System and method for controlling the water fill level within a dishwasher appliance

A dishwasher appliance includes a sump, a water supply valve for providing a flow of water into the sump, and a circulation pump that circulates water that is collected in the sump to one or more spray arm assemblies. A pressure sensor is operably coupled to the sump for monitoring sump pressure and wash fluid level. A controller regulates the water supply valve to provide the flow of water into the sump and monitors the sump pressure during the fill process. The controller further determines that the circulation pump is primed when the rate of increase of the sump pressure exceeds the predetermined threshold rate and stops further filling of the sump.

FIELD OF THE INVENTION

The present disclosure relates generally to dishwasher appliances, and more particularly to the use of water level detection systems to optimize fill levels within dishwasher appliances.

BACKGROUND OF THE INVENTION

Dishwasher appliances generally include a tub that defines a wash chamber. Rack assemblies can be mounted within the wash chamber of the tub for receipt of articles for washing. Wash fluid (e.g., various combinations of water and detergent along with optional additives) may be introduced into the tub where it collects in a sump space at the bottom of the wash chamber. During wash and rinse cycles, a circulation pump may be used to circulate wash fluid to spray assemblies within the wash chamber that can apply or direct wash fluid towards articles disposed within the rack assemblies in order to clean such articles. During a drain cycle, a drain pump may periodically discharge soiled wash fluid that collects in the sump space and the process may be repeated.

In general, it is considered desirable for a dishwasher appliance to operate quietly. The noise level generated by the circulation pump is critical to such quiet operation. However, an undesirably high noise level may be generated if air is drawn into the circulation pump and becomes entrained in the circulated liquid, e.g., when a water level in the sump is insufficient to prime the pump. To avoid this operating condition, conventional dishwasher appliances utilize fill algorithms that commonly overfill the sump beyond a prime level. However, it is also considered desirable for a dishwasher appliance to operate efficiently, for example, by using the least amount of water necessary to prime the circulation pump.

Accordingly, a dishwasher appliance having improved features for determining the water level in the sump would be desirable. More specifically, a dishwasher appliance including features and methods for filling the sump with an optimal amount of water would be particularly beneficial.

BRIEF DESCRIPTION OF THE INVENTION

In a first example embodiment, a dishwasher appliance is provided including a sump for collecting water, a circulation pump in fluid communication with the sump for circulating the water to one or more spray arm assemblies, and a water supply valve for selectively providing a flow of water into the sump. A pressure sensor is operably coupled to the sump and a controller is communicatively coupled with the pressure sensor and the circulation pump. The controller is configured for regulating the water supply valve to provide the flow of water into the sump, monitoring a sump pressure using the pressure sensor, determining that the circulation pump is primed if a rate of increase of the sump pressure exceeds a predetermined threshold rate.

In a second example embodiment, a method for determining that a circulation pump of a dishwasher appliance is primed is provided. The dishwasher appliance includes a sump for collecting water, a water supply valve for selectively providing a flow of water into the sump, and a pressure sensor operably coupled to the sump. The method includes regulating the water supply valve to provide the flow of water into the sump, monitoring a sump pressure using the pressure sensor, and determining that the circulation pump is primed if a rate of increase of the sump pressure exceeds a predetermined threshold rate.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “article” may refer to, but need not be limited to dishes, pots, pans, silverware, and other cooking utensils and items that can be cleaned in a dishwashing appliance. The term “wash cycle” is intended to refer to one or more periods of time during which a dishwashing appliance operates while containing the articles to be washed and uses a detergent and water, preferably with agitation, to e.g., remove soil particles including food and other undesirable elements from the articles. The term “rinse cycle” is intended to refer to one or more periods of time during which the dishwashing appliance operates to remove residual soil, detergents, and other undesirable elements that were retained by the articles after completion of the wash cycle. The term “drain cycle” is intended to refer to one or more periods of time during which the dishwashing appliance operates to discharge soiled water from the dishwashing appliance. The term “wash fluid” refers to a liquid used for washing and/or rinsing the articles and is typically made up of water that may include other additives such as detergent or other treatments. Furthermore, as used herein, terms of approximation, such as “approximately,” “substantially,” or “about,” refer to being within a ten percent margin of error.

FIGS. 1 and 2depict an exemplary domestic dishwasher or dishwashing appliance100that may be configured in accordance with aspects of the present disclosure. For the particular embodiment ofFIGS. 1 and 2, the dishwasher100includes a cabinet102(FIG. 2) having a tub104therein that defines a wash chamber106. As shown inFIG. 2, tub104extends between a top107and a bottom108along a vertical direction V, between a pair of side walls110along a lateral direction L, and between a front side111and a rear side112along a transverse direction T. Each of the vertical direction V, lateral direction L, and transverse direction T are mutually perpendicular to one another.

The tub104includes a front opening114and a door116hinged at its bottom for movement between a normally closed vertical position (shown inFIG. 2), wherein the wash chamber106is sealed shut for washing operation, and a horizontal open position for loading and unloading of articles from the dishwasher100. According to exemplary embodiments, dishwasher100further includes a door closure mechanism or assembly118that is used to lock and unlock door116for accessing and sealing wash chamber106.

As best illustrated inFIG. 2, tub side walls110accommodate a plurality of rack assemblies. More specifically, guide rails120may be mounted to side walls110for supporting a lower rack assembly122, a middle rack assembly124, and an upper rack assembly126. As illustrated, upper rack assembly126is positioned at a top portion of wash chamber106above middle rack assembly124, which is positioned above lower rack assembly122along the vertical direction V. Each rack assembly122,124,126is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outside the wash chamber106, and a retracted position (shown inFIGS. 1 and 2) in which the rack is located inside the wash chamber106. This is facilitated, for example, by rollers128mounted onto rack assemblies122,124,126, respectively. Although a guide rails120and rollers128are illustrated herein as facilitating movement of the respective rack assemblies122,124,126, it should be appreciated that any suitable sliding mechanism or member may be used according to alternative embodiments.

Some or all of the rack assemblies122,124,126are fabricated into lattice structures including a plurality of wires or elongated members130(for clarity of illustration, not all elongated members making up rack assemblies122,124,126are shown inFIG. 2). In this regard, rack assemblies122,124,126are generally configured for supporting articles within wash chamber106while allowing a flow of wash fluid to reach and impinge on those articles, e.g., during a cleaning or rinsing cycle. According to another exemplary embodiment, a silverware basket (not shown) may be removably attached to a rack assembly, e.g., lower rack assembly122, for placement of silverware, utensils, and the like, that are otherwise too small to be accommodated by rack122.

Dishwasher100further includes a plurality of spray assemblies for urging a flow of water or wash fluid onto the articles placed within wash chamber106. More specifically, as illustrated inFIG. 2, dishwasher100includes a lower spray arm assembly134disposed in a lower region136of wash chamber106and above a sump138so as to rotate in relatively close proximity to lower rack assembly122. Similarly, a mid-level spray arm assembly140is located in an upper region of wash chamber106and may be located below and in close proximity to middle rack assembly124. In this regard, mid-level spray arm assembly140may generally be configured for urging a flow of wash fluid up through middle rack assembly124and upper rack assembly126. Additionally, an upper spray assembly142may be located above upper rack assembly126along the vertical direction V. In this manner, upper spray assembly142may be configured for urging and/or cascading a flow of wash fluid downward over rack assemblies122,124, and126. As further illustrated inFIG. 2, upper rack assembly126may further define an integral spray manifold144, which is generally configured for urging a flow of wash fluid substantially upward along the vertical direction V through upper rack assembly126.

Dishwasher100may further include a water supply valve146positioned between an external water supply148and a circulation pump (such as pump152described below) to selectively allow water to flow from the external water supply148into circulation pump152. Additionally or alternatively, water supply valve146can be positioned between the external water supply148and sump138to selectively allow water to flow from the external water supply148into sump138. Water supply valve146can be selectively controlled to open and allow the flow of water into dishwasher100and can be selectively controlled to cease the flow of water into dishwasher100.

The various spray assemblies, manifolds, and water supplies described herein may be part of a fluid distribution system or fluid circulation assembly150for circulating water and wash fluid in the tub104. More specifically, fluid circulation assembly150includes a pump152for circulating water and wash fluid (e.g., detergent, water, and/or rinse aid) in the tub104. Pump152may be located within sump138or within a machinery compartment located below sump138of tub104, as generally recognized in the art. Fluid circulation assembly150may include one or more fluid conduits or circulation piping for directing water and/or wash fluid from pump152to the various spray assemblies and manifolds, e.g., during wash and/or rinse cycles. For example, as illustrated inFIG. 2, a primary supply conduit154may extend from pump152, along rear112of tub104along the vertical direction V to supply wash fluid throughout wash chamber106.

As illustrated, primary supply conduit154is used to supply wash fluid to one or more spray assemblies, e.g., to mid-level spray arm assembly140and upper spray assembly142. However, it should be appreciated that according to alternative embodiments, any other suitable plumbing configuration may be used to supply wash fluid throughout the various spray manifolds and assemblies described herein. For example, according to another exemplary embodiment, primary supply conduit154could be used to provide wash fluid to mid-level spray arm assembly140and a dedicated secondary supply conduit (not shown) could be utilized to provide wash fluid to upper spray assembly142. Other plumbing configurations may be used for providing wash fluid to the various spray devices and manifolds at any location within dishwasher appliance100.

Each spray arm assembly134,140,142, integral spray manifold144, or other spray device may include an arrangement of discharge ports or orifices for directing wash fluid received from pump152onto dishes or other articles located in wash chamber106. The arrangement of the discharge ports, also referred to as jets, apertures, or orifices, may provide a rotational force by virtue of wash fluid flowing through the discharge ports. Alternatively, spray arm assemblies134,140,142may be motor-driven, or may operate using any other suitable drive mechanism. Spray manifolds and assemblies may also be stationary. The resultant movement of the spray arm assemblies134,140,142and the spray from fixed manifolds provides coverage of dishes and other dishwasher contents with a washing spray. Other configurations of spray assemblies may be used as well. For example, dishwasher100may have additional spray assemblies for cleaning silverware, for scouring casserole dishes, for spraying pots and pans, for cleaning bottles, etc. One skilled in the art will appreciate that the embodiments discussed herein are used for the purpose of explanation only, and are not limitations of the present subject matter.

In operation, pump152draws wash fluid in from sump138and pumps it to a diverter assembly156, e.g., which is positioned within sump138of dishwasher appliance. Diverter assembly156may include a diverter disk (not shown) disposed within a diverter chamber158for selectively distributing the wash fluid to the spray arm assemblies134,140,142and/or other spray manifolds or devices. For example, the diverter disk may have a plurality of apertures that are configured to align with one or more outlet ports (not shown) at the top of diverter chamber158. In this manner, the diverter disk may be selectively rotated to provide wash fluid to the desired spray device.

According to an exemplary embodiment, diverter assembly156is configured for selectively distributing the flow of wash fluid from pump152to various fluid supply conduits, only some of which are illustrated inFIG. 2for clarity. More specifically, diverter assembly156may include four outlet ports (not shown) for supplying wash fluid to a first conduit for rotating lower spray arm assembly134, a second conduit for rotating mid-level spray arm assembly140, a third conduit for spraying upper spray assembly142, and a fourth conduit for spraying an auxiliary rack such as the silverware rack.

The dishwasher100is further equipped with a controller160to regulate operation of the dishwasher100. The controller160may include one or more memory devices and one or more microprocessors, such as general or special purpose microprocessors 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. Alternatively, controller160may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

The controller160may be positioned in a variety of locations throughout dishwasher100. In the illustrated embodiment, the controller160may be located within a control panel area162of door116as shown inFIGS. 1 and 2. In such an embodiment, input/output (“I/O”) signals may be routed between the control system and various operational components of dishwasher100along wiring harnesses that may be routed through the bottom of door116. Typically, the controller160includes a user interface panel/controls164through which a user may select various operational features and modes and monitor progress of the dishwasher100. In one embodiment, the user interface164may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface164may 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 interface164may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. The user interface164may be in communication with the controller160via one or more signal lines or shared communication busses.

It should be appreciated that the invention is not limited to any particular style, model, or configuration of dishwasher100. The exemplary embodiment depicted inFIGS. 1 and 2is for illustrative purposes only. For example, different locations may be provided for user interface164, different configurations may be provided for rack assemblies122,124,126, different spray arm assemblies134,140,142and spray manifold configurations may be used, and other differences may be applied while remaining within the scope of the present subject matter.

Referring now generally toFIGS. 3 and 4, a water level detection system170according to an exemplary embodiment of the present subject matter will be described. Water level detection system170may generally be configured for continuously or periodically measuring a level of water or wash fluid within dishwasher100. Water level detection system170described herein is only one exemplary configuration used for the purpose of explaining aspects of the present subject matter and is not intended to limit the scope of the invention in any manner.

As illustrated, a water level detection system170includes a pressure sensor172operably coupled to sump138for measuring a pressure of wash fluid174(seeFIG. 4) within sump138to facilitate wash fluid level detection. According to the illustrated embodiment, pressure sensor172is mounted to a receiving boss176defined by sump138. More specifically, receiving boss176may further define an air chamber178that provides a vertical gap between pressure sensor172and the level of wash fluid174within receiving boss176, e.g., to prevent contamination or fouling of pressure sensor172.

In general, pressure sensor172may be any sensor suitable for determining a water level within sump138based on pressure readings. For example, pressure sensor172may be a piezoelectric pressure sensor and thus may include an elastically deformable plate and a piezoresistor mounted on the elastically deformable plate. However, it should be appreciated that according to alternative embodiments, pressure sensor172may be any type of pressure sensor that is fluidly coupled to sump138in any other suitable manner for obtaining sump pressures to facilitate water level detection.

Water level detection system170and pressure sensor172generally operate by measuring a pressure of air within air chamber178and using the measured chamber pressure to estimate the water level in sump138. For example, when the water level within sump138falls below a chamber inlet180, the pressure within air chamber180normalizes to ambient or atmospheric pressure, and thus reads a zero pressure. However, when water is present in sump138and rises above chamber inlet180, the measured air pressure becomes positive and may increase proportionally with the water level. Although sump138is described herein as containing water, it should be appreciated that aspects of the present subject matter may be used for detecting the level of any other suitable wash fluid or liquid in any other appliance.

Now that the construction of dishwasher appliance100and the configuration of controller160according to exemplary embodiments have been presented, an exemplary method200of operating a dishwasher appliance will be described. Although the discussion below refers to the exemplary method200of operating dishwasher appliance100, one skilled in the art will appreciate that the exemplary method200is applicable to the operation of a variety of other dishwasher appliances or other suitable appliances. In exemplary embodiments, the various method steps as disclosed herein may be performed by controller160or a separate, dedicated controller.

Referring now toFIG. 5, method200includes, at step210, regulating a water supply valve to provide a flow of water into a sump of a dishwasher appliance. In this regard, continuing the example from above, at the start of a wash or rinse cycle water supply valve146may be opened to permit a flow of water from water supply148into pump152or directly into sump138. Step220includes monitoring a sump pressure using a pressure sensor operably coupled to sump. In this regard, pressure sensor172of water level detection system170may be used to periodically or continuously monitor sump pressures to facilitate water level detection. For example,FIGS. 6 and 7illustrate sump pressure curves showing the sump pressure over time during exemplary fill processes, as described in more detail below.

According to exemplary embodiments, water supply valve146may remain open and provide a flow of water at a relatively constant flow rate to fill sump138to a desired fill level. As explained above, the desired fill level may typically correspond to the fill level required to prime the pump152, e.g., such that pump152may operate without cavitation or other noisy operation. As explained herein, aspects of the present subject matter are directed to methods of efficiently filling dishwasher appliance100with water or wash fluid174such that pump prime is achieved while overfilling is avoided.

According to exemplary embodiments, controller160may regulate water supply valve146to provide the flow of water into sump138in any particular manner. For example, according to one exemplary embodiment, water supply valve146may be opened to provide the flow of water at a constant flow rate. In addition, or alternatively, the constant flow rate of water may be maintained until the level of wash fluid in sump138reaches a predetermined prefill amount. In this regard, the prefill amount may be below the prime level such that water may be quickly added without concern of overfilling. Water supply valve146may then be regulated to provide the flow of water in a plurality of incremental steps until prime level is reached. For example, the incremental steps may permit sump pressure measurements after each microfill to accurately identify when the prime level is reached and avoid overfilling sump138.

Referring briefly toFIGS. 6 and 7, sump pressure curves are illustrated for two different fill cycles of dishwasher appliance100. Specifically,FIG. 6illustrates a sump pressure curve300including a two-stage fill process that includes both a prefill stage302at a constant flow rate and a subsequent microfill stage304involving a plurality of incremental fills, referred to herein generally have “microfills.” In general, prefill stage302is designed to fill sump138to a level that is below the prime level and the subsequent microfill stage304is designed to carefully approach the prime level using a series of pauses to avoid overfilling sump138. For example, according to an exemplary embodiment, water supply valve146may be regulated during the prefill stage302to provide a flow of water for a predetermined time period or until a predetermined sump pressure or water level is reached. According to an exemplary embodiment, water supply valve146may be regulated during the microfill stage304to provide an incremental volume, such as 0.1 gallons every second or may provide any suitable incremental fill volume at any desirable frequency of time.

By contrast,FIG. 7illustrates a sump pressure curve310for a fill process where water supply valve146is opened and maintained at a relatively constant flow rate for the entire fill process. According to such an embodiment, controller160may continuously monitor sump pressure to facilitate an efficient fill process as described below. Specifically, as described herein, these sump pressure curves may be used to determine an efficient fill level where pump152is primed without overfilling sump138. It should further be appreciated that the fill processes described herein are only exemplary and are not intended to limit the scope of the present subject matter.

Step230includes determining that a circulation pump is primed if a rate of increase of the sump pressure exceeds a predetermined threshold rate. In this regard, without being bound by any particular theory, it is apparent that there is a detectable increase in the slope of the sump pressure curve when the water level sufficient to prime pump152is reached (referred to herein generally as the “prime level”). By detecting this rate increase, controller160may accurately fill to the prime level without overfilling sump138. Thus, step240may include regulating the water supply to stop the flow of water into the sump after determining that the circulation pump is primed. In addition, step250may include operating a circulation pump to circulate water to one or more spray arm assemblies, e.g., to perform a wash or rinse cycle, after the prime fill level is reached. According to exemplary embodiments, this prime level detection algorithm may be implemented prior to operating pump152during every wash cycle or rinse cycle. Alternatively, this process may be used periodically to provide controller160with data sufficient to accurately predict fill levels and compensate for fill variations, such as variations in water valve performance, water supply pressures, etc.

Notably, step230of determining that a circulation pump is primed may utilize any detectable variation in the sump pressure curve which may be indicative of the wash fluid reaching prime level. For example, controller160may obtain a first pressure reading and a second pressure reading a predetermined amount of time after the first pressure reading. Controller160may then determine that the prime level has been reached (e.g., as indicated at point306inFIG. 6) if a difference between the first pressure reading and the second pressure reading (indicated by reference numeral308inFIG. 6) exceeds a predetermined pressure difference.

In this regard, based on the expected increase in pressure for a given microfill volume and a known measurement frequency, controller160may know the wash fluid level based on the pressure difference of sequential pressure readings. For example, continuing example above where 0.1 gallons of water are added every one second, a pressure difference between sequential measurements of greater than 4 mm of water may indicate that prime level has been reached. It should be appreciated that the incremental fill amounts, the incremental fill frequency, and the anticipated pressure difference at prime level may vary while remaining within the scope of the present subject matter.

According to alternative embodiments such as shown inFIG. 7, controller160may monitor sump pressure and generate a sump pressure curve310. In addition, controller160may implement any suitable mathematical method for determining a slope of the sump pressure curve310(such as taking a derivative of the sump pressure curve310). According to such an embodiment, step230of determining that a circulation pump is primed may include determining that the slope of the sump pressure curve310exceeds a predetermined slope.

In this regard, referring for example toFIG. 7, the rate of change of the sump pressure or the sump pressure slope (e.g. as indicated by reference numeral312) exceeds a predetermined slope threshold at prime level314. Thus, by continuously monitoring the slope of the sump pressure curve, and by knowing a slope threshold corresponding to the water level within sump138reaching prime level, controller160may accurately predict when prime level314has been reached. In this manner, an efficient fill volume may be achieved using only a sump pressure sensor without other complex and costly sensors or detection systems.

FIG. 5depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that the steps of any of the methods discussed herein can be adapted, rearranged, expanded, omitted, or modified in various ways without deviating from the scope of the present disclosure. Moreover, although aspects of method200are explained using dishwasher appliance100as an example, it should be appreciated that these methods may be applied to the operation of any suitable dishwasher, washing machine appliance, or other appliance where efficient fill levels are desirable.