Casting mould for casting a vehicle wheel and method for casting a vehicle wheel

Description

[0001] The invention relates to a mold for casting a vehicle wheel, comprising a mold cavity and a sprue area adjacent to the mold cavity, through which molten material can be supplied to the mold cavity to form the vehicle wheel. Furthermore, the invention relates to a method for casting a vehicle wheel, wherein molten material is supplied to a mold cavity via a sprue area adjacent to the mold cavity to form the vehicle wheel.

[0002] A generic casting mold and a generic process are known from WO 2019 / 048675 A1.

[0003] The process described therein and the mold used have proven to be very well suited to the requirements of modern vehicle wheel manufacturing, particularly with regard to lightweight construction, aerodynamics, and crash performance. However, the known solution is not optimal with respect to the microstructure of the resulting vehicle wheel and its consequent strength.

[0004] Similar casting molds and casting processes are also described in US 2012 / 175905 A1, DE 10 2019 106 378 A1 or DE 295 21 266 U1.

[0005] From DE 12 90 672 A a casting mold for die casting machines consisting of an ejection mold half and a cover mold half is known, in which one mold half is divided into a core-like middle piece and a mold plate.

[0006] A similar state of the art is also described in DE 13 02 161 A.

[0007] In the prior art, gating systems are known that are typically relatively flat to minimize post-processing requirements. However, this design is disadvantageous for the flow of the molten material, as it can lead to very high flow velocities and a resulting cracking of the casting front. This can result in poor or defective components, particularly in vehicle wheels. Especially in die casting processes and the molds used, a gating system with a very small and flat cross-section is most commonly employed.

[0008] It is therefore an object of the present invention to provide a mold and a method for casting a vehicle wheel which is able to design the mold filling, the targeted solidification within the mold cavity in conjunction with the solidification time in such a way that the microstructure and strength properties of the vehicle wheel are improved.

[0009] According to the invention, this problem is solved by the features mentioned in claim 1.

[0010] The inventive ratio between the smallest cross-sectional area of ​​the gate area immediately before entering the mold cavity and the volume of the total mold cavity—i.e., the volume of the actual mold cavity plus the volume of the gate and overflow—ensures that the molten material enters the mold as uniformly as possible and flows through it smoothly. This uniform flow results in an extremely low-turbulence, quasi-laminar, or calmed, casting process, in which the breaking up of the casting front and the associated spattering or tearing of the casting front are prevented as far as possible. At the same time, at a suitable velocity, this makes it possible to achieve very rapid mold filling. The molten material thus experiences no acceleration, which also prevents an unnecessary increase in the casting pressure that could otherwise lead to casting defects.This method also ensures a better supply of material, which is necessary to completely fill the mold.

[0011] The ratio between the smallest cross-sectional area of ​​the sprue area immediately before entering the mold cavity and the volume of the total mold cavity can also be referred to as the modulus, as described in more detail below.

[0012] The very short mold filling times of, for example, 40 to 70 ms, preferably 50 to 60 ms, with a maximum flow rate of the molten material of up to 70 m / s, ensure a fine microstructure and high strength of the vehicle wheel produced with the mold according to the invention.

[0013] In a highly advantageous embodiment of the invention, the ratio or module can be at most 1.4 mm² / cm³. By limiting the ratio between the smallest cross-sectional area of ​​the gate area and the volume of the mold cavity, i.e., the module, incorrect dimensioning of the gate system is avoided, thus ensuring the economic viability of the solution according to the invention.

[0014] To avoid undesirable acceleration of the molten material within the gate area, it may also be provided that the cross-sectional area of ​​the gate area is constant or increasing when viewed in the main flow direction of the molten material.

[0015] In a further advantageous embodiment of the invention, the cross-sectional area of ​​the mold cavity, starting from the gate area, can be configured to be constant or increasing in the main flow direction of the molten material up to a depth of at least 60% of the total depth of the mold cavity. This ensures a constant velocity of the molten material in the majority of the mold cavity, whereas acceleration of the molten material is permitted in the area of ​​the mold cavity furthest from the gate area. Such acceleration of the molten material is particularly advantageous in the manufacture of vehicle wheels, since the area furthest from the gate area often has comparatively narrow cross-sections, in which there is a risk of premature, unwanted solidification.The acceleration of the molten material permitted in these areas, and thus its higher speed, prevents such unwanted solidification processes and results in a homogeneous solidification of the entire vehicle wheel.

[0016] A method according to the invention is specified in claim 5.

[0017] This process allows for the production of a vehicle wheel with the advantages mentioned above in relation to the casting mold.

[0018] In a highly advantageous embodiment of the inventive method, the ratio or module can be at most 1.4 mm² / cm³. As mentioned above, limiting the ratio between the volume of the mold cavity and the smallest cross-sectional area of ​​the gate area, i.e., the module, prevents incorrect dimensioning of the gate system and thus ensures the economic viability of the inventive solution.

[0019] In a highly advantageous further development of the inventive method, if a light metal material is used as the molten material, not only is the method very well suited for the production of vehicle wheels, but optimal adaptation to the further conditions of the inventive method is also achieved.

[0020] To achieve rapid filling of the mold cavity and uniform solidification of the molten material, it may also be provided that the molten material is introduced into the mold cavity at a casting piston speed of more than 5 m / s.

[0021] Furthermore, it can be provided that the molten material flows through the mold cavity at a speed of more than 15 m / s. Such a high flow velocity of the molten material within the mold cavity allows for the creation of very thin cross-sections, as the filling of the mold is ensured despite its significantly lower temperature.

[0022] A vehicle wheel can have geometries that are not achievable with known methods. For example, significantly thinner or more delicate structures can be produced, which, for instance, allows for a much larger number of spokes than in conventional vehicle wheels. An embodiment of the invention is illustrated in principle below with reference to the drawing.

[0023] It shows: Fig. 1 a top view of a casting mold according to the invention for casting a vehicle wheel; Fig. 2 a section along line II-II from Fig. 1 ; Fig. 3 a section along line III-III from Fig. 1 ; Fig. 4 a section along line IV-IV from Fig. 2 ; Fig. 5 a section along line VV from Fig. 2 ; and Fig. 6 a section along line VI-VI from Fig. 2 .

[0024] Fig. 1 Figure 1 shows a mold 1 for casting a vehicle wheel. The vehicle wheel is produced by introducing molten material, preferably a light metal material and in particular an aluminum casting alloy, into a mold cavity 2 of the mold 1 and subsequent solidification of the molten material. Since the material in the Figures 2 to 6 In the depicted states, the molten material forming the vehicle wheel is already located within the mold cavity 2 of the casting mold 1. Figures 2 to 6simultaneously to be seen as cross-sections through the vehicle wheel. Of course, this is in the Figures 2 to 6 The depicted vehicle wheel should be regarded as only one of many possible embodiments.

[0025] The mold 1 also has a sprue area 3 adjacent to the mold cavity 2, through which the molten material is supplied to the mold cavity 2 to form the vehicle wheel.

[0026] The ratio between the smallest cross-sectional area of ​​the gate area 3 and the volume of the mold cavity 2 is at least 0.6 mm² / cm³. Preferably, this ratio is at most 1.4 mm² / cm³. In principle, the ratio between the smallest cross-sectional area of ​​the gate area 3 and the volume of the mold cavity 2 can also be at least 0.7 mm² / cm³ and at most 1.5 mm² / cm³, but the aforementioned values ​​of at least 0.6 mm² / cm³ and at most 1.4 mm² / cm³ have proven to be better suited in tests with regard to a uniform flow into and through the mold.

[0027] The aforementioned ratio between the smallest cross-sectional area of ​​the gate area 3 and the volume of the mold cavity 2 can be understood as a module. Within the scope of the invention, the module links an area measure [mm²], namely the smallest cross-sectional area of ​​the gate area 3, with a volume measure [cm³], namely the volume of the mold cavity 2. The module has the dimension of an inverse length. Furthermore, the unit [mm² / cm³] is equivalent to the unit [1 / m].

[0028] If the mold cavity 2 has a volume of 7000 cm³, for example, the modulus can be selected from an interval between 0.6 mm² / cm³ and 1.4 mm² / cm³, for example with a value of 0.8 mm² / cm³, or the modulus lies within this range. Thus, in the present example, for the design of the smallest cross-sectional area of ​​the gate area 3, starting from a volume of 7000 cm³, multiplying by the modulus of 0.8 mm² / cm³ results in a target cross-sectional area of ​​5600 mm². These values, of course, represent only one exemplary embodiment.

[0029] Preferably, the molten material is introduced into the mold cavity 2 at a casting piston speed of more than 5 m / s. The direction of the force with which a casting piston (not shown) forces the molten material over the sprue area 3 into the mold cavity 2 of the mold 1 is in Fig. 2This is indicated by the arrow "F". As a result, the molten material flows through the mold cavity 2 at a velocity of more than 15 m / s. However, to prevent cracking of the casting front, it is preferable if the velocity of the molten material in those cross-sections of the mold cavity 2 that are critical for achieving a satisfactory component does not exceed 70 m / s. In other words, in certain cross-sections that are not critical for the quality of the vehicle wheel being produced, the flow velocity of the molten material can certainly exceed the aforementioned 70 m / s.

[0030] In Fig. 2The pouring direction or the main flow direction of the molten material is represented by several arrows, some of which are labeled "x". The smallest cross-sectional area of ​​the gate area 3 is measured in a plane perpendicular to the main flow direction x of the molten material. This smallest cross-sectional area of ​​the gate area 3 is in Fig. 3 represented by the hatching.

[0031] Viewed in the main flow direction x of the molten material, the cross-sectional area of ​​the gate region 3 is preferably constant or increasing in size. One embodiment of the gate region 3 can therefore consist in such a way that, measured perpendicular to the main flow direction x of the molten material, all cross-sectional planes of the gate region 3 are approximately the same size.

[0032] Starting from the gate area 3, the cross-sectional area of ​​the mold cavity 2, viewed in the main flow direction x of the molten material, is preferably constant or increasing in size up to a depth of at least 60% of the total depth of the mold cavity 2. These constant or increasing cross-sections of the mold cavity 2 can also be present up to a depth of 80% of the total depth of the mold cavity 2. Only in the last 20 to 40% of the area of ​​the mold cavity 2 furthest from the gate area 3 can the cross-sectional area of ​​the mold cavity 2 decrease.

[0033] For all of the aforementioned conditions, the mold cavity 2 and thus the vehicle wheel produced with the casting mold 1 can be adapted to specific requirements or circumstances.

Claims

1. Casting mould (1) for casting a vehicle wheel, having a mould cavity (2) and a sprue region (3) adjacent to the mould cavity (2), via which molten material can be fed to the mould cavity (2) to form the vehicle wheel, characterised in that a ratio or modulus between the smallest cross-sectional area of the sprue region (3) and the volume of the mould cavity (2) is at least 0.6 mm2 / cm3.

2. Casting mould according to claim 1, characterised in that the ratio or modulus is at most 1.4 mm2 / cm3.

3. Casting mould according to claim 1 or 2, characterised in that the cross-sectional area of the sprue region (3) is designed to remain constant or to increase in the main flow direction (x) of the molten material.

4. Casting mould according to claim 1, 2 or 3, characterised in that the cross-sectional area of the mould cavity (2), starting from the sprue region (3), is designed to remain constant or to increase in the main flow direction (x) of the molten material up to a depth of at least 60% of the total depth of the mould cavity (2).

5. Method for casting a vehicle wheel, wherein molten material for forming the vehicle wheel is fed into a mould cavity (2) via a sprue region (3) adjacent to the mould cavity (2), characterised in that a ratio or modulus between the smallest cross-sectional area of the sprue region (3) and the volume of the mould cavity (2) is at least 0.6 mm2 / cm3.

6. Method according to claim 5, characterised in that the ratio or modulus is at most 1.4 mm2 / cm3.

7. Method according to claim 5 or 6, characterised in that a light metal material is used as the molten material.

8. Method according to claim 5, 6 or 7, characterised in that the molten material is introduced into the mould cavity (2) at a casting piston speed of more than 5 m / s.

9. Method according to one of claims 5 to 8, characterised in that the molten material flows through the mould cavity (2) at a speed of more than 15 m / s.