Patent Publication Number: US-7225056-B2

Title: Method for checking valves in a program-controlled water-carrying household appliance

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The invention is based on a method for checking valves in a program-controlled water-carrying household appliance, in particular in a washing machine or a washer dryer. The machine may be equipped with a control valve that controls the supply of water, with a measuring device that detects the water feed, and with a safety inflow system that contains a stop valve for stopping the supply of water in the event of a problem caused by leakage water. 
   A safety device of that type has become known from German patent DE 39 17 013 C2. The safety hose for a hydraulically secured connection of water-carrying household appliances described in that document has a solenoid valve for blocking off the supply of water in the event of leak, which solenoid valve is accommodated in a valve armature which is directly connected to the domestic water mains. The safety hose is the connection between the household appliance and the domestic water mains. Water is fed by means of a delivery hose and is controlled by the control valve, which is disposed in the appliance directly downstream of the hose connection. The delivery hose is surrounded at an axial distance by a flexible outer tube, which collects escaping leakage water and diverts it into the household appliance. The shut-off valve at the domestic water mains is closed by a switching signal, which is triggered in the event of a leak by a monitoring device in the household appliance. 
   Household appliances in which the water flowing in is to be distributed further contain at least one control valve. In the case of household appliances of this type which have a safety hose, the stop valve and the control valve are hydraulically connected in series. This type of system is redundant in terms of safety: Both valves are closed before the program starts and once the program has finished. This type of arrangement and of this connection means that leaks at one of the two valves are very difficult to detect. Problems at the stop valve, for example due to lime deposits during long-term operation of the appliance or due to faults in the control line, have no effect at all if the control valve is operating without problems. The user receives no information as to whether the stop valve is closing, that is to say whether the valve is performing its intended role as an emergency shut-off switch in the rare case that leakage water escapes, thereby being able to prevent greater damage to the appliance and to the area in which it is installed. 
   The stop valve which is part of the safety system is opened at the start of the program and remains in the open position for the entire program run time. A leaking stop valve has no effect on the program sequence of the household appliance and can therefore not be detected in this phase either. The inflow of water as required by the program during the working cycle is controlled exclusively by the control valve in accordance with the parameters predefined for the program section in question. Pressure sensors which record the filling level in the appliance are mostly used for this purpose. The filling level is also used to regulate the inflow of water by a signal for closing the control valve arranged in the inflow line being generated when a predefined upper setpoint level is reached and by the control valve being opened again when the water level falls below a lower setpoint level. 
   The method controlled in this way can be improved upon in accordance with German patent DE 39 00 705 C1 if the inflow of water is observed using an idealized inflow curve which is matched to the type of machine. The filling process is relatively slow in this improved method too, and has the further disadvantage that the amount of water flowing in cannot be limited narrowly enough and as a result more water than is absolutely necessary for the washing process regularly flows in. In order to be able to restrict the amount of water supplied for each program section to the necessary minimum, the amount of water flowing in must be determined independently of the fluctuating pressure conditions in the domestic water mains as accurately as possible and must be able to be limited with as narrow a tolerance as possible. For this purpose, and in order to speed up the filling process, throughflow meters are increasingly being used. 
   SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide a method of checking a valve in a program-controlled, water-carrying household appliance which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which improves the reliability of the inflow system described above. In the process, the expenditure of implementing the method is to be restricted to a minimum, in particular there must be no need to use additional assemblies or individual parts. 
   With the foregoing and other objects in view there is provided, in accordance with the invention, a method for checking the valves of a program-controlled water-carrying household appliance, such as a washing machine or a washer dryer. The method is to be carried out in a household appliance equipped with a control valve controlling a supply of water, with a measuring device detecting a water feed, and with a safety inflow system including a stop valve for stopping the supply of water in an event of a problem caused by leakage water. The method comprises checking the functionality (i.e., serviceability) of the control valve and of the stop valve each time the household appliance is used at least once during a time selected from the group consisting of before, after, and during a course of program processing. 
   In other words, the objects of the invention are achieved by checking the functioning of the control valve and of the stop valve before, after, and/or during the course of a program each time the household appliance is put into use. As indicators of the functional reliability of the valves, measured data which can be obtained by means of the devices available for monitoring the amount of water flowing in are evaluated, for example by means of the pressure sensor used to monitor the filling level or by means of the throughflow meter. This expansion of the functions of the available measured value sensors, the pressure sensor or the throughflow meter means that expenditure on implementing the method is restricted to expanding the control system software. 
   In accordance with an added feature of the invention, the valves are alternately opened and closed for checking the functioning and a certain change in the measured values of a measuring device which detects the water feed serves to identify a problem at a valve. 
   In accordance with an additional feature of the invention, during a predetermined water inflow phase, measured values are continuously picked up by the measuring device which detects the water feed or are picked up at brief, specifically predefined intervals, and in that the control valve and the stop valve are closed one after the other for a brief period of time, and the change in the measured values is compared with a setpoint value stored in memory by an intelligent evaluation system. 
   In accordance with a further feature of the invention, the period of time is extended by one unit of time once or more than once until the measured values relating to the closing time have reached an experimentally determined stipulated value. 
   In accordance with a further feature of the invention, a warning signal and/or an error message are/is output when the intelligent evaluation system detects a significant problem. 
   With the above and other objects in view there is also provided, in accordance with the invention, a device that is configured to carry out the novel method and which has a pressure sensor or a throughflow meter forming the above-noted measuring device that detects the water feed. 
   Other features which are considered as characteristic for the invention are set forth in the appended claims. 
   Although the invention is illustrated and described herein as embodied in a method for checking valves in a program-controlled water-carrying household appliance, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
   As noted above, the invention is particularly suitable for a washing machine (i.e., a washer) and for a washer dryer (i.e., a combined washing and drying machine, or a washer with a drying cycle). Other appliances are within the field of the invention. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a partly transparent side view of a washing machine having a safety hose; 
       FIG. 2  is a volume/time diagram for a first example of a filling process with the valves being checked; and 
       FIG. 3  is a volume/time diagram for a second example of a filling process with the valves being checked. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a schematic view of a washing machine with a safety hose  11 ,  12  for leakage water that is securely connected to the water mains connection  10  by way of the screwed connection  13 . In the event of a problem as a result of leakage water escaping, a corresponding closing signal is supplied to the stop valve  8  arranged directly downstream of the water mains connection  10  in order to allow the stop valve to shut off the inflow of water. This closing signal is triggered by the monitoring device  4  and conducted to the stop valve  8  via the signal line  7  which runs between the delivery hose  11  and the flexible outer tube  12 . The monitoring device  4  is arranged in the trough  3  which is formed in the base plate  2  of the washing machine housing  1  and in which the leakage water is collected. 
   The washing tub  15  and the washing drum  16  rotatably mounted therein are filled with water from the mains connection  10  via the stop valve  8 , the delivery hose  11 , the control valve  9  and the throughflow meter  5 , this filling being controlled by a control device which has not been illustrated. 
   Control valves  9  are needed in washing machines on account of the required distribution to a plurality of chambers of a non-illustrated detergent feed device. These and further components and lines connected downstream and via which the water flows into the washing tub  15  are of no importance to the understanding of the method according to the invention and they are therefore likewise not illustrated. 
   The inflow of water is regulated by means of the control valve  9  as a function of the water level  18  in the washing tub  15  by the pressure sensor  17  and/or as a function of the amount of water flowing in by the throughflow meter  5 . 
   Before the appliance is used, the control valve  9  and the stop valve  8  are closed. The stop valve  8  is opened each time a program starts and remains in the open position until the program has finished. The control valve  9  is only opened during the controlled inlet of water. 
   In a first variant for implementing the method according to the invention, it is provided in order to check the functioning of the valves  8  and  9  hydraulically connected in series that the valves are alternately opened and closed before, after or during the course of the program in a phase in which the drum  16  in the washing tub  15  is not moved and the control valve  9  is shut off in accordance with program requirements, and the change in the level of water in the washing tub is recorded by the pressure sensor  18 . Given switching times selected to be suitably long, the faulty valve  9  or  8  can be identified by comparison with a setpoint value stored in memory and experimentally determined for each type of appliance separately. 
   For example, when valve  9  is initially moved to the closed position, the valve  8  is first moved to the closed position for a short time and even when valve  8  is in the closed position, the valve  9  is moved to the open position for a short time. If, in this case, the level of washing solution in the washing tub  15  changes significantly, then the valve  8  is faulty since it should have been closed in accordance with a corresponding control signal. In a further checking phase, the valve  8  may be moved to the open position for a short time and even when valve  8  is in the open position, the valve  9  may be moved to the closed position for a short time. If, when the valve  8  is in the open position, the level of washing solution likewise changes significantly, the valve  9  is faulty because it should have been closed in accordance with a closing signal which is present. 
   In a preferred second variant of the invention, the measured values are evaluated at the throughflow meter  5  in the above-described method. Recording the measured values using the throughflow meter  5  ensures a significant improvement in accuracy and therefore a greater reliability in using the method according to the invention to ensure the reliable diagnosis of a valve  8  or  9  which is not closing or is not closing completely, even in the case of short closing times. Since the measured values are not corrupted by drum movement, the method can also be carried out during a washing or rinsing phase. 
   A further preferred variant for carrying out the method according to the invention will be described with reference to the diagrams shown in  FIGS. 2 and 3 . The diagrams show the profile of the volume flow over time when filling the washing tub of a washing machine under different pressure conditions at the mains connection. In the diagram, V e  is the total volume of water to be introduced for the program segment and ΔV 1  is the amount of water flowing in over a specific time. The water pressure is assumed to be constant during the inflow phase. 
   In a departure from the above examples, the control valve  9  and the stop valve  8  are closed one after the other for a short period of time Δt 9  and Δt 8  respectively, during a selected water inflow phase and the change in the measured values preferably recorded at the throughflow meter  5  is compared with a setpoint value stored in memory by an intelligent evaluation system. The closing time Δt for the valves  8  and  9  is to be dimensioned such that, with a normal water pressure in the supply mains, the drop in the flow of water can be reliably recorded in the throughflow meter. On the other hand, the filling of the washing tub should only be interrupted for as short a time as possible, that is to say the closing time Δt should be so tightly dimensioned that the overall program run time is not significantly extended. These conditions can be satisfied with closing times in the range of one second and with the use of a throughflow meter forming the measured value sensor. In addition to significantly higher sensitivity, it is advantageous to use the throughflow meter in order to be able to carry out the method in phases with the washing drum moving too, as in the second variant described. 
   In order to preclude erroneous diagnoses, a further refinement of the method according to the invention provides for the system to be self-calibrated. For this purpose, the closing time Δt is adapted by automatic control to the boundary conditions, for example to the water pressure in the domestic water mains, prevailing at the time of the function check. In the case of the expanded method, the volume flow ΔV over the period of time Δt is measured first in the selected water inflow phase. This ΔV must not fall below a minimum value which is experimentally determined for each model of washing machine and is permanently stored in the program memory as a setpoint value. If ΔV/Δt is below the setpoint value, the closing time Δt is extended in steps by one unit of time and the process is repeated. 
   The method sequence is to be explained with the aid of the diagram in  FIG. 3 . In this example, the water flows in considerably more slowly, as can be seen by the flat profile of the inlet curve. The cause of this may be a drop in pressure on account of an increased amount of water being taken from the domestic water mains or on account of a partial interruption in the feed of water from the domestic water mains. 
   The volume of water flowing in per unit time Δt can be read off from the abscissa at ΔV 2 . ΔV 2 /Δt is considerably lower than ΔV 1 /Δt in  FIG. 2  and in the example should be below the predefined setpoint value. It is provided in this case, that the process is once again repeated under the automatic control of the system. The closing time Δt is extended by one unit of time with each repetition. In the example, it is assumed that the setpoint value is reached or exceeded after a time extension and the calibration process is thereby concluded. The Δt′ value determined in this way is then the new closing time for the control valve  9  (Δt′ 9 =t 2 −t 1 ) and for the stop valve  8  (Δt′ 8 =t 4 −t 3 ). 
   This type of calibration virtually precludes the possibility of erroneous diagnoses by the system and thus of the unjustifiable triggering of error messages. The functional reliability of the method is not restricted by temporary problems with the inflow of water or with the supply mains or by insufficient sensitivity of the throughflow meter. The reliability of the method can be further improved by the fact that a problem which has been diagnosed is checked once again at a later point in time under the control of the system. 
   This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 103 39 252.1, filed Aug. 26, 2003; the entire disclosure of the prior application is herewith incorporated by reference.