RELATED APPLICATIONS 
       [0001]    This application corresponds to PCT/EP2015/059201, filed Apr. 28, 2015, which claims the benefit of German Application No. 10 2014 106 588.9, filed May 9, 2014, the subject matter, of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a spring washer for an indexed rotary switch having a detent cam, and to an indexed rotary switch. 
         [0003]    Indexed rotary switches include a detent cam for a spring-mounted projection to engage therein. The increment of the indexing is predefined by the distance of the individual detent contours of the detent cam, between which the projection can engage. The projection is part of a spring washer, for example, which is arranged between the rotary member of the rotary switch and a base body and urges the rotary member away from the base body, the projection being urged against the detent cam. The spring force, for one thing, causes the projection to be urged into the detent cam or between the detent contours. For another thing, the entire rotary member is urged away from the base body and is thus held to be free of play. By way of supplement, a push-button switch may additionally be integrated by moving the rotary member against an electrical contact contrary to the spring force of the spring washer. 
         [0004]    In the case of such rotary switches it is desirable, on the one hand, to adjust the general resistance when the rotary member is rotated. On the other hand, it is intended for the hardness of the increments, that is, the indexing, to be adjustable, so that white the individual detent steps are perceptible, there is no excessive resistance between the individual detent stages. In addition, it is intended for the resistance to a pushing in to be adjustable in a push-button switch. In the previously known spring washers, only the detent hardness can be adjusted. An additional fractional resistance, which provides for a better haptics of the rotary switch, can only be obtained by separate friction elements. 
       SUMMARY OF THE INVENTION 
       [0005]    It is the object of the invention to provide a rotary switch which allows an adjustability of the friction and of the detent hardness. 
         [0006]    To achieve the object, provision is made for a spring washer for an indexed rotary switch having a detent cam, in particular for a rotary push switch in a vehicle, including at least one indexing section which includes a resiliently yielding projection which is adapted to engage in a detent cam, and at least one contact section which includes a contact surface that can rest at the detent cam, the radius of curvature of the contact surface being considerably larger than the radius of curvature of the projection. According to the invention, in addition to the indexing section by which the indexing of the rotary switch is provided in the known manner, a contact section is provided which can rest at the detent cam but can not engage into it. This means that the contact surface of the contact section is springily pressed against the detent cam, so that an increased friction is produced between the detent cam and the contact surface, the friction providing a resistance when the rotary member is rotated. To prevent the contact surface from engaging between the detent contours and therefore from also providing an indexing, the radius of curvature of the contact surface is considerably larger than that of the projection, the projection being curved such that it can engage between the detent contours, whereas the contact surface is configured such that it can not engage between the detent contours. In this context, “considerably larger” means that the radius of curvature of the contact section is larger than the radius of curvature of the indexing section at least by a factor of 3, preferably by a factor of 5 and particularly preferably by a factor of more than 10. 
         [0007]    In a spring washer of this type it is conceivable that the contact surface and the projection are made to be springy. But a deformation of the contact surface may result in a change in the frictional properties. Also, a deformation of the projection may result in a change in the detent behavior. For this reason, it is desirable for the contact surface and the projection not to be subjected to any heavy deformations during regular operation. Therefore, provision is made that at least one of the indexing section and the contact section each have two spring sections provided thereon which are arranged in the peripheral direction of the spring washer in front of and behind the projection and the contact surface, respectively. These spring sections allow a limited movement of the contact surface and/or of the projection without their becoming deformed themselves. The thickness and/or the shape of these spring sections allow(s) the spring forces by which the contact surface and the projection are pressed against the detent cam to be adjusted separately, so that the frictional resistance and the indexing hardness can be adjusted separately from each other. A further advantage of the spring sections, which are arranged symmetrically in relation to the contact surface and the projection, resides in that the orientations of the contact surface and of the projection are not changed during deflection, so that their orientations in relation to the detent cam are not changed during deflection. 
         [0008]    Different embodiments of the spring washer are possible, depending on the detent cam provided on the rotary switch. The contact surface and the projection may protrude in the radial direction, for example, if the detent cam is provided as an internal or external toothing on the rotary member or on the base body. But, preferably, the contact surface and the projection protrude in the axial direction with respect to the spring washer. In this embodiment, the rotary member is additionally acted upon in the axial direction, so that it is held free of play in the axial direction and a push function can be additionally implemented by moving the rotary member counter to the spring tension. 
         [0009]    Preferably, the at least one indexing section and the at least one contact section are arranged uniformly distributed in the peripheral direction. The uniform distribution of the sections causes a uniform pressure on the rotary member in the axial direction, so that a jamming of the rotary member is prevented. More particularly, it is also conceivable for a plurality of indexing sections and contact sections to be provided, each alternately, that is, each indexing section being followed by a contact section. 
         [0010]    The contact surface is preferably flat and extends substantially in the peripheral direction, so that it can rest flatly at the detent cam. 
         [0011]    To prevent the contact surface from being able to engage in the detent cam, the length of the contact surface in the peripheral direction is, for example, greater than the distance between two detent contours of the detent cam. 
         [0012]    To prevent the spring washer from rotating along with the detent cam, holding tabs are preferably provided on the spring washer for mounting the spring washer so as to prevent rotation, the holding tabs more particularly projecting in the opposite direction than the contact surface and the projection. 
         [0013]    To achieve the object, further provision is made for an indexed rotary switch, in particular a rotary push switch in a vehicle, including a base body, a rotary member which is rotatable about a longitudinal axis and mounted at the base body for limited displacement in the direction of the longitudinal axis, the base body or the rotary member having provided thereon a detent cam with detent contours, and including a spring washer according to the invention, which is held on the rotary member or on the base body so as to prevent rotation and is pretensioned against the detent cam such that the at least one projection of the indexing section engages between two neighboring detent contours and the contact surface of the contact section rests on at least two neighboring detent contours of the detent cam and acts on the rotary member in the axial direction. Since the contact section having the contact surface does not engage into the detent cam, but merely rests on it, the contact surface merely provides a frictional resistance, but no increment or raster. 
         [0014]    To prevent the contact surface from engaging in the detent cam, the length of the contact surface is preferably greater than the distance between two neighboring detent contours, more particularly twice as great as the distance between two neighboring detent contours. 
         [0015]    The detent cam may, for example, be provided on the face side of the rotary member, and the detent contours protrude from the rotary member contrary to the axial direction in relation to the rotary member. In this embodiment, the contact surface and the projection protrude in the axial direction, so that they act upon the rotary member in the axial direction. As a result, the rotary member is held free of play and may additionally be made use of as a push switch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Further advantages and features will be apparent from the description below in conjunction with the accompanying drawings, in which: 
           [0017]      FIG. 1  shows a rotary switch from the prior art; 
           [0018]      FIG. 2  shows the spring washer of the rotary switch of  FIG. 1 ; 
           [0019]      FIG. 3  shows a spring washer according to the invention; 
           [0020]      FIG. 4  shows a first perspective view of a rotary switch according to the invention with the spring washer of  FIG. 3 ; 
           [0021]      FIG. 5  shows a side view of the rotary switch of  FIG. 4 ; 
           [0022]      FIG. 6  shows a second perspective view of the rotary switch of  FIG. 4 ; 
           [0023]      FIG. 7  shows a side view of the rotary switch of  FIG. 6 ; 
           [0024]      FIG. 8  shows a further view of the rotary switch of  FIG. 4 , with a housing being indicated; and 
           [0025]      FIG. 9  shows a sectional view of the rotary switch of  FIG. 4  in the area of the holding tabs of the spring washer. 
       
    
    
     DESCRIPTION 
       [0026]      FIG. 1  shows a rotary switch  10 ′ from the prior art. The rotary switch  10 ′ has a base body  12 ′ which has a rotary member  14 ′ mounted thereon for rotation about a longitudinal axis L′ and for limited displacement in the direction of the longitudinal axis L′. The base body  12 ′ includes a protruding dome  16 ′ which extends into the interior of the rotary member  14 ′. 
         [0027]    Provided on the lower front face, with respect to  FIG. 1 , of the rotary member  14 ′ is an indexing member  18 ′ which includes a detent cam  20 ′ protruding contrary to the longitudinal direction L′ and having a plurality of detent contours  22 ′. Further provided on the base body  12 ′ is a shoulder  24 ′ on which the spring washer  26 ′ rests which is shown in  FIG. 2 . 
         [0028]    The spring washer  26 ′ is stamped out of a metal sheet and has a pair of protruding holding tabs  28 ′ bent at right angles contrary to the longitudinal direction L′ and engaging into slots on the shoulder  24 ′ so that the spring washer  26 ′ is mounted on the base body  12 ′ so as to prevent rotation in the peripheral direction U. The spring washer  26 ′ further includes a pair of indexing sections  30 ′ which each have a projection  32 ′ and spring sections  34 ′ that are arranged in front of and behind the projections  32 ′ in the peripheral direction U. 
         [0029]    As can be seen in  FIG. 1 , the spring washer  26 ′ rests on the shoulder  24 ′ by a pair of holding sections  36 ′ which are located opposite each other in the peripheral direction and have the holding tabs  28 ′ provided thereon, and is held by the holding tabs  28 ′ so as to prevent rotation about the longitudinal axis L′ with respect to a direction of rotation. 
         [0030]    The rotary member  14 ′ is placed with its detent cam  20 ′ on the base body  12 ′ such that the indexing sections  30 ′ are pretensioned in the longitudinal direction L′ between the shoulder  24 ′, that is, the base body  12 ′ and the detent cam  20 ′ of the rotary member  14 ′. This causes the projections  32 ′ to be urged against the detent cam  20 ′ or the detent contours  22 ′ and between the detent contours  22 ′. 
         [0031]    Rotation of the rotary member  14 ′ is only possible when the projections  32 ′ are urged back by the detent contour  22 ′ contrary to the longitudinal direction L′. The projections subsequently snap into the next recess  38 ′ between the detent contours  22 ′. 
         [0032]    In addition, the rotary switch  10 ′ may have a push function, so that an electrical contact is established by pushing in the rotary member  14 ′ contrary to the longitudinal direction L′. 
         [0033]    The resistance to a pushing in of the rotary member  14 ′ may be increased, for example by increasing the spring tension of the spring sections  34 ′. But this also leads to an increased detent hardness of the indexing which is provided by the projections  32 ′ and the detent cam  20 ′. In addition, a separate adjustment of the resistance to rotation independently of the detent hardness is only possible if additional friction elements are provided between the base body  12 ′ and the rotary member  14 ′. 
         [0034]    In order to overcome these problems, provision is made for the rotary switch  10  according to the invention, shown in  FIGS. 4 to 7 , and the spring washer  26  according to the invention, shown in  FIG. 3 . The rotary switch  10  essentially corresponds to the rotary switch  10 ′ shown in  FIGS. 1 and 2 . But, rather than the spring washer  26 ′ shown in  FIG. 2 , the spring washer  26  according to the invention, shown in  FIG. 3 , is used. 
         [0035]    This spring washer  26  likewise has a pair of holding sections  36  located opposite each other and each including a holding tab  28  for mounting the spring washer  26  to the base body  12  so as to prevent rotation. 
         [0036]    However, unlike the spring washer  26 ′ shown in  FIG. 2 , provision is made for only one indexing section  30  having a projection  32  and two spring sections  34  adjacent to the projection  32 . 
         [0037]    In place of the second indexing section, a contact section  40  is provided which has a contact surface  42  that is substantially flat in this embodiment and two spring sections  44  arranged in front of and behind the contact surface  42  in the peripheral direction U. 
         [0038]    Thus, the contact surface  42  in a way replaces the second projection  32 ′ of the spring washer  26 ′ shown in  FIG. 2 . 
         [0039]    As can be seen in  FIG. 3 , the projection  32  has a relatively small curvature, whereas the contact surface  42  has a very large curvature, which, in the embodiment shown here, goes to infinity, so that the contact surface  42  is configured to be approximately flat. 
         [0040]    The spring washer  26  according to the invention is inserted between the base body  12  and the rotary member  14  in place of the conventional spring washer  26 ′ and attached to the base body  12  by means of the holding tabs  28 . 
         [0041]    In the inserted condition, the projection  32  or the indexing section  30  fulfils the same function as in the previously known rotary switches  10 ′, that is, the projection  32  engages between the detent contours  22  and in this way provides an indexing having a detent hardness that is defined by the spring sections  34 . 
         [0042]    As can be seen in  FIGS. 4 and 5 , due to its considerably larger curvature, the contact surface  42 , by contrast, can not engage between the detent contours  22 , but only rests on the detent cam  20 , that is, on the detent contours  22 . 
         [0043]    Thus, while the spring sections  44  provide a spring force in the longitudinal direction L, no additional force is provided for indexing the rotary member  14  since the contact surface  42  can not engage between the detent contours  22 . 
         [0044]    As a result, the contact surface  42  generally increases the frictional resistance in the direction of rotation of the rotary member  14  without changing the characteristic of the indexing by the projection  32  and the detent cam  20 . 
         [0045]    Accordingly, the spring washer  26  has a double function: For one thing, the spring washer  26 , as known from the prior art, provides for the indexing of the rotary switch  10  or of the rotary member  14 . For another thing, the spring washer  26  generally increases the friction between the rotary member  14  and the base body  12  or provides for a spring force in the longitudinal direction L, which, firstly, allows the haptics of the rotary switch  10  to be adjusted and, secondly, allows a mounting free of play of the rotary member  14 , without a change in the characteristic of the indexing. 
         [0046]    The contact surface  42  and the contact section  40  may have any desired configuration here, as long as it is made sure that the contact surface  42  can rest at the detent cam  20 , but can not engage between the detent contours  22 . In order to prevent this, the contact surface  42  is made flat, for example, with the length of the contact surface  42  in the peripheral direction U being preferably greater than the distance between two detent contours  22 . 
         [0047]    In conjunction with the symmetrically arranged spring sections  44 , the illustrated embodiment with a flat contact surface  42  additionally has the advantage that the contact surface  42  is urged across its entire area against the tips of the detent contours  22 , so that a uniform friction can be generated. 
         [0048]      FIG. 8  shows a further view of the rotary switch  10  according to the invention. As a supplement, a code wheel  46  provided on the lower face side of the indexing member  18  and having a reading unit  48  on the base body side is illustrated here as well as an outer cylindrical housing part  60  of the rotary switch  10 . The housing part  50  has a plurality of detent tabs  52  provided thereon for the rotary member  14  or the indexing member  18  to snap in place. 
         [0049]    Unlike in the embodiments shown, however, the spring washer  26  may also be held on the rotary member  14 , and the detent cam  20  is provided on the base body  12 . 
         [0050]    It is also conceivable that the projection  32  and the contact surface  42  are made to be springy in the radial direction and the detent cam is formed as an internal or external toothing on the rotary member  14  or on the base body  12 . 
         [0051]      FIG. 9  shows a sectional view of the rotary switch  10  in the region of the holding tabs  28  of the spring washer. The holding tabs engage into slots  54  on the base body  14 , so that the spring washer is held so as to prevent rotation in the peripheral direction U.
A spring washer ( 26) for an indexed rotary switch ( 10) with a detent cam ( 20), in particular for a rotary push switch in a vehicle, has at least one indexing section ( 30) which includes a resiliency yielding projection ( 32) which is adapted to engage in a detent cam ( 20), and at least one contact section ( 40) which includes a contact surface ( 42) that can rest at the detent cam ( 20), the radius of curvature of the contact surface ( 42) being considerably larger than the radius of curvature of the projection ( 32). According to the invention, further provision is made for a rotary switch ( 10) having such a spring washer ( 26).