Rotation detection for a spray arm in a dishwasher

Abstract

Device for detecting the rotation of at least one spray arm (3) for a liquid (4), wherein a light source (6) serves as a transmitter, wherein a photoreceiver (7) serves as a receiver, wherein a light guide element (8) is assigned to the light source (6) and the photoreceiver (7), wherein at a first location (10) of the light guide element (8) at least a part of the light (9) emitted by the light source (6) is coupled in such a way that the light (9) is guided in the light guide element (8) by means of total internal reflection, wherein at a second location (11) of the light guide element (8), which is spaced apart from the first location (10) in the direction of propagation of the light (9), the light (9') guided in the light guide element (8) is coupled out in such a way that the light (9') is received by the photoreceiver (7) and a signal (13) corresponding to the intensity of the received light (9') is generated,and wherein an evaluation circuit (15) evaluates the generated signal (13) with regard to the rotation of the spray arm (3), characterized in that the evaluation circuit (15) performs a frequency and / or amplitude analysis of the generated signal (13).

Description

[0001] The invention relates to a device for detecting the rotation of at least one spray arm for a liquid according to the preamble of patent claim 1.

[0002] Spray arms for liquids, especially water, are used in household appliances such as dishwashers. For safety reasons, the rotation of the spray arm must be monitored.

[0003] DE 10 2008 003 883A1 discloses a method for detecting the rotation of a spray arm for a liquid. In this method, electromagnetic radiation, in particular light, is emitted from a transmitter. The emitted electromagnetic radiation is coupled at a first location into a guide element, in which the electromagnetic radiation is guided by total internal reflection, at the angle of total internal reflection. As the spray arm rotates, the guide element is wetted by a time-varying portion of the liquid. The electromagnetic radiation guided by total internal reflection is decoupled from the guide element at a second location. The decoupled electromagnetic radiation is received by a receiver, generating a signal corresponding to the received electromagnetic radiation. The temporal change in the signal is then evaluated to detect the rotation.It has been found that the rotation of the spray arm is not always reliably detected. In particular, in cases where the liquid sprayed by the spray arm does not nearly completely hit the guide element, incorrect detection can occur.

[0004] The invention is based on the object of further developing the device for detecting the rotation of a spray arm for a liquid with regard to reliability. In particular, reliable detection of the rotation of the spray arm should be possible even when the sprayed liquid only partially hits the guide element.

[0005] This object is achieved in a generic device by the characterizing features of claim 1.

[0006] In the device according to the invention, a frequency and / or amplitude analysis of the generated signal is performed for evaluation. Advantageously, the rotation of the spray arm can be reliably detected based on the frequency and / or amplitude pattern, even in cases where the sprayed liquid only partially hits the guide element. Further embodiments of the invention are the subject of the dependent claims.

[0007] In a further embodiment, the frequency and / or amplitude of the change in the generated signal can be determined for the purpose of rotation detection. Furthermore, the temporally changing magnitude of the frequency and / or amplitude can be evaluated to detect rotation. Rotation can be reliably detected based on the sequential alternation between a high and a low frequency and / or a large and a small amplitude. In particular, it may be useful to determine the frequency of the amplitude change. If the rotation of several spray arms is to be monitored, the rotation of the respective spray arm can be easily detected based on the pattern contained in the frequency and / or amplitude analysis of the signal.

[0008] The invention provides a device for detecting the rotation of a spray arm for a liquid. In this device, a light-emitting means, in particular a light-emitting diode, serves as the transmitter and a photoreceiver, in particular a phototransistor, serves as the receiver, wherein a light-guiding element is assigned to the light-emitting means and the photoreceiver as the guiding element. At a first point on the light-guiding element, at least a portion of the light emitted by the light-emitting means is coupled in such a way that the light is guided in the light-guiding element by means of total internal reflection, and at a second point on the light-guiding element, which is spaced apart from the first point in the direction of light propagation, the light guided in the light-guiding element is coupled out such that the light is received by the photoreceiver and a signal corresponding to the intensity of the received light is generated.An evaluation circuit evaluates the generated signal with respect to the rotation of the spray arm. According to the invention, the evaluation circuit performs a frequency and / or amplitude analysis of the generated signal.

[0009] In a space-saving and / or compact design, the light-guiding element can be configured as a prism. For energy-efficient operation, the light-emitting diode (LED), in particular an infrared (IR) LED, and / or the photoreceiver can be a phototransistor, in particular an infrared (IR) phototransistor.

[0010] A housing may be provided to protect the device. To expand the functionality of the device, an additional light source for illumination, particularly for the interior lighting, of the household appliance may be arranged in the housing. A cover that is at least partially transparent to the light emitted by the additional light source and can be designed, in particular, in the form of a disc, may expediently be arranged on the housing. In a compact and cost-effective design, the light-guiding element can be arranged on the cover.

[0011] To simplify the assembly of the device, the light source and / or the photoreceiver and / or the additional light source can be arranged on a circuit board in the housing. Furthermore, the cover can be easily attached to the housing using a bayonet lock. This advantageously also allows for easy replacement of the light source. To increase functional reliability, a sealing ring can be located between the cover and the housing on the bayonet lock.

[0012] Finally, the invention also provides a household appliance with a spray arm, such as a dishwasher, in which the rotation of the spray arm can be reliably detected. For this purpose, the household appliance is provided with such a device for detecting the rotation of the spray arm in the form of a rotation sensor. To expand the functionality, interior lighting can also be provided for the household appliance. It may be advantageous for the device for detecting the rotation of the spray arm to be integrated into the interior lighting, in particular by being arranged in a space-saving manner in a housing for the interior lighting.

[0013] For a particularly preferred embodiment of the spray arm rotation detection according to the invention, in which an additional lighting device, for example an LED (light-emitting diode) lighting, can also be integrated, the following can be stated.

[0014] The concept based on the published patent application DE 10 2008 003 883 A1 is to be further developed in such a way that the following disadvantages are essentially avoided: - Reliable detection of the rotation of a spray arm is currently only possible in some cases if the sprayed liquid completely hits the sensor. - The use of additional parts in and / or on the spray arm or in the household appliance using the spray arm is necessary. - Cost-effective standard manufacturing processes are not currently used. - Optional integrated lighting for the appliance is not currently planned.

[0015] The solution to this problem is a concept in which the sensor is designed so that the signal is completely decoupled with every drop of water. An infrared LED couples light into a prism in such a way that the light is totally reflected and hits a photoreceiver. Any water that hits the prism in the relevant area leads to a changed critical angle of total reflection, which causes part of the light to be decoupled and no longer reach the receiver. The rotation of the spray arm can be reliably detected from the signal curve of the receiver circuit using frequency analysis. By detecting different patterns, different spray arms can be detected even if they are not completely aligned with the sensor. In addition, the optional combination of illumination and rotation detection leads to considerable cost savings.Thanks to the principle of total internal reflection, the system requires no additional components within the customer application. Furthermore, the components are designed to ensure reliable rotation detection over a long service life with low power consumption.

[0016] The advantages achieved by the invention are in particular the following: - Reliable rotation detection of at least one spray arm, in particular different spray arms, is made possible by frequency analysis. - It enables the integration of rotation detection and lighting in one product. - It is a durable and efficient solution that eliminates the need for additional individual parts for use in the household appliance. - No replacement of wearing parts is necessary. - The frequency analysis can be integrated in a compact manner on the circuit board. - These are cost-effective standard manufacturing processes for the device according to the invention.

[0017] An embodiment of the invention with various developments and refinements is shown in the drawings and is described in more detail below. Fig. 1 schematically shows a dishwasher with a spray arm and with a device for detecting the rotation of the spray arm, Fig. 2 the device for detecting the rotation of the spray arm Fig. 1 in schematic view, Fig. 3 a diagram of the spray arm rotation detection device Fig. 2 generated signal, Fig. 4 the device for detecting the rotation of the spray arm according to a more detailed embodiment in an exploded view and Fig. 5 the device for detecting the rotation of the spray arm Fig. 4 in perspective and partially cutaway view.

[0018] In Fig. 1 schematically shows a dishwasher 1 with an upper basket 2 for holding the dishes. A spray arm 3 is attached to the lower side of the upper basket 2, from which water 4 emerges during operation, so that the spray arm 3 is set in rotation due to the recoil of the water jet 4. The rotation of the spray arm 3 is detected by a device 5 for detecting the rotation of the spray arm 3, hereinafter also referred to as rotation sensor 5. It is sufficient, as shown in Fig. 1 indicates that the water 4 partially hits the rotation sensor 5, but a complete impact of the water surge 4 on the rotation sensor 5 is not necessary.

[0019] The detailed functionality of the rotation sensor 5 is shown in Fig. 2. The rotation sensor 5 comprises a light source 6, which can be a light-emitting diode. The light source 6 serves as a transmitter for light 9. The rotation sensor 5 further comprises a photoreceiver 7, which can be a phototransistor. The photoreceiver 7 serves as a receiver for the light 9 emitted by the light source 6. A light-guiding element 8 is assigned to the light source 6 and the photoreceiver 7. At a first point 10 of the light-guiding element 8, at least a portion of the light 9 emitted by the light source 6 is coupled in such a way that the light 9 is guided in the light-guiding element 8 largely by means of total reflection. The totally reflected light 9' guided in the light-guiding element 8 is coupled out at a second point 11 of the light-guiding element 8 such that the light 9' is received by the photoreceiver 7. As can be seen from the Fig. 2, the second location 11 is spaced apart from the first location 10 as seen in the direction of propagation of the light 9, 9'. The photoreceiver 7 then generates an electrical signal 13 corresponding to the intensity of the received light 9', which is fed to an evaluation circuit 15.

[0020] If the spray arm 3 rotates, it comes into contact with the rotation sensor 5 once during each rotation, as can be seen from Fig. 1 can be seen. The water surge 4 then partially strikes the light-guiding element 8 and wets its surface with water droplets 4'. Due to the wetting by the water droplets 4', a portion 9" of the light is not totally reflected, but is coupled out at a third point 12 of the light-guiding element 8. As a result, the intensity of the totally reflected light 9' then received at the photoreceiver 7 is now lower, so that the electrical signal 13 of the photoreceiver 7 changes accordingly, corresponding to the proportion of water droplets 4' wetting the surface of the light-guiding element 8, which portion changes over time due to the rotation of the spray arm 3.

[0021] To detect the rotation of the spray arm 3, the temporal change of the signal 13 is evaluated by performing a frequency and / or amplitude analysis of the generated signal 13 for evaluation. Fig. 3 shows a closer look at the electrical signal 13 generated by the photoreceiver 7 over a certain period of time. As can be seen, the signal 13 has alternating ranges in which the signal 13' has a high frequency and / or a large amplitude, and the signal 13" has a low frequency and / or a small amplitude. This is clearly visible in the signal section 14, which is shown again in a temporally expanded form below the signal 13. Thus, the frequency and / or amplitude of the change in the generated signal 13 is determined, with the rotation of the spray arm 3 being recognizable from the temporally changing magnitude of the frequency and / or amplitude. In particular, the rotation can be recognized by the successive alternation between a high and a low frequency and / or a large and a small amplitude. In other words, the signal 13 collapses with each water droplet 4' that strikes the rotation sensor 5.Over a certain time interval x, a recurring pattern in the course of the signal 13 can then be recognized by means of a frequency and / or amplitude analysis, wherein the rotation of the spray arm 3 is detected on the basis of this pattern recognition. If there are several spray arms 3 in the dishwasher 1, which is not shown in detail, the rotation of the respective spray arm 3 can also be detected on the basis of the pattern contained in the frequency and / or amplitude analysis of the signal 13. For evaluation, the evaluation circuit 15 thus carries out a frequency and / or amplitude analysis of the generated signal 13, 13', 13" and then provides a corresponding rotation signal 16 (see . Fig. 2) ready for further processing.

[0022] Instead of visible light 9, the rotation sensor 5 can also operate using other electromagnetic radiation, for example, infrared (IR) radiation. An infrared (IR) light-emitting diode can then be used as the transmitter 6 and an infrared (IR photodiode as the receiver 7. The guide element 8 can be designed as a prism, as shown in Fig. 2 is shown.

[0023] An interior lighting system is also provided for the dishwasher 1. It is then advisable for the device for detecting the rotation of the spray arm 3 to be integrated into the interior lighting system. The detailed design of such a rotation sensor 5, in which an interior lighting system for the dishwasher 1 is also integrated, is described in Fig. 4 and Fig. 5 can be seen.

[0024] The rotation sensor 5 has a housing 17. Inside the housing 17, a further light source 18 for illumination, which consists, for example, of a light-emitting diode and emits light in the visible range, is arranged in the housing 17. A cover 19 in the manner of a disk, which is at least partially transparent to the light emitted by the light source 18, is arranged on the housing 17. The cover 19 is attached to the housing 17 by means of a bayonet lock 20. To seal the interior of the housing 17 with respect to the liquid 4, a sealing ring 21 is located on the bayonet lock 20 between the cover 19 and the housing 17.

[0025] The light source 6 and / or the photoreceiver 7 are arranged on a circuit board 22 in the housing 17 by means of a holder 24. If desired, the additional light source 18 can also be arranged on a holder; in the present case, however, the additional light source 18 is attached directly to the circuit board 22. Furthermore, it is advisable for the light-guiding element 8 to be arranged on the cover 19. In particular, the light-guiding element 8 can be integrated integrally into the cover 19. Finally, a plug connection 23 for connecting the electrical voltage and the signal line to the rotation sensor 5 can be provided on the housing 17.

[0026] The invention is not limited to the described and illustrated embodiment. Rather, it also encompasses all expert developments within the scope of the invention defined by the patent claims. Thus, the invention can be used not only in dishwashers 1 but also in other household appliances or in process engineering. Finally, the invention can also be used to detect the rotation of a spray arm 3 from which a liquid 4 emerges instead of water. Reference symbol list: 1 dishwasher 2 baskets 3 spray arms 4 Water splash / Water / Liquid 4' water drops 5 Device for detecting the rotation of the spray arm / rotation sensor 6 lamps / transmitters 7 photo receivers / receivers 8 Light guide element / guide element 9 (emitted) light (from the lamp) 9' (totally reflected) light 9" (water droplet coupled) light 10 first digit (of light guide element) 11 second position (of light guide element) 12 third place (of light guide element) 13 electrical signal 13' signal (with high frequency) 13" signal (low frequency) 14 Signal section 15 Evaluation circuit 16 rotation signal 17 Housing (of rotation sensor) 18 (additional) lamps 19 Cover 20 bayonet lock 21 Sealing ring 22 circuit board 23 Plug connection 24 bracket QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2008 003 883A1 [0003, 0014]

Claims

[1] Device for detecting the rotation of at least one spray arm (3) for a liquid (4), wherein a light-emitting means (6) serves as a transmitter, wherein a photoreceiver (7) serves as a receiver, wherein a light-guiding element (8) is assigned to the light-emitting means (6) and the photoreceiver (7), wherein at a first point (10) of the light-guiding element (8) at least a portion of the light (9) emitted by the light-emitting means (6) is coupled in such a way that the light (9) is guided in the light-guiding element (8) by means of total reflection, wherein at a second point (11) of the light-guiding element (8), which is spaced apart from the first point (10) in the direction of propagation of the light (9), the light (9') guided in the light-guiding element (8) is coupled out such that the light (9') is received by the photoreceiver (7) and a signal (13) corresponding to the intensity of the received light (9') is generated,and wherein an evaluation circuit (15) evaluates the generated signal (13) with regard to the rotation of the spray arm (3), , characterized by that the evaluation circuit (15) carries out a frequency and / or amplitude analysis of the generated signal (13). [2] Device according to claim 1, characterized by that the light-guiding element (8) is designed as a prism, and that the illuminating means (6) is preferably a light-emitting diode, in particular an infrared (IR) light-emitting diode, and / or the photoreceiver (7) is a phototransistor, in particular an infrared (IR) phototransistor. [3] Device according to claim 1 or 2, characterized bythat a housing (17) is provided, that preferably a further illuminating means (18) for the illumination is arranged in the housing (17), that further preferably a cover (19) which is at least partially transparent to the light emitted by the further illuminating means (18), in particular in the manner of a disc, is arranged on the housing (17), and that even more preferably the light-guiding element (8) is arranged on the cover (19). [4] Device according to claim 1, 2 or 3, characterized by that the illuminant (6) and / or the photoreceiver (7) and / or the further illuminant (18) are arranged on a circuit board (22) in the housing (17), that preferably the cover (19) is fastened to the housing (17) by means of a bayonet catch (20), and that further preferably a sealing ring (21) is located on the bayonet catch (20) between the cover (19) and the housing (17). [5] Household appliance with a spray arm (3), such as a dishwasher (1), characterized by that a device according to one of claims 1 to 4, in particular in the form of a rotation sensor (5), is provided for detecting the rotation of the spray arm (3). [6] Household appliance according to claim 5, characterized by that an interior lighting is provided for the domestic appliance, and that the device (5) for detecting the rotation of the spray arm (3) is integrated into the interior lighting, in particular is arranged in a housing (17) for the interior lighting.

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