FR2634232A1 - METHOD FOR DETECTING FAILURES IN A DRYER AND DRIER EMPLOYING SAID METHOD - Google Patents

Abstract

Method of detecting faults in a tumble dryer 1 provided with a laundry drum 2, electric heating resistors 5 and an air circulation fan 4, characterized in that it comprises temperature measurements of the air T1, T2, T3, T4, T5, Tmin, Tj at the level of the air outlet duct 6 and at predetermined times t1, t2, t3, t4 of the operating cycle of this dryer a determination of the values of the measured temperature variations Tj-T (d-1), T1 - Tmin, T2 - T1, T4 - T3, T5 - Ts and an identification of failures by selective recognition of the abnormal values of these temperature variations taking into account of these instants of measurement of these temperatures, in the operating cycle of the dryer 1. Dryer implementing this method comprising a temperature sensor 14, a control circuit 15 provided with an electronic card 16 using a microprocessor and light signaling diodes.

Description

-1 'to 2634232

  METHOD OF DETECTING FAILURES IN A

  DRIER AND DRYER EMPLOYING

WORK THIS METHOD

  The present invention relates to a method of detecting faults in a tumble dryer, and a tumble dryer

implementing this method.

  Safety in a known tumble dryer is often ensured by means of thermal relays which cut off the power supply of its heating elements or motors in the event of overheating, and by control of a maximum permissible air temperature in the event of overheating. its air outlet duct to cut off its heating and put the unit in phase of 1G cooling where the laundry is brewed without being heated, when

  exceeding such a temperature.

  The operation of this safety in a known tumble dryer occurs in most cases without the user noticing. Indeed, when the power supply of the heating elements or motors is automatically cut due to overheating and restored after cooling thereof, no information of these incidents is clearly made known to the user. Moreover, a user not present at the time of these incidents can hardly realize the malfunction of this dryer and continues to use it in poor conditions that may cause damage to the dryer.

constituent bodies.

  The object of the present invention to avoid these drawbacks is to provide an efficient and economical method of

  detection and identification of failures in a dryer.

  It also relates to a dryer using this method. The dryer reports failures that have occurred

  and controls its operation accordingly.

  According to the invention, a method for detecting faults in a tumble dryer equipped with a laundry drum, electric heating resistors and an air circulation fan, is characterized in that it comprises temperature measurements. air at the air outlet duct and at predetermined times in the operating cycle of the tumble dryer, determining the values of the measured temperature variations, and identifying failures by selective recognition abnormal values of these temperature variations taking into account these moments of measurement of these temperatures, in the operating cycle of the tumble dryer The invention is applicable both to tumble dryers or the air coming out of their laundry drum is discharged outside, only in the tumble dryers in which the air coming out of their clothes drum is recycled, that is to say dehumidified and then put back into their drying air circuit. To better understand the invention is described below an exemplary embodiment illustrated by a single drawing appended schematically and partially showing a tumble dryer o outgoing air

  from his laundry drum is evacuated outside.

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

  Linen 2 is rotated by an electric motor 8.

  When the tumble dryer 1 is turned on, the drum 2 turns and lifts the laundry to be dried 9 while a stream of hot air at a predetermined temperature is passed through the air inlet duct 3 in the drum 2 to dry the laundry. The air 11 leaving the laundry drum 2 being a cooled air and loaded with moisture, is guided by the sheath of

  air outlet 6 to be evacuated outside.

  When a final moisture threshold H of the laundry 9 selected as the end of drying condition is reached, the power supply of the heating resistors 5 is cut off and the dryer 1 is put in the cooling phase of the laundry 9 o 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 to accelerate the cooling of the laundry 9. At the end of this cooling phase the dryer 1 is stopped, drying of the laundry 9 ends and the laundry 9 'is dried according to the criteria chosen by the user. The good result of drying is usually obtained by normal operation of the

1 tumble dryer 1.

  However mechanical or electrical incidents could occur and disrupt this normal operation of the dryer 1 and compromise the good result of drying the laundry 9. A heating failure leads to a badly dried laundry. A lack of ventilation caused for example by a blocked fan 4 or an air outlet duct 6 clogged may expose the laundry hazardously to a temperature too high. Uninterrupted or uncontrollable heating in a cooling phase of the laundry 9 leads to dangerous overheating of the drying air and damage to the laundry. Thermal safety relays or control thermostats mounted in the dryer 1 could to some extent limit or prevent damage caused by operational, control or equipment failures but are still insufficient as a means of achieving proper use. of the dryer, this is already recalled in a

previous paragraph.

  It is thus advantageous that these mechanical or electrical failures or incidents in a tumble 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 of detecting faults in a tumble dryer comprises measuring air temperatures at the air outlet duct of the dryer and at predetermined times in the operating cycle of that dryer. dryer, a determination of the values of the variations of the measured temperatures, and an identification of the failures by a selective recognition of the abnormal values of these temperature variations taking into account these moments of measurement of these temperatures in the operating cycle of the dryer. machine. In a course of normal operation of a dryer 1, the temperature of the air at. level of 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 a decrease of initial temperature to a minimum (Tmin) to an equilibrium temperature (Te) corresponding to the beginning 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 quickly in a third phase or phase of drying out. Normally the power supply of the heating resistors 5 is cut off rapidly after the beginning of this third phase or overdrying phase and a cooling phase of the laundry 9 is triggered, to prevent any deterioration of the laundry 9 by a stream of air having

a temperature too high.

  According to the invention, at the level of 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 temperature of the air Tmin, d a temperature of the air T1 at a predetermined time 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 of T1, and determinations of the values of

  temperature variations T1 - Tmin and T2 - T1.

  These temperature variations constitute bases for an identification of certain breakdowns of the dryer in the initial phase or first phase of the operating cycle of the apparatus. Indeed if T1 - Tmin is negative (or zero) (T1 -Tmin <O). This abnormal drop in temperature indicates

  a lack of heating, that is to say a heating failure.

  If T - Tmin is positive and higher than Tv, Tv is a temperature difference typical of the tumble dryer of about 5 C (Tv <T1 - Tmin), this normal increase of

  temperature indicates normal operation of the dryer 1.

  If T - Tmin is positive but less than Tv approximately (O <T1 - Tmin - Tv), this temperature rise is abnormally low and indicates either a high load in wet clothes to dry in the drum 2 or too low tension electrical supply of heating resistors 5 is a ventilation fault caused by a stop or blocking of the fan 4. In the latter case the heated air is not in normal circulation, the temperature rise in the duct input 10 is fast and the thermal relay for protecting the heating resistors 5 operates and automatically cuts off the power supply of the latter. By thermal inertia, the air temperature in the air outlet duct 6 rises slightly from A Tv, LTv depending on the type of dryer and being about 3 to 5 C between T1 and Tmin and then goes down slowly. These two cases are distinguished one from

  the other by examining the T2-T1 temperature variation.

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

  therefore the operation of the dryer 1 is normal.

  If T2 -T1 is negative or zero (T2 - T1 $ O) this abnormal temperature decrease confirms a defect of ventilation

  caused by a fan stop 4 (O <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 inadvertent shutdown of the fan 4 (O <T1 - Tmin <Tv and T2 - T1 <0) in the

  first phase of a cycle of operation of the dryer.

  According to the invention are furthermore carried out at the level of the air outlet duct 6 and during the operating cycle of the tumble dryer 1 of the air temperature measurements TJ periodically every tn seconds o tn is from order of several seconds, and determinations of

  values of temperature variations TJ - T (j - 1).

  If Tj - T (j - 1) is positive, this normal increase in temperature reflects normal operation of the tumble dryers. If Tj - T (J - 1) is negative, this abnormal decrease in temperature indicates either a temporary poor circulation of the drying air due to a temporary barrier constituted by moving clothes occupying in the drum 2 an obstruction arrangement , ie an opening of the dryer door causing operation of a safety relay which cuts off the heating, or a normal cooling phase of the laundry triggered after the moment when a final humidity threshold H chosen for the laundry is reached or a failure

  of heating, ie an obstruction of the air outlet duct 6.

  For the case of an opening of the door of the dryer the identification is done by scrutinizing the state of a door microswitch, this microswitch being open if the door is open and the case of a normal phase of cooling the identification follows from the determination of the threshold of moisture

  final H controlled by the control circuit of the dryer.

  To distinguish the other cases listed above an AT slope check is performed for a time tp of tp

10 minutes, for example.

  If AT 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 a

obstruction arrangement.

  If A T remains abnormally negative and T is tp tp greater than a threshold S of variation of temperature per unit of time, for example 1 C per minute (AT> S) for a time tp of approximately ten minutes, S depending on the dry -linge, it is either a heating failure or an obstruction of the air outlet duct 6 which can be distinguished from each other by additional examination. For this, a temperature T3 of the air is carried out after a time t3 of the order of fifteen minutes (typical of the dryer considered) after a cut of the heating circuit and a maintenance of the iC ventilation, then a temperature T4 of the air is measured after a time t4 approximately five minutes (typical of the tumble dryer considered) after a reclosing of the heating circuit and

  finally a variation T4 - T3 is determined.

  If T - T is negative or zero (T4 - T3 <0), then

4 34

a heating failure.

  If T - T is positive (T4 - T3> 0), the sheath of

4 34 3

air outlet 6 is obstructed.

  Thus the measurements Tj - T (j - 1), AT AT and T4 - T3 allow identification of heating failure and obstruction of the air outlet duct 6 during a

  operating cycle of the dryer 1.

  According to the invention are also carried out at the air outlet duct 6 and subsequently at the moment when a selected and programmed final humidity threshold H of the laundry is reached, air temperature measurements T5 during the cooling phase every tr seconds o tr is of the order of thirty seconds. Ts being the safety temperature, for example 700C, if T5-Ts is abnormally positive or zero (T-Ts> O) or if AT is abnormally AT 5 tr positive (AT 0), for a minimum duration of two minutes, for example this indicates a failure of non-interruption of the heating, because the heating is still running although the power supply of the heating resistors 5 must be cut off by the programmer-of the tumble dryer 1 which goes into the cooling phase of the laundry or last phase of the dryer's operating cycle, - the drying phase being completed. AT Thus, the measurements of T5-Ts or T make it possible to identify a failure of non-interruption of the heating or failure due to a relay for controlling the power supply of the heating resistors 5, which is blocked or short-circuited in a last phase of the dryer's operating cycle. In the example shown, the tumble dryer 1 which implements the failure detection method described in the preceding paragraphs comprises a known type of temperature sensor 14 which, disposed in the air outlet duct 6 of the drum 2, operates a capture of the temperatures of the circulating air and a control circuit 15 provided with an electronic card 16 using a microprocessor which provides temperature measurements, a recording of the data entered, determinations of the temperature variations to from these data, an identification of failures according to the above method, a storage of operating programs of the dryer, pre-established values such as the safety temperature Ts, the threshold S of temperature variations per unit of time, selected humidity thresholds at the end of drying H of the laundry, and performs a control of the organs of the dryer 1, a running of the selected operating programs is, an interruption thereof following the failures detected and a signaling of these failures. This signaling can be carried out by luminous means or

  sound or means of display in the clear.

  The dryer 1 comprises unrepresented LEDs consisting of diodes to signal or display the operation or the stoppage of the dryer 1 and / or its organs and nature of the faults detected. In the example illustrated in FIG. 2, three aligned diodes 21, 22, 23 have been

  used to display detected faults.

  During operation of the dryer 1, if in the first phase or initial phase of its operating cycle, a heating panine is detected, the selected operating program is interrupted by the control circuit 15 which stops the dryer -linge because it is useless to leave the unit running without heating, and this heating failure is signaled by a lighting of two first 21

  and 22 of the three diodes, shown in a / in Figure 2.

  In the case where a ventilation fault caused by blocking or inadvertent shutdown of the fan 4 is detected, the control circuit 15 cuts off the power 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 reports this failure by a lighting of two end diodes 21, 23

  of the three diodes shown in b / in Figure 2.

  During the cycle of operation of the dryer 1, if at 1 fixed and determined, is negative and greater than a tp threshold of variation of temperatures per unit of time, there is either a heating failure or an obstruction of the duct. air outlet 6, the control circuit 15 can signal this situation by lighting two last 22 and 23 of the three

  diodes, shown in c / in Figure 2.

  If an obstruction of the air outlet duct 6 is detected, the control circuit 15 cuts off the power supply of the heating resistors 5 or stops the dryer 1 and signals this failure by a lighting of the three

  diodes 21, 22, 23 shown in d / in Figure 2.

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

Figure 2.

  The operating safety of the tumble dryer i of the invention is thus carried out in a more extensive manner than that of known tumble dryers, which not only allows the laundry to be effectively put on. thermal origin but also to obtain an appreciable saving by a rational use of the apparatus, and a

good drying result.

1I

Claims (9)

  1. Method of detecting faults in a tumble dryer (1) provided with a clothes drum (2), electric heating resistors (5) and a fan (4) for air circulation, characterized in that it includes measurements of air temperatures (T1, T2, T3, T4, T5, Tmin, Tj) at the air outlet duct (6) and at predetermined times (t1, t2, t3, t4) of the operating cycle of this tumble dryer, a determination of the values of the measured temperature variations (TJ - T (j - 1), T1 Tmin, T2 - T1, T4 - T3, T5 - Ts), and an identification of the failures by a selective recognition of the abnormal values of these temperature variations taking into account these moments of measurement of these temperatures, in the operating cycle of the tumble dryer (1).   2. Method according to claim 1, characterized in that it comprises measurements, at an air outlet duct (6) and in the first phase of the cycle of operation of the dryer (1), d a minimum detected temperature of the air Tmin, an air temperature T1 at a predetermined time t1, of the order of six to twelve minutes after the detection of the Tmin, an air temperature T2 at a predetermined time t2, of the order of ten minutes after the measurement of Ti, and determinations of the values of the temperature changes T1-Tmin and T2 T1, for the purpose of identifying a heating failure and a breakdown of ventilation in this first phase of the operating cycle of the tumble dryer (1).   3. Method according to one of claims 1 and 2,   characterized in that it comprises measurements, at the level of the air outlet sheath (6) and during the operating cycle of the dryer (1), of the air temperature Tj periodically every tn seconds where tn is of the order of several seconds, measurements of the air temperature T3 after a time t3, of the order of fifteen minutes after a cut of the heating and a maintenance of the ventilation, and the temperature of the air T4 after a time t4, of the order of five minutes after a reclosing of the heating and a maintenance of the ventilation, and determinations of the values of the temperature variations Tj - T (j - 1), T - T and AT | T during 4 3 -tp tp pedn a time tp of about ten minutes, in order to identify a heating failure and an obstruction of the air outlet duct (6) during a cycle operating system tumble dryer (1).   4. Method according to one of claims 1 to 3,   characterized in that it comprises measurements of the air temperature Ts every tr seconds, for example thirty seconds, at the level of the air outlet duct (6) and after the moment when a humidity threshold The final finish H selected from the laundry is reached, with a time interval of greater than about two minutes, and determinations of the values of the temperature variations T5 - Ts o Ts is a safety temperature, of the order of 70 C, chosen and recorded or stored, and AT for about two minutes, for an identification of a failure of non-interruption of heating in a last phase or cooling phase of the laundry of the   operating cycle of the dryer (1).   5. Method according to claim 2, characterized in that it comprises an identification of a heating failure in a first phase of an operating cycle of the dryer (1) by a recognition that T1 - Tmin is negative or zero (T1 -Tmin. <0), and a ventilation failure caused by a fan stop (4) in a first phase of an operating cycle by a recognition that T1 Tmin is positive and less than or equal to Tv o Tv is a temperature difference dependent on the dryer, of the order of 5 C (0 <T1 - Tmin <Tv) and T2 - T   is negative or zero (T2 - T1 <0).   6. Method according to claim 3, characterized in that it comprises an identification of a heating failure during a cycle of operation of the dryer-llnge (1) by recognition that TJ T (j - 1 ) is negative (Tj - T (j - 1 <O), than Negative Test (T) <O) and -TI is greater than a threshold S of temperature variation per unit of time (--T> S) during a time tp of about ten up minutes, S depending on the dryer and being about 10C per minute and that T4 - T3 is negative or zero (T - T <O) and an obstruction of the outlet duct 4 3 '   of air (6) during an operating cycle by recognizing that TJ - T (j - 1) is negative (TJ - T (J - 1) <O), that AT is negative and | tI is higher tp ItpT at a threshold S of temperature variation per unit time (T> S) for a time tp of ten minutes   approximately and that T4 -T3 is positive (T4 - T3> O).   7. Method according to claim 4, characterized in that it comprises an identification of a failure of non-interruption of the heating in a last phase or cooling phase of the laundry cycle of operation of the dryer (1) by a recognition since 5 Ts is positive or zero (T - T> O) or AT is AT 5 S - tr Apositive T> 0), for a minimum time of about two minutes. 8. Dryer implementing the method of one   any of claims 1 to 7, characterized in that   comprises a temperature sensor (14) disposed in an air outlet duct (6) of a laundry drum (2) and operating a temperature sensing of the air circulating thereon and a control circuit (15) provided with an electronic card (16) using a microprocessor providing temperature measurements, a record of the data entered, determinations of the temperature variations from these data, a storage of the operating program, a preset value of the temperature of the temperature; safety Ts, threshold S of temperature variation per unit of time; selected humidity thresholds at the end of drying of the laundry, control of the tumble dryer components, execution of the selected operating programs, interruption of these programs according to detected faults, and light, sound or light signaling of these failures.   9. Tumble dryer according to claim 8, characterized in that it comprises for a light signaling faults, three aligned diodes (21, 22, 23), the first two (21, 22) are lit for a heating failure. , both ends (21, 23) are lit for a ventilation fault by a fan stop (4), the last two (22, 23) are lit for a failure of either heating or clogging of the duct the three (21, 22, 23) are lit for an obstruction of the air outlet duct (6), and the three (21, 22, 23) are   blinking for non-interruption of heating.