EP0159202B1 - Washing machine with automatic detection of the load and the kind of laundry - Google Patents

Abstract

For the automatic determination of the load of laundry introduced into the machine and hence for selecting the washing programme, the washing machine includes a means of measuring the driving torque of the drum at constant acceleration (t3, t4) of the drum. This enables the moment of inertia of the washing load about the rotation axis of the drum to be measured. <IMAGE>

Description

The invention relates to a washing machine.

The operating program of a washing machine depends on a certain number of parameters which are: the type of laundry, the degree of soiling, the desired temperature for washing and possibly the quantity of laundry. An automatic washing machine therefore has a programmer which, on the basis of this data displayed by the user, determines a program, that is to say: a washing duration and / or a stirring energy (number of rotations of the drum containing the laundry), possibly a temperature for heating the washing water (if it was not displayed directly by the user), if applicable - if a data depending on the quantity of laundry has been entered - the volume of washing water, a number of rinses, and a speed of rotation of the drum to perform the spin.

Programming a washing machine is often seen as tedious and / or difficult by users. It is therefore beneficial to limit the number of parameters that this user must display. It has already been proposed (US Pat. No. 4,235,085 or international PCT application JP83 00140) to automatically determine the mass of laundry in a washing machine with agitator by measuring the current passing through the agitator drive motor of the machine. These arrangements known up to now do not give a satisfactory representation of the load of laundry introduced into the washing machine. The invention provides an indication which correctly represents the load of laundry in a drum washing machine.

In addition, it is advantageous to minimize the volume of water used for washing because, on the one hand, water is expensive in itself and, on the other hand, the amount of energy used increases with the volume of water. The invention allows such minimization while facilitating the use of the machine or, at least, not complicating it.

The washing machine according to the invention is characterized in that, in order to determine the load of laundry (percentage of the volume of the drum which is occupied by the laundry) in the drum, it comprises, in order to measure the moment of inertia of the laundry relative to the axis of rotation of the drum, means for determining the driving torque of the drum at constant acceleration and means for measuring the driving torque of the drum during this acceleration. Thus, before filling with water, the drum filled with dry linen is rotated at constant known acceleration and the engine torque is measured. (driving the drum) which is proportional, to within a constant, at the moment of inertia. When a universal motor is used to rotate the drum and when this motor is supplied at constant voltage, it is sufficient to measure the intensity of the current flowing through the motor - which is a linear function of the motor torque - to obtain a linear representation of the moment of inertia.

The laundry load is thus determined very simply.

In the preferred embodiment of the invention, this measurement of the load of laundry is used to automatically determine the type of laundry introduced into the machine and thus to select the washing program. To this end, a means is provided for measuring the amount of water absorbed by the dry or practically dry laundry.

In fact, the quantities of water absorbed by dry laundry for the same mass or for the same machine load vary from one type of laundry to another. For example, if mass is taken into account, linen made of synthetic fabric absorbs approximately one liter of water per kilogram, cotton linen two liters per kilogram and terry linen four liters per kilogram. If instead of mass the load is taken into account, a drum of a given type contains, when fully loaded, either five kilograms of cotton linen, or four kilograms of terry cloth, or three kilograms of synthetic cloth linen ; in this case for the full load of this drum the volumes of water absorbed by the dry linen are: ten liters for cotton linen, sixteen liters for terry linen and three liters for synthetic fabric linen.

In this case, that is to say when determining, on the one hand, the load of laundry and, on the other hand, the amount of water absorbed by the dry or substantially dry laundry, we provide, in addition , a means for making the ratio between the quantity of water absorbed and the load measured.

The signal representing the load of laundry and possibly the type of laundry is used to impose constraints on the machine's operating program. Thus the indication of the size representing the load of linen, combined with the type of linen, linen, provides an optimum quantity - from an economic point of view - of water, to be introduced into the machine tank. Furthermore, if, for example, an absorption of about 1 liter of water per kilogram of linen has been detected, which corresponds to linen made of synthetic fabric, the program, preferably implanted in a microprocessor, will impose that the washing temperature cannot exceed 60 ° C.

If a mixture of two types of laundry is introduced into the machine drum, said signal representing the quantity of water absorbed will have a value between two characteristic values. In this case the program selected will be the one corresponding to the characteristic value closest to the actual value of the signal. The users being until now accustomed to wash together cotton linen and terry linen, it is preferable not to force them to carry out a sorting between these two types of linen. This is why the signal representing the amount of water absorbed by the linen makes a selection from only two possibilities: one for cotton and / or terry linen (cotton type) and the other for fabric linen. synthetic (synthetic type).

To determine the quantity of water absorbed by the dry laundry, the procedure is advantageously as follows:
The drum filled with laundry being stationary, water is introduced into the washing machine's tank to a level slightly above (1.5 cm for example) from the bottom of the drum and the opening time is measured of the solenoid valve necessary to perform this filling. This time is inversely proportional to the flow rate of the valve; in other words the duration of opening of the solenoid valve until said level is reached represents the flow rate of the latter. Since it is only a small fraction of the volume of the drum that is immersed in water, only a negligible fraction of the laundry is wet. After this filling, the drum - which, to minimize the amount of water absorbed by the laundry, was previously stationary - is rotated at a speed of the order of 30 revolutions per minute, lower than the speed provided for the washing ; the periphery of the laundry contained in the drum thus bathes in water and this laundry absorbs water, which causes a drop in the level in the tank. The solenoid valve is then opened again so that the free surface of the water in the tank returns to the predetermined level. Then the drum is again rotated so that the laundry continues to absorb water. The solenoid valve is open at each stage so that the free surface of the water in the tank always returns to said predetermined level. After a certain number of operations of this type, generally of the order of ten, the linen is completely soaked with water and the level remains constant in the tank. The quantity of water absorbed by the laundry is equal to the product of the flow rate of the solenoid valve by the sum of the opening times of this solenoid valve after the first filling and until the level is stabilized in the tank.

The various calculations, as well as the time measurements, can be easily carried out if a microprocessor is used.

To regulate (i.e. keep constant) the water level in the washing machine tank, at a low height above the bottom of the drum, it is preferable to use a thermistor fixed to the internal face of a wall of the tank and which is supplied with a sufficiently high voltage so that it is heated by the Joule effect. When this thermistor bathes in water its temperature decreases and therefore its resistance changes. It is this variation in resistance that is used to detect the arrival of water. In addition, this thermistor can be used to measure the temperature of the wash water. It is preferable that the thermistor is placed in a housing such that it is protected against drops of water which could reach it during filling, before the predetermined level is reached.

• la figure 1 est une représentation schématique d'une cuve et d'un tambour de lave-linge au cours d'une étape de fonctionnement de ce dernier,
• la figure 2 montre le fond d'une cuve et d'un tambour de lave-linge pour une autre étape de fonctionnement,
• la figure 3 est un schéma en coupe selon un plan vertical passant par l'axe de rotation du tambour du fond de ce tambour et de la cuve,
• la figure 3a est une coupe selon la ligne 3a-3a de la figure 3, et
• les figures 4, 5, 6 et 7 sont des diagrammes illustrant le fonctionnement des moyens de mesure du moment d'inertie du linge contenu dans le tambour.

Other characteristics and advantages of the invention will appear with the description of some of its embodiments, this being carried out with reference to the attached drawings in which:

• FIG. 1 is a schematic representation of a tank and a washing machine drum during an operating step of the latter,
• FIG. 2 shows the bottom of a tank and a washing machine drum for another operating step,
• FIG. 3 is a diagram in section along a vertical plane passing through the axis of rotation of the drum at the bottom of this drum and of the tank,
• FIG. 3a is a section along line 3a-3a in FIG. 3, and
• Figures 4, 5, 6 and 7 are diagrams illustrating the operation of the means of measuring the moment of inertia of the laundry contained in the drum.

In the example, the washing machine is of the tub type 10 (FIGS. 1, 2, 3 and 3a), of generally cylindrical shape limited by vertical side walls 11, inside which a drum 12 also turns d horizontal axis 20, the cylindrical peripheral wall 13 and / or the vertical side walls 14 are perforated to allow this drum 12, which contains the linen 14 _a , to have the water 15 introduced into the tank through a solenoid valve 16.

This washing machine is controlled by a microprocessor (not shown) which acts by means of interface circuits (also not shown) on the solenoid valve 16, on the motor - of the universal type in the example - for driving the drum 12, on the supply of the resistor 17 for heating the water disposed at the bottom of the tank 10 and possibly on means (not shown) for introducing detergents, bleaches, softeners, etc.

As will be seen below, the invention makes it possible to optimize, in an extremely simple manner, the operating program of the machine, that is to say to adapt it as best as possible to the quantity and to the type of linen introduced into the drum 12 in order to obtain the maximum washing efficiency and this while minimizing the amount of water used. In addition, user intervention is reduced to a minimum.

The machine's operating program takes account of data representing the load or mass of laundry introduced into the drum and the type of laundry (synthetic, sponge or cotton).

The parameter representing the quantity of linen introduced into the drum is, in the example, the moment of inertia L of this linen with respect to the axis 20 of rotation of said drum 12. It is in fact understood that for a given type of laundry having a specific density, the volume occupied by this laundry in the drum varies with the quantity and, therefore, its moment of inertia increasing with the volume, the greater the quantity of laundry, the greater the moment of inertia. For the same volume, for example the drum 12 completely filled, the density is different depending on the type of laundry; it follows that the moment of inertia is different depending on the type of laundry. Thus the same drum can be filled with 4 kilograms of terry cloth, 5 kilograms of cotton linen and 3 kilograms of synthetic linen.

   Dans cette formule C_e est le couple d'entraînement du tambour, c'est-à-dire le couple que fournit le moteur universel, C_f est le couple de frottement dû à la rotation du tambour, L, comme déjà indiqué, le moment d'inertie du linge par rapport à l'axe 20 de rotation du tambour, J_o est le moment d'inertie du tambour par rapport à son axe de rotation, ω est la vitesse de rotation du tambour et $\frac{\text{dω}}{\text{dt}}$

est l'accélération, c'est-à-dire la dérivée de ω par rapport au temps.To measure the moment of inertia L of the laundry, we start from the following formula:

$${\text{VS}}_{\text{e}}{\text{= (L + J}}_{\text{o}}\text{)}\frac{\text{from}}{\text{dt}}{\text{+ C}}_{\text{f}}\text{(1)}$$

In this formula C _e is the drive torque of the drum, that is to say the torque provided by the universal motor, C _f is the friction torque due to the rotation of the drum, L, as already indicated, the moment of inertia of the laundry with respect to the axis of rotation of the drum, J _o is the moment of inertia of the drum with respect to its axis of rotation, ω is the speed of rotation of the drum and $\frac{\text{from}}{\text{dt}}$

is the acceleration, i.e. the derivative of ω with respect to time.

   Dans cette formule J_o et C_f sont en principe des constantes. L'accélération $\frac{\text{dω}}{\text{dt}}$

peut être imposée pour être égale à une constante connue. Dans ces conditions le moment d'inertie L du linge ne dépend alors que d'un seul paramètre variable : C_e le couple d'entraînement du tambour. Comme le moteur d'entraînement du tambour est du type universel et comme la tension d'alimentation est constante, ce couple d'entraînement est lié à l'intensité 1 du courant électrique traversant le moteur par la relation suivante :

${\text{C}}_{\text{e}}{\text{= K (I - I}}_{\text{o}}\text{) (3)}$

   Dans cette formule K et I_o sont des constantes.From formula (1) above we deduce:

In this formula J _o and C _f are in principle constants. Acceleration $\frac{\text{from}}{\text{dt}}$

can be imposed to be equal to a known constant. Under these conditions the moment of inertia L of the laundry then depends on only one variable parameter: C _e the drive torque of the drum. As the drum drive motor is of the universal type and the supply voltage is constant, this drive torque is linked to the intensity 1 of the electric current flowing through the motor by the following relationship:

${\text{VS}}_{\text{e}}{\text{= K (I - I}}_{\text{o}}\text{) (3)}$

In this formula K and I _o are constants.

Thus, if the acceleration imposed on the drum is constant, the moment of inertia L of the laundry only depends on the intensity of the electric current passing through the universal motor.

Under these conditions, before filling the tank with water, the drum is forced into a program which is represented by the diagram in FIG. 4 which represents the variations, as a function of time t, of the speed V of rotation of the drum. Between the instants t₂ and t₂, the drum is made to rotate at a slightly increasing speed so that at time t₂ it reaches a speed of rotation of the order of 100 revolutions per minute. This first phase aims to distribute the laundry evenly in the drum in order to avoid unbalance, which is dangerous for the machine.

Between the instants t₂ and t₃ the drum rotates at the constant speed V₂₃ of the order of 100 revolutions per minute. During this phase, the acceleration being zero, the driving torque is equal to the friction torque C _f1 . The current absorbed by the motor thus has a relatively low effective intensity I _v23 (FIG. 5, which represents the variations of the effective intensity Ieff as a function of time t).

Between times t₃ and t₄, the rotation of the drum is accelerated, at a constant and determined value. The drive torque has a significantly higher value. It follows of course that the effective intensity I _v34 (Figure 5) of the current absorbed by the motor is higher. Then, between instants t₄ and t₅ the speed of drum rotation is kept constant at a value of the order of 500 to 800 revolutions per minute. In this last phase, the drive torque is only equal to the torque necessary to overcome friction.

   Dans cette formule I₃₄ est l'intensité efficace du courant électrique traversant le moteur d'entraînement du tambour entre les instants t₃ et t₄ et C_{f 34} est le couple de frottement, également entre les instants t₃ et t₄. K, I_o et l'accélération $\frac{\text{dω}}{\text{dt}}$

sont des constantes imposées lors de la construction de la machine; elles sent donc connues. I₃₄ est mesuré par exemple en déterminant la tension aux bornes d'une résistance en série avec le moteur. C_{f 34} n'est pas mesurable directement; dans le cas présent on estime que C_{f 34} est la moyenne arithmétique entre le couple de frottement C_{f 23}, entre les instants t₂ et t₃, et le couple de frottement C_{f 45} entre les instants t₄ et t₅. En d'autres termes :

   C_{f 23} et C_{f 45} sont aisément mesurables par les intensités I₂₃ et I₄₅ des courants parcourant le moteur universel entre les instants respectivement t₂ et t₃ et t₄ et t₅.Given formulas (2) and (3) above, we deduce the value of the moment of inertia L:

In this formula I₃₄ is the effective intensity of the electric current passing through the drum drive motor between times t inst and t₄ and C _{f 34} is the friction torque, also between times t₃ and t₄. K, I _o and acceleration $\frac{\text{from}}{\text{dt}}$

are constants imposed during the construction of the machine; they therefore feel known. I₃₄ is measured for example by determining the voltage across a resistor in series with the motor. C _{f 34} is not directly measurable; in the present case it is estimated that C _{f 34} is the arithmetic mean between the friction couple C _{f 23} , between the instants t₂ and t₃, and the friction couple C _{f 45} between the instants t₄ and t₅. In other words:

C _{f 23} and C _{f 45} are easily measurable by the intensities I₂₃ and I₄₅ of the currents flowing through the universal motor between the times t respectivement and t₃ and t₄ and t₅ respectively.

However, this quantity C _{f 34} is practically constant. It follows that in formula (4) above the moment of inertia L depends practically only on the intensity I ₃₄. In other words the intensity I₃ ₃ is a relatively faithful representation of the load of laundry in the drum.

In the diagram of FIG. 6, the variations of this intensity I₃₄ are represented as a function of the mass. Curve E in solid lines corresponds to terry cloth while curve D in lines interrupted corresponds to cotton or synthetic linen. As we can see at the same intensity I _{M 34} corresponds to three kilograms of terry cloth or four kilograms of cotton or synthetic linen.

On the other hand, as shown in FIG. 7, the curve of variation of the intensity I₃₄ as a function of the load of linen (that is to say the percentage of volume of the drum occupied by the linen) is the same curve F independent of the type of linen. It can be seen that for the intensity I _{M 34} corresponding to three kilos of terry cloth or four kilos of cotton or synthetic linen, this volume represents 70% of that of the drum.

Thus, as we have already seen, the intensity I₃₄ cannot represent the type of linen introduced into the drum. It is only the amount of water absorbed by the laundry that, in combination with the load, gives an indication of the type of laundry. At full load (100%) the terry cloth absorbs 16 liters of water, the cotton cloth 10 liters of water and the synthetic cloth 3 liters of water. It is therefore sufficient to make the ratio between the quantity of water absorbed and the intensity I₃ ₄ to obtain a precise indication of the type of laundry. The program contained in the microprocessor provided for controlling the machine can thus choose the operating parameters of the various organs to adapt the program to the type of laundry: engine timing, number of rinses, washing temperature, spin speed and also amount of water used for each wash and each rinse.

In the simplest case, two types of program are provided, one which corresponds to cotton linen or terry linen and the other to synthetic linen, which makes it possible to mix terry linen with cotton linen.

To measure the volume of water absorbed by the dry linen, the side wall II of the tank 10 has, opposite the bottom 30 of the drum 12 (FIG. 3), an opening 31 sealed through, by means of a seal 32, by a bowl cylindrical 33 open inside the tank and closed by a bottom 34 in its part external to the tank. This last part has a cylindrical sleeve 35 with a horizontal axis parallel to the vertical wall 11, and therefore perpendicular to the axis of the cylindrical bowl 33, which tightly connects two diametrically opposite openings 36 and 37 (FIG. 3a) of the cylindrical wall of the bowl. Thus the external surface of the sleeve 35 can bathe in water while the interior of this sleeve is isolated from water. Inside the sleeve 35 is arranged a thermistor 38 connected to a power source (not shown) having a sufficient voltage to heat this thermistor by Joule effect. The thickness of the wall of the sleeve 35 is small so that the thermistor 38 can be in good thermal contact with the water 15. When the sleeve 35 is not in contact with the water, due to Joule heating , the temperature of the thermistor 38 is higher than the ambient temperature and the temperature of the water. When the water reaches the sleeve 35 the temperature of the thermistor 38 drops and its resistance varies; this variation in resistance is used to detect the arrival of water at level 40 where the sleeve 35 is located, that is to say at a low height h, for example of the order of 1.5 centimeters, above the bottom 30 of the drum. In this example, the diameter of the drum being between 40 and 50 cm, the height h represents approximately 3% of the diameter of the drum.

Between the start of the opening of the solenoid valve 16 and the moment when the free surface of the water reaches level 40, a time t elapses which is measured for example using the microprocessor mentioned above. During this filling the drum 12 is stationary. During this phase the linen 14 practically does not absorb water because of the low height of the level 40 above the bottom 30. During a second phase the drum is rotated, preferably at a speed of 30 rpm - lower than the speed of 50 rpm for washing or rinsing - so that the entire periphery of the laundry is bathed in water. This cloth absorbs water and the free surface of the water 15 descends below level 40 to level 41; this state is shown in FIG. 2. Under these conditions the temperature of the thermistor 38 rises and its resistance varies; this new variation is used to indicate that the free surface is below level 40 and thus to order a new opening of the solenoid valve 16 which has been previously closed. The solenoid valve 16 is closed again when the water rises to level 40. The drum is then further rotated so that the laundry is even more soaked. The water level drops again and the solenoid valve 16 is opened again. The sum of the times t 'of opening the solenoid valve 16 after its first closing is thus measured. This sum of times represents the amount of water added, that is to say that which has been absorbed by the laundry. The measurement of the durations t 'is interrupted when the free surface of the water remains at level 40; for this purpose, the microprocessor is programmed to consider the filling completed, the laundry being completely soaked with water, when the free surface remains at level 40 about two minutes after the last closing of the solenoid valve 16.

il en résulte que le volume d'eau absorbé par le linge est :

$$\text{V = q Σ t' =}\frac{\text{Vo}}{\text{ t}}\text{Σ t' (6)}$$

   Dans cette formule Σ t' représente la somme des durées t'.If V _o is the volume of water contained in the tank when the free surface is at level 40, the flow q of the solenoid valve 16 is:

$$\text{q =}\frac{\text{Vo}}{\text{t}}\text{;}$$

it follows that the volume of water absorbed by the laundry is:

$$\text{V = q Σ t '=}\frac{\text{Vo}}{\text{t}}\text{Σ t '(6)}$$

In this formula Σ t 'represents the sum of the durations t'.

The arrangement of the thermistor 38 in the bowl 33 set back from the vertical wall 11 and distant from the solenoid valve 16, protects this thermistor against erroneous detections of the arrival of water at level 40. In fact, the thermistor is distant from the trajectory of the water drops coming from the impact of the water leaving the solenoid valve against the water already filling the tank. In addition, it is protected against turbulence. The sleeve 35 contributes to this result.

Of course, the measurement of the moment of inertia of the dry laundry is carried out prior to the measurement of the durations t and t '.

As a variant, instead of a thermistor, a bimetallic strip is used to control the opening and closing of the solenoid valve 16.

Claims (15)

1. Washing machine with automatic determination of the laundry load in the drum, characterized in that for determining this load it comprises a means for determining the moment of inertion of the laundry with respect to the axis (20) of rotation of this drum, which comprises a means for driving the drum at a constant acceleration (t₃, t₄) and a means for measuring the driving torque of the drum during said acceleration.
2. Washing machine according to claim 1, characterized in that the means for driving the drum at a constant acceleration operates before the filling up with water.
3. Washing machine according to claim 1 or 2, characterized in that the drum being driven by an electric motor of the universal type, and, for measuring the driving torque it comprises a means for measuring the intensity of the electric current flowing through said motor.
4. Washing machine according to claim 1, 2 or 3, characterized in that it comprises a means for enabling the drum to turn at a slowly increasing velocity before it turns with said constant acceleration in order to uniformly distribute the laundry within said drum.
5. Washing machine according to one of the claims 1 to 4, characterized in that it comprises a means for enabling the drum to turn at a constant velocity (V₂₃) before its rotation at a constant acceleration, said drum being also driven at an other constant velocity (V₄₅) after the rotation at constant acceleration, said driving torques being determined in the course of said two rotations at constant velocity, and a calculating means provided for performing a mean value between there two torques, this mean value being considered as the friction torque for the calculation or the driving torque.
6. Washing machine according to one of the preceding claims, characterized in that, for automatically determining the type of laundry introduced in the machine as well as selecting the washing program, it further comprises a means for measuring the water quantity absorbed by dry or substantially dry laundry (14a), the washing program being sensitive to the ratio between the quantity of the absorbed water and the load.
7. Washing machine according to claim 6, characterized in that, being of the type with a drum (12) turning within a tank (10),it comprises, for measuring the quantity of the water absorbed by the dry laundry, a means for interrupting the supply of water when the free surface of this latter reaches a predetermined level (40) which is located slightly above the bottom (30) of the drum, and a means for measuring the time of opening of the electrovalve (16) of the water supply, so that the free surface returns to said predetermined level and that the laundry is imbibed with water.
8. Washing machine according to claim 7, characterized in that it comprises a means for measuring the time of opening of the electrovalve (16), so that the free surface of the water in the tank reaches the predetermined level (40) before moistening the laundry in order to determine the throughput of said electrovalve.
9. Washing machine according to claim 7 or 8, characterized in that it comprises a temperature sensitive element (38) such as a thermistor secured to a wall (11) of the tank (10) of the washing machine, this element being heated such that, on the one hand it experiences a temperature decrease when it is reached by the water, so as to actuate stopping of the filling up, and on the other hand a temperature increase when the water level falls, so as to actuate a repeated filling up.
10. Washing machine according to claim 9, characterized in that the temperature sensitive element (38) is a thermistor, which is also used for measuring the temperature of the water during washing.
11. Washing machine according to claim 9 or 10, characterized in that the temperature sensitive element (38) is disposed at a low heigth (h) above the bottom (30) of the drum (12) of the washing machine.
12. Washing machine according to one of the preceding claims 9 to 11, characterized in that the temperature sensitive element (38) is disposed in a coating (33, 35) which protects it against the water splashes during filling up.
13. Washing machine according to one of the claims 6 to 12, characterized in that the means for measuring the water quantity absorbed by the dry laundry delivers a ternary signal indicating that the laundry is of one of the three following types: sponge, cotton, synthetic.
14. Washing machine according to one of the claims 6 to 12, characterized in that the means for measuring the water quantity absorbed by dry laundry delivers a binary signal indicating that the laundry is either of the synthetic type or of the cotton and/or sponge type.
15. Washing machine according to one of the preceding claims, characterized in that the means for determining the moment of inertia comprises a microprocessor.

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