Patent Publication Number: US-2019170208-A1

Title: Voice coil actuator and sensing driver module

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an actuator and a sensing driver module, and more particularly to a voice coil actuator and a sensing driver module. 
     Description of the Prior Art 
     Usually, a vibration isolating system is widely used in all types of mechanical devices, and as the technology improves, the industry develops more and more dedicated and tiny devices. To keep the dedicated elements from influence of vibration during a processing process and from decreasing precision, a vibration isolating with more preferable vibration isolating effect is developed and manufactured. 
     In addition, since the semi-conductor manufacturing process advances toward the nano level, and the demand for floor vibration isolation becomes higher, traditional vibration isolation technology is gradually out of date. Therefore, many international advanced vibration isolation related companies start developing proactive vibration isolating technology so as to help the development of hi-tech nano equipment. A proactive vibration isolating system uses a vibration detecting device to catch a vibration signal so as to conduct a close loop feedback control, outputs an actuating signal to drive an actuating element so as to provide additional force to suppress the vibration, and further reach the goal of decreasing the amount of vibration and elevating the manufacturing yield. 
     A voice coil actuator has small volume, precise actuating movement and reasonable price, so the voice coil actuator has become the product which is used by the most companies among the other actuating elements in the proactive vibration isolation system. However, in one of the conventional voice coil actuator, a voice coil rotor and a voice coil main body are connected to each other via an elastic plate, because the elastic plate is more rigid, a rigidity of the whole proactive vibration isolating system also increases. Therefore, when the voice coil actuator is impacted by an overly great force (for example, an overly great vibration force), the voice coil may be damaged due to the elastic plate hitting a bottom portion of the voice coil. 
     Therefore, how to provide a voice coil actuator and a sensing driver module which can prevent the coil from damage due to great vibration has become an issue that the industry needs to work on. 
     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
     SUMMARY OF THE INVENTION 
     The major object of the present invention is to provide a voice coil actuator and a sensing driver module which can be adapted to a proactive vibration isolating system. The voice coil actuator and the sensing driver module can not only prevent a coil from being damaged due to a force which is too great but also lower a cost of the proactive vibration isolating system so as to increase a competitiveness of the product. 
     To achieve the above and other objects, a voice coil actuator is provided, including a main body, a cover body, a magnetic element, a rotor assembly and a coil. The cover body is connected to the body base to form a receiving space. The magnetic element is arranged within the receiving space. The rotor assembly is arranged within the receiving space, the rotor assembly has a rotor, a first elastic member and a pressing element, the rotor is arranged opposite to the magnetic element and has a hole and a first side, the pressing element is arranged in the hole and has a first end and a second end which is opposite to the first end, the first end is curved and protrudes beyond the hole, the first elastic element is arranged on the first side and has a third end and a fourth end which is opposite to the third end, the third end abuts against the magnetic element, and the fourth end is located within the hole and abuts against the second end. The coil is annularly arranged around a circumference of the magnetic element and connected to the rotor. 
     To achieve the above and other objects, a sensing driver module is provided, including a voice coil actuator and an accelerometer. The voice coil actuator includes a main body, a cover body, a magnetic element, a rotor assembly and a coil. The cover body is connected to the body base to form a receiving space. The magnetic element is arranged within the receiving space. The rotor assembly is arranged within the receiving space, the rotor assembly has a rotor, a first elastic member and a pressing element, the rotor is arranged opposite to the magnetic element and has a hole and a first side, the pressing element is arranged in the hole and has a first end and a second end which is opposite to the first end, the first end is curved and protrudes beyond the hole, the first elastic element is arranged on the first side and has a third end and a fourth end which is opposite to the third end, the third end abuts against the magnetic element, and the fourth end is located within the hole and abuts against the second end. The coil is annularly arranged around a circumference of the magnetic element and connected to the rotor. The accelerometer is tightly fitted into the voice coil actuator, and the accelerometer is for measuring an axial vibration and outputting a vibration signal; wherein the voice coil actuator controls the rotor assembly to move according to the vibration signal so as to counter the axial vibration. 
     In an embodiment, the voice coil actuator further includes a yoke and a positioning frame. The yoke is arranged within the receiving space and annularly arranged around the circumference of the magnetic element, and the coil is located between the magnetic element and the yoke. The positioning frame is connected to the cover body and the yoke, and the rotor assembly is located by an inner side of the positioning frame. 
     In addition, the voice coil actuator further includes a supporting element and a packing element. The supporting element is annularly arranged around a circumference of the rotor, and the supporting element is respectively connected to the rotor and the positioning frame. The packing element is arranged by an inner side of the positioning frame, and the supporting element is sandwiched between the positioning frame and the packing element. 
     In an embodiment, the rotor assembly further has a ball, a locking element and a second elastic element, at least one lateral side of the rotor has a through hole, the ball is arranged within the through hole and abuts against a groove on a side of the pressing element, the locking element is arranged within and tightly fitted into the through hole, and the second elastic element is arranged between the ball and the locking element. 
     In an embodiment, the accelerometer has a base, a mass block, at least three elastic element sets, a piezoelectric element and a first damping element, the base has a pressing portion on the axial direction, the mass block has a first side and a second side which is opposite to the first side, each of the at least three elastic element sets includes a first elastic element, a second elastic element and a prepressing adjusting element, the first elastic element is arranged on the first side of the mass block, the second elastic element is arranged on the second side of the mass block, the prepressing adjusting element is disposed through the first elastic element, the mass block and the second elastic element, the piezoelectric element is arranged between the mass block and the base, the piezoelectric element has a first side which is toward the pressing portion and a second side which is opposite to the first side, the first damping element is arranged on at least one of two sides of the piezoelectric element, and when the mass block moves on the axial direction, the pressing portion of the base make the piezoelectric element produce a deformation. 
     In an embodiment, a side of the body base has at least three protrusions and a recess, the accelerometer is tightly fitted into the recess, and the at least three protrusions are evenly arranged. 
     Given the above, in the voice coil actuator and the sensing driver module, the accelerometer is tightly fitted into the voice coil actuator; the cover body and the body base of the voice coil actuator are connected to each other to form the receiving space, the first end of the pressing element of the rotor assembly is curved and protrudes beyond the hole, the third end of the first elastic element abuts against the magnetic element, the fourth end of the first elastic element is located in the hole and abuts against the second end of the pressing element, the coil is annularly arranged around the circumference of the magnetic element and connected to the rotor; the accelerometer is for measuring the axial vibration and outputting the vibration signal, and the voice coil actuator can control the rotor assembly to move according to the vibration signal so as to counter the axial vibration. Through the above-mentioned structure, the voice coil actuator and the sensing driver module can prevent the coil from being damaged due to overly great force and lower the cost of the proactive vibration isolating system so as to increase the competitiveness of the product. 
     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment(s) in accordance with the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1C  are respectively assembly, breakdown and cross-sectional views of a sensing driver module of a preferred embodiment of the present invention; 
         FIGS. 2A to 2C  are respectively stereogram, cross-sectional and breakdown views of an accelerometer; and 
         FIGS. 3A to 3C  are respectively stereogram, cross-sectional and breakdown views of a voice coil actuator of the preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be clearer from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention. 
     Please refer to  FIGS. 1A to 1C  for respectively assembly, breakdown and cross-sectional views of a sensing driver module  1  of a preferred embodiment of the present invention. 
     The sensing driver module  1  can be adapted to a proactive vibration isolating system and includes an accelerometer  2  and a voice coil actuator  3 . The accelerometer  2  is for measuring an axial vibration and outputting a vibration signal, the proactive vibration isolating system can calculate and convert the vibration signal and provides the vibration signal converted to the voice coil actuator  3 , and the voice coil actuator  3  can output a counterforce according to the vibration signal to counter the axial vibration. In some embodiments, the proactive vibration isolating system may include a plurality of sets of sensing driver module  1 , the sensing driver modules  1  may be respectively assembled on X axis, Y axis and Z axis, the accelerometers  2  on at least three directions can respectively measure the accelerated velocities of the three axes, the at least three voice coil actuators  3  corresponded can output counter forces on the three axes to respectively counter vibrations on the three axes so as to suppress an object to be measured or an object to be isolated from vibration to decrease vibration. The sensing driver module  1  may also be used on monitoring an industrial production line, earthquake monitoring, measuring microvibration of floors of semi-conductor or optoelectronics factories or other vibration suppressions, but not limited thereto. 
     In the embodiment, the voice coil actuator  3  has a body base  30 , and the accelerometer  2  is tightly fitted into the voice coil actuator  3 . A side  30   a  of the body base  30  has at least three protrusions  301  and a recess  302 , and the accelerometer  2  is tightly fitted into the recess  302 ; that is, the accelerometer  2  is tightly placed in and connected to the recess  302 . In addition, to increase a connection strength, at least one connecting element S 1  (for example, a screw) is disposed through a hole of the body base  30  to be fixedly screwed with the accelerometer  2  to enhance the connection strength. Moreover, a number of the protrusions  301  is three, and the protrusions  301  are evenly arranged on the side  30   a  of the body base  30 . With the protrusions  301 , the accelerometer  2  can be easily assembled in the recess  302  of the voice coil actuator  3 , and the accelerometer  2  can be easily separated from the voice coil actuator  3 . 
     Please refer to related Figs. to see details of structures of the accelerometer  2  and the voice coil actuator  3 . 
     Please refer to  FIGS. 2A to 2C  respectively for stereogram, cross-sectional and breakdown views of the accelerometer  2 . 
     The accelerometer  2  of the present invention is design to measure a vibration in itself which is under ⅓ of the natural frequency, and under the circumstance that a rigid element is a copper sheet, a measurable range is preferably 1 Hz to 40 Hz. 
     The accelerometer  2  is for measuring the accelerated velocity of an axial direction. In other words, the accelerometer  2  is a uniaxial accelerometer, for example, the accelerometer arranged on the X-Y plane (horizontal plane) can measure an accelerated motion on Z direction (vertical direction). Of course, the accelerometer arranged on X-Z plane can measure accelerated motion on Y direction, and so on. 
     The accelerometer  2  includes a base  20 , a mass block  21 , at least three elastic element sets  22 , a piezoelectric element  23  and a first damping element  24 . The base  20  has a pressing portion  202  on the axial direction (Z direction), so a direction that the pressing portion  202  is arranged must be the same as an accelerated velocity direction that the accelerometer  2  wants to measure. Although the pressing portion  202  of the present invention is locked on the base  20  (the pressing portion  202  may be a top pin or a screw), in different embodiments, the pressing portion  202  and the base  20  may be integrally formed as long as the pressing portion  202  protrudes beyond a surface of the base  20  and abuts against a part of the piezoelectric element  23 . In addition, the pressing portion  202  may be in shapes of cylinder, rectangular prism or hexagonal prism, and the shapes are not limited to the shapes or arrangements of the Figs. of the embodiment. 
     For more detail of positions of the elements, the mass block  21  which is arranged above the base  20  has a first side  21   a  and a second side  21   b  which is opposite to the first side  21   a , and the first side  21   a  of the mass block  21  is neighboring to the base  20 . 
     Each of the at least three elastic element sets  22  includes a first elastic element  221 , a second elastic element  222  and a prepressing adjusting element  223 . The first elastic element  221  has first end  221   a  and a second end  221   b  which is opposite to the first end  221   a . The second elastic element  222  has a first end  222   a  and a second end  222   b  which is opposite to the first end  222   a . The first elastic element  221  is arranged on the first side  21   a  of the mass block  21 , the second elastic element  222  is arranged on the second side  21   b  of the mass block  21 . In addition, the prepressing adjusting element  223  is disposed through the first elastic element  221 , the mass block  21  and the second elastic element  222 . Each said prepressing adjusting element  223  corresponds to each said first elastic element  221  and each said elastic element  222  and sequentially through the mass block  21 , each said first elastic element  221  and each said elastic element  222  and the base  20 . With the arrangement of the first elastic element  221  and the second elastic element  222 , the base  20  and the mass block  21  can move simultaneously and coaxially and provide precise vibration signals. Through adjusting a distance between the prepressing adjusting element  223  and the base  20 , the mass block  21  presses the first elastic element  221  and each said elastic element  222  to make the first and second elastic elements of the elastic element set  22  to be prepressed so that a user can adjust a distance between the mass block  21  and the base  20  to abut the pressing portion  202  to a predetermined position. 
     In addition, the prepressing adjusting element  223  can also make the pressing portion  202  of the base  20  to prepress the piezoelectric element  23 . When the piezoelectric element  23  receives a preload force, the piezoelectric element  23  can be ensured to be pressed by a force during a measuring process (the piezoelectric element  23  and the pressing portion  202  will not be separated from each other and unable to measure vibration) to decrease error of measurement. It is to be noted that a prepressing depth may need to be adjusted according to difference materials or structures, if the prepressing depth is too small, the pressing portion  202  may be unable to contact the piezoelectric element  23  during the measuring process and unable to get correct measuring data; but if the prepressing depth is too great, the piezoelectric element  23  may undergo plastic deformation or be broken. In this embodiment, a prepressing distance between the pressing portion  202  and the piezoelectric comment  23  is, for example, 0.75 mm. 
     It is to be noted that in this embodiment, the three elastic element sets  22  have the same heights and are respectively, spacingly and evenly arranged, so the elastic element sets  22  can provide the mass block  21  with a force on a Z direction (vertical direction) (on the contrary, each of the three elastic element sets  22  receives a same weight from the mass block  21 ), and the mass block  21  and the base  20  are arranged in parallel. In other embodiments, a number of the elastic element sets may be adjusted as long as the mass block  21  receives a force evenly, and the mass block  21  and the base  20  can be arranged in parallel. 
     Aside from arrangement, in this embodiment, two ends of the elastic element sets  22  are flattened. In other words, two ends of each said first elastic element  221  and each said second elastic element  222  which respectively contact the mass block  21  and the base  20  are flattened so that the mass block  21  can be arranged parallel to the base  20 , and an overall measuring precision can be increased. Specifically, being flattened here means that the first and second elastic element  221 ,  222  are cut flat in accordance with surfaces of the mass block  21  and the base  20  to make the first and second elastic element  221 ,  222  to be perpendicular to the flattened part. In addition, when being free of force, the first elastic element  221  will make the mass block  21  in a state that resultant force is zero (the mass block  21  can levitate). In this embodiment, each of the first and second elastic elements  221 ,  222  is a spring, and the springs have the same length; but in other embodiments, each of the first and second elastic elements  221 ,  222  may also be an elastic piece or other elastic elements. 
     To cooperate with the at least three elastic element sets  22  mentioned above, in this embodiment, the accelerometer  2  may further include at least three fixing elements  251 , at least three first fixing seats  252 , at least three second fixing seats  253  and at least three third fixing seats  254  for the at least three elastic element sets  22  to be arranged therein. Here, three said fixing elements  251 , three said first fixing seats  252 , three said second fixing seats  253  and three said third fixing seats  254  are used to cooperate with three said elastic element sets  22 . 
     The first fixing seats  252  are provided on the second side  21   b  of the mass block  21 , the second fixing seats  253  are provided on the first side  21   a  of the mass block  21 , and the third fixing seats  254  are provided on a side of the base  20  facing the mass block  21 . In this embodiment, the first fixing seat  252 , the second fixing seat  253  and the third fixing seat  254  may be integrally formed with the mass block  21  or the base  20 , but in other embodiments, the first fixing seat  252 , the second fixing seat  253  and the third fixing seat  254  may also be independent from the mass block  21  or the base  20 . 
     Specifically, the first end  222   a  of the second elastic element is sleeved on the fixing element  251 , the first elastic element  221  is sandwiched between the second fixing seat  253  and the third fixing seat  254 , and the second elastic element  222  is sandwiched between the fixing element  251  and the first fixing seat  252 . In addition, the prepressing adjusting element  223  is disposed through the fixing element  251 , the second elastic element  222 , the first fixing seat  252 , the second fixing seat  253 , the first elastic element  221  and the third fixing seat  254 . 
     The fixing element  251 , the first fixing seat  252 , the second fixing seat  253  and the third fixing seat  254  are provided so that the elastic element sets  22  will deviate, during a process of measuring the accelerated velocity, the elastic element sets  22  will not be displaced or skewed, and the elastic element sets  22  can be prevented from swinging so as to ensure the measurement data to be more precise. 
     The piezoelectric element  23  is arranged between the mass block  21  and the base  20 . Specifically, the piezoelectric element  23  has a first side  23   a  and a second side  23   b  which is opposite to the first side  23   a , and the first side  23   a  of the piezoelectric element  23  is arranged relative to the pressing portion  202 . 
     The chart below shows the piezoelectric element  23  and other material parameters that could be used, but not limited thereto. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 Young&#39;s 
                   
               
               
                   
                 Density 
                 coefficient 
               
               
                   
                 (Kg/m 3 ) 
                 (N/m 2 ) 
                 Poisson&#39;s ratio 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 C3604 
                 8500 
                 9.7 × 10 10   
                 0.31 
               
               
                   
                 PZT-5H 
                 7700 
                 5.1 × 10 10   
                 0.31 
               
               
                   
                 PDMS4207 
                 980 
                 0.4 × 10 6    
                 0.5 
               
               
                   
                 SUS304 
                 8000 
                 19 × 10 10   
                 0.29 
               
               
                   
                 SCM435 
                 8000 
                 21 × 10 10   
                 0.3 
               
               
                   
                   
               
            
           
         
       
     
     In addition, the accelerometer  2  may further include a rigid element  26  (for example, a metal sheet), and the rigid element  26  is arranged on the second side  23   b  of the piezoelectric element  23 . The rigid element  26  is provided to increase a rigidity of the piezoelectric element  23 . For example, the rigid element  26  can be attached to one of two sides of the piezoelectric element  23  which is opposite to the other of the two sides that is pressed (the rigid element  26  can be attached to a negative pole of the piezoelectric element  23  via an epoxy resin) to increase the rigidity of the piezoelectric element  23  and to prevent the piezoelectric element  23  from being broken. The rigid element  26  is also provided to increase a rigidity of the mass block  21 . Therefore, when a supporting rigidity of the mass block  21  increases, the overall natural frequency of the accelerometer  2  will also increase so that a bandwidth that the accelerometer  2  can measure will be greater. In addition, the accelerometer  2  can adjust the overall natural frequency through increasing a thickness or a number of the rigid element  26 . 
     More specifically, this embodiment takes a piezoelectric element  23  and a rigid element  26  as an example, but the user can pile up a piezoelectric element  23  and different numbers of rigid elements in accordance to different requirements to achieve various measuring goals. The chart below is a possible example of an examination, and “thickness” in the chart is the thickness that the rigid element  26  and the piezoelectric element  23  are piled up. In addition, the rigid element  26  in the chart is a thin copper sheet. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 One rigid element 
                 Two rigid 
                 Three rigid 
               
               
                   
                 with one 
                 elements with one 
                 elements with one 
               
               
                   
                 piezoelectric 
                 piezoelectric 
                 piezoelectric 
               
               
                   
                 element 
                 element 
                 element 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Thickness 
                 0.43 
                 mm 
                 0.74 
                 mm 
                 0.95 
                 mm 
               
               
                 Natural 
                 170.5 
                 Hz 
                 299.5 
                 Hz 
                 385.5 
                 Hz 
               
               
                 frequency 
               
               
                 Sensitivity 
                 82.5 
                 V/g 
                 56.5 
                 V/g 
                 36.8 
                 V/g 
               
               
                 (±10%) 
               
               
                 Bandwidth 
                 2~52 
                 Hz 
                 2~96 
                 Hz 
                 1~153 
                 Hz 
               
               
                 (±10%) 
               
               
                 Bandwidth 
                 0.75-92 
                 Hz 
                 0.75-169 
                 Hz 
                 0.25-237 
                 Hz 
               
               
                 (±3 dB) 
               
               
                   
               
            
           
         
       
     
     The first damping element  24  is attached on the first side  23   a  of the piezoelectric element  23 . In other words, in this embodiment, the first damping element  24  is arranged between the mass block  21  and the base  20  and on the first side  23   a  of the piezoelectric element  23 . Specifically, the first damping element  24  is arranged between the piezoelectric element  23  and the pressing portion  202  of the base  20 . The first damping element  24  may be made of rubber, silica gel, elastopolymer or other compounds, but not limited thereto. In actual practice, the material of which the first damping element  24  is made can be adjusted according to different requirements. The first damping element  24  can not only adjust a damping coefficient of the accelerometer  2  but also increase a damping coefficient of the whole invention to make the frequency that responses to be flatter, so the measurable bandwidth range becomes wider. In addition, the first damping element  24  may also function as the pressing portion  202  which isolates the base  20  to prevent the base  20  from contacting the piezoelectric element  23  so as to prevent the piezoelectric element  23  from short-circuit or damage. 
     In different embodiments, the first damping element  24  and the rigid element  26  may also be arranged on the second side  23   b  of the piezoelectric element  23  (not shown). Specifically, the first damping element  24  may be arranged above the rigid element  26  (that is, the rigid element  26  is arranged between the first damping element  24  and the piezoelectric element  23 ) to counter a resonance of the rigid element  26 . If the first damping element  24  is arranged on the first side  23   a  of the piezoelectric element  23 , the resonance of the rigid element  26  can be countered. Although both the two arrangement ways mentioned above influence the sensitivity of the accelerometer, the bandwidth that is measurable increases. Therefore, preferably, the user needs to choose an appropriate damping parameter (that is, to choose the first damping element  24  with appropriate width or hardness) so as to reach the bandwidth and bandwidth s/he wants. 
     In addition, in this embodiment, the accelerometer  2  further includes a second damping element  24   a , and the second damping element  24   a  is arranged on one of two sides of the rigid element  26  opposite to the piezoelectric element  23 . The first damping element  24  is arranged between the piezoelectric element  23  and the pressing portion  202 , and the second damping element  24   a  is arranged on the second side  26   b  of the rigid element  26 . In other words, in this embodiment, each of the two sides of the rigid element is provided with a damping element  24 ,  24   a.    
     Therefore, this embodiment has a simple structure (less elements) and is easy to be assembled, so the accelerometer  2  has lower cost. Besides, during the actual process of operating the accelerometer  2 , when the mass block  21  moves on the axial direction due to vibration, the pressing portion  202  of the base  20  makes the piezoelectric element  23  produce a deformation. Then, the accelerometer  2  converts the deformation to an electric signal (or an electric charge signal or a vibration signal) and transmits the electric signal to the vibration isolating system that the accelerometer  2  cooperates with, after the electric signal is calculated and converted and then provided to the voice coil actuator  3 , and the voice coil actuator  3  can output a counterforce according to the vibration signal to counter the vibration of the axial direction. 
     Please refer to  FIGS. 3A to 3C  for stereogram, cross-sectional and breakdown views of the voice coil actuator  3  of an preferred embodiment. 
     In this embodiment, the voice coil actuator  3  has a body base  30 , and the accelerometer  2  is tightly fitted into the voice coil actuator  3 . A side  30   a  of the body base  30  has at least three protrusions  301  and a recess  302 , and the accelerometer  2  is tightly fitted into the recess  302 . In addition, to increase the connection strength, at least one connecting element S 1  (for example, a screw) is further disposed through a hole of the body base  30  to be fixedly screwed with the accelerometer  2 . In this embodiment, a number of the protrusions is three, and the protrusions are evenly arranged on the side  30   a  of the body base  30 . Through the protrusions  301 , the accelerometer  2  can be easily assembled in the recess  302  of the voice coil actuator  3  to make the accelerometer  2  separate from the voice coil actuator  3  easily. More specifically, the voice coil actuator  3  further includes a cover body  31 , a magnetic element  32 , a yoke  33 , a positioning frame  34 , a rotor assembly  35  and a coil  36 . In this embodiment, the voice coil actuator  3  further includes a supporting element  37  and a packing element  38 . The body base  30 , the cover body  31 , the positioning frame  34 , the rotor assembly  35  and the packing element  38  may be made of metals (for example, stainless steel) to elevate the overall structural strength. 
     As shown in  FIG. 3B , the cover body  31  is connected to the body base  30  to form a receiving space (not marked in  FIG. 3B ). In this embodiment, lateral sides of the cover body  30  and the body base  31  respectively correspond to at least one piercing hole (not marked in  FIG. 3B ), and at least one connecting element S 2  (for example, a screw) is disposed through the at least one piercing hole to fixedly screw the cover body  31  and the body base  30  correspondingly to make the cover body  31  and the body base  30  connected to each other. In this embodiment, a number of the connecting element is two, but the number of the connecting element can be adjusted as long as the cover body  31  and the body base  30  can be tightly connected to each other. 
     The magnetic element  32  and the yoke  33  are both arranged within the receiving space, and the coil  36  is located between the magnetic element  32  and the yoke  33  (the coil  36  does not contact the magnetic element  32  and the yoke  33  directly). As shown in  FIG. 3C , the magnetic element is a cylindrical permanent magnet, the yoke  33  is made of a magnetic material, and the yoke  33  is annularly arranged around a circumference of the magnetic element  32  (that is, the magnetic element  32  is located in an inner ring of the yoke  33 ) so as to guide and change magnetic orientations of the coil  36  and the magnetic element  32 . 
     The positioning frame  34  is connected to the cover body  31  and the yoke  33 , and the rotor assembly  35  is located by an inner side of the positioning frame  34 . The yoke  33  and the magnetic element  32  are located the receiving space which is formed by the body base  30 , the cover body  31  and the positioning frame  34 , the positioning frame  34  positions the coil  36  to keep a gap between the magnetic element  32  and the coil  36 , and the coil  36  and the yoke  33  also have a gap therebetween to prevent the coil from contacting the yoke  33  and the magnetic element  32  directly. 
     The rotor assembly  35  is arranged within the receiving space. In this embodiment, the rotor assembly  35  includes a rotor  351 , a first elastic member  352  and a pressing element  353 , and the rotor  351 , the first elastic element  352  and the pressing element  353  are located by an inner side of the positioning frame  34 . In this embodiment, the rotor assembly  35  may further include a ball  354 , a locking element  355  and a second elastic element  356 . 
     The rotor  351  is arranged opposite to the magnetic element  32 . Being opposite means that the rotor  351  and the magnetic element  32  have similar shapes (both are cylindrical) and are arranged face-to-face. The rotor  351  has a hole H (not shown in  FIGS. 3A and 3B ), a first side  351   a  and a second side  351   b . The first side  351   a  is a side of the rotor  351  facing the magnetic element  32 , and the second side  351   b  is an opposite side of the first side  351   a.    
     The pressing element  353  is arranged in the hole H and has a first end  353   a  and a second end  353   b  which is opposite to the first end  353   a  (not shown in  FIGS. 3A and 3B ), and the first end  353   a  is curved and protrudes beyond the hole H. The pressing element  353  may be a top rail (or a top pin), the first end  353  a is curved so that the pressing element  353  point contacts with an object, and when the pressing element  353  contacts the object, if the first end  353   a  contacts the object in other angles other than 90 degrees, the coil  36  can prevent from being skewed (deviated from the direction of Z-axis). 
     The first elastic element  352  is arranged on the first side  351   a  of the rotor  351  and has a third end  352   a  and a fourth end  352   b  which is opposite to the third end  352   a  (not shown in  FIGS. 3A and 3B ). The third end  352   a  abuts against the magnetic element  32 , and the fourth end  352   b  is located within the hole H and abuts against and connected to the second end  353   b  of the pressing element  353 . The first elastic element  352  is for providing an elasticity so that when a vertical force exerted on the pressing element  353  disappears, the pressing element  353  can push outward to return the rotor assembly  35  back to an original state. 
     The coil  36  is annularly arranged on the circumference of the magnetic element  32  and connected to the rotor assembly  35 . In this embodiment, the coil  36  surrounds an circumference of a fixing ring  361  (for example, a copper ring) and is connected to the rotor  351  via the fixing ring  361 . Specifically, to reinforce a connection strength of the coil  36  and the rotor  351 , in this embodiment, the rotor  351  and an inner ring of the fixing ring  361  are glued to each other with an adhesive. Therefore, when the rotor  351  moves, the fixing ring  361  and the coil  36  are driven to move; and when the fixing ring  361  and the coil  36  move, the rotor  351  is also driven to move. 
     In addition, in this embodiment, at least one lateral side of the rotor  351  has a through hole h (not shown in  FIGS. 3A and 3B ), and the ball  354  is arranged within the through hole h and abuts against a groove on a side of the pressing element  353  (because the Figs. are too complicated, the groove in  FIG. 3B  is not numbered). The ball  354  may be a steel ball, and through engaging the ball  354  into the groove on the lateral side of the pressing element  353 , a connection strength of the rotor  351  and the pressing element  353  can be increased. Specifically, the locking element  355  is arranged within and tightly fitted into the through hole h. The locking element  355  is a screw, and the through hole h has a threaded portion correspond to the screw so that the locking element  355  can be screwed within the through hole h and tightly connected to the through hole h. More specifically, the second elastic element  356  is arranged between the ball  354  and the locking element  355 , one of two ends of the second elastic element  356  abuts against the ball  354 , the other of the two ends of the second elastic element  356  abuts against the locking element  355 . Therefore, through lateral forces that the locking element  355  and the second elastic element  356  exert on the ball  354 , relative positions of the rotor  351  and the pressing element  353  can be fixed. 
     The supporting element  37  may be a rubber ring which is elastic, and the supporting element  37  is annularly arranged around a circumference of the rotor  351  and respectively connected to the rotor  351  and the positioning frame  34  to provide a buffer effect when the rotor assembly  35  moves. In this embodiment, to reinforce the connection strength of the supporting element  37  and the rotor  351 , an inner ring of the supporting element  37  is engaged in an outer ring of the rotor  351 , and the supporting element  37  and the rotor  351  are glued to each other via an adhesive so that the supporting element  37  is fixed between the rotor  351  and the positioning frame  34  to provide a buffer effect. In addition, the packing element  38  is arranged on an inner side of the positioning frame  34 , and the supporting element  37  is sandwiched between the positioning frame  34  and the packing element  38 . The packing element  38  is a packing ring and arranged on the inner side of the positioning frame  34  so that the packing element  38  and the positioning frame  34  can clamp the outer ring of the supporting element  37 , and the supporting element  37  can fix relative positions of the rotor  351  and the coil  36  and relative positions of the rotor  351  and the positioning frame  34 . 
     As shown in  FIG. 3B , through lateral forces from the locking element  355 , the second elastic element  356  and the ball  354 , the relative positions of the rotor  351  and the pressing element  353  can be fixed. Therefore, when a vertical force (on Z-axis) that the pressing element  353  receives is greater than a critical force that the voice coil actuator  3  can endure, the rotor assembly  35  can retract toward the magnetic element  32  via the first elastic element  352  to prevent the coil  36  from hitting the magnetic element  32  or the yoke  33  when the rotor  353  retracts and drives the coil  36  to move. 
     In addition, when the accelerometer  2  detects the axial vibration and outputs the vibration signal, the proactive vibration isolating system can calculate and convert the vibration signal and provides the vibration signal converted to the voice coil actuator  3 , and the voice coil actuator  3  can control the rotor assembly  35  (or the rotor  351 ) to move according to the vibration signal so as to output the counterforce to counter the axial vibration. Therefore, when the voice coil actuator  3  outputs the counterforce according to the vibration signal to counter the axial vibration (for example, Z-axis), the magnetic element  32  and the coil  36  move relative to each other due to interactivity of the magnetic force. Since the magnetic element  32  is fixed on the yoke  33 , the coil (and the fixing ring  361 ) will move up and down (to balance the vibration of Z-axis) so as to drive the rotor  351  to move up and down to counter the axial vibration. 
     It is to be noted that if the voice coil actuator  3  is used to counter the vibration on Z-axis, the rotor  351  is less like to tilt laterally because the rotor  351  is put on a horizontal direction (for example, on X-Y plane). However, when a user wants to balance the vibration from the horizontal direction, the rotor  351  should be put straight. Therefore, when the rotor  351  is free from force, the rotor  351  cannot tilt, or the rotor  351  may tilt laterally; and when the rotor  351  moves to counter the vibration, there may be error, and the precision of the proactive vibration isolating system may also be influenced. Through computational simulation, a center of gravity of the rotor  351  is precisely designed and controlled to solve the problem that the rotor  351  tilts laterally. 
     Given the above, in the voice coil actuator and the sensing driver module, the accelerometer is tightly fitted into the voice coil actuator. The cover body of the voice coil actuator is connected to the body base to form a receiving space, the first end of the pressing element of the rotor assembly is curved and protrudes beyond the hole, the third end of the first elastic element abuts against the magnetic element, the fourth end of the first elastic element is located in the hole and abuts against the second end of the pressing element, and the coil is annularly arranged around the circumference of the magnetic element and connected to the rotor. In addition, the accelerometer is used to detect an axial vibration and outputs a vibration signal, and the voice coil actuator can control the rotor assembly to move according to the vibration signal to counter the axial vibration. Through the above-mentioned structure, the voice coil actuator and the sensing driver module can not only prevent the coil from being damaged due to a force which is too great but also lower a cost of the proactive vibration isolating system so as to increase a competitiveness of the product. 
     While we have shown and described various embodiments in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.