Method and device for sensing unbalance-dependent movement phenomena in laundry drum

Abstract

The laundry in a rotating, obliquely mounted drum falls in the direction of action of gravitational force and therefore is no longer perpendicularly with respect to the axis of rotation of the drum, which results in an uneven distribution over the axial length of the drum, this leading to wobbling movement during the rotation of the drum that cannot be measured by conventional rotational sensor systems with their rigid attachment. In order to be able to counteract such movements on the drive side, these two further components of inertia have to be sensed orthogonally with respect to the main axis of inertia. For this purpose, the output signal of the rotational sensor, which signal indicates the rotational speed of the drum, experiences a variation in its output signal, the variation being dependent on the additional pitching and yawing movements of the laundry drum.

1 . A method for sensing unbalance-dependent movement phenomena in a laundry drum, which comprises the steps of: 
 measuring a rotational movement of the laundry drum; and    sensing angular accelerations occurring about an axis of inertia transversely with respect to an axis of rotation of the laundry drum, as a fluctuation in a measured value of a rotational speed through a displacement of a sensing element or actuator of a rotational sensor system.    
     
     
         2 . The method according to  claim 1 , which further comprises directing a displacement of the sensing element or the actuator of the rotational sensor system counter to an elastic restoring force and/or against at least one stop.  
     
     
         3 . The method according to  claim 1 , which further comprises sensing a fluctuation in an output signal of the rotational sensor system, the fluctuation being measured on account of the displacement, as a measure for a wobbling movement resulting from a combined pitching and yawing stress on the laundry drum.  
     
     
         4 . The method according to  claim 1 , which further comprises sensing relative changes in rotational speed in directions orthogonal to one another transversely with respect to the axis of rotation of the laundry drum.  
     
     
         5 . The method according to  claim 3 , which further comprises comparing a displacement-dependent change in the rotational speed with a rotational-speed signal from a further rotational sensor, the further rotational sensor is disposed rigidly or displaced elastically in relation to another axis of inertia.  
     
     
         6 . A device for sensing unbalance-dependent movement phenomena of a laundry drum of a laundry appliance, the device comprising: 
 a rotational sensor for measuring a rotational speed, said rotational sensor having: 
 an actuator rotating together with the laundry drum a; and  
 a sensing element fixed on the laundry appliance, said actuator and said sensing element being displaced relative to each other in or counter to a direction of rotation of said actuator.  
   
     
     
         7 . The device according to  claim 6 , further comprising: 
 at least one stop; and    an elastic restoring device, said actuator and said sensing element being displaced relative to each other counter to said elastic restoring device and/or against said at least one stop.    
     
     
         8 . The device according to  claim 7 , wherein: 
 said rotational sensor is a tachogenerator selected from the group consisting of voltage-generating tachogenerators and frequency-generating tachogenerators;    said sensing element having a stator coil system and an axis of rotation;    said tachogenerator having a permanent-magnet-type rotor being said actuator and rotating in said stator coil system of said sensing element; and    said sensing element having an eccentric distribution of masses with respect to said axis of rotation and can be rotated relative to a movement of said actuator counter to an elastic restoring force of said elastic restoring device and/or against said stop.    
     
     
         9 . The device according to  claim 7 , wherein: 
 said rotational sensor is a pulse generator outputting a pulse pattern;    said actuator is coupled in terms of rotation to the laundry drum; and    said sensing element being displaceable in a tangential direction with respect to a movement of said actuator counter to an elastic restoring force of said elastic restoring device and/or against said stop.    
     
     
         10 . The device according to  claim 8 , further comprising a nondisplaceable sensing element generating a first output frequency which is compared with a second output frequency of said sensing element being a displaceable sensing element.  
     
     
         11 . The device according to  claim 6 , wherein said sensing element is one of two sensing elements which are disposed pivoted orthogonally in relation to each other in a plane transverse to an axis of rotation of the laundry drum and can in each case be displaced, said two sensing elements output frequencies which are compared with each other.  
     
     
         12 . The device according to  claim 6 , wherein a drive of the laundry drum actively counteracts a wobbling movement thereof in accordance with a fluctuation in a rotational-speed signal from said rotational sensor by influencing the rotational speed, its gradient, by redistributing the laundry, or by torque fluctuations in the drive which are combined in proper phase.  
     
     
         13 . The device according to  claim 7 , wherein said at least one stop is one of two stops.  
     
     
         14 . The device according to  claim 9 , wherein said rotational sensor is an optoelectronic rotational sensor having a perforated or slotted diaphragm-type disc being provided as said actuator in a light barrier as said sensing element.