Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
2001-04-18
2003-11-18
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S259000, C264S275000
Reexamination Certificate
active
06649111
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a method for producing a housing for a throttle valve connection piece, which housing has a throttle orifice for a throttle valve, the housing being produced from plastic by the injection molding method, and, during the injection molding method, plastic being partially injected around a metal cylinder which, at least in the region of the throttle valve, forms the throttle orifice. The invention relates, furthermore, to a throttle valve connection piece with a housing which has a throttle orifice for a throttle valve, the housing produced from plastic by the injection molding method having a metal cylinder which is partially surrounded by plastic and, at least in the region of the throttle valve, forms the throttle orifice.
Throttle valve connection pieces are conventionally used for controlling the fresh-gas quantity of a motor vehicle. Throttle valve connection pieces comprise a housing with a throttle orifice and a throttle member arranged in the throttle orifice. The throttle member assumes a specific position in the throttle orifice for the passage of a specific fresh-gas quantity. For this purpose, the throttle member can be activated mechanically or electronically.
Housings of throttle valve connection pieces are usually produced from plastic or from metal. Those housings of throttle valve connection pieces which are manufactured from metal, for example aluminum, may have particularly low tolerances. Low tolerances are necessary for a throttle valve connection piece, in the region of the throttle valve, particularly when an especially accurate opening and closing of the throttle valve is required. In the closing region of the throttle valve, these requirements are also referred to as leakage-air requirements. However, metal housings of throttle valve connection pieces have the disadvantage that, after the housing has been produced, for example by the diecasting method, complicated remachining of the housing is necessary. It is often necessary, for example, to carry out careful remachining of the housing extensions provided for bearings of the throttle valve shaft, so that the bearings of the throttle valve shaft can be fitted into the housing without tilting.
Those housings of throttle valve connection pieces which are manufactured from plastic have a lower weight than those housings of throttle valve connection pieces which are manufactured essentially from metal, in particular aluminum. Furthermore, plastic, as material, can also be adapted in an especially simple way to a wide variety of geometric configurations of the housing. Moreover, in the case of plastic housings produced by the injection molding method, inserts, for example bearings for mounting the throttle valve shaft, can be injected into the housing.
However, those housings of throttle valve connection pieces which are produced from plastic by the injection molding method have the disadvantage that they shrink during and after the injection molding method. Moreover, housings of this type may experience warping after removal from the mold, that is to say may be deformed when they are taken out of the injection mold. Also, those housings of throttle valve connection pieces which are manufactured from plastic are not especially dimensionally stable over a particularly wide temperature range. On the one hand, in a motor vehicle, housings of throttle valve connection pieces are exposed to outside temperatures down to −40° C. On the other hand, when the throttle valve connection piece is in operation, the temperature of the throttle valve connection piece may rise above 100° C. These wide temperature fluctuations may lead to adverse deformations of the plastic in the pivoting region of the throttle valve. These deformations, in turn, may lead to the particularly high accuracy of fit of the throttle valve in the housing decreasing in the course of time. In this context, particularly high accuracy of fit means, for example, accuracies of fit of the housing of the throttle valve connection piece in the range of 0 to 30 &mgr;m, in so far as the housing is subject, for example, to the ISO tolerance with respect to the dimension for the throttle orifice. As a result of changes in shape of the throttle orifice, the particularly stringent leakage-air requirements, especially when the throttle valve is in the idling position, can no longer be satisfied. This entails an increased fuel consumption and a diminished exhaust-gas quality. For a constant fuel consumption and a constant exhaust-gas quality, therefore, it is necessary to have a dimensional stability of the housing of the throttle valve connection piece, in particular of the throttle orifice, over many years.
DE 43 34 180 A1 discloses a housing manufactured from plastic for a throttle valve connection piece, an annular insertion part being integrated into said housing in the pivoting region of the throttle valve. Although the insertion part, around which plastic is injected completely, improves dimensional stability of the housing of the throttle valve connection piece, it cannot reliably prevent changes in shape in the pivoting region of the throttle valve due to the high compressive loads during the injection of the plastic. Interaction of the medium passing through the throttle valve connection piece with the plastic leads, as before, to changes in shape of the plastic and therefore of the throttle orifice, even though these changes are no longer as drastic as would be the case without the annular insertion part.
SUMMARY OF THE INVENTION
The object on which the invention is based, therefore, is to specify a method for producing a housing for a throttle valve connection piece of the abovementioned type, in which the dimensional stability of the metal cylinder during the injection molding method and the dimensional stability of the housing after removal from the mold are ensured in an especially reliable way. Moreover, a throttle valve connection piece is to be specified, the housing of which has especially high dimensional stability even in the case of especially high temperature fluctuations.
With regard to the method, this object is achieved, according to the invention, in that, before the injection molding method, an expanding mandrel having a diameter which can be enlarged is expanded against the inner face of the metal cylinder. During the injection molding method the inner face if the metal is supported at least partially by the expanding mandrel, and, after the injection molding method, the outer circumference of the expanding mandrel is reduced in order to remove the expanding mandrel from the interior of the metal cylinder.
The invention proceeds from the notion that dimensional stability of the housing after removal from the mold is ensured particularly reliably when the housing has dimensionally stable elements in the region of the throttle orifice during the injection molding operation. A particularly simple design of a dimensionally stable element, at least for a part region of the throttle orifice, is a metal cylinder which is hollow on the inside. It must be remembered, in this case, however, that, during the injection molding method, even a metal cylinder must be protected against deformations which may occur due to the pressure built up by the plastic during the injection molding method. The problem arises here, however, that supporting bodies which support the metal cylinder during the injection molding method often leave behind scores or roundnesses in the metal cylinder during removal from the mold. Scores or roundnesses normally occur when the supporting body is moved out of the metal cylinder, particularly when the supporting body is released from the inner casing of the metal cylinder. The result of these scores or roundnesses may be that the housing of the throttle valve connection piece does not have, for example, a tolerance which is predetermined for the throttle orifice. These scores or roundnesses can be removed by means of a subsequent mechanical machining of the h
Backes Carlos
Haede Michael
Hannewald Thomas
Mörbe Rüdiger
Oppermann Rolf
Farber Martin A.
Mannesmann VDO AG
Ortiz Angela
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