor;

determining a time interval based at least in part upon t₁and t₂.

16. The method of claim 15, further comprising calculating a fluid flow rate of the liquid based at least in part upon t₁and t₂.

17. The method of claim 16, further comprising comparing the fluid flow rate to a prior fluid flow rate.

18. The method of claim 16, further comprising replacing the prior fluid flow rate with the fluid flow rate if the prior fluid flow rate is significantly different from the fluid flow rate.

19. The method of claim 15, further comprising:

repeating said steps of initiating, noting, detecting, and logging in order to generate a plurality of t₁and a plurality of t₂; and