EP1593335B1 - Method for detecting a default of a device for measuring the water quantity of a dishwasher - Google Patents

Abstract

A sensor detects the lowest level required for the stable operation of a circulating pump. An evaluating circuit processes signals received from a measuring device (MD) and a level sensor. A device limits a volume flowing into a rinsing container, partly filled in a first stage (FS) and identified by the MD as a preset amount. FS filling time required is compared with a preset minimum time.

Description

The invention relates to a method for detecting a fault of a measuring device for detecting the accumulated amount of water in the washing container of a program-controlled dishwasher with a circulation pump, with a sensor for detecting a necessary for the stable operation of the circulating pump minimum level N _min , and with an evaluation circuit for processing the signals received by the measuring device and the level sensor, and with a device for limiting the volume flow flowing into the washing container.

It is known in water-conducting household appliances to determine the amount of water required by the implementation of the program by measuring devices and thereby determine. As an example, here an impeller counter can be mentioned, which is arranged in the water supply of a manufactured and sold by the Applicant dishwasher G 892-4 SCi PLUS and from there emits electrical pulses to the program control, which are dependent on the volume flow of the inflowing water. Due to a jamming or grinding of the impeller counter in its storage can lead to malfunction in the quantity measurement. In the above-mentioned dishwashers, therefore, it is checked at the beginning of the water inlet, whether the impeller emits pulses. As a result, only a complete failure can be detected. An error that makes itself felt by the delivery of too few meter pulses in relation to the amount of water introduced, can not be detected. In order to reduce the effects of such an error, the water inlet quantity is regulated by a so-called baffle plate in the solenoid valve. From a water pressure of 1 bar, this limits the flow rate to approx. 5 liters per minute (depending on the opening cross-section). Thus, the quantity-controlled water supply can be superimposed for safety by a time control. Additional safety can be achieved by a second level sensor, which detects the reaching of an overflow level and then closes the solenoid valve via an integrated in the control evaluation circuit. A disadvantage of the baffle plate is that it only works at a water pressure of 1 bar. At lower pressure conditions in the water supply and the same defect of the impeller counter, the latter can not be detected and it flows a quantity of water in the washing container, which is too high and thus has an increased water consumption and at worst the overrun of the machine result.

The DE 101 15 101 C1 shows a method for detecting / correcting the filling water amount of a washing machine, wherein both filling time, and filling level and filling water quantity are detected. It is not specified how the filling water quantity is detected.

From the DE 40 38 802 A1 It is known to detect the inflowing amount of water via a flow meter.

The DE 33 29 345 A1 also describes a method of measuring amounts of water, wherein the flow rate of the water inlet is determined by determining the time to inflow a reference amount of water (which is detected by a level sensor).

The invention thus presents the problem to disclose a method of the type mentioned, in which an error in the measuring device for detecting the accumulated amount of water is detected, which does not result in their complete failure.

According to the invention, this problem is solved by a method having the features of patent claim 1. An advantageous development of the invention results from the following subclaim.

The advantages achievable with the invention are, in addition to the exact recognition of the above-described error, that it is possible to dispense with a second level sensor for detecting an overflow level.

It has proven to be advantageous to carry out an intermediate section before the second filling step, in which a partial amount is supplied to the washing container, which is identified by the measuring device as a predetermined amount V ₃ , wherein the amount V ₃ corresponds to a level above the minimum level N _min is; and in which then the circulation pump for a predetermined time t _{U is} turned on and then the washing container is emptied. As a result, in the level measurement in the second filling step, the influence of the amount of water that is dependent on the wetting of the ware is eliminated, which, as is known, depends on the type and quantity of ware.

An embodiment of the invention will be described in more detail below. The dishwashing machine suitable for carrying out the method has, in a known manner, a housing in which a washing container, which can be closed at the front by a door, is arranged with a drain pan. The door is pivotally mounted on its bottom-side portion about a horizontally extending axis on the device body. In the dishwasher crockery baskets are available, which are associated with spray arms for cleaning the parked dishes. The supply of the spray arm with rinsing liquid via a circulation pump. For this purpose, water is supplied to the washing at the beginning of various program sections via a supply line, at the end of this program sections, the emptying of the drain pan via a drain pump. The adjustment of the individual wash programs is made possible for the user by various operating and display elements, the execution of these programs is controlled by a program control device, whereby preferably a microprocessor control is used.

The supply line can be opened by means of a solenoid valve by supplying power from the microprocessor control, in the de-energized state, the solenoid valve and thus the supply line is closed. During opening of the valve, a timer runs in the microprocessor control and measures the time during which power is supplied. This time is referred to below as filling time t. In the supply line is also arranged as a measuring device for detecting the accumulated amount of water an impeller. This gives pulses to the microprocessor control, the number of which are proportional to the volume flow passing through the line, so that the control of the number of pulses with a known cross-section can determine the amount of water introduced, hereinafter referred to as V _i .

The drain pan is associated with a level sensor, with which a so-called minimum level N _min can be detected, which is required for a stable running of the circulating pump. The level sensor may be designed as a pressure switch, which is arranged in the line behind the circulation pump and is actuated when pumping water. Alternatively, the speed or other control parameters of the circulation pump can be evaluated, since these change depending on the level.

The measured variables of the timer, the vane counter and the output of the level sensor are processed in the microprocessor control by an integrated evaluation circuit in order to detect an error in the detection of the amount of accumulated water in the washing. This procedure works as follows:

First, in a first filling step, the solenoid valve is opened until the impeller counter has sensed a predetermined amount of water V ₁ , for example 1 liter. As described above, the filling time t required for this water inlet is measured. If the filling time is below a predetermined minimum time t _N , the evaluation circuit detects that there is neither a defect in the impeller counter nor too low a line pressure below 1 bar. There then takes place a quantity-controlled filling of the washing container, whereby a time control is superimposed for the purpose of securing.

If the minimum time t _N exceeded so either a defect of the impeller or a low pressure in the domestic water supply, ie a line pressure below 1 bar are present. To distinguish this, an intermediate section is first performed before the further control. The solenoid valve is opened until the rinsing tank a total of a further subset is supplied, which from the impeller counter as a set V ₃ , for example. 3 liters, is identified, wherein the sum of the quantities V ₁ and V ₃ preferably corresponds to a level which is above the minimum level N _min and thus enables stable operation of the unrolling pump. Subsequently, the circulation pump is turned on for one minute and water is pumped through the spray arms; Finally, the washing container is emptied by switching on the drain pump. This ensures that the items that are present in the dish racks are wetted, so that the amount of water necessary for wetting does not enter into the subsequent measurements.

After pumping, a second filling step is performed. The solenoid valve is opened until a subset has run into the washing, which is identified by the impeller or the microprocessor control as a predetermined amount V ₂ . This quantity V ₂ of about one liter corresponds to a level which is below the minimum level N _min . Thereafter, the circulation pump is switched on for level detection. If the pressure switch switches stable, ie over a longer period of time, then the evaluation circuit recognizes that the amount of water actually in the rinsing tank is greater than that sensed by the vane wheel meter and thus the measurement result is definitely wrong. The running program is aborted and an error message is generated. If the pressure switch only switches shortly after switching on the circulation pump, the evaluation circuit detects that the impeller counter is intact and only the line pressure is below 1 bar. Then the program is continued and volume controlled filled the necessary to carry out the set program amount of water in the washing.

In order to avoid the repeated execution of the intermediate section and the second filling step with intact impeller counter and simultaneous low pressure, a memory may be provided in the microprocessor control, in which the time required in the first filling step for filling the amount V _{1 is} stored. A renewed check only takes place if the respectively measured time t for the current filling step exceeds the stored value by a predetermined percentage of, for example, 15%.

Claims (2)

1. Method of detecting a fault in a measuring device for determining the quantity of water supplied to the washing chamber of a program-controlled dishwasher with a circulating pump, including a sensor for determining a minimum level N_min necessary for the steady operation of the circulating pump and with an evaluating circuit for processing the signals received from the measuring device and from the level sensor, and including a device for limiting the volume flow entering the washing chamber, the said method having the following method steps:

   • execute a first fill step in which a part quantity is supplied to the washing chamber, the said part quantity being identified by the measuring device as preset quantity V₁;

   • compare the fill time t necessary for the first fill step with a preset minimum time t_N by means of the evaluation circuit;
   if the fill time t exceeds the preset minimum time t_N, the following method steps are carried out:

   • empty the washing chamber;

   • execute a second fill step in which a part quantity is supplied to the washing chamber, the said part quantity being identified by the measuring device as preset quantity V₂, wherein the preset quantity V₂ corresponds to a level, which is below the minimum level N_min;

   • output a fault signal by means of the evaluation circuit if a fill level of the washing chamber above the minimum level N_min is detected by the level sensor.
2. Method according to claim 1, characterised in that before the emptying of the washing chamber there is an intermediate section in which the following method steps are carried out:

   • a part quantity is supplied to the washing chamber, the said part quantity being identified by the measuring device as preset quantity V₃, wherein the sum of the quantities V₁ and V₃ preferably correspond to a level which is above the minimum level N_min;

   • switch on the circulating pump for a preset time t_U.