Method for operating a washing device having a piston pump for dosing detergent, and washing device suitable therefor

Abstract

The invention relates to a method for operating a washing machine comprising a tub, a drum rotatably mounted therein about a rotational axis for receiving laundry items, a control unit, and a piston pump driven by an electric drive motor and performing an oscillating piston movement, which dispenses a detergent, wherein the piston movement has at least one activation phase with a duration Tstroke, consisting of a suction and an ejection phase, the activation phase of the piston pump being an integer multiple of the duration Tstroke. The invention also relates to a washing machine suitable for carrying out this method.

Description

[0001] The invention relates to a method for operating a washing machine with a piston pump for detergent dosing and to a washing machine suitable for this purpose. The invention particularly relates to a method for operating a washing machine comprising a tub, a drum rotatably mounted therein about an axis of rotation for receiving laundry items, a control unit, and a piston pump driven by an electric drive motor and performing an oscillating piston movement, which doses a detergent, wherein the piston movement has at least one activation phase with a duration T stroke, consisting of a suction phase and an ejection phase.

[0002] The use of piston pumps for dosing detergents is known per se. This generally involves sensorless, time-controlled operation, which typically results in poor dosing reproducibility due to the piston pump's non-uniform dosing. The oscillating piston motion generates a discontinuous flow rate, which can be described by the system's kinematics and generally exhibits a sinusoidal waveform during the piston's extension phase. In the prior art's time-controlled system, it is assumed that the flow rate corresponds to a constant average nominal flow rate, meaning that the dosed volume changes linearly over time. The operating time of the piston pump, also referred to here as the metering pump, then corresponds to the quotient of the nominal dosing quantity and the nominal flow rate.This known operating mode of a metering pump generally results in an absolute error, a so-called metering error. The metering error is the difference between the target metering quantity and the actual metered quantity. Depending on the piston's starting position, the metering error can be slightly more than half the stroke volume (Vstroke), a characteristic parameter of the piston pump. The stroke volume for commercially available piston pumps is typically 2 to 4 ml, so the relative error is large at low metering quantities. The starting position is unknown because the piston pump operates solely on a timer without sensors. Another parameter of the piston pump is the metering duration (Tstroke), which is calculated by adding the generally equal durations of a suction phase and a discharge phase.

[0003] Against this background, the object of the present invention was to provide an improved method for operating a washing machine with a metering pump for dosing a detergent. Preferably, the dosing should be cost-effective and possible using a commercially available piston pump. An object of the invention was also to provide a washing machine suitable for carrying out this method.

[0004] The solution to this problem is achieved according to this invention by a method for operating a washing machine with a metering pump for dosing a detergent, and by a washing machine suitable for carrying out this method, having the features of the respective independent claims. Preferred embodiments of the method according to the invention are listed in the dependent claims, wherein preferred embodiments of the method according to the invention correspond to preferred embodiments of the washing machine according to the invention, even if this is not explicitly mentioned therein.

[0005] The invention therefore relates to a method for operating a washing machine comprising a tub, a drum rotatably mounted therein about an axis of rotation for receiving laundry items, a control unit, and a piston pump driven by an electric drive motor and performing an oscillating piston movement, which dispenses a detergent, wherein the piston movement has at least one activation phase with a duration T stroke, consisting of a suction and an ejection phase, the activation phase of the piston pump being an integer multiple of the duration T stroke. The piston pump is also referred to herein as a metering pump.

[0006] In principle, liquid detergents can be used in the method according to the invention.

[0007] Furthermore, it is preferred that the stroke volume of the piston pump is in the range of 1 to 5 ml, preferably in the range of 2 to 4 ml.

[0008] Furthermore, according to the invention, a method is preferred in which the integer multiple is a multiple of 1 to 50 times.

[0009] Preferably, during the ejection phase, the amount of detergent ejected by the piston pump describes a sine curve as a function of time.

[0010] The drive motor for the piston pump is preferably a continuously running single-phase AC synchronous motor.

[0011] In the method according to the invention, it is preferred that a rotary movement of the drive motor is converted into a translational movement of a piston of the metering pump via an eccentric. It is preferred that a pin of the eccentric runs in a slot located on an extension of the piston.

[0012] If, as provided for in the invention, only integer multiples of the duration T stroke are permitted for the actuation time, the error caused by the kinematics becomes zero, since a full stroke volume V stroke is always dosed. Although such a method quantizes the dosed quantity, it significantly improves the repeatability of the dosing. Thus, the washing performance becomes more reproducible.

[0013] The invention also relates to a washing machine comprising a tub, a drum rotatably mounted therein about an axis of rotation for receiving laundry items, a control unit and a piston pump operated by an electric drive motor for dosing detergent, which is configured to perform an oscillating piston movement, wherein the piston movement has at least one start-up phase with a duration T stroke, and wherein the control unit is configured to operate the piston pump such that the start-up phase of the piston pump is an integer multiple of the duration T stroke.

[0014] The washing appliance is generally a washing machine or a washer-dryer. It generally has a drum rotatably mounted in a tub for holding laundry, as well as a water supply device. The latter can, for example, be a valve-controlled fresh water connection, the valve preferably being controllable by the control unit.

[0015] The invention has several advantages. It enables increased reproducibility of detergent dosing, thereby improving the reproducibility of washing performance. Furthermore, this can be achieved cost-effectively according to the invention, as it allows the use of a commercially available dosing pump.

[0016] The invention is described below with reference to the Figures 1 to 3 illustrated. Fig. 1shows a comparison of a previous dosing method with a dosing method according to the invention as used in the process according to the invention. Fig. 2 shows for numerous test runs of a dosing pump, the dosed volume in each case. Fig. 3 shows similar to Fig. 2 for numerous test runs of a dosing pump in contrast to Fig. 2 the respective relative dosage weight in relation to the target volume.

[0017] Fig. 1Figure 1 shows a comparison of a previous dosing method with a dosing method according to the invention, as used in the inventive process. The figures show the volumes pumped during a stroke time T of the piston pump, which here consists of a 1.5-second intake phase and a 1.5-second discharge phase. Curve 1 represents the target volume, curve 2 the actual volume, i.e., the actual volume of detergent pumped (in this case, a liquid detergent), and curve 3 a dosing error.

[0018] The oscillating piston movement of the piston pump generates a discontinuous volume flow, which can be described by the kinematics of the system and has a sinusoidal profile during the piston's ejection phase, see curve 2.

[0019] In the time-based control system commonly used in the prior art, it is assumed that the volume flow rate corresponds to a mean, constant nominal volume flow rate. This means that the metered volume changes linearly with time, as is the case in Fig. 1 This is represented by curve 1. The pump's on-time then corresponds to the quotient of the nominal dosing quantity and the nominal flow rate.

[0020] In Fig. 1 The curves are shown only for a single duration T stroke. According to the invention, however, the start-up phase of the piston pump is an integer multiple of the duration T stroke.

[0021] If the switching-on time of the piston pump does not correspond to an integer multiple of the duration T stroke, i.e., the time for one complete reciprocating movement of the piston, as provided for in the invention, an absolute error results, which is referred to herein as the metering error and in the Fig. 1This is illustrated by curve 3. Depending on the piston's starting position, the dosing error can be slightly more than half the stroke volume V. The stroke volume for commercially available piston pumps is typically 2 to 4 ml, so the relative error is large for small doses. The starting position is unknown because the pump operates solely on a timer without sensors. However, if, as provided for in the invention, only integer multiples of the dosing duration T are specified for the piston pump's actuation time, the dosing error becomes zero, since a full stroke volume is always dosed.

[0022] Fig. 2The graph shows the dosed volume for numerous test runs of a dosing pump, where on the one hand the dosing took place over a duration corresponding to an integer multiple of T stroke (IMD = integer multiple dosing, represented by filled circles), and on the other hand over a duration corresponding to a non-integer multiple of T stroke, namely here 2 / 3 of T stroke (non-IMD = non-integer multiple dosing, represented by filled triangles).

[0023] Fig. 2 This illustrates that when dosing over a duration corresponding to an integer multiple of T stroke, the dosage hardly fluctuates, meaning there is only an extremely small dosing error.

[0024] Fig. 3 shows similar to Fig. 2 for numerous test runs of a dosing pump in contrast to Fig. 2the respective relative dosage weight in relation to the target volume, whereby on the one hand the dosage was administered over a duration corresponding to an integer multiple of T stroke (IMD = integer multiple dosing, represented by filled circles), and on the other hand over a duration corresponding to a non-integer multiple of T stroke, namely here 2 / 3 of T stroke (non-IMD = non-integer multiple dosing, represented by filled triangles).

[0025] Fig. 3 This also illustrates that when dosing over a duration corresponding to an integer multiple of T stroke, the dosage hardly fluctuates, meaning there is only an extremely small dosing error. Reference symbol list

[0026] 1 Target volume 2 Actual volume 3 Dosing error

Claims

1. Method for operating a washing machine comprising a tub, a drum rotatably mounted therein about an axis of rotation for receiving laundry items, a control unit and a piston pump operated by an electric drive motor and performing an oscillating piston movement, which doses a detergent, wherein the piston movement includes at least one start-up phase with a duration T stroke features a suction phase and an ejection phase, characterized by the fact that The start-up phase of the piston pump is an integer multiple of the duration T. stroke is.

2. Method according to claim 1, characterized by the fact that The detergent is a liquid detergent.

3. Method according to claim 1 or 2, characterized by the fact that a stroke volume of the piston pump is in the range of 1 to 5 ml, preferably in the range of 2 to 4 ml.

4. Method according to any one of claims 1 to 3, characterized by the fact that the integer multiple is a multiple of 1 to 50 times.

5. Method according to any one of claims 1 to 4, characterized by the fact that During the ejection phase, the amount of detergent ejected describes a sine curve as a function of time.

6. Method according to any one of claims 1 to 5, characterized by the fact that The drive motor for the piston pump is a continuously running single-phase AC synchronous motor.

7. Method according to any one of claims 1 to 6, characterized by the fact that A conversion of the rotary motion of the drive motor into a translational motion of a piston of the metering pump takes place via an eccentric.

8. Method according to claim 7, characterized by the fact that A pin of the eccentric runs in a slot located on an extension of the piston.

9. Washing machine comprising a tub, a drum rotatably mounted therein about an axis of rotation for receiving laundry items, a control unit and a piston pump operated by an electric drive motor for dosing detergent, the pump being configured to perform an oscillating piston movement, wherein the piston movement includes at least one start-up phase with a duration T stroke exhibits, and wherein the control unit is configured to operate the piston pump such that the switching-on phase of the piston pump is an integer multiple of the duration T stroke is.

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