The invention relates to a combination instrument for displaying measured values or other information, in particular in a motor vehicle. Combination instruments such as these are used in order to inform the vehicle driver of the operating states of the motor vehicle, or to provide him with other information, for example, in the form of navigation instructions.
A combination instrument is known from the prior art, in which electrical and/or electronic components are arranged on a flexible printed circuit. In this case, parts of the flexible printed circuit are clamped in between a rear-face cover and a front-face cover.
One disadvantage of this is that thermal problems occur, in particular when using such a combination instrument in a motor vehicle and when using electrical and/or electronic components. Normally, when using printed circuits with electrical and/or electronic components, thermal problems are avoided by connecting the problematic components directly to heat sinks and/or by cooling them by means of a medium flowing over them, in particular air. Types of cooling such as these have the disadvantage that they are complex and occupy a large amount of space.
The object of the invention is thus to specify simple, space-saving cooling for the components.
This object is achieved in that the rear-face cover of the flexible printed circuit is made of a metallic material, in particular aluminum or copper. The invention makes use of the knowledge that the heat produced by the electrical and/or electronic components can be passed through the thin, flexible printed circuit to the rear-face cover, and that the metallic rear-face cover can be used for effective cooling. Even a large number of heat sources, such as lighting apparatuses and light-emitting diodes, can thus be arranged physically closely adjacent to one another on the flexible printed circuit without any additional further cooling devices. The rearward cover can, for example, be produced by stamping from an appropriate metal sheet.
If there are additional rearward covers, and parts of the flexible printed circuit are clamped in between the additional rearward covers the front cover, it is possible to arrange the visible display at different levels and/or angles by designing the front cover appropriately.
Arranging lighting means directly on the flexible printed circuit also makes it possible to dissipate the heat produced by them effectively via the rear-face cover. Using lighting means in the form of light-emitting diodes results in a permanent lighting apparatus for which no replacement capability or repair facility need to be provided, since, provided the current flow through them is appropriate, the light-emitting diodes have a longer life than the motor vehicle in which they are installed.
Openings in the front-face cover make it possible to arrange even relatively large components directly on the flexible printed circuit, and/or to arrange lighting means remotely from the item to be illuminated on the printed circuit.
Since the openings are surrounded by wall sections which are covered by subsections of an instrument dial, it is possible, for example, to use the light from lighting means for the respective subsections of the instrument dial, for example, in order to illuminate a specific pictogram, which has specific information content.
Since a measuring element is attached to the rear-face cover in such a manner that a part of the flexible printed circuit is arranged between the measuring element and the rear-face cover, it is possible to produce a simple electrical connection between the flexible printed circuit and the measuring element. For example, the measuring element may be screwed or clipped to the rear-face cover. A connection which is particularly simple to produce and, in the process can be produced permanently can be achieved by the measuring element having expanding dowels, which are passed through openings in the flexible printed circuit and in the rear-face cover and are then expanded, thus securing the measuring element.
The measuring element can be driven electrically in a simple manner by said measuring element having electrical connections which are connected to electrical contact surfaces on the flexible printed circuit. This can be done particularly easily if the connections of the measuring element are pressed onto the connections of the flexible printed circuit. If the connections of the measuring element are soldered to the contact surfaces of the flexible printed circuit, the electrical connections are particularly permanent, and are not susceptible to defects.
Since the measuring element has a pointer shaft composed of optically conductive material and the measuring element housing is designed in such a manner that it has an indentation underneath the pointer shaft toward the flexible printed circuit, an optically conductive pointer which is fitted on the pointer shaft can easily be illuminated by means of an illuminating device fitted within the incision on the flexible printed circuit.
If the flexible printed circuit is connected to a rigid printed circuit board, this makes it possible for the drive circuit for the components arranged on the flexible printed circuit to be produced in a space-saving manner on the rigid printed circuit board.
The rigid printed circuit board can be installed easily, permanently, and in a space-saving manner if it can be clipped in behind the rear cover.