Process water flow detection in circulation pump

Abstract

Provided are 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.

Claims

1. Method of detecting a change in process water flow of a circulation pump in an appliance for washing and rinsing goods, comprising: measuring a property indicating torque of the circulation pump; averaging a first set of values of the measured property, thereby creating a first average; averaging at least a further set of values of the measured property, thereby creating at least one further average; comparing the first average with the at least one further average; and detecting the change in process water flow of the circulation pump based on a difference between the first average and the at least one further average.

2. The method of claim 1, wherein the comparing the first average with the at least one further average comprises: calculating a difference between the first average and the at least one further average; determining whether said difference complies with a predetermined threshold criterion; and if so: detecting a decrease in process water flow of the circulation pump.

3. The method of claim 2, wherein the determining whether said difference complies with a predetermined threshold criterion comprises: determining whether said difference exceeds a predetermined threshold value.

4. The method of claim 1, wherein the averaging of at least a further set of values of the measured property comprises: averaging a plurality of sets of values of the measured property, thereby creating a corresponding plurality of averages; and wherein the comparing of the first average with the at least one further average comprises: comparing the first average with each of said plurality of averages; and wherein the detecting of the change in process water flow comprises: detecting the change in process water flow of the circulation pump based on differences between the first average and each of said plurality of averages.

5. The method of claim 4, wherein the comparing of the first average with the at least one further average comprises: calculating a difference between the first average and each of the plurality averages; determining whether each calculated difference complies with a predetermined threshold criterion; and if so: detecting a decrease in process water flow of the circulation pump.

6. The method of claim 5, wherein the determining whether each calculated difference complies with a predetermined threshold criterion comprises: determining whether each calculated difference exceeds a corresponding predetermined threshold value.

7. The method of claim 1, wherein averaging at least a further set of values of the measured property thereby creating at least one further average comprises creating a second further average and a third further average, wherein calculating a difference between the first average and the at least one further average comprises calculating a difference between the first average and the second further average and calculating a difference between the first average and the third further average, wherein detecting the change in process water flow of the circulation pump based on the difference between the first average and the at least one further average comprises detecting the change in process water flow of the circulation pump based on the difference between the first average and the at second further average and based on the difference between the first average and the third further average.

8. The method of claim 2, further comprising: controlling a valve to supply additional water in response to detecting the decrease in process water flow of the circulation pump.

9. The method of claim 1, wherein measuring a property indicating torque of the circulation pump is performed in response to the circulation pump circulating process water to at least one wash arm.

10. A computer program comprising computer-executable instructions for causing a device to perform steps recited in claim 1 when the computer-executable instructions are executed on a processing unit included in the device.

11. A computer program product comprising a computer readable medium, the computer readable medium having the computer program according to claim 10 embodied thereon.

12. An appliance for washing and rinsing goods, comprising: a circulation pump; a sensing arrangement arranged to measure a property indicating torque of the circulation pump; and a controller 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 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.

13. The appliance of claim 12, the controller further being arranged to, when comparing the first average with the at least one further average: calculate a difference between the first average and the at least one further average; determine whether said difference complies with a predetermined threshold criterion; and if so detect a decrease in process water flow of the circulation pump.

14. The appliance of claim 13, the controller further being arranged to, when determining whether said difference complies with a predetermined threshold criterion comprises: determine whether said difference exceeds a predetermined threshold value.

15. The appliance of claim 12, the controller further being arranged to, when averaging at least a further set of values of the measured property: average a plurality of sets of values of the measured property, thereby creating a corresponding plurality of averages; and being arranged to, when comparing the first average with the at least one further average: compare the first average with each of said plurality of averages; and detect the change in process water flow of the circulation pump based on differences between the first average and each of said plurality of averages.

16. The appliance of claim 15, the controller further being arranged to, when comparing the first average with the at least one further average: calculate a difference between the first average and each of the plurality averages; determine whether each calculated difference complies with a predetermined threshold criterion; and if so detect a decrease in process water flow of the circulation pump.

17. The appliance of claim 16, the controller further being arranged to, when determining whether each calculated difference complies with a predetermined threshold criterion: determine whether each calculated difference exceeds a corresponding predetermined threshold value.

18. The appliance of claim 12, the sensing arrangement being arranged to measure operating current of a motor driving the circulation pump in order to attain a representation of the property indicating torque of the circulation pump.

19. The appliance of claim 18, wherein the sensing arrangement comprises: a resistor arranged at the motor driving the circulation pump, through which resistor operating current of the motor is measured, in order to attain the representation of the property indicating torque of the circulation pump.

20. The appliance of claim 12, further comprising: a drain pump, wherein the circulation pump is configured to circulate process water through at least one wash arm during a wash cycle, wherein the drain pump is configured to drain water from the appliance during a drain cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a prior art dishwasher in which the present invention may be implemented;

(3) FIG. 2 schematically illustrates a cross-sectional view of the dishwasher of FIG. 1 taken along section II;

(4) FIGS. 3a and b illustrate two different views of a circulation pump through which a change in process water flow may be determined according to embodiments of the invention;

(5) FIG. 4 illustrates fluctuations in circulation pump operating current over time;

(6) FIG. 5 shows a flowchart illustrating an embodiment of a method of detecting a change in process water flow of a circulation pump according to the invention;

(7) FIG. 6 illustrates a decrease in circulation pump operating current over time;

(8) FIG. 7 shows a flowchart illustrating another embodiment of a method of detecting a change in process water flow of a circulation pump according to the invention;

(9) FIG. 8 illustrates further decrease in circulation pump operating current over time;

(10) FIG. 9 shows a flowchart illustrating a further embodiment of a method of detecting a change in process water flow of a circulation pump according to the invention; and

(11) FIG. 10 illustrates a further scenario where circulation pump operating current decreases over time.

DETAILED DESCRIPTION

(12) The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description. The washing appliance of the invention will subsequently be exemplified by a dishwasher.

(13) FIG. 1 shows a prior art dishwasher 1 in which the present invention can be implemented. It should be noted that dishwashers can take on many forms and include many different functionalities. The dishwasher 1 illustrated in FIG. 1 is thus used to explain different embodiments of the present invention and should only be seen as an example of a dishwasher in which the present application can be applied.

(14) The exemplifying dishwasher 1 comprises a washing compartment or tub 2, a door 4 configured to close and seal the washing compartment 2, a spraying system having a lower spray arm 3 and an upper spray arm 5, a lower rack 6 and an upper rack 7. Additionally, it may comprise a specific top rack for cutlery (not shown). A controller 11 such as a microprocessor is arranged in the interior of the dishwasher for controlling washing programmes and is communicatively connected to an interface 8 via which a user can select washing programmes.

(15) The door 4 of the prior art dishwasher 1 illustrated in FIG. 1 is further on its inside arranged with a small detergent dispenser 9 having a lid 10 being controllably opened and closed by the controller 11 for dispensing detergent from the dispenser 9 into the tub 2.

(16) FIG. 2 schematically illustrates a cross-sectional view of the dishwasher 1 of FIG. 1 taken along section II, to further illustrate components included in a dishwasher 1. Hence, as previously mentioned, the dishwasher 1 comprises a washing compartment or tub 2 housing an upper basket 7 and a lower basket 6 for accommodating goods to be washed such as cutlery, plates, drinking-glasses, trays, etc.

(17) Detergent in the form of liquid, powder or tablets is dosed in a detergent compartment located on the inside of a door (not shown in FIG. 2) of the dishwasher 1 by a user, which detergent is controllably discharged into the washing compartment 2 in accordance with a selected washing programme. As previously mentioned, the operation of the dishwasher 1 is typically controlled by the controller 11 executing appropriate software 12 stored in a memory 13.

(18) Fresh water is supplied to the washing compartment 2 via water inlet 15 and water supply valve 16. This fresh water is eventually collected in a so called sump 17, where the fresh water is mixed with the discharged detergent resulting in process water 18. The opening and closing of the water supply vale 16 is typically controlled by the controller 11.

(19) By the expression “process water” as used herein, is meant a liquid containing mainly water that is used in and circulates in a dishwasher. The process water is water that may contain detergent and/or rinse aid in a varying amount. The process water may also contain soil, such as food debris or other types of solid particles, as well as dissolved liquids or compounds. Process water used in a main wash cycle is sometimes referred to as the wash liquid. Process water used in a rinse cycle is sometimes referred to as cold rinse or hot rinse depending on the temperature in the rinse cycle. The pressurized fluid supplied to the detergent dispensing device according to embodiments of the invention thus at least partly contains process water.

(20) At the bottom of the washing compartment is a filter 19 for filtering soil from the process water before the process water leaves the compartment via process water outlet 20 for subsequent re-entry into the washing compartment 2 through circulation pump 21. Thus, the process water 18 passes the filter 19 and is pumped through the circulation pump 21, which typically is driven by a brushless direct current (BLDC) motor 22, via a duct 23 and process water valve 24 and sprayed into the washing compartment 2 via nozzles (not shown) of a respective wash arm 3, 5 associated with each basket 6, 7. Thus, the process water 18 exits the washing compartment 2 via the filter 19 and is recirculated via the circulation pump 21 and sprayed onto the goods to be washed accommodated in the respective basket via nozzles of the wash arms 3, 5. Further, a controllable heater 14 is typically arranged in the sump 17 for heating the process water 18.

(21) The washing compartment 2 of the dishwasher 1 is drained on process water 18 with a drain pump 29 driven by a BLDC motor 30. It should be noted that it can be envisaged that the drain pump 29 and the circulation pump 21 may be driven by one and the same motor.

(22) In an embodiment of the invention, a sensing arrangement 25 is arranged at the circulation pump 21 for measuring torque of the circulation pump 21, in the form of e.g. operating current, voltage or power. The sensing arrangement 25 may be implemented in the form of a resistor arranged at the circulation pump motor 22 for measuring operation current of the motor. Practically, this is undertaken by measuring the operating voltage of a known shunt resistor in the motor 22 of the circulation pump 21 and calculating the operating current.

(23) Measured pump operating current can directly be translated into circulation pump torque for a given circulation pump speed; the higher the torque, the higher the operating current of the motor 22 driving the pump 21, and a higher pump torque implies a greater flow of process water 18 through the circulation pump while a lower torque indicates a smaller flow of process water 18 through the circulation pump 21.

(24) It should be noted that a torque sensor (not shown) may be used for directly measuring circulation pump torque instead of indirectly measuring the torque via an electrical property.

(25) FIG. 3a shows a view of an exemplifying circulation pump 21. The speed of the circulation pump 21 is typically controlled by the controller 11. FIG. 3a shows an outlet 40 (referred to as a discharge port) of the circulation pump 21 and an inlet 41. The casing 42 of the circulation pump 21 is referred to as the volute and can be removed from a main body 43 of the circulation pump 21.

(26) FIG. 3b shows a further view of the circulation pump 21 of FIG. 3a, where the volute 42 has been removed from the main body 43 of the circulation pump, thereby revealing the impeller 44 of the circulation pump which under operation pumps the process water that is entering the circulation pump 21 via the inlet 41. The process water that is pumped by the impeller 44 is subsequently received by the volute 42, which slows down the flow rate of the process water, and exits the circulation pump 21 via the outlet 40.

(27) FIG. 4 illustrates fluctuations in circulation pump operating current over time, i.e. the operating current being a property indicating torque of the circulation pump 21. As can be seen, the operating current fluctuates around a nominal pump operating current I.sub.nom. FIG. 4 illustrates seven measured current values from t.sub.1 to t.sub.7. The measured current at each instant of time t.sub.n will be denoted I(t.sub.n).

(28) With reference to the art, in case e.g. ΔI=I(t.sub.1)−I(t.sub.2) exceeds a predetermined threshold value ΔI.sub.T, it may be concluded that more water should be supplied to the dishwasher 1, since the torque of the circulation pump 21 is indicated to having decreased to a level I(t.sub.2) where a water fill is required. As will be described in the following with reference to FIG. 4, this may be a result of a temporary fluctuation in pump current which in fact do not indicate a need for activation of water fill.

(29) In an embodiment of the present invention, where reference further will be made to the flowchart of FIG. 5, a property is measured indicating torque of the circulation pump 21 in step S101, in this case operating current of the pump.

(30) In a second step S102, a first set S1 of measured current values is averaged, thereby creating a first average current value, Ī.sub.S1. This could be undertaken in different ways depending on the particular application, for instance by calculating an arithmetic mean or a moving average.

(31) In this particular exemplifying embodiment, an arithmetic mean is calculated as:

(32) ${\overline{I}}_{S 1} = \frac{I (t_{1}) + I (t_{2}) + I (t_{3}) + I (t_{4})}{4}$

(33) In the illustration of FIG. 4, it can be concluded that Ī.sub.S1≈I.sub.nom.

(34) In a third step S103, a second set S2 of measured current values is averaged, thereby creating a second average current value, Ī.sub.S2:

(35) ${\overline{I}}_{S 2} = \frac{I (t_{4}) + I (t_{5}) + I (t_{6}) + I (t_{7})}{4}$

(36) Again with reference to the illustration of FIG. 4, it can be concluded that Ī.sub.S2≈I.sub.nom.

(37) In this example, the two sets S1 and S2 comprise one overlapping measured current value I(t.sub.4). It can be envisaged that further measured current values are common to the two sets S1 and S2, or that no overlap occurs at all.

(38) In step S104, the first average current Ī.sub.S1 is compared to the second average current Ī.sub.S2, and from the comparison it is detected in step S105 whether a change in process water flow of the circulation pump 21 has occurred based on a difference between the first average Ī.sub.S1 and the second average Ī.sub.S2.

(39) In this exemplifying embodiment, the first average current Ī.sub.S1 and the second average current Ī.sub.S2 are substantially equal, and accordingly no change in process water flow is detected.

(40) FIG. 6 illustrates another scenario, where initially, for the first set S1 of measured operating current values consisting of I(t.sub.1), I(t.sub.2), I(t.sub.3) and I(t.sub.4), it again can be concluded that Ī.sub.S1≈I.sub.nom.

(41) However, for the second set S2 of measured operating current values consisting of I(t.sub.4), I(t.sub.5), I(t.sub.6) and I(t.sub.7), it can be seen that the average current Ī.sub.S2 is substantially lower, thereby reflecting a “true” decrease in pump torque (as indicated by the decreasing pump current), and thus process water flow through the circulation pump.

(42) Hence, with reference to the flowchart of FIG. 7, the operating current I of the circulation pump is measured in step S101 and a first and second average Ī.sub.S1, Ī.sub.S2 is created in steps S102 and S103, respectively.

(43) In this particular embodiment, the comparing of the first average Ī.sub.S1 with the second average Ī.sub.S2 comprises calculating a difference between the first average and the at least one second average as ΔI=Ī.sub.S1−Ī.sub.S2, and determining whether the difference exceeds a predetermined current threshold value ΔI.sub.T:
ΔI=Ī.sub.S1−S.sub.S2≥ΔI.sub.T.

(44) If so, a decrease in pump torque is detected, and it is concluded in step S105 that a decrease in process water flow through the circulation pump indeed has occurred. A possible action to be taken by the processor 11 may be to control the valve 15 of the inlet 16 to supply additional water to the dishwasher 1.

(45) FIG. 8 illustrates the scenario of FIG. 6, but where a third set S3 of measured operating current values is taken into account for detecting process water flow change of the circulation pump.

(46) Hence, with reference to the flowchart of FIG. 9, the operating current I of the circulation pump is measured in step S101 and a first average Ī.sub.S1 is created in step S102.

(47) Further, in this embodiment, a plurality of sets of current values are averaged in step S103, in this example a second set S2 and a third set S3, the third set S3 consisting of measured current values I(t.sub.7), I(t.sub.8), I(t.sub.9) and I(t.sub.10).

(48) For the third set S3 of measured operating current values, it can be seen that the average current Ī.sub.S3 is substantially lower as compared to Ī.sub.S1 (and even as compared to Ī.sub.S2), thereby even more strongly reflecting a true decrease in pump torque (as indicated by the decreasing pump current), and thus process water flow through the circulation pump, when compared to the embodiment described with reference to FIGS. 6 and 7.

(49) In this particular embodiment, the comparing in step S104 of the first average Ī.sub.S1 with the second average Ī.sub.S2 comprises calculating a difference between the first average and the second average as ΔI.sub.1=Ī.sub.S1−Ī.sub.S2, and determining whether the difference exceeds a first predetermined current threshold value ΔI.sub.T1:
ΔI.sub.1=Ī.sub.S1−Ī.sub.S2≥ΔI.sub.T1.

(50) Further in step S104, the first average Ī.sub.S1 is compared with the third average Ī.sub.S3 by calculating a difference between the first average and the third average as ΔI.sub.2=Ī.sub.S1−Ī.sub.S3, and determining whether the difference exceeds a second predetermined current threshold value ΔI.sub.T2:
ΔI.sub.2=Ī.sub.S1−Ī.sub.S3≥ΔI.sub.T2.

(51) If both of theses conditions are fulfilled, a decrease in pump torque is detected, and it is concluded in step S105 that a decrease in process water flow through the circulation pump indeed has occurred. Again, a possible action to be taken by the processor 11 may be to control the valve 15 of the inlet 16 to supply additional water to the dishwasher 1.

(52) Hence, in this particular example, if both averages Ī.sub.S2, Ī.sub.S3 differ from Ī.sub.S1 to a certain extent, a change is detected. In practice, averages of even further sets of measured current values may have to fulfil corresponding threshold conditions for a detection of flow rate change to occur.

(53) With reference to FIG. 10, it should be noted that the average current Ī.sub.S3 of the third set S3 not necessarily must be lower than that of the second set S2.

(54) In FIG. 10, the third average Ī.sub.S3 is about the same as the second average Ī.sub.S2, which thus indicates that a true decrease in pump torque has occurred.

(55) It may thus suffice in the comparing step S104 that
ΔI.sub.1=Ī.sub.S1−Ī.sub.S2≥ΔI.sub.T and ΔI.sub.2=Ī.sub.S1−Ī.sub.S3≥ΔI.sub.T,
i.e. that both differences in average current ΔI.sub.1, ΔI.sub.2 exceeds the same predetermined threshold value ΔI.sub.T1, for a decrease in flow should be detected in step S105. Again, if both averages Ī.sub.S2, Ī.sub.S3 differ from Ī.sub.S1 to a certain extent based on the threshold value SIT, a change is detected.

(56) The figures illustrate decrease in process water flow, but an increase in process water flow would be detected analogously, with an increasing average pump current when comparing the first set S1 with at least one further set S2.

(57) In practice, the steps of the method performed by the dishwasher 1 according to embodiments of the invention, is caused by the controller 11 embodied in the form of one or more microprocessors or processing units arranged to execute a computer program 12 downloaded to a suitable storage medium 13 associated with the microprocessor, such as a Random Access Memory (RAM), a Flash memory or a hard disk drive. The controller 11 is arranged to cause the dishwasher 1 to carry out at the steps of the method according to embodiments of the present invention when the appropriate computer program 12 comprising computer-executable instructions is downloaded to the storage medium 13 and executed by the controller 11. The storage medium 13 may also be a computer program product comprising the computer program 12. Alternatively, the computer program 12 may be transferred to the storage medium 13 by means of a suitable computer program product, such as a Digital Versatile Disc (DVD) or a memory stick. As a further alternative, the computer program 12 may be downloaded to the storage medium 13 over a network. The controller 11 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), etc.

(58) The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Process water flow detection in circulation pump

Assignee

Inventors

Cpc classification

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D06F2103/14

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D06F2103/48

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A47L2501/03

HUMAN NECESSITIES

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A47L15/4244

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A47L15/0049

HUMAN NECESSITIES

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A47L2401/08

HUMAN NECESSITIES

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D06F39/085

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D06F33/36

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A47L2501/01

HUMAN NECESSITIES

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A47L15/00

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A47L15/42

HUMAN NECESSITIES

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D06F39/08

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D06F33/00

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Abstract

Claims

Description