Abstract:
An electronic device may be provided with a vibrator. The vibrator may vibrate to alert a user to an incoming cellular telephone call or other events. The vibrator may have a piezoelectric vibrator motor. The piezoelectric vibrator motor may rotate a shaft about a rotational axis. A weight may be attached to the shaft so that the vibrator vibrates when the shaft is rotated. The shaft may have opposing first and second ends. To help prevent damage to the vibrator during a drop event, the first and second ends of the shaft may be supported by support structures and end caps or other structures for retarding axial movement may be provided. The support structures may be formed from a bracket having vertical members with holes that respectively receive the first and second ends. The stop structures may prevent movement of the shaft along its rotational axis.

Description:
BACKGROUND 
       [0001]    This relates generally to vibrators, and, more particularly, to vibrators for electronic devices. 
         [0002]    Electronic devices such as cellular telephones are often provided with vibrators. A vibrator may be used to alert a user to an incoming telephone call or other activity. 
         [0003]    Conventional vibrators are formed from electric motors. A rotationally unbalanced weight is affixed to the protruding end of a motor shaft. As the shaft rotates around a rotational axis, the vibrator and the device to which the vibrator is mounted will vibrate. 
         [0004]    Electronic devices such as cellular telephones and other portable electronic devices may sometimes be accidentally dropped. During a drop event, axial movement of the weight and the motor shaft may cause damage to the vibrator. 
         [0005]    It would therefore be desirable to provide improved vibrators for electronic devices. 
       SUMMARY 
       [0006]    An electronic device may be provided with a vibrator. The vibrator may vibrate to alert a user to an incoming cellular telephone call or other events. 
         [0007]    The vibrator may have a compact piezoelectric vibrator motor. Piezoelectric elements in the vibrator motor may be driven using a drive circuit to cause the vibrator motor to rotate a shaft about a rotational axis. 
         [0008]    A weight may be attached to the shaft so that the vibrator vibrates when the shaft is rotated. The shaft may have opposing first and second ends. To help prevent damage to the vibrator during a drop event, the first and second ends of the shaft may be supported by support structures and stop structures such as end caps may be formed on the ends of the shaft. The support structures may be formed from a bracket having vertical members with holes that respectively receive the first and second ends. Bearings may be placed in the holes. The stop structures that are mounted to the first and second ends of the shaft may prevent longitudinal movement of the shaft along its rotational axis, thereby spreading impact loads among the support structures and helping the vibrator to withstand damage from a drop event. The stop structures may be formed from members that are press fit onto the first and second ends of the shaft, from c-rings that are mounted within grooves on the shaft, from members that are welded to the ends of the shaft, from portions of the shaft that have been deformed, or other structures. 
         [0009]    The vertical members of the bracket may be mounted to a common horizontal member. The horizontal member may have an opening to accommodate movement of the weight about the rotational axis without striking the bracket. 
         [0010]    Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view of an illustrative electronic device of the type that may include a vibrator in accordance with an embodiment of the present invention. 
           [0012]      FIG. 2  is a perspective view of an illustrative vibrator motor that includes piezoelectric elements in accordance with an embodiment of the present invention. 
           [0013]      FIG. 3  is an illustrative bracket for a vibrator motor of the type shown in  FIG. 2  in accordance with an embodiment of the present invention. 
           [0014]      FIG. 4  is a cross-sectional side view of an illustrative vibrator in accordance with an embodiment of the present invention. 
           [0015]      FIG. 5  is a cross-sectional side view of an illustrative vibrator shaft that has portions that have been bent back from the shaft to form a stop structure in accordance with an embodiment of the present invention. 
           [0016]      FIG. 6A  is a cross-sectional side view of an illustrative vibrator shaft with a stop structure formed from a c-ring in accordance with an embodiment of the present invention. 
           [0017]      FIG. 6B  shows an illustrative c-ring of the type used in  FIG. 6A  to form a stop structure on a vibrator shaft in accordance with an embodiment of the present invention. 
           [0018]      FIG. 7  is a cross-sectional side view of an illustrative vibrator shaft having a stop structure that is attached to the end of the shaft using welds or other fastening mechanisms in accordance with an embodiment of the present invention. 
           [0019]      FIG. 8  is a cross-sectional side view of an illustrative vibrator shaft having a stop structure that is formed from flared portions of a deformed end of a shaft in accordance with an embodiment of the present invention. 
           [0020]      FIG. 9  is a perspective view of a vibrator mounting bracket showing how the vibrator mounting bracket may include portions that can be crimped around a shaft in accordance with an embodiment of the present invention. 
           [0021]      FIG. 10  is a cross-sectional side view of an illustrative vibrator shaft mounted in a bracket in which a stop structure has been captured between two opposing bracket members in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Electronic devices such as cellular telephones, tablet computers, media players, other portable electronic devices, and other electronic equipment may be provided with vibrators. 
         [0023]    An illustrative electronic device of the type that may be provided with a vibrator is shown in  FIG. 1 . Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  of  FIG. 1  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, a media player, etc. 
         [0024]    Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes or other touch sensors. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. 
         [0025]    Components such as integrated circuits, connectors, switches, sensors, speakers, microphones, cameras, and other electronic components may be mounted in housing  12 . Vibrator  16  may also be mounted in housing  14 . Vibrator  16  may be used to vibrate device  10 . For example, vibrator  16  may be used to vibrate device  10  when an alarm timer has expired. Vibrator  16  may also vibrate device  10  when an incoming telephone call is received (e.g., when device  10  has been placed in a silent mode in which audible telephone ringing has been suspended). 
         [0026]    Vibrator  16  may be implemented using any suitable vibrator technology. For example, vibrator  16  may include a solenoid, an electric motor, or other electromagnetic device that moves a weight. With one suitable arrangement, which is sometimes described herein as an example, vibrator  16  may be implemented using a vibrator motor that is based on piezoelectric elements. 
         [0027]    An illustrative vibrator motor that has piezoelectric elements is shown in  FIG. 2 . As shown in  FIG. 2 , vibrator motor  18  may have piezoelectric elements  22  mounted on main body member  26 . With one suitable arrangement, there may be four of piezoelectric elements  22 , each mounted on one of the four sides of body member  26  (e.g., on the left and right sides and the top and bottom sides in the orientation of  FIG. 2 ). Arrangements with different numbers of piezoelectric elements (e.g., fewer than four or more than four) and arrangements in which piezoelectric elements are located in different positions relative to shaft  24  and body member  26  may be used if desired. The arrangement of  FIG. 2  is merely illustrative. 
         [0028]    Drive circuitry  20  may be used to provide piezoelectric elements  22  with control signals over control paths  28 . These control signals may control the shape of each piezoelectric element. Shaft  24  may run through the center of body member  26 . Shaft  24  and body member  26  may include interlocking features (e.g., threads), so that shaft  24  rotates when piezoelectric elements  22  are driven using appropriate drive signals on paths  28 . 
         [0029]    Shaft  24  of vibrator motor  18  may have two exposed ends. A rotationally asymmetric weight may be formed on one or both ends of shaft  24 , so that vibrations are induced when shaft  24  is rotated about rotational axis  46  by vibrator motor  18 . 
         [0030]    To prevent damage to shaft  24  of vibrator motor  18  when device  10  is accidentally dropped, it may be desirable to support both of the opposing ends of shaft  24  and to form stop structures on each of the opposing ends. Any suitable mounting structure that supports both ends of shaft  34  may be used if desired (e.g., metal support structures, plastic support structures, bearings, parts of electronic device housing structures, etc.). As shown in  FIG. 3 , for example, vibrator motor mounting bracket  30  may have shaft support openings such as openings  32  in vertical end wall structures  38 . Openings  32  may receive shaft  24 . Each opening  32  may be used to support a respective end of shaft  24 . Openings  32  may be sized to receive shaft  24  directly or may be oversized to accommodate bearings (e.g., sleeve bearings or ball bearings that surround and support shaft  24 , etc.). 
         [0031]    Vertical wall structures  38  of bracket  30  may be mounted on horizontal bracket base structure  36 . Base structure  36  may be mounted within housing  12  using adhesive, screws, welds, or other fastening mechanism. An opening such as opening  34  may be formed in bracket base structure  36  to accommodate a rotating weight mounted on shaft  24 . 
         [0032]    A cross-sectional side view of a vibrator that includes a vibrator motor mounted in support structures such as mounting bracket  30  of  FIG. 3  is shown in  FIG. 4 . As shown in  FIG. 4 , vibrator  16  may have a weight such as weight  44  that is mounted on shaft  24 . As shaft  24  rotates around rotational axis  46 , weight  44  rotates about axis  46  and shaft  24 . An opening such as opening  34  may be provided in bracket  30  to allow weight  44  to rotate under shaft  24  without striking bracket  30 . This type of arrangement allows vibrator  16  to be implemented in a low-height configuration. If desired, the height of end wall members  36  can be increased to prevent weight  44  from striking portion  36  of bracket  30 . 
         [0033]    The rotation of weight  44  causes vibrator  16  to vibrate. Vibrations from vibrator  16  are conveyed to device  10  via mounting bracket  30 . Because both ends of shaft  24  are supported by bracket  30 , vibrations may be transmitted efficiently from vibrator  16  to housing  12  of device  10 . 
         [0034]    In the example of  FIG. 4 , optional bearings  40  have been inserted into holes  32 . Shaft  24  may be supported by bearings  40 . Bearings  40  may be sleeve bearings, ball bearings, or bearings of other types. Stop structures  42  have been formed on both ends of shaft  24  to prevent longitudinal movement of shaft  24  (i.e., to prevent movement of shaft  24  parallel to axis  46 ). Stop structures  42  may be press-fit members that are press fit over the ends of shaft  24  or may be members that are attached to shaft  24  using other suitable attachment mechanisms (e.g., welds, adhesive, screws, etc.). Stop structures  42  may also be formed by locally deforming portions of shaft  24 . Bearings  40 , bracket  30 , shaft  24 , and stop structures  42  may be formed from metal, plastic, or other materials. The support that is provided to both ends of shaft  24  by bracket  30  and the ability to resist axial movement that is provided by each of the associated stop structures  32  may help prevent damage to vibrator  16  in a drop event. If, for example, vibrator  16  were to be dropped on one of its shaft ends, the stop structure on the other end of the shaft would help dissipate some of the axial force generated by the impact, thereby helping to prevent damage. 
         [0035]    If desired, stop structures  42  may be formed by bending a portion of the end of shaft  24 . As shown in  FIG. 5 , for example, portions  24 ′ of shaft  24  may be flared outwards away from axis  46  to form stop structures  42 . 
         [0036]    In the illustrative arrangement of  FIG. 6A , the end of shaft  24  has been provided with circumferential groove  50  and mating c-ring  50 . When c-ring  50  is attached to shaft  24  in groove  48 , c-ring  50  forms stop structures  42 .  FIG. 6B  is a front view of c-ring  50 . 
         [0037]    As shown in the cross-sectional side view of shaft  24  in  FIG. 7 , stop structures  42  may be attached to the end of shaft  24  using attachment features  52 . Attachment features  52  may include adhesive, welds, solder, or other suitable attachment mechanisms. 
         [0038]      FIG. 8  is a cross-sectional side view of an illustrative configuration for shaft  24  showing how stop structures  42  may be formed by pressing inwardly on the end of shaft  24  in direction  54  to deform shaft  24 . The pressure on the end of shaft  24  flattens end portion  52  and creates protruding portions  24 ″ that serve as stop structures  42 . 
         [0039]    If desired, stop structures  42  may be formed on the ends of shaft  24   FIG. 9  before shaft  24  is mounted in bracket  30 . To accommodate this order of assembly, bracket  30  may be provided with a shape that allows bracket  30  to be crimped over the end of shaft  24  after stop structures  42  have been formed. As shown in  FIG. 9 , for example, bracket  30  may have upper bracket portion  30 - 1  and lower bracket portion  30 - 2 . Portion  30 - 1  may have an opening such as hemispherical opening  32 - 1 , whereas portion  30 - 2  may have an opening such as hemispherical opening  32 - 2 . Bracket  30  may initially have an open-jaw shape of the type shown in  FIG. 9 . After positioning shaft  24  as shown in  FIG. 9 , upper portion  30 - 1  may be bent downward in direction  56  so that portion  30 - 1  mates with portion  30 - 2 . In this configuration, hole portions  32 - 1  and  32 - 1  will form a circular hole (hole  32 ) that surrounds shaft  24 . Stop structures  42  on the ends of shaft  24  will then prevent longitudinal movement of shaft  24  along axis  46 . 
         [0040]    As shown in  FIG. 10 , mounting bracket  30  may have vertical portions that are located on opposing sides of a single stop member. In the  FIG. 10  example, mounting bracket  30  has three vertical structures (vertical structure  38 A, vertical structures  38 B, and vertical structure  38 C) mounted on a common base structure (base structure  36 ). Structure  38 C may be used to support the left-hand end of shaft  24 , but need not be provided with a stop structure. Stop structure  42  (e.g., a press-fit disk, a c-ring structure, deformed portions of shaft  24 , etc.) may be formed on shaft  24  near the right-hand end of shaft  24  and may be captured between opposing vertical structures  38 A and  38 C to prevent movement of shaft  24  along rotational axis  46 . 
         [0041]    In the  FIG. 10  example, the left-hand end of shaft  24  is supported by a single vertical bracket structure and the right-hand end of shaft  24  is supported using dual vertical bracket structures. If desired, both the left-hand and right-hand ends of shaft  24  may be supported by dual vertical bracket structures. The  FIG. 10  arrangement is merely illustrative. 
         [0042]    The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.