DE3146527C2 - Method for detecting a lack of water in the water supply in a program-controlled washing machine - Google Patents

Abstract

In a program-controlled washing machine, which is provided with separate feed paths for cold and warm fresh water, a water shortage when cold and hot water is supplied is to be recognized, the controller is to be given a signal and the operator is to be given an indication of the cause. The solution for recognizing a lack of water is that the water level in the tub is measured before the inflow of cold and warm water and a specified period of time afterwards, the two measurement results are compared with each other and if the difference falls below a specified minimum value, the program run is aborted and an optical and / or acoustic fault message is triggered. The method according to the invention is carried out by an automatically operating drum washing machine which contains a master control part (e.g. microcomputer), solenoid valves for cold and hot water supply and a slave control part assigned to the method according to the invention. This essentially consists of three timing elements (3, 7, 15) for cold water supply, level calming and hot water supply as well as an electronic level sensor (17), a sample-and-hold amplifier (6), an analog switch (10), a comparator ( 11), an error flip-flop (12), a short time element (5) for the acquisition time of the sample and hold amplifier (12) and a short time element (9) for the comparison time of the comparator (11).

Description

The invention relates to a method for detecting a lack of water when cold and cold water is flowing in Hot water via separate paths in a program-controlled washing machine, with the The water level in the suds container is measured.

There are facilities in washing machines known (z. B. DE-GM 1891428, DE-OS 1435023) that it allow, in the case of insufficient flooding of the sump in the tub, d. H. at water levels below the 5 uppermost radiator to cancel the program run (heating up the liquor) in order to damage the laundry and avoid radiators. Monitoring the correct flooding of the entire radiator is done by a so-called dry boil protection.

The means used for this are pressure switches (DE-OS 1435023), float switches or electronic switching means with sensing electrodes (DE-GM 1891428).

In a washing machine known from US Pat. No. 4,195,500, a predetermined period of time To, which is normally required to completely grooves the tub, z. B. 5 minutes, compared with the actually elapsed time T since switching on the water supply until a predetermined filling level was reached. As soon as the elapsed time 7 * is equal to or greater than the predetermined time period To which is constantly compared with it, the error message and the termination of the program run are triggered. If, on the other hand, the elapsed time T is below the predetermined time period To, d-yin, this means that the final water level has been reached within the predetermined time period - that is, properly. The program then immediately continues with the next step.

Such a lack of water detection cannot be satisfactory because it is necessary to establish the correct one Wait a long time for the water supply (5 min.). There is a desire for a lot previous statement. All the more so because there is a lack of water when connecting cold and hot water must be established long before the time to reach the final water level has elapsed, so that still enough opportunity to mix the cold water with the hot water to a predetermined temperature consists.

A method for providing an amount of liquid with a selectable temperature from a cold water and a hot water inflow is known from DE-OS 2658435. Before reaching a With a predetermined amount of water in the tub of a washing machine, the heater cannot operate there so that the heat content of the hot water flow is first used. If this is not enough, to set the selected temperature of the amount of water, then by means of a radiator in the Reheated vat.

The invention is based on the problem of water shortage in a washing machine with an inlet of cold and hot water to be recognized early enough that the program run is aborted in the event of a lack of water and the user can be notified of the lack of water before the Cold water inlet so much hot water has flowed in that the hot water which cannot be influenced in terms of temperature the laundry has reached.

If the temperature of the hot water is too high, the laundry could be damaged. "Lack of water" is intended here and in the following to mean that at one outlet of the two water supply valves (Cold and hot water) or at both outlets (cold and hot water) the pressure is so low that within a specified period of time for the

The water level in the suds container has not reached a lower, specified limit. The pressure is on too low if the water tap in question is not open or not open wide enough or if the The water pressure in the relevant pipe is not high enough.

According to the invention this task is; solved by that the water level before the inflow of cold and hot water and a predetermined period of time is then measured, the two measurement results together are compared and if the difference falls below a predetermined minimum value the program sequence is canceled and an optical and / or acoustic fault message is triggered will. If the level falls below a certain, specified level, the program run stopped and the user informed of the status. This can be done, for example, by an illuminated one Note "water tap" done on the control panel. The user must then use the cold or Open the hot water tap (or both) or continue to open it and restart the program.

This type of differential measurement is made possible by a level sensor, which measures the input variable "Water level in the suds container" into a level-proportional, electrically equivalent output signal transformed and has a steady, linear transmission behavior and to a measured value processing Logic is connected. For the measurement of the minimum permissible measurement difference of the water level, i. H. the smallest possible amount of inlet water, ε-ind Parameters such as load and type of laundry (wool, synthetic) due to the different absorbency to be taken into account if the inflow is already sufficient to wet the laundry. The measurement difference are therefore, in this respect, the most unfavorable conditions must be used. By the invention The procedure is a pressure switch on the respective inlet solenoid valve for cold or hot water inlet, such as B. in condensation dryers or dishwashers, not required. The method according to the invention can be used anywhere in cold and hot water domestic appliances where a check is required is necessary for a lack of cold and hot water.

Further advantageous refinements of the invention result from application of the method according to FIG Claim 1 in a program-controlled washing machine from claims 2 to 6, whose Features can be used individually or in combination with one another.

The method according to the invention is based on an exemplary embodiment shown in the drawing explained below. It shows

1 shows a block diagram for carrying out the method according to the invention. The lines between the individual circuit blocks represent active connections,

2 shows a circuit example for a sample and hold amplifier,

3 shows a circuit example for an analog switch using an FET and

FIG. 4 shows a flow diagram of the functions in the block diagram of FIG. 1.

The first phase of the method according to the invention begins with actuation of the start button 1 of a washing machine control. The timer 3, which can be a monoflop, is started by the rising switch-on edge. The timer 3 in turn opens the solenoid valve 2 for cold water supply and starts the timer S with the rising edge via a logic OR link 4, which can also be a monoflop. The timer 5 activates the sample-and-hold amplifier 6, which queries the level sensor 17 at the same time as the cold water inflow begins. After the relatively very short period of time At ^ , the timing element 5 has expired and switches the amplifier 6 to the "Hold" state, ie the measured value obtained by the level sensor is stored. The amplifier 6 (see FIG. 2) consists of a first operational amplifier which is connected as an input follower, an FET as a digitally controlled switch, a capacitor for storing the measured value and a second operational amplifier which is connected as an output follower. After the relatively long period of time At] , the timer 3 has expired. With the falling edge of the timer 3, the timer 7, which can be a monoflop, and the timer 9, which can be a monoflop, via a logical OR link 8. When the timer 9 is started, an analog switch 10, which can be an FET (Fig. 3), at this point in time (end of the cold water supply), the current level value is queried and the level value stored in the amplifier 6 from the beginning of the? Compare cold water supply. If the current level value is not greater or not by a certain amount ANK _ml " greater than the older stored level value, the output signal of the comparator II jumps from" low "to" high "and sets the flip-flop 12, which over the line 13 sends a signal to the control unit, not shown, which interrupts the program sequence. In addition, the LED 14, which is also connected to the line 13, gives an optical signal to the operator.

If, on the other hand, no inadmissible conditions have been found in the cold water supply, the timer 9 expires after the relatively very short period At $ and interrupts the comparison so that the flip-flop 12 cannot be set. There is then no water shortage message.

When the timer 7 started, the second phase began, which is used to calm the water level in the tub. After the relatively long period of time Ati , the timer 7 has expired. With the falling edge of the timing element 7, the timing element 15, which can be a monoflop, and via the rising edge of the timing element 15 and a logic OR link 4, the target element 5 is started.

When the timer 15 starts, the third phase begins. The timer 15 opens the solenoid valve 16 for hot water supply, releases the amplifier 6 and thus enables the water level to be detected at the beginning of the hot water supply. After the relatively very short period Ati, the timer 5 has expired and switches the amplifier 6 to "store the measured value". After the relatively long time Ali , the timer 15 has expired. With the falling edge of the timer 15, the timer 9 is started via a logic OR link 8, the current level value at the end of the hot water supply being compared with the level value stored in the amplifier 6 (start of the hot water supply) via an analog switch 10 will.

Is not greater in this comparison, the current level value or not, jumps by a predetermined amount greater than in the older level value as the

Output signal of the comparator 11 goes from "low" to "high" and sets the flip-flop 12, which via the Line 13 sends a signal to the controller and the user via an LED 14 about the faulty Operating conditions informed. The flip-flop 12 is an RS flip-flop, which is set when the set input Is "high" and is reset when line 28 of the controller is "high".

However, if no inadmissible conditions for the hot water supply could be determined, it will run the timing element 9 after the relatively very short period of time 4/5 and prevents the comparison and thus the Set the flip-flop 12. There is then no water shortage message.

The electronic level sensor 17 is powered by a Constant voltage source supplied with a reference voltage (not shown in detail). It can The output signal of the electronic level sensor 17 is transmitted directly to the control system via the line 19 so that the current level value is always available for control purposes.

An advantageous embodiment of the block diagram of FIG. 1 is shown in dashed lines Elements shown. The logical AND link 26 links the output of the timer 9 with the Output of the comparator 11 conjunctive. As a result, the flip-flop 12 is only set when the timer 9 the Has given the signal »comparison valid«.

In Fig. 4 the processes in the method according to the invention, as described above with reference to FIG. 1, are shown graphically. The time / output signals under a) of the timer 3, under b) of the timer 7, under c) of the timer 15, under d) of the timer 5, under e) of the timer 9, under h) of the comparator 11, shown under i) the logical AND operation 26 and under k) the error flip-flop 12. The positive input signal is shown under 0 and the negative input signal of the comparator is shown under g). Here, Au is the acquisition time ("Sampling"), At] -Ai ₁ and At} -Ata, the opening times ("Hold") for the sample-and-hold amplifier and the drop in the shown in 0 (comparator plus input) stored measured value the skew rate in the case of non-ideal analog memories. A temporal uncertainty when recording the measured value can be neglected, since Au <At], Aty. Incidents are shown hatched. After a malfunction occurs, the program run is aborted and an error message is given to the user. After eliminating the problem, the user can restart the program. The above relation < should mean the factor 10 ... 100. At is around 15 see in absolute terms.

For this purpose 3 sheets of drawings

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Claims (6)

Patent claims: 1. Procedure for detecting water shortages when cold and hot water are supplied separately Paths in a program-controlled washing machine, with the water level in the tub is measured, characterized in that the water level in each case before Inflow of cold and hot water and a predetermined period of time is measured thereafter, the two measurement results are compared with each other and if the difference is not reached, below a predetermined minimum value, the program run is aborted and an optical and / or acoustic fault messages are triggered. 2. Program-controlled washing machine using the method according to claim 1, characterized in that the electrical! equivalent of the level in the tub er-.vzeugender electrical level sensor (17), one that records the equivalent when the ■ water supply begins and sample-and-hold amplifier (6) storing until the end of the water supply. a the switching equivalent to be compared formed after the specified period of time Analog switch (10) and a comparator (11) comparing the equivalents are provided. 3. Program-controlled washing machine according to claim 2, characterized in that the set input (S) of an error flip-flop (12) is connected to the comparator (11), the activation output (line 13) of which carries an error signal. 4. Program-controlled washing machine according to claim 2 or 3, characterized in that that three timers (3, 7,15) for a timed Sequence with the three phases »cold water supply«, »level stabilization«, »hot water supply« provided are, the first timer (3) with the cold water valve (2), the third timer (15) with the Hot water valve (16), and the first (3) and the third timing element (15) with each other via the second Timing element (7) are operatively connected. 5. Program-controlled washing machine according to claim 4, characterized in that the Outputs of the first and third timing element (3, 15) with a setting that can be set on a rising edge first short-term element (5) and with a second short-term element (9) that can be set on a falling edge connected, the output of the first short-term element (5) to the sample-and-hold amplifier (6) and the Output of the second short-term element (9) are connected to the analog switch (10). 6. Program-controlled washing machine according to claim 5, characterized in that the acquisition time (At ^) of the sample-and-hold amplifier (6) by the first short-term element (5) and the comparison time (Ats) of the comparator (11) by the second short-term element (9) are specified.