Abstract:
A position encoder includes a sensor unit and an encoder unit configured to follow a motion of a lever by means of a pusher so as to enable the sensor unit to capture said motion. The encoder unit and the sensor unit include separate housings connected to each other. The connection between the housings of the encoder unit and the sensor unit is implemented by means of a hollow riveted connection with at least one fastening element configured to be guided into the hollow space thereof.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2012/051401, filed on Jan. 30, 2012, which claims the benefit of priority to Serial No. DE 10 2011 006 035.9, filed on Mar. 24, 2011 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The disclosure is based on a position encoder and on a pedal unit. 
     Usually, when a position encoder is manufactured, separate assemblies, in particular a sensor unit and a position encoder unit, are combined and prefabricated to form one common physical unit. In this state, at least one electrical characteristic curve is programmed in, said curve requiring predefined distances between the position encoder unit and the sensor unit. This requires nondetachable pre-assembly of the two assemblies, which can be implemented, for example, by means of bonding and/or soldering and/or welding and/or latching and/or screwing etc. The completely assembled position encoder is then mounted on a bearing block of a lever to be sensed. The sensor unit and the position encoder unit are usually embodied with steel sockets which are encapsulated by injection molding and which take up the prestressing force of attachment elements which connect the sensor unit and the position encoder unit to one another and/or connect the completely assembled position encoder to the bearing block of the pedal unit or lever unit. The position encoder, which is connected, to the lever via a driver, for example measures travel or a rotational angle of the lever to be sensed, which lever can be embodied as a pedal crank, for example, in particular as a pedal or as a crank handle etc. 
     Laid-open patent application DE 10 2007 000 649 A1 describes an assembly structure for a position encoder with a sensor unit and a position encoder unit. The position encoder unit follows a motion of a lever by means of a driver, with the result that the sensor unit sense this motion, wherein the position encoder unit and the sensor unit have separate housings which are connected to one another. In this context, the two housings of the position encoder unit and the sensor unit are welded to one another by laser welding and attached to a pedal unit by means of attachment screws via assembly struts. 
     SUMMARY 
     The position encoder according to the disclosure, has, by contrast, the advantage that the connection between the housing of the position encoder unit and the housing of the sensor unit is implemented by means of at least one hollow riveted connection, in the cavity of which at least one attachment element can be guided. Embodiments of the present disclosure therefore make available an inseparable connection between the position encoder unit and the sensor unit and at the same time a means for guiding a corresponding attachment element, said means being necessary for mounting the position encoder on the bearing block of the lever unit. With this type of connection between the two assemblies, the assembly of the complete position encoder is advantageously facilitated since the means for guiding the attachment element is already present. Furthermore, embodiments of the present disclosure permit a space-saving connection of the two assemblies since all the necessary attachment measures and/or connection measures are carried out at one region. The use of a hollow rivet for connecting the two assemblies and for guiding the attachment element is also more economical in terms of material since there is no need for any steel sockets, encapsulated by injection molding, for the respective attachment element. Furthermore, the at least one attachment element cannot damage the housings of the two assemblies as a result of excessive tightening since the hollow rivet takes up the prestressing force. In addition, heat-sensitive components can also be used in the assemblies since no welded connections and/or soldered connections are used for assembling the two assemblies. 
     Embodiments of the present disclosure make available a position encoder which comprises a sensor unit and a position encoder unit. The position encoder unit follows a motion of a lever by means of a driver, which motion can be sensed by the sensor unit. The position encoder unit and the sensor unit have separate housings which are connected to one another. According to the disclosure, the connection between the housings of the position encoder unit and the sensor unit is implemented by means of at least one hollow riveted connection, in the cavity of which at least one attachment element can be guided. 
     A position encoder unit is understood here to be a physical unit which comprises a signal encoder for generating a physical variable. The generated physical variable changes indirectly or directly as a result of the motion of the lever via the driver. A possible signal encoder is, for example, a permanent magnet. The associated changeable physical variable is a magnetic field, wherein magnetic field lines of the magnetic field change their direction advantageously by virtue of the motion of the lever. Sources of electromagnetic waves and/or sound waves can be used as further possible signal encoders. An amplitude and/or wavelength and/or wave frequency, which are changed by the motion of the lever, can then be used as the physical variable. The signal encoder can be surrounded by a seal in order to protect it against external influences. 
     A sensor unit is understood here to be a physical unit which comprises at least one sensor which is fixed in relation to the signal encoder and which senses the motion of the lever on the basis of the change in the physical variable generated by the signal encoder. In particular, the angular dependence of the physical variable can be sensed. Depending on the physical property of the signal encoder, the sensor unit comprises, for example, a Hall sensor and/or a magneto-resistive sensor and/or an inductive sensor and/or an optical sensor and/or an ultrasonic sensor and/or a high frequency sensor and/or a radar sensor or some other suitable sensor. Furthermore, the sensor unit comprises an evaluation unit which converts the change in the physical variable into an electrical signal, preferably an actuation signal. An interface, which is embodied as a plug-in connection, for example, outputs the generated actuation signal to a control unit for further processing. 
     Advantageous improvements of the position encoder specified in the disclosure and of the pedal unit specified in the disclosure are possible by virtue of the measures and developments disclosed in the dependent claims. 
     It is particularly advantageous that the connection between the housings of the position encoder unit and the sensor unit of the position encoder according to the disclosure is embodied as at least one tubular rivet. Tubular rivets can advantageously be acquired inexpensively as a mass product in various suitable embodiments and in large quantities. 
     In one advantageous embodiment of the position encoder according to the disclosure, the housing of the position encoder unit and/or the housing of the sensor unit has a spray protection means at the connection region of the two assemblies. The signal encoder of the position encoder unit is arranged in the connection region between the two assemblies. A seal is arranged between the housing of the position encoder unit and the sensor housing in order to protect the signal encoder against external influences, in particular against moisture. In addition, the spray protection means in the connection region between the two assemblies prevents a water jet, which originates from a cleaning device, for example, in particular from a high pressure cleaner, from striking the seal directly and damaging it or making it inoperative. Furthermore, the spray protection means advantageously prevents coarse soiling from entering the interior of the position encoder unit and/or between position encoder unit and the sensor unit and thereby inhibiting the mobility of the signal encoder and/or blocking up the position encoder unit and/or falsifying the position encoder signal. 
     In a further advantageous embodiment of the position encoder according to the disclosure, the spray protection means is embodied as a raised portion and/or oblique portion and/or edge and/or collar. This permits an effective spray protection means which is matched to the external conditions and which increases the functional life of the position encoder by virtue of the fact that internal components are not prematurely worn and/or damaged by contamination and/or moisture. 
     In a further advantageous embodiment of the position encoder according to the disclosure, the housing of the position encoder unit also accommodates the driver. This prevents moisture and/or soiling from entering the interior of the position encoder via the driver. Furthermore, the housing of the position encoder unit protects the driver against external influences such as, for example, against coldness and/or heat and/or moisture and/or external forces which do not originate from the lever motion to be sensed, to which housing the driver is coupled. This ensures that only the motions of the lever which are to be sensed are transmitted via the driver, but no undesired external shocks and/or vibrations. Furthermore, the housing of the position encoder unit protects the driver against damage. 
     In a further advantageous embodiment of the position encoder according to the disclosure, the driver is connected to a shaft and drives this shaft, wherein the shaft is mounted in a hollow axle of the position encoder unit and comprises the signal encoder which is operatively connected to the shaft, wherein the signal encoder generates a physical variable which changes with the motion of the shaft. The sensor unit senses the changeable physical variable and evaluates it. The driver is therefore coupled on one side to the lever and on the other side to the shaft. As a result of a motion of the lever, the shaft is rotated, for example, via the driver. The signal encoder is attached to the shaft by, for example, soldering and/or bonding and/or screwing. In this way, the signal encoder moves with the shaft. The signal encoder and the sensor of the sensor unit are separated from one another by means of an air gap. This permits smooth transmission of the signal. Furthermore, the sensor can be accommodated completely in the housing of the sensor unit if the housing is made of a material which is permeable to the physical variable from the signal encoder. If the signal encoder is embodied as a permanent magnet, for example, the magnetic field lines can penetrate the housing, and the sensor can sense, by way of example, the changes in the magnetic field which are brought about by the rotational motion of the signal encoder. As a result, the sensor can be protected by the housing against external influences. Since there are a multiplicity of possible signal encoders which convert a motion into a changeable physical variable, a multiplicity of possibilities for sensing a change in travel and/or angle are obtained, and these can be matched to the corresponding motion which is to be sensed. 
     In a further advantageous embodiment of the position encoder according to the disclosure, a spring element, which is embodied as a compression spring, is mounted about the hollow axle of the position encoder unit, wherein the spring element regulates the distance between the driver and the shaft and/or the distance between the signal encoder and the sensor unit. As a result, the driver which is mounted on the shaft is advantageously always pressed to one side. As a result, rattling noises are prevented from being generated despite a necessary axial play for the shaft in the hollow axle, with the result that the position encoder according to the disclosure can be operated with a particularly low level of noise. Furthermore, the distance between the signal encoder and the sensor is always kept to the same value, and therefore the measuring accuracy is increased. 
     In a further advantageous embodiment of the position encoder according to the disclosure, the spring element is mounted in such a way that the prestressing force of the spring element moves the driver into a predefined home position. In this context, the spring element is advantageously mounted on the housing of the position encoder unit and on the driver by hooking in, latching, bonding etc. The restoring force of the spring element moves the driver back into its home position. In this way, a constant basic setting is obtained for an unactivated state in which the lever which is to be sensed is also located in its home position. The reliable returning of the driver to its home position does not bring about any change in the characteristic curve which is ascertained. Furthermore, the restoring force of the spring element results in a tolerance offset which compensates for elastic activation deformations in the lever which is to be sensed, and does not transmit such undesired deformations to the position encoder unit. 
     Embodiments of the position encoder according to the disclosure can be used in a pedal unit with a pedal lever and a bearing block, for example, for determining the pedal travel of the pedal lever. In this context, the position encoder is attached to the bearing block of the pedal lever, and coupled to the pedal lever via the driver. Since the position encoder is already completely assembled, it can quickly be connected to any pedal unit. 
     In one advantageous embodiment of the pedal unit according to the disclosure, the position encoder is connected to the bearing block of the pedal unit by means of at least one attachment element which is guided through the cavity of a tubular rivet. This permits extremely fast and cost-effective mounting of the position encoder on the pedal unit. 
     An exemplary embodiment of the disclosure is illustrated in the drawings and will be explained in more detail in the following description. In the drawings, identical reference symbols denote components or elements which carry out the same or analogous functions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded illustration of an exemplary embodiment of a position encoder according to the disclosure from above. 
         FIG. 2  shows an exploded illustration of the exemplary embodiment of a position encoder according to the disclosure from  FIG. 1  from below. 
         FIG. 3  shows a schematic perspective illustration of the assembled position encoder unit for the position encoder according to the disclosure from  FIGS. 1 and 2 . 
         FIG. 4  shows a further schematic perspective illustration of the assembled position encoder unit for the position encoder according to the disclosure from  FIGS. 1 and 2 . 
         FIG. 5  shows a schematic perspective illustration of the assembled sensor unit for the position encoder according to the disclosure from  FIGS. 1 and 2 . 
         FIG. 6  shows a further schematic perspective illustration of the assembled sensor unit for the position encoder according to the disclosure from  FIGS. 1 and 2 . 
         FIG. 7  shows a schematic cross-sectional illustration of the assembled position encoder according to the disclosure from  FIGS. 1 and 2 . 
         FIG. 8  shows a schematic longitudinal-sectional illustration of the position encoder according to the disclosure from  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION 
     As is apparent from  FIGS. 1 to 8 , the illustrated exemplary embodiment of a position encoder  1  according to the disclosure comprises a sensor unit  20  and a position encoder unit  10 . The position encoder unit  10  follows, by means of a driver  14 , a motion of a lever (not illustrated) which is to be sensed, which motion is sensed by the sensor unit  20 . As is also apparent from  FIGS. 1 to 8 , the position encoder unit  10  and the sensor unit  20  have separate housings  12 ,  22  which are connected to one another and are embodied as a plastic housing in the illustrated exemplary embodiment. The connection between the housings  12 ,  22  of the position encoder unit  10  and the sensor unit  20  is implemented by means of at least one hollow riveted connection, in particular by means of a tubular rivet  30 , in the cavity of which at least one attachment element (not illustrated) can be guided. 
     In order to connect the sensor unit  20  to the position encoder unit  10 , the sensor unit  20  is positioned correctly on the position encoder unit  10  by means of two centering pins  36  and two corresponding centering drill holes  34  in the position encoder unit  10 . The housings  12 ,  22  of the two assemblies  10 ,  20  are shaped in such a way that the sensor unit  20  closes off the upper opening region of the position encoder unit  10  except for a narrow region between the underside of the sensor unit  20  and the upper side of the position encoder unit  10 . The tubular rivets  30  are guided through insertion openings  32  provided in the housing of the sensor unit  20  and in the housing of the position encoder unit  10 , and after the insertion are widened and riveted by means of corresponding tools. As a result, the housing  22  of the sensor unit  20  is securely connected to the housing  12  of the position encoder unit  10 , and the tubular rivet  30  is captively attached to the physical unit which is produced. A seal  18 . 2  is arranged between the housing  12  of the position encoder unit  10  and the housing  22  of the sensor unit in order to protect the interior of the position encoder unit  10  against external influences, in particular against moisture and soiling. The seal  18 . 2  is pressed against the housing floor  22 . 1  of the sensor housing  22  by the riveted connection  30 , with the result that a better seal for the position encoder unit  10  can be achieved. 
     As is apparent from  FIG. 3  in particular, the housing  12  of the position encoder unit  10  in the illustrated exemplary embodiment has a spray protection means  12 . 1  in order to protect the connection region between the sensor unit  20  and the position encoder unit against external influences such as, for example, soiling. In addition, the spray protection means  12 . 1  in the connection region between the two assemblies  10 ,  20  prevents a water jet, originating from a cleaning device, for example, in particular from a high pressure cleaner, from striking the seal  18 . 2  directly and damaging it or making it inoperative. In the case of alternative embodiments (not illustrated), the spray protection means  12 . 1  can be arranged on the housing floor  22 . 1  of the sensor housing  22  or both on the sensor housing  22  and on the position encoder housing  12 . 
     As is also apparent from  FIG. 4  in particular, the housing  12  of the position encoder unit  10  also virtually completely accommodates the driver  14 , as a result of which the driver  14  is also protected against undesired external influences. The driver  14  is connected to a shaft  18  which is mounted in a hollow axle  17  of the position encoder unit  10  and is driven by the driver  14 . In this context, the shaft  18  carries out a rotational motion as a result of the motion of the driver  14 . The signal encoder  18 . 1  is embodied as a permanent magnet in the illustrated exemplary embodiment, and is securely connected to the shaft  18 , with the result that the signal encoder  18 . 1  moves with the shaft  18 . The rotational motion of the shaft  18  changes the magnetic field of the permanent magnet  18 . 1 , which is sensed by the sensor unit  20 , for example via at least one sensor  24  which is embodied as a Hall element. The spray protection means  12 . 1  described above advantageously prevents coarse soiling entering the interior of the position encoder unit  10  and/or between the position encoder unit  10  and the sensor unit  20  and thereby inhibiting the mobility of the shaft  18  with the signal encoder  18 . 1  and/or blocking up the position encoder unit  20  and/or falsifying the position encoder signal. The sensor  24  which is fixed with respect to the signal encoder  18 . 1  registers the change in the magnetic field of the signal encoder  18 . 1 . In the illustrated exemplary embodiment, the sensor  24  which is embodied as a Hall element is separated from the signal encoder  18 . 1  of the position encoder unit  10  by means of an air gap and the housing floor  22 . 1 . The sensor  24  which is embodied as a Hall element translates a position of the lever and/or of the driver  14  into an actuation signal. Embodiments of the present disclosure make available a sensor unit  20  with a plug receptacle  26  via which an electrical connection to a control unit can be brought made, which control unit receives and evaluates the generated actuation signal. 
     As is also apparent from  FIGS. 1 to 8 , the position encoder unit  10  has a spring element  16  which is wound around the hollow axle  17  of the position encoder unit  10 . The spring element  16 , which is embodied as a leg spring, serves primarily for returning the driver  14 , but is at the same time also designed as a compression spring. As a result, the permanent magnet  18 . 1  which is bonded into the shaft  14  is always pressed to one side. As a result, the spring element  16  reduces the necessary axial play D 1  between the shaft  18  and a corresponding bearing, which is embodied, by way of example, as a flanged bearing, and prevents the shaft from generating rattling noises in the flanged bearing despite the necessary axial play D 1 . In addition, the distance between the permanent magnet and the sensor  24  which is embodied as a Hall element is always kept to the same value, and therefore the measuring accuracy is increased. The spring element  16  is mounted in such a way that the prestressing force of the spring element  16  moves the driver  14  into a predefined home position when the lever to be sensed is in an unactivated state. 
     Embodiments of the position encoder according to the disclosure can be used, for example, in a pedal unit (not illustrated) with a pedal lever and a pedal block for sensing the pedal travel of the pedal lever. As is apparent from  FIGS. 2 and 4  in particular, the housing  12  of the position encoder unit has pins  12 . 2  for positioning or pre-locating the common physical unit on the pedal block (not illustrated) of the pedal unit.