DESCRIPTION

The present invention relates to a method for determining a preferred speed of rotation of a drum within a laundry washing machine or washing/drying machine according to the preamble of claim 1, as well as to a machine for the treatment of laundry adapted to implement said method. In particular, the present invention applies to the field of laundry washing machine and washing/drying machines for domestic use, and specifically to solutions for wash optimization.

Wash optimization, both in terms of wash efficiency and of energy consumption, is a problem which is felt and faced by all big manufacturers of household appliances. At present, several measures are known which allow to obtain such an optimization, e.g. measures related to the rotation of the drum or to the choice of temperatures and wash/rinse phases.

In order to improve both energy consumption and environmental impact, special systems are currently used for controlling the quantity of water supplied, so that the quantity of water supplied is proportional to the laundry load.

The optimization of water supply allows to reduce both the water consumption and the electric energy required to heat the water up to wash temperature.

Furthermore, some prior patents, such as the patent EP 0 143 685, provide for calculating the weight of the laundry load to be treated in a washing machine or washing/drying machine with rotating drum. Such a system measures a plurality of parameters, among which drum acceleration and torque required to keep it rotating, in order to determine the exact weight of the laundry load and thus be able to determine the quantity of water to be supplied as well as other parameters of the wash programme. However, such a system is too complex and cannot be used in commercial products, in that the parameters taken into account for determining the moment of inertia of the laundry load are too many and subject to much uncertainty. The errors of measure of all parameters add together, so that the method result turns out to be unreliable. The object of the present invention is therefore to provide a method for optimizing the wash in a laundry washing machine or washing/drying machine, which allows to

overcome the drawbacks of the above-mentioned methods.

The present invention takes as a starting point the fact that, in known laundry washing machine and washing/drying machines, the laundry to be washed is placed inside a drum which is driven by a motor at a speed of rotation being optimized, according to international standards, for a maximum load, e.g. 5 kg.

Also, it has been observed that wash efficiency, i.e. the capacity of removing dirt from the laundry to be washed, is bound to the speed of rotation of the drum and also depends, the washing agents used being equal, on the efficiency of the mechanical action exerted on the laundry; said mechanical action depends also on the speed of rotation of the drum. At the same speed of rotation of the drum, therefore, the dirt is removed in different percentages depending on, in particular, the weight and/or moment of inertia of the laundry being present inside the washing machine.

Object of the present invention therefore is also to provide wash optimization while observing the restrictions imposed by the international standards, without for this reason limiting the speed of rotation of the drum to a predetermined value during the production stage.

Furthermore, it should be noted that a laundry wash, or more in general a treatment for laundry, sized for a 5kg load, may turn out to be too stressful for a lighter load. As a matter of fact, the load undergoes a mechanical action which on the one hand allows to remove dirt, but on the other hand may damage or cause premature wear of the fabrics; it is therefore necessary to find the best compromise between care for the treated fabric and wash efficiency.

Thus, the present invention also aims at providing a treatment for fabric care-oriented laundry. These and further objects of the present invention are accomplished through a method of treatment for laundry and a machine for the treatment of laundry having the features of the annexed claims, which form an integral part of the present description. Further objects and advantages will become apparent from the following detailed description and annexed drawings, supplied by way of non-limiting example, wherein: Fig. 1 shows a machine for the treatment of laundry according to an embodiment of the invention. Fig. 2 schematically shows the trend of the speed of rotation of the drum as a function of

time in a laundry washing machine using a preferred application of the method according to the present invention.

Fig. 3 shows the trend of torque as a function of speed of rotation and load. Fig. 4 shows the percentage of dirt removed in respect of the speed of rotation for a lkg load of cotton linen.

Fig. 1 shows a machine 1 for the treatment of laundry which, in its preferred embodiment described below, is a laundry washing machine.

It is however clear that the invention according to the following description may also be easily applied to other typologies of machines for the treatment of laundry , in particular to washing/drying machines, clothes dryers or laundry dyeing machines.

The machine 1 for the treatment of laundry has a load opening 2 which provides access to a drum 3 wherein the laundry to be treated is placed. The load opening can be closed through a door 4. By means of a control panel 5, which in the example of Fig. 1 is located on the front side of the machine, the user selects the functions of the machine for the treatment of laundry, e.g. delicate wash, wash temperature, etc. The functions are selected through means being known to those skilled in the art, e.g. knobs 6, push-buttons 7 and display 8. A control unit 9 is connected to the control panel 5 and it processes the selections made by the user and controls the various machine components which allow to perform the functions selected by the user.

In the case of a washing machine, as the one shown in Fig. 1, the control unit 9 controls in a known way a whole set of components, such as, for example, the switches that supply voltage to the water heating resistance or the drain system. These machine components and the control of the same performed by the control unit will not be described any further in the following, in that they are known in the art and are not fundamental to understand the present invention.

According to the invention, the control unit of the machine 1 is capable of providing a particularly efficient and intelligent control of the motor 10 which starts the rotation of the drum, thus carrying out a method for the treatment of laundry which allows to improve the treatment, i.e. the wash in this case.

The machine 1 for the treatment of laundry according to the invention therefore comprises:

A-

• a drum adapted to contain laundry,

• a motor adapted to drive said drum,

• a control unit adapted to control said motor,

• means adapted to measure a characteristic operating parameter of said motor and to provide a measured value to said control unit;

According to the invention, the machine 1 also comprises at least one memory area 11 containing code portions adapted to implement a method for determining a preferred speed of rotation of a drum within a machine for the treatment of laundry. According to the invention, the drum containing the laundry to be treated is driven by a motor according to a method comprising the following steps: a) carrying out a sequence of phases of measure, in each of said phases of measure the drum being rotated at a different and preferably constant speed of rotation and at least one characteristic operating parameter of said motor being measured, b) comparing the values of said operating parameter, measured during said phases of measure, with corresponding reference values contained in a memory area of said machine for the treatment of laundry, c) determining said preferred speed of rotation through said comparison.

The sequence of phases of measure may include, between two consecutive phases of measure, intermediate phases wherein, for instance, the drum is stopped or rotated without any measure being carried out. However, such a solution suffers the drawback of a longer time being required for determining the preferred speed of rotation. Fig. 2 schematically shows the rotation of a drum within a laundry washing machine using a preferred application of the method according to the present invention. After having completed the soaking phase of the laundry load(designated I in Fig. 2), the control unit rotates the motor according to a sequence of phases of measure Fl, F2 ..Fn ₅ wherein the drum is rotated at a constant speed for short time intervals, preferably for approximately ten seconds per phase. As better described below, by comparing these measures with reference values, the method then allows to determine a preferred speed of rotation for the wash phase L. In a preferred embodiment of the method according to the invention, said phases of measure are carried out at 25, 30, 35, 40, 45, 50, 55, 60 rpm, i.e. starting from a first phase of measure at a relatively low speed of rotation (25 rpm), until a last phase of

measure carried out at a relatively high speed of rotation (60 rpm), being slightly higher than the typical wash speed of a laundry washing machine.

Of course, the number of phases of measure and the corresponding speeds of rotation may be chosen according to a compromise between the accuracy required from the method according to the invention (e.g. in the case of a washing machine, to obtain a percentage of dirt removed being higher than 45%) and the time needed to complete the measure. Said choice is not binding for the purposes of the present invention. In a preferred embodiment, each phase includes the measure of a torque value, in particular an electric torque value, necessary to keep the drum turning at the constant speed of rotation set for the phase of measure. Preferably, said torque value is the mean value of the torque measured during the phase of measure.

With reference to the above-mentioned phases of measure, a torque reading at 25rpm, another torque reading at 30rpm, and so on will be obtained for all the phases of measure. Fig. 3 shows the result of laboratory experimental measures; in particular, it shows three curves A, B, C corresponding to the linear interpolation of the torque readings taken during the different phases of measure for lkg, 3kg and 5kg loads, respectively. As shown in Fig. 3, different loads return different torque curves; these curves may also vary depending on the weight and material of the treated laundry. Tests carried out have shown that the optimum speed of rotation which optimizes the treatment of laundry is different according to the weight and type of the load. As far as a laundry washing machine is concerned, the wash efficiency may for instance be rated according to the percentage of dirt removed, calculated as a ratio between the reflectance of the laundry item before and after the wash; alternatively, for example, said percentage may also be calculated as a ratio between the reflectance of the laundry item after the wash and the reflectance of a reference dirty item.

Fig. 4 shows an experimental measure of the percentage of dirt removed R with reference to the speed of rotation of the drum, expressed in rpm; the measure refers to a lkg load of cotton. The graph of Fig. 4 clearly shows that the optimum speed of rotation for a lkg load of cotton is approximately 47 rpm, which is the speed of rotation of the drum allowing to obtain the maximum percentage of dirt removed (46%). According to the invention, the machine 1 comprises a memory area, being preferably of

the non-volatile type, containing reference values to be compared with the readings taken before the treatment of laundry. Through this comparison it is then possible to identify a speed of rotation which improves the treatment.

If measures of the torque values necessary to keep the drum rotating are carried out, the values of measure will be torque values.

According to the invention, therefore, wash tests with different types of loads are carried out during production, and the results of the measures carried out during the respective phases of measure are stored in a suitable memory area being accessible to the control unit. When the user uses the machine 1 to perform a treatment of laundry, the control unit carries out a sequence of measures F 1..Fn as described above, thereby obtaining a set of values which can be compared with the reference values stored in the memory area 11 during production. Through this comparison, the machine 1 will identify the behavior of the laundry load to be treated as similar to that of a certain load which was tested during production, and therefore will select the corresponding preferred speed of rotation to optimize the treatment of laundry.

According to a particularly advantageous embodiment, the speed is determined by choosing a speed value among a plurality of predetermined speed values contained in a memory area of said machine. This choice is made following the result of the comparison between the values measured and the reference values; in particular, said comparison may include the identification of the minimum differences between said values measured and said reference values, so as to determine which load tested during production is closest to the laundry load to be treated; the preferred speed of rotation chosen for the laundry load to be treated will correspond to the optimum speed of rotation, measured in laboratory and stored in a memory area of the machine.

The invention therefore provides a method for controlling a machine for the treatment of laundry wherein a laundry drum is rotated by a motor at least at one speed of rotation, and wherein at least one speed of rotation is determined for every new laundry load placed in said drum.

In particular, the determination of the preferred speed of rotation of the drum is preferably carried out only once for each new laundry load to be treated, so that treatment

times are not long.

According to a further embodiment, said determination of the preferred speed of rotation of the drum may be carried out several times for the same laundry load. In the case of a washing/drying machine, a first speed of rotation may be determined for the wash process, whereas a second speed of rotation may be determined for the drying process.

It is clear that many other variations are possible for those skilled in the art without departing from the inventive idea resulting from the annexed claims and from the description of the preferred embodiments.

In particular, in the above embodiment example just one method was indicated for comparing the measured values with the reference values stored in a memory area of the machine; it is clear, however, that many other comparison algorithms, if appropriately conceived, may be employed.

For instance, the characteristic operating parameter of the motor 10 may be power consumption instead of the motor torque. By measuring the power consumption (as a voltage, current or power value without distinction), it is still possible to follow the behaviour of the motor in relation to the laundry load placed in the drum and of speed of rotation.

By comparing the power consumption, or the power consumption mean value, read during the phases measure repeated for each new treatment of laundry, with the power consumption values contained in a memory area 11 of the machine, it will be possible to determine a preferred speed of rotation for the laundry load to be treated.

The method according to the invention may be particularly advantageous when applied to a machine for the treatment of laundry provided with a three-phase motor, wherein the voltage of each phase is imposed through an inverter controlled by the control unit. In this case, in fact, those skilled in the art may use a plurality of known solutions which allow to follow the behaviour of the motor through the information returned to the control unit by the inverter.