The present invention relates to a laundry washing machine with an electronic device for sensing the motion of the wash assembly due to the dynamic unbalance of the wash laundry drum assembly, and to the relative operating method.
More specifically, the present invention relates to a home laundry washing machine or combination washing machine-drier equipped with a device for evaluating a dynamic unbalance parameter related to the torque and speed acting on the wash assembly of the machine as a result of dynamic unbalance effects, and for accordingly activating or not the spin stage; to which the following description refers purely by way of example.
Home washing machines are known to comprise a casing, a laundry wash assembly comprising a cylindrical tub connected in floating manner to casing by suspension devices, a laundry drum mounted inside the tub to rotate freely about a longitudinal axis of rotation; and an electric motor connected mechanically to laundry drum by a transmission system to rotate laundry drum about longitudinal axis of rotation inside tub.
It is important to point out that the term “laundry drum assembly” will be intended to mean the assembly comprising the laundry drum, the laundry arranged into the laundry drum, and all the rotating parts of a transmission system used to impress the rotating motion to the laundry drum, i.e. pulleys, transmission shafts, and rotor of the electric motor.
In addition home washing machines comprises electronic control devices for measuring a physical parameter related to unbalance of the laundry drum assembly caused by random distribution of the laundry inside the laundry drum of the wash assembly, and accordingly determining potentially critical overall unbalance of the laundry drum assembly.
The main purpose of such devices is to achieve a predetermined spin speed of the laundry drum inside the wash assembly without producing unbalance of the laundry drum assembly over and above a maximum permissible threshold, which poses various problems in the machine, such as: collision of the wash assembly with the machine casing, and/or severe vibration resulting in a high noise level, and/or partial deformation of the laundry drum, and/or mechanical stress of the drum supporting members, i.e. bearings, dampers, springs, inside the wash assembly.
Unbalance of the laundry drum assembly of a washing machine caused by random distribution of the laundry inside the laundry drum can be divided substantially into two unbalance components, each associated with a respective distribution pattern of the laundry inside the laundry drum, and with a given rotation of the laundry drum caused by the distribution pattern.
More specifically, a first theoretical unbalance component—known as static unbalance and shown in the
More specifically, in the first distribution pattern, mass MS is located inside laundry drum T with its barycentre BMS aligned vertically with the barycentre BTS of wash assembly; and, as laundry drum T rotates, the first theoretical distribution pattern of static mass MS produces a substantially cylindrical rotation C (shown by the dash line) of the longitudinal axis L of laundry drum T with respect to its rest position. In other words, the cylindrical component of rotation of longitudinal axis L of laundry drum T is mainly associated with the “static unbalance” component of the laundry.
The second unbalance component—known as “dynamic unbalance” (shown schematically in FIG. 2)—is associated with a second laundry distribution pattern represented by two masses MAD and MPD, which are equal in weight, and are located opposite each other with respect to a vertical axis through the barycentre BTD of wash assembly; and, as laundry drum T rotates, the distribution pattern of the two masses MAD and MPD produces a substantially conical rotation of longitudinal axis L with respect to its rest position. In this case, projection of the rotation of longitudinal axis L in a plane perpendicular to longitudinal axis L in non-rotation conditions is defined by an ellipse E (shown by a dash line in
In other words, the conical component of rotation of longitudinal axis L of laundry drum T with respect to its rest position is mainly associated with the “dynamic unbalance” component of the laundry.
Though efficient, known control devices have the major drawback of determining unbalance of the laundry drum assembly solely on the basis of “static unbalance” as described above, i.e. associated solely with the “cylindrical component” of rotation of the longitudinal axis of the laundry drum assembly (
Known control devices, in fact, determine unbalance of the laundry drum assembly by processing the fluctuation in speed or torque acting in the wash assembly and imparted by its electric drive motor for regulating the rotating speed. Fluctuation in speed or torque, however, is related mainly to static unbalance, and provides no useful information concerning dynamic unbalance, which, being produced by a distribution pattern defined by two opposite masses of equal weight, produces weak fluctuation in the speed or torque imparted to the laundry drum assembly by the electric motor and therefore it cannot be determined using known control devices of the type described above.
It is an object of the present invention, therefore, to provide a laundry washing machine equipped with a device for sensing the motion of the wash assembly due to the “dynamic” unbalance of a wash laundry drum assembly, so as to prevent spin speed from being attained when “dynamic” unbalance exceeds a given threshold jeopardizing the washing machine.
According to the present invention, there is provided a method of operating a washing machine, as claimed in Claim 1 and preferably, though not necessarily, in any one of the Claims depending directly or indirectly on Claim 1.
According to the present invention, there is also provided a washing machine as claimed in Claim 8 and preferably, though not necessarily, in any one of the Claims depending directly or indirectly on Claim 8.
According to the present invention, there is also provided an electronic control device for sensing the motion of the wash assembly due to the dynamic unbalance of a laundry drum assembly of a washing machine, as claimed in Claim 9.
According to the present invention, there is also provided a software product loadable into a memory of processing means, as claimed in Claim 10.
A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:
With reference to
Laundry drum 6 has a front opening 7 closed selectively by a door (not shown) hinged to casing 2; and wash assembly 3 comprises an electric motor 8 connected mechanically to laundry drum 6 by a transmission system to rotate laundry drum 6, on command, about longitudinal axis of rotation L inside tub 4.
It is important to point out that term “laundry drum assembly” 15 will be intended to mean the assembly comprising the laundry drum 6, the laundry 16 located inside the laundry drum 6, and all the rotating parts of a transmission system used to impress the rotating motion to the laundry drum 6, comprising transmission shafts 18, and rotor 19 of the electric motor 8 (
Washing machine 1 also comprises a control device 9 for sensing the motion of the wash assembly 3 due to the dynamic unbalance of laundry drum assembly 15, and which comprises a regulating block 10 for regulating the rotation speed ω imparted to laundry drum 6 by the electric motor 8; a measuring block 11 for measuring the torque T imparted to laundry drum assembly 15 by an electric motor 8; and a measuring block 12 for measuring the total moment of inertia J of the laundry drum assembly 15.
Rotation speed regulating block 10, torque T measuring block 11, and inertia J measuring block 12 are known and therefore not described in detail, except to state that measuring block 12 measures inertia J as a function of torque T, and of the rotation speed ω imparted to the laundry drum 6 by the electric motor 8.
Control device 9 also comprises a processing and control block 14, which provides for implementing the method of sensing the motion of the wash assembly 3 due to the dynamic unbalance of laundry drum assembly 15 as described in detail below.
First, however, it should be pointed out that the dynamic unbalance of laundry drum assembly 15 (shown in
where d is the total dynamic unbalance of the laundry load (d=mRb, m is the dynamic mass MAD or MPD, R is the laundry drum radius, and b is the arm between the two dynamic masses MAD and MPD).
The first set of formulas 1) defines the rotations θy and θz of the wash assembly, measured in the principal axes of the elliptical cross section of the cone of motion (
The second set of formulas 2) defines the components Ty and Tz of the centrifugal torque produced by the dynamic unbalance, measured in the same principal axes of the ellipse.
The phase angle φ represents the phase shift of rotations with respect to the centrifugal torque: the phase angle φ defines the phase relation of the output (wash assembly rotations) with respect to the input (the rotating torque due to the dynamic unbalance of the load).
Angle δ defines the angular position of the vector of the centrifugal torque with respect to the frame of reference rotating with the drum.
The third formula 3) defines the additional torque acting on the laundry drum 6 due to the dynamic unbalance. In the present description, the additional torque is called “dynamic torque” Tdyn. The third formula 3) consists of two terms as indicated in formula 4): a quasi-static term TdynLF and a second-harmonics term TdynHF, both of which depend on the value of dynamic unbalance and on the square of rotation speed.
The quasi-static term TdynLF depends on ½·(θy0+θz0) which is the average value of the principal flare angles of the cone of motion. The quasi-static term TdynLF is therefore related to the conical motion of wash assembly 3.
The absolute value of the quasi-static part of the dynamic torque TdynLF grows up to a maximum value when passing through the wash assembly resonances showing conical motions of the laundry drum assembly. This maximum value is related to both the dynamic unbalance and the motion amplitude: larger maximum values correspond to larger dynamic unbalances and larger cones of motion (and vice-versa). When passing through resonances, the quasi-static part of the torque output by the electric motor will necessarily grow up to counterbalance the quasi-static term of the dynamic torque, which is a negative braking torque: physically this means that a larger power will be dissipated in the shock absorbers due to the larger amplitude in the conical motion of the wash assembly 3.
The second-harmonics term of formula 3) depends on ½·(θz0-θy0) which is related to the shape of the conical motion: if this value is zero, the cross section of the cone is a circle.
The formula 3) highlights that it is not possible to have a measure of the dynamic unbalance in Kg*m2 units, because both the terms TdynLF and TdynHF depend on the product of dynamic unbalance by a function of rotation amplitude (½·(θy0+θz0) and ½·(θz0−θy0)) and not only on one of them. However, by speeding up the washer, only if the absolute value of term TdynLF (or term TdynHF) is lower than a given threshold, an excessive dynamic unbalance in the spin phase can be avoided.
The present invention is based on the fact that it is possible to detect the effects of dynamic unbalance in terms of motion of the wash assembly 3 by reading the speed and torque signals output by the motor. If the motion of the wash assembly is sensed from the motor speed and torque signals, the dynamic unbalance can be taken under control. As a matter of fact, if the wash assembly is clamped as for shipping, this procedure cannot work because all the wash assembly movements are inhibited.
Research shows that a gradual increase in rotation speed ω of laundry drum 6 within a resonance speed range DFR of wash assembly 3 produces an increase in the amplitude of a component ALF, at a low frequency LF, of an unbalance function A=T−ω/dt.
More specifically, research shows the amplitude of the low-frequency component ALF, cleansed of a value associated with the friction torque TFRICTION to which laundry drum assembly 15 is subjected as the laundry drum 6 rotates, to be related to the quasi-static component TdynLF of dynamic unbalance torque Tdyn described above.
In the case in point, the increase in the amplitude of the component ALF at low frequency LF of unbalance function A=T−Jdω/dt within resonance frequency range DFR, cleansed of the friction torque TFRICTION of the laundry drum assembly 15, is related to the quasi-static component TdynLF of torque Tdyn to which laundry drum assembly 15 is subjected as a result of dynamic unbalance effects.
It should be pointed out that “low frequency” is intended to mean a frequency quite lower to the rotation frequency of laundry drum assembly 15. For example, a 120 rpm rotation speed of laundry drum assembly 15 corresponds to 2 Hz frequency and the low frequency LF is between 0 Hz and a few tenths of Hz.
With reference to the
Once the fixed laundry distribution pattern inside laundry drum 6 is achieved, rotation speed ω=ωDIST is maintained constant for a given time interval dt1, during which the method processes unbalance function A=T−Jdω/dt (block 110).
At this stage, the method filters the component of unbalance function A=T−Jdω/dt having a low frequency LF, to determine the amplitude of low-frequency component ALF (block 120).
It should be pointed out that, once rotation speed ωDIST is reached, angular acceleration of laundry drum 6 is practically zero, so the torque T imparted to laundry drum assembly 15 by electric motor 8 practically equals the torque T required to overcome the friction to which laundry drum assembly 15 is subjected as laundry drum 6 rotates, and the following equation applies: TFRICTION=ALF. Friction torque TFRICTION, in fact, equals the amplitude of the component ALF at low frequency LF of unbalance function A (block 130) (
At this point, regulating block 10 repeatedly increases rotation speed ω by a predetermined value Δω (block 140) to gradually cover a predetermined rotation speed range DFR of laundry drum 6, within which resonance of wash assembly 3 occurs. The resonance rotation speed range DRR may range between a minimum rotation speed ωRmin of about 120 rpm and a maximum rotation speed ωRMAX of about 250 rpm.
At each increase Δω, the method determines (block 150) whether current rotation speed ω is below a predetermined maximum rotation speed ωDYN, which is a predetermined value higher or equal to ωRMAX.
If current rotation speed ω is below predetermined maximum rotation speed ωDYN (YES output of block 150), the method performs the following steps in sequence: calculates unbalance function A=T−Jdω/dt at predetermined time intervals (block 160); filters component ALF at low frequency LF of unbalance function A=T−Jdω/dt (block 170); and determines a dynamic unbalance parameter corresponding to quasi-static component TdynLF of dynamic unbalance torque Tdyn (block 180) according to the equation:
TdynLF=ALF−TFRICTION
At this point, processing block 14 determines (block 190) whether the amplitude of the dynamic unbalance parameter, i.e. quasi-static component TdynLF, is below a predetermined threshold TdynLFMAX, which, in the case in point, is associated with an unacceptably hazardous dynamic unbalance condition of the laundry drum assembly 15, and in consequence an unacceptably motion of the wash assembly 3.
If the dynamic unbalance parameter, i.e. quasi-static component TdynLF, is below the predetermined threshold TdynLFMAX, (YES output of block 190), processing block 14 determines an acceptable dynamic unbalance condition and an acceptable motion of the wash assembly 3, again increases rotation speed ω by predetermined value Δω (block 140), and repeats the controls performed in blocks 150, 160, 170, 180 and 190 as described above.
Conversely, if the dynamic unbalance parameter, i.e. quasi-static component TdynLF, exceeds the predetermined threshold TdynLFMAX, (NO output of block 190), processing block 14 determines an unacceptably hazardous dynamic unbalance condition and in consequence an unacceptably motion of the wash assembly 3, commands regulating block 10 to immediately reduce rotation speed ω to achieve a random redistribution of the laundry inside laundry drum 6, and, once the laundry is redistributed, again performs the control method described above.
Dynamic unbalance control terminates when rotation speed ω of laundry drum 6 reaches a predetermined maximum rotation speed ωDYN (NO output of block 150) corresponding, for example, to ωRMAX.
In the event no unacceptable dynamic unbalance condition is detected over the whole resonance range DFR, the method authorizes the spin stage, and increases rotation speed ω to the wash cycle spin speed ωSPIN.
Washing machine 1 described above has the major advantage of specifically detecting the presence of the dynamic component of the unbalance of the laundry drum assembly as the laundry drum rotates, and so greatly reducing the risk of the wash assembly colliding with the machine casing at the spin stage.
Clearly, changes may be made to the washing machine and operating method as described and illustrated herein without, however, departing from the scope of the present invention, as defined in the accompanying Claims.
More specifically, in the
More specifically, research shows that, in resonance conditions of wash assembly 3, the amplitude of the component AHF at high frequency HF of the unbalance function A undergoes an increase ΔAHF with respect to a reference value AHFREF of the amplitude of component AHF measured in non-resonance conditions of the wash assembly 3 and at constant rotation speed. More specifically, increase ΔAHF in amplitude is related to the second harmonic TdynHF of dynamic unbalance torque Tdyn described above.
In the case in point, the increase in the amplitude of component AHF at high frequency HF of unbalance function A=T−Jdω/dt in the resonance frequency range DFR, cleansed of its initial reference value AHFREF, is related to the second harmonic TdynHF of the torque Tdyn to which laundry drum assembly 15 is subjected as a result of dynamic unbalance effects.
It should be pointed out that “high frequency” is intended to mean a frequency equal to twice the rotation frequency of laundry drum assembly 15. For example, a 240 rpm rotation speed corresponds to a rotation frequency of 4 Hz, so the high frequency to calculate second harmonic TdynHF is roughly 8 Hz.
With reference to the
Once the fixed laundry distribution on the inner wall of laundry drum 6 is achieved, rotation speed ω is maintained constant for a given time interval dt1, during which the method processes unbalance function A=T−Jdω/dt (block 210) (
At this stage, the method filters the component AHF of unbalance function A=T−Jdω/dt having a frequency equal to the predetermined high frequency HF (block 220).
At this point, the method assigns the filtered component AHF to reference value AHFREF (block 230). With reference to
At this point, regulating block 10 repeatedly increases rotation speed ω by a predetermined value Δω (block 240) within the predetermined rotation speed range DFR of laundry drum 6 in which resonance of wash assembly 3 occurs.
At each increase Δω, the method determines (block 250) whether current rotation speed ω is below the predetermined maximum rotation speed ωDYN.
If current rotation speed ω is below predetermined maximum rotation speed ωmm (YES output of block 250), the method performs the following steps in sequence: calculates unbalance function A=T−Jdω/dt at predetermined time intervals (block 260); and filters' the component AHF of unbalance function A=T−Jdω/dt having a frequency equal to the predetermined high frequency HF (block 270). It should be pointed out that component AHF represents the peak-to-peak amplitude of the oscillations of AHF during resonance.
At this point, processing block 14 determines a dynamic unbalance parameter, i.e. component TdynHF, according to the equation:
TdynHF=AHF−AHFREF
Processing block 14 determines (block 290) whether component TdynHF is below a predetermined maximum unbalance threshold TdynHFMAX, which, in the case in point, is associated with an unacceptably hazardous dynamic unbalance condition, and in consequence an unacceptably, motion of the wash assembly 3.
If the maximum unbalance parameter, i.e. component TdynHF, is below the predetermined maximum unbalance threshold TdynHFMAX (YES output of block 290), processing block 14 determines an acceptable dynamic unbalance condition and in consequence an acceptably motion of the wash assembly 3, again increases rotation speed ω by predetermined value Δω (block 240), and repeats the controls performed in blocks 250-260-270-280-290.
Conversely, if component TdynHF, exceeds the predetermined threshold TdynHFMAX, (NO output of block 290), processing block 14 determines an unacceptably hazardous dynamic unbalance condition and in consequence an unacceptably motion of the wash assembly 3, commands regulating block 10 to immediately reduce rotation speed ω to achieve a random redistribution of the laundry inside laundry drum 6, and repeats the control steps of blocks 200-290 described above.
Dynamic unbalance control terminates when rotation speed ω of laundry drum 6 reaches the predetermined maximum rotation speed ωDYN (NO output of block 250). In which case, the method, having detected no unacceptable dynamic unbalance condition when increasing rotation speed over the resonance rotation speed range DFR, authorizes the spin stage, and increases rotation speed ω to spin speed ωSPIN.
The method in the
Number | Date | Country | Kind |
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07118827 | Oct 2007 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/008551 | 10/10/2008 | WO | 00 | 8/23/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/049825 | 4/23/2009 | WO | A |
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6032494 | Tanigawa et al. | Mar 2000 | A |
20060242768 | Zhano et al. | Nov 2006 | A1 |
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19928657 | Dec 2000 | DE |
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International Search Report for PCT/EP2008/008551 (WO2009/049825), mailed Mar. 11, 2009. |
Number | Date | Country | |
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20100306926 A1 | Dec 2010 | US |