CROSS-REFERENCES TO RELATED APPLICATIONS

This application is the U.S. National Stage of International Application No. PCT/EP2018/061648, filed May 7, 2018, which designated the United States and has been published as International Publication No. WO 2018/210594 A1 and which claims the priority of German Patent Application, Serial No. 10 2017 208 527.4, filed May 19, 2017, pursuant to 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The present invention relates to a water-conducting household appliance and a method for operating a water-conducting household appliance.

Water-conducting household appliances frequently have moving components, for example a water diverter, which moves and/or is moved to predetermined positions during operation of a respective appliance. In order to be able to move to a predetermined position specifically, it is necessary to know the current position of the component. A switching cam is conventionally used for example, sending a signal to a control apparatus when the moving component is moved over a specific position so the position is determined. However the switching cam has to be coupled to the control apparatus for this purpose. This is done using a signal cable for example, which increases the complexity of the appliance due to the additional wiring outlay. Corresponding inputs also have to be provided on the control apparatus. Such a solution is known for example from WO 2016/096019 A1.

BRIEF SUMMARY OF THE INVENTION

Against this background one object of the present invention is to provide an improved water-conducting household appliance.

According to a first aspect a water-conducting household appliance, in particular a dishwasher, is proposed, with a moving component, an electric motor for moving the component, a control apparatus for actuating the electric motor and a load apparatus for providing a resistance, which is a function of a position of the moving component and counter to the movement. The control apparatus is designed to detect the drive current, which is drawn by the electric motor and is a function of the resistance provided, and to ascertain the position of the moving component as a function of the detected drive current.

Such a water-conducting household appliance has the advantage that the position of the moving component can be ascertained, while being able to dispense with additional cabling to a position sensor and the position sensor itself. This in particular reduces the complexity of the water-conducting household appliance and lowers costs. The position of the moving component of the water-conducting household appliance is therefore advantageously identified without additional cabling outlay.

The electric motor is in particular configured as a brushless DC motor (BLDC motor). Such a BLDC motor is actuated for example with a predefined DC voltage. A direction of rotation and a rotation speed of the BLDC motor can for example be controlled here by way of a drive voltage. The direction of rotation here is a function in particular of a polarity of the drive voltage and the speed is a function of an amplitude or size of the drive voltage. Such a BLDC motor draws a drive current that is a function of a load. The greater the load, the greater the power of the BLDC motor. Therefore the BLDC motor draws a higher drive current with a large load than with a small load.

The control apparatus is designed to actuate the electric motor. To this end the control apparatus has a cable connection to the electric motor for example and can supply it with a predefined drive voltage. For example the control apparatus has a voltage source for this, in particular a voltage source with a controllable output voltage, for example a power supply unit or transformer. The voltage source is designed in particular to provide the predefined drive voltage. The electric motor draws a drive current, which is a function of the load and is provided by the voltage source.

The control apparatus can be implemented by means of hardware and/or software. In a hardware implementation the control apparatus can be configured as a computer or microprocessor. In a software implementation the control apparatus can be configured as a computer program product, function, routine, part of a program code or as an executable object. The control apparatus can in particular be a central control apparatus for operating the water-conducting household appliance.

The load apparatus in particular comprises a mechanical unit coupled to the moving component. The load apparatus provides a resistance counter to the movement of the moving component as a function of the position of the moving component. This resistance can be generated for example by friction.

For example the movement of the moving component has a natural resistance, which is a function in particular of the support of the moving component. This resistance is referred to in the following as the basic resistance. The basic resistance per se can already have a position-dependent size for example.

The load apparatus is designed to change this basic resistance specifically as a function of position. This can include both reducing the resistance locally and also increasing the resistance locally.

For example the moving component is a spray arm of a dishwasher. The spray arm is supported in a rotatable manner, rotation of the spray arm for example consuming a power loss of 1.2 W without a load apparatus. The electric motor provides this power during operation with a drive voltage of 12 V by drawing a drive current of 0.1 A. If the load apparatus is designed to provide an increased resistance in a rotational movement range, for example 0°-10°, so the power loss is doubled to 2.4 W in this range, the electric motor draws a drive current of 0.2 A to provide this power, in order to maintain the rotational movement of the spray arm in a regular manner over this range.

The control apparatus is designed to detect the drive current drawn by the electric motor and to ascertain the position of the moving component from this. To this end the control apparatus has an ammeter for example. Detection can also include storing a detected value. To ascertain the position of the moving component, the control apparatus is designed in particular to compare a detected value with a reference value, to make assignments and/or to perform different calculations. Such calculations include for example ascertaining functional values and/or performing pattern recognition, in particular a spectral frequency analysis. In the example set out above it can be concluded from the doubling of the drive current that the position of the spray arm is in the range between 0° and 10°.

According to one embodiment of the water-conducting household appliance the moving component is configured as a water-conducting component, in particular as a spray arm of a dishwasher or as a water diverter.

Such components are designed for example to execute a rotational movement. To this end they are mounted for example on a rotation axis, such as a shaft or drive axle, which is supported in a rotatable manner.

According to a further embodiment of the water-conducting household appliance the moving component is designed to perform a rotating movement about an axis.

Such a rotational movement is in particular periodic; in other words the movement is repeated after a complete rotation of the moving component. For example the load apparatus is designed to provide an increased resistance at 90° intervals for 5° respectively. During the course of a complete rotation of the moving component the drive current drawn by the electric motor is therefore increased four times. Increased here is in relation in particular to the drawn drive current at positions in which the resistance is not provided or not increased by the load apparatus but where only the basic resistance is active.

According to a further embodiment of the water-conducting household appliance the load apparatus is designed to provide a resistance that is a function of a degree of rotation of the moving component.

The degree of rotation can be given for example as an angle relative to an initial angle. As such a rotational movement is periodic, the initial angle can be freely selected.

According to a further embodiment of the water-conducting household appliance the load apparatus comprises a transmission unit for coupling the electric motor to the moving component.

In this embodiment the load apparatus therefore has a double function: on the one hand it provides the position-dependent resistance, on the other hand it couples the electric motor to the moving component.

According to a further embodiment of the water-conducting household appliance the transmission unit is designed to reduce a rotation speed of the electric motor by a predefined factor when coupling the electric motor to the moving component.

The predefined factor is also referred to as a gear reduction. Such a gear reduction can in particular change a drive torque for the moving component. A gear reduction is also advantageous for example in order to reduce a high rotation speed of the electric motor and to increase uniformity of movement.

According to a further embodiment the transmission unit is designed to convert a rotational movement provided by the electric motor to a linear movement.

According to a further embodiment of the water-conducting household appliance the load apparatus is designed to provide the resistance according to a predetermined load function as a function of the degree of rotation of the moving component.

The resistance therefore has a resistance value as a function of the degree of rotation. For example the resistance value can increase linearly in proportion to the degree of rotation and drop back to the initial value after a complete rotation. In this embodiment it is possible to map the position of the moving component, which is shown here by the degree of rotation, clearly onto the resistance value and therefore also onto the drive current drawn by the electric motor.

According to a further embodiment of the water-conducting household appliance the load apparatus is designed to provide the resistance as an increased resistance and/or reduced resistance relative to a basic resistance, which corresponds to the resistance when the moving component moves without the load apparatus.

In this embodiment the position can be identified robustly in particular in respect of interference, for example chaotically occurring hydrodynamic disturbance variables or even mechanical disturbance variables, for example due to dirt particles that counteract movement. Such interference or disturbance variables result in particular in locally increased resistance, for example because a dirt particle inhibits the course of movement. If such a dirt particle adheres in a certain position, the electric motor draws an increased drive current every time the moving components passes over this position. This could result in incorrect position identification. Such incorrect position identification is excluded in particular by providing a local resistance reduction, which cannot originate from one of the cited disturbance variables.

Such a resistance reduction relative to the basic resistance can be achieved for example by a load apparatus, which at the same time acts as a transmission unit to couple the electric motor to the moving component. To this end provision is made for example for suspending a transfer of force from the electric motor to the moving component at certain points. The moving component is therefore not driven at such points so the basic resistance due to the moving component drops in particular to zero. The drive current drawn by the electric motor is therefore also zero or at least almost zero. A deviation from zero can result here in particular due to losses ascribable to the electric motor itself.

According to a further embodiment of the water-conducting household appliance the control apparatus is designed to actuate the electric motor as a function of the ascertained position of the moving component in such a manner that the moving component is moved into a predetermined position.

A predetermined position can be determined for example by a specific degree of rotation. For example specific cleaning of predefined or even dynamically determined regions in the dishwasher can be achieved by moving a spray arm of a dishwasher into a predetermined position. This allows a flatware basket for example to be targeted specifically and selectively.

According to a further embodiment of the water-conducting household appliance the control apparatus is designed to actuate the electric motor to perform a complete movement amplitude to ascertain a current load function of the moving component and to detect the drive current drawn by the electric motor in the process.

Such an operation can also be referred to as standardization or calibration. The moving component is arranged for example in an environment exposed to widely varying conditions, for example a washing chamber of a dishwasher. It can be the case here that the mechanical properties of the movement of the moving component change, for example due to soiling, over the working life of the water-conducting household appliance. If such a calibration is performed for example before each use of the water-conducting household appliance, it is possible to detect the drive current drawn by the electric motor during regular performance of the movement and to store it as a reference. The control apparatus is then in particular designed to ascertain the position of the moving component as a function of said reference.

A complete movement amplitude here means that the moving component reaches every position the moving component can reach just once. It is also possible to distinguish a respective position based on different movement directions. In the case of a linear oscillation movement from a left stop to a right stop the complete movement amplitude for example comprises the movement from the left stop to the right stop and back again.

Because the moving component is actuated to perform a complete movement amplitude, it can also be ascertained whether for example an object, such as an item to be washed in a dishwasher, is blocking the course of movement. If so, provision can also be made for outputting a corresponding error message or warning to a user of the dishwasher.

According to a further embodiment of the water-conducting household appliance the control apparatus is designed to identify blocking of the moving component as a function of the drive current drawn by the electric motor.

According to a further embodiment of the water-conducting household appliance the water-conducting household appliance is configured as a dishwasher, a washing machine or a tumble dryer.

According to a further aspect a method is proposed for operating a water-conducting household appliance, in particular a dishwasher, with a moving component, an electric motor for moving the component and a control apparatus for actuating the electric motor. In a first method step the electric motor is actuated. For example the control apparatus supplies a constant DC voltage to the electric motor. In a second method step a load apparatus provides a resistance, which is a function of a position of the moving component and counter to the movement. In a third method step a drive current is detected, which is drawn by the electric motor and a function of the resistance provided. Detected means for example recorded, read or measured. In a fourth method step the position of the moving component is ascertained as a function of the detected drive current. For example the detected drive current is an unambiguous function of the position. It is then possible to derive or calculate the position directly from the detected drive current by inversion. A table can also be provided, in which values for the detected drive current are assigned to a position. This can also be referred to as a look-up table.

The embodiments and features of the proposed water-conducting household appliance apply correspondingly to the proposed method.

A computer program product is also proposed, which prompts the performance of the method as described above on a program-controlled facility.

A computer program product, for example a computer program means, can be provided or supplied for example as a storage medium, for example a memory card, USB stick, CD-ROM, DVD or even in the form of a downloadable file from a server in a network. This can take place for example in a wireless communication network by transferring a corresponding file containing the computer program product or the computer program means.

Further possible implementations of the invention comprise combinations of features or embodiments described above or in the following with regard to the exemplary embodiments even if these are not cited specifically. The person skilled in the art will also add individual aspects to improve or complete the respective basic form of the invention.

