Patent Abstract:
A multifunction acoustic device has a rotor rotatably supported in a frame, a stator provided in the frame. A permanent magnet is provided on the rotor, a coil is provided for forming magnetic fluxes between the rotor and the stator. Voltage detecting means is provided for detecting a voltage generating at the coil. A voltage detected by the voltage detecting means in the operation of the acoustic device is compared with a reference voltage which corresponds to a voltage generating at abnormal rotation of the rotor and for producing an abnormal signal when the detected voltage is equal or higher than the reference voltage. In response to the abnormal signal, the rotor is rotated from a low speed.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a multifunction acoustic device used in a portable instrument such as a portable telephone.  
           [0002]    There has been provided an acoustic device of the portable instrument in which a speaker is provided for generating sounds of calling signals, and a vibrating motor is provided for informing the receiver of calling signals without generating sounds. In such a device, since both of the speaker and the motor are mounted in the device, the device is increased in size and weight, and in manufacturing cost.  
           [0003]    In recent years, there is provided a multifunction acoustic device in order to remove the above described disadvantages. The multifunction acoustic device comprises a speaker having a vibrating plate and a permanent magnet magnetically connected to a voice coil mounted on the vibrating plate of the speaker. The permanent magnet is independently vibrated at a low frequency of 100-150 Hz so as to inform the receiving of calling signals by the vibration of the case of the device, which is transmitted to the body of the user of the device.  
           [0004]    [0004]FIG. 9 is a sectional view of a conventional electromagnetic induction converter disclosed in Japanese Utility Model Application Laid Open 5-85192. The converter comprises a diaphragm  506  mounted in a case  512  at a periphery thereof, a voice coil  508  secured to the underside of a central portion  507  of the diaphragm  506 , a spring plate  511  mounted in the case  512 , and a permanent magnet  510  secured to a central portion of the spring plate  511 , inserted in the voice coil  508 .  
           [0005]    By applying a low or high frequency signal to the voice coil  508 , the spring plate  511  is vibrated in the polarity direction Y of the magnet  510 .  
           [0006]    In the device, the diaphragm  506  and the spring plate  511  are relatively moved through the magnetic combination between the voice coil  508  and the magnet  510 . Consequently, when a low frequency signal or a high frequency signal is applied to the voice coil  508 , both of the diaphragm  506  and the spring plate  511  are sequentially vibrated. As a result, sounds such as voice, music and others generated from the device are distorted, thereby reducing the quality of the sound. In addition, vibrating both of the voice coil  508  and the magnet  510  causes the low frequency vibration of the magnet to superimpose on the magnetic combination of the voice coil  508  and the magnet  510 , which further largely distorts the sounds.  
           [0007]    [0007]FIG. 10 is a sectional view showing a conventional multifunction acoustic device. The device comprises a speaker vibrating plate  603  made of plastic and having a corrugated periphery  603   a  and a central dome, a voice coil  604  secured to the underside of the vibrating plate  603  at a central portion, and a magnet composition  610 . The vibrating plate  603  is secured to a frame  609  with adhesives.  
           [0008]    The magnetic composition  610  comprises a lower yoke  605 , a core  601  formed on the yoke  605  at a central portion thereof, an annular permanent magnet  602  mounted on the lower yoke  605 , and an annular upper yoke  606  mounted on the permanent magnet  602 . The lower yoke  605  and the upper yoke  606  are resiliently supported in the frame  609  by spring plates  607  and  608 . A magnetic gap  611  is formed between a periphery  601   a  of the core  601  and an inside wall  606   a  of the upper yoke  606  to be magnetically connected to the voice coil  604 .  
           [0009]    When an alternating voltage is applied to the voice coil  604  through input terminals  612   a  and  612   b,  the speaker vibrating plate  603  is vibrated in the direction Y to generate sounds at a frequency between 700 Hz and 5 KHz. If a low frequency signal or a high frequency signal is applied to the voice coil  604 , the speaker vibrating plate  603  and the magnetic composition  610  are sequentially vibrated, since the magnetic composition  610  and the speaker vibrating plate  603  are relatively moved through the magnetic combination of the voice coil  604  and the magnet composition  610 .  
           [0010]    As a result, sounds such as voice, music and others generated from the device are distorted, thereby reducing the quality of the sound. In addition, the driving of both the voice coil  604  and the magnetic composition  610  causes the low frequency vibration to superimpose on the magnetic combination of the voice coil  604  and the magnetic composition  610 , which further largely distorts the sounds.  
           [0011]    [0011]FIG. 11 is a sectional view showing another conventional multifunction acoustic device. The device comprises the speaker vibrating plate  603  made of plastic and having the corrugated periphery  603   a  and the central dome, the voice coil  604  secured to the underside of the vibrating plate  603  at a central portion, and the magnet composition  610 . The vibrating plate  603  is secured to the frame  609  with adhesives.  
           [0012]    The magnetic composition  610  comprises a lower yoke  703 , core  601  formed on the yoke  703  at a central portion thereof, an annular permanent magnet  702  secured to the lower yoke  703 , and annular upper yoke  606  having a peripheral wall  606   b  and mounted on the permanent magnet  702 . The upper yoke  606  is resiliently supported in the frame  609  by spring plates  707  and  708 . A first magnetic gap  701  is formed between the periphery  601   a  of the core  601  and the inside wall  606   a  of the upper yoke  606  to be magnetically connected to the voice coil  604 . A second gap  705  is formed between a periphery  703   a  of the lower yoke  703  and inside wall  606   a  of the upper yoke  606 . A driving coil  706  is secured to the frame and inserted in the second gap  705 .  
           [0013]    When an alternating voltage is applied to the voice coil  604  through input terminals  612   a  and  612   b,  the speaker vibrating plate  603  is vibrated in the direction Y to generate sounds at a frequency between 700 Hz and 5 KHz. If a low frequency signal or a high frequency signal is applied to the voice coil  604 , the speaker vibrating plate  603  and the magnetic composition  610  are sequentially vibrated, since the magnetic composition  610  and the speaker vibrating plate  603  are relatively moved through the magnetic combination of the voice coil  604  and the magnet composition  610 .  
           [0014]    When a high frequency signal for music is applied to the voice coil  604 , only the speaker vibrating plate  603  is vibrated. Therefore, there does not occur distortion of the sound. Furthermore, when a low frequency signal is applied to the driving coil  706 , only the magnetic composition  610  is vibrated, and the speaker vibrating plate  603  is not vibrated.  
           [0015]    However if a high frequency signal is applied to input terminals  612   a,    612   b,  and a low frequency signal is also applied to input terminals  704   a,    704   b,  the speaker vibrating plate  603  and magnetic composition  610  are sequentially vibrated, thereby reducing the sound quality.  
           [0016]    In the above described conventional devices, both the speaker vibration plate and the magnetic composition are vibrated when a low frequency signal or a high frequency signal is applied to the voice coil. This is caused by the reason that the low frequency vibrating composition is vibrated in the same direction as the high frequency vibrating direction.  
         SUMMARY OF THE INVENTION  
         [0017]    An object of the present invention is to provide a trouble shooting for the multifunction acoustic device which may deal with trouble such as the stopping of a rotor by shock applied to the device.  
           [0018]    According to the present invention, there is provided a multifunction acoustic device comprising a frame, a rotor rotatably supported in the frame, a stator provided in the frame, a permanent magnet provided on the rotor, a diaphragm supported in the frame, a coil for forming magnetic fluxes between the rotor and the stator, voltage detecting means for detecting a voltage generating at the coil, comparing means for comparing a voltage detected by the voltage detecting means in the operation of the acoustic device with a reference voltage which corresponds to a voltage generating at abnormal rotation of the rotor and for producing an abnormal signal when the detected voltage is equal to or higher than the reference voltage, speed control means responsive to the abnormal signal for starting to rotate the rotor from a low speed.  
           [0019]    The reference voltage is a voltage which corresponds to a voltage when the rotor starts to rotate at a low speed.  
           [0020]    The abnormal rotation is the stopping of the rotation of the rotor.  
           [0021]    The speed control means sets the speed of the rotor at the starting of the rotation and at a constant speed during the sound generating condition.  
           [0022]    These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0023]    [0023]FIG. 1 is a sectional view of a multifunction acoustic device of the present invention;  
         [0024]    [0024]FIG. 2 is a sectional view taken along a line II-II of FIG. 1;  
         [0025]    [0025]FIG. 3 is an exploded perspective view of a rotor of the multifunction acoustic device of the present invention;  
         [0026]    [0026]FIG. 4 is an exploded perspective view of a stator of the multifunction acoustic device of the present invention;  
         [0027]    [0027]FIG. 5 is a driving circuit used in the multifunction acoustic device of the present invention;  
         [0028]    [0028]FIG. 6 shows a block diagram of a trouble shooting system;  
         [0029]    [0029]FIG. 7 shows the system flowchart of the present invention;  
         [0030]    [0030]FIG. 8 is a graph showing characteristics of the system;  
         [0031]    [0031]FIG. 9 is a sectional view of a conventional electromagnetic induction converter;  
         [0032]    [0032]FIG. 10 is a sectional view showing a conventional multifunction acoustic device; and  
         [0033]    [0033]FIG. 11 is a sectional view showing another conventional multifunction acoustic device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    Referring to FIGS. 1 and 2, the multifunction acoustic device of the present invention comprises a sound generating device  10 , a rotor  20  and an annular stator  30  provided in a cylindrical frame  1  made of plastic. The sound generating device  10  comprises a speaker diaphragm  14  having a central dome  14   a  and secured to the frame at a periphery  14   b  with adhesives, a voice coil  15  secured to the underside of the speaker diaphragm  14 . The speaker diaphragm  14  is covered by a cover  13  having a plurality of sound discharge holes and secured to the frame  1  at a peripheral edge thereof.  
         [0035]    The rotor  20  comprises a lower rotor yoke  23  secured to a rotor shaft  16  rotatably mounted on a base plate of the frame  1 , and an annular side yoke  22  secured to the lower rotor yoke  23 . An annular speaker permanent magnet  17  is secured to the lower rotor yoke  23  around the shaft  16 , and a central top yoke  18  is secured to the magnet  17  by the shaft  16 . The speaker permanent magnet  17  is magnetized in single-polarity in the axial direction. Thus, a first magnetic circuit is formed between the top yoke  18  and the side yoke  22 .  
         [0036]    An annular rotor permanent magnet  21  is secured to the peripheral wall of the side yoke  22  and to the lower rotor yoke  23 . As shown in FIG. 3, the rotor permanent magnet  21  is magnetized in multiple-polarity in the radial direction, so that the peripheral wall of the rotor permanent magnet has a plurality of magnetic poles. Thus, a second magnetic circuit is formed between the rotor  20  and the stator  30 . The voice coil  15  is disposed in a speaker gap  11  formed between the outside wall of the top yoke  18  and the inside wall of the side yoke  22 .  
         [0037]    As shown in FIGS. 2 and 3, a semicircular weight  24  made of plastic including heavy particles such as tungsten particles is secured to the outside wall of the side yoke  22  and mounted on the rotor permanent magnet  21 . As another means, the permanent magnet  21  may be eccentrically disposed with respect to the rotor shaft  16 . A motor gap  12  is formed between the periphery of the rotor permanent magnet  21  and the inside wall of the stator  30 . As shown in FIGS. 1 and 2, the annular stator  30  is disposed around the rotor  20 .  
         [0038]    Referring to FIG. 4, the stator  30  comprises an annular stator coil  33 , annular upper and lower shading plates  36  and  35  disposed on the upper and lower sides of the annular coil  33 , and annular upper and lower stator yokes  31  and  32 . The upper stator yoke  31  has four main magnetic poles  31   a   1 ,  31   b   1 ,  31   c   1  and  31   d   1 , and four auxiliary magnetic poles  31   a   2 ,  31   b   2 ,  31   c   2  and  31   d   2 . Each of the magnetic poles extends in the axial direction and toward the lower stator yoke  32 . The lower stator yoke  32  has four main magnetic poles  32   a   1 ,  32   b   1 ,  32   c   1  and  32   d   1  and four auxiliary magnetic poles  32   a   2 ,  32   b   2 ,  32   c   2  and  32   d   2 .  
         [0039]    A couple of upper main and auxiliary magnetic poles  31   a   1  and  31   a   2  and a couple of lower main and auxiliary magnetic poles  32   a   1  and  3   a   2 , and other couples of the magnetic poles are angularly disposed at one magnetic pole pitch of 90 degrees (electric angle 360°). The sum of widths of the main magnetic pole and the auxiliary magnetic pole is within 45 degrees, and the width of the main magnetic pole is larger than that of the auxiliary magnetic pole.  
         [0040]    The couple of upper main and auxiliary magnetic poles and the couple of lower main and auxiliary magnetic poles are alternately disposed on the same circle as shown in FIG. 2.  
         [0041]    The upper shading plate  36  has four holes  36   a ,  36   b ,  36   c  and  36   d,  each formed in a projection projected from the inside wall of the shading plate  36  in the radially inward direction. Similarly, the lower shading plate  35  has four holes  35   a ,  35   b,    35   c  and  35   d.  The auxiliary magnetic poles  31   a   2 ,  31   b   2 ,  31   c   2  and  31   d   2  of the upper stator yoke  31  are inserted in the holes  36   a - 36   d  of the upper shading plate  36 . Similarly, the auxiliary magnetic poles  32   a   2 ,  32   b   2 ,  3   c   2  and  32   d   2  of the lower stator yoke  32  are inserted in the holes  35   a - 35   d  of the lower shading plate  35 .  
         [0042]    Referring to FIGS. 1 and 4, the lower stator yoke  32  has a cylindrical peripheral wall  32   e . The lower shading plate  35  is mounted on the lower stator yoke  32  between the peripheral wall  32   e  and main and auxiliary magnetic poles. The stator coil  33 , upper shading plate  36 , and upper stator plate  31  are stacked on the lower shading plate  35  in order. Thus, the rotor  20  and stator  30  are composed in a synchronous motor.  
         [0043]    It will be understood that the motor can be made into a stepping motor having a permanent magnet rotor having multiple polarities.  
         [0044]    The magneto motive force of the permanent magnet  21  is applied to the speaker and motor gaps  11  and  12  in parallel, so that a necessary magnetic flux density is provided.  
         [0045]    Referring to FIG. 5, a rotor driving circuit  40  comprises a pair of NPN transistors  41  and  43  and a pair of PNP transistors  42  and  44  which are connected crosswise, interposing the stator coil  33 . Bases of the transistors  41  and  42  are connected to an input terminal  48 , bases of the transistors  43  and  44  are connected to the input terminal  48  through an inverter  47 .  
         [0046]    In operation, when a high frequency signal is applied to input terminals  19   a  and  19   b  (FIG. 1) of the voice coil  15 , the speaker diaphragm  14  is vibrated in the Y direction (FIG. 1) to generate sounds.  
         [0047]    When a low frequency signal of about 100-300 Hz is applied to input terminal  48  of the driving circuit  40 , the transistors  41  and  44  are turned on at a high level of the input signal. Consequently, a current passes the stator coil  33  through the transistors  41  and  44  from the Vcc to GND. And the current passes through the transistor  43 , coil  33  and transistor  42  at a low level of the input signal. Thus, an alternate current of the low frequency corresponding to the input low frequency signal flows in the stator coil  33 . Consequently, couples of main pole  32   a   1  and auxiliary pole  32   a   2  to poles  32   d   1  and  32   d   2  are energized. At that time, magnetic flux generated by four auxiliary poles  31   a   2 ,  31   b   2 ,  31   c   2  and  31   d   2 , and magnetic flux generated by four auxiliary poles  32   a   2 ,  32   b   2 ,  32   c   2  and  32   d   2  are delayed in phase by eddy currents passing through holes  36   a - 36   d  of the upper shading plate  36  and holes  35   a - 35   d  of the lower shading plate  35  to produce a shifting magnetic field to generate rotating power in a predetermined direction. Thus, the rotor  20  is rotated at the driving low frequency. Since the weight  24  is eccentrically mounted on the rotor  20 , the rotor vibrates in radial direction. The vibration is transmitted to user&#39;s body through the frame  1  and a case of the device so that a calling signal is informed to the user.  
         [0048]    The number N of rotation of the rotor is expressed as follows.  
         N=60f/Z (rpm)   1  
         [0049]    where Z is a pair of number of poles of the rotor,  
         [0050]    f is driving frequency.  
         [0051]    The load torque TL is expressed as follows.  
         TL=μrRΩ 2 M (N·m)   2  
         [0052]    where M is the mass of weight  24  of the rotor,  
         [0053]    R is the length between the center of the rotor shaft  16  and the center of gravity of the weight  24 ,  
         [0054]    r is the radius of the rotor shaft  16 ,  
         [0055]    μ is the friction coefficient between the rotor shaft  16  and the rotor  20 ,  
         [0056]    Ω is the number of rotation (rad/sec) of the rotor  20 .  
         [0057]    Since the rotor  20  merely bears the load torque TL, the power consumption of the device is small.  
         [0058]    If a lower frequency signal is applied to the input terminal  48  to rotate the rotor  20  during the generating sounds by the speaker diaphragm  14 , the magnetic flux density in the first gap  11  does not change from the magnetic flux density when only the speaker diaphragm  14  is vibrated. Therefore, quality of sounds generated by the vibrating plate does not reduce even if the rotor  20  rotates Although the synchronous motor is used in the above described embodiments, other motors such as a stepping motor, a direct current motor and others can be used. Further, the rotor can be disposed outside the stator.  
         [0059]    Referring to the trouble shooting system of the present invention, an oscillator  50  is provided for generating a driving signal which is applied to the input terminal  48  of the circuit of FIG. 5 for driving the rotor  20 . The system comprises a frequency divider  51 , the driving circuit  40  (FIG. 5), a voltage detecting circuit  52 , a comparator  53 , a sweeper  54 , a hold circuit  55 , and a counter  56 .  
         [0060]    The sweeper  54  linearly increases a frequency f fed from the frequency divider  51  from an initial frequency f so  to an end frequency f ss . The rotor  20  is driven by the driving circuit  40 . During the rotating of the rotor, the voltage Vd induced in the stator coil  33  is lower than the voltage Vc at the time when the rotor  20  is stopped by vibration of the acoustic device or shock applied to the device. Therefore, the voltage Vc is set in the comparator  53  as a reference value, so that the stopping of the rotor  20  can be detected by comparing the voltage Vd with the voltage Vc.  
         [0061]    [0061]FIG. 7 shows the system flowchart. The system flowchart comprises a start  60 , setting step  61 , sweeping step  62 , holding step  63 , voltage checking step  64 , a feedback loop  65  and end  66 .  
         [0062]    At the step  61 , frequencies f so , f ss , voltages Vd, Vc are set. At the step  63 , the frequency f ss  is held.  
         [0063]    At the step  64 , when the voltage Vc equals or is lower than voltage Vd, the program returns to the step  62  passing the feedback loop  65 , so that the frequency starts from f so .  
         [0064]    [0064]FIG. 8 shows variations of the number of rotation N of the rotor  20  and the current induced in the stator coil  33  on the time axis.  
         [0065]    The number of rotation N starts from N so  at a point A in the time τ 1  and reaches N ss  at a point B. In the case of wobbling tone, the rotation continues for time τ 2  and stops at a point C. Thus, the rotation sequentially repeats the steps A, B, C, D, E.  
         [0066]    On the other hand, the current I changes such as M (I so ), G, H (I ss ), J. When the rotor is stopped, the current increases to the line K, L. The current difference K-J is detected as voltage difference by the resistance of the stator coil  33 . The voltage difference is detected by the comparator  53 . Thus, the number of rotation N returns to the initial number N so , the current I returns to I so . Thereafter, the number of rotation and the current gradually increases. Thus, the abnormal stopping of the stator is recovered to a normal condition.  
         [0067]    In accordance with the present invention, when the rotor is abnormally stopped, the rotation of the rotor is returned to an initial speed at the start of the operation. Therefore, the rotation speed is stably held, thereby preventing the sound quality from decreasing.  
         [0068]    From the foregoing description, it will be understood that the present invention provides a multifunction acoustic device which may generate sounds and vibration of the frame at the same time without reducing sound quality. In the prior art, since the speaker diaphragm and the magnetic composition are vibrated in the same direction, the thickness of the device increases. In the device of the present invention, since the magnetic composition rotates, the thickness of the device can be reduced.  
         [0069]    While the invention has been described in conjunction with preferred specific embodiment thereof, it will be understood that this description is intended to illustrate and not limit the scope of the invention, which is defined by the following claims.

Technology Classification (CPC): 7