Abstract:
A coupling for the torsion-proof, but radially resilient connection of a stator of an angle encoder with a stator of an object to be measured, the coupling includes a spring element that is either normally in a first position but when the spring element is bent out by a bending force the spring element moves from the first position through a click point to a second position where the spring element engages a portion of the angle encoder or the spring element normally is biased in a first position but when the bias of the spring element at said first position is canceled the spring element is moved to a second position where the spring element engages a portion of the angle encoder.

Description:
[0001]    Applicants claim, under 35 U.S.C. §119, the benefit of priority of the filing date of Mar. 9, 2001 of a German patent application, copy attached, Serial Number 101 11 368.4, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a torsion-proof, but radially resilient connection of a stator of an angle encoder with a stator of an object to be measured. The present invention further relates to an angle encoder having a stator and a shaft, a coupling and a spring element.  
           [0004]    2. Discussion of Related Art  
           [0005]    Angle encoders are used for determining the angular position, the angular speed or other angle-dependent values of a rotor of an object to be measured, in particular a motor, and for making them available for purposes of display, control of a machine tool, regulation or other evaluations.  
           [0006]    For the compensation of alignment errors in the course of coupling the shaft of the angle encoder to the rotor, and therefore of radial deflections of the rotatable rotor, a coupling is arranged between the stator of the angle encoder and the stationary object to be measured, which connects the stator of the angle encoder in a torsion proof, but radially and preferably also axially resilient manner, with the stationary object to be measured.  
           [0007]    Such an angle encoder is known, for example, from DE 195 21 845 C2.  
           [0008]    In connection with the angle encoder in accordance with DE 196 29 585 A1 it was found that it is advantageous for certain applications to arrange the coupling between the stator and the stationary object to be measured in the area of the bearing device of the rotor. The installation space available in this area is very limited, so that problems in reaching and actuating the device for radial clamping of the coupling can arise in actual use.  
           [0009]    An angle encoder with a coupling between the stator and the stationary object to be measured is furthermore described in DE 200 08 590 U1. The leaf spring arms of the coupling are crammed in place on the stationary object because of external pressure, or spring pressure because of a deformation of the coupling. The introduction of the clamping force takes place by an axial displacement of the angle encoder with respect to the stationary object to be measured, and the clamping force is directly proportional to the relative axial position of the two elements. Assembly is made more difficult because of this.  
         OBJECTS AND SUMMARY OF THE INVENTION  
         [0010]    An object of the present invention is based on disclosing a coupling for an angle encoder that is easy to mount.  
           [0011]    This object is attained by a coupling for the torsion-proof, but radially resilient connection of a stator of an angle encoder with a stator of an object to be measured, the coupling includes a spring element either normally in a first position but when the spring element is bent out by a bending force the spring element moves from the first position through a click point to a second position where the spring element engages a portion of the angle encoder or the spring element is normally biased in a first position but when the bias of the spring element at said first position is canceled the spring element is moved to a second position where the spring element engages a portion of the angle encoder.  
           [0012]    It is a further object of the present invention to disclose an angle encoder having this coupling.  
           [0013]    This further object is attained by an angle sensor that includes a first stator and a shaft for measuring an angular position between a second stator of an object to be measured and a rotor, which is rotated with respect to the second stator around an axis of rotation and a coupling for torsion-proof, but radially resilient connection of the first stator with the second stator. The coupling includes a spring element that is either normally in a first position but when the spring element is bent out by a bending force the spring element moves from the first position through a click point to a second position or the spring element normally biased in a first position but when the bias of the spring element at the first position is canceled the spring element is moved to a second position.  
           [0014]    The advantages obtained by the present invention reside in particular in that the coupling can be installed in the vicinity of the bearing device of the rotor of the angle encoder, and that in spite of crowded installation conditions the coupling can be fastened to the stationary object solidly and fixed against relative rotation. A stable and space-saving mounting is possible. During mounting and operation, the force required for assured clamping does not act, at least not completely, on the angle encoder.  
           [0015]    Further advantages, as well as details, of the present invention ensue from the following description of a preferred embodiment, making reference to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a cross section through an embodiment of an angle encoder with a coupling in a first mounting position in accordance with the present invention;  
         [0017]    [0017]FIG. 2 shows the angle encoder in FIG. 1 in the installed state;  
         [0018]    [0018]FIG. 3 is a perspective representation of the coupling of the angle encoder in FIGS. 1 and 2;  
         [0019]    [0019]FIG. 4 is an example of a clamping area of the coupling; FIG. 5 is a further example of a clamping area of the coupling of FIGS.  1 - 3  in a sectional view;  
         [0020]    [0020]FIG. 6 shows the clamping area in FIG. 5 in a view from above;  
         [0021]    [0021]FIG. 7 shows a second embodiment of a clamping area of the coupling of FIGS.  1 - 3 ; FIG. 8 shows a third embodiment of a clamping area of the coupling of FIGS.  1 - 3 ;  
         [0022]    [0022]FIG. 9 represents a second embodiment of an angle encoder with a coupling in a first mounting position in accordance with the present invention;  
         [0023]    [0023]FIG. 10 shows the angle encoder in FIG. 9 in the installed state;  
         [0024]    [0024]FIG. 11 is a portion of the coupling in FIG. 9 in a view from above;  
         [0025]    [0025]FIG. 12 represents a third embodiment of an angle encoder with a coupling in a first mounting position in accordance with the present invention; and  
         [0026]    [0026]FIG. 13 shows the angle encoder in FIG. 12 in the installed state.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    A first exemplary embodiment of the invention is represented in FIGS.  1  to  3 . The angle encoder  1  includes a shaft  2 , to which a graduated disk  3  with a measurement representation  4  has been attached. The shaft  2  is seated, rotatable around the axis of rotation D, by a bearing device  5  in the stator  6  of the angle encoder  1 . The angular position of the shaft  2  in relation to the stator  6  is measured in that the measurement representation  4  is scanned in a known manner by a scanning unit  7  affixed to the stator  6 . In this case, the measurement representation  4  can be a pattern in the form of an incremental or coded graduation, which can be optically, magnetically, capacitively or inductively scanned.  
         [0028]    For measuring the angular position of a rotor  8 , which is rotatable around the axis of rotation D, in relation to a stationary object  9 , the shaft  2  must be connected, fixed against relative rotation, with the rotor  8 . The stator  6  must also be connected in a torsion-proof manner with the stationary object  9 . In the example represented, the rotor is the shaft  8  of an electric motor, and the stationary object is the motor housing  9 .  
         [0029]    For compensating alignment errors between the shaft  2  and the shaft  8 , as well as for compensating tumbling movements, as well as axial displacement, of the shaft  8 , the stator  6  is mounted on the motor housing  9  by a torsion-proof, but radially and also preferably axially elastically compensating coupling  10 .  
         [0030]    Before the angle encoder  1  is inserted into the mounting space  11 , which is constituted by the motor housing  9 , one connecting area of the coupling  10  is rigidly fastened on the stator  6  of the angle encoder  1 . This can be accomplished by screws, which engage bores  13  (FIG. 3) of the coupling  10 . Fastening can also be provided by riveting, gluing or welding, but the coupling  10  can also be formed on the stator  6 .  
         [0031]    Thereafter, the angle encoder  1  with the coupling  10  is pushed into the mounting space  11  and is axially (direction A) guided to the motor shaft  8 . Note that in order to accomplish this insertion, the spring  12  is curved so that the radial, exterior circumference of the clamping jaws  16  is less than the radius of the circumferential surface  17 .  
         [0032]    In the course of this axial guidance, an axially acting stop face  14  of the coupling  10  abuts on a stop face  15  of the motor housing  9 , which extends transversely with respect to the axis of rotation D. A position is reached during the continued approach of the angle encoder  1 , in which the connecting areas  16  of the coupling  10  assigned to the motor housing  9  suddenly move radially outward and are spread against the tube-shaped circumferential surface  17  of the motor housing  9 . In what follows, these second connecting areas of the coupling will be called clamping jaws  16 .  
         [0033]    This jump of the clamping jaws  16  from a first radial position into a second radial position of a greater radial distance (direction R) is achieved by a curved spring  19 , which jumps over from a first position into a second position by a clicker effect.  
         [0034]    The clamping force required for radial clamping of the coupling  10  is introduced by the cooperation of the two stop faces  14  and  15  only until the click point of the curved spring  12  connecting the two clamping jaws  16  has been reached.  
         [0035]    The bending force required for this acts counter to the curved shape of the spring  12 .  
         [0036]    Thus, only the bending force of the curved spring  12  needs to be supplied during the mounting process. After the jump and after overcoming the click point of the spring  12 , no axial force, which is dependent on the radial clamping force acts anymore on the angle encoder  1 . The radial clamping force is exerted by the leaf-like spring  12 , which is advantageously axially supported in the center area on the motor housing  9  after it has been bent over and therefore cannot jump over into a second position of rest, but is maintained in a position in which it exerts the maximum spreading force in the radial direction. The spring  12  and the shaft  2 , or rotor  8 , are of such dimensions that, in the mounted position in accordance with FIG. 2, the spring  12  does not touch the shaft  2  and the rotor  8 .  
         [0037]    During assembly the spring  12  is advantageously supported in the center area on the stator  6  or on a shoulder  20  of the shaft  2  for producing the bending force in the axial direction A.  
         [0038]    The jump-over of the clamping jaws  16  from a first radial position into a second radial position by the cooperation of the stop faces  14  and  15  during the insertion of the angle encoder  1  into the mounting space  11  is particularly advantageous. However, the jump-over can also be initiated in a manner not shown by an actuating tool introduced from the outside.  
         [0039]    The coupling  10  is represented in a perspective view in FIG. 3. The coupling includes a base  30  with two guide elements  31 , which are bent at right angles, extend parallel with each other and parallel with respect to the axis of rotation D, and can be screwed to the stator  6 . Two further guide elements  32  are formed on the base  30 , which extend parallel with each other at least to a large extent, wherein these further guide elements  32  extend at right angles with respect to the base  30 , as well as at right angles with respect to the first guide elements  31 . The clamping jaws  16  for a torsion-proof fastening on the motor housing  9  are formed at the ends of the further guide elements  32 . This coupling  10  has been advantageously produced from spring steel in one piece as a punched and bent part. Guide elements  31 , or  32 , extending parallel with respect to the axis of rotation D, each constitute a parallel guidance in the radial direction R.  
         [0040]    The base  30  and/or the tongues  31 ,  32  can also be embodied in a framework-like manner in accordance with EP 0 762 081 B1.  
         [0041]    The two clamping jaws  16  are connected with each other by the leaf-like spring  12 . This spring  12  is curved in the shape of an arc so that it jumps over from this curved position of rest as the initial position into a second position differing from the first when a pressure force is exerted on it. This pressure force—also called bending force—must be of sufficient size that a click point is overcome. This jump-over of the spring is also known as clicker effect since a clicking sound is generated during the jumping from the curved position of rest shown in FIG. 3 into the second position shown in FIG. 4.  
         [0042]    The clamping jaws  16  can be embodied in different ways. In accordance with FIG. 4 they are embodied in such a way that they engage a groove  21 , coming to a point, of the motor housing  9 . In accordance with FIGS. 5 and 6, the clamping jaws  16  additionally are interlockingly connected in the circumferential direction (direction of rotation of the shaft  2 ) with the motor housing  9 . At least one recess  23  is provided for this purpose in each clamping jaw  16 , which is engaged by a protrusion in the form of a pin  24  of the motor housing  9 . The clamping jaws  16  are supported in a radially clamping manner on the pins  24  and/or on the tube-shaped circumferential surface  17 . The recesses  23  are conically shaped and taper radially inward, so that the edges of the recess  23  are pushed against the pins  24  free of play by the radial clamping forces. The interlocking connection acts as a safety against twisting. The interlocking connection can also be provided by depressions on the motor housing  9 , which are engaged by protrusions of the clamping jaws  16 .  
         [0043]    The clamping jaws  16  in accordance with FIG. 7 also engage a groove  25  of the motor housing  9  in an interlocking manner. Elements  26 , which increase the static friction, for example in the form of a rubber coating, are arranged at the ends of the clamping jaws  16 .  
         [0044]    The clamping jaws  16  in accordance with FIG. 8 are designed as V-shaped spreading elements.  
         [0045]    A second example of an angle encoder  1  with a coupling  10  is represented in FIGS.  9  to  11 . Reference is made to the previous example in regard to the basic structure of the angle encoder  1  and the coupling  10 . The two clamping jaws  16  are connected with each other by the leaf-shaped spring  12 . This spring  12  is a leaf spring or a diaphragm, curved in an arc shape, so that it is displaced from this curved, biased position of rest as the initial position into a second position differing therefrom, in particular by being bent out. In contrast to the previous example, the curved position of rest of the spring  12  is predetermined by at least one pin  27  of the shaft  2 . Thus, the spring  12  is biased, bent in the axial direction, by the pin  27 . The angle encoder  1  with the coupling  10  fastened thereon is inserted in this position, represented in FIG. 9, into the mounting space  11  and the shaft  2  is connected, fixed against relative rotation, with the shaft  8 . Thereafter the bias of the spring  12  is cancelled, so that it jumps over into a second position and the two clamping jaws  16 , which are located radially opposite each other, move radially outward and are clamped in a torsion-proof manner against the circumferential surface  17 . The cancellation of the bias of the spring  12  takes place by rotating the shaft  2  (schematically represented in the view from above in FIG. 11) until the pin  27  fastened thereon reaches a recess  29  of the spring  12  and permits an axial movement of the spring  12 . The end position of the spring  12  and of the clamping jaws  16  achieved by this is represented in FIG. 10. Disassembly is performed in that the angle encoder  1  with the coupling  10  fastened thereon is pulled out of the mounting space  11 —possibly by an auxiliary tool—and in the process the spring  12  comes into contact with stops  28  arranged on the shaft  2  and in this way bends them out axially, because of which the radial distance between the clamping jaws  16  is reduced and the clamping jaws  16  come out of contact with the circumferential surface  17 .  
         [0046]    A third example of an angle encoder  1  with a coupling  100  is represented in FIGS. 12 and 13. The coupling  100  again includes first guide elements  310  which are fastened in a torsion-proof manner on the stator  6  of the angle encoder  1 , and of further guide elements  320 , which are clampingly fastened in a torsion-proof manner on the motor housing  9  by clamping jaws  160 . In this example, the curved leaf-shaped spring  120  for achieving the clicker effect is the base  300  of the coupling  100 , on which the guide elements  310  and  320  are formed.  
         [0047]    As represented in FIG. 12, the angle encoder  1  with the coupling  100  mounted thereon is displaced in the axial direction A into the mounting space  11  until the stop faces  140  of the coupling  100  come into contact axially with the stop faces  150  of the motor housing  9 . In the course of the continued pressing in of the angle encoder  1  a position is reached, in which a bending force directed opposite the arc shape is exerted on the spring  120 , during which the click point for the jump-over of the spring  120  is passed. Because of this jump-over of the spring  120 , the angle encoder  1  moves further in the direction of the shaft  8  until the outer cone of the shaft  8  comes into contact with the inner cone of the shaft  2  and the shafts  8  and  2  are frictionally connected with each other by this. This second mounting position is represented in FIG. 13.  
         [0048]    As with the first exemplary embodiment, here, too, the connection of the coupling  100  with the motor housing  9  is based on the clicker effect of a spring  120 , in that prior to the jump-over of the spring  120  the clamping jaws  160  have a lesser mutual distance from each other in the radial direction R than after the jump-over of the spring  120 . Following the jump-over of the spring  120  from a curved initial position (position of rest) into a second position differing from the first, the clamping jaws  160  are spread in the radial direction R against the tube-shaped circumferential surface  17  of the motor housing  9 , and are therefore clampingly supported in a torsion-proof manner.  
         [0049]    In accordance with FIG. 13, the mounting space  11  is closed by a cover  400  at the end of the mounting process.  
         [0050]    In all examples the guide elements  31 ,  32 ,  310 ,  320  are advantageously radially deflectable leaf springs.  
         [0051]    The explained clamping of the coupling  10 ,  100  can alternatively or additionally also be employed between the coupling  10 ,  100  and the stator  6  of the angle encoder  1 .  
         [0052]    The coupling  10 ,  100  is advantageously arranged at the end of the angle encoder  1  toward the shaft in a space-saving manner. However, it can also be fastened on the other end of the angle encoder.  
         [0053]    The frictional and/or interlocked torsion-proof connection of the shafts  2  and  6  can take place by known tools with screws or collet chucks.  
         [0054]    The foregoing description is provided to illustrate the invention, and is not to be construed as a limitation. Numerous additions, substitutions and other changes can be made to the invention without departing from its scope as set forth in the appended claims.