Abstract:
In the case of an actuator having a rotation angle sensor with a magnet, no satisfying solution has yet been found for the attachment of the magnet. The invention relates to an actuator having a rotation angle sensor, the magnet of the rotation angle sensor being provided with a plastic cover. The plastic cover and magnet may be easily connected to a first sensor part of the rotation angle sensor of the actuator. The actuator with the rotation angle sensor can particularly be used in motor vehicles.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2008/057061 filed on Jun. 6, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on an actuator having a rotation angle sensor, and a method for manufacturing an actuator. 
     2. Description of the Prior Art 
     In a known actuator (DE 195 25 510 A1), a rotation angle sensor is provided for sensing an angular position of a rotor. Depending on the angular position of the rotor, a gas conduit extending through the housing of the actuator is opened to a greater or lesser degree by means of a throttle element connected to the rotor. In the known actuator, a first sensor part is situated on a gear connected to the rotor and a second sensor part is situated on a cover that is attached to the housing in a stationary fashion. In the actuator disclosed in DE 195 25 510 A1, the rotation angle is measured by means of moving sliders. It is, however, also possible to attach a magnet to the rotor, for example, and to attach a magnetically sensitive element to the stator. Depending on the position of the magnet of the rotor, the magnetic field acting on the magnetically sensitive element changes so that the magnetically sensitive element emits a corresponding electrical signal in accordance with the position of the rotor. Previously, the problem was the lack of a satisfactory solution for attaching the magnet to the rotor. For example, attaching the magnet to the rotor by means of screws would involve highly complex work. Casting the magnet into the plastic material of the rotor is also complex and requires a specific adaptation to different customer wishes and a significantly higher degree of complexity in the manufacture of the rotor. It is also possible to provide a deformable edge on the rotor, which is used by first placing the magnet against the rotor and then deforming the deformable edge so that the deformable edge encompasses part of the magnet, thus securing the magnet to the rotor. However, this has the disadvantage that the material normally used for the rotor, for example plastic, springs back slightly after the plastic deformation, thus resulting in play between the rotor and the magnet. As a result, the magnet can wobble somewhat in relation to the rotor. Another danger is that the deformation can change the properties of the plastic material of the rotor so that with the occurrence of temperature changes during operation of the actuator, the plastic material relaxes and as a result, the firm fit of the magnet is no longer assured. This leads to a distortion of the rotation angle sensor signal. 
     ADVANTAGES AND SUMMARY OF THE INVENTION 
     The actuator according to the invention, having the rotation angle sensor, and the method for manufacturing an actuator according to the invention have the advantage that the magnet embedded in the plastic casing can be attached very easily to the first sensor part. This connection can be produced by means of simple, proven, easy-to-implement, and very controllable manufacturing processes. The plastic casing accommodating the magnet can be very easily attached to the first sensor part, for example by means of ultrasonic welding, rotation welding, friction welding, gluing, etc. 
     Another advantage is that the magnet with the plastic casing can be manufactured as a blank on a mass production scale independently of the actuator, and then the mass-produced blank can be attached to various actuators. This has the advantage that in the event of a change to the actuator, no change to the actual rotation angle sensor is required. 
     Another advantage is that the magnet can be attached to the first sensor part without a high level of complexity by means of a method known to be reliable. A fastening method can be used in which it is known with certainty that no play between the rotor and the magnet will be produced even with the occurrence of temperature changes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferably selected, particularly advantageous exemplary embodiments of the invention are shown in simplified fashion in the drawings and will be explained in detail in the subsequent description in conjunction with the drawings, in which: 
         FIG. 1  shows a first exemplary embodiment of an actuator having a rotation angle sensor according to the invention; 
         FIG. 2  shows a detail of the actuator of  FIG. 1  at a different scale; and 
         FIG. 3  shows another exemplary embodiment of an actuator according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an actuator  2  equipped with a rotation angle sensor  4 . The rotation angle sensor  4  includes a first sensor part  6  and a second sensor part  8 . In the exemplary embodiment shown, the first sensor part  6  is part of a rotatably supported rotor  10 . The second sensor part  8  is part of a stator  12 . In the exemplary embodiment shown, the rotor  10  essentially includes a throttle element shaft  14 , a throttle element  16  fastened to the throttle element shaft  14  for co-rotation, and a rotation element  18  fastened to it for co-rotation. The stator  12  essentially includes a throttle element housing  20  with a gas conduit  22 , which extends through the throttle element housing  20 , and a housing cover  24 . 
     The actuator  2  has an actuator motor  26  for producing an actuation force and a transmission for transmitting the actuating force from the actuator motor  26  to the rotation element  18  of the rotor  10 . The actuating force is transmitted from the actuator motor  26  to the rotor  10  in the form of torques. 
     A detail of the actuator  2  shown in  FIG. 1  is depicted in  FIG. 2  at an enlarged scale and in a sectional view along the rotation axis of the rotor  10 . The plane of the section shown in  FIG. 2  is marked with II-II in  FIG. 1 . 
     In all of the figures, parts that are the same or function in the same manner have been provided with the same reference numerals. Provided that nothing to the contrary is mentioned or shown in the drawing, that which is mentioned and depicted in connection with one of the figures also applies to the other exemplary embodiments. 
     The first sensor part  6  includes a blank  30 . The blank  30  is essentially composed of the magnet  32  and a plastic casing  34 . 
     The magnet  32  is positioned a slight distance apart from the second sensor part  8 . The magnet  32  has a side  32   a  oriented toward the second sensor part  8 . Toward the side  32   a , the magnet  32  has one indentation  32   b  or several indentations  32   b  along its circumference. 
     The blank  30  including the magnet  32  and the plastic casing  34  can be manufactured separately on a machine especially provided for this purpose. The blank  30  is manufactured by inserting the magnet  32  into an injection mold and then injection-molding a plastic material around it. In the process of this, the plastic material travels into the indentation  32   b  provided in the magnet  32 . This produces an intimate, fatigue-resistant, in particular co-rotating connection between the magnet  32  and the plastic casing  34 . The blank  30  can be manufactured so that there is no plastic material on the side  32   a  oriented toward the second sensor part  8  but instead, the magnet  32  extends to the surface of the blank  30  on the side  32   a . This achieves the smallest possible distance between the magnet  32  and the second sensor part  8 . 
     A fastening point  36   a  is provided on the plastic casing  34  of the blank  30 . By means of the fastening point  36   a , a connection  36  is produced between the blank  30  and the rotation element  18  of the rotor  10 . In the exemplary embodiment shown, the fastening point  36   a  is a circumferential end surface oriented toward the rotation element  18 . The fastening point  36   a  of the blank  30  can, for example, be attached to the rotation element  18  by means of glue, ultrasonic welding, laser welding, friction welding, or another known fastening method. An integrally joined, form-locked, or nonpositive, frictional connection  36  can be provided. 
     The second sensor part  8  on the stator  12  includes a magnetically sensitive element  38 . The magnetically sensitive element  38  can be used to sense the strength of a magnetic field and/or the direction of a magnetic field. The element  38  emits an electrical signal as a function of the magnetic field acting on the magnetically sensitive element  38  and/or as a function of the direction of the magnetic field. The rotation angle sensor  4  can thus be used to measure the relative rotation angle position between the first sensor part  6  and the second sensor part  8 . 
     The proposal is made to manufacture the blank  30  so that in lieu of a finished magnet, an as yet unmagnetized material suitable for producing a permanent magnet is provided with the plastic casing  34 . Only after the blank  30  has been attached to the rotation element  18  by means of the fastening point  36   a  and after all of the material-removing machining of the actuator  2  has been completed is the magnetizable material constituting the magnet  32  permanently magnetized by means of a powerful external magnetic field applied to the side  32   a.    
       FIG. 3  shows another exemplary embodiment of an actuator embodied according to the invention. 
     Provided that nothing to the contrary is mentioned or shown in the drawings, the details of the various exemplary embodiments can be combined with one another. 
     In the exemplary embodiment of an actuator  2  shown in  FIG. 3 , which is embodied in the form of a gas pedal, the rotation element  18  is connected to a lever  40 . By pressing on the lever  40 , a driver of a vehicle can produce an actuating force. The actuating force moves the two sensor parts  6 ,  8  in relation to each other. By means of the lever  40 . the driver can move the rotation element  18  and therefore the first sensor part  6  from an unactuated position into an actuated position. It is possible to rotate the first sensor part  6  by means of the manually actuatable lever  40  through. A return spring action likewise acting on the rotation element  18  provides a continuous return force for moving the rotation element  18  into the unactuated position. In the exemplary embodiment shown, the second sensor part  8  provided on the stator  12  constitutes a pedal housing. the rotation element  18  and therefore the first sensor part  6  from an unactuated position into an actuated position. A return spring action  40  likewise acting on the rotation element  18  provides a continuous return force for moving the rotation element  18  into the unactuated position. In the exemplary embodiment shown, the second sensor part  8  provided on the stator  12  constitutes a pedal housing. 
     The actuator  2  with the two sensor parts  6 ,  8  that are movable in relation to each other can be embodied in different ways. The actuator  2  can, for example, be a throttle valve assembly, an electrically adjustable regulating valve, or an actuator in an air-conditioning system, or the actuator  2  can be embodied so that it can be used to control a heat distribution in an internal combustion engine, as a wiper drive unit, as a power window unit, as a power seat adjustment unit, etc. 
     In the preferably selected exemplary embodiments shown, the second sensor part  8  with the magnetically sensitive element  38  is situated on the stator  12  and the first sensor part  6  with the blank  30  is situated on the rotor  10 . This can, however, also be reversed. Depending on suitability of the routing of electrical lines to the magnetically sensitive element  38 , it can be advantageous to provide the magnetically sensitive element  38  either on the stator  12  or on the rotor  10 . 
     The foregoing relates to the preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.