Patent Grant
7748067
The present invention relates to a laundry washing or to a laundry washing-dryer machine provided with means able to detect the unbalance mass and to balance the laundry load before the spinning phase.
It is well known during an operating program of laundry washing/drying machine to have one or more spinning phases, i.e. drum rotation phases at much higher speed than normally foreseen during the actual washing phases.
A basic element concerning said spinning phases is the risk of having an unbalanced laundry load with the clothes arranged unevenly inside the machine drum, i.e. accumulated in some definite areas and not available in other areas, so that during high speed rotation of the drum this unbalanced load condition may in fact cause remarkable oscillations or even the risk of a mechanical failure.
To this purpose the presently available washing machines (or washing-dryer machine) are provided with special control systems and methods to check whether the laundry load is evenly distributed or balanced inside the drum before the execution of the spinning phase, whereas in case of an unbalanced load the control system will remove the unbalance condition and provide for a new distribution phase or at least bring its amount back to acceptable limits to the machine structure.
The techniques to achieve this goal are mainly based on measuring the variation of the drum speed during the starting time of the spinning phase, and on correlating said speed variation to the unbalance level.
Indeed in a drum with an unbalanced load, moving at a constant rotation speed, the presence of an unbalanced load causes an increase in the drum speed in the time interval when the load is in the descending phase, and causes it to slow down when it is in the ascending phase.
As a result the drum speed takes an oscillatory behaviour around an average speed, well known to the man skilled in the art, and that for the sake of brevity is no further described.
According to the prior art, as in the exemplary patents EP 1342826, EP 0335790B1 and FR 2577949, such an oscillatory speed behaviour is then detected, processed and used in order to generate some procedures of drum rotation aimed to avoid or reduce the detected unbalance mass.
However said solution shows some drawbacks mainly based on the fact that the inertia moment of the loaded drum is not detected and then not considered in the processing and balancing procedure.
The inertia moment is however most important as it is well known that it directly affects the drum oscillation during the spinning phase; indeed in a drum having an unbalanced load, if the overall drum inertia is increased, i.e. if the laundry load is increased, the resulting oscillation during the spinning phase is reduced accordingly.
And on the contrary, if the inertia moment is reduced, that is if the laundry load is partly removed from the drum, maintaining the initial unbalance mass, then the speed oscillation increases.
Therefore some specific conditions can come true, wherein during the spinning phase the drum is subjected to an excessive oscillations that are prejudicial to the machine safety, even if an acceptable unbalance mass still exists.
A further method to control the unbalance mass is to directly measure the same unbalance mass, i.e. to measure the vibrations of the washing group by using one or more accelerometers.
Based on the measured values, a procedure is started which is aimed to redistribute the load according to known methods.
However this solution requires a not negligible computing power, expensive additional sensors, and moreover the unbalance mass evaluation can be done, with adequate confidence, only when the drum speed is so high that the laundry load is retained on the drum inner surface.
Largely known in the art is a different technique of controlling within proper limits the drum unbalance mass, and consisting in directly counterbalancing said unbalance mass; said technique is implemented by using adequate and generally circular conduits placed solidly with the drum and that are coaxial with it, and that contain some rotating or floating masses, typically water, or oil, or rollers or spheres; said masses are made to rotate by the drum rotation and soon they tend to distribute themselves in their own accord in a respective position able to at least partially balance the unbalance mass of the laundry load contained in the drum.
Said solutions are exemplified in the European patent appl. n. 96114328.6, in WO 93/23687 and also in the patents therein cited.
Said solutions of automatic re-balancing have shown effective from a functional point of view, but also burdensome and complicated in the construction, and furthermore they are also degrading the performances as the annular chambers, containing the balancing masses, take up a room that otherwise could have be taken by the laundry articles.
It would therefore be desirable, and is actually a main purpose of the present invention, to provide a clothes washing or washing-drying machine that will eliminate, or at least reduce the drawback of the unbalance mass produced by the uneven laundry distribution inside the drum during the spinning phases at high speed, considering also the actual inertia of the arm containing the laundry load.
According to a further purpose of the present invention this clothes washing machine (or washing-dryer machine) shall be able to be easy manufactured by using existing, ready available materials and techniques, and be competitive in its construction without suffering any alteration or reduction in the performance and reliability thereof.
These aims are reached in a washing machine (or in a washing-dryer machine) incorporating the characteristics as recited in the appended claims and including such operating modes as described below by mere way of non-limiting example with reference to the accompanying figures, in which:
The requirements of the distribution strategy according to the instant invention are now generally described, and the description of the operating modes and of the computations, aimed to define the needed parameters, are deferred further on.
In order to obtain a good balance of the laundry load it is needed:
As well known, the unbalance mass can be calculated from the static laundry unbalance mass; said static unbalance mass can be measured by making an energy balance on an integer number of drum turns.
Therefore an initial measurement of the inertia moment of the total drum (comprising drum, the whole laundry load and the motor), and the continuous measurements (i.e. lasting for the whole time interval of the distribution process) of the angular drum speed and of the motor torque have to be carried out.
In order to obtain a good balance of the laundry load it is needed to find out the best distribution strategy according to the unbalance mass, which of course can be varying during the spinning starting phase; moreover the said distribution strategy has to be able of automatically changing itself according to the changing of the unbalance mass.
The laundry movement inside the drum is random, not foreseeable and in the facts not controllable from the outside; then, if a favourable situation takes place, it is advisable to try to freeze it as quick as possible, by increasing the rotation speed.
From this point of view it is then useful to drive the drum at a suitably high speed, so that the laundry load is fully retained on the drum inner surface.
On the other side, with the increase of the rotation speed, the portion of the laundry load not yet retained against the drum inner surface tends to decrease, and that may prevent the reduction of the unbalance mass in excess with respect to the maximum allowed value for the unbalance mass.
As a conclusion, the speed control during the laundry distribution process has to duly take into account said two clashed elements; practically speaking, the rotational speed must be controlled in such a way to be the highest possibly, having taken into account that the possibility of eliminating the unbalance mass in excess (with respect to the maximum acceptable unbalance degree) shall not be excluded.
The requirements of the distribution strategy according to the instant invention are now explained.
The general equilibrium equation with reference to the rotational speed of the drum with the laundry load is:
wherein the various terms show the respective following meanings:
The overall inertia on the drum axis (JTOTAL) must be measured once and for all at the beginning of the laundry distribution process, as it is a value that is stable, when the laundry humidity is constant.
The friction torque on the drum axis (TFRICTION) takes into account all the frictions developed by the machine, comprising both the ball bearings and the gear friction, and those related to the laundry rubbing.
The elevation torque on the drum axis (TELEVATION) is the resistant torque due to the laundry not yet retained by the centrifugal force on the drum inner surface; indeed in its downwards motion the not yet retained laundry doesn't make any resisting torque, as it doesn't drags the drum with it, while it makes a restraining torque in its upwards motion.
The energy supplied by the motor to raise the laundry is then dispersed by friction in the warping motion of the laundry load (falling impact and rubbing due to the relative motion among the laundry articles). The elevation torque is then a negative moment, as the friction torque is.
The parameters used in the distributing procedure are the static unbalance mass (m) and the elevation torque (TELEVATION).
They can be obtained by using the given general equation to calculate an energy balance over an integer number of drum turns. Therefore an integration of the same equation between an initial angle θ1 and a final angle θ2=θ1+2πN, has to be calculated, N being an integer number.
As the resistant torque generated by the static unbalance mass −mgR·cos(ωt) shows a sinusoidal behaviour with respect to the drum rotation angle, then the unbalance mass amount can be estimated by the following equation, valid for any initial angle θ1:
In order to use the main equation that allows the instantaneous determination of the amount of the unbalance mass (m) and of the elevation torque (TELEVATION), it is requested to measure two parameters: the drum angular speed (ω), and the motor torque (TMOTOR).
However here it is intended that the relevant amounts are well known, as they can be easily detectable with known means and procedures; for instance by using a tachometer generator and measuring the current taken up by the motor, with respect to its phase; therefore their measurements and processing are no further discussed.
Distribution Strategy of the Laundry Load
The elevation torque (TELEVATION) can be referred as the parameter of the percentage of the laundry load not retained to the inner wall of the drum; if said moment is zero, the laundry articles are fully retained on the drum inner surface, while as much this parameter increases in its absolute amount (being it a negative amount) as the laundry load is allowed to move itself.
By using the correlation between the elevation torque and the mobility degree of the laundry load, it is possible to define an advantageous and effective strategy for the distribution process.
According to the above considerations, the procedure for starting the spinning phase without suffering an excessive unbalance mass will have to consider the following observations:
If all these facts are taken into account, it is concluded that the best distribution strategy consists in the adoption of a rotating drum speed during the whole distribution phase that be the maximum possible speed, however compatible with a laundry mobility degree good enough to allow the possibility of eliminating the unbalance mass in excess measured each time.
In order to implement such strategy and in order to control properly the target speed during the distribution process, the following condition must be implemented:
m−S<β·|TELEVATION|
In it, m represents the static unbalance mass measured at the actual time, while S gives the threshold, i.e. the maximum allowed limit for the unbalance mass; therefore m−S represents the unbalance mass in excess that is requested to compensate.
β is a suitably selected constant value.
If the check of the above given condition is positive (the condition is true), that means that the laundry articles have not been fully distributed on the drum wall, but a part of them are still “flying” inside it, due to the fact that the drum speed is too low. Therefore a limited increase of the drum speed is activated.
If the check of the above condition is negative, (the condition is not true), that means that the unbalance mass is too high, independently of the fact that the laundry articles are or not retained on the drum inner wall. Then a small decrease in the drum speed is activated, in order to separate a further portion of the laundry load from the drum inner wall and to reposition it in a more balanced way.
The optimum condition, that permits to start the spinning phase with a well balanced load, is implemented when the unbalance mass is low enough and, in the same time, the elevation torque is close enough to zero, (i.e. when the laundry load appears to be well distributed in the drum and with a left-over mobility close to zero).
That means that the following two conditions have to come true:
where TELEVATIONMAX is the maximum allowable amount for the absolute value of the elevation torque.
As a matter of facts, the distribution strategy must consist in that the spinning phase is allowed only after two basic conditions are implemented, i.e.:
Such strategy can be effectively understood, in the actual case of a washing machine (or a washing-dryer machine) just before the spinning phase, considering the logical flow-chart of
In order to simplify and to make easier the understanding of the invention, said logical flow-chart shows only the working modes of a logical and working kind that are essential to implement the invention; in the real situation however of a washing machine (or a washing-dryer machine) that actually implements the invention, it is needed and useful to introduce some further operations and logical functions; these are described in
In the flow-chart of
The flow-chart of
With reference to
The blocks of
Moreover the new blocks are easily recognized as their external perimeter is highlighted with a double line.
Now the meanings of the main blocks that have been added is explained shortly, as the reasons of their presence and the related working modes is easily guessed and understood by the man skilled in the art.
With reference to
It is then apparent that the instantaneous speed basically follows the progress of said target speed, as it is the latter which controls the time by time motor working.
Moreover it is to be noticed that at a certain time, T in the diagram, the actual speed tends to increase beyond its previous average amounts; in the facts at this time the spinning phase is started, as the two conditions 1 and 2, previously described, have been met.
It can be immediately verified that, at that time, the unbalance mass m takes its minimum amount and, in the same time, the elevation torque takes its minimum amount, in its absolute value.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04102927 | Jun 2004 | EP | regional |
This application is a divisional of U.S. application Ser. No. 11/140,393, filed on May 27, 2005 now abandoned which claims the benefit of European application Serial No. 04 102 927.3, filed on Jun. 24, 2004. These applications are incorporated in their entirety herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6418581 | Bruce et al. | Jul 2002 | B1 |
| 20030140427 | Yamamoto et al. | Jul 2003 | A1 |
| Number | Date | Country |
|---|---|---|
| 0335790 | Oct 1989 | EP |
| 1342826 | Sep 2003 | EP |
| 2577949 | Aug 1986 | FR |
| Number | Date | Country | |
|---|---|---|---|
| 20090151085 A1 | Jun 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11140393 | May 2005 | US |
| Child | 12371221 | US |
