Inductor devices – With outer casing or housing – Potted type
Patent
1998-05-07
1999-09-07
Gellner, Michael L.
Inductor devices
With outer casing or housing
Potted type
336 92, 336 84, 336205, H01F 2702, H01F 2736, H01F 1700
Patent
active
059493194
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
German Published Patent Appln. No. DE 41 32 851 A1 discloses a bar coil as the ignition coil unit, having a cylindrical casing in its basic form. A rod-shaped core, a primary winding and a secondary winding, each applied to a separate bobbin, are inside the casing, together with several return plates to influence the magnetic field of the bar coil. These elements are separated from one another by gaps, some of which have a small cross-sectional area and must be filled with casting resin without defects to insulate the elements. The casing is closed at one end with a primary terminal and at the other end with a secondary terminal as the high-voltage terminal, so that it is difficult to add the casting resin.
The narrow gap results in an unfavorable filling time from the manufacturing point of view, and the function is endangered by high-voltage sparkovers due to the possible development of air inclusions.
SUMMARY OF THE INVENTION
The bar coil for ignition systems according to the present invention has the advantage over the related art in that the above-mentioned inadequacy is prevented in a satisfactory manner. For this purpose, the bar coil of the present invention is designed so that casting resin can be introduced directly into the bar coil, downstream of the windings, through a channel which is longer than each of the windings of the bar coil. The casting resin travels from the channel into gaps that are adjacent to the windings.
Thus, the bar coil can be filled rapidly, and the casting resin rises as an essentially uniform front back in the opposite direction through the gaps.
This prevents air inclusions which shorten the insulating clearance after curing as bubbles in the casting resin and can thus lead to failure of the bar coil.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE shows a longitudinal section through the bar coil.
DETAILED DESCRIPTION
A bar coil 11 that is used as the ignition coil in an internal combustion engines is provided according to the FIGURE for direct contacting with a spark plug 12, which is installed in the usual manner (not shown here) into a shaft in a cylinder head of an internal combustion engine.
Bar coil 11, which is a basically rotationally symmetrical part, has an elongated cylindrical core 14 made of a magnetic material in a coaxial arrangement with longitudinal axis 13, with a central channel 16 running through the core 14.
Concentrically around core 14 there is arranged a first bobbin 17 as the primary bobbin made of plastic, which may be implemented by coating core 14 or as a separately assembled body. Primary winding 18, which carries a low voltage, is applied to the first bobbin 17.
A second bobbin 21 which is provided with secondary winding 22 carrying a high voltage is arranged with a small radial distance as a first gap 19 to primary winding 18.
As an alternative, secondary winding 22 may also be arranged on the inside with primary winding 18 on the outside.
A tubular casing 24 made of plastic follows at a small radial distance (second gap 23) to secondary winding 22. Outside of casing 24, or as an alternative inside the casing 24, is a return element 26 that is provided as a sheet metal part in the form of a jacket to shield the magnetic field of bar coil 11 toward the outside.
At the end of casing 24 there is connected, first, a high-voltage terminal 27 for transferring the ignition power of bar coil 11 to spark plug 12, which is indicated only with dashed lines, and, second, a connecting segment 29. Interior space 30 is formed between casing 24, high-voltage terminal 27 and connecting segment 29.
High-voltage terminal 27 comprises a dome 31, a protective jacket 32, an electrode 33 and a contact spring 34.
Dome 31 is a basically sleeve-shaped plastic part formed as one piece with casing 24, and it is arranged coaxially with longitudinal axis 13. As an alternative, it may also be a plastic part which is separate from casing 24 and surrounds contact spring 34, which is electrically connected to a terminal stud 36 of spark plug 2
REFERENCES:
patent: 5101803 (1992-04-01), Nakamura et al.
patent: 5146906 (1992-09-01), Agatsuma
Endres Wolfgang
Nuebel Karl-Heinz
Gellner Michael L.
Mai Anh
Robert & Bosch GmbH
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