Dishwasher, method and computer program product

Abstract

The invention relates to a dishwasher (1), more particularly a domestic dishwasher, comprising: - at least one spraying device (20) which is actively driven by means of a drive apparatus (15) and intended for applying a washing liquor to items to be washed that can be placed in a washing container (2) of the dishwasher (1), the drive apparatus (15) comprising an electric motor (16) for actively driving the at least one spraying device (20) and a sensing unit (16A) for sensing a motor rotational speed (SIG) of the electric motor (16); and - a control device (25) which is designed to detect a blockage of the at least one spraying device (20) on the basis of the sensed motor rotational speed (SIG).

Description

[0001] The present invention relates to a dishwasher, a method for operating a dishwasher and a computer program product.

[0002] Common dishwashers often feature a rotating spray arm, driven, for example, by a hydraulic recoil mechanism or an electric motor. During operation, items such as knives or plates may protrude from the dish rack and obstruct the spray arm's path. This can cause the spray arm to become blocked. If the spray arm stops rotating, it can negatively impact cleaning results. Therefore, it is advisable to detect a blockage in the spray arm in order to take corrective action.

[0003] Preferably, the dishwasher's spray mechanism is actively driven by an electric motor. This has the advantage that the spray mechanism can rotate at different speeds and / or be stopped at specific points, for example to create an intensive rinsing zone.

[0004] US patent 8,357,246 B2 discloses a dishwasher with a motor-driven spray arm. Monitoring and analyzing the motor current makes it possible to detect a blockage of the spray arm. US patents 8,734,594 B2 and 9,681,790 B2 disclose other conventional dishwashers.

[0005] German patent DE 10 2010 000 351 A1 discloses a dishwasher comprising a wash chamber, a spray arm, and a sensor. The sensor provides data concerning the rotation of the spray arm. The direction of rotation of the spray arm is reversed based on a control signal generated when the load on the spray arm exceeds a predetermined limit.

[0006] DE 10 2010 038 184 A1 discloses a dishwasher comprising a spray arm assembly positioned in the wash chamber of the dishwasher tub and containing a corner arm rotated via an intermediate gear. The intermediate gear arrangement of the intermediate gear allows the assembly to be decoupled from the gear input when the rotation of the corner arm is inhibited.

[0007] EP 3 488 756 A1 discloses a dishwasher comprising a control unit and a pump for pumping water to a spray arm assembly. The spray arm assembly includes a spray arm with one or more spray holes for spraying a wash load with water. The spray arm assembly includes an opening designed and positioned to be in an open or closed state depending on the rotational position of the spray arm. The power consumption of the pump depends at least partially on whether the opening is in the open or closed state. The control unit is configured to monitor the energy consumption of the pump in order to determine rotational information of the spray arm.

[0008] WO 2019 / 120560 A1 discloses a dishwasher with at least one rotating spray arm arranged to spray process water onto items to be cleaned in a chamber. The dishwasher further comprises at least one sensor arranged in a tub of the chamber and configured to detect a property of the process water indicating a periodic rotation of the spray arm as it is sprayed into the tub, and to transmit a signal indicating the detected property. The dishwasher further comprises a control unit configured to receive the signal and determine that the detected property changes periodically.

[0009] DE 10 2017 208 527 A1 discloses a water-bearing household appliance, in particular a dishwasher, comprising a movable component, an electric motor for moving the component, a control device for controlling the electric motor and a load device for providing a resistance that depends on a position of the movable component and opposes the movement, wherein the control device is configured to detect the drive current absorbed by the electric motor and dependent on the provided resistance and to determine the position of the movable component as a function of the detected drive current.

[0010] DE 10 2007 041 313 A1 discloses a method for operating a dishwasher, comprising at least one wash tank, at least two spray devices arranged within the wash tank, a circulation pump for conveying liquid to the spray devices, a first drive for driving the circulation pump, a reversing device by means of which the circulation pump conveys liquid to one of the two and / or to both spray devices, comprising the following method steps: adjusting the position of the reversing device and detecting the current position of the reversing device based on at least one operating parameter assigned to the first drive.

[0011] Further state of the art is formed by the documents WO 2016 / 096020 A1, WO 2017 / 012629 A1, US 2011 / 146733 A1, DE 29708598 U1, DE 4020898 A1, EP 2 048 274 A1 and DE 10 2015 102694 A1.

[0012] Against this background, one object of the present invention is to improve the operation of a dishwasher.

[0013] According to a first aspect, a dishwasher, in particular a household dishwasher, is proposed with at least one spray device driven by a drive unit for spraying dishes arranged in a wash tub of the dishwasher with a wash solution. The drive unit comprises an electric motor for actively driving the at least one spray device and a sensor unit for detecting the motor speed of the electric motor. A control device is provided for detecting a blockage of the at least one spray device depending on the detected motor speed.

[0014] This dishwasher has the advantage of detecting a blockage in the spray mechanism based on the motor speed. This allows for appropriate countermeasures to be taken if a blockage occurs, minimizing its impact on the washing result. As a result, the dishwasher is able to achieve optimal cleaning results despite a blockage. This protects the dishes, as it prevents the spray mechanism from remaining stuck in the blocked position, thus ensuring that only the items located at that point are sprayed with the wash solution. Furthermore, it conserves resources, as it avoids having to run a second wash cycle with the same items because they were not cleaned satisfactorily. A blockage in the spray mechanism can be caused, for example, by the dishes themselves or by dirt that has entered the spray mechanism's drive train.

[0015] The drive unit comprises, in particular, an electric motor, for example, a brushless direct current (BLDC) motor or a brushless alternating current (BLAC) motor. Other types of electric motors may also be suitable. The drive unit is controlled, for example, by the control device. The drive unit is configured to actively drive the spraying device. In this context, "actively driven" means that the drive unit applies torque to the spraying device. Therefore, "active" driving does not refer to the fact that the spray arm is set in rotation by means of spray nozzles. Active driving can, in particular, be achieved with an adjustable rotational speed.The drive unit can also be configured to stop the spraying device at a specific position or angle of rotation and / or to move the spraying device back and forth.

[0016] The spray device is rotatably mounted and is designed, for example, as a spray arm. The spray device is configured to dispense cleaning solution onto the items being cleaned. For this purpose, the spray device preferably comprises a plurality of spray nozzles from which the cleaning solution is sprayed under pressure. The spray device includes a hydraulic system designed to direct the cleaning solution from a connection port, located, for example, on the axis of rotation of the spray device, to the spray nozzles. The spray device may optionally include one or more satellite spray devices.

[0017] In this context, "washing liquor" refers to any liquid that can be used to rinse dishes in a dishwasher. For example, the washing liquor includes freshly added tap water, deionized tap water, tap water mixed with detergent, and similar liquids. The washing liquor may also contain soiling removed from the dishes.

[0018] The detection unit of the drive device includes, for example, a Hall sensor, an optical encoder, an incremental encoder, or the like.

[0019] Additionally or alternatively, the detection unit can be based on measuring the zero-crossing voltage of a voltage induced in a motor winding of the electric motor, in particular the back EMF. Advantageously, the back EMF is already evaluated for the control of the electric motor, so no additional elements are necessary in this case.

[0020] The control device can be implemented in hardware and / or software. In a hardware implementation, the control device can be, for example, a computer or a microprocessor. In a software implementation, the control device can be a computer program, a function, a routine, part of program code, or an executable object.

[0021] The control device is designed to detect a blockage of the spraying device depending on the detected engine speed. For example, the control device analyzes a signal curve of the engine speed and / or compares it with a target value for the engine speed.

[0022] According to one embodiment of the dishwasher, an overload protection device is provided between the electric motor and the spray device, which automatically switches from a coupled state, in which there is a power transmission between the electric motor and the spray device, to a decoupling state, in which the power transmission between the electric motor and the spray device is interrupted, in the event of a blockage of the spray device.

[0023] The overload protection reliably prevents the drive unit from being overloaded. This prevents damage to a drive element or gearbox within the drive unit. The fact that the overload protection "automatically" switches between the coupled and uncoupled states means, in particular, that the overload protection can switch between the coupled and uncoupled states without an active drive element or sensors. In the uncoupled state of the overload protection, the spraying device is no longer actively driven, and the electric motor rotates without load.

[0024] The overload protection preferably triggers at a maximum torque between 0.25 Nm and 2 Nm, preferably between 0.4 Nm and 1 Nm. This limits the force acting on the items being washed, the spray arm, and the drive unit before the overload protection disengages to a low upper limit. At the same time, the maximum torque is high enough that the motor speed of the electric motor drops slightly before the overload protection disengages, allowing the change in motor speed to be reliably detected. It should be noted that a control system for the electric motor, which regulates the motor speed to a predetermined setpoint, for example, must not compensate for the speed drop too quickly, as otherwise the speed fluctuation caused by the blockage may no longer be detected. Therefore, the control system must be set so that the speed fluctuation remains sufficiently large in the event of a blockage.

[0025] According to a further embodiment of the dishwasher, the drive unit is arranged outside the washing tub, wherein an output shaft is provided for transmitting a torque from the electric motor to the spray device, and the overload protection is arranged between the output shaft and the spray device, wherein a rotation angle of the output shaft and a rotation angle of the spray device are in a predetermined ratio to each other when the overload protection is in the coupled state.

[0026] In this embodiment, it is advantageous to infer the rotation angle of the spraying device from the rotation angle of the output shaft when the overload protection is in the coupled state. The rotation angle of the output shaft can, for example, be additionally detected within the drive unit, for instance, using a rotary encoder or an incremental sensor. Alternatively or additionally, the rotation angle of the output shaft can be inferred from the rotation angle of the electric motor.

[0027] The output shaft protrudes into the flushing container, particularly through a wall, and is sealed with a gasket so that no flushing fluid can escape from the flushing container at the output shaft.

[0028] Preferably, the axis of rotation of the output shaft of the drive device and the axis of rotation of the spray arm are arranged parallel to each other and spaced apart from each other.

[0029] In embodiments of the dishwasher, the drive unit comprises a gear unit arranged between the electric motor and the spray device to provide a predetermined gear ratio for driving the spray device.

[0030] In some embodiments, the gearbox unit is arranged between the electric motor and the output shaft.

[0031] The gearbox unit is preferably designed such that the output shaft, and thus also the spraying device, rotates at a speed of 0–20 revolutions per second. The gearbox unit is preferably configured to provide a reduction ratio in the range of 200:1–1000:1. This means, for example, that the electric motor makes 200 revolutions while the output shaft makes only one revolution.

[0032] According to another embodiment of the dishwasher, the control device for determining the blockage of the spray device is set up depending on a comparison of a predetermined target speed and the detected motor speed.

[0033] For example, the target speed at a given time is 500 rpm. If the measured motor speed is different, especially lower, this may indicate a blockage. It should be noted that the target speed may vary at different times during the cleaning program.

[0034] In embodiments, the control device is configured to perform a signal analysis of the detected engine speed and to determine the blockage of the spraying device depending on a result of the signal analysis.

[0035] Signal analysis includes, in particular, calculating a time derivative and / or performing a frequency analysis. Sudden changes in rotational speed, in particular, can be identified by jumps in the time derivative.

[0036] According to another embodiment of the dishwasher, the control device is designed to detect the blockage of the spray device depending on a deviation of the detected motor speed from the target speed by more than a predetermined threshold value.

[0037] For example, the predetermined threshold can be specified as an absolute value, as a relative value that depends on the target speed, and / or a combination of these possibilities. For example, the predetermined threshold can be 50 rpm. Alternatively, the predetermined threshold can be 10% of the target value, for example, 100 rpm with a target of 1000 rpm. Alternatively, the predetermined threshold can be a combination of these, for example, 10% of the target value and at least 50 rpm.

[0038] According to another embodiment of the dishwasher, the control device is designed to issue a warning signal to a user of the dishwasher depending on whether the spray device is blocked.

[0039] For example, the dishwasher includes a loudspeaker for emitting an audible warning signal and / or a display element for emitting a visual warning signal. In preferred embodiments, the dishwasher includes a communication unit configured to transmit the warning signal to an external device, such as a mobile device, in particular a smartphone, a computer, or the like, belonging to the user, wherein the external device is configured to output the warning signal to the user. For example, a corresponding application runs on the external device, which, upon receiving the warning signal from the dishwasher, triggers the output of a warning to the user.

[0040] This way, the user can be notified if a blockage occurs. The user can then, for example, manually resolve the blockage and / or notify customer service.

[0041] According to one aspect, a system comprising the dishwasher as described in the first aspect and an external device is proposed. The dishwasher includes a communication unit configured to transmit a notification signal to the external device. The external device is configured to output the notification signal to the user. For example, a corresponding application runs on the external device, which, upon receiving the notification signal from the dishwasher, triggers the output of a notification to the user.

[0042] In the dishwasher, according to the first aspect, the control device is set up to determine a blockage position of the spray device.

[0043] The blockage position includes a rotation angle of the spray device.

[0044] The blockage position can be derived, for example, from the position of the electric motor at which the blockage is detected. If no overload protection device is arranged between the electric motor and the spraying device, meaning that the electric motor and the spraying device are permanently coupled, there is a proportionality between the motor position and the position of the spraying device determined by the drive train. If an overload protection device is present, then the electric motor rotates independently of the spraying device in the decoupling state. In this case, the overload protection device is preferably designed such that the coupled state can only be established in a specific relative rotational position between the electric motor and the spraying device or, if present, an output shaft and the spraying device.With each revolution of the electric motor or output shaft, this position is reached once, causing the overload protection to engage. If the blockage is still present, the overload protection will then disengage. This engagement / disengagement can be determined based on the measured motor speed. The motor position at which disengagement first occurred thus corresponds to the blockage position of the spraying device.

[0045] In the dishwasher described in the first aspect, the control device is designed to issue a notification to the dishwasher user depending on the detected blockage position. The notification includes the blockage position. For example, the notification can include a graphical representation of the blockage position. This allows the user to easily check the blockage and, if necessary, clear it.

[0046] According to another embodiment of the dishwasher, the control device is designed to reverse the direction of rotation of the electric motor in the event of a blockage of the spray device.

[0047] When the direction of rotation of the electric motor is changed, the direction of rotation of the actively driven spray nozzle also changes. This means that the spray nozzle moves away from the position where the blockage is located. Depending on the nature of the blockage, for example, an item protruding into the spray nozzle's range of motion, the blockage can also occur in the opposite direction of rotation. If the blockage was caused by contamination, the contamination may be removed by changing the direction of rotation.

[0048] According to a further embodiment of the dishwasher, a detection unit is provided for detecting a movement of the spray device, wherein the control device is set up to determine the blockage of the spray device depending on the detected motor speed and the detection of the movement of the spray device.

[0049] In this embodiment, the blockage of the spray device can be verified. The detection unit can, for example, comprise a rotary encoder on a drive shaft of the spray device, a Hall sensor that detects when the spray device passes over a specific position in the rinsing container (the spray device being equipped with a magnet), or a camera that detects movement of the spray device based on image analysis. The implementation of the detection unit as a Hall sensor in combination with a magnet arranged in or on the spray device is particularly advantageous, since the Hall sensor can then be located outside the rinsing container.

[0050] According to a further embodiment of the dishwasher, the control device is designed to determine an angular range in which the spray device is freely rotatable and to control the electric motor in such a way that the spray device only rotates in the determined angular range.

[0051] In this embodiment, two blockage positions are determined in particular, wherein the angular range between the two blockage positions is the free angular range.

[0052] For example, the spray device is designed as a spray arm comprising two opposing arms of equal length. When rotating in one direction, a blockage is detected at an angle of approximately 90°. The spray arm is then rotated in the other direction, and another blockage is detected at an angle of approximately 270°, i.e., after about half a rotation of the spray arm. Each blockage position corresponds to contact between the arms of the spray arm. In this case, the control device activates the drive mechanism to rotate the spray arm back and forth between 90° and 270°. In this way, cleaning of the items being washed can still take place despite the presence of a blockage.

[0053] According to another embodiment of the dishwasher, the control device is set up to adjust a torque provided by the electric motor.

[0054] For example, the control device monitors the drive current with which the electric motor is operated and / or a voltage applied to the electric motor. This can be done, for example, by setting a duty cycle.

[0055] In particular, limiting the torque can be advantageous to force the electric motor to stop even if an overload protection device is present. For this to work, the torque must be set so that it is insufficient to trigger or disengage the overload protection. Therefore, if a blockage occurs, the electric motor will also stop. This allows a motor position corresponding to the blockage position to be determined.

[0056] According to the first aspect, the control device is designed to immediately after a dishwasher door is closed, to control the electric motor in such a way that the spray device performs at least one complete revolution in the wash tub.

[0057] This has the advantage that it detects immediately after the door closes whether a blockage exists. If a blockage is present, the user, who in this case is still near the dishwasher, can be notified accordingly and preferably resolve the blockage directly.

[0058] This movement of the spraying device can also be described as a test run.

[0059] In some embodiments, the test run is only provided if the user has programmed the start of a washing program.

[0060] In further embodiments, the test run can be performed every time the door is closed. In preferred embodiments, the test run is performed whenever a change in the dishwasher's load of dishes is detected. The change in load can be determined, for example, based on an image of the dishes being washed and / or a weight measurement.

[0061] In embodiments of the dishwasher, the spray device comprises a lower spray arm, an upper spray arm and / or a roof-mounted rotating element.

[0062] Each spray arm comprises, in particular, an actively driven boom and may include a spray arm satellite rotatably mounted on the boom. The spray arm satellite is preferably not actively driven, but is driven by means of a spray solution ejected from its spray nozzles.

[0063] According to a second aspect, a method for operating a dishwasher, in particular a household dishwasher, is proposed, comprising at least one spray device driven by a drive unit for spraying dishes arranged in a dishwasher tub with a washing solution. In a first step, an electric motor of the drive unit is activated to actively drive the spray device. In a second step, the motor speed of the electric motor of the drive unit is measured. In a third step, a blockage of the spray device is determined as a function of the measured motor speed. The electric motor is activated immediately after the dishwasher door is closed, such that the spray device completes at least one full rotation in the dishwasher tub.A blockage position of the spray mechanism is determined, which includes a rotation angle of the spray mechanism. A message containing the blockage position is displayed to the dishwasher user, depending on the determined blockage position.

[0064] The embodiments and features described for the proposed dishwasher apply accordingly to the proposed method. This method has the same advantages as explained with reference to the dishwasher.

[0065] According to a third aspect, a computer program product is proposed which includes instructions that, when the program is executed by a computer, cause it to perform the procedure according to the second aspect.

[0066] A computer program product, such as a computer program tool, can be provided or delivered from a server on a network, for example, as a storage medium such as a memory card, USB stick, CD-ROM, DVD, or as a downloadable file. This can be done, for example, in a wireless communication network by transmitting the corresponding file containing the computer program product or tool.

[0067] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0068] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures. Fig. 1 shows a schematic perspective view of an embodiment of a dishwasher; Fig. 2 shows a schematic section through another embodiment of a dishwasher; Fig. 3 shows an exemplary diagram of the rotation angle of an output shaft and a measured engine speed; and Fig. 4 shows a schematic block diagram of an exemplary embodiment of a method for operating a dishwasher.

[0069] In the figures, identical or functionally equivalent elements have been given the same reference symbols, unless otherwise indicated.

[0070] The Fig. 1 Figure 1 shows a schematic perspective view of an embodiment of a dishwasher 1, which is designed here as a household dishwasher. The household dishwasher 1 comprises a wash tub 2, which can be closed by a door 3, in particular in a watertight manner. For this purpose, a sealing device can be provided between the door 3 and the wash tub 2. The wash tub 2 is preferably cuboid in shape. The wash tub 2 can be arranged in a housing of the household dishwasher 1. The wash tub 2 and the door 3 can form a wash chamber 4 for washing dishes.

[0071] Door 3 is in the Fig. 1 The door 3 is shown in its open position. It can be opened or closed by pivoting it about a pivot axis 5 located at its lower end. The door 3 can be used to open or close a loading opening 6 of the wash tank 2. The wash tank 2 has a base 7, a top 8 opposite the base 7, a rear wall 9 opposite the closed door 3, and two opposing side walls 10 and 11. The base 7, the top 8, the rear wall 9, and the side walls 10 and 11 can, for example, be made of stainless steel. Alternatively, the base 7 can, for example, be made of a plastic material.

[0072] The household dishwasher 1 further comprises at least one dishware holder 12 to 14. Preferably, several, for example three, dishware holders 12 to 14 can be provided, wherein the dishware holder 12 can be a lower dishware holder or a lower basket, the dishware holder 13 an upper dishware holder or an upper basket, and the dishware holder 14 a cutlery drawer. As the Fig. 1 As further shown, the dishware holders 12 to 14 are arranged one above the other in the washing container 2. Each dishware holder 12 to 14 can be selectively moved into or out of the washing container 2. In particular, each dishware holder 12 to 14 can be pushed or moved into the washing container 2 in an insertion direction E and pulled or moved out of the washing container 2 in an extension direction A opposite to the insertion direction E.

[0073] A spray device 20 is arranged on the base 7. This is, for example, a spray arm. The spray arm 20 can have a satellite spray arm (not shown). The spray arm 20 is designed to dispense cleaning solution onto items arranged in the item holders 12 to 14. The spray arm 20 is rotatably mounted, with a torque for rotating the spray arm 20 being provided by a drive unit 15. The drive unit 15 is preferably arranged outside the wash tank 2, in this example, therefore, under the base 7. The drive unit 15 particularly includes an electric motor 16 (see Fig. 2 ) and a 16A recording unit (see Fig. 2 ) to detect an engine speed 21 (see Fig. 3 ) of the electric motor 16.

[0074] A control device 25 is also arranged on the door 3 of the household dishwasher 1. The control device 25 is configured, for example, to execute a wash program from a number of wash programs. In particular, the control device 25 is configured to detect a blockage of the spray arm 20 depending on the detected motor speed 21. For example, the spray arm 20 without an overload protection device 19 (see Fig. 2 The spray arm 20 is coupled to the electric motor 16 of the drive unit 15. In the event of a blockage of the spray arm 20, the motor speed 21 therefore drops to zero, as the spray arm 20 is stopped, and consequently, so is the electric motor 16. If a blockage is detected, the control device 25 can, for example, control the drive unit 15 so that the spray arm 20 is rotated in the opposite direction. If a blockage also occurs in this direction of rotation, the spray arm 20 can, for example, be rotated back and forth between the two points where the spray arm 20 encounters the obstruction causing the blockage. This can also be described as the oscillating operation of the spray arm 20. This ensures that the dishes are cleaned despite a blockage of the spray arm 20. Additionally, the control device 25 can inform the user of the dishwasher 1 about the blockage.This can be done by issuing an audible and / or visual warning signal and / or by transmitting a message to the user's external device, in particular a mobile device. The user can then react and clear the blockage or contact customer service, unless the blockage is caused by dishwashing items or similar.

[0075] Fig. 2 Figure 1 shows a schematic section through another embodiment of a dishwasher 1. The dishwasher 1 has, in particular, all the features that can be seen in the household dishwasher of the Fig. 1 were explained, even if their presentation in the Fig. 2 was partially waived.

[0076] In the Fig. 2 In particular, a drive train from the drive unit 15 to the actively driven spray device 20 is shown in detail. The drive unit 15 is arranged under the base 7 of the rinsing tank 2. The drive unit 15 comprises an electric motor 16 and a detection unit 16A, which is used to detect a motor speed 21 (see Fig. 3 ) of the electric motor 16. The electric motor 16 drives an output shaft 17. This can be achieved, in particular, by using a gearbox (not shown) that increases or decreases the motor speed 21 by a predetermined factor. The output shaft 17 rotates in accordance with the electric motor 16, and one direction of rotation can be freely adjustable. The rotation of the output shaft 17 is proportional to the rotation of the electric motor 16, with a gearbox ratio representing the proportionality factor. If no gearbox is present, as in the Fig. 2 The proportionality factor shown is 1. The arrow from the electric motor 16 to the output shaft 17 indicates the power transmission.

[0077] The output shaft 17 penetrates the bottom 7 of the rinsing tank 2 and extends into it. The output shaft 17 is sealed, for example, with a shaft seal or the like, so that rinsing fluid cannot escape. In particular, the output shaft 17 is coupled to a coupling unit 18, which is located in the rinsing tank 2. In this example, the coupling unit 18 includes an overload protection device 19. If the spray device 20 becomes blocked, the overload protection device 18 automatically switches from a coupled state, in which there is power transmission between the electric motor 16 and the spray device 20, to a decoupling state, in which the power transmission between the electric motor 16 and the spray device 20 is interrupted. In the coupled state, the overload protection device 18 transmits a force from the output shaft 17 to a drive shaft 20A of the spraying device 20, as indicated by the arrows.

[0078] The spray device 20 is, for example, rigidly connected to the drive shaft 20A and rotates accordingly with it. The overload protection is preferably designed such that the coupling state can be established in exactly one specific relative rotational position between the output shaft 17 and the drive shaft 20A. Thus, in the coupling state, a specific rotational position of the output shaft 17 corresponds to a specific rotational position of the drive shaft 20A and therefore of the spray device 20.

[0079] In embodiments (not shown), the drive unit 15 additionally includes a sensor for detecting the rotational position of the output shaft 17. The sensor is, for example, designed as a magnetic or optical rotary encoder. From the detected rotational position of the output shaft 17, the rotational position of the spray device 20 can be inferred in the coupled state. Thus, the position of any blockage in the spray device 20 is known. Based on the known blockage position, suitable measures can be taken. For example, in a visual notification to the user of the dishwasher 1, the blockage position can be graphically displayed so that the user can easily check the blockage and, if necessary, remove it.

[0080] Fig. 3 shows two diagrams, where the upper diagram shows a rotation angle φ of an output shaft 17 (see Fig. 2 ) and the lower diagram shows a motor speed RPM of an electric motor 16 driving the spraying device 20 (see Fig. 2 ). The two diagrams share a common time axis t. Each diagram represents an exemplary curve, for example, of a dishwasher equipped with an overload protection device 19 (see Fig. 2 ) in the drive train corresponds to how the dishwasher 1 of the Fig. 2 .

[0081] The upper diagram shows the rotation angle 21 of the output shaft 17. As explained above, the output shaft 17 rotates at a substantially constant angular velocity. Changes in the engine speed SIG have a proportional effect on the angular velocity of the output shaft 17.

[0082] The lower diagram shows the recorded motor speed SIG. A control system regulates the motor speed SIG to a setpoint RS for the motor speed SIG. Fluctuations in the motor speed SIG are noticeable at two times t1 and t2. These fluctuations occur in the two depicted revolutions of the output shaft 17 at the same rotation angle φ of the output shaft 17. The fluctuations are counteracted by coupling / discoupling the overload protection 19 when the spraying device 20 (see Fig. 1 or 2The overload protection device 19 is triggered when the spray device 20 is blocked. When the overload protection device 19 is in the coupled state and the spray device 20 is blocked, the drive train becomes strained until the overload protection device 19 trips. This causes the motor speed SIG to drop. When the overload protection device is decoupled, the drive train relaxes again and the motor speed SIG rises sharply. The electric motor 16 now rotates without load, which is why the motor speed SIG may briefly exhibit an elevated value until it is corrected by the control system.

[0083] To determine whether the speed fluctuation is due to a blockage of the spraying device 20, two threshold values ​​th1, th2 are shown. If one or both of these threshold values ​​th1, th2 are exceeded, a blockage of the spraying device 20 can be concluded. The control device 25 (see Fig. 1 ) is therefore, for example, configured to compare the detected engine speed SIG with at least one threshold value th1, th2. For reliable detection of the blockage, it may be advantageous to wait for two or more revolutions of the output shaft 17 to see if the coupling / uncoupling occurs again at the same rotational position of the output shaft 17, as described in the Fig. 3 is shown.

[0084] In addition to and / or as an alternative to comparing the motor speed SIG with threshold values ​​th1, th2, which refer to the setpoint RS, the control device 25 can be configured to determine the local maxima / minima of the motor speed SIG by means of a curve analysis (not shown). For example, if the first time derivative of the motor speed SIG is considered, there would be a zero crossing at each of the local maxima / minima, which can be detected.

[0085] Fig. 4 shows a schematic block diagram of an embodiment of a method for operating a dishwasher 1, for example the dishwasher 1 of the Fig. 1 or the Fig. 2 The dishwasher 1 has at least one drive unit 15 (see Fig. 1 or 2 ) powered spray device 20 (see Fig. 1 or 2 ) for applying pressure to a rinsing container 2 (see Fig. 1 or 2 ) the dishwasher 1 arranges the items to be washed with a wash solution. In a first step S1, an electric motor 16 (see Fig. 2 ) the drive unit 15 to actively drive the spray device 20. In a second step S2, a motor speed SIG (see Fig. 3 ) of the electric motor 16 of the drive unit 15 is detected. In a third step S3, a blockage of the spray device 20 is determined as a function of the detected motor speed SIG.

[0086] In one embodiment, the method additionally comprises the steps described below. Once a blockage of the spray device 20 has been detected, for example as indicated by the Fig. 3 As described, the electric motor 16 is controlled in such a way that the provided torque is insufficient to activate the overload protection 19 (see Fig. 2 ) to resolve this. This can be achieved, for example, by adjusting the duty cycle to reduce the effective voltage at which the electric motor 16 is operated. When the output shaft 17 has completed one full revolution and the overload protection 19 returns to the coupled state, the torque of the electric motor 16 is insufficient to decouple the overload protection 19 again.

[0087] Therefore, the electric motor 16 stops. The angular position of the electric motor 16, corresponding to the blockage position, is stored. The torque limitation is then removed, and the electric motor 16 is rotated in the opposite direction. This also drives the spray device 20 in the opposite direction. The spray device 20 rotates until it encounters the obstacle causing the blockage from the other side. The blockage is determined based on the detected motor speed SIG, and the torque of the electric motor 16 is again limited to determine and store a second blockage position, which corresponds to the other direction of rotation of the spray device 20. This establishes, in particular, an angular range within which the spray device 20 can rotate freely. The spray device 20 can now be pivoted back and forth within this known range.

[0088] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. Reference symbols used:

[0089] 1 Dishwasher 2 Wash tub 3 Door 4 Wash chamber 5 Swivel axis 6 Loading opening 7 Floor 8 Ceiling 9 Back wall 10 Side wall 11 Side wall 12 Dishwashing compartment 13 Dishwashing compartment 14 Dishwashing compartment 15 Drive unit 16 Electric motor 16A Detection unit 17 Output shaft 18 Clutch unit 19 Overload protection 20 Spray device 20A Axle 21 Angle of rotation 25 Control device φ Rotation angle A Withdrawal direction E Insertion direction RPM Speed ​​RSSet speed S1 Process step S2 Process step S3 Process step SIG Motor speed t Time axis t1 Time point t2 Time point th1 Threshold th2 Threshold

Claims

1. Dishwasher (1), in particular a household dishwasher, having least one rotatably mounted spray apparatus (20) that is actively driven by means of a drive facility (15) so as to apply a washing liquor to items to be washed that can be arranged in a dishwasher cavity (2) of the dishwasher (1), wherein the drive facility (15) comprises an electric motor (16) for actively driving the at least one spray apparatus (20) and a detection unit (16A) for detecting a motor rotational speed (SIG) of the electric motor (16), and having a control apparatus (25) that is configured so as, in dependence upon the detected motor rotational speed (SIG), to determine a blockage of the at least one spray apparatus (20), characterised in that the control apparatus (25) is configured so as, immediately after a door (3) of the dishwasher (1) is closed, to actuate the electric motor (16) in such a manner that the spray apparatus (20) performs at least one complete rotation in the dishwasher cavity (2), wherein the control apparatus (25) is configured so as to determine a blockage position of the spray apparatus (20), wherein the blockage position includes an angle of rotation of the spray apparatus (20), and wherein the control apparatus (25) is configured so as, in dependence upon the determined blockage position, to output an alert including the blockage position to a user of the dishwasher (1).

2. Dishwasher according to claim 1, characterised by an overload protection (19) that is arranged between the electric motor (16) and the spray apparatus (20) and in the case of a blockage of the spray apparatus (20), said overload protection moves automatically from a coupling state, in which force is transferred between the electric motor and the spray apparatus, into a decoupling state, in which the transfer of force between the electric motor (16) and the spray apparatus (20) is interrupted.

3. Dishwasher according to claim 2, characterised in that the drive facility (15) is arranged outside the dishwasher cavity (2), wherein an output shaft (17) is provided so as to transfer a torque from the electric motor (16) to the spray apparatus (20) and the overload protection (19) is arranged between the output shaft (17) and the spray apparatus (20), wherein an angle of rotation (21) of the output shaft (17) and an angle of rotation of the spray apparatus (20) are in a predetermined relationship with one another when the overload protection (19) is in the coupling state.

4. Dishwasher according to one of claims 1 - 3, characterised in that the control apparatus (25) is configured so as, in dependence upon a comparison between a predetermined target rotational speed (RS) and the detected motor rotational speed (SIG), to determine the blockage of the spray apparatus (20).

5. Dishwasher according to claim 4, characterised in that the control apparatus (25) is configured so as, in dependence upon a deviation of the detected motor rotational speed (SIG) from the target rotational speed (RS) by more than a predetermined threshold value (th1, th2), to determine the blockage of the spray apparatus (20).

6. Dishwasher according to one of claims 1 - 5, characterised in that the control apparatus (25) is configured so as, in dependence upon determining the blockage of the spray apparatus (20), to output an alert signal to a user of the dishwasher (1).

7. Dishwasher according to one of claims 1 - 6 characterised by a detection unit for detecting a movement of the spray apparatus (20), wherein the control apparatus (25) is configured so as, in dependence upon the detected motor rotational speed (SIG) and the detection of the movement of the spray apparatus (20), to determine the blockage of the spray apparatus (20).

8. Dishwasher according to one of claims 1 - 7, characterised in that the control apparatus (25) is configured so as to reverse a direction of rotation of the electric motor (16) in the case of a blockage of the spray apparatus (20).

9. Dishwasher according to one of claims 1 - 8, characterised in that the control apparatus (25) is configured so as to determine an angular range in which the spray apparatus (20) can freely rotate and to actuate the electric motor (16) in such a manner that the spray apparatus (20) only rotates in the determined angular range.

10. Dishwasher according to one of claims 1 - 9, characterised in that the control apparatus (25) is configured so as to set a torque of the electric motor (16).

11. Method for operating a dishwasher (1), in particular a household dishwasher, having at least one rotatably mounted spray apparatus (20) that is actively driven by means of a drive facility (15) so as to apply a washing liquor to items to be washed that can be arranged in a dishwasher cavity (2) of the dishwasher (1), the method comprising: actuating (S1) an electric motor (16) of the drive facility (15) for actively driving the spray apparatus (20); detecting (S2) a motor rotational speed (SIG) of the electric motor (16) of the drive facility (15), and in dependence upon the detected motor rotational speed (SIG) determining (S3) a blockage of the spray apparatus (20) characterised in that immediately after a door (3) of the dishwasher (1) is closed, the electric motor (16) is actuated in such a manner that the spray apparatus (20) performs at least one complete rotation in the dishwasher cavity (2), a blockage position of the spray apparatus (20) is determined, which includes an angle of rotation of the spray apparatus (20), and an alert including the blockage position is output to a user of the dishwasher (1) in dependence upon the determined blockage position.

12. Computer program product, comprising commands that, when the commands are implemented by a computer, cause the dishwasher of claim 1 to perform the method according to claim 11.

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