Patent Publication Number: US-9854366-B2

Title: Speaker device

Description:
TECHNICAL FIELD 
     The present invention relates to a speaker device. 
     BACKGROUND ART 
     A noise cancellation technique of cancelling external noise at, e.g., a speaker device or headphones so that a user&#39;s ears can hear only musical sound has been typically in widespread use. According to such a noise cancellation technique, the external noise is detected by a microphone, and then, a noise cancellation signal with a phase opposite to that of the detected noise signal is generated. Subsequently, the noise cancellation signal is output from, e.g., the speaker device to cancel the external noise. 
     Meanwhile, a full digital speaker device configured so that a digital signal can be directly input to a speaker has been recently developed. This full digital speaker device can directly transfer the digital signal to the speaker, and therefore, digital/analog conversion is no longer required. Thus, high-quality sound can be realized regardless of performance of a digital/analog converter. 
     However, when the above-described noise cancellation technique is applied to the full digital speaker device, a delay of about 0.5 msec to 3 msec is, due to a delay caused by an arithmetic circuit of a digital filter portion provided in the full digital speaker device, caused after input of a noise signal until output of sound. 
     For this reason, when an attempt is made to perform signal processing for the input noise signal to remove noise as in the typical noise cancellation technique, a noise-processed signal delay corresponding to the signal processing is also caused, and a delay in response to actual noise is caused. Thus, there is a problem that effective noise reduction cannot be performed. 
     In order to prevent such a delay, a device has been typically proposed, which includes a speaker unit having a single diaphragm and two voice coils configured to drive the diaphragm and which is configured such that a musical sound signal is input to one of the voice coils and a noise cancellation signal based on a noise signal detected by a noise detection microphone is input to the other voice coil, for example (see Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Laid-Open No. 2008-098988 
     SUMMARY OF INVENTION 
     Technical Problem 
     According to Patent Literature 1, the noise cancellation signal is input to one of the double wound voice coils, and in this manner, the single diaphragm is driven to cancel noise. Thus, the signal for noise cancellation can be simplified, and a delay in response to actual noise can be reduced as much as possible. 
     However, the device of Patent Literature 1 is applied to a typical dynamic speaker. Due to an increase in the number of voice coils, the weights of the diaphragm and the voice coil portion themselves in the speaker device increase. For this reason, vibration of the diaphragm is reduced, leading to interruption of high-frequency characteristics and lowering of acoustic characteristics. 
     The present invention has been made in view of the above-described points, and is intended to provide a speaker device configured so that a time lag between a sound signal and a noise cancellation signal can be prevented, worsening of high-frequency characteristics can be avoided, and acoustic characteristics can be improved. 
     Solution to Problem 
     In order to accomplish the above-described objective, the present invention relates to a speaker device including a plane diaphragm. In the speaker device, the plane diaphragm includes a sound voice coil pattern to which drive current corresponding to a sound signal is supplied, and a noise cancellation voice coil pattern to which drive current corresponding to a noise cancellation signal is supplied, and the sound voice coil pattern and the noise cancellation voice coil pattern are formed corresponding to a formed magnetic field of a magnet. 
     Moreover, in the above-described configuration, the plane diaphragm may be configured such that the sound voice coil pattern and the noise cancellation voice coil pattern are formed on a flexible circuit board. Further, in the above-described configuration, the noise cancellation voice coil pattern may be formed on one side of the sound voice coil pattern. In addition, in the above-described configuration, the noise cancellation voice coil pattern may be formed on each side of the sound voice coil pattern. 
     Moreover, in the above-described configuration, the noise cancellation voice coil pattern may include a plurality of noise cancellation voice coil patterns, and end portions of the noise cancellation voice coil patterns may be electrically connected together to form a single noise cancellation voice coil pattern. Further, in the above-described configuration, a resistor element may be connected to a middle portion of the noise cancellation voice coil pattern. In addition, in the above-described configuration, a reinforcement pattern may be formed between two adjacent patterns of the sound voice coil pattern and/or the noise cancellation voice coil pattern of the plane diaphragm. 
     Advantageous Effects of Invention 
     According to the present invention, the sound voice coil pattern to which the drive current corresponding to the sound signal is supplied and the noise cancellation voice coil pattern to which the drive current corresponding to the noise cancellation signal is supplied are formed, and therefore, reproduced sound with a favorable sound quality can be obtained without noise signal influence on the sound signal. Moreover, since the sound voice coil pattern and the noise cancellation voice coil pattern are formed, the surface of the diaphragm can be hardened. As a result, a transmission speed by the diaphragm can be increased, and worsening of high-frequency characteristics can be avoided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of a speaker device, illustrating a first embodiment of a speaker device of the present invention. 
         FIG. 2  is a longitudinal sectional view of the speaker device. 
         FIG. 3  is a plan view of a diaphragm. 
         FIG. 4  is an enlarged partial view of the diaphragm in a frame indicated by a chain line of  FIG. 3 . 
         FIG. 5  is a block diagram of a drive circuit. 
         FIG. 6  is an enlarged partial view of a diaphragm, illustrating a second embodiment of the speaker device of the present invention. 
         FIG. 7  is an enlarged partial view of a diaphragm, illustrating a third embodiment of the speaker device of the present invention. 
         FIG. 8  is an enlarged partial view of a diaphragm, illustrating a fourth embodiment of the speaker device of the present invention. 
         FIG. 9  is an enlarged partial view of a diaphragm, illustrating a fifth embodiment of the speaker device of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of a speaker device of the present invention will be described below with reference to drawings. 
       FIG. 1  is an exploded perspective view of the speaker device, and  FIG. 2  is a longitudinal sectional view of the speaker device.  FIG. 3  is a plan view of a diaphragm, and  FIG. 4  is an enlarged partial view of the diaphragm in a frame indicated by a chain line of  FIG. 3 . 
     In the present embodiment, an example of a full digital speaker device using a plane diaphragm is described as the speaker device. 
     A speaker device  10  of the present embodiment includes a diaphragm  11 , a pair of magnets  13  vertically sandwiching the diaphragm  11  with a buffer member  12  being interposed between each magnet  13  and the diaphragm  11 , and a pair of holding members  14  covering all of these members from upper and lower sides. 
     The diaphragm  11  is formed of a thin film-shaped flexible circuit board  20 , and a sound voice coil pattern  21  to which drive current is supplied based on a sound signal is formed on one surface of the flexible circuit board  20 . As illustrated in  FIGS. 3 and 4 , the sound voice coil pattern  21  is formed such that a plurality of conductive wire patterns meander across the entirety of the flexible circuit board  20 . 
     Moreover, in the present embodiment, a single noise cancellation voice coil pattern  22  is, on one side of the sound voice coil pattern  21  on the flexible circuit board  20 , formed to meander substantially in parallel to the sound voice coil pattern  21 , as illustrated in  FIG. 3 . 
     Note that in  FIGS. 4, 6, and 9 , the sound voice coil pattern  21  is indicated by a solid line, and the noise cancellation voice coil pattern  22  is indicated by a chain line, for the sake of description. 
     A conductive wire drawing portion  23  configured to draw the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  to the outside is provided integrally with one side of the diaphragm  11 , and a tip end portion of the conductive wire drawing portion  23  is provided with a terminal portion  24  connected to end portions of the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22 . 
     It is configured such that drive current is applied from the terminal portion  24  based on a predetermined digital sound signal and a predetermined analog noise cancellation signal. 
     Moreover, as illustrated in  FIG. 2 , the magnets  13  are formed in such a striped pattern that the N-pole and the S-pole are alternatively positioned along the line of the voice coil pattern. 
     A magnetic field component vertical to the surface of each magnet  13  is greatest in the vicinity of the N-pole and the S-pole, and is smallest in the vicinity of the boundary between the N-pole and the S-pole. On the other hand, a horizontal magnetic field component parallel to the surface of each magnet  13  is smallest in the vicinity of the N-pole and the S-pole, and is greatest in the vicinity of the boundary between the N-pole and the S-pole. Thus, a magnetic field component contributing to vibration of the diaphragm  11  in the thickness direction thereof is not a vertical component but a horizontal component (the Fleming&#39;s left hand rule). 
     Thus, linear portions of the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are arranged at positions corresponding to the vicinity of the boundary between the N-pole and the S-pole such that lines of magnetic force extend in the direction intersecting the linear portions of the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  in the plane of the diaphragm  11 . 
     Thus, in the present embodiment, it is configured such that the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are arranged at the boundary between the N-pole and the S-pole. When drive current is applied to the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22 , electromagnetic force is most efficiently generated by interaction between the drive current and a magnetic field, and the diaphragm  11  vibrates in the thickness direction thereof. 
     As illustrated in  FIG. 1 , each magnet  13  is provided with a plurality of through-holes  25  through which sound output from the diaphragm  11  passes. As described above, the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are arranged at the boundary between the N-pole and the S-pole so that the diaphragm  11  can efficiently vibrates at such a boundary. Thus, each through-hole  25  is preferably formed at a position corresponding to the boundary between the N-pole and the S-pole. 
     Each buffer member  12  is made of a soft material, and has a function to allow sound to pass through the buffer member  12 . The buffer member  12  is made of non-woven fabric, for example. The buffer member  12  is formed to have the substantially same size as that of the diaphragm  11 , and forms a predetermined gap between the diaphragm  11  and the magnet  13 . The buffer member  12  is configured to prevent noise generation due to contact between the diaphragm  11  and the magnet  13  in driving of the diaphragm  11 . Depending on the thickness and material of the buffer member  12 , a plurality of buffer members  12  may be used in the form of a stack, if necessary. 
     Each holding member  14  is made of a hard material such as metal. In the state in which the diaphragm  11 , the buffer members  12 , and the magnets  13  are sandwiched between the holding members  14 , not-shown screws etc. are screwed into the outer periphery of each holding member  14 , and therefore, the diaphragm  11  is held and fixed between the pair of magnets  13  with a predetermined gap being formed between the diaphragm  11  and each magnet  13 . Moreover, the holding member  14  is provided with through-holes  26  at positions similar to those of the through-holes  25  of the magnet  13 , and each through-hole  26  allows sound from the diaphragm  11  to be efficiently emitted to the outside. 
     Next, a drive circuit of the speaker device  10  described above will be described with reference to  FIG. 5 . 
     As illustrated in  FIG. 5 , a drive circuit  30  includes a sound driver circuit  32  to which a digital sound signal is input from a predetermined digital sound source  31 . The sound driver circuit  32  is configured to convert the digital sound signal into a predetermined sound drive signal to supply the sound voice coil pattern  21  with drive current corresponding to the sound drive signal through the terminal portion  24 . 
     The drive circuit  30  further includes a microphone  33  to which external noise is input, and a noise cancellation circuit  34  to which an external noise signal is input from the microphone  33 . The noise cancellation circuit  34  is configured to invert the phase of the noise signal from the microphone  33  and to use the phase-inverted signal as a noise cancellation signal to supply the noise cancellation voice coil pattern  22  with drive current corresponding to the noise cancellation signal through the terminal portion  24 . 
     Next, features of the present embodiment will be described. 
     In the present embodiment, the sound signal sent from the predetermined digital sound source  31  is converted into the sound drive signal by the sound driver circuit  32 , and the drive current corresponding to the sound drive signal is supplied to the sound voice coil pattern  21 . 
     Meanwhile, the external noise is input through the microphone  33 , and is sent to the noise cancellation circuit  34 . The noise cancellation circuit  34  inverts the phase of the noise signal from the microphone  33 , and then, the drive current corresponding to the phase-inverted noise cancellation signal is supplied to the noise cancellation voice coil pattern  22 . 
     Since the drive current corresponding to the sound signal and the drive current corresponding to the noise cancellation signal are supplied, electromagnetic force is generated by interaction between each type of drive current and the magnetic field of each magnet  13 , and the diaphragm  11  vibrates in the thickness direction thereof. At this point, since not only the drive current corresponding to the sound signal but also the drive current corresponding to the noise cancellation signal are supplied, the diaphragm  11  vibrates based on a composite signal of the sound signal and the noise cancellation signal. Thus, sound of the sound signal can be output with the external noise being cancelled out. 
     As described above, in the present embodiment, the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are formed on the flexible circuit board  20 , and the drive current corresponding to the sound signal and the drive current corresponding to the noise cancellation signal are supplied. Thus, the diaphragm  11  vibrates based on the composite signal of the sound signal and the noise cancellation signal. Consequently, sound of the sound signal can be output with the external noise being cancelled out. As a result, reproduced sound with a favorable sound quality can be obtained without noise signal influence on the sound signal. 
     Moreover, in the present embodiment, the noise cancellation voice coil pattern  22  is, in addition to the sound voice coil pattern  21 , formed on the flexible circuit board  20 . Thus, the surface of the diaphragm  11  can be hardened by addition of the noise cancellation voice coil pattern  22 . As a result, a transmission speed by the diaphragm  11  can be increased, and worsening of high-frequency characteristics can be avoided. 
     Next, a second embodiment of the present invention will be described. 
       FIG. 6  illustrates the second embodiment of the present invention. In the present embodiment, a noise cancellation voice coil pattern  22  is formed on each side of a sound voice coil pattern  21  formed on a flexible circuit board  20 . 
     That is, the noise cancellation voice coil pattern  22  is formed on one side of the sound voice coil pattern  21  in the first embodiment. However, in the case of forming the noise cancellation voice coil pattern  22  on one side of the sound voice coil pattern  21 , there is a probability that the amplitude of the diaphragm  11  is non-uniform. 
     For this reason, in the present embodiment, the noise cancellation voice coil pattern  22  is formed on each side of the sound voice coil pattern  21  so that the diaphragm  11  can uniformly vibrate on the sound voice coil pattern  21 . 
     As in the first embodiment, the sound voice coil pattern  21  and the noise cancellation voice coil patterns  22  are, in the present embodiment, formed on the flexible circuit board  20 , and drive current corresponding to a sound signal and drive current corresponding to a noise cancellation signal are supplied. Thus, the diaphragm  11  vibrates based on a composite signal of the sound signal and the noise cancellation signal. Consequently, sound of the sound signal can be output with external noise being cancelled out. 
     Moreover, the noise cancellation voice coil pattern  22  is formed on each side of the sound voice coil pattern  21  on the flexible circuit board  20 . Thus, as compared to the first embodiment, the surface of the diaphragm  11  can be more hardened. As a result, a transmission speed by the diaphragm  11  can be increased, and worsening of high-frequency characteristics can be avoided. 
     Next, a third embodiment of the present invention will be described. 
       FIG. 7  illustrates the third embodiment of the present invention. In general, as compared to a dynamic speaker device, a speaker device using a plane diaphragm  11  tends to exhibit a smaller impedance and consume greater current. This might lead to an increase in power consumption of a power amplifier circuit, and therefore, leads to functioning of an overcurrent protection circuit. 
     For this reason, in the present embodiment, a noise cancellation voice coil pattern  22  is formed on each side of a sound voice coil pattern  21  as in the second embodiment, and end portions of the noise cancellation voice coil patterns  22  are electrically connected together to form a single long noise cancellation voice coil pattern  22  disposed on both sides of the sound voice coil pattern  21 . 
     With this noise cancellation voice coil pattern  22  having a great length dimension, the resistance of the noise cancellation voice coil pattern  22  increases, and therefore, the impedance of the noise cancellation voice coil pattern  22  can be enhanced. 
     As in each of the above-described embodiments, the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are, in the present embodiment, formed on a flexible circuit board  20 , and drive current corresponding to a sound signal and a noise cancellation signal is supplied. Thus, the diaphragm  11  vibrates based on a composite signal of the sound signal and the noise cancellation signal. Consequently, sound of the sound signal can be output with external noise being cancelled out. 
     Moreover, the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are formed on the flexible circuit board  20 . Thus, the surface of the diaphragm  11  can be hardened. As a result, a transmission speed by the diaphragm  11  can be increased, and worsening of high-frequency characteristics can be avoided. 
     Further, the end portions of the noise cancellation voice coil patterns  22  are electrically connected together, and the noise cancellation voice coil pattern  22  is formed to have a great length dimension. Thus, the resistance of the noise cancellation voice coil pattern  22  increases, and therefore, the impedance of the noise cancellation voice coil pattern  22  can be enhanced. As a result, current consumption can be reduced. This can prevent functioning of the overcurrent protection circuit. 
     Note that in the first and second embodiments, drawing of a wiring pattern of the noise cancellation voice coil pattern  22  can be devised such that a great length dimension of the noise cancellation voice coil pattern  22  is ensured. Thus, the impedance of the noise cancellation voice coil pattern  22  can be increased. However, in the present embodiment, the impedance of the noise cancellation voice coil pattern  22  can be easily increased without such devising of drawing of the wiring pattern. 
     Next, a fourth embodiment of the present invention will be described. 
       FIG. 8  illustrates the fourth embodiment of the present invention. In order to increase the impedance of a noise cancellation voice coil pattern  22 , the noise cancellation voice coil pattern  22  is, in the present embodiment, formed on each side of a sound voice coil pattern  21 , and a resistor element  35  is connected to a middle portion of each noise cancellation voice coil pattern  22 . 
     With the resistor element  35  connected to each noise cancellation voice coil pattern  22 , the resistance of the noise cancellation voice coil pattern  22  is increased, and therefore, the impedance of the noise cancellation voice coil pattern  22  can be enhanced. 
     As in each of the above-described embodiments, the sound voice coil pattern  21  and the noise cancellation voice coil patterns  22  are, in the present embodiment, formed on a flexible circuit board  20 , and drive current corresponding to a sound signal and a noise cancellation signal is supplied. Thus, a diaphragm  11  vibrates corresponding to a composite signal of the sound signal and the noise cancellation signal. Consequently, sound of the sound signal can be output with external noise being cancelled out. 
     Moreover, the sound voice coil pattern  21  and the noise cancellation voice coil patterns  22  are formed on the flexible circuit board  20 . Thus, the surface of the diaphragm  11  can be hardened. As a result, a transmission speed by the diaphragm  11  can be increased, and worsening of high-frequency characteristics can be avoided. 
     Further, since the resistor element  35  is connected to the middle portion of each noise cancellation voice coil pattern  22 , the resistance of the noise cancellation voice coil pattern  22  can be increased by the resistor element  35 . Thus, the impedance of the noise cancellation voice coil pattern  22  can be enhanced. As a result, current consumption can be reduced. This can prevent functioning of an overcurrent protection circuit. 
     Next, a fifth embodiment of the present invention will be described. 
       FIG. 9  illustrates the fifth embodiment of the present invention. In the present embodiment, a reinforcement pattern  36  is formed between two adjacent patterns of a sound voice coil pattern  21  and/or a noise cancellation voice coil pattern  22  on a flexible circuit board  20 . 
     The reinforcement pattern  36  is a pattern formed of metal foil such as copper foil or foil of a hard material, for example. The flexible circuit board  20  is reinforced by the reinforcement patterns  36 , and therefore, a transmission speed by a diaphragm  11  is increased. 
     As in each of the above-described embodiments, the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are, in the present embodiment, formed on the flexible circuit board  20 , and therefore, sound of a sound signal can be output with external noise being cancelled out. 
     Moreover, the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are formed on the flexible circuit board  20 , and the reinforcement pattern  36  is formed between two adjacent patterns of the sound voice coil pattern  21  and/or the noise cancellation voice coil pattern  22 . Thus, the surface of the diaphragm  11  can be more hardened. As a result, the transmission speed by the diaphragm  11  can be increased, and high-frequency characteristics can be significantly improved. 
     Note that aspects of the present invention have been described in the above-described embodiments, and the present invention is not limited to these embodiments. 
     For example, in each of the above-described embodiments, the case where the single or double noise cancellation voice coil patterns  22  are formed has been described. However, three or more noise cancellation voice coil patterns  22  may be formed. 
     Moreover, in each of the above-described embodiments, the sound voice coil pattern  21  and the noise cancellation voice coil pattern(s)  22  are formed on one side of the flexible circuit board  20 , but may be formed on both sides of the flexible circuit board  20 , for example. 
     For example, the sound voice coil pattern  21  may be formed on the flexible circuit board  20 , and an insulating layer may be formed to cover the sound voice coil pattern  21 . Then, the noise cancellation voice coil pattern(s)  22  may be formed on the surface of the insulating layer. With this configuration, the sound voice coil pattern  21  and the noise cancellation voice coil pattern(s)  22  may be formed on top of one another. 
     Further, in each of the above-described embodiments, the example where the N-pole and the S-pole of each magnet  13  are formed in the striped pattern and the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are arranged meandering has been described. However, the magnetized state of the N-pole and the S-pole of each magnet  13  can be changed such that the sound voice coil pattern  21  and the noise cancellation voice coil pattern  22  are arranged according to the magnetized state of each magnet  13 . 
     REFERENCE SIGNS LIST 
     
         
           10  speaker device 
           11  diaphragm 
           12  buffer member 
           13  magnet 
           14  holding member 
           20  flexible circuit board 
           21  sound voice coil pattern 
           22  noise cancellation voice coil pattern 
           23  conductive wire drawing portion 
           24  terminal portion 
           25 ,  26  through-hole 
           30  drive circuit 
           31  digital sound source 
           32  sound driver circuit 
           33  microphone 
           34  noise cancellation circuit 
           35  resistor element 
           36  reinforcement pattern