Metal working – Method of mechanical manufacture – Electrical device making
Patent
1996-09-11
1997-11-18
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
25112921, H01F 4102
Patent
active
056874685
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is based on a process for manufacturing a magnetic circuit for a valve, specifically for an injection valve for fuel injection systems of internal combustion engines electromagnetically actuatable fuel injection valve wherein a connecting ring is made of a non-magnetic material having a high specific electric resistance, firmly and tightly connected with an internal field and a valve jacket of the fuel injection valve. Thus it is achieved that no fuel can reach a magnetic coil that surrounds the internal field which in turn is surrounded by the valve jacket between the internal field/valve jacket and the connection ring. Since the connecting ring is made of a non-magnetic material, the influence of the connecting ring on the magnetic field is very small; rather, it prevents a magnetic short-circuit between the internal field and the valve jacket, preventing additional eddy-current losses. Fitting the connecting ring, however, is a relatively cost-intensive process. For example, in order to create firm and tight connections, an additional internal ring and an external soldered ring are required for manufacturing the magnet from the internal field, valve jacket, and connecting ring.
Thus, for example, five individual parts are required for manufacturing the magnet. The individual components, internal field, valve jacket, and connecting ring, must be manufactured with a high precision and assembled prior to the joining process. The manufacture of the high-precision components and the assembly of the components until firm and tight connections are achieved are complicated and costly processes.
German Patent Application No. 42 30 376, concerning the same species, discloses, among other things, the metal injection molding (MIM) process for manufacturing a valve needle for an electromagnetically actuatable valve. In this process, a single-part actuator, consisting of an armature section and a valve sleeve section, is manufactured by the MIM process. The MIM process includes the manufacturing of molded parts from a metal powder with a binding agent, e.g., a plastic binding agent, for example, using conventional plastic injection molding machines and the subsequent removal of the binding agent and sintering of the remaining metal powder skeleton. Since the composition of the metal powder can be adapted to the optimum magnetic characteristics of the desired molded component in a simple manner, this process is well-suited not only for the manufacture of actuator components, such as valve needles, but also for the manufacture of magnetic circuits for valves. The magnetic circuit is made, in addition to the magnetic coil and the armature, of at least a core, an intermediate ring, and a nozzle holder as parts of the valve housing.
SUMMARY OF THE INVENTION
The process according to the present invention for manufacturing a magnetic circuit for a valve, specifically for a fuel injection valve, has the advantage that a magnet is created economically with fewer individual components than in the prior art. Also advantageous is that a plurality of high-precision components is no longer required, since only one single-part valve housing, for example, an extruded housing, is used as part of the magnet. The valve housing is designed so that an internal field, made later according to the process of the invention, and a valve jacket, also to be formed, are still connected due to the single-part design of the valve housing. The valve housing has, from the very beginning, an external contour that corresponds to the subsequent contours of the internal field and the valve jacket.
It is advantageous to place a non-magnetic, circular intermediate ring into a groove made in the valve housing. It is particularly simple to place the intermediate ring into the groove, since the groove provides a well-defined position for the intermediate ring. An extrusion effect is caused by an axial force from a pressing tool acting upon the intermediate ring. The force acting upon the intermediate ring crea
Hans Waldemar
Schmidt-Hebbel Robert
Hall Carl E.
Robert & Bosch GmbH
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