Flap for regulating airflow and automotive air conditioning unit

Abstract

The invention relates to a flap (7; 16) for regulating an airflow in a motor vehicle air conditioning unit (15), which can be pivotably installed in a housing of the motor vehicle air conditioning unit (15), comprising a flap body with a hard component (8) made of a sound- and air-impermeable material, wherein at least one perforated recess (12) is formed in the hard component (8), wherein the at least one perforated recess (12) is closed by a cover (13; 19) made of a sound-permeable, sound-absorbing and air-impermeable material. The invention further relates to a motor vehicle air conditioning unit (15) comprising at least one such flap (7, 16).

Description

[0001] The invention relates to a flap for regulating an airflow in a motor vehicle air conditioning unit and to an air conditioning unit in which at least one such flap is installed for the purpose of reducing flow-induced noise.

[0002] The invention is applicable to the reduction of flow-induced noise, particularly in automotive air conditioning systems. The demands placed on automotive air conditioning systems are constantly increasing in terms of performance and functionality, while at the same time, less and less installation space is available. Especially in electric vehicles, the requirements for noise reduction from the air conditioning system are very high, since the combustion engine, as a potential masking or overpowering noise source, is no longer present. Another trend is that manufacturers are avoiding sound-absorbing materials, for example, below the instrument panel, due to cost and weight considerations. This, in turn, facilitates the transmission of noise generated by the air conditioning system into the vehicle's interior.

[0003] The biggest noise source in an air conditioning unit is the blower, including its motor, impeller, and fan shroud. Depending on the arrangement of the unit's components, the blower draws in recirculated air from below the instrument panel. If the recirculation vent is directed towards the A-pillar or into the passenger compartment and is located very close to the blower, this provides a direct path for the sound towards the driver or front passenger. Noise can penetrate the passenger compartment more easily through the air conditioning unit's recirculation vents if these are located not only near the blower and fan shroud, but also near the instrument panel.

[0004] However, it's not only the recirculation vents located near the blower and instrument panel that contribute to the noise level in the vehicle's passenger compartment. The noise also penetrates the passenger compartment through other openings, as the air conditioning unit's exhaust vents and the connecting air ducts also provide a path for sound towards the occupants.

[0005] Both the recirculation opening and the exhaust cross-sections can be opened and closed with flaps. When the flaps are open, sound can escape unhindered.

[0006] All these openings can be opened and closed by means of flaps. When a flap is open, noise can easily escape from the air conditioner. There are no noise reduction features in the outlet and flap areas.

[0007] Previously, the noise level of a vehicle air conditioning unit was reduced, among other things, by optimizing the largest noise source, namely the motor, impeller, and fan shroud. Resonators and absorbers are also known to be used on larger housing components, but these require additional installation space.

[0008] Another problem is posed by noise with a frequency below 500 Hz, which is mostly caused by the resonance of various volumes within the vehicle's air conditioning system. While potential noise pollution problems in the frequency range above 1000 Hz can be solved at the vehicle level with additional effort and expense, this is not possible below 1000 Hz, and especially below 500 Hz. Due to the packing density and the arrangement of all components of an air conditioning system, including the evaporator, filters, and heat exchanger, the various volumes of the vehicle's air conditioning system cannot simply be increased or decreased in such a way as to change the resonance volume sufficiently to reduce the problems in the spectrum below 500 Hz.

[0009] From DE 196 13 875 A1, a flap for an air duct of a heating and / or air conditioning system of a motor vehicle is known, wherein the flap has a flap body assembled from at least two flap parts, which is designed as a hollow body. The flap is pivotably mounted in opposite walls of the air duct about its pivot axis. The hollow body is made of a plastic and is formed from an upper flap part with openings and a flat, closed lower flap part. The upper flap part consists of a flat flap segment with the openings and a curved flap segment extending therefrom. A damping layer, which may consist of a nonwoven or felt material, is located on the outside of the flat flap segment with the openings.

[0010] In JP 2012-232 662 A, an air mixing flap of an air conditioning system is described, wherein the air mixing flap has a plurality of through holes or a plurality of openings penetrating in the thickness direction of the air mixing flap, wherein the through holes or penetrating openings are closed with a sound-absorbing material made of a porous material, for example polyurethane.

[0011] German patent DE 20 2010 016 053 U1 describes a recirculation damper that encloses three resonator chambers. Resonator openings are provided on the walls of the recirculation damper within these chambers, thus enabling the damper to act as a Helmholtz resonator. This resonator significantly increases the absorption of sound incident on the damper, resulting in additional sound attenuation. Furthermore, the surface of the recirculation damper outside the Helmholtz resonator is covered with sound-absorbing material, such as a microporous plastic. The combination of this sound-absorbing material and the Helmholtz resonator on the recirculation damper further enhances sound absorption and attenuation.

[0012] From DE 198 55 360 A1, a flap for an air duct of a motor vehicle's heating or air conditioning system is known, comprising a flap body with two flap parts connected to each other via a film hinge. These parts can be folded together around a hinge axis of the film hinge and fixed in this folded position by means of fixing elements. To provide an improved flap for an air duct that is lightweight and easy and therefore inexpensive to manufacture, the flap parts are designed as a frame and have openings that can be covered by an insert held between the flap parts. The insert can consist of a foam, fibrous material, paper, or natural fibers such as flax, sisal, or coconut fibers.

[0013] German patent application DE 20 2013 105 639 U1 describes a sound-absorbing element for an air outlet, wherein the air outlet has a housing with an air outlet opening and a connection to an air supply duct. At least one sound-absorbing element is mounted in the housing and / or in a housing of the air supply duct, wherein the sound-absorbing element has a support that is connected to at least one layer of sound-absorbing material. The at least one layer of sound-absorbing material comprises activated carbon, or at least one further layer of activated carbon is applied to the layer of sound-absorbing material.

[0014] The object of the invention is to achieve effective sound absorption in an air conditioning unit while saving installation space, and thus to reduce flow-induced noise.

[0015] The problem is solved by a flap for regulating an airflow in a motor vehicle air conditioning unit according to claim 1. Further developments are specified in the dependent claims.

[0016] The flap is pivotally mounted in a housing of the automotive air conditioning unit and comprises a flap body with a hard component made of a sound- and air-impermeable material, wherein at least one perforated recess is formed in the hard component. For the purposes of this invention, a hard component made of a sound-impermeable material is understood to be a hard component which, due to the material itself and / or its thickness, exhibits reflective properties corresponding to a reflection coefficient of > 0.9. According to the invention, the perforated recess is closed by a cover made of a sound-permeable, sound-absorbing, and air-impermeable material.

[0017] In this way, sound-absorbing elements can be integrated into the flaps of a vehicle air conditioning unit to reduce noise levels, particularly in the frequency range above 1000 Hertz. Ideally, these flaps with integrated sound-absorbing elements can be positioned as close as possible to the largest noise source, the blower, as is usually the case for the recirculation flap. However, flaps positioned further downstream from the blower can also reduce noise propagation with appropriate sound-absorbing elements. Integrating sound-absorbing elements into existing flaps in an air conditioning unit has the advantage that no additional installation space is required.

[0018] According to a non-inventive embodiment, at least one cavity with sound- and air-impermeable walls is formed in the hard component, which is closed by the cover made of the sound-permeable, sound-absorbing, and air-impermeable material. The at least one perforated recess in the hard component can be closed by the cover made of the sound-permeable, sound-absorbing, and air-impermeable material and lead into the at least one cavity formed by the flap, which is otherwise enclosed by sound- and air-impermeable walls.

[0019] The soundproof and airtight walls of the at least one cavity can be formed, at least partially, by a ribbed structure formed on one side of the flap body. The cavity formed on the side opposite the cover made of the soundproof, sound-absorbing, and airtight material can be closed by an additional soundproof and airtight cover wall. Within the scope of the present invention, a soundproof wall or cover wall is understood to be any wall or cover wall that, due to its material and / or its thickness, exhibits reflective properties corresponding to a reflection coefficient of > 0.9. For example, the cover wall can be formed from the same material as the rigid component of the flap, which is typically made of a plastic.

[0020] This variant, which is not according to the invention, can be easily implemented in a space-saving manner, particularly because flaps in the vast majority of cases have a rib structure on the front and / or back for stiffening. The volume occupied by the rib structure can be sealed with a sound-absorbing material, creating a cavity between the sound-absorbing material and the actual flap, i.e., the sound-impermeable material of the flap. Sound strikes the sound-absorbing material and passes through it into the cavity. There, the sound is reflected and exits the cavity again through the sound-absorbing material. Thus, the noise level is reduced, as the sound passes through the sound-absorbing material twice. Additionally, depending on its shape and size, the sound can also be canceled out or attenuated within the cavity.This always occurs when incoming and outgoing waves overlap in such a way that they cancel each other out or weaken. The frequency range that can be addressed by this effect depends on the size and geometry of the cavity. In the case of flaps and the resulting small cavities, a corresponding influence is more likely to be observed in the higher frequency range of the spectrum. In a further development of the above-described non-inventive variant, a plurality of hole-shaped recesses are formed in the hard component of the flap, leading into a plurality of cavities formed by the rib structure. The cavities are closed on the side opposite the sound-permeable, sound-absorbing, and airtight material by a sound- and airtight cover wall resting on the rib structure.

[0021] According to the invention, the cover made of sound-permeable, sound-absorbing, and airtight material does not close a hollow body, but rather, as an acoustic window, closes a perforated recess in the rigid component of the flap and is integrated into the flap body, so that sound can pass through the flap and be partially absorbed by the sound-absorbing material. The particular advantage of this design is that the resulting airtight, but acoustically permeable recess provides an acoustic connection between two volumes separated by the flap in the vehicle air conditioning unit, allowing the communication between these volumes to shift or reduce resonances.

[0022] Various shapes are possible for the perforated recess or acoustic window. According to the invention, the perforated recess and / or the acoustic window each has an oval shape, for example a circular or elliptical shape.

[0023] According to the invention, the sound-permeable, sound-absorbing and air-impermeable material is a nonwoven fabric in each of the embodiments mentioned above.

[0024] Another aspect of the invention relates to a motor vehicle air conditioning unit, which comprises at least one flap according to one of the embodiments described above, which is pivotably installed in a housing of the motor vehicle air conditioning unit for the purpose of regulating the airflow.

[0025] As a recirculation flap that is pivotally mounted in an air intake housing of the vehicle air conditioning unit, the variant described above (not according to the invention) is particularly suitable, in which the cover made of the sound-permeable, sound-absorbing, and airtight material closes a cavity. As already mentioned, this allows a reduction of noise in a higher frequency range, i.e., above 1000 Hertz, to be achieved without the use of additional installation space. However, this approach is not only suitable for the recirculation flap, which is often located very close to the blower and the area of ​​the blower impeller, the main noise source, but also for any type of flap in an air conditioning unit, including the flaps at the air conditioning unit's outlets or even the temperature flaps within the air conditioning unit, which can influence noise propagation and attenuation.

[0026] The acoustic window variant according to the invention is particularly suitable for temperature flaps in automotive air conditioning systems, which are also known as mixing air flaps. When in their end positions, these temperature flaps divide the air distribution housing into specific areas and volumes. These volumes are not acoustically connected. This means that while the temperature flaps close certain flow paths in their end positions, they also close a path for sound propagation. By adding an acoustic window, this path for sound propagation remains open at all times.

[0027] Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1: A perspective sectional view of a blower air intake device of a motor vehicle air conditioning unit, state of the art, Fig. 2A: A perspective view of a recirculation flap looking at its front side, state of the art. Fig. 2B: A perspective view of the recirculation flap looking at its rear side, state of the art. Fig. 3A: a front view of a recirculation flap with a plurality of circular, perforated recesses in the hard component of the flap without showing a cover on the front side, not belonging to the invention, Fig. 3B: a view of the rear side of the recirculation flap showing a rib structure with a plurality of cavities and the plurality of hole-shaped recesses in the hard component of the flap without showing any covers on the rear side, not belonging to the invention, Fig. 4A: a front view of a recirculation flap looking towards a central area covered with a sound-absorbing material, not belonging to the invention, Fig. 4B: a rear view of the recirculation flap showing a ribbed structure with a soundproof and airtight cover on the rear side, not belonging to the invention, Fig. 5: Comparison diagrams showing the reduction of airflow noise in the frequency range above 1000 Hz in warm air mode and in cold air mode when using sound-absorbing material in a recirculation flap, not relating to the invention, Fig. 6: A perspective sectional view of a motor vehicle air conditioning unit with a temperature flap, state of the art, Fig. 7A: a perspective view of a temperature damper with an acoustic window made of a sound-absorbing material, looking at the convexly curved back side, Fig. 7B: a perspective view of the temperature damper with the acoustic window made of a sound-absorbing material, looking at the concave curved front, and Fig. 8: Comparison diagrams showing a reduction in sound pressure level in the frequency range between 200 and 500 Hz when using temperature dampers with an acoustic window made of a sound-absorbing material.

[0028] The Fig. Figure 1 shows a sectional view of a blower air intake device 1 of a motor vehicle air conditioning unit, which is known per se from the prior art. Such a blower air intake device comprises a blower with a blower impeller 2 and a blower screw 3, as well as an air inlet housing with a fresh air opening 4 and a recirculation opening 5, and a fresh air flap 6 and a recirculation flap 7. Using a recirculation flap as an example, it can be shown how a sound-absorbing element can be integrated into a motor vehicle air conditioning unit in a space-saving manner.

[0029] The characters Fig. 2A and Fig. Figure 2B contains perspective views of a recirculation flap 7, the design of which is known from the prior art. The Fig. 2A comprises a front side 7a of the recirculation flap 7, the flap body with a sound- and air-impermeable hard component 8, and a seal 9 circumferentially around the hard component 8. The front side 7a is the side of the recirculation flap along which the air can flow. In contrast, the Fig. 2B the rear side 7b of the recirculation flap 7, which is hardly or not at all exposed to air. The rear side 7b of the recirculation flap 7 has a rib structure 10 consisting of two intersecting groups of parallel ribs, whereby the rib structure forms a plurality of cavities 11, each enclosed by four walls formed by the ribs.

[0030] The characters Fig. 3A, Fig. 3B, Fig. 4A and Fig. Figures 4B, which do not represent the invention, show the possibility of modifying a corresponding recirculation flap and integrating a sound-absorbing element into the modified recirculation flap without requiring additional installation space.

[0031] The Fig. Figure 3A shows the front side 7a of the recirculation flap 7, in which perforated recesses 12 in the form of two parallel rows of circular holes are provided in the flap body. Fig. Figure 3B shows the reverse side of the recirculation flap with the ribbed structure 10, where the perforated recesses 12 are visible. It can be seen that each of the perforated recesses 12 leads from the front side 7a of the recirculation flap 7 into one of the cavities 11 formed by the ribbed structure.

[0032] The Fig. Figure 4A shows the front side 7a of the correspondingly modified recirculation flap 7, in contrast to the illustration in the Fig. 3A The area with the openings is covered with a cover 13 made of a non-woven material and is therefore not visible. This cover 13 is an example of sound-absorbing material. In Fig. 3A shows the position of cover 13 with a dashed line. According to the illustration in the Fig. 4B is the area of ​​rib structure 10 that is not connected to the Fig. 4A still in Fig. The perforated recesses shown in 4B correspond to the recirculation flap 7, which is also provided with a cover 14, but unlike the cover 13 on the front side, this cover 14 is made of a sound- and air-impermeable material. Thus, the rib structure 10, together with the sound- and air-impermeable cover 14 on the rear side 7b and the sound-absorbing material of the cover 13 on the front side 7a of the recirculation flap 7, forms a multitude of closed cavities, wherein in Fig. 3B these cavities 11 are visible and the position of the cover 14 is marked with a dashed line.

[0033] The shape and size of a cavity or many small cavities can be influenced by the shape of the rib structure 10, where the figures Fig. Figure 3B shows only one possible embodiment of a ribbed structure. The sound-reducing effect of this construction can be described as follows: Sound enters the cavity 11(s) through the nonwoven material, is reflected, and exits again through the nonwoven material. Thus, the sound passes through the nonwoven material twice and is absorbed accordingly.

[0034] This principle is applicable to any type of flap in a vehicle air conditioning system. However, its application in the recirculation flap is particularly relevant, especially when, as in the case of the... Fig. In the arrangement shown in Figure 1, the recirculation flap is positioned directly above the blower and is therefore very close to the largest noise source.

[0035] Sounds are created by vibrations and propagate through the air as sound waves. The intensity of the sound, or its loudness, is measurable. The measured quantity is called sound pressure, and the displayed measurement is the sound pressure level, expressed in decibels (dB). A sound event manifests as the smallest pressure fluctuation around atmospheric pressure; this vibration is perceived by the ear. The perceived loudness of a sound event is fundamentally determined by this sound pressure and also by the frequency. The frequency, that is, the number of vibrations per second, determines the "pitch." The higher the frequency, the higher the pitch of the sound is perceived.

[0036] In Fig. Figure 5 shows that when using a modified recirculation flap as described above in an air conditioning unit, a reduction in the sound pressure level (L or SPL) is achieved in the frequency range above 1000 Hz, both in heating mode and in cooling mode of the vehicle air conditioning unit, compared to a measurement with a conventionally designed recirculation flap (base).

[0037] Another example of integrating a sound-absorbing element into a damper of an air conditioning unit is explained below using a modified temperature damper or mixing air damper as an example. Fig. Figure 6 shows a perspective sectional view of a motor vehicle air conditioning unit 15, which has a temperature flap 16 that, in its end positions, either closes the cold air path, which leads directly from a heat exchanger (evaporator 17) for cooling and dehumidifying the air into a mixing chamber, or the warm air path, which leads through a heating heat exchanger 18 to heat the air before it reaches the mixing chamber. In the version shown Fig. In the position shown in Figure 6, the temperature flap 16 closes the cold air path, so that the entire volume of air passing through the evaporator 17 then flows through the heating heat exchanger 18 to heat the air. As a result, in this position, no sound can propagate through the cold air path in the air conditioner. Depending on the geometric design of the air conditioner, this can lead to resonances, which can be avoided by allowing sound to propagate through the cold air path nonetheless.

[0038] This is made possible by the integration of a so-called acoustic window into the temperature flap 16, as shown in the figures. Fig. 7A and Fig. 7B is shown schematically. This shows Fig. 7A the temperature flap 16 with a view to the convexly curved back side 16a and the Fig. 7B with a view of the concave curved front 16b. The acoustic window is rectangular in the illustration shown, but according to the invention has an oval shape, is positioned centrally in each case and consists of sound-permeable but also sound-absorbing material.

[0039] An acoustic window can be integrated into the damper body of the temperature damper 16 by closing a recess 12, usually created by cutting a hole, in the hard component of the temperature damper 16 with a cover 19 made of sound-permeable and sound-absorbing material, the acoustic window. The position of the perforated recess 12 is specified in the Fig. 7A and Fig. 7B is shown with a dashed line. The material of the acoustic window, which according to the invention is an acoustic nonwoven fabric, is simultaneously airtight, thus enabling the in Fig. In the final position shown in Figure 6, which closes off the cold air path of the air conditioner, all air must continue to flow over the heating heat exchanger 18.

[0040] Due to the sound permeability of the material of the acoustic window, the volume of an air distribution housing, which is blocked for the airflow by a completely closed temperature flap 16 (mixing air flap), can be used as a resonance volume to address certain frequencies and reduce the amplitude of these frequencies in the spectrum.

[0041] The Fig.Figure 8 contains three comparison diagrams showing a reduction in the sound pressure level in the frequency range between 200 and 500 Hz when using a temperature damper operating in cooling mode, defrost mode, and heating mode, respectively, each damper incorporating an acoustic window made of sound-absorbing material. This test shows an improvement in all three diagrams in the form of a reduction in the sound pressure level, primarily in the frequency range between 200 and 500 Hz, compared to a standard temperature damper (baseline).

[0042] The perforated recess in the temperature damper, and the sealing of this recess with an acoustic window (made of nonwoven fabric according to the invention), separates the different volumes from one another with respect to the airflow, but allows them to be acoustically connected through the nonwoven fabric. Therefore, the volumes in the air distribution housing can be used as a resonator to reduce the peak of certain frequencies in a spectrum. The example shows a problematic peak in the 300 Hz range, which can be reduced by the modified temperature dampers. Reference symbol list 1 Blower air intake device 2 blower impeller 3 blower screw 4 Fresh air opening 5 Recirculation opening 6 Fresh air flap 7 Recirculation flap 7a front side of the recirculation flap 7b rear side of the recirculation flap 8 Hard component 9 circumferential seals 10 rib structure 11 Cavity 12 hole-shaped recesses 13 Cover made of sound-permeable, sound-absorbing and airtight material 14 Cover made of soundproof and airtight material 15 Automotive air conditioning unit 16 Temperature flap 16a convex curved back side of the temperature flap 16b concave curved front of the temperature flap 17 evaporators 18 heating heat exchangers 19 Cover (acoustic window)

Claims

A flap (16) for regulating an airflow in a motor vehicle air conditioning unit (15), which can be pivotably installed in a housing of the motor vehicle air conditioning unit (15), comprising a flap body with a hard component (8) made of a sound- and air-impermeable material, wherein at least one perforated recess (12) is formed in the hard component (8), wherein the at least one perforated recess (12) is closed by a cover (19) made of a sound-permeable, sound-absorbing and air-impermeable nonwoven fabric, characterized in that the cover (19) made of the sound-permeable, sound-absorbing and air-impermeable nonwoven fabric does not close a hollow body, but rather, as an acoustic window, closes a perforated recess (12) in the hard component (8) of the flap (16) and is thereby integrated into the flap body of the flap (16).so that the sound can pass through the flap (16) and be partially absorbed in the sound-absorbing material, and that the perforated recess (12) and / or the acoustic window each have an oval shape. Motor vehicle air conditioning unit (15), comprising at least one flap (16) according to claim 1, which is pivotably installed in a housing of the motor vehicle air conditioning unit (15) for regulating the airflow. Motor vehicle air conditioning unit (15) according to claim 2, characterized in that a flap (16) according to claim 1 is pivotably installed as a temperature flap (16) in the housing of the motor vehicle air conditioning unit (15).

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