EP3114268B1 - Method for determining a loading weight of an oscillating system of a domestic appliance for treating items of laundry, and domestic appliance - Google Patents

Description

The invention relates to a method for determining a loading weight of a vibrating system of a domestic appliance for the care of laundry, in which vibrations of the oscillating system are attenuated by means of at least one shock absorber against a device housing of the household appliance, and wherein by means of a displacement sensor measured values are provided which a displacement indicate the oscillating system with respect to a reference position, and the determination of the loading weight by means of a control device based on the measured values takes place. The invention also relates to a domestic appliance for the care of laundry items, which is designed for carrying out such a method.

It is common in household appliances for the care of laundry, as in particular in washing machines, to detect the movement of the tub relative to the device housing. If the movement of the tub measured, can be deduced on the loading of the laundry drum. On the other hand, depending on the detected movement of the tub and an imbalance of the laundry drum or the entire oscillating system can be detected in the spin mode. It is already state of the art to use for detecting the movement of a tub capacitive sensors which measure the movement of the tub relative to the device housing in a capacitive way. Such a household appliance is for example from the document DE 10 2007 061 525 A1 known. The laundry care device here includes a detection device which serves to detect an operating parameter, namely in particular a water load of a laundry container. The detection device is coupled to a capacitor whose capacitance is correlated with the operating parameter. As a capacitor, a film capacitor is used here, which in contrast to a conventional capacitor has a much smaller space requirement and can be arranged due to its geometric flexibility without much effort in an optimal position within the household appliance. This will improve the detection of the Operating parameters ensured. It may further be provided that one electrode of the film capacitor are fixed in position to a housing of the household appliance and the other electrode or the counter electrode are fixed in position to the tub. In this way, in addition to determining the water load as a function of the geometric arrangement of the two electrodes, the position or the movement of the tub inside the housing can be determined, whereby a total load of the tub and a static and dynamic imbalance can be determined.

Also the document DE 101 04 682 B4 describes a method for measuring the loading and unbalance of the drum of a washing machine, wherein the capacitance curve of a capacitive sensor during a washing process measured and from the movement of the tub is determined. In this case, at least one conductive surface of the sensor is electrically isolated as a capacitive sensor between the tub and the device housing fixed to the housing attached.

In the present case, the interest is directed to the determination of the loading or a loading weight of the washing drum of a washing machine, in particular to the detection of the so-called dry mass of laundry items, which are introduced by the user into the laundry drum. The commonly used method uses the measurement of the movement of the spring-loaded oscillating system with increasing load for determining the mass in the drum. A symmetrical system with a one-dimensional sensor is in this regard, for example, in the document DE 10 2009 028 772 A1 described. Another method which can also be used for asymmetrical systems for determining a loading amount of a laundry treatment appliance is disclosed in the document DE 10 2006 034 190 A1 known. All such measuring systems have in common that the friction dampers used in the washing machine, which are required for vibration damping of the oscillating system, exert a force which counteracts the weight of the drum load and thus falsifies the measurement result. It must therefore be used in the prior art dampers, which are virtually frictionless in static operation. In the DE 102 25 335 B4 Therefore, the use of oil-hydraulic dampers is proposed, but with larger Loading quantities develop a strong non-linear force component and solve the problem of falsified measurement results only partially.

In the DE 10 2010 042 173 A1 It is proposed to continuously determine a mean value of the oscillation amplitude measured at the displacement sensor as the current position of the oscillation system, to store the position determined last, to compare it with the position of a zero position of the oscillating system and to determine therefrom the current rest position of the shock absorber. Thus, it can be determined how far the rest position of the piston of the shock absorber after removal of the currently thrown Wäschepostens - ie at unloaded system - is removed from its theoretical center position, as it alone would have no influence on the load measurement by the displacement sensor. This deviation from the central position is the basis for a measured value correction during the next load measurement.

The use of a displacement sensor for determining the load weight of a washing machine is further from the document DE 10 2004 043 838 B3 known. The evaluation of the measured values of the displacement sensor takes place in such a way that the rest position of the oscillating system is detected and stored with the aid of the displacement sensor, and the control is switched into the active mode when the detected values change. To determine the load weight, the detected rest position of the oscillating system is taken into account. The determination of the rest position thus takes place here in the time in which the control unit is inactive, that is in sleep mode. After activating the control unit, the displacement sensor is read in at least once again, this value read in under load being subtracted from the value for the rest position detected in sleep mode and the result from this calculation being used as weight for the laundry.

Furthermore, it is off DE 10 2008 055 092 A1 a method for predicting an imbalance in a washing machine is known in which jumps of a measurement signal, which are caused due to a change in position of a friction element of a spring piston damper.

It is an object of the invention to provide a solution, as in a method of the type mentioned in the determination of the load weight can be carried out very precisely.

This object is achieved by a method and by a household appliance with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures.

An inventive method is used to determine a loading weight of a vibrating system of a household appliance for the care of laundry. By means of at least one shock absorber - this is designed as a spring piston friction damper - vibrations of the oscillating system are damped against a housing of the household appliance. By means of a displacement sensor, measured values are provided which indicate a displacement of the oscillating system - in particular in the vertical direction of the domestic appliance - with respect to a reference position, ie. a relative position with respect to the reference position. The determination of the loading weight is carried out on the basis of the measured values by means of an electronic control device, which can be designed, for example, as a digital signal processor. According to the invention, during a loading process of the oscillating system-in particular while a user is placing the items of laundry in a laundry drum of the system-a temporal course of the measured values is evaluated by the control device and, based on the chronological progression, slippage of the shock absorber during loading of the oscillating system is detected is, wherein a caused by the slipping change value of the displacement is determined by the control device and compensated in the determination of the loading weight.

The invention is based on the finding that the measurement of the load weight in a domestic appliance for the care of laundry items is adversely affected by slippage of a friction lining of the shock absorber. This slippage can occur in particular during the loading process. Another finding is that slippage of the friction lining of the shock absorber generates a typical course of the measured values of the displacement sensor. This typical waveform can detected during the loading process by the control device and interpreted as slippage of the friction lining. If such slipping is detected, an offset value or a change value of the displacement is simultaneously determined and compensated for in the determination of the loading weight. The force impressed into the system by the shock absorber is fundamentally dependent on the lowering of the oscillating system. The weight of the oscillating system including loading is in equilibrium with the spring forces of a spring assembly and the impressed by the at least one shock absorber forces. By the invention, a change in position is compensated, which results by changing the equilibrium when the at least one shock absorber comes in a non-linear working area and slips. Overall, the invention has the advantage that the total loading weight can be determined very precisely, since the main disturbing influence of the loading amount - namely the nonlinear damping force - is compensated. It can also be used with a lower stiction spring piston damper, which has particular advantages in terms of noise reduction. Accordingly, costly, speed-dependent dampers, such as oil hydraulic dampers, do not need to be used.

The slippage of the shock absorber is detected when a change in the displacement of the oscillating system which is greater than a predetermined limit value is detected based on the time profile of the measured values within a time interval of a predetermined length. This embodiment is based on the recognition that a large change in the position of the oscillating system within a very short time interval can basically only be caused by the slipping of the shock absorber, but not by the introduction of the laundry items in the laundry drum. If the position of the oscillating system changes abruptly within, for example, two milliseconds, it can be assumed that this change in position is due to the slipping friction lining and not to an additional load. Thus, the slippage of the shock absorber can be detected particularly reliable and the load weight can be precisely determined.

In practice, this can also be implemented in such a way that, based on the chronological course of the measured values, a rate of change as a change in the shift per Time unit is determined by the controller. The detection of the slipping of the shock absorber can then be made depending on the rate of change. If the rate of change exceeds a predetermined limit, slippage is detected because it is unlikely that a relatively high rate of change can be caused by the introduction of laundry into the laundry drum.

Under a household appliance for the care of items of laundry is understood in particular a washing machine or a washer-dryer.

The oscillating system comprises in particular a tub, which is supported on the at least one shock absorber and in particular suspended on a spring assembly. The oscillating system also includes in particular a laundry drum, which is rotatably mounted in the tub.

In the present case, a displacement sensor is understood to mean a sensor which is designed to detect the altitude of the oscillating system. This displacement sensor can be based on any physical principle, for example on optical and / or electrical and / or electromechanical and / or electromagnetic effects. The output signal of the displacement sensor may be an analog or a digital signal.

A "slippage of the shock absorber" in the present case is understood to mean a movement or slippage of a friction lining of the damper relative to its friction partner, in particular a cylinder of the damper. As a shock absorber, in particular a damper can be used, as in the document DE 10 2010 042 173 A1 is described.

The displacement of the oscillating system is detected by means of the displacement sensor relative to a reference position of the system. In particular, this reference position can be a rest position of the oscillating system that occurs in an unloaded system. This rest position can be detected, for example, after completion of each operating program after unloading the laundry drum.

In one embodiment, it is provided that a dry mass of laundry items is determined as the load weight, which is introduced into the laundry drum of the oscillating system. This means that the loading weight of the laundry drum is determined before activating an operating program of the household appliance.

If the slippage is detected, the control device determines the abovementioned change value of the offset, which is compensated in the determination of the loading weight. This can in particular be effected in such a way that the change value of the displacement caused by the slippage is subtracted from a current measured value of the displacement sensor (after slipping) and the loading weight is determined as a function of the subtraction result. A distortion of the load weight can thus be prevented.

The invention also relates to a domestic appliance for the care of laundry items, comprising a vibrating system including a laundry drum for holding the laundry items, with at least one shock absorber for damping vibrations of the oscillating system against a housing of the household appliance, with at least one displacement sensor for providing measured values indicate a displacement of the oscillating system relative to a reference position, and with a control device for determining a loading weight of the oscillating system on the basis of the measured values. The control device is designed to evaluate a time characteristic of the measured values during a loading process of the oscillating system (16), to detect, based on the time course, slippage of the shock absorber during loading of the oscillating system, to determine a change value of the displacement caused by the slipping to compensate for the determination of the loading weight and then to detect slippage, if, based on the time profile of the measured values, a change in the displacement within a time interval of a predetermined length is detected, which is greater than a predefined limit value.

The preferred embodiments presented with reference to the method according to the invention and their advantages apply correspondingly to the household appliance according to the invention.

Further features of the invention will become apparent from the claims, the figures and the description of the figures. All the features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively indicated combination but also in other combinations or alone.

The invention will now be described with reference to a preferred embodiment and with reference to the accompanying drawings.

• Fig. 1 in schematischer Darstellung ein Haushaltsgerät gemäß einer Ausführungsform der Erfindung;
• Fig. 2 eine Abhängigkeit einer Dämpferkraft von einer Absenkung eines schwingenden Systems des Haushaltsgeräts; und
• Fig. 3 eine Abhängigkeit eines gemessenen Beladungsgewichts von einem tatsächlichen Gewicht von eingebrachten Wäschestücken, wobei ein Verfahren gemäß einer Ausführungsform der Erfindung näher erläutert wird.

Show it:

• Fig. 1 a schematic representation of a household appliance according to an embodiment of the invention;
• Fig. 2 a dependence of a damper force on a lowering of a swinging system of the household appliance; and
• Fig. 3 a dependence of a measured load weight of an actual weight of introduced laundry, wherein a method according to an embodiment of the invention is explained in more detail.

An in Fig. 1 illustrated household appliance 1 is a washing machine in the embodiment. The household appliance 1 comprises a tub 2, in which a laundry drum 3 is rotatably mounted. In the laundry drum 3 are laundry items 4, which are washed in the household appliance 1 during a care process.

The tub 2 is suspended by a spring assembly 5 on a device housing 6 of the household appliance 1. In the exemplary embodiment, the spring arrangement 5 comprises a first and a second spring 7, 8, wherein the number of springs can be basically arbitrary.

The tub 2 is further supported on a damper assembly 9, which in the embodiment comprises a first and a second shock absorber 10, 11. The shock absorbers 10, 11 are friction dampers. The number of shock absorbers 10, 11 used can basically be chosen arbitrarily. For example, the damper assembly 9 may also include three or four such shock absorbers 10, 11.

The laundry drum 3 is rotatably mounted in the tub 2 about a horizontally extending axis of rotation 12 and is driven by means of an electric drive motor 13. A rotor of the drive motor 13 may be connected, for example via a belt with the laundry drum 3 in a conventional manner.

The tub 2 and the laundry drum 3 form a total of a vibrating system 16 which is suspended via the springs 7, 8 movable in the device housing 6. For damping large amplitudes, the shock absorbers 10, 11 are used.

In the household appliance 1, a central control device 14 and an electronic engine control unit 15 are further arranged. While the central electronic control device 14 is used to control the care processes of the household appliance 1 and thus represents a higher-level control device, it is the task of the motor control unit 15 to control the electric drive motor 13. For example, while the speed of the drive motor 13 is controlled by means of the engine control unit 15. The central control device 14 can communicate with the engine control unit 15, for example via a communication bus, not shown, or wirelessly.

For controlling the care processes of the household appliance 1, the central control device 14 requires information about the current parameter values of various operating parameters of the household appliance 1, in particular information about the load weight or the dry mass of the laundry items 4. To record this load weight, a displacement sensor 17 is used, which is located between the vibrating System 16 on the one hand and a bottom 18 of the device housing 6 is clamped and detects the movement of the tub 2 and the entire oscillating system 16 relative to the device housing 6 in the vertical direction z and thus perpendicular to the axis of rotation 12 or optionally in several dimensions. Of the Distance sensor 17 detects a current position or displacement of the oscillating system 16 with respect to a reference position, which corresponds in particular to a rest position of the oscillating system 16. The measured values provided by the displacement sensor 17 are transmitted to the control device 14, which then uses these measured values to determine the current load weight.

Fig. 2 shows the dependence of a force F introduced by the shock absorbers 10, 11 into the oscillating system 16 from a depression A of the oscillating system 16. In a first section 19, the weight of the vibrating system 16, including loading, is in equilibrium with the forces of the springs 7, 8 and the force F. impressed by the shock absorbers 10, 11. The linear course of the section 19 shows that the springs of the shock absorbers 10, 11 are continuously tensioned. At a point 20, a static friction FH of the shock absorbers 10, 11 is overcome, and the friction lining slips through, which can be recognized by a further section 21, in which the force F decreases. According to section 22, the spring of the respective shock absorber 10, 11 stretched again, wherein after reaching the static friction FH, the friction lining again slips. The slippage takes place within a very small time interval T.

The interest in the present case is the compensation of the determination of the load weight due to a change in the equilibrium when the shock absorbers 10, 11 come into their non-linear working range and slip. In order to detect this slippage of the shock absorber 10, 11 during the loading process, the control device 14 evaluates the time profile of the measured values of the displacement sensor 17. The control device 14 checks whether a very large change in the measured values occurs within a very short time interval. If such a change is detected within a very short time - for example within two milliseconds - it can be assumed with very high probability that this change is due to a slipping shock absorber 10, 11.

The controller 14 may also determine a rate of change v = ΔS / Δt as a change in the shift ΔS per unit time Δt and over the whole Evaluate the measurement period. The measured value changes can basically be assigned to three possible causes:
The rate of change v is nearly zero and thus less than a predetermined first limit G1: a low rate of change indicates a change in the load weight and thus a conventional user loading action.

The rate of change v is greater than the first threshold G1 and less than a higher second threshold G2. This moderate rate of change v indicates manual manipulation of the vibrating system 16 by the user, which is ignored by the controller 14 herein. This position change of the oscillating system 16 is thus not corrected in the determination of the load weight.

The rate of change v is very large and therefore greater than the second limit G2: If this is detected, it is assumed that a slipping shock absorber 10, 11. Slippage of the shock absorber 10, 11, i. A displacement of the position of the friction lining within the shock absorber 10, 11, namely, exists when the measured values of the displacement sensor 17 change very quickly, which can be detected by the control device 14 on the basis of the rate of change v.

A typical dependency of the measured loading weight B on the actual load or the actual weight B 'of the introduced laundry items 4 is shown in FIG Fig. 3 shown. How out Fig. 3 shows that the rate of change v is initially relatively low and almost equal to zero. As indicated at 23, the position or displacement of the oscillating system 16 changes abruptly upon reaching the stiction of the shock absorbers 10, 11. Upon detection of this slippage, the controller 14 determines a change value 24 of the position of the oscillating system 16 caused by slippage This change value 24 represents an offset, which is then compensated in the determination of the loading weight B. The result of the determination of the loading weight B without this compensation is in Fig. 3 denoted by 25. If the change value 24 is compensated, then a Loading weight B determined by the control device 14, which is much more realistic. The loading weight B with the compensation according to the invention is in Fig. 3 denoted by 26. How out Fig. 3 In the context of the compensation, the determined change value 24 is deducted from the current measured values of the displacement sensor 17 detected after the detection of slippage.

LIST OF REFERENCE NUMBERS

1

household appliance

2

tub

3

washing drum

4

laundry

5

spring assembly

6

device housing

7, 8

feather

9

damper arrangement

10, 11

shock absorber

12

axis of rotation

13

drive motor

14

control device

15

Engine control unit

16

swinging system

17

displacement sensor

18

ground

19

section

20

Point

21

section

22

section

23

position change

24

Modifier

25

uncompensated history

26

compensated course

A

lowering

B, B '

load weight

F

force

FH

stiction

G1, G2

limit

T

time interval

v

rate of change

z

vertical direction

.DELTA.S

Change of shift

.delta.t

time unit

Claims (6)

1. Method for determining a loading weight (B) of an oscillating system (16) of a domestic appliance (1) for treatment of items of laundry (4), in which oscillations of the oscillating system (16) are damped by means of at least one shock absorber (10, 11), which is embodied as a friction shock absorber, against a device housing (6) of the domestic appliance (1), and in which measured values are provided by means of a position sensor (17) embodied to detect a height position of the oscillating system (16), which measured values specify a displacement in the height direction of the oscillating system (16) in relation to a reference position corresponding to a rest position of the oscillating system (16), the loading weight (B) is determined by means of a control device (14) on the basis of the measured values, and, during the loading process of the oscillating system (16), a temporal sequence of the measured values is evaluated by the control device (14), characterised in that on the basis of the temporal sequence of the measured values, a slipping of a friction lining relative to a cylinder of the shock absorber (10, 11) is detected during loading of the oscillating system (16), wherein the slipping of the shock absorber occurs when a static friction FH of the shock absorber is overcome and the slipping is detected when, as a result of the temporal sequence of the measured values, a change in the displacement is detected within the time interval of a predetermined length that is greater than a predetermined limit value, and wherein a change value (24) of the displacement caused by the slipping is determined by the control device (14) and is compensated for in the determination of the loading weight (B).
2. Method according to claim 1, characterised in that a dry mass of items of laundry (4), which is introduced into a laundry drum (3) of the oscillating system (16), is determined as the loading weight (B).
3. Method according to one of the preceding claims, characterised in that, on the basis of the temporal sequence of the measured values, a rate of change (v) is determined as a change of the displacement (ΔS) per unit of time (Δt) by the control device (14) and the slipping is detected as a function of the rate of change (v).
4. Method according to claim 3, characterised in that the slipping is detected when the rate of change (v) exceeds a predetermined limit value (G2).
5. Method according to one of the preceding claims, characterised in that the compensation comprises the change value (24) of the displacement caused by the slipping being subtracted from a current measured value of the position sensor (17) and the loading weight (B) being determined as a function of the subtraction result.
6. Domestic appliance (1) for treatment of items of laundry (4), with an oscillating system (16) including a laundry drum (3) to accept the items of laundry (4), with at least one shock absorber (10, 11), which is embodied as a friction shock absorber, for damping oscillations of the oscillating system (16) against a device housing (6) of the domestic appliance (1), with at least one position sensor (17) for providing measured values, which specify a displacement in the height direction of the oscillating system (16) in relation to a reference position corresponding to a rest position of the oscillating system (16), and with a control device (14) for determining a loading weight (B) of the oscillating system (16) on the basis of the measured values, wherein the control device (14) is designed, during a loading process of the oscillating system (16), to evaluate a temporal sequence of the measured values, characterised in that the control device (14) is further designed, on the basis of the temporal sequence of the measured values, to detect a slipping of a friction lining relative to a cylinder of the shock absorber (10, 11) during loading of the oscillating system (16), wherein the slipping of the shock absorber occurs when a static friction FH of the shock absorber is overcome and a slipping is detected when, as a result of the temporal sequence of the measured values, a change in the displacement is detected within a time interval of a predetermined length that is greater than a predetermined limit value, and to determine a change value (24) of the displacement caused by the slipping and to compensate for it in the determination of the loading weight (B).

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