Patent Description:
A conventional dishwasher comprises a tub configured to house items to be washed (such as dishes, cutlery, drinking glasses), and a door for providing selective access to the tub.

A conventional dishwasher also comprises a sump in fluid communication with a bottom portion of the tub, and configured to collect a washing fluid reaching the tub and detergent discharged from a detergent compartment.

A conventional dishwasher further comprises a circulation pump in fluid communication with the sump (and, hence, with the tub), and configured to circulate the washing fluid in the tub. Particularly, when the circulation pump is rotated in a predefined direction, the washing fluid leaves the sump and re-enters the tub (e.g., by means of proper spray devices).

A conventional dishwasher further comprises a circulation pump motor for driving the circulation pump. The circulation pump motor may typically comprise a respective electric motor and a respective motor command element (such as a TRIAC) for commanding the electric motor.

During operation, the circulation pump may experience a saturation state or a starvation state.

When the circulation pump experiences the saturation state, the amount of washing fluid in the tub is sufficient or high enough to prevent air drawing by the circulation pump.

When the circulation pump experiences the starvation state, the amount of washing fluid in the tub is insufficient or not high enough to prevent air drawing by the circulation pump.

<CIT> discloses a method of detecting a change in process water flow of a circulation pump in an appliance for washing and rinsing goods, and an appliance performing the method. An appliance for washing and rinsing goods may be provided including a circulation pump, a sensing arrangement arranged to measure a property indicating torque of the circulation pump, and a controller. The controller may be arranged to average a first set of values of the measured property, thereby creating a first average, average at least a further set of values of the measured property, thereby creating at least one further average, compare the first average with the at least one further average, and to detect change in process water flow of the circulation pump based on a difference between the first average and the at least one further average.

<CIT> discloses adaptive fill control for controlling the amount of liquid added in one or more liquid fill periods in a dishwasher cycle. The amount of liquid added in a liquid fill cycle is adjusted by activating the dishwasher drain pump while continuing to operate the dishwasher circulation pump. The accumulated time from the start of the drain pump operation until the circulation pump experiences a liquid starvation episode is compared to a predetermined optimum time period for the circulation pump to experience liquid starvation. The sign and difference between to accumulated time period and optimum time period is used to adjust the amount liquid added in the next liquid fill period. A number of sensors for detecting a circulation pump liquid starvation episode are disclosed.

<CIT> discloses methods for operating a washer, and in preferred embodiments to a washer having a water tank that is integrally, preferably detachably, formed with the washer, wherein the washer comprises a washing chamber for accommodating goods to be cleaned, said washing chamber having in its lower portion a sump for collecting water during operation of the washer, a water inlet, a circulating pump for circulating water through the washing chamber, and a control unit for controlling a washing cycle carried out by the washer. In accordance with the invention, in this method water is fed via the water inlet into the sump; the pressure within an inlet or outlet conduit of the circulating pump is measured; and based on the pressure measurement the washing cycle is controlled and/or indicator signals are issued to a user of the washer.

The Applicant has found that reliably determining the saturation or starvation state of the circulation pump is of the upmost importance to ensure correct operation of the dishwasher.

The Applicant is aware that by monitoring or measuring one or more electromechanical parameters of the circulation pump motor (such as an electric current drawn by the circulation pump motor, a voltage across the circulation pump motor, and/or a torque of the circulation pump motor), the saturation or the starvation state of the circulation pump could be determined.

Particularly, for each electromechanical parameter monitoring or measuring event, a corresponding air drawing by the circulation pump (starvation event) or a corresponding no-air drawing by the circulation pump (saturation event) may be determined.

However, the Applicant has understood that by merely associating each saturation event with the saturation state (or, equivalently, each starvation event to the starvation state) could be unreliable in practical conditions in which spurious (saturation or starvation) events may often or relatively often arise. Spurious (saturation or starvation) events may for example result from transitory or temporary conditions, such as air bubbles due to turbulent motion of the washing fluid resulting from circulation pump: in these cases, a spurious (saturation or starvation) event would be erroneously interpreted as a (saturation or starvation, respectively) state of the circulation pump.

The Applicant has faced the above-mentioned issues, and has devised a dishwasher capable of reliably determining, based on a trend of the detected (saturation or starvation) events, a saturation state or a starvation state of the circulation pump.

One or more aspects of the present invention are set out in the independent claim claim, with advantageous features of the same invention that are indicated in the dependent claims, whose wording is enclosed herein verbatim by reference.

More specifically, an aspect of the present invention relates to a washing appliance. The washing appliance comprises a tub to house items to be washed. The washing appliance comprises a circulation pump to circulate a washing fluid in the tub. The washing appliance comprises a circulation pump motor to drive the circulation pump. The washing appliance comprises a drain pump. The washing appliance comprises a detection unit configured to monitor at least one electromechanical parameter of the circulation pump motor, and to detect, based on the monitored at least one electromechanical parameter, a starvation event indicating that air is drawn out by the circulation pump or a saturation event indicating that no air is drawn out by the circulation pump. The washing appliance comprises a control unit configured to determine a first starvation event and a second starvation event occurred after said first starvation event. The first starvation event is determined when a starvation event is detected after a first number of consecutive saturation events is counted, or after a first time interval has elapsed during which no starvation event is detected. The second starvation event is determined when a starvation event is detected before a second number of consecutive saturation events is counted after the first starvation event, or before a second time interval has elapsed after the first starvation event during which no starvation event is detected. Said first number of consecutive saturation events is higher than said second number of consecutive saturation events, and said first time interval is higher than said second time interval.

According to an embodiment, after the starvation state is determined, the control unit is configured to determine a saturation state of the circulation pump after a third number of consecutive saturation events is counted from determination of the starvation state, or after a third time interval has elapsed from determination of the starvation state during which no starvation event is detected.

According to an embodiment, said second number of consecutive saturation events is equal to said third number of consecutive saturation events, and said second time interval is equal to said third time interval.

According to an embodiment, with the circulation pump in the saturation state, the control unit is configured to determine a starvation state of the circulation pump if a third starvation event is detected before said first number of consecutive saturation events is counted from determination of the saturation state, or before said first time interval has elapsed from determination of the saturation state, said third starvation event not following the first starvation event.

According to an embodiment, the control unit is configured to pause the operation of the detection unit for a predefined time interval after the first starvation event is determined, and to resume the operation of the detection unit after the predefined time interval has elapsed.

According to an embodiment, said predefined time interval is lower than said first time interval.

According to an embodiment, the first number of consecutive saturation events and the first time interval are indicative of a stable saturation state of the circulation pump.

According to an embodiment, the at least one parameter comprises an electric current of the circulation pump motor.

According to an embodiment, the control unit is configured to control the washing appliance based on the determined starvation state or saturation state of the circulation pump by controlling a washing fluid filling and/or the circulation pump and/or the drain pump.

According to an embodiment, the washing appliance further comprises an inlet valve operable to be selectively switched between an open condition for causing the washing fluid to be loaded into the tub, and a closed condition for preventing the washing fluid be fed to the appliance. The control unit is configured to control a washing fluid filling by controlling a switch of the inlet valve between the open and closed conditions according to the starvation state or saturation state of the circulation pump.

According to an embodiment, the control unit is configured to receive an indication of a current speed of the circulation pump and an indication of a target speed for the circulation pump. Said target speed is based on a user-selected washing cycle and/or on a phase of said user-selected washing cycle. The control unit is configured to control a switch of the inlet valve by:
causing the inlet valve to switch from the open condition to the closed condition if the following two conditions a) and b) are both true:.

According to an embodiment, the control unit is configured to control a switch of the inlet valve further by:
delaying said switch of the inlet valve from the open condition to the closed condition by a delay interval if, in addition to have both the conditions a) and b) that are true, the difference between said target speed and said current speed of the circulation pump is higher than a speed threshold.

According to an embodiment, a duration of said delay interval is based on said difference between said target speed and said current speed of the circulation pump.

According to an embodiment, the control unit is configured to control a washing fluid filling by:
causing the inlet valve to switch from the open condition to the closed condition if, in addition to have the condition a) that is true, the condition b) is not true.

According to an embodiment, the control unit is configured to control a washing fluid filling by:
causing the inlet valve to switch from the open condition to the closed condition if both the conditions a) and b) are not true.

According to an embodiment, the control unit is configured to control a washing fluid filling by:
causing the inlet valve to switch from the closed condition to the open condition if, in addition to have the condition b) that is true, the condition a) is not true.

According to an embodiment, the washing appliance further comprises an inlet valve operable to be selectively switched between an open condition for causing the washing fluid to be loaded into the tub, and a closed condition for preventing the washing fluid be fed to the appliance. The control unit is configured to receive an indication of a current speed of the circulation pump and an indication of a target speed for the circulation pump, and to cause the current speed of the circulation pump to increase towards the target speed. The control unit is configured to control the circulation pump by controlling a speed increase rate of the circulation pump from the current speed towards the target speed according to the starvation state or saturation state of the circulation pump and according to the open and closed condition of the inlet valve.

According to an embodiment, the control unit is configured to cause the current speed of the circulation pump to increase towards the target speed with a first speed increase rate. The control unit is configured to control the speed increase rate of the circulation pump from the current speed towards the target speed by:
causing the current speed of the circulation pump to increase towards the target speed with a second speed increase rate lower than the first speed increase rate, if the following two conditions a) and b) are both true:.

According to an embodiment, the control unit is configured to control the circulation pump by causing the current speed of the circulation pump to be decreased if the condition a) is true while condition b) is not true.

According to an embodiment, the control unit is configured to control the circulation pump by causing the current speed of the circulation pump to increase towards the target speed with the second speed increase rate if, in addition to have both the conditions a) and b) that are true, no saturation state of the circulation pump is determined during a predetermined time period after the determination of a starvation state of the circulation pump.

According to an embodiment, the control unit is configured to cause the current speed of the circulation pump to increase towards the target speed with a third speed increase rate lower than the first speed increase rate and higher than the second speed increase rate if the circulation pump has reached the target speed before a starvation state of the circulation pump is determined.

According to an embodiment, the control unit is configured to cause the current speed of the circulation pump to increase towards the target speed with the third speed increase rate if, in addition to have the condition a) true, a saturation state of the circulation pump is determined during said predetermined time period.

According to an embodiment, said third speed increase rate is equal to:.

According to an embodiment, said first value of the third speed increase rate is higher than <NUM> RPM/s, and said second value of the third speed increase rate is lower than <NUM> RPM/s.

According to an embodiment, said target speed depends on a user-selected washing cycle being carried out by the washing appliance and/or by a phase of said user-selected washing cycle being carried out by the washing appliance.

According to an embodiment, said first speed increase rate is higher than <NUM> RPM/s, and said second speed increase rate is lower than <NUM> RPM/s.

According to an embodiment, the control unit is configured to control the washing fluid filling and the circulation pump by controlling at least one washing filling component allowing the washing fluid filling and at least one pump parameter of the circulation pump based on the starvation state or saturation state of the circulation pump, and by controlling the at least one washing filling component and the at least one pump parameter with respect to each other.

According to an embodiment, the at least one washing filling component comprises an inlet valve operable to be selectively switched between an open condition for causing the washing fluid to be loaded into the tub and a closed condition for preventing the washing fluid be fed to the appliance. The at least one pump parameter comprises a target speed of the circulation pump based on a user-selected washing cycle and/or on a phase thereof and a current speed of the circulation pump. The control unit is configured to control the washing fluid filling and the circulation pump by:.

These and other features and advantages of the present invention will be made apparent by the following description of some exemplary and non-limitative embodiments thereof; for its better intelligibility, the following description should be read making reference to the attached drawings, wherein:.

With reference to the drawings, <FIG> schematically shows a simplified (not-in-scale) cross-sectional side view of a washing appliance, such as a dishwasher, <NUM> according to an embodiment of the present invention.

In the following, only features of the dishwasher <NUM> that are deemed relevant for the understanding of the present invention will be discussed, with well-known features and/or obvious variants of the relevant features that are omitted for the sake of conciseness.

According to an embodiment, the dishwasher <NUM> comprises a control unit <NUM> (or more thereof) configured to control an operation of the dishwasher <NUM>.

According to an embodiment, the control unit <NUM> is configured to control the operation of the dishwasher <NUM> by carrying out one or more software/firmware routines (discussed in the following) installed/stored in one or more memory units of (or associated with) the control unit <NUM>.

According to an embodiment, the dishwasher <NUM> comprises a number of well-known hydraulic, electronic, electric and/or electromechanical components (hereinafter globally referred to as dishwasher components).

According to an embodiment, the control unit <NUM> is configured to control an operation of the dishwasher components (or at least of a subset thereof).

According to an embodiment, the control unit <NUM> is configured to control the operation of the dishwasher components by running a respective routine (discussed in the following), or more thereof.

According to an embodiment, the dishwasher <NUM> comprises a tub <NUM>. According to an embodiment, the tub <NUM> is configured to house items to be washed, such as dishes, cutlery, drinking glasses.

According to an embodiment, the dishwasher <NUM> comprises one or more baskets for accommodating the items to be washed. According to an embodiment, each basket is provided in the tub <NUM>. According to an embodiment, each basket (or at least a subset of the baskets) is at least partially removably provided in the tub <NUM>.

According to an embodiment, the dishwasher <NUM> comprises a first basket (or upper basket) <NUM>, a second basket (or middle basket) <NUM> and a third basket (or lower basket) <NUM>. Just as an example, the upper basket <NUM> may be configured to accommodate cutlery, and the middle <NUM> and lower <NUM> baskets may be configured to accommodate other kinds of items to be washed, such as plates and drinking glasses.

According to an embodiment, the dishwasher <NUM> comprises a door (not shown in the figure). According to an embodiment, the door is hingedly mounted to a front portion of the dishwasher <NUM> for providing selective access to the tub <NUM>, and hence to the baskets <NUM>, <NUM>, <NUM>.

According to an embodiment, the dishwasher <NUM> comprises a detergent compartment (not shown) for storing detergent. Without losing generality, the detergent compartment may be configured to store detergent in form of tablets, liquid, and/or powder. According to an embodiment, the detergent compartment is located at an inside portion of the door of the dishwasher <NUM>. According to an embodiment, during operation of the dishwasher <NUM>, the stored detergent may be controllably discharged, e.g. under the control of the control unit <NUM>, into the tub <NUM> according to a user-selected washing cycle and/or to a phase thereof.

According to an embodiment, the dishwasher <NUM> comprises an inlet valve <NUM> operable (e.g., under the control of the control unit <NUM>) to be selectively switched between an open condition for causing washing fluid (e.g., fresh water provided by a water inlet <NUM>) to be fed to the dishwasher <NUM> and loaded into the tub <NUM>, and a closed condition for preventing the washing fluid be fed to the dishwasher <NUM>.

According to an embodiment, the dishwasher <NUM> comprises a sump <NUM>. According to an embodiment, the sump <NUM> is in fluid communication with a bottom portion of the tub <NUM>. According to an embodiment, the sump <NUM> is configured to collect the washing fluid reaching the tub <NUM> (such as fresh water loaded by the inlet valve <NUM>). According to an embodiment, the sump <NUM> is configured to collect the detergent discharged from the detergent compartment. According to an embodiment, the fresh water (from the tub <NUM>) and the detergent from the detergent compartment mix with each other within the sump <NUM>, so that the resulting washing fluid - also referred to as process water - turns into a mixture of water and detergent.

According to an embodiment, the dishwasher <NUM> comprises a circulation pump <NUM>. According to an embodiment, the circulation pump <NUM> is in fluid communication with the sump <NUM> (and, hence, with the tub <NUM>). According to an embodiment, the circulation pump <NUM> is configured to be rotated, e.g. under the control of the control unit <NUM>, in a first (or forward) direction and in a second (or backward) direction. According to an embodiment, the circulation pump <NUM> is configured to circulate the washing fluid in the tub <NUM> during a user-selected washing cycle and/or a phase thereof. According to an embodiment, the circulation pump <NUM> is configured to circulate the washing fluid in the tub <NUM> when the circulation pump <NUM> is rotated in the forward direction.

According to an embodiment, when the circulation pump <NUM> is rotated in the forward direction, the washing fluid leaves the sump <NUM> and re-enters the tub <NUM> (e.g., from above). According to an embodiment, when the circulation pump <NUM> is rotated in the forward direction, the washing fluid is caused to leave the sump <NUM>, to pass through one or more conducts and to be sprayed back into the tub <NUM> by spray devices. According to an embodiment, each spray device is associated with a respective basket. In the exemplary considered embodiment in which the dishwasher <NUM> comprises three baskets, the dishwasher <NUM> comprises three spray devices. In the exemplary considered embodiment, the dishwasher <NUM> comprises three spray devices <NUM>, <NUM>, <NUM> each one associated with a respective basket <NUM>, <NUM>, <NUM>.

According to an embodiment, each spray device <NUM>, <NUM>, <NUM> comprises a respective wash arm. According to an embodiment, each wash arm is provided with one or more nozzles for causing the washing fluid to be sprayed onto the items to be washed that are housed in the respective basket <NUM>, <NUM>, <NUM>.

According to an embodiment, the dishwasher <NUM> comprises a flow control device <NUM> configured to receive the washing fluid pumped by the circulation pump <NUM> when the latter is controlled to rotate in the forward direction, and to selectively provide (e.g., under the control of the control unit <NUM>) the received washing fluid to one or more selected spray devices among the spray devices <NUM>, <NUM>, <NUM>. In this way, the washing fluid pumped by the circulation pump <NUM> may be selectively recirculated in the washing tub <NUM> through the selected spray device(s). According to an embodiment, selective provision of the received washing fluid to the selected spray device(s) may be achieved by selective connection between (i.e., by fluidly connecting in a selective manner) the selected spray device and the circulation pump <NUM> (e.g., an output thereof).

According to an embodiment, the dishwasher <NUM> comprises a filter <NUM>. According to an embodiment, the filter <NUM> is configured to filter soil from the washing fluid before the latter is recirculated into the washing tub <NUM> by the circulation pump <NUM> through the selected spray device(s). According to an embodiment, the filter <NUM> is provided at the sump <NUM>.

According to an embodiment, the dishwasher <NUM> comprises a drain pump <NUM>. According to an embodiment, the drain pump <NUM> is configured to be operated (e.g., by, or under the control of, the control unit <NUM>) in an activated condition which causes the washing fluid within the sump <NUM> to be drained from the dishwasher <NUM> (e.g., through a corresponding drain outlet <NUM>) and in a deactivated condition which prevents the washing fluid within the sump <NUM> to be drained from the dishwasher <NUM>.

According to an embodiment (as illustrated in <FIG>), the dishwasher <NUM> comprises a circulation pump motor <NUM> for driving the circulation pump <NUM>. According to an embodiment, the circulation pump motor <NUM> comprises a respective electric motor and a respective motor command element (such as a TRIAC) for commanding the electric motor. According to an embodiment, the circulation pump motor <NUM> is operated by, or under the control of, the control unit <NUM>.

According to an embodiment (as illustrated in <FIG>), the dishwasher <NUM> comprises a drain pump motor <NUM> for driving the drain pump <NUM>. According to an embodiment, the drain pump motor <NUM> comprises a respective electric motor and a respective motor command element (such as a TRIAC) for commanding the respective electric motor. According to an embodiment, the drain pump motor <NUM> is operated by, or under the control of, the control unit <NUM>.

Provision of the circulation pump motor <NUM> and of the drain pump motor <NUM> allows concurrent and independent driving (or, more generally, concurrent and independent actuation or control) of the circulation pump <NUM> and of the drain pump <NUM>. However, embodiments are not excluded in which a single motor system configured to selectively drive the circulation pump <NUM> or the drain pump <NUM> is provided: in these embodiments, concurrent and independent actuation or control of the circulation <NUM> and drain <NUM> pumps may not take place (i.e., concurrent and independent actuation or control of the circulation <NUM> and drain <NUM> pumps may be excluded).

According to an embodiment, the dishwasher <NUM> comprises a water softening system <NUM>.

According to an embodiment, the water softening system <NUM> is connected between the water inlet <NUM> and the inlet valve <NUM>.

According to an embodiment, the water softening system <NUM> is configured to reduce hardness of water fed to the dishwasher <NUM> through the water inlet <NUM> (and used for generating the washing fluid). Without losing generality, the water softening system <NUM> may comprise a softening agent container adapted to contain a water softening agent (e.g., an ion-exchange resin) capable of reducing hardness of water, and a regenerating agent container for storing a regenerating agent, usually salt (e.g., sodium chloride salt) configured to regenerate the softening agent when exhausted.

According to an embodiment, the dishwasher <NUM> comprises a detection unit <NUM> (or more thereof).

According to an embodiment, the detection unit <NUM> is configured to monitor or measure one or more electromechanical parameters of the circulation pump motor <NUM>. Examples of electromechanical parameters of the circulation pump motor <NUM> include, but are not limited to, an electric current drawn by the circulation pump motor <NUM>, a voltage across the circulation pump motor <NUM>, and/or a torque of the circulation pump motor <NUM>.

According to an embodiment, the detection unit <NUM> is configured to detect, based on the monitored electromechanical parameter(s), a starvation event or a saturation event.

For the purposes of the present disclosure, a starvation event indicates that air is drawn out by the circulation pump <NUM>, and a saturation event indicates that no air is drawn out by the circulation pump <NUM>. Just as an example, a starvation event may be determined when a current value of the electric current drawn by the circulation pump motor <NUM> is subjected to a variation (for example, a drop) (e.g., at least equal to a predetermined amount).

According to an embodiment, the detection unit <NUM> is configured to provide each detected (saturation or starvation) event to the control unit <NUM>.

According to an embodiment, as better discussed in the following, the control unit <NUM> is configured to determine, based on a trend of the detected (saturation or starvation) events received by the detection unit <NUM>, a saturation state or a starvation state of the circulation pump <NUM>. According to an embodiment, the control unit <NUM> is configured to determine a saturation state or a starvation state of the circulation pump <NUM> by running a respective routine (discussed in the following), or more thereof.

For the purposes of the present disclosure, a saturation state of the circulation pump <NUM> indicates that sufficient washing fluid is present in the tub <NUM> to prevent air from being drawn out by the circulation pump <NUM>. In other words, a saturation state of the circulation pump <NUM> indicates that the amount of washing fluid in the tub <NUM> is sufficient or high enough to prevent air from being drawn out by the circulation pump <NUM>. An exemplary saturation state of the circulation pump <NUM> is schematically illustrated in <FIG>.

For the purposes of the present disclosure, a starvation state of the circulation pump <NUM> indicates that insufficient washing fluid is present in the tub <NUM> to prevent air from being drawn out by the circulation pump <NUM>. In other words, a starvation state of the circulation pump <NUM> indicates that the amount of washing fluid in the tub <NUM> is insufficient or not sufficient or not high enough to prevent air from being drawn out by the circulation pump <NUM>. An exemplary starvation state of the circulation pump <NUM> is schematically illustrated in <FIG>.

As better understood from the following discussion, determining the (saturation or starvation) state of the circulation pump <NUM> based on a trend of the detected (saturation or starvation) events, rather than merely associating each (saturation or starvation) event with the corresponding (saturation or starvation, respectively) state of the circulation pump <NUM>, allows avoiding that a spurious (saturation or starvation) event resulting from transitory or temporary conditions (such as, for example, air bubbles due to turbulent motion of the washing fluid resulting from circulation pump and/or drain pump operation) is erroneously interpreted as, i.e. it is associated with, a (starvation or saturation, respectively) state of the circulation pump <NUM>.

According to an embodiment, the control unit <NUM> is configured to control the dishwasher <NUM> based on the determined (starvation or saturation) state of the circulation pump <NUM>. According to an embodiment, the control unit <NUM> is configured to control a washing fluid filling and/or the circulation pump <NUM> and/or the drain pump <NUM> based on the determined (starvation or saturation) state of the circulation pump <NUM>. According to an embodiment, the control unit <NUM> is configured to control the washing fluid filling and/or the circulation pump <NUM> and/or the drain pump <NUM> by running one or more respective routines (as better discussed in the following).

With reference to <FIG>, it illustrates in terms of functional blocks exemplary routines that can be run by the control unit <NUM>, according to an embodiment of the present invention. As will be understood form the following description, one or more routines may be run by the control unit <NUM> concurrently with, and/or in alternative to, and/or by interacting / cooperating with, one or more other routines.

As mentioned above, according to an embodiment the control unit <NUM> is configured to control the operation of the dishwasher components by running a respective routine (hereinafter, referred to as "washing cycle routine") <NUM>.

According to an embodiment, the washing cycle routine <NUM> allows the control unit <NUM> to control the dishwasher components for performing user-selected washing cycles. Just as non-exhaustive examples, based on an ongoing phase of the washing cycle, the washing cycle routine <NUM> may allow controlling the discharge of detergent into the tub <NUM>, and/or setting a target speed for the recirculation pump <NUM>, and/or selecting the spray device(s) <NUM>, <NUM>, <NUM>, and/or setting the temperature of the washing fluid.

As mentioned above, according to an embodiment the control unit <NUM> is configured to determine a saturation state or a starvation state of the circulation pump <NUM> by running a respective routine (hereinafter, referred to as "state routine") <NUM>.

According to an embodiment, the state routine <NUM> allows the control unit <NUM> to determine the operative state of the circulation pump <NUM> based on a trend (e.g., over time) of the (saturation and/or starvation) events detected by the detection unit <NUM> (and, hence, on the electromechanical parameters of the circulation pump motor <NUM> monitored or measured by the detection unit <NUM>).

As mentioned above, according to an embodiment the control unit <NUM> is configured to control the washing fluid filling and/or the circulation pump <NUM> and/or the drain pump <NUM> by running one or more respective routines.

According to an embodiment, the control unit <NUM> is configured to control the washing fluid filling by controlling the switch of the inlet valve <NUM> between the open and closed conditions according to the starvation state or saturation state of the circulation pump <NUM>.

According to an embodiment, the control unit <NUM> is configured to control the washing fluid filling by running a respective routine (hereinafter, referred to as "fill routine") <NUM>.

According to an embodiment, the fill routine <NUM> allows the control unit <NUM> to control the inlet valve <NUM> to load in the tub <NUM> amounts of washing fluid dosed in such a way to allow a correct operation of the dishwasher <NUM>.

According to an embodiment, the control unit <NUM> is configured to control the circulation pump <NUM> by running a respective routine (hereinafter referred to as "circulation routine") <NUM>.

According to an embodiment, the circulation routine <NUM> allows the control unit <NUM> to efficiently control a current speed of the circulation pump <NUM> based on a target speed (e.g., of an indication thereof) of the recirculation pump <NUM>.

According to an embodiment, the control unit <NUM> is configured to concurrently control the washing fluid filling and the circulation pump <NUM> by running a respective routine (hereinafter referred to as "interaction routine") <NUM>.

According to an embodiment, the interaction routine <NUM> allows the control unit <NUM> to control one or more washing filling components allowing the washing fluid filling (such as the inlet valve <NUM>) and one or more pump parameters of the circulation pump <NUM> (such as current and/or target speeds of the circulation pump <NUM>) based on the starvation state or saturation state of the circulation pump <NUM>, and to control the washing filling component(s) and the pump parameter(s) with respect to each other.

As graphically illustrated in <FIG>, the fill routine <NUM>, the circulation routine <NUM>, and the interaction routine <NUM> are configured to operate by taking into account the output produced by the state routine <NUM> i.e., by taking into account the operative state of the circulation pump <NUM> (i.e., saturation state or starvation state).

As will be discussed in the following, the fill routine <NUM>, the circulation routine <NUM>, and the interaction routine <NUM> allow the control unit <NUM> to efficiently control the operation of the dishwasher <NUM> without the need that the dishwasher <NUM> is equipped with a pressure sensor for the determination of the level of washing fluid inside the tub <NUM>. In this way, a correct and reliable operation of the dishwasher <NUM> can be guaranteed even if no pressure sensor is provided in the dishwasher <NUM> for the determination of the level of washing fluid inside the tub <NUM>.

With reference now to <FIG>, it shows an exemplary activity diagram of the state routine <NUM>, according to an embodiment of the present invention.

For the sake of description ease, <FIG> will be discussed by making joint reference to <FIG> shows an exemplary trend of saturation and starvation events detected by the detection unit <NUM> based on the monitored electromechanical parameter(s) (top drawing), and a corresponding output of the state routine <NUM> (bottom drawing), according to an embodiment of the present invention.

A number of (e.g., <NUM>) detected events (including both saturation and starvation events) are exemplary represented in the top drawing of <FIG>, from a first detected event (labeled by "<NUM>" in the abscissae axis) to a last detected event (labeled by "<NUM>" in the abscissae axis), it being understood that first and last detected events are not to be construed in absolute terms: indeed, the trend of detected events illustrated in the top drawing of <FIG> may represent a subset of saturation and starvation events being detected during a washing cycle of the dishwasher <NUM>.

Saturation and starvation events are graphically distinguished from each other in the top drawing of <FIG>: particularly, starvation events are represented as lines having a higher height with respect to the lines representing the saturation events.

According to an embodiment, each detected (saturation or starvation) event may be associated with a respective detection time instant. According to an embodiment, each detection time instant may depend on a detection frequency of the detection unit <NUM> (i.e., the number of electromechanical parameter(s) measurements per second). According to an embodiment, the detection frequency of the detection unit <NUM> may be set or controlled or adjusted according to specific design needs, e.g. during a design phase of the dishwasher <NUM>, and/or during a maintenance phase of the dishwasher <NUM>, and/or during an update phase of the dishwasher <NUM> (such as during an automatic or manual software/ firmware update procedure).

Just as an example, the detection frequency of the detection unit <NUM> may be equal to <NUM> (which corresponds to <NUM> electromechanical parameter(s) measurements per second, and hence to <NUM> detected events per second).

According to an embodiment, the output of the state routine <NUM> (bottom drawing of <FIG>) may comprise a digital signal (hereinafter referred to as output signal). According to an embodiment, the output signal may take a first logic level (e.g., a high logic level) "<NUM>" indicative of the saturation state, or a second logic level (e.g., a low logic level) "<NUM>" indicative of the starvation state.

Broadly speaking, the state routine <NUM> determines a starvation state of the circulation pump <NUM> when both a first starvation event and a second starvation event occurred after the first starvation event are determined, wherein the first starvation event is determined when a starvation event is detected after a first number of consecutive saturation events N1 is counted, or after a first time interval has elapsed during which no starvation event is detected (hereinafter, first time interval without starvation events ΔT1), and the second starvation event is determined when a starvation event is detected before a second number of consecutive saturation events N2 is counted after the first starvation event, or before a second time interval has elapsed after the first starvation event during which no starvation event is detected (hereinafter, second time interval without starvation events ΔT<NUM>).

According to an embodiment, consecutive saturation events are counted by means of a proper event counter (not shown). According to an embodiment, the event counter may be an internal entity located within the control unit <NUM> or within the detection unit <NUM>, or an external entity communicably coupled thereto.

According to an embodiment, time intervals are counted by means of a proper time counter (not shown). According to an embodiment, the time counter may be an internal entity located within the control unit <NUM> or within the detection unit <NUM>, or an external entity communicably coupled thereto.

According to an embodiment, the first number of consecutive saturation events N1 and the first time interval without starvation events ΔT1 are indicative of a stable saturation state of the circulation pump <NUM>, whereby a starvation event detected after the first number of consecutive saturation events N1 is counted or after the first time interval without starvation events ΔT1 has elapsed, could likely be a spurious starvation event.

According to an embodiment, the first number of consecutive saturation events N1 and the first time interval without starvation events ΔT1 may be set or controlled or adjusted according to specific design needs, for example during a design phase of the dishwasher <NUM>, and/or during a maintenance phase of the dishwasher <NUM>, and/or during an update phase of the dishwasher <NUM> (such as during an automatic or manual software/ firmware update procedure).

Just as an example, the first number of consecutive saturation events N1 may be equal to <NUM> and the first time interval without starvation events ΔT1 may be equal to <NUM> seconds.

According to an embodiment, the state routine <NUM> comprises, in response to detection of an event (action node <NUM>), determining if the detected event is a starvation event or a saturation event (decision node <NUM>).

According to an embodiment, the state routine <NUM> comprises, if the detected event is a starvation event (exit branch Y of the decision node <NUM>), and if the circulation pump <NUM> is in the saturation state (exit branch Y of the decision node <NUM>) determining if the detected starvation event may be a spurious starvation event (i.e., if it is a possible spurious starvation event) (decision node <NUM>).

As mentioned above, according to an embodiment, a detected starvation event is a possible spurious starvation event if it has been detected after the first number of consecutive saturation events N1 is counted, or after the first time interval without starvation events ΔT1 has elapsed.

According to an embodiment, the state routine <NUM> comprises, if the detected starvation event is a possible spurious starvation event (exit branch Y of the decision node <NUM>), the detected event is determined to be (e.g., marked as) the first starvation event (action node <NUM>).

In the example illustrated in <FIG>, in which the circulation pump <NUM> is in the saturation state (output signal at the "<NUM>" logic level), the eighth detected event is a starvation event, and this starvation event has been detected after the first number of consecutive saturation events N1 is counted, or after the first time interval without starvation events ΔT1 has elapsed, the eighth detected event is marked as the first starvation event.

Back to the activity diagram, according to an embodiment, after determination of the first starvation event the state routine <NUM> is restarted as such for the following event detection, and the starvation state of the circulation pump <NUM> is determined if, as mentioned above, the second starvation event is detected before the second number of consecutive saturation events N2 is counted after the first starvation event, or before the second time interval without starvation events ΔT2 has elapsed from the first starvation event (as better discussed here below).

According to an embodiment, the second number of consecutive saturation events N2 and the second time interval without starvation events ΔT2 may be set or controlled or adjusted according to specific design needs, for example during a design phase of the dishwasher <NUM>, and/or during a maintenance phase of the dishwasher <NUM>, and/or during an update phase of the dishwasher <NUM> (such as during an automatic or manual software/ firmware update procedure).

According to an embodiment, the first number of consecutive saturation events N1 is higher than second number of consecutive saturation events N2, and the first time interval without starvation events ΔT1 is higher than second time interval without starvation events ΔT2.

Just as an example, the second number of consecutive saturation events N2 may be equal to <NUM> and the second time interval without starvation events ΔT2 may be equal to <NUM> seconds.

According to an embodiment, the second number of consecutive saturation events N2 or the second time interval without starvation events ΔT2 is counted from the first starvation event or after a predefined pause time interval ΔTpause has elapsed from the first starvation event (as better discussed here below). According to an embodiment, the values of the second number of consecutive saturation events N2 or of the second time interval without starvation events ΔT2 may take into account these counting alternatives.

According to an embodiment, the state routine <NUM> comprises, if the detected starvation event follows a (previously determined) first starvation event (exit branch Y of decision node <NUM>), determining if the detected starvation event is a second starvation event (decision node <NUM>).

As mentioned above, according to an embodiment, a detected starvation event is a second starvation event if it has been detected before the second number of consecutive saturation events N2 is counted after the first starvation event, or before the second time interval without starvation events ΔT2 has elapsed from the first starvation event.

According to an embodiment, if the detected starvation event has been detected before the second number of consecutive saturation events N2 is counted after the first starvation event, or before the second time interval without starvation events ΔT2 has elapsed after the first starvation event (exit branch Y of the decision node <NUM>), the detected starvation event is determined to be (e.g., marked as) the second starvation event (action node <NUM>), and the starvation state of the circulation pump <NUM> is determined (action node <NUM>). In other words, according to an embodiment, the state routine <NUM> comprises determining the starvation state of the circulation pump <NUM> when both the first starvation event and the second starvation event are determined.

In the example illustrated in <FIG>, in which the circulation pump <NUM> is in the saturation state (output signal at the "<NUM>" logic level), the forty-first detected event is a starvation event, and this starvation event has been detected before the second number of consecutive saturation events N2 is counted after the first starvation event, or before the second time interval without starvation events ΔT2 has elapsed from the first starvation even, the forty-first detected event is marked as the second starvation event and the output signal is switched from the "<NUM>" logic level to the "<NUM>" logic level (which indicates that the starvation state of the circulation pump <NUM> is determined). In this example, as better discussed in the following, the second number of consecutive saturation events N2 or the second time interval without starvation events ΔT2 are counted after the predefined pause time interval ΔTpause has elapsed from the first starvation event (although this should not be construed limitatively).

According to an embodiment, if the detected starvation has been detected after the second number of consecutive saturation events N2 is counted after the first starvation event, or after the second time interval without starvation events ΔT2 has elapsed after the first starvation event (exit branch N of the decision node <NUM>), the saturation state of the circulation pump <NUM> is determined (i.e., confirmed) (action node <NUM>), thereafter the state routine <NUM> is restarted as such for the following event detection (as conceptually represented in the figure by loop connection between action nodes <NUM> and <NUM>). In other words, according to an embodiment, the state routine <NUM> comprises determining the saturation state of the circulation pump <NUM> if no second starvation event is determined (i.e., if no starvation event is detected before the second number of consecutive saturation events N2 is counted after the first starvation event, or before the second time interval without starvation events ΔT2 has elapsed after the first starvation event).

Back to decision node <NUM>, according to an embodiment, if the detected event is a saturation event (exit branch N of the decision node <NUM>), and if the circulation pump <NUM> is in the saturation state (exit branch Y of the decision node <NUM>), no actions are taken (in that the detected saturation event is consistent with the saturation state of the circulation pump <NUM>), and the state routine <NUM> is restarted as such for the following event detection (as conceptually represented in the figure by loop connection between exit branch Y of the decision node <NUM> and action node <NUM>).

According to an embodiment, the state routine <NUM> comprises, if the detected event is a saturation event (exit branch N of the decision node <NUM>), and if the circulation pump <NUM> is in the starvation state (exit branch N of the decision node <NUM>), determining the saturation state of the circulation pump <NUM> after a third number of consecutive saturation events N3 is counted from determination of the starvation state, or after a third time interval without starvation events ΔT3 has elapsed from determination of the starvation state (see nodes <NUM> and <NUM>, discussed here below).

According to an embodiment, the third number of consecutive saturation events N3 and the third time interval without starvation events ΔT3 may be set or controlled or adjusted according to specific design needs, for example during a design phase of the dishwasher <NUM>, and/or during a maintenance phase of the dishwasher <NUM>, and/or during an update phase of the dishwasher <NUM> (such as during an automatic or manual software/ firmware update procedure).

Just as an example, the third number of consecutive saturation events N3 may be equal to the second number of consecutive saturation events N3, and the third time interval without starvation events ΔT3 may be equal to the second time interval without starvation events ΔT2.

According to an embodiment, the state routine <NUM> comprises, if the detected saturation event has been detected after the third number of consecutive saturation events N3 is counted from determination of the starvation state, or after the third time interval without starvation events ΔT3 has elapsed from determination of the starvation state (exit branch Y of the decision node <NUM>), determining the saturation state of the circulation pump <NUM> (action node <NUM>), thereafter the state routine <NUM> is restarted as such for the following event detection (as conceptually represented in the figure by loop connection between action nodes <NUM> and <NUM>).

In the example illustrated in <FIG>, in which the circulation pump <NUM> is in the starvation state (output signal at the "<NUM>" logic level) from the forty-first detected event, and the sixty-first detected event is a saturation event detected after the third number of consecutive saturation events N3 is counted after the determination of the starvation state, or after the third time interval without starvation events ΔT3 has elapsed from the determination of the starvation state, at the sixty-first detected event the output signal is switched from the "<NUM>" logic level to the "<NUM>" logic level (which indicates that the saturation state of the circulation pump <NUM> is determined).

According to an embodiment, if the detected saturation event has been detected before the third number of consecutive saturation events N3 is counted from determination of the starvation state, or before the third time interval without starvation events ΔT3 has elapsed from the determination of the starvation state (exit branch N of the decision node <NUM>), no actions are taken (i.e., circulation pump <NUM> still in the starvation state), and the state routine <NUM> is restarted as such for the following event detection (as conceptually represented in the figure by loop connection between exit branch N of the decision node <NUM> and action node <NUM>).

Back to decision node <NUM>, according to an embodiment, the state routine <NUM> comprises, if the detected event is a starvation event (exit branch Y of the decision node <NUM>) and the circulation pump <NUM> is in the starvation state (exit branch N of the decision node <NUM>), no actions are taken (in that the detected starvation event is consistent with the starvation state of the circulation pump <NUM>), thereafter the state routine <NUM> is restarted as such for the following event detection (as conceptually represented in the figure by loop connection between exit branch N of the decision node <NUM> and action node <NUM>).

Back to the action node <NUM>, according to an embodiment the state routine <NUM> comprises pausing the operation of the detection unit <NUM> for the predefined pause time interval ΔTpause after the first starvation event is determined (action node <NUM>), and resuming the operation of the detection unit <NUM> (action node <NUM>) after the predefined pause time interval ΔTpause has elapsed (see loop node <NUM>).

According to an embodiment, the predefined pause time interval ΔTpause may be set or controlled or adjusted according to specific design needs, for example during a design phase of the dishwasher <NUM>, and/or during a maintenance phase of the dishwasher <NUM>, and/or during an update phase of the dishwasher <NUM> (such as during an automatic or manual software/ firmware update procedure).

According to an embodiment, the predefined pause time interval ΔTpause may be lower than the first time interval without starvation events ΔT1.

According to an embodiment, the predefined pause time interval ΔTpause may be the amount of time that, in case that a detected starvation event is a spurious starvation event, could be reasonably expected to take by the circulation pump <NUM> to resolve or substantially resolve any transitory or temporary conditions having determined that spurious starvation event.

Just as an example, the predefined pause time interval ΔTpause may be equal to <NUM> seconds (although this should not be construed limitatively).

Back to action node <NUM>, according to an embodiment the state routine <NUM> comprises, if the detected starvation event is not a possible spurious starvation event (exit branch N of the decision node <NUM>), and if the detected starvation event does not follow a (previously determined) first starvation event (exit branch N of decision node <NUM>), the starvation state of the circulation pump <NUM> is determined (action node <NUM>), and the state routine <NUM> is restarted as such for the following event detection (as represented in the figure by loop connection between action nodes <NUM> and <NUM>). In other words, according to an embodiment, the state routine <NUM> comprises, with the circulation pump <NUM> in the saturation state, determining the starvation state of the circulation pump <NUM> if a starvation event is not a first starvation event and if it does not follow a first starvation event (i.e., if the closest previous starvation event is not a first starvation event).

In the example illustrated in <FIG>, in which the circulation pump <NUM> is in the saturation state (output signal at the "<NUM>" logic level) from the sixty-first detected event (and the closest previous starvation event is not a first starvation event), and the sixty-fifth detected event is a starvation event detected before the second number of consecutive saturation events N2 is counted from the determination of the saturation state, or before the second time interval without starvation events ΔT2 has elapsed from the determination of the saturation state, at the sixty-fifth detected event the output signal is switched from the "<NUM>" logic level to the "<NUM>" logic level (which indicates that the starvation state of the circulation pump <NUM> is determined).

With reference now to <FIG>, it shows an exemplary activity diagram of the fill routine <NUM>, according to an embodiment of the present invention.

Broadly speaking, according to an embodiment of the fill routine <NUM>, the control unit <NUM> is configured to receive an indication of a current speed of the circulation pump and an indication of a target speed for the circulation pump <NUM> (the target speed being for example based on a user-selected washing cycle and/or on a phase of the user-selected washing cycle), and to control the switch of the inlet valve <NUM> by:
causing the inlet valve <NUM> to switch from the open condition to the closed condition if the following two conditions a) and b) are both true:.

Broadly speaking, according to an embodiment of the fill routine <NUM>, the control unit <NUM> is configured to control the switch of the inlet valve <NUM> further by:
delaying the switch of the inlet valve <NUM> from the open condition to the closed condition by a delay interval if, in addition to have both the conditions a) and b) that are true, the difference between the target speed and the current speed of the circulation pump <NUM> is higher than a speed threshold.

Broadly speaking, according to an embodiment of the fill routine <NUM>, a duration of the delay interval is based on the difference between the target speed and the current speed of the circulation pump <NUM>.

Broadly speaking, according to an embodiment of the fill routine <NUM>, the control unit <NUM> is configured to control the washing fluid filling by:
causing the inlet valve <NUM> to switch from the open condition to the closed condition if, in addition to have the condition a) that is true, the condition b) is not true.

Broadly speaking, according to an embodiment of the fill routine <NUM>, the control unit <NUM> is configured to control the washing fluid filling by:
causing the inlet valve <NUM> to switch from the open condition to the closed condition if both the conditions a) and b) are not true.

Broadly speaking, according to an embodiment of the fill routine <NUM>, the control unit <NUM> is configured to control the washing fluid filling by:
causing the inlet valve <NUM> to switch from the closed condition to the open condition if, in addition to have the condition b) that is true, the condition a) is not true.

Broadly speaking, according to an embodiment of the fill routine <NUM>, the fill routine <NUM> provides for causing the inlet valve <NUM> to be opened in order to fill washing fluid in the tub <NUM> when the current speed (SC) of the circulation pump <NUM> is lower than or equal to the target speed (TS) if a starvation state of the circulation pump <NUM> is determined. According to an embodiment of the fill routine <NUM>, the fill routine <NUM> also provides for causing the inlet valve <NUM> to be closed if a saturation state of the circulation pump <NUM> is determined. According to an embodiment of the fill routine <NUM>, in order to reduce the number of times the inlet valve <NUM> switches between the open and closed conditions, the closure of the valve is delayed in case the speed SC of the circulation pump <NUM> is lower than the target speed TS by a sufficiently large amount.

The fill routine <NUM> will be now discussed by making reference to the activity diagram of <FIG>.

According to an embodiment, the fill routine <NUM> may switch between two different states, and namely a so-called "valve open state" (action node <NUM>) corresponding to an open condition of the inlet valve <NUM> for causing new washing fluid to be fed to the dishwasher <NUM> for being loaded in the tub <NUM>, and a so-called "valve closed state" (action node <NUM>) corresponding to a closed condition of the inlet valve <NUM> for preventing new washing fluid to be fed to the dishwasher <NUM>.

The initial state of the fill routine <NUM> depends on the current state of the inlet valve <NUM>.

Starting from the valve closed state (action node <NUM>), in which the inlet valve <NUM> is in the closed condition, according to an embodiment, if a starvation state of the circulation pump <NUM> is determined (action node <NUM>), when the current speed SC of the circulation pump <NUM> is equal to or lower than the target speed TS (action node <NUM>), the control unit <NUM> causes the inlet valve <NUM> to switch to the open condition for causing new washing fluid to be fed in the tub <NUM> (action node <NUM>). Then, the fill routine <NUM> switches to the valve open state (going to action node <NUM>).

According to an embodiment, if instead a saturation state of the circulation pump <NUM> is determined (action node <NUM>), when the current speed SC of the circulation pump <NUM> is equal to or higher than the target speed TS (action node <NUM>), the fill routine <NUM> terminates.

According to an embodiment, when the fill routine <NUM> is in the valve open state (action node <NUM>), and a starvation state of the circulation pump <NUM> is determined (action node <NUM>), when the current speed SC of the circulation pump <NUM> is higher than the target speed TS (action node <NUM>), the control unit <NUM> causes the inlet valve <NUM> to switch to the closed condition for preventing new washing fluid be fed to the dishwasher <NUM> (action node <NUM>). Then the fill routine <NUM> switches the valve closed state (going to action node <NUM>).

According to an embodiment, when the fill routine <NUM> is in the valve open state (action node <NUM>), and a saturation state of the circulation pump <NUM> is determined (action node <NUM>), when the current speed SC of the circulation pump <NUM> is equal to or higher than the target speed TS (action node <NUM>), the control unit <NUM> causes the inlet valve <NUM> to switch to the closed condition for preventing new washing fluid be fed to the dishwasher <NUM> (action node <NUM>). Then, the fill routine <NUM> switches to the valve closed state (going to action node <NUM>).

According to an embodiment, when the fill routine <NUM> is in the valve open state (action node <NUM>), and a saturation state of the circulation pump <NUM> is determined (action node <NUM>), when the current speed SC of the circulation pump <NUM> is lower than the target speed TS (action node <NUM>), the control unit <NUM> checks (decision node <NUM>) if the current speed SC is however close to (e.g., only slightly lower than) the target speed TS, or if the current speed SC is still far from (e.g., substantially lower than) the target speed TS.

According to an embodiment, if the difference between the target speed TS and the current speed SC of the circulation pump <NUM> is not higher than a speed threshold THC (exit branch N of decision node <NUM>), the control unit <NUM> directly causes the inlet valve <NUM> to switch to the closed condition for preventing new washing fluid be fed to the dishwasher <NUM> (action node <NUM>). Then, the fill routine <NUM> switches to the valve closed state (going to action node <NUM>).

According to an embodiment, if the difference between the target speed TS and the current speed SC of the circulation pump <NUM> is higher than a speed threshold THC (exit branch Y of decision node <NUM>), the control unit <NUM> causes a delayed switching of the inlet valve <NUM> to the closed condition. According to an embodiment, the control unit <NUM> causes the inlet valve <NUM> to switch to the closed position only after a delay interval DIF is expired.

According to an embodiment, the speed threshold THe is higher than <NUM> RPM and lower than <NUM> RPM, the speed threshold THC being for example equal to <NUM> RPM.

According to an embodiment, the duration of the delay interval DIF depends on the difference ΔF between the target speed TS and the current speed SC of the circulation pump <NUM>.

According to an embodiment, the control unit <NUM> sets the delay interval DIF (action node <NUM>) to a value that is proportional to the difference ΔF between the target speed TS and the current speed SC of the circulation pump <NUM>. According to an embodiment, the delay interval DIF is set to a maximum predetermined value MDIF if the difference ΔF is excessively large. For example, according to an embodiment, the control unit <NUM> sets the delay interval DIF to the minimum value between:.

wherein PF is a proportionality parameter.

For example, MDIF may be set to <NUM> and PF may be set to <NUM>.

According to an embodiment, when the delay interval DIF is expired (action node <NUM>), the control unit <NUM> causes the inlet valve <NUM> to switch to the closed condition for preventing new washing fluid be fed to the dishwasher <NUM> (action node <NUM>). Then, the fill routine <NUM> switches to the valve closed state (going to action node <NUM>).

By delaying the closure of the inlet valve <NUM> when the speed SC is still far from (e.g., substantially lower than) the target speed TS, an additional amount of washing fluid is fed into the tub <NUM>, advantageously reducing the possibility that, once the inlet valve <NUM> is in the closed condition, the circulation pump <NUM> enters into the starvation state (with a consequent reopening of the inlet valve <NUM>). In this way, undesired "bouncing" between the open and closed condition of the inlet valve <NUM> is advantageously reduced.

Thanks to the fill routine <NUM>, it is possible to efficiently control the inlet valve <NUM> to load in the tub <NUM> amounts of washing fluid dosed in such a way to allow a correct operation of the dishwasher <NUM> when the latter is operating with the circulation pump <NUM> at a current speed SC based on said target speed TS, without requiring the presence of a pressure sensor for the determination of the current level of washing fluid inside the tub <NUM>.

With reference now to <FIG>, it shows an exemplary activity diagram of the circulation routine <NUM>, according to an embodiment of the present invention.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the control unit <NUM> is configured to control the circulation pump <NUM> by controlling a speed increase rate of the circulation pump <NUM> from the current speed towards the target speed according to the starvation state or saturation state of the circulation pump <NUM> and according to the open and closed condition of the inlet valve <NUM>.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the control unit <NUM> is configured to cause the current speed of the circulation pump <NUM> to increase towards the target speed with a first speed increase rate, and to control the speed increase rate of the circulation pump <NUM> from current speed towards the target speed by:
causing the current speed of the circulation pump <NUM> to increase towards the target speed with a second speed increase rate lower than the first speed increase rate, if the following two conditions a) and b) are both true:.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the control unit <NUM> is configured to control the circulation pump <NUM> by causing the current speed of the circulation pump <NUM> to be decreased if the condition a) is true while condition b) is not true.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the control unit <NUM> is configured to control the circulation pump <NUM> by causing the current speed of the circulation pump <NUM> to increase towards the target speed with the second speed increase rate if, in addition to have both the conditions a) and b) that are true, no saturation state of the circulation pump <NUM> is determined during a predetermined time period after the determination of a starvation state of the circulation pump <NUM>.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the control unit <NUM> is configured to cause the current speed of the circulation pump <NUM> to increase towards the target speed with a third speed increase rate lower than the first speed increase rate and higher than the second speed increase rate if the circulation pump <NUM> has reached the target speed before a starvation state of the circulation pump <NUM> is determined.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the control unit <NUM> is configured to cause the current speed of the circulation pump <NUM> to increase towards the target speed with the third speed increase rate if, in addition to have the condition a) true, a saturation state of the circulation pump <NUM> is determined during said predetermined time period.

Broadly speaking, according to an embodiment of the circulation routine <NUM>, the third speed increase rate is equal to:.

Broadly speaking, according to an embodiment, the circulation routine <NUM> provides for causing the current speed SC of the circulation pump <NUM> to increase towards the target speed TS with a first speed increase rate R1. If a starvation state of the circulation pump <NUM> is determined, and at the same time the inlet valve <NUM> is in the open condition (causing thus washing fluid being loaded into the tub <NUM>) before the current speed SC of the circulation pump <NUM> reached the target speed TS, the current speed SC of the circulation pump <NUM> is set to increase towards the target speed TS with a second speed increase rate R2 lower than the first speed increase rate R1.

The circulation routine <NUM> will be now discussed by making reference to the activity diagram of <FIG>.

According to an embodiment, the control unit <NUM> sets a first increase rate R1 for the speed SC of the circulation pump <NUM> (action node <NUM>).

Then, according to an embodiment, the circulation routine <NUM> enters in a so-called "initial speed ramp state" in which the control unit <NUM> causes the current speed SC of the circulation pump <NUM> to increase - from a starting value, e.g., equal to zero if the circulation pump <NUM> is stopped - towards the target speed TS with said first increase rate R1 (action node <NUM>). According to an embodiment, the value of the target speed TS is set by the washing cycle routine <NUM>, depending on a user-selected washing cycle (and/or based on a phase thereof) being currently carried out by the dishwasher <NUM>.

According to an embodiment, the first increase rate R1 is higher than <NUM> RPM/s, such as for example equal to <NUM> RPM/s.

According to an embodiment, if a starvation state of the circulation pump <NUM> is determined (by the state routine <NUM>) before the current speed SC of the circulation pump <NUM> reached the target speed TS (action node <NUM>), the control unit <NUM> initializes a timer TC (action node <NUM>) and starts the timer TC to count a predetermined time period (e.g., <NUM>). Then, the circulation routine <NUM> enters in a so-called "starving state" (action node <NUM>), in which the current speed SC of the circulation pump <NUM> is caused to increase by the control unit <NUM> with the actually set increase rate while the circulation pump <NUM> is determined to be in the starvation state.

According to an embodiment, if the timer TC elapses without having a saturation state of the circulation pump <NUM> be determined by the state routine <NUM> (action node <NUM>), the control unit <NUM> checks if the inlet valve <NUM> is in the open condition or in the closed position (decision node <NUM>). According to an embodiment, the condition (open or closed) of the inlet valve <NUM> is set by the fill routine <NUM>.

According to an embodiment, if the inlet valve <NUM> is in the closed position (exit branch N of decision node <NUM>), meaning that no new washing fluid is being fed into the tub <NUM> from outside the dishwasher <NUM>, the control unit <NUM> causes the increasing rate of the current speed SC of the circulation pump <NUM> to be set to zero, and causes the current speed SC of the circulation pump <NUM> to be decreased by a corresponding decreasing amount DSC (action node <NUM>).

According to an embodiment, if the inlet valve <NUM> is in the open condition (exit branch Y of decision node <NUM>), meaning that new washing fluid is being fed into the tub <NUM> from outside the dishwasher <NUM>, the control unit <NUM> checks (decision node <NUM>) if the highest value reached by the current speed SC of the circulation pump <NUM> has been subjected to any increase for a corresponding time period (e.g., <NUM>). In case the highest value reached by the current speed SC of the circulation pump <NUM> did not increase during said time period (exit branch N of decision node <NUM>), the control unit <NUM> stops (action node <NUM>) the circulation pump <NUM> for a time interval, such as for <NUM>, for removing air from the circulation pump <NUM>, and then the operations flow returns to action node <NUM>. In case the highest value reached by the current speed SC of the circulation pump <NUM> did increase at least once during said time period (exit branch Y of decision node <NUM>), the control unit <NUM> causes the current speed SC of the circulation pump <NUM> to increase towards the target speed TS with a second increase rate R2 lower than the first increase rate R1 (action node <NUM>). According to an embodiment, said decreasing amount DSC is equal to <NUM> RPM/s. According to an embodiment, said second increase rate R2 is lower than <NUM> RPM/s, such as for example equal to <NUM> RPM/s.

Then, the control unit <NUM> reinitializes the timer TC and starts the timer TC to count a further time period (action node <NUM>), for example <NUM>.

At this point, the operations flow returns to action node <NUM>, where the previously described operations are reiterated, with the reinitialised timer TC and the new value of the current speed SC and/or the new value for the increase rate of the current speed SC.

According to an embodiment, if a saturation state of the circulation pump <NUM> is determined by the state routine <NUM> before the timer TC elapses (action node <NUM>), after a further time period is expired (e.g., <NUM>), the circulation routine <NUM> enters in a so-called "saturating state" (action node <NUM>), in which the current speed SC of the circulation pump <NUM> is caused to increase by the control unit <NUM> with a third increase rate R3 lower than the first increase rate R1 and higher than the second increase rate R2 while the circulation pump <NUM> is determined to be in the saturation state. According to an embodiment, the value of the third increase rate R3 depends on the condition (open/closed) of the inlet valve <NUM>. According to an embodiment, if the inlet valve <NUM> is in the open condition, the third increase rate R3 is higher than <NUM> RPM/s, for example equal to <NUM> RPM/s, while if the inlet valve <NUM> is in the closed condition, the third increase rate R3 is lower than <NUM> RPM/s, for example equal to <NUM> RPM/s.

Then, according to an embodiment, when a starvation state of the circulation pump <NUM> is determined again by the state routine <NUM> (action node <NUM>), the operations flow returns to action node <NUM>, wherein the control unit <NUM> reinitializes the timer TC and the circulation routine <NUM> enters again in the starving state (action node <NUM>).

Returning back to action node <NUM>, according to an embodiment, if the current speed SC of the circulation pump <NUM> reaches the target speed TS before a starvation state of the circulation pump <NUM> is determined by the state routine <NUM> (action node <NUM>), the operations flow goes to action node <NUM>, where the circulation routine <NUM> enters in the saturating state.

When carrying out the circulation routine <NUM> according to the embodiments illustrated in <FIG>, the control unit <NUM> tries to cause the circulation pump <NUM> to operate at the target speed TS by increasing the current speed SC of the circulation pump <NUM> starting from a starting value with a corresponding speed increase rate (action nodes <NUM>, <NUM>). The target speed TS can be reached without causing the circulation pump <NUM> to enter in the starvation state (action node <NUM>). If the target speed TS cannot be reached without causing a starvation state of the circulation pump <NUM> (action node <NUM>), the control unit <NUM> controls the current speed SC to reach the highest speed capable of maintaining the circulation pump <NUM> in the saturation state. This is done by slowly increasing the current speed SC until a starvation state of the circulation pump <NUM> is detected, and then:.

With joint reference to <FIG>, it shows an exemplary time diagram showing circulation pump speed variations over time during running of circulation routine <NUM>.

In the example illustrated in <FIG>, the circulation pump <NUM> is initially turned off, and therefore the current speed SC is equal to zero. At time tc(<NUM>), the circulation routine <NUM> is started, and the control unit <NUM> causes the circulation pump <NUM> to increase the current speed SC of the circulation pump <NUM> with a corresponding first speed increase rate R1 (action nodes <NUM>, <NUM>). At time tc(<NUM>), a starvation state of the circulation pump <NUM> is determined, before the current speed SC of the circulation pump <NUM> reached the target speed TS (action node <NUM>). At this point, the control unit <NUM> initializes and starts the timer TC to count a predetermined time period (action node <NUM>). In the considered example, the timer TC expires at time tc(<NUM>) before a saturation state of the circulation pump <NUM> is determined (action node <NUM>). In the considered example, at time tc(<NUM>) the inlet valve <NUM> is in the open condition (exit branch Y of decision node <NUM>), and therefore the control unit <NUM> verifies if the highest value reached by the current speed SC of the circulation pump <NUM> has been subjected to any increase during a past time period from time tc(<NUM>) (decision node <NUM>). Since in the considered example the current speed SC of the circulation pump <NUM> was constantly increasing from time tc(<NUM>) to time tc(<NUM>), this condition is verified (exit branch Y of decision node <NUM>), and therefore the control unit <NUM> varies the increase rate of the current speed SC of the circulation pump <NUM> to a second speed increase rate R2 lower than the first speed increase rate R1 (action node <NUM>).

Thanks to the circulation routine <NUM>, it is therefore possible to efficiently control the current speed SC of the circulation pump <NUM> to reach a value corresponding to a requested target speed TS without requiring the presence of a pressure sensor for the determination of the level of washing fluid currently inside the tub <NUM>.

With reference to <FIG>, it shows, in terms of schematic functional blocks, the interaction routine <NUM> according to an embodiment of the present invention.

As mentioned above, according to an embodiment, the interaction routine <NUM> allows the control unit <NUM> to control one or more washing filling components allowing the washing fluid filling (such as the inlet valve <NUM>) and one or more pump parameters of the circulation pump <NUM> (such as current and/or target speeds of the circulation pump <NUM>) based on the starvation state or saturation state of the circulation pump <NUM>, and to control the washing filling component(s) and the pump parameter(s) with respect to each other.

According to an embodiment, interaction routine <NUM> is based on concurrent running of the fill routine <NUM> and of circulation routine <NUM>.

This is based on the fact that, each one of these two routines (i.e., the fill routine <NUM> and the circulation routine <NUM>) requires, among its inputs, information that can be output by the other routine.

Particularly, in order to be correctly executed, the circulation routine <NUM> requires to receive the indication of the target speed TS, an indication of the operative state PC (starvation state or saturation state) of the circulation pump <NUM>, and an indication of the condition VC (open condition or closed condition) of the inlet valve <NUM>. Moreover, in order to be correctly execute, the fill routine <NUM> requires to receive the indication of the target speed TS, the indication of the operative state PC of the circulation pump <NUM>, and an indication of the current speed SC of the circulation pump <NUM>.

By making reference to the schematic functional block of <FIG>, since the current speed SC of the circulation pump <NUM> is set by the circulation routine <NUM> (based on TS, PC, VC), and the condition VC of the inlet valve <NUM> is set by the fill routine <NUM> (based on TS, PC, SC), according to an embodiment the circulation routine <NUM> and the fill routine <NUM> may be advantageously executed concurrently, using the indication of the condition VC of the inlet valve <NUM> set by the fill routine <NUM> as an input for the circulation routine <NUM>, and using the indication of the current speed SC of the circulation pump <NUM> set by the circulation routine <NUM> as an input for the fill routine <NUM>.

According to an embodiment, when the circulation routine <NUM> and the fill routine <NUM> are concurrently executed, each one of said routines may operate by using a respective different target speed TS.

According to an embodiment, the control unit <NUM> may control the current speed SC of the circulation pump <NUM> (by running the circulation routine <NUM>) based on:.

According to an embodiment, the control unit <NUM> may control the condition VC of the inlet valve <NUM> (by running the fill routine <NUM>) based on:.

For example, if the first target speed TS1 is set to a value higher than the value of the second target speed TS2 (e.g., TS1 is set to <NUM> RPM, and TS2 is set to <NUM> RPM), as long as the current speed SC of the circulation pump <NUM> is equal to or lower than TS2, both the two routines are carried out by the control unit <NUM>. When the current speed SC of the circulation pump <NUM> is higher than TS2, the fill routine <NUM> is prevented to cause the opening of the inlet valve <NUM>.

Claim 1:
Washing appliance (<NUM>) comprising:
a tub (<NUM>) to house items to be washed;
a circulation pump (<NUM>) to circulate a washing fluid in the tub;
a circulation pump motor (<NUM>) to drive the circulation pump;
a drain pump (<NUM>);
a detection unit (<NUM>) configured to monitor at least one electromechanical parameter of the circulation pump motor, and to detect, based on the monitored at least one electromechanical parameter, a starvation event indicating that air is drawn out by the circulation pump or a saturation event indicating that no air is drawn out by the circulation pump, and
a control unit (<NUM>) configured to determine a first starvation event and a second starvation event occurred after said first starvation event,
and wherein the control unit is configured to:
determine a starvation state of the circulation pump when both the first starvation event and the second starvation event are determined, said starvation state indicating that insufficient washing fluid is present in the tub to prevent air from being drawn out by the circulation pump;
determine a saturation state of the circulation pump if said second starvation event is not determined, said saturation event indicating that sufficient washing fluid is present in the tub to prevent air from being drawn out by the circulation pump, and
control the washing appliance based on the determined starvation state or saturation state of the circulation pump,
characterised in that
the first starvation event is determined when a starvation event is detected after a first number of consecutive saturation events (N1) is counted, or after a first time interval (ΔT1) has elapsed during which no starvation event is detected, and that the second starvation event is determined when a starvation event is detected before a second number of consecutive saturation events (N2) is counted after the first starvation event, or before a second time interval (ΔT2) has elapsed after the first starvation event during which no starvation event is detected, said first number of consecutive saturation events (N1) being higher than said second number of consecutive saturation events (N2) and said first time interval (ΔT1) being higher than said second time interval (ΔT<NUM>).