GB2270373A

GB2270373A - Spinning cycle control in a drum washing machine

Info

Publication number: GB2270373A
Application number: GB9318269A
Authority: GB
Inventors: Peter Blauert; Frank Boeldt; Martina Woebkemeier
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-09-04
Filing date: 1993-09-03
Publication date: 1994-03-09
Anticipated expiration: 2013-09-03
Also published as: FR2695415A1; ES2087010B1; ITMI931880A0; FR2695415B1; TR26964A; GB9318269D0; ES2087010A2; GB2270373B; DE4229646C2; DE4229646A1; IT1272552B; ES2087010R; ITMI931880A1; KR940002409A

Abstract

A method of operating a drum washing machine comprises driving the drum at a predetermined rotational speed (nU) which is below the resonance speed and when the laundry lies against the inner circumference of the drum, the imbalance of the laden drum being measured. Subsequently, the main spinning phase is carried out at a final speed which is above the resonance speed and is set, in dependence on the measured amount of imbalance, between two limit values (tSE1, tSE2). The spinning phase is also variable in respect of rate ( alpha ) of acceleration to the final speed and spinning duration (tSB to tSE). The setting of rate of acceleration and spinning duration can be carried out in dependence on laundry quantity and/or laundry kind making up the drum load. <IMAGE>

Description

SPINNING CYCLE CONTROL IN A DRUM WASHING MACHINE The present invention

relates to a method of operating a drum washing machine and to a machine in which the method can be performed.

In German published specification 40 22 715 there is described a washing machine spinning cycle in which a subsequent operational phase of the spinning cycle is carried out with a final drum rotational speed which lies above the resonance speed and between two walues in dependence on an impermissible level c -%A: J r UM imbalance ascdrtained in the measurement phase. This operational phase, however, serves for preliminary draining of the laundry load, which is subsequently examined once again for imbalance within a measurement phase. The actual spinning cycle is carried out only after detection of a permissible level of imbalance and then at a final speed above the previously set rotational speeds.

is Such a known method suffers from the tracki ng of a fixedly registered profile for the main spinning cycle. Each laundry load is treated without differentiation, whereby on the one hand a risk of damage to sensitive articles of laundry arises and on the other hand either the spinning result or the treatment duration leaves something to be desired in the case of many laundry loads not matched to this profile. Moreover, the damping equipment installed in washing machines must be designed for the most unfavourable relationship between a fixed main spinning profile and laundry charges matched thereto, which causes appreciable unnecessary cost.

It would thus be desirable to improve the spinning process in the sense that the profile of spinning cycles may be individually adaptible to laundry loads so that the laundry is treated carefully and the spinning result improved while expenditures on damping means 5 in washing machines may be reduced.

According to a first aspect of the present invention there is provided a method of operating a drum washing machine for spin-drying laundry in the machine drum, comprising the steps of causing the laden drum to rotate at a given speed in an operational phase at the star-:;,- of a spinning cycle of the machine with the laundry already disposed against the inner circumference of the drum, the given speed being below the resonance speed of the drum, measuring the imbalance of the drum while rotating at the given speed, determining a final rotational speed of the drum for a further operational phase of the spinning cycle, the final rotational speed being above the resonance speed and set between two limit values in dependence on the measured imbalance, and determining at least one of the rate of acceleration to the final rotational speed and the duration of the spinning cycle.

According to a second aspect of the invention there is provided a drum washing machine with a spinning cycle for spin-drying laundry in the machine drum, the machine comprising means to cause the laden drum to rotate at a given speed in an operational phase at the start of a spinning cycle of the machine with the laundry already disposed against the inner circumference of the drum, the given speed being below the resonance speed of the drum, means to measure the imbalance of the drum while rotating at the given speed, means to determine a final rotational speed of the drum for a further operational phase of the spinning cycle, the final rotational speed being above the resonance speed and set between two limit values in dependence on the measured imbalance, and means to determine at least one of the rate of acceleration to the final rotational speed and the duration of the spinning cycle.

The measures provided by such a method and in such a washing machine may lead to a more gentle treatment of the laundry not only because the laundry can be spun only as long as absolutely necessary for a desired degree of drying of the laundry, but also because laundry loads at the upper end of the sensitivity scale can be treated with sufficient care. These measures may also reduce the number of the acceleration trials and improve the standing behaviour of the washing machine by more -exact judgement of the parameters given by the laundry type, distribution and initial moisture. Testing has shown higher average values for the attained final drum speeds of the main spinning cycle and thereby lower average residual moistures and thus a better spinning result.

A method exemplifying a washing machine embodying the present invention will now be more particularly described with reference to the accompanying- drawing, which is a diagram showing plots of drum speed against time in the spinning cycle of a washing machine embodying the invention.

Referring now to the drawing, there is shown a spinning program diagram for a drum washing machine operable to perform a spinning cycl e. The cycle consists of a measurement operational phase T U in which drum imbalance is measured, an acceleration phase t RB to tsB in which the drum is accelerated from a predetermined speed n U at which the measurement is carried out to a set final speed, and a spinning operational phase t SB to tSE at which the drum is driven constantly at the final speed in order to perform spin-drying of laundry in the drum. The washing machine includes devices for ascertaining the q jcn,-IL..ity and/or the kind of laundry forming 11.111e drum load. In that case, the spinning cycle duration will depend on the ascertained laundry quantity and/or laundry kind making up the drum load. This duration is to be set between limits t SE1 and t SE2 The kind of laundry determines the spinnin.g duration in the sense that, for example, the fibres of fabrics that retain relatively little water, such as synthetic fabrics, cause the spinning duration to be set rather closer to the lower limit tSE11 whereagainst the fibres of fabrics which retain a relatively large amount of water, such as cotton fabrics, cause the spinning duration to be set rather closer to the upper 1 imit t SE2 The quantity of the laundry also has an influence on the selection of the spinning duration, because a larger laundry quantity offers greater resistance to the flowing away of water expelled from the fabric than a smaller laundry quantity. Accordingly, a larger laundry charge should preferably be spun for a longer time than a smaller charge. A matrix-like table, from which different spinning durations can be derived, can be set up from these two parameters of quantity and the kind of laundry.

In addition, the steepness ol- of the. slope of acceleration of the drum speed can be set between the limits -Cl and oC2, which is of substantial importance for improved standing behaviour of the washing machine and for reduction in the number of acceleration trials.

If a high value for the still permissible imbalance is ascertained during the imbalance interrogation phase TU, a more rapid acceleration with a slope steepness oC2 is preferable than in the case of a lower ascertained imbalance.

The term "imbalance" characterises the situation only generally, since two parameters influence the imbalance detected during the imbalance measurement phase TU at the predetermined speed nu, which is below the resonance speed. One of these parameters is the weight imbalance due to the load mass not being distributed equally. The other parameter is the quanti-ty of laundry (= total mass), which is to be accelerated and which gives the oscillating system an additional inertia. A large total mass has a greater inertia and therefore also reduces the influence of a mass distributed with imbalance. Therefore, there are in terdependencies of the effects of mass imbalance and total mass. These interdependencies can be taken into consideration in the selection of the steepness of the slope. A less steep slope has the advantage of a longer preliminary drainage so that the total mass of laundry and water can be appreciably lower before reaching of the final rotational speed than in the case of a steeper slope.

Similar interdependencies are also effective on the attainment o12 the final speed in the main spinning phase. It is therefore desirable to set the final speed in dependence on the laundryquantity and/or laundry kind in the drum load and on the amount of the imbalance. A greater imbalance weighted by the quantity of the load therefore leads to the setting of a lower final speed closer to nEl and conversely a lower imbalance to a higher final speed closer to n E2 Interdependencies between imbalance and loading are dependent not only on the kind and the quantity of the laundry charge, but also on certain machine construction parameters. From such parameters, algorithms are developed which finally determine the steepness of the slope, the final rotational speed and the spinning duration. The actual mode and manner of -the ascertaining of imbalance and kind and/or quantity of the laundry load is freely selectable. One possibility is to make use of fluctuations in rotational speed measurable at the tachogenerator of the drum drive motor. The kind and quantity of the load are also deducible in other ways from process parameters of washing program phases that have just taken place.

Claims

1. A method of operating a drum washing machine for spin-drying laundry in the machine drum, comprising the steps of causing the laden drum to rotate at a given speed in an operational phase at the start of a spinning cycle of the machine with the laundry already disposed against the inner circumference of the drum, the given speed being below the resonance speed of the drum, measuring the imbalance of the drum while rotating at the given speed, determining a final rotational speed of the drum for a further operational phase of the spinning cycle, the final rotational speed being above the resonance speed and set between two limit values in dependence on the measured imbalance, and determining at least one of the rate of acceleration to the final rotational speed and the duration of the spinning cycle.

2. A method as claimed in claim 1, wherein at least one of the rate of acceleration and the duration of the spinning cycle is determined in dependence on at least one parameter of the laden drum.

3. A method as claimed in claim 2, wherein the rate of acceleration is determined in dependence on at least one of laundry kind and laundry quantity in the laden drum.

4. A method as claimed in claim 2 wherein the duration of the spinning cycle is determined in dependence on at least one of laundry kind and laundry quantity in the laden drum.

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5. A method as claimed in any one of the preceding claims, wherein the final rotational speed is additionally set in dependence on at least one of laundry kind and laundry quantity in the laden drum.

6. A method substantially as hereinbefore described with reference 5 to the accompanying drawing.

7. A drum washing machine with a spinning cycle for spin-drying laundry in the machine drum, the machine comprising means to cause the laden drum to rotate at a given speed in an operational phase at the start of a spinning cycle of the machine with the laundry already disposed against the inner circumference of the drum, the given speed being below the resonance speed of the drum, means to measure the imbalance of the drum while rotating at the given speed, means to determine a final rotational speed of the drum for a further operational phase of the spinning cycle, the final rotational speed 16 being above the resonance speed and set between two limit values in dependence on the measured imbalance, and means to determine at least one of the rate of acceleration to the final rotational speed and the duration of the spinning cycle.

8. A washing machine as claimed in claim 7, comprising means to determine at least one parameter of the laden drum, at least one of the rate of acceleration and the duration of the spinning cycle being determined in dependence on said at least one parameter.

9. A washing machine as claimed in claim 8, said means to determine at least one parameter being arranged to determine at least one of laundry kind and laundry quantity in the drum, at least one of the^" rate oil acceleration and duration of the spinning cycle being determined in dependence on the determined laundry kind and/or laundry quantity.

10. A washing machine as claimed in any one of claims 7 to 9, wherein the final rotational speed is additionally set in dependence on at le--.st one of laundry kind and laundry quantity in tne laden drum.

11. A washing machine substantially as hereinbefore described with reference to the accompanying drawing.