Control element with proximity sensor

A control element includes a switching element, an operating element for operating the switching element, a printed circuit board, and an electrically conductive sensor element of a capacitive proximity sensor integrated in the operating element. The electrically conductive sensor element is designed to be electrically conductively connected to the printed circuit board.

BACKGROUND OF THE INVENTION

The invention relates to a control element, particularly for a motor vehicle component, having an operating element which is mounted so as to move in a support element and which acts on a switching element, in particular.

To control motor vehicle components, such as in a radio appliance, in a navigation appliance, in a car telephone, in a multimedia installation and the like, control and display devices are frequently used which are arranged ergonomically in the vehicle. In this case, the display device should be arranged such that the driver can observe it with as little diversion from the road traffic as possible. The display unit is therefore preferably arranged in the region of the dashboard or in the upper region of a central console. The control unit is preferably arranged such that the driver can reach it with his fingers without a relatively great arm movement. However, this arrangement of the control unit has the drawback that the control unit can be observed visually only very poorly. The driver will therefore frequently feel his way to and select the control elements on the control unit without any visual contact. It is therefore desirable to detect the approach of the driver's hand to a control element, for example in order to be able to output advice of the type of control element or the function to be controlled thereby on the display device or else an audible acknowledgement before the control element has been operated and the action linked to it has been executed.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a control element which identifies an approach to the control element, but at the same time provides the conventional functionality of a control element without restrictions.

According to a preferred embodiment of the present invention, the control element includes a switching element, an operating element for operating the switching element, a printed circuit board, and an electrically conductive sensor element of a capacitive proximity sensor integrated in the operating element. The electrically conductive sensor element is designed to be electrically conductively connected to the printed circuit board. The sensor element being integrated in the operating element means that the sensor element either forms part of the operating element or is arranged inside the operating element. In any case, however, the sensor element cannot be identified by the user and therefore in no way adversely affects the visual appearance of the control element. The corresponding electrically conductive connection of the sensor element to the printed circuit board allows a sensor signal from the sensor element to be forwarded easily to signal-processing elements, which can be arranged on the printed circuit board. A suitable arrangement of the sensor element as a part of or within the operating element and a suitable connection of the sensor element to the printed circuit board ensure that the conventional functionality of the control element, which can particularly be formed as a pushbutton switch, is not adversely affected.

The sensor element may be formed as an angled, elastically deformable metal element or metal-coated plastic element which has a first and a second leg, wherein the first leg projects into the operating element and is fixedly connected thereto, and the second leg is supported on a conductive face of the printed circuit board on a side of the printed circuit board which faces the operating element. This ensures that the sensor element is securely connected to the printed circuit board. Even when the operating element is operated, particularly when an operating element of a pushbutton switch is pressed, the elastically deformable configuration of the metal element or of the metal-coated plastic element ensures reliable contact with the printed circuit board in all phases of the operation of the control element.

The sensor element may be formed as an angled, elastically deformable metal element which has a first leg and a second leg, wherein the first leg is fixedly connected to the printed circuit board and the second leg acts on an inner front portion of the operating element as a spring element. In this arrangement, the sensor element simultaneously brings about the returning of the operating element of the pushbutton switch into the position of rest, so that this requires no additional elements such as a spring or an elastic rubber element. The space required by a control element, which is small anyway, can be even lowered as a result of this combination of sensor element and returning element.

The sensor element may have a portion which is provided with a metal coating, projects through the printed circuit board and, in a position in which the pushbutton switch is at rest, rests against a conductive face of a side of the printed circuit board which is remote from the operating element. The sensor element and possibly also an additional element for field orientation are in this case implemented by means of a two-component operating element with a partly metal coating. In this case, the electrical connection of the sensor element to the printed circuit board is likewise made via the metal-coated region of the operating element. The operating element and the sensor element are therefore of integral design, so that additional assembly complexity is not required.

The sensor element may be arranged on an internal surface of the operating element as a metal coating, and the electrical connection to the printed circuit board may be established by means of a sliding contact element which is fixedly connected to the printed circuit board. In this context, the operating element for a pushbutton switch is formed as a two-component injection-molded part. Further, one of the components is chosen such that its surface may be coated so as to be metallically conductive. The metal coating is the actual sensor element. Contact to the printed circuit board is established by means of a sliding contact element which is fixedly connected to the printed circuit board and rests against the metal coating of the operating element. The sensor element can therefore also be produced in complex geometries which cannot be produced in a stamping process for a metal element, for example.

The sensor element may be fixedly connected to the operating element, with a subregion of the sensor element projecting into a metal-coated recess in the printed circuit board and resting against the metal coating. The metal-coated recess may, in particular, be a through hole in the printed circuit board. In this case too, contact is established between the printed circuit board and the sensor element in the form of a sliding contact. The sensor element itself may be formed as a separate metal element or a conductive coating for a two-component plastic key.

In another embodiment, the switching element may contain a switching mat arranged on the printed circuit board, the sensor element may have been arranged on the operating element as a metal coating, and the switching mat may have an electrically conductive layer which is connected both to the conductive coating of the operating element and to the printed circuit board. The use of an electrically conductive plastic material for subregions of the operating element and of a conductive coating, connected thereto, for a switching mat in the form of a switching element provides a simple way of establishing a conductive connection between the sensor element and the printed circuit board. In particular, this embodiment allows the operating element to engage on the side of the switching mat opposite to the operating element, with the conductive coating of the operating element, in a position in which the control element is at rest, resting against the electrically conductive layer of the switching mat. In this case, the switching mat is simultaneously used as a stop for the operating element in the position of rest, its rubber-like material simultaneously ensuring noise damping when the key is returned from the operating position to the position of rest.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1schematically shows a control element formed as a pushbutton switch with a linearly moving operating element1which is mounted in conventional fashion in a support element (not shown here) so as to move linearly. Pressure on the operating element1moves it toward the printed circuit board2. The operating element1may be returned to the position of rest by a spring element (likewise not shown), for example. The operating element1has an interior space3. Projecting into the interior space3of the operating element1is a first leg4of an angled and elastically deformable metal element5. The first leg4is firmly connected to the operating element1, which is made of a plastic material. A second leg6is arranged at an angle of slightly more than 90 degrees relative to the first leg4and is supported on a conductive face7of the printed circuit board2. The second leg6is electrically connected to the printed circuit board2by means of snap-in hooks.

When the operating element1is pressed, the metal element5adapts to the movement, that is to say that the angle between the first leg4and the second leg6becomes slightly smaller. When the operating element1is released, the spring action of the metal element5assists the returning of the operating element1to the position of rest. The metal element5is the sensor element of a capacitive proximity sensor, where, by way of example, changes in capacitance between the sensor element (metal element5) and a ground element occur, in a manner which is known per se, when a hand approaches the operating element1, and are evaluated in an evaluation circuit.

FIG. 2schematically shows a second embodiment of a pushbutton switch according to the invention. In this context, the sensor element is in turn formed as an angled, elastically deformable metal element30, but now a first leg8is fixedly connected to the printed circuit board and a second leg9acts on an inner front portion10of the operating element1as a spring element.FIG. 2shows both the position of rest and the pretensioned operating position (in dashes) of the second leg9. The pretensioned position is obtained when the operating element1is depressed. Additional components for returning the operating element1from the operating position to the position of rest are not required in this embodiment.

FIG. 3schematically shows another refinement of a pushbutton switch, where the sensor element is formed as a portion12of the operating element1, the portion being provided with a metal coating11. The sensor element portion12projects through an opening13in the printed circuit board2and has an angled end14abutting against a conductive face7of the printed circuit board2, the conductive face7being arranged on the side of the printed circuit board2which is remote from the operating element1. The conductive coating11of the sensor element portion12of the operating element1therefore firstly results in the formation of the sensor element itself and secondly also ensures a reliable contact with the conductive face7of the printed circuit board2in the position in which the operating element1is at rest. In a position in which the operating element1is being operated, on the other hand, there is no contact between the sensor element and the printed circuit board. This is also not necessary, however, since at this time it is not necessary to detect an approach. The partial metalization of the operating element1and the use of this metalized face both for the sensor element and for orienting the field allow the entire sensor system to be produced in a very space-saving manner. In particular, in this embodiment, the interior space3is preoccupied only insignificantly by the additional arrangement of the sensor element of the capacitive proximity sensor and can therefore accommodate insertable illumination elements and the like in an almost unchanged manner.

FIG. 4shows another embodiment, in which the operating element1is formed as a two-component plastic part. In this context, a first key component15is made of a nonmetalizable plastic, while a second key component16is made of a metalizable plastic. A conductive coating17is layered onto the second key component16, which represents the actual sensor element of the capacitive proximity sensor. The printed circuit board2has a sliding contact element18fixedly connected to it, the sliding contact element18additionally resting against the conductive coating17. By means of the sliding contact element18it is ensured that during the operation of the key a reliable connection between the conductive coating17and the printed circuit board2is maintained.

FIG. 5shows another embodiment of a pushbutton switch, where the operating element1is arranged and guided in a faceplate19. The electrically conductive sensor element20is fixedly connected to the inside wall of the operating element1. A subregion21of the sensor element20projects into a recess22in the printed circuit board2, the recess22having a metal coating23. The sensor element20may be formed as a conductive metal element or as a conductive region of a two-component operating element.

FIG. 6shows another exemplary embodiment, in which the operating element1comprises two subregions, a nonconductive subregion24and a conductive subregion25. The conductive subregion25is in contact with a switching mat26which is arranged on the printed circuit board2. When the operating element1is pressed, the switching mat26closes contacts on the printed circuit board2in a known fashion. The switching mat26has an electrically conductive surface coating27establishing a contact between a top of the switching mat26and an underside of the switching mat. The conductive surface coating is connected both to the conductive subregion25of the operating element1and to the printed circuit board2, so that an electrically conductive connection is ensured between the conductive subregion25acting as sensor element and the printed circuit board2. In addition, this exemplary embodiment has a light-emitting diode28arranged on the printed circuit board2in order to illuminate the operating element. A light-emitting diode of this kind may also be provided for all the preceding exemplary embodiments.

FIG. 7shows another embodiment, in which the operating element has a nonconductive subregion24and a conductive subregion25, as in the case of the embodiment shown inFIG. 6. On the printed circuit board2, a switching mat26is arranged whose side facing the printed circuit board2has an electrically conductive surface coating27. The conductive subregion25of the operating element1now likewise rests against this conductive surface coating27of the switching mat26, so that the conductive surface coating of the switching mat26ensures that a contact is established between the conductive subregion25of the operating element1acting as sensor element and the printed circuit board2in the position in which the operating element1is at rest. In this embodiment, the operating element1projects into an opening13in the printed circuit board2. An LED28arranged on the printed circuit board2again allows the operating element to be illuminated.

Various examples have been illustrated to show how a capacitive proximity sensor element formed by an electrically conductive region of an operating element can be in reliable contact with a printed circuit board, wherein the sensor element likewise hardly restricts the integration of further components into the operating element and may additionally perform the function of other components of a pushbutton switch.