Abstract:
A speaker vibrating plate having a voice coil secured thereto is provided in a frame, a rotor having poles is rotatably supported in the frame, and a stator having poles is provided in the frame. A permanent magnet is provided in the rotor for forming a magnetic circuit passing through the rotor and the stator, and a stator coil is provided in the stator. A driving circuit is provided for energizing the stator coil for rotating the rotor.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a multifunction acoustic device used in a portable instrument such as a portable telephone. 
     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. 
     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. 
     FIG. 7 is a sectional view of a conventional electromagnetic induction converter disclosed in Japanese Patent Laid Open 5-85192. The converter comprises a diaphragm  606  mounted in a case  612  at a periphery thereof, a voice coil  609  secured to the underside of a central portion  607  of the diaphragm  606 , a spring plate  611  mounted in the case  612 , and a permanent magnet  610  secured to a central portion of the spring plate  611 , inserted in the voice coil  609 . 
     By applying a low or high frequency signal to the voice coil  609 , the spring plate  611  is vibrated in the polarity direction Y of the magnet  610 . 
     In the device, the diaphragm  606  and the spring plate  611  are relatively moved through the magnetic combination between the voice coil  609  and the magnet  610 . Consequently, when a low frequency signal or a high frequency signal is applied to the voice coil  609 , both of the diaphragm  606  and the spring plate  611  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  609  and the magnet  610  causes the low frequency vibration of the magnet to superimpose on the magnetic combination of the voice coil  609  and the magnet  610 , which further largely distorts the sounds. 
     FIG. 8 is a sectional view showing a conventional multifunction acoustic device. The device comprises a speaker vibrating plate  703  made of plastic and having a corrugated periphery  703   a  and a central dome, a voice coil  704  secured to the underside of the vibrating plate  703  at a central portion, and a magnet composition  710 . The vibrating plate  703  is secured to a frame  709  with adhesives. 
     The magnetic composition  710  comprises a lower yoke  705 , a core  701  formed on the yoke  705  at a central portion thereof, an annular permanent magnet  702  mounted on the lower yoke  705 , and an annular upper yoke  706  mounted on the permanent magnet  702 . The lower yoke  705  and the upper yoke  706  are resiliently supported in the frame  709  by spring plates  707  and  708 . A magnetic gap  711  is formed between a periphery  701   a  of the core  701  and an inside wall  706   a  of the upper yoke  706  to be magnetically connected to the voice coil  704 . 
     When an alternating voltage is applied to the voice coil  704  through input terminals  712   a  and  712   b , the speaker vibrating plate  703  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  704 , the speaker vibrating plate  703  and the magnetic composition  710  are sequentially vibrated, since the magnetic composition  710  and the speaker vibrating plate  703  are relatively moved through the magnetic combination of the voice coil  704  and the magnet composition  710 . 
     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  704  and the magnetic composition  710  causes the low frequency vibration to superimpose on the magnetic combination of the voice coil  704  and the magnetic composition  710 , which further largely distorts the sounds. 
     FIG. 9 is a sectional view showing another conventional multifunction acoustic device. The device comprises the speaker vibrating plate  703  made of plastic and having the corrugated periphery  703   a  and the central dome, the voice coil  704  secured to the underside of the vibrating plate  703  at a central portion, and the magnet composition  710 . The vibrating plate  703  is secured to the frame  709  with adhesives. 
     The magnetic composition  710  comprises a lower yoke  803 , core  701  formed on the yoke  803  at a central portion thereof, an annular permanent magnet  802  secured to the lower yoke  803 , and annular upper yoke  706  having a peripheral wall  706   b  and mounted on the permanent magnet  702 . The upper yoke  706  is resiliently supported in the frame  709  by spring plates  807  and  808 . A first magnetic gap  801  is formed between a periphery  701   a  of the core  701  and an inside wall  706   a  of the upper yoke  706  to be magnetically connected to the voice coil  704 . A second gap  805  is formed between a periphery  803   a  of the lower yoke  803  and inside wall  706   a  of the upper yoke  706 . A driving coil  806  is secured to the frame and inserted in the second gap  805 . 
     When an alternating voltage is applied to the voice coil  704  through input terminals  712   a  and  712   b , the speaker vibrating plate  703  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  704 , the speaker vibrating plate  703  and the magnetic composition  710  are sequentially vibrated, since the magnetic composition  710  and the speaker vibrating plate  703  are relatively moved through the magnetic combination of the voice coil  704  and the magnet composition  710 . 
     When a high frequency signal for music is applied to the voice coil  704 , only the speaker vibrating plate  703  is vibrated. Therefore, there does not occur distortion of the sound. Furthermore, when a low frequency signal is applied to the driving coil  806 , only the magnetic composition  710  is vibrated, and the speaker vibrating plate  703  is not vibrated. 
     However if a high frequency signal is applied to input terminals  712   a ,  712   b , and a low frequency signal is also applied to input terminals  804   a ,  804   b , the speaker vibrating plate  703  and magnetic composition  710  are sequentially vibrated, thereby reducing the sound quality. 
     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 
     An object of the present invention is to provide a multifunction acoustic device in which a vibrating member is not vibrated together with another vibrating member, thereby removing disadvantages of conventional devices. 
     According to the present invention, there is provided a multifunction acoustic device comprising a frame, a speaker vibrating plate supported in the frame, a voice coil secured to the speaker vibrating plate, a rotor having magnetic poles and rotatably supported in the frame, a stator having magnetic poles and provided in the frame, corresponding to the rotor, a first permanent magnet provided on the rotor, at least one coil for forming magnetic fluxes between the magnetic poles of the rotor and the magnetic poles of the stator. 
     The device further comprises eccentric means provided on the rotor for vibrating the rotor during the rotation of the rotor. 
     The first permanent magnet is an annular magnet, and the voice coil is disposed in a gap formed in the annular magnet. 
     In an aspect of the invention, the coil is disposed in the stator. 
     A second permanent magnet is provided in the gap for increasing a magnetic flux density in the gap. 
     The eccentric means is a weight eccentrically provided in the rotor. 
     The device further comprises a driving circuit for energizing the coil in the stator for rotating the rotor. 
     In a further aspect of the invention, the rotor comprises a lower rotor yoke rotatably mounted in the frame, and an upper rotor yoke secured to the lower rotor yoke, and the stator comprises a lower stator yoke and an upper stator yoke secured to the lower stator yoke. 
     The first permanent magnet is disposed between the lower rotor yoke and the upper rotor yoke, and the stator coil is disposed between the lower stator yoke and the upper stator yoke, and the rotor and the stator are formed into a synchronous motor. 
     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 
     FIG. 1 is a sectional view of a multifunction acoustic device as a first embodiment of the present invention; 
     FIG. 2 is a sectional view taken along a line II—II of FIG. 1; 
     FIG. 3 is an exploded perspective view of a rotor of the multifunction acoustic device of the present invention; 
     FIG. 4 is an exploded perspective view of a stator of the multifunction acoustic device of the present invention; 
     FIG. 5 is a driving circuit used in the multifunction acoustic device of the present invention; 
     FIG. 6 is a sectional view of a multifunction acoustic device as a second embodiment of the present invention; 
     FIG. 7 is a sectional view of a conventional electromagnetic induction converter; 
     FIG. 8 is a sectional view showing a conventional multifunction acoustic device; and 
     FIG. 9 is a sectional view showing another conventional multifunction acoustic device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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 vibrating plate  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 vibrating plate  14 . The speaker vibrating plate  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. 
     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 , central top yoke  18  secured to the lower rotor yoke  23  and secured to the rotor shaft  16  at a central hole  18   a  thereof, an annular permanent magnet  21  securely mounted on the lower rotor yoke  23  and an annular upper rotor yoke  22  secured to the lower rotor yoke  23  and mounted on the permanent magnet  21 . The permanent magnet  21  is axially magnetized in single polarity. The voice coil  15  is disposed in a first gap  11  formed between the outside wall of the top yoke  18  and the inside wall of the upper rotor yoke  22 . 
     Referring to FIG. 3, the upper rotor yoke  22  has four magnetic poles  22   a ,  22   b ,  22   c  and  22   d . Each of the magnetic poles is formed by bending a radially extending projection in the axial direction and toward the lower rotor yoke  23 . The lower rotor yoke  23  has four magnetic poles  23   a ,  23   b ,  23   c  and  23   d  each of which extends in the axial direction and toward the upper rotor yoke  22 . The magnetic poles of the upper rotor yoke and magnetic poles of the lower rotor yoke are alternately disposed on the same circle as shown in FIG.  2 . Couples of magnetic poles  22   a  and  23   a  ( 22   b  and  23   b ,  22   c  and  23   c ,  22   d  and  23   d ) are angularly disposed at one magnetic pole pitch of 90 degrees (electric angle 360°). 
     The width of the magnetic pole of each of the magnetic poles  22   a  to  23   d  is suitably selected from widths smaller than 45 degrees. The shape of the magnetic pole may be triangular. A semicircular weight  24  made of plastic including heavy particles such as tungsten particles is disposed around the permanent magnet  21 . As another means, the permanent magnet  21  may be eccentrically disposed with respect to the rotor shaft  16 . A second gap  12  is formed between the periphery of the rotor  20  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 . 
     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 . 
     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  32   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. 
     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 . 
     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 ,  32   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 . 
     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. 
     It will be understood that the motor can be made into a stepping motor having a permanent magnet rotor having multiple polarities. 
     The magnetomotive force of the permanent magnet  21  is applied to the first and second gaps  11  and  12  in parallel, so that a necessary magnetic flux density is provided. 
     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 . 
     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 vibrating plate  14  is vibrated in the Y direction (FIG. 1) to generate sounds. 
     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. 
     The number N of rotation of the rotor is expressed as follows. 
     
       
           N =60 f/Z (rpm)  1  
       
     
     where 
     Z is a pair of number of poles of the rotor, 
     f is driving frequency. 
     The load torque TL is expressed as follows. 
     
       
         TL=μ r Rω 2   M ( N·m )  2  
       
     
     where 
     M is the mass of weight  24  of the rotor, 
     R is the length between the center of the rotor shaft  16  and the center of gravity of the weight  24 , 
     r is the radius of the rotor shaft  16 , 
     μ is the friction coefficient between the rotor shaft  16  and the rotor  20 , 
     ω is the number of rotation (rad/sec) of the rotor  20 . 
     Since the rotor  20  merely bears the load torque TL, the power consumption of the device is small. 
     If a lower frequency signal is applied to the input terminal  48  to rotate the rotor  20  during the generating sounds by the speaker vibrating plate  14 , the magnetic flux density in the first gap  11  does not change from the magnetic flux density when only the speaker vibrating plate  14  is vibrated. 
     Referring to FIG. 6 showing the second embodiment of the present invention, the same parts as the first embodiment are identified by the same reference numerals as those of FIG. 1, and the explanation thereof is omitted. A central annular permanent magnet  51  is securely mounted on the lower rotor yoke  23  around the shaft  16 . On the permanent magnet  51 , a top yoke  52  is secured. The permanent magnets  21  and  51  are magnetized in reverse directions, so that the magnetic flux density of the first gap  11  between both the magnets is increased. Construction of other portions is the same as the first embodiment. 
     Since the magnetic flux density in the first gap  11  is high, the sounds generated by the speaker vibrating plate  14  are not influenced by the rotation of the rotor  20 . 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. 
     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 vibrating plate 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. 
     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.