Method for operating a pump

Abstract

A pump of a dishwasher has an integrated heating element, a pump chamber with an inlet and an outlet, a pump rotor inside the pump chamber and a drive motor, wherein the heating element and a temperature sensor are provided on a wall of the pump chamber. For measuring a calcification of the pump chamber it is filled with water and then the pump rotor rotates for mixing the water in the pump chamber without transporting water out of the pump chamber. The temperature of the water in the pump chamber is measured with the temperature sensor as a starting temperature, and then the heating element is activated to heat the water in the pump chamber while the temperature of the water in the pump chamber is measured. Then the heating element is deactivated and the maximum temperature of the water during the heating duration or directly afterwards is determined. A temperature relation between the maximum temperature and the starting temperature of the water is calculated. These steps are executed in the pump at the very beginning of an operation of the new dishwasher after its installation for determining an initial temperature relation. These steps are automatically executed again at a later stage for determining a later temperature relation to determine the heating efficiency of the pump by comparing the later temperature relation to the initial temperature relation.

Claims

1. A method for operating a pump with an integrated heating element, wherein said pump comprises: a pump chamber with an inlet into said pump chamber and with an outlet out of said pump chamber and with a wall, a pump rotor inside said pump chamber, a drive motor for said pump rotor, a heating element being provided on at least a part of said wall of said pump chamber, and a temperature sensor for sensing a temperature of water in said pump chamber, the method comprising the steps of: A providing water in said pump chamber, B rotating said pump rotor for mixing said water in said pump chamber without transporting water out of said pump chamber, C measuring a temperature of said water in said pump chamber with said temperature sensor as a starting temperature, D activating said heating element to heat said water in said pump chamber after measuring said temperature of said water, E measuring said temperature of said water in said pump chamber with said temperature sensor, F deactivating said heating element and determining a maximum temperature of said water during a heating duration of step D or within a maximum of 10 sec after a heating duration of step D, and G calculating a temperature relation between said maximum temperature and said starting temperature of the water, wherein: said steps A to G are executed in said pump at a beginning of an operation of said pump or at one of first 50 operating cycles of said pump for determining an initial temperature relation, said steps A to G are executed again at a later stage for determining a later temperature relation to determine a heating efficiency of said pump by comparing said later temperature relation to said initial temperature relation, and said water in said pump chamber is heated up to a maximum temperature of no more than 80° C.

2. The method according to claim 1, wherein a predefined amount of water is provided in said pump chamber in step A.

3. The method according to claim 1, wherein said heating element to heat said water in said pump chamber after measuring said temperature of said water is activated for a predefined heating duration in step D.

4. The method according to claim 3, wherein said heating element is deactivated in step F after said predefined heating duration in step D.

5. The method according to claim 1, wherein said temperature relation is a temperature difference such that said starting temperature of said water is subtracted from said maximum temperature of said water, wherein said heating efficiency of said pump is determined to be reduced if said initial temperature difference is larger than said later temperature difference.

6. The method according to claim 5, wherein in case that said later temperature difference is less than 90% of said initial temperature difference, a signal prompting a user to start a de-calcification process of said pump is generated or an automatic de-calcification process of said pump is started.

7. A method for operating a pump with an integrated heating element, wherein said pump comprises: a pump chamber with an inlet into said pump chamber and with an outlet out of said pump chamber and with a wall, a pump rotor inside said pump chamber, a drive motor for said pump rotor, a heating element being provided on at least a part of said wall of said pump chamber, and a temperature sensor for sensing a temperature of water in said pump chamber, the method comprising the steps of: A providing water in said pump chamber, B rotating said pump rotor for mixing said water in said pump chamber without transporting water out of said pump chamber, C measuring a temperature of said water in said pump chamber with said temperature sensor as a starting temperature, D activating said heating element to heat said water in said pump chamber after measuring said temperature of said water, E measuring said temperature of said water in said pump chamber with said temperature sensor, F deactivating said heating element and determining a maximum temperature of said water during a heating duration of step D or within a maximum of 10 sec after a heating duration of step D, and G calculating a temperature relation between said maximum temperature and said starting temperature of the water, wherein: said steps A to G are executed in said pump at a beginning of an operation of said pump or at one of first 50 operating cycles of said pump for determining an initial temperature relation, said steps A to G are executed again at a later stage for determining a later temperature relation to determine a heating efficiency of said pump by comparing said later temperature relation to said initial temperature relation, said temperature relation is a temperature difference such that said starting temperature of said water is subtracted from said maximum temperature of said water, wherein said heating efficiency of said pump is determined to be reduced if said initial, in case that said later temperature difference is less than 90% of said initial temperature difference, a signal prompting a user to start a de-calcification process of said pump is generated or an automatic de-calcification process of said pump is started, and in step B said rotational speed of said pump rotor is less than 500 rpm.

8. The method according to claim 1, wherein when comparing said later temperature relation to said initial temperature relation, said heating efficiency is determined to be reduced if said initial temperature relation is different from said later temperature relation.

9. The method according to claim 1, wherein said steps A to G are repeated consecutively at least two or three times to find a median temperature relation from each of said determined temperature relation.

10. The method according to claim 1, wherein said method is repeated in regular manner.

11. The method according to claim 10, wherein said method is repeated in regular manner at a number of operating cycles of an electrical appliance in which said pump is provided, wherein said number of said operating cycles between each regular repeating is between 5 and 100.

12. The method according to claim 3, wherein said predefined heating duration is between 10 sec and 60 sec.

13. The method according to claim 12, wherein said predefined heating duration is between 20 sec and 30 sec.

14. The method according to claim 1, wherein an operating voltage of said heating element is monitored and a correction factor is adapted to variations of said operating voltage, wherein said correction factor is taken into account when determining said temperature relation.

15. The method according to claim 14, wherein said correction factor is taken into account when determining said temperature relation such that said temperature relation is independent from said operating voltage or its variation, respectively.

16. The method according to claim 14, wherein a drive voltage in a drive circuit for said drive motor corresponds to said operating voltage of said heating element and wherein said drive voltage is measured.

17. The method according to claim 1, wherein said heating element is a PTC heating element with a PTC effect of its resistance behaviour.

18. The method according to claim 1, wherein said temperature sensor is an NTC temperature sensor with an NTC effect of its resistance behaviour.

19. The method according to claim 1, wherein said pump is provided with an axial inlet into said pump chamber.

20. The method according to claim 19, wherein said outlet out of said pump chamber is to a side or parallel to a radial direction of said pump chamber.

21. The method according to claim 1, wherein said water in said pump chamber is heated up to a maximum temperature of no more than 65° C.

22. The method according to claim 7, wherein in step B said rotational speed of said pump rotor is from 10 rpm to 300 rpm.

23. A method for operating a pump with an integrated heating element, wherein said pump comprises: a pump chamber with an inlet into said pump chamber and with an outlet out of said pump chamber and with a wall, a pump rotor inside said pump chamber, a drive motor for said pump rotor, a heating element being provided on at least a part of said wall of said pump chamber, and a temperature sensor for sensing a temperature of water in said pump chamber, the method comprising the steps of: A providing water in said pump chamber, B rotating said pump rotor for mixing said water in said pump chamber without transporting water out of said pump chamber, C measuring a temperature of said water in said pump chamber with said temperature sensor as a starting temperature, D activating said heating element to heat said water in said pump chamber after measuring said temperature of said water, E measuring said temperature of said water in said pump chamber with said temperature sensor, F deactivating said heating element and determining a maximum temperature of said water during a heating duration of step D or within a maximum of 10 sec after a heating duration of step D, and G calculating a temperature relation between said maximum temperature and said starting temperature of the water, wherein: said steps A to G are executed in said pump at a beginning of an operation of said pump or at one of first 50 operating cycles of said pump for determining an initial temperature relation, said steps A to G are executed again at a later stage for determining a later temperature relation to determine a heating efficiency of said pump by comparing said later temperature relation to said initial temperature relation, an operating voltage of said heating element is monitored and a correction factor is adapted to variations of said operating voltage, wherein said correction factor is taken into account when determining said temperature relation, and a drive voltage in a drive circuit for said drive motor corresponds to said operating voltage of said heating element and wherein said drive voltage is measured.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are schematically illustrated in the drawings and will be explained in more detail below. In the drawings:

(2) FIG. 1 shows a schematic view of a dishwasher in which the method according to the invention is implemented by a control unit,

(3) FIG. 2 shows a schematic view of a pump of the dishwasher of FIG. 1,

(4) FIG. 3 shows a diagram for the temperature over time, which temperature a temperature sensor on the pump of FIG. 2 has measured and

(5) FIG. 4 shows the drive voltage of the drive motor with a temporary cutback due to the activation of the heating element.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(6) In FIG. 1 a dishwasher for performing the method according to the invention is shown in schematic manner. The dishwasher 11 is basically as is known in the art with a washing chamber 12 which can be accessed via a door 13. In the washing chamber 12 two baskets 14 for example are arranged one above the other for receiving dishes to be cleaned. Above the upper basket 14 a schematic jet arm 16 is provided which rotates and which has a number of small jet openings on the underside directed towards the baskets 14. Water is pumped to the jet arm 16 via a delivery pipe 17. Preferably more than only one jet arm is provided in the washing chamber 12, which for easier understanding of FIG. 1 has been left out.

(7) On the bottom of the washing chamber 12 a so-called sump 19 is provided from which a drain pipe 20 leads water to a pump 22 according to the invention. Pump 22 is shown in more detail in FIG. 2 and described with reference to FIG. 2.

(8) A control unit 15 of the dishwasher 11 is provided which is connected to the pump 22 as is shown in FIG. 1. This connection is meant to be schematic and of course, in practice, is rather different. It is clear from FIG. 1 that pump 22, which is a so-called motor heat pump to pump water while heating it, can circulate water from the washing chamber 12 via the sump 19 and the drain pipe 20 back into the washing chamber via the delivery pipe 17 and the jet arm 16.

(9) FIG. 2 shows a schematic view of the pump 22 in more detail. It is explicitly referred to U.S. Pat. No. 9,470,242 B for further details. Pump 22 has a pump housing 23 in which a pump chamber 24 is provided, preferably round-circular. The pump chamber 24 has an outer lateral pump chamber wall 25. An inlet 26, that is connected to the drain pipe 20, leads into the pump housing 23 and into the pump chamber 24. An outlet 27 connected to the delivery pipe 17 leads out of the pump chamber 24.

(10) Inside the pump chamber 24, a pump rotor 30 is provided which rotates when driven by the drive motor 32. The rotating pump rotor 30, in practice rotating with about 3,000 to 6,000 rpm, sucks in water through the inlet 26 with axial direction. This water is then ejected in radial direction so that it circulates for several times inside the pump chamber 24 around the pump rotor 30 until it leaves the pump chamber 24 via the outlet 27. This is known very well in the art.

(11) The drive motor 32 is powered or provided with electrical power, respectively, by the drive circuit 33. The drive circuit 33 is connected to a drive voltage Ud, preferably the mains voltage. The drive circuit 33 is connected to or controlled by the control unit 15. This allows for controlling the power and, in particular, the speed of the drive motor 32 and, consequently, of the pump rotor 30. It is also possible and preferred to measure the drive voltage Ud in the drive circuit 33 to provide this information to the control unit 15.

(12) On the outside of the pump chamber wall 25 a heating element 35 is provided. Such is known in the art and can be taken, for example, from U.S. Pat. No. 9,470,242 B. The heating element 35 may be provided as a thick film heating element, alternatively as an electrical heating element in different realization. The heating element 35 is provided with a heating element connection 36. This is connected to a switch circuit which is not shown here to operate the heating element 35 with the drive voltage Ud. In a preferred embodiment of the invention, the heating element 35 is operated in a kind of pulsed mode or in a pulse width modulation mode, which means that the heating element 35 is either fully powered with the drive voltage Ud or is switched off.

(13) The heating element 35 has PTC properties of its resistance. This means that the resistance of the heating element rises if the temperature rises. This leads to a temperature of the heating element 35 above the intended operating temperature, which via the PTC effect of its resistance leads to a higher resistance and a smaller heating power output. This smaller or reduced heating power output leads to the maximum temperature of the water after the heating duration being lower than the maximum temperature if the heat generated by the heating element 35 could be better transported into the water in the pump chamber 25 without calcification on the inside of pump chamber wall 25.

(14) In other words, the strong calcification of the inside of the pump chamber wall 25 has a negative impact onto the heat transfer from the heating element 35 into the water through the pump chamber wall 25 so that it is lower. This leads to a higher temperature of the heating element 35 which due to the PTC effect results in the resistance becoming higher. This higher resistance again leads in view of a fixed operating voltage to the heating power output becoming smaller. This together with the reduced heat transfer into the water leads to the maximum temperature of the water being reduced after the same time or heating duration, respectively. Such a calcification 28 is depicted in FIG. 2, although the thickness is grossly exaggerated here. In practice, such a calcification may have a thickness of between 100 μm and 1 mm or even more than 1 mm.

(15) On the outside of the pump chamber wall 25, preferably with a slight distance to the heating element 35, a temperature sensor 39 is provided. Temperature sensor 39 is provided in good heat-conducting manner to the pump chamber wall 25 to exactly measure its temperature. Basically, the temperature sensor 39 is provided to measure the temperature of the water inside the pump chamber 24 and on the inside of the pump chamber wall 25. The temperature sensor 39 is an NTC temperature sensor. It has sensor connections 40, which preferably are connected to the control unit 15. Further temperature sensors like the temperature sensor 39 could be provided on the pump chamber 24 or the pump chamber wall 25, respectively.

(16) In the method according to the invention the basic operation for measuring a temperature is to operate the pump rotor 30 with low power and low speed, for example with 300 rpm. This could be about 5% to 10% of the maximum speed. Such a rather low speed of the pump rotor 30 provides for some water to be sucked into the pump chamber 24 via the drain pipe 20 and the inlet 26. The pump rotor 30 tries to kind of pump the water or transport it via the outlet 27 and the delivery pipe 17. Due to the low rotational speed of the pump rotor 30, the water cannot be transported much higher than the outlet 27, for example only for 3 cm to 5 cm in the vertical direction. Then an equilibrium is established, which by itself is important. This equilibrium serves to have some water inside the pump chamber 24, preferably filling it mostly or totally, wherein this amount of water is not changing and does neither flow through the outlet 27 out of the pump chamber 24 nor through the inlet 26. The water inside the pump chamber 24 is also mixed very well by the rotating pump rotor 30.

(17) The temperature sensor 39 measures the temperature of the water circulating inside the pump chamber 24, in particular of the cold water with a temperature of 24° C. This information is provided to the control unit 15. If this information is present in the control unit 15, the heating element 35 is activated, preferably with its maximum power due to its preferred operation via PWM. Such a heating process can be taken from FIG. 3, wherein the fat line shows a temperature T over time t. At 56 sec after starting, the heating element 35 is activated with its full power. The water inside the pump chamber 24 is being mixed and can, in consequence, absorb the heat generated by the heating element 35 in an optimum way. The temperature sensor 39 can sense the rising temperature according to the fat line in FIG. 3. After 26 sec of heating time, the heating element 35 is switched off again. Some seconds after that, the measured temperature has reached its maximum at 61° C. After this maximum, the temperature declines again.

(18) As the starting temperature of the cold water inside the pump chamber 24 before the heating element 35 has been activated has been measured to amount to 24° C., a temperature difference is 37° C. or 37 K, respectively. This temperature difference is a very simple implementation of a temperature relation mentioned before. The value of 37 K as an initial temperature difference is stored in the control unit 15. This measuring process can be repeated for one or two times to find a median initial temperature difference that does not depend on chance.

(19) If now after several operating cycles of the pump 11 some calcification 28 has formed on the inside of the pump chamber wall 25, and if then the temperature measurement is started again, a course of the temperature T over time is shown in the thin line in FIG. 3. Due to the effect described before, not only less heating energy can be brought into the water in pump chamber 24 through the pump chamber wall 25 via the heating element 35, but the calcification leads to the effect that the heating element 35 itself heats up more than in the case described before without calcification 28, which again leads to a reduced heating power of the heating element 35 due to its PTC behaviour. This leads to the maximum power reached with this heating element 35 or pump 22, respectively, being reduced and that after 26 sec of heating time a maximum temperature of only 57° C. is reached. Such a later temperature difference after several operating cycles of the pump 11 consequently amounts to only 33° C. Furthermore, this maximum temperature is reached even later than in the initial case described before due to the reduced heat conducting behaviour resulting from the increased calcification 28.

(20) So the initial temperature difference has been 37° C., and the later temperature difference is 33° C. If now the difference between these two differences, for example, has reached 5° C., this is a clear sign for the control unit 15 that a calcification 28 is present in the pump chamber 24 and, consequently, the heating efficiency of the pump 22 has been degraded too much. If a temperature difference is too big, a signal can be output to the user to start a de-calcification process, for example by adding some substances into the dishwasher 11 to initiate de-calcification as is known in the art.

(21) Even if in view of FIG. 3 it should not be waited to reach the maximum temperature only after the heating element 35 has been deactivated again, the temperatures at the end of the heating duration could be measured right away and compared to each other.

(22) In a further variation of the embodiment it can be provided that not only one temperature sensor 39 is provided at the pump chamber 24, but two or even three temperature sensors. Such a measurement informing about the difference can thus be made for only one of them or for all of them.

(23) As has been described before, it is preferred to measure the drive voltage Ud at the drive circuit 33, which is also the operating voltage of the heating element 35. This information can be used to correct values of this drive voltage Ud supplying the heating element 35 if it is reduced slightly when turning on the heating element 35. This is shown in FIG. 4.

(24) As has been described before, such a measurement can be repeated several times, for example for three times, to find a median value. Then the water that has been heated up to the temperature according to FIG. 3 is removed from the pump chamber 24 by operating the pump 22 with nominal power. Fresh and cold water can then be sucked in as has been described before and its temperature can be measured again to have a correct starting point for the temperature difference.

(25) FIG. 4 shows the drive voltage of the drive motor 32 with a temporary cutback due to the activation of the heating element 35 in the same time frame as in FIG. 3. This cutback is about 5 V. This cutback can be eliminated mathematically as has been described before. As the drive voltage Ud is also used to power the heating element 35, the heating power is affected also by this cutback. But the control unit 15 can see the drive voltage Ud due to its connection to the drive circuit, so a compensation for this is easy for the control unit 15. The control unit 15 and the drive circuit 33 could be realized in one housing or in one common component even.