Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-08-19
2001-04-17
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C029S840000, C174S266000, C361S707000, C361S773000, C361S776000, C361S749000
Reexamination Certificate
active
06219247
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention belongs to the automotive arts. Specifically, the invention relates to a control unit for a motor vehicle. The control unit comprises a base plate formed with press-fit openings in an outer area; a conductor-track carrier mounted on the base plate and formed with conductor tracks that are routed to the press-fit openings and that each have electric contacting tabs formed in the area of the press-fit openings. An electronic circuit is electrically connected to the conductor-track carrier, and a housing cover is coupled in an oil-tight manner to the base plate. A plastic supporting body is coupled to the base plate in a bearing area and at least one electric conductor is encapsulated within the supporting body. A contact pin that is electrically connected to the conductor emerges from the supporting body in the bearing area projects into a press-fit opening in the base plate and there establishes an electrical connection with a contacting tab of the conductor-track carrier. The invention further pertains to a method of producing a control unit of that kind.
The integration of engine and gearbox control units into the motor-vehicle subassembly that is to be controlled by the control unit (i.e., the engine or gearbox) is already known in the art. Integrated control units of the kind must be sealed off from oil, remain functional over a wide temperature range (about −40° C. to 140° C.) and be highly resistant to vibration (up to about 40 g). Furthermore, the units must meet particularly high reliability requirements since removing the units from the engine or the gearbox and refitting them, as required for repair, is very costly.
A control unit as generally described above is disclosed in the commonly assigned German patent application 197 12 842.4 (published after the priority date of this application). The earlier disclosure has a housing of simple construction which can be produced economically. The control unit is supported by a supporting body in which the housing cover is integrally formed. The electrical conductors in the supporting body are connected electrically to the electronic circuit in the control-unit housing by means of conductor pins, which are provided in a bearing area of the housing cover, project into insulating bushes of the base plate and there in each case establish an electrical connection with a conductor-track tab of the conductor-track carrier. The tab is pulled into the insulating bush.
That control unit essentially meets the above-mentioned requirements with regard to oil-tightness, ability to function over a wide temperature range, and vibration resistance.
SUMMARY OF THE INVENTION
It is nevertheless an object of the invention to provide a motor vehicle control unit, which overcomes the disadvantages of the heretofore-known devices and methods of this general type and which can be produced economically and, at the same time, provides contacting of the electronic circuit to the electrical conductors in the supporting body in a manner which is particularly operationally reliable and stable in the long term. It is a further object of the invention to specify a method for producing a control unit of that kind.
With the foregoing and other objects in view there is provided, in accordance with the invention, a control unit for a motor vehicle, comprising:
a base plate having an outer area formed with a plurality of press-fit openings;
a conductor-track carrier mounted on the base plate and having conductor tracks routed to the press-fit openings and each including an electric contacting tab formed at the press-fit openings;
an electronic circuit connected electrically to the conductor-track carrier;
a housing cover connected in an oil-tight manner to the base plate; and
a plastic supporting body having a bearing area coupled to the base plate, carrying at least one encapsulated electric conductor, and a contact pin electrically connected to the conductor, the contact pin emerging from the supporting body in the bearing area, projecting into a respective one of the press-fit openings formed in the base plate, and electrically contacting a respective one of the contacting tabs of the conductor-track carrier;
wherein the contacting tab of the conductor-track carrier is formed with a reserve of material diminishing as the contact pin is pressed into the respective the press-fit opening, whereby the reserve of material causes the contacting tab to be anchored in the press-fit opening in an essentially tension-relieved manner.
The anchoring of the contacting tab in the press-fit opening in a manner which is essentially relieved of tension, as provided according to the invention, ensures a number of advantages. Since there is a free length of contacting tab available during the entire press-fitting process owing to the reserve of material, there are virtually no, or only very slight, shearing and tensile forces on the contacting tab in the area of the edge of the press-fit opening. Tearing of the contacting tab during the pulling-in operation can thus be reliably prevented and an essentially stress-free or at least low-stress end position of the contacting tab in the press-fit opening as regards shearing and tensile forces is also achieved. This is advantageous because the contact location is significantly less sensitive to environmental effects such as vibration or extension of the material due to changes in temperature in the low-stress or stress-free state than when it is under tension. Another advantage is that, by virtue of the reserve of material, the contacting tab is always drawn into the press-fit opening together with the contact pin and essentially without a movement relative to the latter. The pressure contacting to which this gives rise generally has better electrical contact properties than friction contacting because, unlike friction contacting, no damage to the contact surfaces occurs. Another advantage achieved by means of the invention is that, by virtue of the reduction in the shearing and tensile forces that occurs during press-fitting, the total press-in force that has to be applied when joining the supporting body and the base plate together is reduced. Since, in practice, there is generally a multiplicity of contact pins, this effect is very desirable because a joining process that takes place under comparatively low mechanical loading is easier to control in terms of production engineering and can therefore be carried out more reliably.
If the length of the reserve of material of the contacting tab is equal to the penetration depth of the contact pin into the press-fit opening (i.e. the free length of the contact pin minus a slight gap between the base plate and supporting body joined together), the reserve of material is just used up as the base plate is joined to the supporting body but the tension-relieved state in the end position is not compromised. However, the length of the reserve of material can be greater than the penetration depth of the contact pin into the press-fit opening.
In accordance with an added feature of the invention, the length of the reserve of material of the contacting tab is greater than the diameter of the press-fit opening.
For optimized process reliability from a production-engineering point of view, the press-fit connection should be designed in such a way that the contacting tab is drawn into the press-fit opening virtually without friction. This can be influenced both by the choice of material for the joining partners and by means of their structural design. As regards their structural design, the free end of the contact pin is preferably rounded, in particular hemispherical, and/or the press-fit opening is provided with an insertion bevel in its entry area. This ensures that the contact pin slides into the press-fit opening and the shearing and tensile forces grow only gradually. It is thereby possible to prevent the contact pins from sticking in the press-fit opening, this being advantageous since, as is well known, significantly high
Franzen Frank
Haupt Detlef
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Thompson Gregory
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