Patent Application
20190248207
This application claims priority to German Application No. DE 10 2018 202 169.4, filed on Feb. 13, 2018, the contents of which are hereby incorporated by reference in its entirety.
The invention relates to an air flap for an air conditioning system of a motor vehicle. The invention also relates to a method for producing the air flap.
An air flap is provided in an air conditioning system for regulating the air flow in an air duct and in the closed state securely seal the air duct and in the opened state make possible an unobstructed air flow through the air duct. For the reasons mentioned, the air flap has to be torsionally rigid in order to securely seal the air duct in the closed state. Furthermore, the air flap should have a matched contour in order to minimise in the opened state the pressure drop and a noise development at the air flap. Usually, the air flap comprises at least one flap wing which on the one hand extends to a bearing defining a tilting or pivot axis at least in regions radially or in the circumferential direction. Accordingly, the air flap can for example be a one or two-legged flap, drum flap, roll flap.
The professional world always endeavours to reduce the net weight of individual components in a motor vehicle and among others also the net weight of the air flaps in the air conditioning system. To this end, the wall thickness of the flap wings is usually reduced but this results directly in the loss of the bending strength of the flap wings. For this reason, the reduction of the wall thickness or of the net weight of the bearing of the air flap is disregarded, since the same is exposed to a major workload during operation. In order to counteract the loss of the bending strength of the flap wings, the same can be additionally stiffened geometrically through ribs, corrugations or thickened portions. Disadvantageously, the air flow in the air duct is negatively influenced by ribs, corrugations and thickened portions on the flap wings. In particular, a loud noise in the air duct can develop on the fully or partly opened air flap because of this. In addition, the net weight of the air flap stiffened in such a manner significantly increases with increasing dimensions of the flap wings.
Other solutions for reducing the net weight of the air flaps are also known already. In DE 10 2012 209 603 A1 and DE 44 14 483 A1, air flaps are described for example which have a stiff framework covered by a light material. By way of the framework, the bending strength of the flap wings can be increased and the covering makes possible an air-tight lining of the framework. EP 2 072 297 A1 describes an air flap whose the flap wings have a drop-shaped profile. This serves to particularly improve the pressure drop and the noise development in the air duct. From DE 198 14 953 A1 an air flap is known, in which a framework is over-moulded with a foam material. Here, too, the framework is designed to have a good bending strength in order to achieve the bending strength required for the flap wings. Disadvantageously, such air flaps have to be elaborately produced in multiple stages, which involves major costs.
As standard, the air flaps are produced by an injection moulding method from a plastic—for example polypropylene. Following this, a sealing lip—for example consisting of a thermoplastic elastomer—can be additionally injection moulded onto the air flap. The air flaps produced in this manner are subject to warpage which increases with increasing dimensions of the flap wings. The defects of the sealing of the air duct resulting from this have to be offset by the matched shape of the sealing lip or the flap wings, which in turn can result in a major noise development in the air duct. For producing the hybrid components with a reduced net weight, the injection moulding method with a negative stroke is known from DE 10 2014 208 421 A1. There, a blowing agent is admixed to a plastic melt and a component mould filled with the plastic melt enlarged by a negative stroke of mould parts. Because of this, the plastic melt is foamed in the component mould and the wall thickness as well as the bending strength of the hybrid component increased with a net weight remaining. However, such an injection moulding method is not directly usable for producing an air flap for an air duct because of a high complexity of the components and, in particular, flap bearings.
In summary, a reduction of the net weight of the air flap according to the known prior art involves major design and production expenditure combined with high costs.
The object of the invention therefore is to state an improved or at least alternative embodiment for an air flap of the generic type with which the described disadvantages can be overcome. A further object of the invention is to provide a method for producing the air flap.
According to the invention, this object is solved through the subject of the independent claim(s). Advantageous embodiments are subject of the dependent claim(s).
The present invention is based on the general idea of reducing the net weight in an air flap for an air conditioning system of a motor vehicle in regions, with a bending strength remaining the same. The air flap for an air conditioning system of a motor vehicle comprises a bearing section defining a pivot axis of the air flap for mounting the air flap on a housing and at least one flap wing. The at least one flap wing is integrally formed on the bearing section and extends from the pivot axis of the air flap at least in regions radially to the outside and/or in the circumferential direction. According to the invention, the at least one flap wing and/or the bearing section has an outer skin and at least one inner region delimited from the outer skin towards the inside, which merge into one another. The at least one flap wing and/or the bearing section are formed from a plastic, wherein the plastic is exclusively foamed in the inner region.
The air flap can comprise multiple inner regions, which are delimited by the outer skin towards the outside. Both the outer skin and also at least one inner region are produced from the same plastic and merely differ in their density. The outer skin has a density corresponding to the unfoamed plastic and in the at least one inner region the density—also varying in a region—is reduced according to a foaming factor. In this advantageous way the net weight of the air flap can be reduced with no reduction or a minor reduction of the wall thickness and the bending strength of the air flap retained. In particular, the net weight is reducible only on the flap wings without the density and the bending strength of the bearing section being influenced. Furthermore, the air flap is additionally stiffened by the outer skin and the surface quality of the air flap improved. The air flap can, for example, consist of polypropylene, polyamide or polyolefin with a suitable for example mineral addition for foaming the plastic.
Advantageously, a density of the foamed plastic in the at least one inner region can be lower by a foaming factor between 1.1 and 4 than a density of the plastic in the outer skin. The foaming factor between 1.1 and 4 makes possible an increase in volume by 10% to 300% and accordingly a density reduction. Preferably, the foaming factor amounts to approximately 2 and makes possible the volume increase by 100% and the density reduction by 50%. Advantageously, the air flap can comprise at least two inner regions, wherein foaming factors of the foamed plastic in these inner regions deviate from one another. Accordingly, two inner regions can be formed for example in the at least one flap wing which have a density deviating from one another and a net weight deviating from one another.
In a further development of the air flap according to the invention it is advantageously provided that on a bearing side of the bearing section an axially projecting bearing element is integrally formed. The bearing element can be arranged in a bearing opening of the housing and the air flap rotatably mounted about the pivot axis on the housing because of this. Alternatively, an axially extending bearing opening can be formed on a bearing side of the bearing section. In the bearing opening, an axially projecting bearing element of the housing can then be arranged and the air flap be rotatably mounted about the pivot axis on the housing because of this. On the bearing side, the air flap is rotatably mounted passively. For actively mounting the air flap, an axially extending mounting space can be formed on a receiving side of the bearing element section and in the mounting space an output element of the air flap can be non-rotatably fixed on one side. On the other side, the output element can be rotatably arranged in a receiving opening of the housing and the air flap rotatably mounted about the pivot axis on the housing because of this. On the output element, a pivot or tilting drive—for example an actuator—can be arranged which pivots the output element and because of this the air flap that is non-rotably fixed on the output element and because of this opens and closes the air duct.
For the non-rotatable fixing of the output element in the mounting space at least one radial engagement lug can be formed on the output element and at least one radial engagement opening in the mounting space. The engagement lug can then engage in the engagement opening and because of this the output element can be non-rotatably fixed in the mounting space. Alternatively or additionally, at least one axially extending groove or tongue can be formed in the mounting space and on the output element a complementarily formed tongue or groove be formed. The respective tongue and the respective groove can then be in engagement in the circumferential direction to the pivot axis and because of this the output element in the mounting space can be non-rotatably fixed.
Advantageously it can be provided that on the at least one flap wing an interference structure with multiple mouldings and/or with multiple recesses is formed. The multiple mouldings and/or the multiple recesses of the interference structure can be arranged regularly or irregularly on the at least one flap wing. In particular, a noise development on the air flap in a slightly opened state can be reduced in this way without increasing the net weight of the air flap.
In an advantageous further development of the air flap according to the invention it is provided that the at least one flap wing has a flat radial region adjoining the bearing section and a flat deflection region adjoining the radial region, wherein the deflection region adjoins the radial region at a bending angle. In particular, air can be deflected in the air duct with the opened air flap in this way, and because of this a favourable air flow in the air duct achieved. In order to be able to seal the air duct, an axially extending sealing lip can be fixed in an edge region of the at least one flap wing facing away from the bearing section. Here, the sealing lip is fixed preferably in a material-bonded manner by injection moulding and/or is fixed in a form-fitting manner by engaging on the at least one flap wing.
In summary, the air flap according to the invention has a reduced net weight with a high bending strength. Furthermore, additional reinforcement structures such as for example ribs or corrugations are obsolete with the air flap according to the invention so that the undesirable noise development and the complexity of the air flap are reduced.
The invention also relates to a method for producing an air flap for an air conditioning system of a motor vehicle. In the method, a closed cavity is initially formed from at least two mould parts and the formed cavity is filled with a melted plastic charged with a blowing agent. The filled cavity is enlarged by moving the mould parts or mould segments of at least one of the mould parts so that in the enlarged cavity an under pressure is created and a foam formation initiated in the melted plastic. Following a solidification of the plastic, the enlarged cavity is opened for removing the produced air flap. According to the invention, the air flap described above is described by the method. The air flap described above can be produced by the method with a reduced net weight in one production step. Here, the air flap does not have any additional stiffening structures and an undesirable noise development on the air flap can be advantageously prevented.
In the method according to the invention, the mould parts or the individual mould segments of one of the mould parts can be moved in such a manner that the air flap described above is produced with the at least one flap wing and the bearing section. In the method, an outer skin and at least one inner region that is delimited from the outer skin towards the inside is formed in the at least one flap wing and/or in the bearing section, which integrally merge into one another. The outer skin is formed from the plastic and the at least one inner region is formed from the foamed plastic. Both the outer skin and also the at least one inner region are produced from the same plastic and merely differ in their density. Accordingly, the one mould part cannot be moved and the other mould part or one or some of the mould segments of the other mould part can be moved. On the moved mould segments, the outer skin is formed from the plastic that is solidified and not foamed on the mould surfaces of the mould segments and by way of a negative stroke of the mould segments, the inner regions that are delimited from the outer skin moulded from the foamed plastic. On the unmoved mould segments, the plastic is not foamed and exclusively the outer skin formed.
For example with the air flap having two flap wings, the mould segments forming the two flap wings can be moved and in the two flap wings the inner regions delimited by the outer skin formed from the foamed plastic because of this. The mould segment forming the bearing section of the air flap cannot be moved so that the bearing section is formed from the unfoamed plastic. Alternatively, the mould segment forming the bearing section of the air flap can be moved with a smaller negative stroke than the mould segments forming the two flap wings so that the inner region in the bearing section is foamed to a higher density than in the inner regions of the flap wings. Alternatively or additionally, the mould segments forming the two flap wings can be moved with a deviating negative stroke.
Advantageously it can be provided that the plastic in the at least one inner region of the at least one flap wing and/or of the bearing section is chemically or mechanically foamed to a density which is lower by a foaming factor between 1.1 and 4 than a density of the plastic in the outer skin. The foaming factor between 1.1 and 4 makes possible a volume increase by 10% to 300% and accordingly a density reduction. Preferably, the foaming factor is approximately 2 and makes possible the volume increase in the inner region by 100% and a corresponding density reduction. Advantageously, the plastic in the inner regions can be chemically or mechanically foamed to a deviating density in that for example the mould segments forming the two inner regions are moved with a deviating negative stroke. In order to configure the bearing section of the air flap so as to be stable, the plastic in the inner region of the bearing section can be foamed by a more deviating foaming factor than the plastic in the at least one inner region of the at least one flap wing. Alternatively, the plastic in the bearing section cannot be foamed.
Advantageously, the mould parts and/or the individual mould segments can be temperature-controlled to a deviating process temperature. A foaming factor of the plastic in the at least one inner region of the at least one flap wing and/or of the bearing section can be adapted by a deviating process temperature. In particular, the thickness of the outer skin defining the inner regions can be adapted in this way. Accordingly, the mould segment for example forming the bearing section of the air flap or a region of the mould part forming the bearing section of the air flap can be cooled so that a foaming in the bearing section is partly or completely prevented even during a negative stroke of the neighbouring mould segment or of the neighbouring mould part. In this way, the bearing section can have an same bending strength and an same quality as with a compactly injection moulded air flap. Furthermore, the inner regions can be formed with a deviating density within the air flap even with an same negative stroke of the mould parts and/or of the mould segments of the mould parts.
In order to be able to seal the air duct, the axially extending sealing lip can be injection moulded on in a material-bonded manner and/or can be engaged in a form-fitting manner following the removal of the air flap from the cavity in the edge region of the at least one flap wing facing away from the bearing section. The air flap can be produced for example from polypropylene, polyamide or polyolefin with a suitable for example mineral additive for promoting the foaming of the plastic and the sealing lip for example from a thermoplastic elastomer.
In summary, the air flap can be produced with the method according to the invention with a reduced net weight and a high bending strength in one process step in a simplified and cost-saving manner. In the produced air flap, additional reinforcing structures such as for example ribs or corrugations can be omitted and an undesirable noise development on the air flap advantageously prevented because of this. Corrugations and other contours for suppressing the noise development in the case of an only slightly opened air flap however can be realised without problems.
Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description by way of the drawings.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description, wherein same reference numbers relate to same or similar or functionally same components.
It shows, in each case schematically
The air flaps 1 in
In summary, the air flap 1 according to the invention has a reduced net weight with a high bending strength. Furthermore, additional reinforcement structures such as for example ribs or corrugations are not required with the air flap 1 according to the invention so that the undesirable noise development and the complexity of the air flap 1 are reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018202169.4 | Feb 2018 | DE | national |
