The present disclosure generally relates to a method of determining if water enters a dishwasher. More specifically, the present disclosure relates to an algorithm to prevent seal damage to a wash pump for a dishwasher.
Conventional wash pumps for dishwashers and similar appliances generally require water to be present to lubricate the seals to prevent seal damage from the excessive heat generated by running dry. A dry run could be caused by a variety of scenarios, such as failing to turn on the water to the dishwasher after initial installation or such as a sudden unexpected loss of water pressure. As a result, the motor of the pump and/or the heating element for the dishwasher can overheat and burn out, requiring costly repairs to replace these components. Some conventional dishwashers determine the presence of water in a dishwasher by using a flow meter, pressure sensor, or other device provided specifically for water management. Such additional parts increase the cost of the dishwasher and generally require a flow of water coming into the dishwasher to operate. Accordingly, it can be seen that a need exists for a system and method for detection of water within a dishwasher that addresses the foregoing and other related and unrelated problems in the art.
The invention utilizes an existing part in a novel manner to detect the presence of water. The present invention generally includes a thermistor to detect a water fill. Although thermistors are generally provided in conventional dishwashers, such as to manage heating of water, such conventional thermistors are not used for water management, especially for minimum water level determination. The present algorithm accordingly utilizes a temperature measuring or monitoring device such as a thermistor, for example, to determine whether the proper amount of water has been provided in a dishwasher.
To analyze whether the proper amount of water is present, the algorithm compares a change in temperature, TEMPDELTA with a TEMPMIN
If water is not detected during either the first fill sequence or the drain sequence, the algorithm initiates a retry fill sequence. Prior to the retry fill sequence, the detection parameters generally are first reset, then are monitored during the retry fill sequence. If water is detected during the retry fill sequence, the algorithm proceeds with subsequent motor current tests. If water is not detected during the initial fill sequence, or the drain sequence, or the retry fill sequence, the algorithm proceeds to drain the dishwasher unit and indicates a Fill Error.
Generally, since the temperature expectedly changes upon a successful water detection, the algorithm specified above is used for the first fill sequence, and, if required, during drain/retry fill sequence, of a dishwasher operation cycle.
Those skilled in the art will appreciate the above stated advantages and other advantages and benefits of various additional embodiments upon reading the following detailed description of the embodiments with reference to the below-listed drawing figures.
According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate the embodiments of the disclosure.
The present invention includes an algorithm designed to prevent activation of a dishwasher motor or flow through heater unless a water level sufficient to prevent component damage is present in the dishwasher. The present invention utilizes a thermistor or other temperature detection component to detect a change in the temperature of any water present in the dishwasher. Generally, the algorithm monitors and/or measures a change in temperature to detect/determine whether a fill step has been complete. If sufficient water is determined to have been provided during the fill step, the algorithm proceeds with the dishwasher operation cycle. Otherwise, a drain cycle is initiated, and then a subsequent fill cycle can be initiated. A change in temperature of the water within the dishwasher is monitored through each cycle.
As illustrated in
At least one spray arm 30 typically is mounted within the wash chamber for applying heated water and cleaning solutions of water and soap against the dishes during wash and rinse cycles of the cleaning operation. While only one spray arm 30 is illustrated in
The spray arm 30 generally is connected via a water line or pipe 34 to a wash pump 35, which is part of the sump and motor assembly 29 and can include or can be connected to a motor 36, and a heater 37, such as a flow-through heater or similar heating element. A thermistor 38 or similar temperature sensing device additionally is located along the sump and motor assembly 29 adjacent the wash pump. The wash pump supplies heated water and/or cleaning solution to the spray arm(s) under pressure, generally causing the spray arm to rotate for application of sprays of heated water and/or cleaning and rinse solutions against the dishes during washing and rinsing cycles of the cleaning operation. The thermistor monitors the temperature of water within the sump and provides feedback to a control system for the dishwasher regarding changes in the temperature of the water present in the sump and water assembly, which the fill protection algorithm according to the present invention utilizes to determine the presence of a level of water within the sump and motor assembly sufficient to initiate operation of the wash pump 35 with the danger of overheating or the pump running “dry” being substantially minimized.
The following parameters are measured throughout the first fill sequence:
In general, the fill protection algorithm according the principles of the present invention is based upon a change in temperature of the water within the sump and motor assembly. Generally, as water flows into the sump and motor assembly, there will be a change in temperature due to the incoming water. This change in temperature is indicative of an inflow of water, and if the monitored or detected change in temperature is determined to be at a level at or above the predetermined TEMPMIN
In order to detect whether a sufficient level of water is present in the sump and motor assembly to initiate the dishwasher operational cycle, the fill protection algorithm monitors the change in temperature (TEMPDELTA) between a first measured temperature, which typically can include an initial or minimum temperature (TEMPMIN) and a second measured temperature, generally measured at a desired or selected time during or at/close to the end of the sequence and which can include a maximum measured temperature (TEMPMAX), to determine a change in temperature from the start of the filling operation until the perceived or timed completion of the first fill sequence. This change in temperature (TEMPDELTA) is compared (step 103) with a predetermined minimum temperature change that is selected or predetermined as indicative of there being sufficient water within the system to prevent motor damage from running “dry” (TEMPMIN
As indicated in
If a sufficient level of water is not detected within the sump and motor assembly, the algorithm can initiate a second or retry fill sequence, as indicated at 111 in
Once the dishwasher cycle has been initiated, the wash pump will be started or engaged and will begin to pump water through the dishwasher and to the spray arms for application to the dishes within the dishwasher. As the pump is operated, the motor current for the pump motor further will be monitored to determine the continued presence of a sufficient amount of water within the system to keep the pump operating at a desired or optimum level and without damage to the pump and/or flow-through heater element, based upon the motor current detected over a predetermined window of time of operation. Average motor current will be checked to determine if the motor is in a no-load (absence of water) or loaded condition, as well as to check the difference between maximum and minimum monitored current to determine if the motor of the wash pump is surging. If the motor is found to be loaded and not surging, the dishwasher operation cycle can proceed. If the motor is indicated as in a no-load condition or is surging, the dishwasher control system can stop operation and indicate an error condition.
The foregoing description of the disclosure illustrates and describes various embodiments. As various changes could be made in the above construction without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Furthermore, the scope of the present disclosure covers various modifications, combinations, alterations, etc., of the above-described embodiments that are within the scope of the claims. Additionally, while the disclosure shows and describes only selected embodiments of the present invention, the present invention is further capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, commensurate with the above teachings, and/or within the skill or knowledge of the relevant art. Furthermore, certain features and characteristics of each embodiment of the present invention may be selectively interchanged and applied to other illustrated and non-illustrated embodiments of the invention.
The present patent application is a formalization of previously filed, U.S. Provisional Patent Application Ser. No. 61/345,272, filed May 17, 2010 by the inventor named in the present Application. This patent application claims the benefit of the filing date of this cited Provisional Patent Application according to the statutes and rules governing provisional patent applications, particularly 35 U.S.C. §119(a)(i) and 37 C.F.R. §1.78(a)(4) and (a)(5). The specification and drawings of the Provisional Patent Application referenced above are specifically incorporated herein by reference as if set forth in their entirety.
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