Abstract:
A multi-stage contactless switch, in particular for an operating element in a motor vehicle, has a movably arranged magnet and several Hall sensor elements spaced apart from each other. Each Hall sensor element is capable of activating a particular switching state depending on a magnetic field of the magnet as detected by the Hall sensor.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a multi-stage contactless switch, in particular for an operating element in a motor vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002]     Multi-stage operating elements in motor vehicles are often realized by several microswitches which are arranged adjacent to each other. In addition to requiring a comparatively large amount of space and the costly mechanical construction, such operating elements have the disadvantage that they are prone to wear, because the electric contacts are produced by physical contact of contact elements.  
         [0003]     Contactless switches based on the Hall effect are generally known. An example of such a switch with two switching states is shown in U.S. Pat. No. 4,061,988. A permanent magnet which is fastened to a pin is linearly displaceable, the permanent magnet being able to be moved from an initial position into a position directly adjacent to a Hall effect sensor switching circuit. The switching circuit responds to the change in the magnetic field and thereby initiates a switching process. A multi-stage operating element based on such a switch type would, however, again require several switches.  
         [0004]     It is an object of the invention to provide a switching device which saves as much space as possible, has a long lifespan, and enables a multi-stage operation in a comfortable manner.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     According to the invention, a multi-stage contactless switch has a movably arranged magnet and several Hall sensor elements spaced apart from each other. Each Hall sensor element is capable of activating a particular switching state depending on a magnetic field of the magnet as detected by the Hall sensor. The invention is based on the finding that the design of a two-stage switch based on the Hall effect is able to be expanded to several switching states by a suitable construction of the switch. Contactless switching processes, which are free of wear, are possible in several stages with the switch according to the invention, without requiring an enlarged operating field for this. As no physical contacts of contact elements have to be taken into account, the mechanical realization of the switching paths and switching points can be largely freely arranged, so that a comfortable operation can be realized, having a pleasant “feel”. The bounce-free switch is therefore suitable for applications in high quality motor vehicles, such as for example for actuating a direct switching gear via an operating element which is arranged on the steering wheel of the vehicle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0006]     In the drawing, the single FIGURE shows diagrammatically the essential elements of a switch according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0007]     The two-dimensional illustration of the FIGURE is restricted to the essential electrical and magnetic components of a multi-stage contactless switch. The mechanical components of the switch will be described after the description of the function.  
         [0008]     A parallelepiped-shaped permanent magnet  10  has an equatorial plane E which separates the north pole N from the south pole S of the permanent magnet  10 . The permanent magnet  10  is linearly movable in the direction of the arrow A and back.  
         [0009]     A bipolar Hall IC switching component  12  contains several (three in the example shown) Hall sensor elements  14 ,  16 ,  18 , which define a sensor axis X. The Hall sensor elements  14 ,  16 ,  18  are arranged at the same distance a on the sensor axis X. The Hall IC component  12  is arranged so that the permanent magnet  10  is guided past in the immediate vicinity (behind the component  12  in the FIGURE), so that it is ensured that the Hall sensor elements  14 ,  16 ,  18  respond reliably and in a defined manner to a change in magnetic field brought about by the movement of the permanent magnet  10 .  
         [0010]     The direction of movement of the permanent magnet  10  runs perpendicularly to the sensor axis X of the Hall IC component. The relative orientation of the Hall IC component to the permanent magnet  10  is selected such that the sensor axis X is tilted by an acute angle φ with respect to the equatorial plane E of the permanent magnet  10 .  
         [0011]     The mode of operation of the multi-stage switch is explained below. The permanent magnet  10  is moved from an initial position in the direction of the arrow A. Ideally, the first Hall sensor element  14  responds precisely when the equatorial plane E of the permanent magnet  10  passes the element, and then activates a first switching process (first switching state). This situation corresponds to the illustration in the FIGURE, which shows the first Hall sensor element  14  precisely on the equatorial plane E.  
         [0012]     Proceeding from this state, a further linear movement of the permanent magnet  10  in the direction of the arrow A by the distance Δs (switching path) is necessary, until the second Hall sensor element  16  responds and activates a second switching process (second switching state). This distance Δs can be calculated by means of simple geometric considerations from the distance a of the two Hall sensor elements  14  and  16  and also the angle φ between the sensor axis X and the equatorial plane E: 
 
 Δs=a· tan φ
 
         [0013]     The same applies to the switching path for reaching the third switching state and to further switching paths in the case of additional Hall sensor elements.  
         [0014]     Vice versa, this means that in accordance with the basic structure of the multi-stage switch shown in the FIGURE, the switching path between two switching states can be prescribed by the distance a between the Hall sensor elements  14 ,  16 ,  18  and the angle φ between the sensor axis X and the equatorial plane E. Of course, different distances of the Hall sensor elements  14 ,  16 ,  18  and therefore switching paths of different lengths are also possible.  
         [0015]     The mechanical realization of the switching paths and switching points may take place for example by means of a suitable connecting link, in which a detent position is provided which is associated with the initial position of the permanent magnet  10  and each switching point.  
         [0016]     Instead of a parallelepiped-shaped permanent magnet  10 , a different magnet shape may also be used, e.g. a cylindrical rod magnet, or a different type of magnet.  
         [0017]     The use of the multi-stage contactless switch according to the invention is not restricted to the operation of a direct switching gear or other operating elements in a motor vehicle. Rather, the advantageous switch may be used generally in the field of household applications and in industry.