Household appliance with fan and flow channel

Abstract

The invention relates to a domestic appliance (1), in particular a floor treatment appliance, having an appliance housing (2), a fan (3) arranged in the appliance housing (2), a discharge opening (4) and a flow channel (5) configured in the appliance housing (2) behind the fan (3) in the flow direction, wherein sound waves are generated by the fan (3), which cause a resonance within the flow channel (5), which is characterized by a standing wave generated between mutually opposite inner walls (10) of the flow channel (5), which fluidically connects the discharge opening (4) to the fan (3).

Description

Technical Field

[0001] This invention relates to a household appliance, particularly a floor treatment appliance, the household appliance having an appliance housing, a fan arranged in the appliance housing, a discharge opening and a flow channel constructed in the appliance housing behind the fan along the flow direction, the flow channel guiding the discharge opening fluidly to the fan, wherein sound waves are generated by the fan, the sound waves causing resonance within the flow channel, the resonance being characterized by standing waves generated between the opposing inner walls of the flow channel. Background Technology

[0002] Household appliances of the aforementioned type are known in the prior art. These household appliances are, for example, floor cleaning devices, particularly suction cleaning devices, that have a fan for sucking dust and dirt from surfaces to be cleaned. Typically, the suction material is transferred to a suction chamber by means of a fan and accumulates there, while cleaned air, filtered, flows toward the fan and ultimately toward the exhaust opening.

[0003] Sound waves are generated by the operation of a fan and the rotation of its blades, and these sound waves are inevitably audible to users when household appliances are in operation. To reduce the associated background noise to a level that does not disturb the user, silencers incorporated into the housing of household appliances are known in the prior art.

[0004] Furthermore, in existing technologies, such as in the field of duct silencers for air ducts, it is known that the flow duct is internally equipped with a perforated support structure that carries acoustic foam or fiber mesh. This results in increased pressure loss, making it impossible for suction cleaning equipment to remove the suction material from the surface to be cleaned as effectively as, for example, without such a silencer. To compensate for the negative impact of the silencer on efficiency, the suction cleaning equipment must be equipped with a higher-performance fan or drive motor. Summary of the Invention

[0005] Therefore, based on the prior art, the technical problem to be solved by the present invention is to improve the type of household equipment so that the noise emitted by the fan is optimally reduced, while minimizing the adverse effects of the noise reduction measures on the suction force.

[0006] To address the aforementioned technical problem, it is proposed that an anechoic wall be positioned within a suction channel, the wall plane of which is oriented parallel to the main flow direction of the airflow guided in the flow channel. The anechoic wall is positioned in such a way that the maximum value of the velocity amplitude of the acoustic particles in the airflow guided in the flow channel lies within the wall plane of the anechoic wall, and that sound waves are generated between the opposing inner walls of the flow channel as they pass through the anechoic wall.

[0007] According to the invention, the sound-absorbing wall is placed or constructed in the flow channel such that the wall plane of the sound-absorbing wall is located at the position where the velocity amplitude of the sound particles is at its maximum. The sound-absorbing wall is thus spaced apart from the inner wall of the flow channel and is located substantially centrally in the opening cross-section of the flow channel, i.e., at the position where the velocity of the sound particles is at its maximum. This ensures that the sound-absorbing wall is accurately positioned in a location where a particularly large amount of sound energy is guided in the airflow. Since the sound-absorbing wall also extends parallel to the main flow direction of the airflow in the flow channel, the airflow is not significantly obstructed, thus maintaining the suction force of the fan or household appliance as high as possible. In other words, the sound-absorbing wall is arranged in the flow channel of the household appliance such that the airflow delivered by the fan can flow towards the exhaust opening within the flow channel with the least possible pressure loss, while optimally reducing the sound generated by the fan. The sound-absorbing wall is oriented substantially parallel to the direction of the airflow in the flow channel, while sound waves are generated between the opposing inner walls of the flow channel, i.e., transversely to the flow channel. This allows the airflow generated by the fan to flow through the flow channel with minimal pressure loss, while simultaneously achieving optimal sound absorption through a sound-absorbing wall positioned at the location of maximum sound particle velocity. It is recognized that, in contrast to existing technologies, known sound-absorbing measures are positioned too close to the inner wall of the flow channel, where the sound particle velocity has already reached its minimum amplitude and therefore cannot effectively absorb sound energy. The sound-absorbing wall installed according to this invention improves the efficiency of sound reduction relative to pressure loss to 2:1 or even higher.

[0008] Household appliances with such a sound-absorbing wall according to the invention are particularly suitable for floor cleaning appliances, especially cleaning appliances, having a suction opening and a suction chamber arranged along the main flow direction between the suction opening and the fan. Particularly preferred is that the sound-absorbing wall is positioned in the flow channel between the fan and the discharge opening. This means that the sound-absorbing wall is located on the pressure side or discharge side of the fan and thus positioned where the fan would generate disruptive noise due to the airflow directed in the flow channel. The sound-absorbing wall is preferably connected to opposing local areas of the inner wall of the flow channel. For example, bonding, welding, or similar techniques can be used for connection. The sound-absorbing wall can also be held in place by a support structure, which in turn is fixed to the inner wall of the flow channel.

[0009] It is recommended that the anechoic wall be centrally located within the flow channel relative to the opening cross-section of the flow channel. This particularly relates to an embodiment in which the flow channel is symmetrically constructed in cross-section (transverse to the longitudinal extension dimension oriented along the main flow direction) and the anechoic wall extends through the center of symmetry of the flow channel. Sound waves generated by the fan of a household appliance cause resonance, characterized by so-called standing waves, which form between opposing local regions of the flow channel. These standing waves are generated by reflections on the acoustically reflective inner walls of the flow channel, which do not absorb sound energy. The phase-shifted sound particle velocities, in contrast, have amplitudes approaching zero on the reflective, rigid inner walls. The maximum amplitude of the sound particle velocities is located at the geometric center between the opposing local regions of the inner walls of the flow channel. The sound particle velocities of all resonant wavelengths of sound propagating in the flow channel have maximum values ​​at the center of the flow channel, which is symmetrically constructed with respect to the cross-section. Importantly, the maximum amplitude of the sound particle velocities is located at the center of the flow channel, while the minimum amplitude occurs on the reflective inner walls of the flow channel. This applies to all modes that propagate in a standing wave manner within an open cross-section. For the flow channel, a cross-sectional shape corresponding to a circle, ellipse, or rectangle is preferred. The anechoic walls are preferably arranged in the respective flow channel such that they form a plane of symmetry of the cross-sectional shape of the flow channel.

[0010] Furthermore, it is particularly recommended that the inner wall of the flow channel and the anechoic wall be spaced apart from each other transversely to the main flow direction, the distance corresponding to a quarter wavelength (λ / 4) of the sound wave emitted by the fan. This design of the flow channel, adapted to its resonant frequency, ensures that the wavelength of the acoustically dominant sound wave matches the width of the flow channel, thus making the distance between the anechoic wall and the inner wall of the flow channel correspond to a quarter wavelength. In principle, it is also feasible to arrange multiple anechoic walls parallel to each other within the flow channel, for example, on the one hand at the center of the flow channel and on the other hand, for example, in the plane between the anechoic wall arranged in the middle of the flow channel and the inner wall of the flow channel, when multiple associated resonant wavelengths or associated submaxima exist.

[0011] It is recommended that the sound-absorbing wall be made of nonwoven or fiber web material or foam material. The fiber web material or foam material constitutes a fluid-permeable sound-absorbing element that allows sound propagation transversely to the sound-absorbing wall to be as unobstructed as possible. Importantly within the scope of this invention, the sound-absorbing wall is as non-reflective as possible to sound energy, and most of the sound energy is absorbed by the material of the sound-absorbing wall. Sound energy is absorbed both longitudinally along the main flow direction of the sound-absorbing wall and transversely to the longitudinal length of the wall, i.e., at the wall thickness, i.e., the thickness of the sound-absorbing wall. The amount of sound energy absorbed is proportional to the amount of acoustically effective surface area of ​​the sound-absorbing wall. Furthermore, the material used to construct the sound-absorbing wall can also affect the amount of absorption. It has proven particularly advantageous to use fiber-reinforced fiber web material. The fiber web material is preferably 20% to 40% fiber-reinforced in volume. Particularly preferred is that the fiber web material is about 30% fiber-reinforced. Furthermore, the fiber web material is preferably woven. Fiber reinforcement refers to the reinforcement of fiber web materials, especially those made of polypropylene or polystyrene, with the aid of glass fibers and / or carbon fibers.

[0012] Finally, it is recommended that the sound-absorbing wall have a wall thickness of a few millimeters. A wall thickness between 1 mm and 10 mm has proven particularly advantageous. A wall thickness of 3 mm to 6 mm is particularly preferred. By adjusting the thickness of the sound-absorbing wall, the optimal wavelength range absorbed by the wall can be adjusted. This also allows compensation for slight variations in the sound wave wavelength, such as those caused by slight changes in the fan's rotational frequency or slight changes in the shape of the flow channel. Attached Figure Description

[0013] The present invention will now be described in detail with reference to the embodiments. In the accompanying drawings: Figure 1 A household appliance according to the invention is shown. Figure 2 A flow channel with a sound-absorbing wall is shown. Figure 3A schematic diagram illustrating the function of the sound-absorbing wall is shown. Detailed Implementation

[0014] Figure 1 First, a household appliance 1 in the form of a floor cleaning device is shown, for example, a vacuum cleaner manually guided by the user. The household appliance 1 has a handle 12, which the user can use to guide the appliance 1 onto the surface to be cleaned, so as to draw in the suction material, i.e., dust and / or dirt, into the suction chamber 8. The household appliance 1 has an electrically driven fan 3, which draws the suction material into the suction chamber 8 from the suction opening 7. The suction material is filtered from the drawn-in air by means of a filter element 11 corresponding to the suction chamber 8, so that only clean air continues to flow towards the fan 3. A flow channel 5 is located behind the fan 3, i.e., on the pressure side of the fan 3, and the flow channel is directed towards the discharge opening 4. The discharge opening 4 is located on the wall of the appliance housing 2 of the household appliance 1. The flow channel 5 defines the main flow direction for the airflow guided in the flow channel 5, with the fan 3 as the starting point and towards the discharge opening 4. Instead of the design shown only as an example here, the flow channel 5 may also have a different shape, such as a rectangular cross-section instead of a circular cross-section. The flow channel 5 may also extend straight toward the discharge opening 4 instead of being curved. Furthermore, it is possible for the cross-sectional shape of the flow channel 5 to change along the direction of its longitudinal extension.

[0015] A sound-absorbing wall 6 is arranged in the flow channel 5, which is here made of, for example, a fiber-reinforced mesh material. The wall thickness of the sound-absorbing wall 6 is here, for example, about 4 mm or less. In the exemplary design shown here, the sound-absorbing wall 6 extends entirely from the fan 3 to the discharge opening 4 in the flow channel 5. However, it is also possible for the sound-absorbing wall 6 to be constructed only for a portion of the length of the flow channel 5 and to have, for example, a length of only a few centimeters. Particularly preferred is that the sound-absorbing wall 6 extends centrally within the flow channel 5, and if necessary, even parallel to the opposing inner walls 10 of the flow channel 5, which are rectangular in cross-section.

[0016] Figure 2A cross-section is shown, extending longitudinally along the main flow direction s, transverse to the flow channel 5. The anechoic wall 6 is centrally arranged in the flow channel 5, which is exemplarily circular, as shown, i.e., arranged such that the anechoic wall 6 forms the plane of symmetry of the cylindrically constructed flow channel 5. The anechoic wall 6 is located at the same distance 'a' as the corresponding local area of ​​the inner wall 10 of the flow channel 5. Besides the cylindrical shape shown here, other shapes of the flow channel 5, such as elliptical or rectangular cross-sectional shapes, can also be considered, as mentioned above. Importantly, the anechoic wall 6 is constructed and arranged within the flow channel 5 such that it extends parallel to the main flow direction on one hand, and is centrally located within the flow channel 5 on the other hand, i.e., arranged such that the distance 'a' is the same as the distance 'a' from the two sides of the anechoic wall 6. The flow channel 5 may also have only one anechoic wall 6 in sections, or multiple anechoic walls 6 arranged sequentially, depending on its longitudinal extension.

[0017] Figure 3 A longitudinal section obtained by cutting a local area of ​​the flow channel 5 is shown. Exemplary two resonant modes with wavelengths λ / 2 and 3λ / 2 are shown. The distance 'a' between the anechoic wall 6 and the inner wall 10 of the flow channel 5 is designed such that the value of this distance corresponds to a quarter wavelength of the fundamental harmonic mode formed within the flow channel 5. The variation in the vibrational modes of the resonant wave reflects the amplitude of the local variation in the acoustic energy of the resonant wave, i.e., the velocity amplitude '9' of the sound particle velocity, which is transverse to the main flow direction 's' of the airflow guided in the flow channel 5. Figure 3 As shown, the sound particle velocity, and thus the sound energy, has a maximum value at the geometric center of the flow channel 5, where the distance between the sound-absorbing wall 6 and the adjacent inner wall 10 is the same on both sides. According to the invention, the sound-absorbing wall 6 is located precisely in the plane characterized by the maximum velocity amplitude 9, so that sound energy is absorbed there by means of the fiber mesh material 24. In the region of the inner wall 10 of the flow channel 5, the velocity amplitude 9 or the sound energy is essentially zero, so there is no need to install sound-absorbing material there, or installing sound-absorbing material there would be ineffective. Due to the sound-permeable properties of the material of the sound-absorbing wall 6, the propagation of standing waves transversely to the sound-absorbing wall 6 is unimpeded, i.e., with as little reflection as possible. Overall, this greatly and effectively reduces the sound energy of the resonant waves formed in the flow channel 5, while simultaneously allowing the airflow to flow through the flow channel 5 towards the discharge opening 4 with the lowest possible pressure loss along the main flow direction s. The efficiency of the sound-absorbing wall 6, i.e., the ratio of sound reduction to pressure loss within the flow channel 5, is 2:1 or higher, which represents a significantly higher efficiency than the prior art.

[0018] List of reference numerals

[0019] 1. Household equipment

[0020] 2 Equipment casing

[0021] 3. Fan

[0022] 4. Discharge opening

[0023] 5. Flow channels

[0024] 6. Soundproof wall

[0025] 7. Suction opening

[0026] 8. Suction chamber

[0027] 9. Sound particle velocity amplitude

[0028] 10 Inner Wall

[0029] 11 Filter elements

[0030] 12 handles

[0031] a distance

[0032] d Wall thickness

[0033] s Main flow direction

Claims

1. A household appliance (1) having a housing (2), a fan (3) disposed within the housing, a discharge opening (4) and a flow channel (5) constructed in the housing (2) behind the fan (3) along a flow direction, the flow channel fluidly connecting the discharge opening (4) to the fan (3), wherein, Sound waves are generated by the fan (3), which resonate within the flow channel (5). The resonance is characterized by standing waves generated between the opposing inner walls (10) of the flow channel (5). The sound-absorbing wall (6) is positioned in the flow channel (5), and the wall plane of the sound-absorbing wall is oriented parallel to the main flow direction (s) of the airflow guided in the flow channel (5). The sound-absorbing wall (6) is positioned in the flow channel (5) such that the maximum value of the velocity amplitude (9) of the sound particle velocity of the airflow guided in the flow channel (5) is located in the wall plane of the sound-absorbing wall (6). The sound waves are generated between the opposing inner walls (10) of the flow channel (5) as they pass through the sound-absorbing wall (6).

2. The household appliance (1) according to claim 1, characterized in that, The household appliance (1) is a floor treatment device, which has a suction opening (7) and a suction chamber (8) arranged along the main flow direction (s) between the suction opening (7) and the fan (3).

3. The household appliance (1) according to claim 1 or 2, characterized in that, The sound-absorbing wall (6) is positioned in the flow channel (5) between the fan (3) and the discharge opening (4).

4. The household appliance (1) according to claim 1 or 2, characterized in that, The sound-absorbing wall (6) is centrally located in the flow channel (5) relative to the opening cross-section of the flow channel (5).

5. The household appliance (1) according to claim 4, characterized in that, The flow channel (5) is symmetrically constructed in a cross-section transverse to the longitudinal extension dimension oriented along the main flow direction (s), and the sound-absorbing wall (6) extends through the center of symmetry of the flow channel (5).

6. The household appliance (1) according to claim 1 or 2, characterized in that, The inner wall (10) of the flow channel (5) and the sound-absorbing wall (6) are spaced apart from each other transversely to the main flow direction (s), the distance corresponding to a quarter wavelength (λ / 4) of the sound wave emitted by the fan (3).

7. The household appliance (1) according to claim 1 or 2, characterized in that, The sound-absorbing wall (6) is made of fiber mesh material or foam material.

8. The household appliance (1) according to claim 1 or 2, characterized in that, The sound-absorbing wall (6) has a wall thickness (d) of 1 mm to 10 mm.

9. The household appliance (1) according to claim 8, characterized in that, The sound-absorbing wall (6) has a wall thickness (d) of 3 mm to 6 mm.

10. The household appliance (1) according to claim 1, characterized in that, The household appliance (1) is a ground treatment device.

11. The household appliance (1) according to claim 2, characterized in that, The household appliance (1) is a cleaning appliance.

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