Abstract:
A trackball module structure is provided. In the structure, a Hall IC is integrated in a flexible printed circuit, and the integrated structure and a trackball device are disposed on the base to be located. Afterwards, a lid is used to fix the integrated structure and the trackball device to form a module. The module is easy to be disposed on an electronic device. This not only solves the problem that the conventional trackball is hard to locate, but also prevents the ESD with the cooperation of a metal base and a metal lid.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a trackball module structure adapted to an electronic device and, more particularly, to a trackball module structure in which a trackball device and a control chipset are integrated to be a single module. 
     2. Description of the Related Art 
     Generally, a trackball is disposed on an electronic device to move a cursor. Especially to a portable electronic device such as a personal digital assistant, the trackball may facilitate the operation of a user. As shown in  FIG. 1 , it is a schematic diagram showing a conventional trackball. A trackball device  70  is formed by a ball  71 , four magnetic rollers  73  and a casing  72  covering them. Afterwards, the trackball device  70  is disposed on the motherboard  75  of the electronic device. The motherboard  75  has four Hall ICs  74  corresponding to the magnetic rollers  73 . 
     Thus, when the user rolls the ball  71 , the magnetic rollers  73  rotate along with the rotation of the ball  71 . Then, the Hall ICs  74  sense the magnetism change of the magnetic rollers  73  to make the cursor move according to the calculation of the electronic device. Thus, the relationship of the magnetic rollers  73  and the Hall ICs  74  may determine the sensing precision of the trackball. 
     However, to facilitate the operation of the user, the trackball device  70  should be fixed at the casing of the electronic device (not shown). The Hall ICs  74  are welded on the motherboard  75 . Since manufacturing tolerance and assembling tolerance may exist between the trackball device  70  and the casing, the casing and the motherboard  75  and the motherboard  75  and the Hall ICs  74 , the tolerance is accumulated, and the tolerance between the magnetic rollers  73  and the Hall ICs  74  may be large and is hard to be controlled. This not only affects the precision of the trackball, but also may affect the sensing ability and the operation of the user. 
     In the conventional technology, a reed switch is used to replace the Hall IC to reduce the cost and improve the reliability. However, since the assembly mode of the reed switch and the trackball device is not changed, the problem that the tolerance accumulates still exists. Once the sensing ability is not good, even if the manufacturing cost is reduced, the reliability cannot be improved. 
     BRIEF SUMMARY OF THE INVENTION 
     The trackball module structure according to the invention includes a base, a flexible printed circuit, a trackball device and a lid. The base has a recess to dispose the flexible printed circuit, and the flexible printed circuit has a carrying portion and a connecting portion which are connected to each other. The carrying portion has a control chipset which is disposed in the recess of the base through the carrying portion. The connecting portion extends out of the recess, and it may be electrically connected to the circuit board of the electronic device. Then, the trackball device is disposed in the recess of the base corresponding to the control chipset and is fixed by the lid. Thus, the trackball device and the control chipset are modularized via the base. After located, the module is connected to the electronic device by the connecting portion of the flexible printed circuit. Thus, the conventional problem that the sensing ability is not good due to the difficult location of the trackball device and the control chipset is solved. 
     In another aspect, the base and the lid may be made of metal, and thus the problem of the electrostatic discharge (ESD) is solved. 
     These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing that a conventional trackball is connected to an electronic device; 
         FIG. 2  is a schematic diagram showing a trackball module structure in an embodiment of the invention; 
         FIG. 3A  to  FIG. 3C  are schematic diagrams showing the assembly of the trackball module structure in an embodiment of the invention; and 
         FIG. 4  is a schematic diagram showing the trackball module structure in another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     As shown in  FIG. 2 , according to the trackball module structure disclosed in the invention, it is a schematic diagram showing the trackball module structure in an embodiment of the invention. The trackball module structure includes a base  10 , a flexible printed circuit  20 , a trackball device  30  and a lid  40 . The base  10  includes a recess  11 . The recess  11  has a lateral opening for disposing the flexible printed circuit and the trackball device  30 . The flexible printed circuit  20  has a connecting portion  22  and a carrying portion  21  which are connected to each other. The carrying portion  21  has a control chipset which is composed of four Hall ICs  24  and a push switch  23 . The Hall ICs  24  may sense the rotation of the ball  31  of the trackball device  30 . The push switch  23  is used to receive the motion of pressing the ball  31 . 
     The trackball device  30  includes a ball  31  and four magnetic rollers  32 . They are disposed in a frame  33 . When the ball  31  rotates, it drives the magnetic rollers  32  to rotate. With the change of the magnetism of the magnetic rollers  32  and the sense of the Hall ICs  24 , the moving distance is determined. The lid  40  has an opening  41 , and the opening  41  corresponds to the ball  31  of the trackball device  30  to locate and expose the ball  31 . 
     As shown in  FIG. 3A  to  FIG. 3C , they are schematic diagrams showing the assembly of the trackball module structure in an embodiment of the invention. 
     As shown in  FIG. 3A , the flexible printed circuit  20  is disposed in the recess  11  of the base  10 . The flexible printed circuit  20  has multiple locating holes  25 . Cooperating with the recess  11  of the base  10  and multiple locating pillars  12  at the edge of the recess  11 , the locating pillars  12  pass through the locating holes  25 , and thus the flexible printed circuit  20  is fixed and located in the recess  11  of the base  10 . The locating mode is not limited to use the locating pillars  12  and the locating holes  25 . If the size of the carrying portion  21  of the flexible printed circuit  20  is as large as that of the recess  11  of the base  10 , the locating effect also may be achieved. In another aspect, if the flexible printed circuit  20  needs to be fixed on the base  10  stably, glue also may be used to stick the flexible printed circuit  20  in the recess  11  of the base  10 . 
     As shown in  FIG. 3B , after the flexible printed circuit  20  is located and fixed, the trackball device  30  is disposed in the recess  11  of the base  10  corresponding to the control chipset of the flexible printed circuit  20 . In other words, the bottom of the ball  31  of the trackball device  30  corresponds to a push switch  23  of the flexible printed circuit  20 . The magnetic rollers  32  of the trackball device  30  correspond to the Hall ICs  24  of the flexible printed circuit  20 . Thus, when the ball  31  is pressed, the push switch  23  is triggered, and when the ball  31  drives the magnetic rollers  32  to rotate, the Hall ICs  24  sense the rotation and output the corresponding signal. 
     At last, as shown in  FIG. 3C , the lid  40  is connected in the recess  11  of the base  10 . The opening  41  of the lid  40  corresponds to the ball  31  of the trackball device  30 . Thus, the ball  31  is located and exposed. The lid  40  has slots  42  at both sides, and hooks  13  are disposed in the inner sides of the recess  11  of the base  10 . With the cooperation of the slots  42  and hooks  13 , the lid  40  is fixed at the position. A screw  50  also may be used to pass the fixing hole  43  of the lid  40  and the fixing hole  26  of the flexible printed circuit  20  to be locked in the screw hole  13  of the base  10 . This makes the module more stable. In the invention, the trackball module structure is fixed in the electronic device, and only the connecting portion  22  is electrically connected to the motherboard of the electronic device (not shown). This may improve the locating effect. 
     The trackball device  30  now is a mature element, and the sensing method using magnetic rollers  32  and the Hall ICs  24  is only one of the aspects. Trackball devices  30  using other sensing elements also may be adapted to the invention. Since the trackball device  30  is different from the conventional structure, that is, the trackball device  30  is held and sandwiched by the base  10  and the lid  40 , and the base  10  and the lid  40  are made of metal, this may prevent the electrostatic discharge (ESD) effectively. 
     In another aspect, as shown in  FIG. 4 , it is a schematic diagram showing the trackball module structure in another embodiment of the invention. 
     To make it convenient to fix the structure at the electronic device, extending portions  15  extend from the two sides of the base  10 , and the extending portion  15  has a fixing hole  16  to be fixed at the electronic device (not shown). The flexible printed circuit  20  may have a keypad circuit board  27  having multiple keypad connectors  28  to allow the electronic device to be used directly. Thus, the function of the trackball module structure is more complete. The extending portion  15  is not limited to be the aspect in the drawings, and the flexible printed circuit  20  also may have additional functions or provide different keypad connectors  28 . 
     According to the trackball module structure in the invention, the trackball device and the control chipset are modularized using the base and the lid, and the whole module may be disposed on the electronic device. Thus, the disadvantages that tolerance may generate and accumulate and the sensing ability are not good when the trackball device is disposed at the casing and the control chipset is disposed at the motherboard is overcome. In addition, the base and the lid are made of material, and this may prevent the ESD. 
     Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, the disclosure is not for limiting the scope of the invention. Persons having ordinary skill in the art may make various modifications and changes without departing from the scope and spirit of the invention. Therefore, the scope of the appended claims should not be limited to the description of the preferred embodiments described above.