EP4018898A1 - Household appliance with a fan and a flow duct - Google Patents

Abstract

The invention relates to a household appliance (1), in particular a soil cultivating appliance, having an appliance housing (2), a fan (3) arranged in the appliance housing (2), an outlet opening ( 4) and a flow channel (5) which connects the outlet opening (4) to the fan (3) in a flow-conducting manner, with the fan (3) generating sound waves which cause resonances within the flow channel (5) which are characterized by standing waves are formed between opposite inner walls (10) of the flow channel (5). In order to improve the efficiency of the noise reduction, it is proposed that a noise reduction wall (6) be positioned in the flow duct (5), the wall plane of which is oriented parallel to a main flow direction (s) of the air flow guided in the flow duct (5), the noise reduction wall (6) is positioned in the flow duct (5) in such a way that a maximum of a velocity amplitude (9) of a sound velocity of the air flow guided in the flow duct (5) lies in the wall plane of the sound reduction wall (6), and with the sound waves penetrating the Form a sound reduction wall (6) between the opposing inner walls (10) of the flow channel (5).

Description

field of technology

The invention relates to a household appliance, in particular a soil cultivation appliance, with an appliance housing, a fan arranged in the appliance housing, an outlet opening formed in the appliance housing behind the fan in the direction of flow, and a flow channel which connects the outlet opening to the fan in a flow-conducting manner, with sound waves passing through the fan are generated, which cause resonances within the flow channel, which are characterized by standing waves that form between opposite inner walls of the flow channel.

State of the art

Household appliances of the aforementioned type are known in the prior art. These are, for example, soil treatment devices, in particular vacuum cleaning devices, with a blower for sucking up dust and dirt from a surface to be cleaned. The suction material is usually transferred into a suction material chamber by means of the blower and collected there, while air that has been cleaned through a filter flows to the blower and finally to the outlet opening.

The operation of the fan and the associated rotation of the fan blades generate sound waves which are inevitably audible to a user when the household appliance is in operation. In order to reduce the background noise associated with this to such an extent that the user does not find it disturbing, silencers are known in the prior art, which are introduced into the appliance housing of the household appliance.

Furthermore, it is known in the prior art, for example in the field of pipe silencers for air ducts, to equip flow ducts from the inside with a perforated support structure that carries an acoustic foam or a fleece. As a result, the pressure loss increases so that, in relation to a vacuum cleaning device, suction material can no longer be removed from a surface to be cleaned as well as would be the case, for example, without such a silencer. In order to compensate for the negative effect on the efficiency of the silencer, the vacuum cleaning device would have to be equipped with a more powerful blower or drive motor.

Summary of the Invention

Based on the aforementioned prior art, it is therefore the object of the invention to develop a household appliance of the aforementioned type in such a way that noise emitted by the fan is optimally reduced, while at the same time the suction power is affected as little as possible by the noise reduction measure.

To solve this problem, it is proposed that a sound reduction wall is positioned in the flow duct, the wall plane of which is oriented parallel to a main flow direction of the air flow guided in the flow duct, with the sound reduction wall being positioned in the flow duct such that a maximum velocity amplitude of a sound velocity of in the air flow guided in the flow duct lies in the wall plane of the sound reduction wall, and wherein the sound waves form between the opposite inner walls of the flow duct, penetrating the sound reduction wall.

According to the invention, a sound-reducing wall is thus introduced into the flow channel or formed there in such a way that the wall plane of the sound-reducing wall lies exactly where the velocity amplitude of the sound velocity has a maximum. The sound reduction wall is thus at a distance from the inner wall of the flow channel and lies essentially in the center within an opening cross section of the flow channel, namely where the sound velocity has a maximum. As a result, the sound-absorbing sound reduction wall is located exactly where a particularly large amount of sound energy is conducted in the air flow. Since the noise reduction wall also runs parallel to the main flow direction of the air flow in the flow channel, the air flow is not significantly impeded, so that the suction power of the fan or household appliance remains as high as possible. In other words, the sound reduction wall is arranged within the flow channel of the household appliance in such a way that the air flow conveyed by the fan can flow to the outlet opening within the flow channel with the lowest possible pressure loss, while on the other hand the sound generated by the fan is optimally reduced. The sound reduction wall is oriented essentially parallel to the direction of the air flow within the flow duct, while the sound waves form between the opposite inner walls of the flow duct, ie transversely thereto. As a result, the air flow generated by the blower can flow through the flow channel with as little pressure loss as possible, while at the same time optimal acoustic absorption takes place by means of the sound reduction wall arranged at the maximum of the sound velocity. In contrast to the prior art, it was thus recognized that the known damping measures are arranged too close to the inner wall of the flow channel, where the sound velocity has already reached a minimum amplitude and sound energy can therefore not be effectively absorbed. By the sound reduction wall placed according to the invention an efficiency of noise reduction to pressure drop can be improved up to 2:1 or even beyond.

The household appliance which has such a noise reduction wall according to the invention can in particular be a floor treatment appliance, in particular a cleaning appliance, which has a suction opening and a suction material chamber arranged in the main flow direction between the suction opening and the fan. The sound reduction wall is particularly preferably positioned in the flow channel between the fan and the outlet opening. This means that the noise reduction wall is located on the pressure side or outlet side of the fan and is therefore arranged where the disruptive noise of the fan propagates through the air flow guided in the flow channel. The sound reduction wall is preferably connected to opposite partial areas of the inner wall of the flow channel. Techniques such as gluing, welding or the like can be used for the connection. The noise reduction wall can also be held by a support structure, which in turn is attached to the inner wall of the flow channel.

It is proposed that the sound reduction wall is arranged centrally in the flow channel in relation to an opening cross section of the flow channel. In particular, this relates to an embodiment in which the flow channel is embodied symmetrically in a cross section (transverse to a longitudinal extension oriented in the main flow direction) and the sound reduction wall runs through a center of symmetry of the flow channel. Sound waves generated by the fan of the household appliance cause resonances, which are characterized by so-called standing waves, which form between opposing partial areas of the flow channel. The standing waves are caused by reflections from the reverberant inner walls of the flow channel, which do not allow any absorption of sound energy. In contrast, the phase-shifted sound velocity has an amplitude approaching zero on the reflecting hard inner walls. Rather, the amplitude maximum of the sound velocity is located in a geometric center between the opposing partial areas of the inner wall of the flow channel. The sound velocities of all resonance wavelengths of the sound propagating in the flow channel have a maximum in the center of a flow channel that is symmetrically designed in relation to the cross section. It is essential that the maximum amplitude of the sound velocity is in the middle of the flow channel, while the minimum amplitude of the sound velocity occurs on the reflecting inner walls of the flow channel. This applies to all modes propagating in a standing position in the opening cross section. Cross-sectional shapes which correspond to a circular, oval or rectangular shape are preferred for the flow channel. The sound reduction wall is preferably arranged in the respective flow channel in such a way that the sound reduction wall forms a plane of symmetry of the cross-sectional shape of the flow channel.

Furthermore, it is proposed in particular that an inner wall of the flow duct and the sound reduction wall are at a distance from one another transversely to the main flow direction, which corresponds to a quarter wavelength (λ/4) of a sound wave emitted by the fan. The flow channel is thus designed to match the resonance frequencies of the flow channel in such a way that the wavelength of an acoustically dominant sound wave and the width of the flow channel are matched to one another, namely in such a way that the distance between the sound reduction wall and the inner wall of the flow channel corresponds to a quarter wavelength. In principle, it is also possible to arrange several sound reduction walls parallel to one another within the flow channel if there are several relevant resonance wavelengths or relevant secondary maxima. namely, for example, on the one hand in the middle of the flow channel and on the other hand, for example, in a plane which is arranged centrally between the sound reduction wall arranged centrally in the flow channel and the inner wall of the flow channel.

It is suggested that the sound reduction wall comprises a fleece material or foam material. The fleece material or foam material forms a flow-permeable noise reduction element, which ensures that the noise can propagate transversely to the noise reduction wall as unimpeded as possible. In terms of the invention, it is essential that the sound reduction wall is as reflection-free as possible for the sound energy and that a large part of the sound energy is absorbed by the material of the sound reduction wall. The sound energy is absorbed both over the longitudinal extension of the sound reduction wall in the main flow direction of the air flow and transversely to the longitudinal extension of the wall, namely via the wall thickness, ie the thickness of the sound reduction wall. The amount of sound energy absorbed is proportional to the amount of surface area of the acoustically effective sound reducing wall. The material used to form the sound reduction wall can also affect the amount of absorption. It has proven particularly advantageous to use a fiber-reinforced non-woven fabric. Based on the volume, the nonwoven can preferably be 20% to 40% fiber-reinforced. The non-woven fabric is very particularly preferably approximately 30% fiber-reinforced. Furthermore, the non-woven fabric can preferably be woven. In this context, fiber-reinforced means that the nonwoven fabric, which consists in particular of polypropylene or polystyrene, is reinforced with the aid of glass and/or carbon fibers.

Finally, it is proposed that the sound reduction wall has a wall thickness of several millimeters. In particular, a wall thickness of between 1 mm and 10 mm has proven particularly advantageous. The wall thickness is particularly preferably between 3 mm and 6 mm. About the thickness of the sound reduction wall, i. H. their wall thickness, a wavelength range can be set which is optimally absorbed by the sound reduction wall. In this way, even minor changes in the sound wavelength can be compensated for, which are caused, for example, by a slightly changed rotational frequency of the fan or by a minor change in the shape of the flow channel.

Brief description of the drawings

Fig. 1

ein erfindungsgemäßes Haushaltsgerät,

Fig. 2

einen Strömungskanal mit einer Schallreduzierungswand,

Fig. 3

eine Prinzipskizze der Funktion der Schallreduzierungswand.

The invention is explained in more detail below using exemplary embodiments. Show it:

1

a household appliance according to the invention,

2

a flow channel with a noise reduction wall,

3

a schematic diagram of the function of the noise reduction wall.

Description of the embodiments

figure 1 1 initially shows a household appliance 1 in the form of a floor preparation appliance, designed here, for example, as a vacuum cleaner that is manually guided by a user. The household appliance 1 has a handle 12 with which the user can guide the household appliance 1 over a surface to be cleaned in order to suck in suction material, ie dust and/or dirt, into a suction material chamber 8 . The household appliance 1 has an electric motor-driven blower 3 which sucks up material from a suction opening 7 sucks into the suction material chamber 8. The suction material is filtered out of the sucked-in air by means of a filter element 11 assigned to the suction material chamber 8 , so that only cleaned air flows further to the blower 3 . In the direction of flow behind the fan 3, ie on the pressure side of the fan 3, there is a flow channel 5 which leads to an outlet opening 4. The outlet opening 4 is located on a wall of an appliance housing 2 of the household appliance 1. The flow channel 5, starting from the fan 3 to the outlet opening 4, specifies a main flow direction s for the air flow guided in the flow channel 5. Instead of the embodiment shown here merely as an example, the flow channel 5 can also have a different shape, for example a rectangular cross section instead of a round cross section. The flow channel 5 can also run in a straight line to the outlet opening 4 instead of being curved. Furthermore, it is possible for the cross-sectional shape of the flow channel 5 to change in the direction of the longitudinal extension.

A sound reduction wall 6 is arranged in the flow channel 5, which consists here, for example, of a fiber-reinforced non-woven fabric. A wall thickness d of the sound reduction wall 6 is here, for example, approximately 4 mm or less. In the exemplary embodiment here, the sound reduction wall 6 in the flow channel 5 runs completely from the fan 3 to the outlet opening 4. However, it is also possible for the sound reduction wall 6 to be formed over only part of the length of the flow channel 5 and, for example, to be only a few centimeters. The sound reduction wall 6 particularly preferably extends centrally within the flow channel 5, possibly even parallel to opposite inner walls 10 of a flow channel 5 with a rectangular cross section.

figure 2 shows a cross section of the flow channel 5 transverse to a longitudinal extent of the flow channel 5 in the main flow direction s. As shown, the sound reduction wall 6 is arranged centrally within the flow channel 5, which is round in this case by way of example, in such a way that the sound reduction wall 6 forms a plane of symmetry of the cylindrical flow channel 5. On both sides of the noise reduction wall 6 there is an identical distance a to a respective partial area of an inner wall 10 of the flow channel 5. In addition to the cylindrical shape of the flow channel 5 shown here, other shapes are also conceivable, as already mentioned, for example an oval or rectangular cross-sectional shape of the flow channel 5. It is essential that the sound reduction wall 6 is designed and arranged within the flow channel 5 in such a way that the sound reduction wall 6 runs parallel to the main flow direction s within the flow channel 5 on the one hand and is arranged centrally in the flow channel 5 on the other hand, namely in such a way that the distances a on both sides of the sound reduction wall 6 are identical. The flow channel 5 can also only have a sound reduction wall 6 in sections of its longitudinal extent, or a plurality of sound reduction walls 6 one behind the other.

figure 3 shows a longitudinal section through a portion of the flow channel 5. Two resonance modes with the wavelengths λ/2 and 3 λ/2 are shown as examples. The distance a between the sound reduction wall 6 and the inner wall 10 of the flow channel 5 is dimensioned such that its amount corresponds to a quarter wavelength of a fundamental mode formed within the flow channel 5 . The course of the illustrated vibration modes of the resonance wave reflects the locally varying amplitudes of the sound energy of the resonance wave, ie a velocity amplitude 9 of the sound velocity which is transverse to the main flow direction s of the air flow guided in the flow channel 5 . As in figure 3 recognizable, the speed of sound, and thus also the sound energy, has a maximum in the geometric Center of the flow channel 5, in which the distance a to the adjacent inner wall 10 on both sides of the sound reduction wall 6 is identical. According to the invention, the sound reduction wall 6 is placed in precisely this plane, which is characterized by the maximum of the velocity amplitude 9, in order to absorb the sound energy there by means of the fleece material 24. In the area of the inner wall 10 of the flow channel 5, the velocity amplitude 9 or the sound energy is essentially equal to zero, so that it is not necessary or effective to place a sound absorption material there. The propagation of the standing wave transversely to the sound reduction wall 6 is possible without hindrance, ie as reflection-free as possible, due to the sound-permeable property of the material of the sound reduction wall 6 . Overall, the sound energy of the resonance wave formed in the flow channel 5 is effectively reduced, while at the same time the air flow can flow in the main flow direction s with as little pressure loss as possible through the flow channel 5 in the direction of the outlet opening 4 . The efficiency of the noise reduction wall 6, ie the noise reduction in relation to a pressure loss within the flow channel 5, is for example 2:1 or more, which means a significantly higher efficiency compared to the prior art.

List of References

1 household appliance a Distance 2 device housing i.e Wall thickness 3 fan s main flow direction 4 exit port 5 flow channel 6 sound reduction wall 7 suction port 8th suction chamber 9 speed amplitude 10 inner wall 11 filter element 12 Handle

Claims (8)

Household appliance (1), in particular soil cultivating appliance, having an appliance housing (2), a fan (3) arranged in the appliance housing (2), an outlet opening (4) configured in the direction of flow behind the fan (3) in the appliance housing (2), and a Flow channel (5), which connects the outlet opening (4) to the fan (3) in a flow-conducting manner, with the fan (3) generating sound waves which cause resonances within the flow channel (5) which are characterized by standing waves that between opposing inner walls (10) of the flow duct (5), characterized in that a sound-reducing wall (6) is positioned in the flow duct (5), the wall plane of which is oriented parallel to a main flow direction (s) of the air flow guided in the flow duct (5). is, wherein the sound reduction wall (6) is positioned in the flow channel (5) that a maximum of a velocity amplitude (9) of a sound The speed of the air flow guided in the flow channel (5) lies in the wall plane of the sound reduction wall (6), and the sound waves are formed between the opposite inner walls (10) of the flow channel (5) by penetrating the sound reduction wall (6). Household appliance (1) according to Claim 1, characterized in that the household appliance (1) is a floor treatment appliance, in particular a cleaning appliance, with a suction opening (7) and one arranged in the main flow direction (s) between the suction opening (7) and the fan (3). Suction material chamber (8) is. Household appliance (1) according to Claim 1 or 2, characterized in that the sound-reducing wall (6) is positioned in the flow channel (5) between the fan (3) and the outlet opening (4). Household appliance (1) according to one of the preceding claims, characterized in that the sound-reducing wall (6) is arranged centrally in the flow duct (5) in relation to an opening cross section of the flow duct (5). Household appliance (1) according to Claim 4, characterized in that the flow channel (5) is symmetrical in a cross section transverse to a longitudinal extension oriented in the main flow direction (s) and the sound reduction wall (6) runs through a center of symmetry of the flow channel (5). Household appliance (1) according to one of the preceding claims, characterized in that an inner wall (10) of the flow channel (5) and the sound-reducing wall (6) are at a distance (a) from one another transversely to the main flow direction (s) which is a quarter wavelength ( λ/4) corresponds to a sound wave emitted by the fan (3). Household appliance (1) according to one of the preceding claims, characterized in that the sound-reducing wall (6) has a fleece material or foam material. Household appliance (1) according to any one of the preceding claims, characterized in that the sound reduction wall (6) has a wall thickness (d) of several millimeters, in particular a wall thickness between 1 mm and 10 mm, particularly preferably a wall thickness of 3 mm to 6 mm.

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