Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-07-28
2001-11-27
Tung, T. (Department: 1743)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S426000, C204S428000
Reexamination Certificate
active
06322681
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gas sensor, in particular for determining the content of gases in the exhaust of an internal combustion engine, with a contact part carrier composed of two opposing, externally symmetrical half-shells which engage in and make contact with the terminal end of a sensor which extends axially and is installed in a tubular protective sleeve, with the half-shells of the contact part carrier being held together by a spring element.
BACKGROUND INFORMATION
A gas sensor is known, for example, from German Patent Application No. 41 26 378. With the known design, two contact shells in which the electric contact parts are mechanically secured are pressed against the contact points of the sensor element by a horseshoe-shaped or hexagonal spring element which is open at one end. A spring element (spring clip) which is also clipped on it ensures the vibrational strength of this design. However, when more than six terminals are provided on the sensor, secure contact for all contact points is no longer guaranteed. In addition, the installation space would be too small due to the additional space required for the mechanical anchoring of the contacts.
SUMMARY OF THE INVENTION
An object of the present invention is to permit vibration-proof contacting that is thermally stable up to a temperature of 500° C. and is vibration-resistant up to 1300 m/s
2
for a gas sensor having at least seven terminals, with negligible contact resistance (in the nano-ohm range) so that a sufficiently great pressing force of the half-shells of the contact part carrier can be achieved with a single inexpensive spring element, while at the same time facilitating assembly of the contact part carrier.
The above-mentioned object is achieved according to the present invention with a gas sensor by designing the spring element so that it exerts only a low clamping force on the half-shells of the contact part carrier in an initial bracing step when the contact part carrier is pre-mounted on the terminal end of the sensor, so that the sensor can still be inserted easily between the two half-shells, and by the fact that in a second bracing step, it presses with a greater force from all sides against the half-shells, pressing them against the load-bearing contact points, than in the first bracing step through the inside wall of the protective sleeve.
The present invention is a combination of a soldered or welded connection and a clamped connection, with the actual contacting being achieved by the soldered or welded connection, but the mechanical load relief and short-circuit protection being provided by the half-shells of the contact part carrier.
The externally symmetrical half-shells of the contact part carrier are held together by the spring element designed according to the present invention, which exerts only a low clamping force on the half-shells in the first bracing step, so that the end of the sensor element with the contacts can still be inserted easily during assembly.
The protective sleeve may have a specific inside diameter which is adapted to the outside dimensions of the contact part carrier as well as the spring element pushed over it, so that the second bracing step is achieved on pushing the protective sleeve having a specific inside diameter onto it. As an alternative, the protective sleeve may have a circular caulking, so that this circular caulking causes a subsequent reduction in the inside diameter of the protective sleeve and thus produces the second bracing step.
This spring element is preferably a ring spring made of steel, which may come in various shapes, e.g., a helical spring with inclined windings such as that available under the brand name Bal Seal from Bal Seal Engineering Europe BV, Rhijnspoorplein 26, Amsterdam. As an alternative, the spring element may also be a spiral spring made of thin spring wire coiled up into a ring, which is slightly deformed into an oval when the outer protective sleeve is pushed over it. Additional spring elements may include U-shaped rings made of thin spring strips or star-shaped rings which are brought to their second bracing step either when the protective sleeve with a corresponding inside diameter is pushed onto them or by a subsequent reduction in the diameter of the protective sleeve, in particular by circular caulking.
As a result of this subsequent bracing step, the half-shells of the contact part carrier are exposed to a force acting symmetrically from all sides due to the design of the spring element according to the present invention, so that the contacts withstand the required vibrational load.
Due to subsequent setting processes during operation, which can be accelerated by a suitable design of the contact parts, the contacts which are not initially located in the magnetic flux are put under load, and thus the load on the soldered joints or welded joints is relieved when there are more than three contacts per side.
On the whole, the gas sensor designed according to the present invention has the following advantages:
more than three contacts are possible per side of the sensor;
a second additional clip spring can be omitted;
extremely reliable contact behavior is achieved due to the combination of the soldered or welded joint with clamping by the spring element;
the components used are inexpensive; and
known manufacturing methods can be used for the most part.
REFERENCES:
patent: 4339320 (1982-07-01), Friese et al.
patent: 4915815 (1990-04-01), Shibata et al.
patent: 5246562 (1993-09-01), Weyl et al.
patent: 5711863 (1998-01-01), Henklemann
patent: 5900129 (1999-05-01), Tsuji et al.
patent: 5948963 (1999-09-01), Kato et al.
patent: 6083371 (2000-07-01), Weyl et al.
Kenyon & Kenyon
Robert & Bosch GmbH
Tung T.
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