EP0657576B1 - Automatically controlled washing machine - Google Patents

Description

The invention is based on a method for determining an undesired Braking the laundry drum during a spin section in one automatically controlled washing machine with a drive motor, the speed of which with a Speed control circuit adjustable on the basis of a phase control and can be determined according to target and actual speed values and which drives the Laundry drum with several different speeds for washing, rinsing and slingshots.

In a known washing machine of this type (DE 36 38 498 A1) is used for determination the presence of foam by means of a known for level determination Pressure sensor the pressure present in the so-called sump of the washing machine measured and deduced from this that foam was present or absent. It has but showed that also pressure surges on the residual water still present in the swamp act from the side of the drain pump, such a high level of Pretend suds container that no spin cycle will be operated would lead to the skidding being stopped. Hence this type of foam detection unsure. It also requires the simultaneous use of the pressure sensor at least one additional one for lye level detection and foam detection Switch that increases the amount of components.

From FR-A-2 639 661 a program-controlled washing machine is known, in which one compares the measured value for the actual speed with the comparison value for the target speed or the measured value for the load torque on the laundry drum with the predetermined comparison value for the target load torque in order to to determine the braking torque of the drum. In these cases, only comparisons between two parameters are provided. In addition, the comparison between load torques requires additional sensors on the drive or its suspension, because torque measurement is not possible in any other way.
This known solution for the detection of foam formation in the tub also has a decisive disadvantage: the increase in the drum speed in the range between about 220 and 400 min ^-1 is almost identical, regardless of whether there is foam in the tub or not. If, for example, only to take place, a comparison between the target speed and the actual speed according to the known washing machine, then you will have to wait with the detection of foam formation, exceeded until the desired speed 400 min ^-1. For then only arises a difference between the two speed values (desired and actual), because then the actual speed from 400 lags behind the target speed min ^-1.
In addition, speed deviations are at all possible due to fluctuations of variables that cannot be influenced, such as, for example, the mains voltage and the mains frequency of the motor supply, and also due to strong bearing friction, as occurs, for example, with high unbalances.

The invention is therefore based on the object of being able to reliably detect foam to be found in all spin speed ranges without additional components gets along.

a) Solldrehzahl,

b) lstdrehzahl und

c) eine belastungsabhängige elektrische Größe.

According to the invention, this object is achieved by a method in which the control circuit of the washing machine is supplied with a signal during a spin section which determines a measure of undesired braking of the laundry drum (for example due to foam formation) and the ratio of the following parameters of the drive motor operation to one another is:

a) target speed,

b) actual speed and

c) a load-dependent electrical quantity.

The speed values are electrical quantities in the Speed control circuit of a modern washing machine anyway and a load-dependent electrical quantity can also be an existing one in the speed control circuit Value for the motor current or the phase angle of the motor current, so that it is for the invention Foam detection no additional components requirement.

The inventive method is particularly advantageous Washer trained by the fact that when the Signals with a magnitude that indicate the presence of a the drum stops braking amount of foam that Spin drive of the drum at least for a limited Duration switched off is set up. During the switch-off period of the centrifugal drive, the foam at the bottom of the Suds container collapse. The remaining lye residues are according to a further advantageous development the washing machine according to the invention during the The centrifugal drive is switched off by a drain pump pumpable.

To accelerate the foam breakdown, according to another advantageous embodiment of the washing machine according to the invention while the centrifugal drive is switched off the drum is driven in reverse on the gentle cycle. The gentle cycle is regularly with such low speeds performed that the drum movement no further Creates foam, but smashes the existing foam bubbles.

If there is a large amount of foam, another advantageous one Training the washing machine according to the invention for effective Remedy, after finding a another rinse cycle can be initiated is. Great compactness or a large amount of foam each to a strong braking torque on the drum, the quite a bit from the above three parameters Security can also be assessed in its scope. Dependent on from the amount of foam determined in this way one or the other measure can be initiated become. Following such measures can also be initiated another rinse cycle in a particularly advantageous Way the further rinse cycle with an increased lye level be performed.

Using the diagrams shown in the drawing Motor speeds and motor current over time are the Dependencies on centrifuge sections and foam development clearly visible.

The diagrams in Figures 1 and 2 show the course of the Motor current i over time t and the associated drum speed n over time. Proportional to that shown Current through the drum drive motor is the leading edge angle, the as a control variable from the control circuit for the drum drive motor can be removed immediately can.

For all the diagrams shown, the same item of laundry has always been examined in a single washing machine. In the diagram in FIG. 1, the laundry item was rinsed well at the beginning of the spin section and without any residual surfactant content in the lye still present in the laundry. When the drive motor is switched on and accelerated to approximately 100 min ^-1 , a needle-like increase in the motor current up to 4.5 A can be observed, which then occurs at approximately 1.2 A. When accelerating further from 100 min ^-1 to approximately 240 min ^-1 , the needle-like increase in motor current i is already significantly smaller (up to approximately 2.4 A). Here, the laundry movement that has already been initiated reduces the inertia. At the idle speed of around 240 min ^-1 , the motor current falls below 1.4 A. During a ramp that now rises gently for the motor speed down to about 800 min ^-1 , the motor current only rises slowly above 1.5 A. When the drum speed remains at around 800 min ^-1 , the motor current drops back to around 1.5 A. After a brief switch-off current peak, the motor current drops back to 0 and the speed drops rapidly to 0 min ^-1 .

If the quiescent current measurement is more than 0 A, then lies the fact that when recording the current diagrams the Total power consumption of the washing machine was measured. The Current consumption without motor activation is only about 500 mA and is therefore compared to the high current consumption of the drive motor is negligible.

The laundry item observed for recording the diagram in FIG. 2 still contained foam-forming lye. Basically, the current curve in the diagram during the spin-up phase until it reaches about 220 min ^{-1 is} about the same as that in the diagram in FIG. 1. However, since there should already be some foam between the tub and the rotating laundry drum the level of current consumption during the speed plateau 100 min ^-1 and the drop in current after the needle tip when accelerating to about 220 min ^{-1 is} already significantly higher than in the corresponding sections in FIG. 2. First, the plateau of 220 min ^-1 also accelerates the laundry drum along a ramp up to about t = 2 min in the experiment according to FIG. 2, whereby this is obviously opposed by braking foam. This manifests itself in a sharp rise in the motor current to just over 4.5 A, which now reaches its power limit and can no longer accelerate the drum against the braking torque generated by the foam. The drum speed is therefore maintained at around 400 min ^-1 . This fact causes two significant disadvantages: On the one hand, the drum motor is often overloaded too much (for example, instead of 300W nominal power, an actual power consumption of 750W). As a result, the engine overheats and wears out prematurely. On the other hand, the laundry is often insufficiently dewatered at a reduced spin speed. In addition, further foam formation is intensified by the strong mechanical entry into the spun off lye by the spinning drum; foam control is thus made even more difficult.

After the drive is stopped, the motor current consequently drops and the laundry drum speed back to 0.

In the recordings for the diagrams in FIGS. 3 and 4, a control circuit according to the invention has been used for the control of the drive motor, which control circuit can be supplied with a signal which is a measure of undesired braking, e.g. B. by foam formation, the laundry drum. It can be seen that in the test carried out for the diagram in FIG. 3 — assuming the same amount of laundry and otherwise the same conditions — approximately the same results are obtained in the ratio of the respective speeds to the required motor current values. The earlier termination of the speed plateau between 700 and 800 min ^-1 at about 3 2/3 minutes in contrast to a little more than 4 minutes in the example in FIG. 1 is due to a program change which has nothing to do with any foam formation.

In contrast, Fig. 4 shows that the control circuit designed according to the invention breaks off the beginning of the spin section during the ascent ramp at a little above 400 min ^-1 , because the motor current had risen well above 4.5 A, and the speed which is set no longer corresponds to that in Fig. 3 apparent target course could follow. This can lead to an excessive load on the laundry drum due to external influences, for. B. closed by foam braking. To monitor this undesirable operating condition - as assumed in the diagrams - the increase in the motor current itself or the phase angle of the motor power supply and the ratio of the target speed to the actual speed can be observed.

According to advantageous developments of the invention this termination of the spin start another consequence be switched in the preceding program sequence. First of all, it can be important to use the centrifugal drive Turn the drum off at least for a limited period. It would be advantageous during the switch-off period of the centrifugal drive continue to run the washing machine drain pump, with it lye resulting from collapsing Foam continues to collect, immediately removed from the tub can be. Lye that is no longer in the tub remains, can no longer form further foam take part.

So that the foam formation in a subsequent Spin cycle should be avoided after finding a braking amount of foam in the tub at least another rinse cycle can be initiated. Another one Rinse cycle would further reduce the residual surfactant content in the lye and thus reduce the risk of renewed foaming. After completing the further rinse cycle, a new spin start attempt will be made. Upon need can such additional rinse cycles with an increased Lye level can be carried out.

Of particular value for comfortable operation of the Washing machine in which braking by detergent foam could be considered from the outset would be an order in the control circuit, which is the number of at Foam development aborted centrifuge attempts stores and from certain frequencies of such numbers for future treatment processes one the learned Experience based on the corresponding number of rinse cycles Manufacturer already installed number of rinse cycles adds from the start. However, it would be an advantage if after a set number of treatment processes always trying with the manufacturer installed number of rinse cycles is made to test whether the operator can control their behavior, e.g. by changing the detergent. Alternatively however, the control circuit can be designed in this way be that in principle the one already installed by the manufacturer Number of rinses and a spin start attempt be carried out, but then this first attempt at start-up a number corresponding to the learned experience of rinse cycles before the next spin start attempt is connected downstream.

Claims (9)

1. Method for ascertaining an undesired braking of the laundry drum during a spinning section in an automatically controlled washing machine with a drive motor, the rotational speed of which is settable by a rotational speed regulating circuit and is ascertainable in terms of target and actual rotational speed values and which serves for the drive of the laundry drum at several different rotational speeds for the washing, rinsing and spinning, characterised in that the control circuit of the washing machine has a signal fed to it during a spinning period, which signal is a measure of an undesired braking of the laundry drum and determined from the relationship to each other of the following parameters of the drive motor operation:

   a) target rotational speed,

   b) actual rotational speed and

   c) an electrical magnitude dependent on load.
2. Method with a rotational speed regulating circuit based on a phase-gating control, according to claim 1, characterised in that the electrical magnitude dependent on load is the phase-gating angle of the supply voltage of the drive motor.
3. Method with a rotational speed regulating circuit based on a chopper control, according to claim 1, characterised in that the electrical magnitude dependent on load is the current consumption of the drive motor.
4. Method according to claim 1, 2 or 3, characterised in that the spinning drive of the drum is switched off for at least a limited duration in the presence of the signal with a magnitude which permits the presence of a quantity of foam braking the drum to be deduced.
5. Method according to claim 4, characterised in that a washing solution pump continues to be driven whilst the spinning drive is switched off.
6. Method according to claim 4 or 5, characterised in that the drum is driven in reversing manner in overdrive whilst the spinning drive is switched off.
7. Method according to one of the claims 1 to 6, characterised in that at least one further rinsing run is initiated after ascertaining a braking quantity of foam.
8. Method according to claim 7, characterised in that the rinsing run and/or further rinsing runs are carried out with a higher washing solution level.
9. Method according to claim 7 or 8, characterised in that the number of attempts to start spinning is stored in an arrangement of the control circuit and a number of rinsing runs, which corresponds with the empirical value learned from certain frequencies of numbers of that kind, is for future treatment processes either added in advance to the number of rinsing runs, which is already installed at the manufacture, or installed before the next attempt to start spinning.

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