Note: Descriptions are shown in the official language in which they were submitted.
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Procedure for manufacturing a frame-like structural component
The invention relates to a procedure for manufacturing a frame-like structural
component with an opening,
especially a recliner back structure or a seat frame structure of a vehicle,
while using a light metal alloy by
means of casting.
A procedure of this type is known from DE 10 2004 062 946 Al. It serves for
manufacture of a recliner
back frame of a vehicle seat while using a magnesium alloy. With this, melted
metal is cast into a casting
hopper by means of shape casting, which [hopper] in essence is placed in the
middle of a form for
manufacturing the recliner frame so that the metal expands into the form in
various directions. The molten
metal flows at a rate between 4.5 m per second and 5.5 m per second at a de
facto pressure of 500 bar to
7009 bar into the form.
What is a drawback with this known procedure is that after cooling of the
melt, fins form through the central
attachment of the casting hopper (gate) between it and the actual recliner
frame, and these fins are to be
removed as waste parts. In addition to this, due to the waste fins, at various
locations on the cast recliner
frame, it must be re-worked. An additional disadvantage is that with this
casting process, unintentionally,
areas of the recliner frame cannot be optimized in certain sections as regards
mechanical capability to bear
loadings. This optimization is significant, especially as regards mechanical
loading of the recliner frame in
the event of a crash.
In US 6,513,878 B1, a frame-like structural component is described with an
opening, specifically a recliner
structure of a vehicle seat. This recliner structure is manufactured by
casting, whereby a thixo-melting
procedure is used to spray in a melt
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from a semi-melted alloy with a low specific weight.
EP 1 186 469 Al describes a head rest for a vehicle seat, whereby parts of the
metallic
structure are produced by a thixo-molding process, using a magnesium or
aluminum
alloy.
From WO 97/04689, manufacture of a recliner structure and a seat frame
structure of a
vehicle seat by casting is known, whereby the metal body of the structure is
produced in
a single pass by die casting.
The task of the invention is to take a further step in the procedure mentioned
initially, so
that structural components can be produced that in any case after casting need
no
significant re-working, and in which, in defined areas of the frame, enhanced
mechanical characteristics can be featured.
The problem is solved by the present invention, which in one broad aspect
provides a
procedure for manufacturing a frame-like structural component with an opening,
using a
light metal alloy by means of casting, characterized by the following
features:
a. feeding of molten metal of said light metal alloy to at least two
heated melt
feed-in guides, whose melt outlets empty directly into a channel of a casting
form, said channel serving to admit the melt for the structural component,
said melt being fed via the melt feed-in guides into those areas of the
channel of the casting form that correspond to the areas of the finished
structural component, in which the finished structural component is
subjected to higher mechanical loading, cold-flow areas of the molten metal
being placed in defined areas of the structural component that are subject to
lower mechanical loads in the finished structural component;
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b. feeding of the molten metal from the melt feed-in guides into the
channel of
the casting form, whereby molten streams flow in opposite directions in the
channel.
In a second broad aspect, the present invention provides a procedure for
manufacturing
structural component comprising a recliner back structure or a seat frame
structure of a
vehicle, using a light metal alloy by means of casting, characterized by the
following
features:
a. feeding of molten metal of said light metal alloy to at least two heated
melt
feed-in guides, whose melt outlets empty directly into a channel of a casting
form, said channel serving to admit the melt for the structural component,
said melt being fed via the melt feed-in guides into those areas of the
channel of the casting form that correspond to the areas of the finished
structural component, in which the finished structural component is
subjected to higher mechanical loading, cold flow areas of the molten metal
being placed in defined areas of the structural component that are subject to
lower mechanical loads in the finished structural component;
b. feeding of the molten metal from the melt feed-in guides into the
channel of
the casting form, whereby molten streams flow in opposite directions in the
channel.
With the invention-specific procedure, the particular temperature control is
essential. Up
to its entry into the channel of the casting form, the melt is heated, so it
does not harden
in this area. Only the frame-like
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structural component hardens, with waste material not present and re-working
of the structural
component able to be reduced to a minimum.
Due to the two heated melt feed-in guides, hot melt gets into the area of the
channel of the casting form
next to the melt feed-in guides, and the melt slowly cools as it passes
through the channel. Due to the
frame-like configuration of the structural component and the placement of at
least two melt feed-in
guides, the melt can issue via the melt feed-in guides into those areas of the
channel of the casting
form that correspond to the areas of the finished structural component in
which the finished structural
component is subjected to increased mechanical loading. Preferably these are
the lateral frame parts
of the frame-like structural component, especially, with a rediner back
structure, the lateral frame parts
that are placed adjacent to support receptacles of the recliner back structure
for pivoting
accommodation of a seat frame structure.
Through the placement of the melt feed-in guides relative to the channel of
the casting form, and the
hot melt sites feeding into the channel as a result of this, the mechanical
characteristics of the end
product ¨ the frame-like structural component ¨ can be deliberately increased
at the desired locations,
in that the melt feed-in guides produce the corresponding areas that
accommodate great forces during
a crash. Also, cold-flow locations can be placed with this procedure in
defined areas. By this means,
controlled breakdowns can be evoked. With this procedure, the wall thickness
of the frame-like
structural component can be reduced in the direction distant from the gate, to
further lower the weight
of the frame-like structural component. The prerequisite for this is that just
these areas accommodate
light loadings. One such lightly loaded area of a recliner structure is found,
for example, in the upper
horizontal
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section of the recliner structure, in the area of which a head rest is
supported in the frame-like
structural component.
The frame-like structural component in particular is a closed frame that thus
surrounds an opening in
the structural component. However, it is also conceivable for the procedure to
be used with a frame-like
structural component that forms only an opening between two lateral sections
of the structural
component and an area that connects these two lateral sections of the
structural component.
What is common to all the frame-like structural components with an opening, is
that after the molten
metal is fed from the melt feed-in guides into the channel of the casting
form, the molten streams flow
in opposition in the channel. These molten streams which flow at each other,
unite, whereby in the area
of uniting the melt possesses a lower temperature than in the area of the melt
feed-in guides.
Consequently, the uniting areas are especially suited to evoke a controlled
breakdown there owing to
the lower mechanical characteristics.
In a frame-like structural component with an opening, in which it [the
opening] is completely surrounded
by the structural component, the structural component is manufactured in such
a way that the melt is
fed to an annular channel of the casting form via the melt feed-in guides.
The melt feed-in guides can be variously configured. It is viewed as being
especially advantageous if
the particular melt feed-in guide has a hot-channel nozzle, which is also
designated as a hot runner.
Via this hot-channel nozzle, in a particularly effective manner and way, the
melt can be specifically
heated up to the entry into the channel of the casting
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form. By this means is ensured a particularly good temperature control to the
channel and in the
channel. The controllable nozzle temperature in the area of the nozzle outlet
is thus directly at the
entrance of the frame-like structural component, as seen from the viewpoint of
the frame-like structural
component cooled after the casting. But the very real possibility exists to
configure the melt feed-in
guides as heated gates of the casting form.
If especially high requirements are to be set for the quality of the frame-
like structural component as
regards increased mechanical characteristics at various locations, it is
recommended to provide a
multiplicity of melt feed-in guides, and thus a multiplicity of places at
which a melt enters at a high
temperature into the channel of the casting form. In this case, four melt feed-
in guides are viewed as
appropriate.
In particular, the use of hot-channel nozzles in connection with a thixo-
molding or thixo-casting process
makes it possible to manufacture frame-like structural components of
particularly high quality. These
semi-solid processes, in which the alloy to be processed is heated to a
transitional temperature
between solid and liquid, and thus is in a thixotropic condition, ensures
through lessened viscosity of
the material while shear forces are exerted, that the melt can discharge
especially favorably, emerging
from the hot-channel nozzles into diverging areas of the channel of the
casting form, until the opposite-
flowing forward-moving melt streams make contact.
As an alternative, casting of the structural component by means of die casting
is offered, whereby the
casting is done especially by means of warm-chamber die casting or cold-
chamber die casting. In any
case, additionally it is possible also to combine with vacuum die casting.
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Further advantages and features of the invention are gleaned from the
subordinate claims as well as
the following description of an embodiment example of the invention, without
being limited to it. Figure
1 shows a basic depiction of an arrangement to elucidate the invention-
specific procedure.
What is illustrated in figure 1 is a device 1 for feeding the melt from a
magnesium alloy to the channel
of a casting form, whereby this casting form is not illustrated, but instead
the frame-like structural
component 2, which is produced during casting, and thus the insertion of the
melt into an annular
channel of the casting form.
The frame-like structural component 2 is a recliner back structure of a seat,
especially the front seat of
a passenger automobile, where the recliner structure is formed by lateral
frame pieces 3, an upper
frame piece 4 that joins them, and a lower frame piece 5 that joins the frame
pieces 3. Frame pieces 4
and 5 are placed to be essentially parallel, with upper frame piece 4 able to
have receptacles 6 for
insertion of a head rest. Frame pieces 3 are situated so as to diverge from
frame piece 4, so that the
structural component 2 is a trapezoid, frame piece 4 at the top is only
slightly shorter than frame piece
5. An opening 7 is formed between the two frame pieces 3 and frame piece 4 and
5. When the frame-
like structural component 2 is completed, this [opening] serves to accommodate
a suspension,
especially a recliner suspension. In case that structural component 2 forms a
seat frame structure, this
would serve as the receptacle for a bottom suspension.
The apparatus 1 for feeding the melt in has a feed tube 9 with a melt inlet 8.
The feed tube 9 is
connected with two branching tubes 10, so that the melt flowing through feed
tube 9 is divided in equal
parts to the two branching tubes 10. From the two branching tubes 10, the melt
gets into the hot
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channel nozzles 11, wherewith the melt flowing through the particular
branching tube 10 is heated in
the area of the hot channel nozzle lithe follows it to a controlled exit
temperature, or is kept roughly at
it. The outlet area of the melt from the particular hot channel nozzle ills
designated by the reference
number 12. The outlet area is located in those areas of the annular channel of
the casting form, which,
following the casting process, correspond to structural component 2 formed in
the casting form in the
area of frame piece 3, and in fact spaced closer to frame piece 5 than to
frame piece 4. From the
outlet area 12 of the particular hot-channel nozzle 11, the melt is forced
according to the double arrow
A in the direction of frame piece 4 and in the direction of frame piece 5. The
partial melt streams
emerging from the two hot-channel melts 11 meet each other, at a lower
temperature than the exit
temperature of the melts in the outlet areas 12 of hot-channel nozzles 11, in
the area of the axis of
symmetry of structural component 2 between the two frame pieces 3, thus in the
area of the
receptacles 6 for the head rests between these two receptacles 6, at half the
length of frame piece 5. In
the casting process, which preferably is done by means of the thixo-molding
procedure, thus the areas
in which the melt enters into the channel via the hot-channel nozzles 11, have
the best mechanical
characteristics, especially the highest mechanical strength, while the areas
located downstream of the
melt feed-in, especially those in the area of the axis of symmetry of
structural component 2, possess
less strength. Through the arrangement of the hot-channel nozzles 11, where
also more than two hot-
channel nozzles can be used, mechanical characteristics can be deliberately
increased in locations
where the cast frame-like structural component faces the hot-channel nozzles,
such as in areas that
accommodate larger forces in a crash. In the cold-flow locations in the area
of the axis of symmetry, in
contrast, a controlled breakdown can be evoked. With this procedure, the wall
thickness of structural
component 2 can be lessened in the direction distal to the gate,
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to lower the weight of the component. The prerequisite is that these areas
bear light loads.
