Method for producing an injection molded part, injection mold and fan impeller

Abstract

A method produces an injection molded part. A plastic material is injected into a cavity for forming the injection molded part. The plastic material in a flow line region of the cavity, where the plastic material from two directions coincides during an injection molding process, is at least partially removed from the cavity via at least two overflow points and, in so doing, is locally swirled or mixed between the overflow points.

Claims

1. A method for producing an injection molded part, which comprises the steps of: injecting a plastic material into a cavity for forming the injection molded part, wherein the plastic material in a flow line region of the cavity, where the plastic material converges from two directions during an injection molding process, is at least partially removed from the cavity via at least two overflow points that are disposed tangentially and axially offset from one another and, during the injection molding process, is locally swirled or mixed between the at least two overflow points.

2. The method according to claim 1, wherein the at least two overflow points are disposed offset from the flow line region along one of the two directions.

3. The method according to claim 1, wherein the at least two overflow points open perpendicularly into the cavity.

4. The method according to claim 1, wherein the injection molded part is a fan impeller for a radiator fan.

5. The method according to claim 4, wherein the cavity producing the injection molded part as the fan impeller having a central hub cup with a plurality of radially oriented blades and an outer ring connecting the radially oriented blades to one another at blade tips.

6. The method according to claim 5, wherein the flow line region is disposed at the outer ring.

7. The method according to claim 5, wherein the flow line region at the outer ring is disposed between two adjacent ones of the radially oriented blades.

8. The method according to claim 5, wherein the at least two overflow points are positioned radially on an inside of the outer ring.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a diagrammatic, perspective view of a fan impeller according to the invention;

(2) FIG. 2 is a sectional view of a flow line region of the fan impeller with two overflow points of an injection mold;

(3) FIG. 3 is a sectional view of an outer ring of the fan impeller with two tunnels as overflow points;

(4) FIG. 4 is a sectional view of the outer ring and an overflow cavity of the injection mold;

(5) FIG. 5 is a schematic side view of the outer ring of the fan impeller; and

(6) FIG. 6 is a sectional plan view of the outer ring.

DETAILED DESCRIPTION OF THE INVENTION

(7) In all the figures, mutually corresponding parts and dimensions are always provided with the same reference signs.

(8) Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a fan impeller 2 of a radiator fan (not illustrated specifically) or radiator fan module of a motor vehicle in perspective.

(9) The fan impeller 2 has a central hub cup 4, on an outside of which a number of fan blades (fan vanes) 6, which are oriented in a radial direction R, are integrally formed. In this exemplary embodiment, the fan impeller 2 has seven blades 6. In FIG. 1, purely by way of example, the blades 6 are provided with reference signs.

(10) Here and in the following, axial or an axial direction A is understood to mean, in particular, a direction parallel (coaxial) to the axis of rotation of the fan impeller 2, that is to say perpendicular to the end faces of the hub cup 4. In corresponding fashion, here and in the following, radial or a radial direction R is understood to mean, in particular, a direction oriented perpendicularly (transversely) to the axis of rotation of the fan impeller 2 along a radius of the fan impeller 2. Here and in the following, tangential or a tangential direction T is understood to mean, in particular, a direction along the circumference of the fan impeller 2 (circumferential direction, azimuthal direction), i.e. a direction perpendicular to the axial direction A and to the radial direction R.

(11) During operation of the radiator fan module, the fan impeller 2 is driven in rotation, by an electric motor coupled in terms of drive to the hub cup 4, in the direction of rotation symbolized by the arrow D in FIG. 1. Here, the direction of rotation D is parallel to the tangential or circumferential direction T of the fan impeller 2. In this direction of rotation D or in the tangential direction T, the blades 6 are configured so as to be concave at their leading edges 6a and substantially convex and preferably wavy at their trailing edges 6b.

(12) The blades 6 are connected to one another or mechanically coupled to one another at their blade tips 6c by means of a circumferential outer ring 8. The outer ring 8 serves, inter alia, to stabilize the blades 6 during the rotary motion of the fan impeller 2. By means of the outer ring 8, the air flow is also guided, and the aerodynamic properties of the fan impeller 2 are improved.

(13) The outer ring 8 has a tangentially extending outer band 8a and a radial lip 8b projecting radially around the outer band 8a. As can be seen, in particular, in FIGS. 3 and 4, the outer ring 8 thus has an approximately L-shaped cross-sectional shape in the section planes shown, wherein the outer band 8a extends as a vertical L-leg and the radial lip 8b extends as a horizontal L-leg in the radial direction over the outer circumference of the outer ring 8 or outer band 8a.

(14) The fan impeller 2 is embodied as a single-part, i.e. one-piece or monolithic, injection molded part. In this case, the fan impeller 2 is produced from a thermoplastic and fiber-reinforced plastic material, which is injected by means of nozzles into a cavity 13 (FIG. 4) of an injection mold (not shown specifically) in the course of the injection molding process.

(15) The injection or gating point of the injection mold or of the cavity 13 is arranged in the middle or centrally in the region of the hub cup 4, for example, from where the pressurized plastic material or plastic melt is distributed in the cavity. The result is that, in the region of the outer ring, in each case two melt flows converge from two directions between two blades. In the cooled or cured state of the plastic material, the converging melt flows form a flow line 10, wherein the region in which the flow line 10 occurs is referred to below as a flow line region 12. As can be seen in FIG. 1, the fan impeller 2 has seven such flow lines 10 or flow line regions 12.

(16) In order to mechanically stabilize and improve the flow line strength, at least two overflow points 14a, 14b are provided for each flow line region 12 of the cavity, at which overflow points the plastic material is partially removed from the cavity 13. The overflow points 14a, 14b are, in particular, embodied as (sprue) tunnels, which open into one or more overflow cavities 16 (FIG. 4).

(17) The overflow points 14a, 14b, which are also referred to below as tunnels, are arranged off-center and offset relative to one another in the flow line region 12, with the result that when the plastic material converges from two (flow) directions S1, S2 in the flow line region 12 during an injection molding process, the plastic material is at least partially guided into the overflow cavity (cavities) 16 via the tunnels 14a, 14b and, as a result, the plastic material or melt flows is/are locally swirled or mixed in the flow line region 12.

(18) As can be seen comparatively clearly in FIGS. 2 and 3, the two tunnels 14a, 14b are arranged tangentially and axially offset relative to one another, with the result that the flow line 10 is positioned between the tunnels 14a, 14b in the tangential direction. The tunnels 14a, 14b open out substantially perpendicularly onto the component surface of the outer ring 8b, as is shown particularly in FIG. 4 for tunnel 14a. The tunnels 14a, 14b are thus spaced apart from an edge or a parting plane of the fan impeller 2 or outer ring 8. In this case, the tunnels 14a, 14b are arranged radially on the inside of the outer band 8b.

(19) As can be seen, in particular, in the illustration of FIG. 2, a flow line 10 is formed in the outer ring 8 in the flow line region 12 owing to the offset arrangement of the tunnels 14a, 14b on the sheet-like inner circumference of the outer band 8b. As a result, a high orientation of the reinforcing fibers of the plastic material, which are illustrated as lines in FIG. 2, is achieved, thereby increasing the strength of the flow line 10 or in the flow line region 12.

(20) A second exemplary embodiment of the invention is shown in FIGS. 5 and 6. In this embodiment, the tunnels 14a, 14b are arranged on a common side of the flow line 10, that is to say offset with respect to the flow line region 12 along one of the directions S1, S2. The relative positioning of the tunnels 14a, 14b with respect to the flow line 10 is explained in greater detail below.

(21) Hereinafter, the axial height of the outer band 8a is denoted by a and the radial width of the radial lip 8b is denoted by b, wherein the height a is preferably longer than the width b. The sum of the height a and the width b is referred to below as length l (l=a+b).

(22) FIG. 6 shows a projected illustration of the outer ring 8. Tunnel 14a is arranged at a position P1 and tunnel 14b is arranged at a position P2, which are arranged offset with respect to the flow direction S1 in the flow line region 12. Position P1 is at a tangential distance r from the flow line 10, while position P2 is at a tangential distance s. Position P1 is at an axial/radial distance u from an (upper) edge of the outer ring 8, while position P2 is at a radial/axial distance v from an opposite (lower) edge of the outer ring.

(23) In a suitable dimensioning, the following relationships apply:

(24) $10\mathrm{mm}r25\mathrm{mm},$$r+10\mathrm{mm}sr+25\mathrm{mm},$$*Iu0.49*I,\mathrm{and}$$*Iv0.49*I.$

(25) This means that the distance r is preferably between 10 mm (millimeters) and 25 mm, where, depending on the distance r, the distance s is between 10 mm+r and 25 mm+r. The distances u and v are preferably dimensioned to be between 10% and 49% of the length l.

(26) The invention is not restricted to the exemplary embodiment described above. On the contrary, other variants of the invention can also be derived therefrom by a person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the exemplary embodiment can also be combined with one another in some other way without departing from the subject matter of the invention.

(27) The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.

LIST OF REFERENCE SIGNS

(28) 2 fan impeller 4 hub cup 6 blade 6a leading edge 6b trailing edge 6c blade tip 8 outer ring 8a outer band 8b radial lip 10 flow line 12 flow line region 13 cavity 14a, 14b overflow point/tunnel 16 overflow cavity A axial direction R radial direction T tangential direction D direction of rotation S1, S2 flow direction a height b width l length P1, P2 position r, s, u, v distance