FR2697332A3 - Method for determining the unbalance of a drum of a loaded washing machine. - Google Patents

Abstract

Method for determining the unbalance of the loaded drum of a washing machine, in which after a phase of distributing the laundry before spinning, an unbalance measurement is carried out, characterized in that for the additional recording of the load of the drum after the laundry distribution phase, the setpoint speed is increased sharply and the deviations from the actual values are established in the load-dependent respective actual speed curve compared to the value of increased setpoint, are measured cyclically within a measurement window and are added together and in that from the sum a correction value is determined with which the unbalance measurement is corrected.

Description

i

  The invention relates to a method for determining

  mining the imbalance of the drum loaded with a washing machine, in which after a phase of distribution of the laundry,

  before a spin, an unbalance measurement is made.

  DE 3 039 315 Ai describes a regulation of the speed of rotation of an electric motor which rotates a mass with variable eccentricity of the center of gravity (washing machine drum) The regulation controls the current of the motor according to a setpoint value A sensor, recording the eccentricity force of the center of gravity, influences the setpoint of the speed of rotation The sensor records the motor current During an application spin (distribution phase of the washing) the unbalance measurement takes place If this is too large, this operation is interrupted If the unbalance is within acceptable values, the speed of

  drum rotation is increased to approximately 400 rpm.

  During this pre-spin phase, an unbalance measurement takes place in particular. The final spin speed is derived from this result. It is for example between 600 rpm and 1400 rpm, depending on the actual unbalance. An imbalance detection, depending on the motor current, is also described in EP O 275 862 Bl and in DE 26 20 464 But in these two cases it is not

  provision for adjusting the final spin speed as a function of the unbalance It is proposed, in the event of an unbalance limit value, to interrupt the spin or to return to the washing rotation speed.

  In US 3,152,462 there is described a control for the motor of a washing machine, the rotational speed of the motor being recorded by a tachometer generator and an unbalance sensor recording the mechanical impulses of the unbalance of the drum and supplying the signals corresponding to a computer command En

  in case of unbalance, the speed of rotation is reduced.

  US 3,674,419 also describes a washing machine control. An unbalance switch is provided, so as not to allow the rotation speed to rise to

the expected value.

  Mechanical unbalance detection, as described for example in US 3,152,462 and in

  US 3,674,419 is complex and unreliable in practice.

  DE 29 15 815 Ai describes a device intended to detect the speed of rotation and the unbalance of a group (washing drum) mounted oscillating in a box. On the driving disc of the washing drum there are provided markings which are read optically, in order to detect the unbalance It is thus possible to detect the rotation speed and the unbalance, which makes it possible to adapt the spin speed to the respective conditions But this device appears complex and requires a lot of

  care, because of the markings to be applied.

  GB 2 124 626 A also describes a motor control device for a washing machine. According to one embodiment (see Fig 4), provision is made to detect the

  load weight, by weight-dependent sensors.

  These sensors are complex and subject to failures in permanent service. In the embodiment according to FIG. 6, a tachometer generator is provided which records

  fluctuations in the speed of rotation, through

  diary of a group This unit controls the speed of

desired rotation.

  In the processes of the aforementioned type, according to the

  unbalance measured, it is set different speeds of esso-

  rage For large unbalances, lower spin speeds are set than for small unbalances The known measurement of unbalance gives a sufficient result

  precise when starting from a specific weight of the

  age (linen + water not yet spun) But in practice

  the drum is not always loaded with this weight; sou-

  wind, the load is lighter or heavier Depending on the moment of inertia of the drum masses, the result is different and the known measurement of unbalance does

  not give the optimal spin speed.

  A method of measuring unbalance is also described in DE 40 38 178 A1 The moment of inertia of the masses y

  is measured by engine shutdown and acceleration

  This results in unregulated operating phases. The object of the invention is to propose a method of the aforementioned type making it possible to record not only the unbalance caused by the eccentricity of the center of gravity of the masses when the axis is horizontal, but also the

respective load.

  According to the invention this object is achieved in that

  for additional recording of the respective charge

  drum after the laundry distribution phase,

  the setpoint speed is increased suddenly-

  and the differences in real values being established

  in the curve of the actual speed of rotation respec-

  tive, dependent on the load, in relation to the value of

  increased setpoint, are measured cyclically at the

  titer of a measurement window and are added and in that from the sum a correction value is determined with which the unbalance measurement is corrected. Also according to the invention, a) the setpoint speed of rotation increased suddenly after the laundry distribution phase is less than a spin speed, b) it is also possible that the setpoint speed of rotation after the increase is lowered to a compensation speed, c) finally, the compensation speed is

  equal to or greater than a speed of application of the laundry.

  The advantage of this process is that the moment of inertia

  respective masses of the drum is determined directly-

  ment, the moment of inertia of the masses depending on the weight of the laundry and the water retained by it as well as its distribution in the drum It is measured the overshoot of the actual speed of rotation, depending on the moment of inertia respective of the masses, by the set speed

suddenly increased.

  Since to determine the moment of inertia

  tie of the respective masses, its influence on the rotation speed of the drum is used and a detection of the rotation speed is in any case provided, a sensor

  additional is superfluous to detect the charge.

  In a variant of the invention, the first measurement window begins when, after the sudden increase in the set speed, the actual value of the speed exceeds the speed of

  setpoint and is set to a fixed duration.

  In a variant of the invention, after a stop time which is chosen to be long enough for the actual rotation speed to reach the set rotation speed, the unbalance measurement is carried out in a

  second measurement window, by recording fluctuations

  The speed of rotation depending on the unbalance Preferably the second measurement window consists of a constant time component and a variable time component and the variable time component is adjusted according to the correction value. thus in a simple way a correction of the unbalance measurement, depending on the respective load or the moment

respective inertia of the masses.

  Various other features of the invention

  appear moreover from the detailed description which

follows.

  An embodiment of the object of the invention is shown, by way of non-limiting example, to

attached drawings.

  Fig 1 is a block diagram of a machine

to wash.

  Fig 2 is a time diagram of the

drum rotation speed.

  Fig 3 is a diagram with test results,

  shown schematically for comparison.

  A washing machine comprises a washing drum 2 driven by a motor 1 On the drive shaft of the

  motor 1 is coupled to a tachometer generator 3.

  This provides an alternating voltage whose frequency

  is proportional to the engine speed.

  The frequency of this alternating voltage, evaluated with the motor-drum to linen transmission ratio,

  therefore represents the actual rotation speed of the drum.

  The fluctuations in the speed of rotation due to an imbalance of the laundry drum 2, lead to corresponding fluctuations in the output voltage of the generator

speed 3.

  The frequency of the output voltage of the tachometer generator 3 is applied to electronic

  rotation speed 4 digital, controlled by a micro-

  processor In the rotation speed electronics 4 the setpoint speeds of the drum are stored,

  necessary for the different washing programs.

  They are compared with the actual rotation speeds of the drum and the motor 1 is controlled accordingly by power electronics 5 The desired program can

  be selected using a program selector 6.

  The time diagram (see Fig 2) represents the transition zone between a washing phase and a phase

not shown.

  Curve 1 represents the variation of the actual rotation speed for a load of the washing drum 2 of 10 kg Curve It represents the variation of the actual rotation speed without load of the washing drum 2, the load being constituted in practice the weight of the laundry and the water absorbed by it

  loads of 10 kg and O kg are limit values.

  They were chosen to simplify In practice,

  the load values are between these quantities.

  Curve 3 represents the variation of the set value. Fig 2 shows in detail the following situation: A washing phase A is followed by a distribution phase of the laundry B During this, the rotation speed of the drum is approximately 82 rpm Ul During during the laundry distribution phase, the laundry must be applied stably against the inside perimeter of the laundry drum 2 After the application speed of the laundry Ul is reached, the set speed is suddenly increased, after a short phase C, up to U 2, for example 120 rpm For the load of 10 kg, the motor 1 needs a fairly long time, because of the fairly large moment of inertia of the masses, to accelerate up to the set speed, but then reaches a maximum actual speed U 3 higher (see curve I) than the speed without load (see

  curve II, with maximum actual speed U 4).

  After a certain time, the set speed returns to the value U 5, for example 100 rpm This value is greater than the speed of application of the linen Ul, because the linen must not come off the drum The time during which the set speed U 2 is given, is measured so that even for the greatest possible moment of mass inertia, the real speed

  confidently reaches the set speed U 2.

  After switching from U 2 to U 5, the drum 2 brakes without load faster than with load, due to

  its moment of mass inertia which is then lower.

  A first measurement window D is provided. This begins when the actual value of the speed of rotation exceeds the set value U 2 The duration of the measurement window D is set to a fixed value It is approximately 4 s The measurement window is about as long as the duration of the set speed U 2 On the

  figure 2, the measurement window is indicated for the run-

  be II In the case of curve I, the measurement window D is slightly shifted to the right The first measurement window D ends in any case before the

  actual speed does not reach the set speed U 5.

  In the first measurement window D, the difference in regulation of curve I or curve II with respect to the setpoint U 2 is integrated, taking into account

  of the sign This is done by cyclic measurement of the differences

  these rotational speeds in exceeding the variations in the speed of curve I or of curve II with respect to the set speed U 2 In this case,

  in principle, the surface a or b of the excess is recorded.

  respective The value obtained from the different

  rence of the surfaces b minus a, represents a dimension of the moment of inertia of the respective masses of the laundry drum 2 possibly loaded and is treated as a correction value, as described below Integration can also take into account the surfaces c, d, located in the measurement window D above the value of

setpoint U 5, curves I or II.

  At the first measurement window D follows a stop time E with the set speed U 5 The stop time E is determined experimentally so that within stop time E, including for the greatest possible moment of mass inertia, the target speed U 5 is reached with certainty for the measurement

unbalance.

  After the stop time E begins a second measurement window F The measurement window F consists of a constant time component F1 and a variable time component F 2 In the measurement window F is

  measured the respective unbalance of the loaded laundry drum 2.

  Due to the unbalanced distribution of the laundry, there is an additional torque, which causes the actual drum speed to periodically oscillate around the set speed U 5 The amplitude of these

  fluctuations is directly proportional to the importance

  tance of the unbalance, but inversely proportional to the moment of inertia of the masses of the laundry drum 2 with respect to the axis of rotation Figure 2 represents these fluctuations, determined by the unbalance, in the measurement window F These fluctuations of the unbalance also overlap curves I and II in the time ranges described above. The period of the unbalance fluctuations is much less than the constant component Fl of the measurement window F The unbalance is determined by integrating the value of the periodic fluctuations cited around the set speed. The duration of the variable time component F 2 of the measurement window F is adjusted as a function of the correction value, determined in the measurement window D The variable time component F 2 is therefore

  approximately proportional to the respective growth

  tive of the mass moment of inertia due to the load Un

  proportionality factor can be determined experimentally

  mentally The extension of the measurement window F by the variable time component F 2, depending on the respective moment of inertia of the masses, corresponds to a multiplication of the measurement result, determined within the constant time component Fl , by

a factor greater than 1.

  The result of the measurement, determined in the measurement window F, therefore also takes account of the respective moment of inertia of the masses. With this result it is possible to adjust the target speed, corresponding to the respective load or unbalance, a phase spin G following the measurement window F. FIG. 3 represents the unbalance M measured for different cases, as a function of the different unbalance weights U The curves I and II are shown for the case according to the invention in which the measurement window F has a variable component F 2 Curves III and IV are determined for the state of the art in which the measurement window F only has a constant time component Fl The curve I corresponds to the load of 10 kg Curve II applies to the case where there is no load Curve III applies to the case

  no load Curve IV corresponds to the load of 10 kg.

  As can be seen, the results of the unbalance measurement M deviate more and more from one another for curves III and IV according to the state of the art when the weight of the unbalance U increases, while the results of the unbalance M measurement of curves I and II are much closer when the weight of the unbalance U increases This means that the result of the unbalance measurement M according to the invention depends significantly less on

  the respective charge as in the prior art.

  The accuracy of the measurement can be improved by synchronizing the start of the mass inertia measurement with the unbalance position. For this purpose it is possible to use the angle of rotation of the washing drum for which the speed control changes from positive to negative

Or vice versa.

  By means of the described correction of the unbalance measurement by measuring the mass moment of inertia, on the whole it is possible to work with very low spin speeds, without the risk of

  overstress the bearings of the laundry drum.

Claims (6)

  1 Method for determining the unbalance of the drum loaded with a washing machine, in which after a phase of distribution of the laundry before a spin, there is a measurement of the unbalance, characterized in that for the additional recording of the respective load of the drum after the distribution phase of the laundry, the set speed is suddenly increased and the differences in actual values are established in the curve of the respective actual speed, depending on the load, relative to the increased set value, are measured cyclically inside a measurement window and are added and in that from the sum a correction value is determined with which the unbalance measurement is corrected.   2 Method according to claim 1, characterized in that the set speed of rotation increased suddenly after the distribution phase of the laundry, is   lower than a spin speed.   3 Method according to one of claims 1 or 2,   characterized in that the setpoint speed after the increase is lowered to a compensation speed. 4 Method according to claim 3, characterized   in that the compensation speed is equal to or greater than   higher than the speed at which the laundry is applied.   Method according to one of claims 1 to 4,   characterized in that the first measurement window (D) begins when, after the sudden increase in the set speed, the actual value of the speed exceeds the set speed and is set to a fixed duration.   6 Method according to one of claims 1 to 5,   characterized in that after a stop time (E) which is chosen to be long enough for the actual rotation speed to reach the target rotation speed, the unbalance measurement takes place in a second measurement window (F ), by recording fluctuations in the   rotation speed depending on the unbalance.   7 Method according to claim 6, characterized in that the second measurement window (F) consists   of a constant time component (Fl) and a compo-   variable time (F 2) and in that the variable time component (F 2) is adjusted according to the correction value.   8 Method according to one of claims 1 to 7,   characterized in that the instant of the variation of the target rotation speed is synchronized with the rotation angle of the drum for which the unbalance occurs.