EP1900867A1

EP1900867A1 - Method for detecting pump faults in a washing machine

Info

Publication number: EP1900867A1
Application number: EP06120591A
Authority: EP
Inventors: Stefano Casagrande
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2006-09-13
Filing date: 2006-09-13
Publication date: 2008-03-19

Abstract

The present invention refers to a method for detecting pump faults in a washing machine (6) provided with a turbidity sensor (5) mounted on a measuring section of a conduit (3) which is in fluid communication with said pump (4). The present method is characterised by comprising the following steps: (A) when the pump (4) is switched off and said conduit (3) is empty, a first signal is provided indicative of a first turbidity measurement; (B) when the pump (4) is energized, a second signal is provided indicative of a second turbidity measurement; (C) calculating the difference between the first and the second signal and comparing such difference with a preset threshold value; (D) supplying a pump fault signal if said difference is lower than the preset threshold value.

Description

METHOD FOR DETECTING PUMP FAULTS IN A WASHING MACHINE

The present invention refers to a method for detecting pump faults in a washing machine.
Modern washing machines are provided with a washing liquor circulating system in which washing liquor discharged from the rotating drum at the bottom of the tub is fed back to the drum inner region by means of a pipeline having an outlet placed at an upper portion of the drum so as to drop the washing liquor on the laundry to be washed. The circulating system comprises a pump and a sensor device arranged on the pipeline respectively for moving the liquor and for detecting if liquor is actually circulating in the pipeline.
Such a washing machine is known from US 6,378,341 . In this machine the sensor device comprises a turbidity sensor, placed in a measuring section of the laundering water recirculation conduit, and a float designed as a valve disk provided with a stem protruding into the measuring section of the turbidity sensor when the volumetric flow in the conduit is absent or unable to lift the float.
According to US 6,378,341 disclosure, the sensing function detecting whether a fluid is circulating in the recirculation conduit results from the cooperation of the floating body movement within the conduit and the signal provided by the turbidity sensor. However, since the float is placed inside a conduit where detergent scale and lint can accumulate, it is possible that such float blocks after a number of washing cycles causing sensing errors or a complete absence of the sensing function. A fault of the sensing function compromises laundry washing results.
The aim of the present invention is therefore to solve the noted problems and thus providing a method for detecting pump faults having an improved reliability.
Another object of the present invention is to provide a method for detecting pump faults that does not require mechanical modifications of existing washing machines.
A further object of this invention is to provide a method for detecting pump faults which is suitable to sense whether a fluid circulation is in progress in a conduit without the need of any movable body.
Advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realised and attained as particularly pointed out in the appended claims.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate a possible embodiment of the invention and together with the description serve to explain the principles of the invention.
In the drawings:
Figure 1 shows schematically a washing machine provided with a turbidity sensor;
Figure 2 shows a graph representing turbidity sensor outputs for experimental measurements in an empty conduit and in a conduit in which a volumetric flow is in progress.
With reference to figure 1 the method according to the invention can be applied in a washing machine 6 comprising a drum 1 rotatably mounted within a tub 2 and further comprising a conduit 3 in fluid communication with a pump 4. Said conduit 3 conveys washing liquor to a drum inner region 7 suitable for receiving laundry to be washed. In figure 1, conduit 3 is in the form of a recirculating pipeline draining washing liquor from the bottom portion of the tub 2 and spraying the liquor on the laundry from a top portion of the tub 2.
A turbidity sensor 5 of known type is arranged in a region of the conduit 3 representing the measuring section of the turbidity sensor 5 and consisting of translucent material, so as a light beam transmitted by a transmitting part of the sensor 5 can pass through the conduit 3 to a receiving part of the sensor 5.
According to the present invention the method for detecting pump 4 faults is based on checking whether a flow is effectively occurring in conduit 3 when the pump 4 is energized. Such check is performed using signals provided by turbidity sensor 5 when pump 4 is in a first condition of rest, i.e. when it is switched off or not energized and when the pump 4 is in a second working condition, i.e. when it is energized.
In order not to alter the sensor 5 measurement when pump 4 is in a rest condition, the turbidity sensor 5 is preferably placed above the maximum level of washing liquor in the tub 2. However, for applying the present method in already existing washing machines provided with a turbidity sensor 5 in a position below said washing liquor level, it is sufficient ensuring that the sensor measurement, performed when the pump 4 is switched off, is done before draining water from the main water supply.
A first turbidity measurement is carried out by the sensor 5 when pump 4 is switched off and the conduit 3 is empty. Signal given by the sensor 5 is clearly not indicative of a fluid turbidity, but it corresponds to the condition in which there is no fluid circulation in progress within the conduit 3. A second signal is provided by turbidity sensor 5 after the pump 4 has been energized. If the pump 4 works correctly, a flow will occur in conduit 3 and the sensor 5 will give an indication of turbidity of the liquor circulating in the conduit 3. If the energized pump 4 does not effectively generate a flow in the conduit 3, the sensor 5 will provide a signal that can be considered equal to that provided in the first measurement taking into account also the sensor 5 measurement error.
Signal taken after the pump 4 has been energized is compared with the signal indicative of condition in which there is no fluid circulation in conduit 3 and the difference between such signals is calculated. Such difference is further compared with a preset threshold value indicative of the "not working state" of the pump 4. If the calculated difference is lower than the preset threshold value, a pump fault signal is supplied. A preferred threshold value is 0.01.
Figure 2 shows signals provided by a turbidity sensor 5 by varying the percentage of light beam emitted when the conduit 3 is empty and the pump 4 is switched off (Line A), and when a cleaned fluid flows within conduit 3 (Line B). The field between lines A and B defines the space in which a turbidity sensor measurement falls when a turbid fluid flows within conduit 3.
Even if the turbidity sensor 5 preferably provides a voltage signal as output, other forms of outputs are equivalently possible.
Conclusively it can be stated that the present method for detecting pump faults has an improved reliability and it does not require any modification in already existing washing machines to be applied.
The turbidity sensor 5 present in any case in modern washing machines is thus used not only for measuring turbidity during washing and rinsing cycles of the washing machine but also for controlling the operative state of a recirculation pump. It is consequently possible to avoid the use of a separate sensor element for controlling such pump.

Claims

Method for detecting pump faults in a washing machine (6) provided with a turbidity sensor (5) mounted on a measuring section of a conduit (3) which is in fluid communication with said pump (4), said method being characterised by comprising the following steps: (A) when the pump (4) is switched off and said conduit (3) is empty, providing a first signal indicative of a first turbidity measurement; (B) when the pump (4) is energized, providing a second signal indicative of a second turbidity measurement; (C) calculating the difference between the first and the second signal and comparing such difference with a preset threshold value; (D) supplying a pump fault signal if said difference is lower than the preset threshold value.
Method for detecting pump faults according to claim 1 wherein said preset threshold is 0.01.