EP0351276B1 - Method for detecting failures in a laundry drier, and laundry drier using this method - Google Patents

Description

The present invention relates to a method for detecting faults in a dryer, and to a dryer implementing this method.

Safety in a known dryer is often ensured by means of thermal relays which cut off the electrical supply to its heating elements or to its motors in the event of overheating, and by controlling a maximum admissible temperature of the air in its air outlet duct in order to cut off its heating and put the appliance in the cooling phase where the laundry is brewed without being heated, when such a temperature is exceeded.

The dryer described in document DE-A-3 436 342 has a device for measuring variations in humidity in the drum during the operating cycle. By means of this measurement faults can be detected.

The operation of this safety device in a known dryer occurs in most cases without the user being aware of it. When the electrical supply to the heating elements or to the motors is automatically cut off due to overheating and restored after they have cooled down, no information of these incidents is clearly brought to the attention of the user. Furthermore, a user who was not present at the time of these incidents can hardly be aware of the malfunction of this dryer and continues to use it in poor conditions which risk causing damage to the constituent parts.

The object of the present invention to avoid these drawbacks is an efficient and economical method for detecting and identifying faults in a dryer. It also relates to a dryer implementing this process. The dryer signals faults that have occurred and controls its operation accordingly.

According to the invention a method for detecting faults in a dryer fitted with a clothes drum, resistors electric heaters and an air circulation fan, is characterized in that it includes measurements of air temperatures at the air outlet duct and at predetermined times in the operating cycle of this dryer, determination of the values of the measured temperature variations, and identification of faults by selective recognition of the abnormal values of these temperature variations taking into account these instants of measurement of these temperatures, in the dryer operating cycle -laundry

The invention is applicable both to tumble dryers where the air leaving their laundry drum is discharged outside, and to tumble dryers in which the air leaving their laundry drum is recycled. i.e. dehumidified and then returned to their drying air circuit. In order to better understand the invention, an exemplary embodiment of it is described below, illustrated by a single appended drawing annexed schematically and partially to a dryer where the air leaving its washing drum is evacuated outside.

The dryer 1 illustrated comprises a rotary laundry drum 2, an air inlet duct 3 for a stream of drying air conveyed by a fan 4 and heated, to a predetermined temperature, by electric heating resistors 5 , an air outlet duct 6 provided with a filter 7 which retains in particular linen fluff. The laundry drum 2 is rotated by an electric motor 8.

When the dryer 1 is started, the drum 2 rotates and lifts the laundry to be dried 9 while a stream of hot air at a predetermined temperature 10 is sent through the air intake duct 3 in drum 2 to dry the laundry. The air 11 leaving the laundry drum 2 being cooled air and charged with humidity, is guided by the air outlet duct 6 to be evacuated to the outside.

When a final humidity threshold H of the laundry 9 chosen as the end of drying condition is reached, the electrical supply to the heating resistors 5 is cut and the dryer 1 is put in the cooling phase of the laundry 9 where the motor 8 and the fan 4 continue to operate to rotate the drum 2 and lift the laundry 9 and send a stream of fresh air into the drum 2 in order to accelerate the cooling of the linen 9. At the end of this cooling phase, the dryer 1 is stopped, the drying of the linen 9 ends and the linen 9 is dried in accordance with the criteria chosen by the user. The good drying result is usually obtained by normal operation of the dryer 1.

However, mechanical or electrical incidents could occur and disrupt this normal operation of the dryer 1 and compromise this good result of drying the laundry 9. A heating failure results in poorly dried laundry. A ventilation fault caused, for example, by a blocked fan 4 or by a blocked air outlet duct 6 risks exposing the laundry to an excessively high temperature. Uninterrupted or uncontrollable heating during a cooling phase of the laundry 9 leads to dangerous overheating of the drying air and damage to the laundry. Safety thermal relays or control thermostats mounted in the dryer 1 could to a certain extent limit or prevent damage caused by malfunctions in operation, control or equipment, but are still insufficient as means to lead to proper use. of the dryer, this is already recalled in a previous paragraph.

It is thus advantageous that these mechanical and electrical failures or incidents in a dryer are detected, identified, to the knowledge of the user and / or used for effective control of the dryer 1.

According to the invention, a method for detecting faults in a dryer comprises measurements of the air temperatures at the air outlet duct of the dryer and at predetermined times in the operating cycle of this dryer. dryer, a determination of the values of the measured temperature variations, and an identification of faults by a selective recognition of the abnormal values of these temperature variations taking into account these instants of measurement of these temperatures in the dryer operating cycle laundry.

In the course of a normal operation of a dryer 1, the air temperature at the outlet duct 6 rises rapidly, during a first phase where the wet laundry and the mechanical structure of the dryer are heated from a relatively low initial outlet temperature (Ti) (<25 ° C) or after an initial temperature drop to a minimum (Tmin) up to an equilibrium temperature (Te) corresponding to the start of a second phase or phase of water extraction during which the temperature follows a slow rise to a value Tf from which the temperature rises again rapidly in a third phase or phase of overdrying. Normally the power supply to the heating resistors 5 is cut off quickly after the start of this third phase or overdrying phase and a cooling phase of the laundry 9 is triggered, to avoid any deterioration of the laundry 9 by a current of air having a temperature too high.

According to the invention are carried out at the air outlet duct 6 and in the first phase or initial phase of the operating cycle of the dryer 1, measurements of a minimum detected air temperature Tmin, d '' an air temperature T₁ at a predetermined instant t₁, of the order of six to twelve minutes after the detection of Tmin, of an air temperature T₂ at a predetermined instant t₂ of the order of ten minutes after the measurement of T₁, and determinations of the values of the temperature variations T₁ - Tmin and T₂ - T₁.

These temperature variations form the basis for identifying certain failures of the dryer in the initial or first phase of the appliance's operating cycle. Indeed if T₁ - Tmin is negative (or zero) (T₁ - Tmin <O). This abnormal drop in temperature indicates an absence of heating, that is to say a heating failure. If T₁ - Tmin is positive and greater than Tv, Tv being a typical temperature difference of the dryer considered of the order of approximately 5 ° C (Tv <T₁ - Tmin), this normal increase in temperature indicates normal operation of the dryer 1.

If T₁ - Tmin is positive but less than about Tv (O <T₁ - Tmin <Tv), this rise in temperature turns out to be abnormally low and indicates either a heavy load in damp cloth to be dried in the drum 2 or too low a tension electrical supply to the heating resistors 5, ie a ventilation fault caused by a stop or blockage of the fan 4. In the latter case, the heated air is not in normal circulation state, the temperature rise in the duct input 10 is fast and the thermal protection relay for the heating resistors 5 operates and automatically cuts off the electrical supply to the latter. By thermal inertia, the temperature of the air in the air outlet duct 6 rises slightly by Δ Tv, ΔTv depending on the type of dryer and being approximately 3 to 5 ° C between T₁ and Tmin and then slowly decreases. These two cases are distinguished from each other by an examination of the temperature variation T₂ - T₁.

If T₂ - T₁ is positive (T₂ - T₁> 0), this normal temperature increase indicates that either the drying air resumes normal circulation in the dryer 1 after a stagnant start due to a temporary barrier consisting of too heavy load of laundry in drum 2 (0 <T₁ - Tmin <Tv) or the mains voltage is low and therefore the operation of dryer 1 is normal.

If T₂ - T₁ is negative or zero (T₂ - T₁ ≦ O) this abnormal drop in temperature confirms a ventilation fault caused by the fan 4 stopping (0 <T₁ - Tmin <Tv).

Thus the measurements of T₁ - Tmin and T₂ - T₁ make it possible to identify a heating failure (T₁ - Tmin <0) a ventilation fault caused by a blockage or an untimely stop fan 4 (0 <T₁ - Tmin <Tv and T₂ - T₁ <0) in the first phase of a dryer operating cycle.

According to the invention are also carried out at the air outlet duct 6 and during the operating cycle of the dryer 1 air temperature measurements Tj periodically every tn seconds where tn is l 'order of several seconds, and determinations of the values of the temperature variations Tj - T (j - 1).

If Tj - T (j - 1) is positive, this normal increase in temperature indicates normal operation of the dryers.

If Tj - T (j - 1) is negative, this abnormal drop in temperatures indicates either a momentary poor circulation of the drying air due to a temporary barrier consisting of moving laundry occupying in the drum 2 an obstruction arrangement. , either an opening of the dryer door leading to the operation of a safety relay which cuts the heating, or a normal phase of cooling of the linen triggered after the moment when a final humidity threshold H of the selected linen is reached either a heating failure or an obstruction of the air outlet duct 6.

For the opening of the dryer door, the identification is made by scanning the state of a door microswitch, this microswitch being open if the door is open and in the case of a normal cooling phase. the identification follows from the determination of the reaching of the final humidity threshold H controlled by the dryer control circuit.

est effectué pendant un temps tp de dix minutes environ par exemple.To distinguish the other cases listed above, check the slope $$\frac{\text{ΔT}}{\text{tp}}$$

is carried out for a time tp of about ten minutes for example.

est d'abord négatif et ensuite positif, il s'agit d'une mauvaise circulation momentanée de l'air de séchage due au linge en mouvement qui occupe dans le tambour 2 une disposition d'obstruction.Yes $$\frac{\text{ΔT}}{\text{tp}}$$

is first negative and then positive, it is a momentary poor circulation of the drying air due to the moving laundry which occupies in the drum 2 an obstruction arrangement.

reste anormalement négatif et

est supérieur à un seuil S de variation de température par unité de temps, par exemple 1°C par minute $$\text{(}\frac{\text{ΔT}}{\text{tp}}\text{> S)}$$

pendant un temps tp de dix minutes environ, S dépendant du sèche-linge, il s'agit soit d'une panne de chauffage soit d'une obstruction de la gaine de sortie d'air 6 lesquelles peuvent être distinguées l'une de l'autre par un examen supplémentaire. Pour cela, une température T₃ de l'air est effectuée au bout d'un temps t₃ de l'ordre de quinze minutes (typique du sèche-linge considéré) après une coupure du circuit de chauffage et un maintien de la ventilation, puis une température T₄ de l'air est mesurée au bout d'un temps t₄ environ cinq minutes (typique du sèche-linge considéré) après une refermeture du circuit de chauffage et enfin une variation T₄ - T₃ est déterminée.Yes $$\frac{\text{ΔT}}{\text{tp}}$$

remains abnormally negative and

East greater than a temperature variation threshold S per unit of time, for example 1 ° C. per minute $$\text{((}\frac{\text{ΔT}}{\text{tp}}\text{> S)}$$

for a time tp of about ten minutes, S depending on the dryer, it is either a heating failure or an obstruction of the air outlet duct 6 which can be distinguished from one of the other by further examination. For this, an air temperature T₃ is carried out after a time t₃ of the order of fifteen minutes (typical of the tumble dryer considered) after a cut in the heating circuit and a maintenance of the ventilation, then a temperature T₄ of the air is measured after a time t₄ about five minutes (typical of the dryer in question) after closing the heating circuit and finally a variation T₄ - T₃ is determined.

If T₄ - T₃ is negative or zero (T₄ - T₃ ≦ 0), it is a heating failure.

If T₄ - T₃ is positive (T₄ - T₃> 0), the air outlet duct 6 is obstructed.

,

et T₄ - T₃ permettent une identification de panne de chauffage et l'obstruction de la gaine de sortie d'air 6 au cours d'un cycle de fonctionnement du sèche-linge 1.Thus the measures of Tj - T (j - 1), $$\frac{\text{ΔT}}{\text{tp}}$$

,

and T₄ - T₃ allow identification of heating failure and obstruction of the air outlet duct 6 during an operating cycle of the dryer 1.

est anormalement positive $$\text{(}\frac{\text{ΔT}}{\text{tr}}\text{≧ 0),}$$

pour une durée minimale de deux minutes par exemple, cela indique une panne de de non interruption du chauffage, car le chauffage est toujours en marche bien que l'alimentation électrique des résistances chauffantes 5 doive être coupée par le programmateur du sèche-linge 1 qui passe en phase de refroidissement du linge ou dernière phase du cycle de fonctionnement du sèche-linge, la phase de séchage étant terminée.According to the invention are moreover carried out at the level of the air outlet duct 6 and subsequently when a final humidity threshold H chosen and programmed for the laundry is reached, measurements of the air temperature T₅ during the cooling phase every tr seconds where tr is around thirty seconds. Ts being the safety temperature, for example 70 ° C, if T₅ - Ts is abnormally positive or zero (T₅ - Ts ≧ O) or if $$\frac{\text{ΔT}}{\text{tr}}$$

is abnormally positive $$\text{((}\frac{\text{ΔT}}{\text{tr}}\text{≧ 0),}$$

for a minimum duration of two minutes for example, this indicates a failure of the heating not to be interrupted, because the heating is always on although the electric supply of the heating resistors 5 must be cut by the programmer of the dryer 1 which goes into the laundry cooling phase or the last phase of the dryer operation, the drying phase is over.

permettent d'identifier une panne de non interruption du chauffage ou panne due à un relais de commande d'alimentation électrique des résistances chauffantes 5, qui est bloqué ou en court-circuit dans une dernière phase du cycle de fonctionnement du sèche-linge.Thus the measurements of T₅ - Ts or of $$\frac{\text{ΔT}}{\text{tr}}$$

identify a failure of non-interruption of the heating or failure due to a control relay for the electric supply of the heating resistors 5, which is blocked or short-circuited in a last phase of the dryer operating cycle.

In the example illustrated, the dryer 1 which implements the fault detection method described in the preceding paragraphs comprises a temperature sensor of a known type 14 which, disposed in the air outlet duct 6 of the drum 2, operates to enter the temperatures of the air flowing therein and a control circuit 15 provided with an electronic card 16 using a microprocessor which ensures temperature measurements, recording of the data entered, determinations of temperature variations at from these data, an identification of faults according to the above process, a storage of dryer operating programs, preset values such as the safety temperature Ts, the threshold S of temperature variations per unit of the time, selected humidity thresholds for the end of drying H of the laundry, and performs a control of the organs of the dryer 1, an execution of the operating programs cho isis, an interruption of these following the detected faults and a signaling of these faults. This signaling can be carried out by light or sound means or clear display means.

The dryer 1 comprises indicator lights, not shown, constituted by diodes to indicate or display the operation or the stopping of the line dryer 1 and / or of its organs and the nature of the faults detected. In the example illustrated in FIG. 2, three aligned diodes 21, 22, 23 were used for displaying the detected faults.

During operation of the dryer 1, if in the first phase or initial phase of its operating cycle, a heating failure is detected, the selected operating program is interrupted by the control circuit 15 which stops the dryer because there is no need to leave the appliance running without heating, and this heating failure is indicated by an illumination of the first two 21 and 22 of the three diodes, represented in a / in FIG. 2.

In the event that a ventilation fault caused by an inadvertent blocking or stopping of the fan 4 is detected, the control circuit 15 cuts the electrical supply to the heating resistors 5 or stops the dryer to prevent overheating and repetitive operation of these under the control of its thermal safety relay, and signals this failure by lighting two end diodes 21, 23 of the three diodes shown in b / in FIG. 2.

mesurée et déterminée, est négative et supérieure à un seuil de variation de températures par unité de temps, il y a soit une panne de chauffage soit une obstruction de la gaine de sortie d'air 6, le circuit de commande 15 peut signaler cette situation par un éclairage de deux dernières 22 et 23 des trois diodes, représentées en c/ dans la figure 2.During the dryer 1 operating cycle, if $$\frac{\text{Δ T}}{\text{tp}}$$

measured and determined, is negative and greater than a temperature variation threshold per unit of time, there is either a heating failure or an obstruction of the air outlet duct 6, the control circuit 15 can signal this situation by illumination of the last two 22 and 23 of the three diodes, represented in c / in FIG. 2.

If an obstruction of the air outlet duct 6 is detected, the control circuit 15 cuts the electrical supply to the heating resistors 5 or stops the dryer 1 and signals this failure by lighting the three diodes 21, 22, 23 shown in d / in Figure 2.

If a non-interruption of the heating is detected during the cooling phase of the laundry or the last phase of the dryer operating cycle, the control circuit 15 keeps the fan 4 operating even after the end of the normal laundry cooling phase. to avoid any damage to the laundry by too high a temperature, and signals this failure of non-interruption of the heating by a flashing of the three diodes 21, 22, 23 represented in e / in Figure 2.

The operational safety of the dryer 1 of the invention is thus achieved in a more advanced manner than that of known dryers, which not only makes it possible to effectively put the laundry 9 away from any damage from thermal origin but also to obtain an appreciable economy by a rational use of the device, and a good drying result.

Claims (9)

1. A method for the detection of faults in a laundry dryer (1) provided with a washing drum (2), with electrical heating elements (5) and with a fan (4) for the circulation of the air, characterised in that it comprises measurements of the temperature of the air (T₁, T₂, T₃, T₄, T₅ Tmin and Tj) at the level of the air outlet casing (6) and at predetermined instants (t₁, t₂, t₃ and t₄) of the operating cycle of the washing machine, an ascertainment of the values of the variations in the measured temperatures (Tj - T(j - 1), T₁ - Tmin, T₂ - T₁, T₄ - T₃ and T₅ - Ts) and an identification of the faults by selectively recognising abnormal values of such variations in temperature taking into account the instants at which said temperatures are measured, in the operating cycle of the washing machine (1).

2. The method as claimed in claim 1, characterised in that it comprises measurements, at the level of the outlet case (6) for the air and during the first phase of the operating cycle of the washing machine (1), of a minimum air temperature detected of Tmin, at a predetermined instant t₁ of the order of six to twelve minutes after the detection of the Tmin, of a temperature of the air T₂ at a predetermined instant t₂, of the order of ten minutes after the measurement T₁, and ascertainment of values of variations in the temperature T₁ - Tmin and T₂ - T₁ in order to identify a fault in the heating and of a fault in the air circulation in this first phase of the cycle of operation of the washing machine (1).

3. The method as claimed in claim 1 or in claim 2, characterised in that it comprises measurements, at the level of the outlet case (6) for the air and during the cycle of operation of the washing machine (1), of the temperature of the air Tj periodically every tn seconds where tn is of the order of several seconds, measurements of the temperature of the air T₃ at the end a time t₃, of the order of fifteen minutes after turning off the heating and continuation of the air circulation, and of the temperature of the air T₄ at the end of a time t₄, of the order of five minutes after turning on the heating again and continuation of the air circulation and ascertainment of the values of the variations in temperature Tj -T(j - 1), T₄ - T₃ and of ΔT/tp, |ΔT/tp| during a time tp of approximately ten minutes in order to identify a fault in the heating and of a blockage of the air outlet case (6) during a cycle of operation of the washing machine (1).

4. The method as claimed in any one of the preceding claims 1 through 3, characterised in that it comprises measurement of the temperature of the air Ts every tr seconds, for instance every thirty seconds, at the level of the air outlet case (6) and after the time when a final dampness threshold H selected for the washing has been reached, of an interval of time greater than approximately two minutes and ascertainment of the values of variation of the temperatures T₅ - Ts, where ts is a security temperature, of the order of 70° C, selected and recorded or stored, and of ΔT/tr for approximately two minutes in order to identify a fault in a last phase or washing cooling phase in the operating cycle of the washing machine (1).

5. The method as claimed in claim 2, characterised in that it comprises identification of a heating fault during a first phase of a cycle of operating of the washing machine (1) by recognising the fact that T₁ - Tmin is negative or zero (T₁ - Tmin ≦ 0), and of a fault in the air circulation caused by the fan (4) stopping in a cycle of a first phase of operation by recognition of the fact that T₁ - Tmin is positive and is less than or equal to Tv, where Tv is a temperature offset dependent on the washing machine, of the order of 5° C (0 < T₁ - Tmin ≦ Tv) and T₂ - T₁ is negative or zero (T₂ - T₁ ≦ 0).

6. The method as claimed in claim 2, characterised in that it comprises identification of a fault in the heating during an operating cycle of the washing machine (1) by recognition of the fact that Tj - T(j -1) is negative (Tj - T(j - 1 < 0), that ΔT/tp is negative (ΔT/tp < 0) and |ΔT/tp| is greater than a threshold S of variation in temperature in a unit of time (ΔT/tp > S) during a time tp of approximately ten minutes, S being dependent on the washing machine and being approximately 1° C per minute and that T₄ - T₃ is negative or zero (T₄ - T₃ ≦ 0) and of the blockage of the air outlet case (6) during a cycle of operation by recognising the fact that Tj - T(j - 1) is negative (Tj - T(j - 1) < 0), that ΔT/tp is negative and |ΔT/tp| is greater than a thereshold S of temperature variation for a unit of time (|ΔT/tp| > S) during a time tp of approximately ten minute and that T₄ - T₃ is positive (T₄ - T₃ > 0).

7. The method as claimed in claim 4, characterised in that it comprises identifying a fault involving failure to turn off the heating during a last phase or cooling phase of the washing of the operating cycle of the washing machine (1) by recognising the fact that T₅ - Ts is positive or zero (T₅ - T_s ≧ 0) or ΔT/tr is positive (ΔT/tr > 0) during a minimum time of approximately two minutes.

8. A laundry dryer for performing the method as claimed in any one of the preceding claims 1 through 7, characterised in that it comprises a temperature sensor (14) arranged in an air outlet case (6) of a washing drum (2) and performing detection of the temperatures of the air circulating therethrough and a control circuit (15) provided with an electronic circuit board (16) utilised a microprocessor for the measurement of the temperatures, for recording the detected data, for the measurements of the variations in temperature on the basis of such data, for storing the operating program, for pre-established temperature values of the security temperature Ts, for the threshold S of variation of the temperature for a unit of time, for dampness thresholds selected for the end of drying H of the washing, for control of the parts of the washing machine, for running operating programs as selected, for turning off of these programs following faults detected and illuminating, audible or color signaling means indicating such faults.

9. The laundry dryer as claimed in claim 8, characterised in that for illuminating indication of the faults it comprises three aligned diodes (21, 22 and 23) of which the two first ones (21 and 22) are lit up for a heating fault, the two end ones (21 and 23) are lit up for a fault in the air circulation owing to stoppage of the fan (4), the two last ones (22 and 23) are lit up for a fault either in the heating or because of an obstruction in the air outlet case (6), all three diodes (21, 22 and 23) being lit up for a blockage of the air outlet (6), all three being caused to blink if there is a failure to turn off the heating.

Images