JP2007020024A - Linear motor type loudspeaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hi-fi/high output linear motor type speaker suitable for low-pitched sound reproduction. <P>SOLUTION: A cylindrical magnet 14 having outside dimension slightly smaller than cavity dimension is arranged in the cavity of a cylindrical electromagnet 10. In the magnet 14, the outside and the inside are considered as first and second magnetic poles with the opposite polarity to each other and a diaphragm 16 is attached so as to interrupt airflow in the cavity of the magnet 14. Coil groups other than one coil group among many coil groups 12 is energized so as to perform magnetic levitation of the magnet 14 by making the inside of the electromagnet 10 a magnetic pole with the same polarity as that of the second magnetic pole and one coil group is energized so as to reverse the polarity of the magnetic pole from other coil group. Switching control of direction of current of a plurality of coil groups is performed so as to vibrate the diaphragm 16 by performing reciprocating displacement of the magnet 14 while being magnetically levitated by a magnetic pole relative to polarity reversal in accordance with amplitude variation of an audio signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cylindrical linear motor type speaker having an edgeless / damperless structure, and more specifically, unlike a conventional electrodynamic type acceleration control type speaker, a displacement control type speaker for controlling amplitude displacement itself. It is about.

  Conventionally, as a cylindrical electrodynamic speaker having an edgeless structure, the one shown in FIG. 10 is known (see, for example, Patent Document 1).

  In the speaker shown in FIG. 10, on the base 1, the lower damper support base 2 </ b> A, the lower plate 3 </ b> A, the permanent magnet 4, the upper plate 3 </ b> B, and the upper damper support base 2 </ b> B have their center holes as the central holes 1 </ b> A of the base 1. Laminated and arranged in the aligned state. A cylindrical yoke 8 is disposed so as to surround such a laminate, and a lower end portion of the yoke 8 is connected to an outer peripheral portion of the base 1. Magnetic gaps Ga and Gb are defined between the yoke 8 and the plates 3A and 3B, respectively.

  The coil support 5 includes a lower voice coil 5A and an upper voice coil 5B that are interconnected, and the winding directions of the coils 5A and 5B are opposite to each other. The coil support 5 is placed on the support bases 2A and 2B by the lower damper 6A and the upper damper 6B so that the coils 5A and 5B are arranged in the magnetic gaps Ga and Gb with the coils 5A and 5B offset by half each downward and upward. It is supported. A diaphragm 7 is mounted on the upper portion of the coil support 5. A vertical hole continuing from the central hole 1A of the base 1 to the central hole of the upper damper support 2B is a hole for communicating the space between the diaphragm 7 and the upper damper 6B to the outside air, and is provided in the base 1. The through holes 1a and 1b are holes for communicating the space between the lower damper 6A and the base 1 to the outside air.

When a current is supplied to the coils 5A and 5B according to the audio signal, the coils 5A and 5B are driven in the vertical direction to vibrate the diaphragm 7. For this reason, the audio signal is converted into sound.
JP-A-9-182188

  According to the above-described prior art, the diaphragm 7 is supported only by the coil support 5 (not supported by the yoke 8), and has a so-called edgeless structure. For this reason, the amplitude of the diaphragm 7 is not limited by the edge.

  However, dampers 6A and 6B are provided at two locations, and the amplitude of diaphragm 7 is limited by these dampers. For this reason, bass reproduction is restricted, and it is inevitable that distortion occurs in the sound output of the speaker due to the mechanical nonlinearity of the damper (force-deformation nonlinearity). Further, although the driving range can be expanded by arranging the coils 5A and 5B in the magnetic gaps Ga and Gb in an offset state, the dampers 6A and 6B are driven from the structure in which the coil support 5 and the diaphragm 7 are supported at the center. The range is limited and it is not easy to obtain a high output. In addition, the durability of the dampers 6A and 6B is limited, and it is difficult to stabilize the operation and sound quality over a long period of time.

  The object of the present invention is to provide a high-fidelity, high-output displacement motor-type linear motor speaker suitable for low-frequency reproduction by eliminating such restrictions and non-linear edges and dampers. There is.

The linear motor type speaker according to the present invention is:
A cylindrical electromagnet having an elongated cylindrical body made of a non-magnetic body and a large number of coil groups arranged in parallel along the longitudinal direction of the cylindrical body, and each coil group includes: A coil group including a plurality of coils arranged in the circumferential direction and connected in series in the winding direction; and
A cylindrical magnet disposed in the cavity of the cylindrical body and having an outer dimension slightly smaller than the cavity dimension in a direction perpendicular to the longitudinal direction of the cylindrical body, the inner side and the outer side of the cylindrical magnet having different polarities. The first and second magnetic poles to be
A diaphragm attached to the cylindrical magnet so as to block air flow in the cavity of the cylindrical magnet;
The coil group other than one or a plurality of coil groups among the many coil groups is energized so that the cylindrical magnet is magnetically levitated with the inner side of the cylindrical body having the same polarity as the second magnetic pole. And energizing means for energizing the one or plurality of coil groups so that the polarity of the magnetic poles is reversed with respect to the other coil groups;
In response to the amplitude change of the audio signal, the currents of the plurality of coil groups among the plurality of coil groups are caused to vibrate the diaphragm by reciprocally displacing the cylindrical magnet while the magnetic pole is magnetically levitated by polarity reversal. And a control means for switching and controlling the direction.

  According to the linear motor type speaker of the present invention, since the cylindrical magnet holding the diaphragm is driven to reciprocate in a magnetically levitated state within the cylindrical electromagnet, the diaphragm has an edgeless / damperless structure, and the edge and damper Therefore, it is possible to avoid the limitation of the amplitude due to the non-linearity of the edge and the damper. That is, the diaphragm can be piston-moved by direct control of the position (displacement) from the low range to the high range, and a large volume exclusion amount can be ensured particularly in the low range. For this reason, high-fidelity and high-output sound reproduction is possible, and is particularly suitable for reproduction of large amplitude low sounds.

  In the linear motor type speaker of the present invention, the cylindrical magnet may be composed of an electromagnet, but may be composed of a permanent magnet having a high magnetic flux density. When the electromagnet is used, it is necessary to reduce the influence of the power supply wiring on the movement of the cylindrical magnet and the diaphragm. On the other hand, when the cylindrical magnet is composed of permanent magnets, no wiring is required and the movement of the cylindrical magnet and diaphragm is not subject to any restrictions, but in order to minimize the mass of the diaphragm It is necessary to use a magnet having a light weight and a high magnetic flux density.

  According to the present invention, since the cylindrical linear motor type speaker has an edgeless / damperless structure, the effect of reproducing sound with high fidelity and high output can be obtained. In addition, since there are no edges or dampers, the durability is excellent and the operation and sound quality can be stabilized over a long period of time.

  In addition, the speaker according to the present invention is basically a “displacement amplitude control type”, and the structure restricts the displacement only by the length of the outer tube (cylindrical body). It does not have the disadvantage of low-frequency limitations (such as cone speakers), that is, large attenuation in low frequencies.

That is, the relationship between the peak value ξ of the displacement amplitude and the sound output W in a general cone speaker is generally given by the following equation 1 where R ₀ is the effective radius of the cone and f is the frequency (frequency). It is done.

That is, if W is constant, the necessary amplitude increases in inverse proportion to the square of the frequency f. For this reason, it is necessary to increase the amplitude four times (12 dB) every time one octave is lowered, and in reality, the output is attenuated with a certain slope from the vicinity of the lowest resonance frequency f ₀ toward the lower side (low range). Become. On the other hand, in the case of the speaker according to the present invention, there is no such restriction in the low range, and if the outer tube (cylindrical body) is increased, a very large output can be obtained even in the very low range. On the other hand, in the high region, the non-zero mass (cone paper, diaphragm) needs to be repeatedly displaced many times at a high speed. However, according to the equation (1), the higher region may have a smaller amplitude. This can be realized. As a result, the loudspeaker according to the present invention is based on piston motion without being restricted by amplitude (output) or distortion over the entire band, and is difficult to divide and vibrate even at high frequencies, so that it can provide ideal response frequency characteristics. it can.

As described above, the present invention provides a structure of a sounding body.
(B) If it is slow, it can move a large distance (amplitude) without difficulty even if the mass is not zero.
(B) On the other hand, at a high frequency, on the other hand, it is only necessary to move a small distance, and the rational operation principle that “the acceleration of the diaphragm necessary to obtain a constant output is always constant without depending on the frequency f” is used. It is realized.

  FIG. 1 shows a linear motor type speaker according to an embodiment of the present invention, and a cross section taken along the line A-A 'of FIG. 1 is shown in FIG.

The cylindrical electromagnet 10 includes an elongated cylindrical body 11 made of a nonmagnetic material such as plastic (synthetic resin), for example, and a large number of coil groups 12 arranged in parallel along the longitudinal direction of the cylindrical body 11. Yes. As an example, the cylindrical body 11 has a cylindrical shape with a circular cross section as shown in FIG. 2, but may have a rectangular tube shape with a polygonal shape such as a quadrilateral cross section as shown in FIG. . Each coil group in the many coil groups 12 is arranged along the circumferential direction of the cylindrical body 11 as shown in FIGS. ... consists of a coil group including 12d ... 12a. Here, a description such as “12a... 12b” means that there are many coils between the coils 12a and 12b. FIG. 5 shows a state in which a large number of coils constituting the coil group are connected in series for each of the coil groups C ₀ , RC ₁ , RC ₂ , LC ₁ , and LC ₂ in the large number of coil groups 12. Has been.

  In the cavity of the cylindrical body 11, a cylindrical magnet 14 having an outer dimension slightly smaller than the cavity dimension in the direction orthogonal to the longitudinal direction of the cylindrical body 11 is arranged. As illustrated in FIGS. 2 and 3, the magnet 14 has a cylindrical shape or a rectangular tube shape suitable for the cylindrical body 11. A permanent magnet is used as the magnet 14, but an electromagnet may be used when it is allowed to arrange a power supply wiring. As an example, the polarity of the magnetic pole of the magnet 14 is determined so that the inner side and the outer side become the N pole and the S pole, respectively. However, the polarity of the magnetic pole may be determined conversely. If the length of the cylindrical body 11 is 50 to 100 [cm], the length between both ends of the magnet 14 is 10 to 15 [cm], and the diameter of the magnet 14 shown in FIG. 2 (or the magnet 14 shown in FIG. 3). Can be set to 20 to 30 [cm], and the gap GP between the cylindrical body 11 and the magnet 14 can be set to about 0.1 to 1.0 [mm].

  A vibration plate (diaphragm) 16 is attached to the cylindrical magnet 14 so as to block the air flow in the cavity. The attachment portion of the diaphragm 16 is, for example, the tip of the magnet 14, but may be an intermediate portion in the cavity of the magnet 14. As the material of the diaphragm 16, a light and highly rigid material is used. For example, aluminum alloy, titanium, beryllium, plastic, paper, or the like can be used. As an example, the diaphragm 16 having a convex shape rearward is used, but it may be planar, or may have a convex shape (dome shape) forward.

  When generating a speaker, an initial state is set by flowing currents in opposite directions in one coil group (or a plurality of coil groups) out of the many coil groups 12 and other coil groups than the one coil group. To do. That is, in the initial state, the magnet 14 is magnetically levitated by the magnetic repulsion force with the other coil group other than one coil group having the inner side of the electromagnet 10 as a magnetic pole (S pole) having the same polarity as the S pole outside the magnet 4. In addition, the one coil group is energized so that the polarity of the magnetic poles is reversed with respect to the other coil groups (the inside and the outside of the electromagnet 10 are set to the N pole and the S pole, respectively). Then, in response to changes in the amplitude of audio signals such as audio signals and musical tone signals, the magnet 14 is reciprocally displaced as indicated by the arrow while being magnetically levitated from the initial state by the magnetic pole associated with polarity reversal to vibrate the diaphragm 16. In addition, the current direction of a plurality of coil groups in the many coil groups 12 is switched and controlled. As a result, the audio signal is converted into sound, and sound related to the conversion is radiated from the diaphragm 16. Details of the sound generation operation as described above will be described later with reference to FIGS. Incidentally, the moving parts such as the diaphragm and the magnet are sufficiently light-weighted as described above, and therefore follow the change in the amplitude of the input audio signal without delay.

  When the speaker shown in FIG. 1 is used, various kinds of equipment are provided in the same manner as a normal speaker, so that the efficiency can be increased and the characteristics can be improved by relaxing the restrictions. For example, a horn 18 can be attached to the front end of the cylindrical body 11. As the horn 18, a bending horn or the like may be used. A sealed cabinet 20 in which a sound absorbing material 22 such as glass wool is disposed on the inner surface is attached to the rear end portion of the cylindrical body 11, so that reverse-phase sound from the rear surface (back surface) can be avoided. A bass-reflex cabinet or the like may be mounted instead of the cabinet 20.

  4A to 4F show an example of a method for manufacturing the cylindrical magnet 14. In the process of FIG. 4 (A), a rectangular columnar magnet 14a elongated in the NS direction is subjected to compression processing, and as shown in FIG. 4 (B), left and right orthogonal to the NS direction compared to the NS direction. A prismatic magnet 14b that is slightly elongated in the direction is obtained. In the process of FIG. 4B, the magnet 14b is stretched so that the magnet 14b is further elongated in the left-right direction orthogonal to the NS direction, and the prism 14 is elongated in the left-right direction as shown in FIG. 4C. Magnet 14c is obtained. In the step of FIG. 4C, the magnet 14c is widened so as to widen the magnet 14c in the front-rear direction orthogonal to the NS direction and the left-right direction, and the rectangular shape as shown in FIG. A magnet 14d is obtained.

  Next, in the step of FIG. 4D, the magnet 14d is subjected to a cylindrical process so that the north pole is on the inside, thereby obtaining a magnet 14e having a shape close to a cylinder as shown in FIG. In the step of FIG. 4E, the cylindrical process is further continued so that the ends of the magnets 14e are in contact with each other, and the ends of the magnets 14e are connected to each other as shown in FIG. A magnet 14 is obtained. The magnet 14 has an N pole and an S pole on the inside and outside, respectively. As shown in FIG. 4 (F), a cylindrical magnet 14 as shown in FIG. 4 (F) may be obtained by applying a magnetizing process to a ferromagnetic material that has been cylindricalized in advance.

  FIG. 5 shows an example of a drive circuit for driving the speaker of FIG. 1, and this drive circuit includes an audio signal source 30, an amplifier 31, a small computer 32, a switching circuit group 34, and the like.

  In the small computer 32, an A / D (analog / digital) converter 36, a CPU (central processing unit) 38, a ROM (read only memory) 40, a RAM (random access memory) 42, An output circuit 44 and the like are connected. Audio signals such as audio signals and musical tone signals from the audio signal source 30 are input to the A / D converter 36 via the amplifier 31. In the amplifier 31, the volume, tone color, etc. of the audio signal can be adjusted as appropriate. In the A / D converter 36, the audio signal is converted into amplitude data every predetermined sampling period. The amplitude data for each sample point is obtained by quantizing the input amplitude at the sample point and expressing the quantized amplitude by a digital code having a predetermined number of bits. The CPU 38 executes a driving process as will be described later with reference to FIG. 6 in accordance with a program stored in the ROM 40. In the driving process, some storage areas in the RAM 42 are used as registers. The output circuit 44 includes a large number of output registers respectively corresponding to the large number of coil groups 12 of the electromagnet 10, and a control signal representing 1 or 0 is set in each output register. The switching circuit group 34 includes a large number of switching circuits respectively corresponding to the large number of coil groups 12, and each switching circuit has a large number of coil groups 12 in accordance with control signals from the corresponding output registers in the output circuit 44. An operating current is supplied to the corresponding coil group.

For convenience of explanation, as shown in FIG. 5, the initial position of the outer side of the cylindrical body 11 of the electromagnet 10 as S pole is i = 0, and the position of the N pole arranged on the right side is sequentially set to i = 1, 2,. When the positions of the N poles arranged on the left side of i = 0 are sequentially set to i = -1, -2,..., The positions of i = 0, 1, 2, -1, and -2 in a large number of coil groups 12. The corresponding five coil groups are designated as C ₀ , RC ₁ , RC ₂ , LC ₁ , LC _2, and in the switching circuit group 34, the coil groups C ₀ , RC ₁ , RC ₂ , LC ₁ , LC ₂ are respectively assigned. The corresponding switching circuits are SW ₀ , RSW ₁ , RSW ₂ , LSW ₁ , LSW ₂ . The switching circuits SW ₀ , RSW ₁ , RSW ₂ ..., LSW ₁ , LSW ₂ ... Are supplied with control signals CN ₀ , RCN ₁ , RCN ₂ , LCN ₁ , LCN ₂ . Are supplied to the coil groups C ₀ , RC ₁ , RC ₂ ..., LC ₁ , LC ₂ ... From the switching circuits SW ₀ , RSW ₁ , RSW ₂ ..., LSW ₁ , LSW ₂ . The In the coil groups C ₀ , RC ₁ , RC ₂ ..., LC ₁ , LC ₂ ..., All terminals on the side opposite to the switching circuit side are connected to the ground point (reference potential 0).

In the initial state, the the one coil group C ₀ energized to respectively N and S poles inside and outside of the electromagnet 10, the coil group C ₀ than other coil group RC _1, RC 2 _..., LC ₁ , LC ₂ ... Are energized so that the inside and outside of the electromagnet 10 are the S pole and N pole, respectively, thereby setting the magnet 14 to the initial position i = 0. For this purpose, the control signal CN _{0 is set} to 0 and an operating current is supplied from the switching circuit SW ₀ to the coil group C ₀ based on the negative power supply potential −E, and the control signals RCN ₁ , RCN ₂ ... LCN ₁ , LCN ₂ ... Are all set to ₁ , and the coil groups RC ₁ , RC ₂ ..., LC ₁ , LC ₂ ... Are respectively based on the positive power supply potentials + E from the switching circuits RSW ₁ , RSW ₂ , LSW ₁ , LSW ₂ . Supply operating current. In such an initial state, the S pole of the magnet 14 and the S pole of the electromagnet 10 repel each other in the cylindrical body 11, and when the magnet 14 is displaced in a certain direction, the repulsive force increases and the original position Strong force works in the direction of being pushed back to. For this reason, the inward force and the outward force are balanced in the radial direction, and the magnet 14 is held in a state of being magnetically levitated in the air.

  Next, a driving process in the circuit of FIG. 5 will be described with reference to FIG. The driving process in FIG. 6 starts in response to an on operation of the system power switch or the like.

  In step 50, initial setting processing is performed. The RAM 42 has a first register for setting the amplitude data every time the amplitude data is acquired from the A / D converter 36, and a first register before setting the current amplitude data in the first register. And a second register that receives the previous amplitude data from the first register. In the initial setting process, both the first and second registers are set to 0.

In the initial setting process, the magnet 14 is set to the initial position i = 0 as described above with reference to FIG. The magnet 14 does not necessarily exist at the initial position i = 0 before using the speaker. Further, the speaker of FIG. 1 may be used in a state where the cylindrical body 11 is upright. Therefore, the A / D converter 36 is supplied with an initial setting signal S ₀ as shown in FIG. 7B, thereby enabling the magnet 14 to be set at the initial position i = 0. In FIG. 7B, the horizontal axis represents time t [sec], and the vertical axis represents voltage x [V]. The initial setting signal S ₀ indicates a sinusoidal amplitude change passing through the points P _{1 to} P ₅ . When the initial setting signal S ₀ is the amplitude value 0 at point P _1, it becomes S pole coils C _0, as shown in FIG. 5 on the outside of the tubular body 11, the other coil group other than coils C ₀ is In either case, the outer side of the cylindrical body 11 is an N pole. Assuming that many n coil groups exist on the right side of the position i = 0, the S pole reaches the position i = n when the signal S ₀ reaches a positive peak amplitude value at the point P _2. . When the signal S ₀ has an amplitude value of 0 at the point P ₃ , the S pole returns to the position of i = 0. Assuming that there are a large number of n coil groups on the left side of the i = 0 position, when the signal S ₀ reaches the negative peak amplitude value at the point P ₄ , the S pole is at the i = −n position. To reach. When the signal S ₀ reaches the amplitude value 0 at the point P ₅ , the S pole returns to the position of i = 0.

In such a magnetic pole moving operation, the coil groups other than the one coil group that generates the S pole that moves outside the cylindrical body 11 are both the N pole and S on the outside and inside of the cylindrical body 11, respectively. Since it is a pole, the magnet 14 is in a magnetically levitated state. Wherever the magnet 14 is present in the cylindrical body 11, the magnet 14 is attracted to the N pole that reciprocates inside the cylindrical body 11 and is set to the initial position of i = 0. In the above description, the description of the operation of the output circuit 44 and the switching circuit group 34 according to the output of the A / D converter 36 is omitted, but the operation of these circuits is the same as that described later in steps 52-60. It is. Note that in order to set the magnet 14 to the initial position i = 0, instead of inputting an initial setting signal S ₀ to the A / D converter 36, cylindrical according to the initial setting data such as waveform data stored in ROM40 The N pole movement inside the body 11 (S pole movement outside) may be controlled.

After the initial setting process as described above, in step 52, the data in the first register is transferred to the second register, and the amplitude data is acquired from the A / D converter 36 to obtain the first data. Set to register. In step 54, compares the current indicated by the amplitude data in the amplitude value A _P and the first register of the previous showing amplitude data in the second register and an amplitude value A _C, step 56, the comparison result However, one of the three of A _C = A _P , A _C > A _P and A _C <A _P is determined.

  According to the principle of the present invention, the vibration part (diaphragm, magnet, etc.) is sufficiently light and is determined by the instantaneous amplitude of the input audio signal (that is, the position of the diaphragm is determined by balancing with the inner moving magnet). (The position determined by the coil group) is intended to move without delay, but the following methods are conceivable for controlling an actual vibration part composed of a magnet having a non-zero mass. .

When the comparison result is A _C = _AP , the process proceeds to step 62 without performing any processing. When the comparison result is A _C > A _P , the forward process is performed according to the difference (A _C −A _P ) in Step 58, and then the process proceeds to Step 62. When the comparison result is A _C <A _P , the backward process according to the difference (A _P −A _C ) is performed in Step 60, and then the process proceeds to Step 62. In step 62, it is determined whether there has been an instruction to end the system power switch or the like. If the determination result is negative (N), the process returns to step 52 and the subsequent processing is repeated as described above. As a result, every time amplitude data is acquired from the A / D converter 36, the amplitude data and the previous amplitude data are compared, and if the comparison result is A _C > A _P , the forward process of step 58 performs the comparison result. If A _P > A _C , the backward process of step 60 is performed. If the determination result in step 62 is affirmative (Y), the processing ends.

In the forward process of step 58, the magnet 14 is displaced by the reversed magnetic pole to the right by the number of coil groups corresponding to the difference (A _C −A _P ) from the initial position i = 0. For the sake of simplicity, the difference (A _C −A _P ) corresponds to the number of coil groups to be moved in a one-to-one relationship, but may have a one-to-multiple or a plurality of one-to-one correspondence. In the initial state, an operating current is supplied from the switching circuit SW ₀ to the coil group C ₀ based on the potential −E in response to the control signal CN ₀ = 0, and the magnet 14 has i = 0 as shown in FIG. At the initial position, the tube 11 is sucked by the N pole inside the cylindrical body 11 and is stationary. This state corresponds to the state at time t ₀ in FIG. In FIG. 8, the horizontal axis represents time t, the vertical axis represents voltage V, and potential control states corresponding to the coil groups at positions i = 0, 1, 2, 3, −1, and −2 are shown. .

Difference when _(A C -A _P) is 1, the output register corresponding to the control signal _CN 0, RCN ₁ to the control signal CN ₀ to 1 and controlling signal RCN ₁ 0 in the output circuit 44 Change the contents. In the switching circuit SW ₀ , the potential is smoothly switched from −E to + E as indicated by a waveform W ₀ in FIG. 8 in response to the control signal CN ₀ = 1, and in the switching circuit RSW ₁ , the control signal RCN ₁ = 0. depending smoothly switched to -E potential as indicated by the waveform W ₁ in FIG. 8 from + E to. In the state of time t ₁ in FIG. 8, the operation current is supplied to the coil groups C ₀ based on the potential + E, the operating current is supplied to the coil group RC ₁ based on the potential -E. That is, the direction of the current is smoothly switched in any of the coil groups C ₀ and RC ₁ toward time t ₁ . For this reason, in the coil groups C ₀ and RC ₁ , the polarities of the magnetic poles are inverted to N and S on the outside of the cylindrical body 11, and the S pole on the outside of the cylindrical body 11 is i = from the initial position of i = 0. Move to position 1. As a result, the magnet 14 is attracted to the N pole inside the cylindrical body 11 and advances (displaces) to the position of i = 1 as indicated by the broken line in FIG. Each switching circuit in the switching circuit group 34 is configured using, for example, a time constant circuit having a discharge waveform that changes from the potential −E to the potential 0 and a charging waveform that changes from the potential 0 to the potential + E. Is possible.

When the difference (A _C −A _P ) is a value larger than 1 (the change in input amplitude is steep), the current switching process similar to that described above for the coil groups C ₀ and RC ₁ is performed at the initial position i = 0. To the coil groups in the right range by the number of coil groups corresponding to the difference value. As an example, assuming that the difference value is 2, the same current switching process as described above is sequentially performed on the coil groups C ₀ and RC ₁ and the coil groups RC ₁ and RC ₂ . In this case, the coil group C _0, RC _1, the direction of the current is smoothly switched at any of coils C _0, RC ₁ toward the time t ₁ of FIG. 8 in the same manner as described above.

At time t _{1 in} FIG. 8, the contents of the output registers corresponding to RCN ₁ and RCN ₂ are changed so that the control signal RCN _{1 is set} to 1 and the control signal RCN _{2 is set} to 0 in the output circuit 44. In the switching circuit RSW ₁ , the potential is smoothly switched from −E to + E as indicated by a waveform W ₁ in FIG. 8 in response to the control signal RCN ₁ = 1, and in the switching circuit RSW ₂ , the control signal RCN ₂ = 0. depending smoothly switched to -E potential as indicated by the waveform W ₂ in FIG. 8 from + E to. In the state of time t ₂ in FIG. 8, the operation current is supplied to the coils RC ₁ based on the potential + E, the operating current is supplied to the coil groups RC ₂ based on the potential -E. That is, the direction of current is smoothly switched in both coil groups RC ₁ and RC ₂ toward time t ₂ . For this reason, in the coil groups RC ₁ and RC ₂ , the polarity of the magnetic pole is inverted to N and S on the outside of the cylindrical body 11, and the S pole on the outside of the cylindrical body 11 is i = from the initial position of i = 0. Move to position 2. As a result, the magnet 14 is attracted by the N pole inside the cylindrical body 11 and advances to the position of i = 2.

When the difference value is 3, the same current switching operation as described above is performed up to the coil group of i = 3. In the state of time t ₃ in FIG. 8, the operating current based on the potential + E, as shown by the waveform W ₂ is supplied to the coil groups RC 2 _(i = 2), the coils of the position of i = 3 the operating current is supplied based on the potential -E as shown by the waveform W _3. Therefore, in this case, the magnet 14 moves forward to the position of i = 3. As described above, when the displacement amount of the magnet 14 is increased as the difference value is increased, the diaphragm 16 can be vibrated following a steep change in the input amplitude.

FIG. 7A shows a signal x = x (t) whose amplitude increases linearly as an example of an input signal input to the A / D converter 36. According to the driving process described above, the magnet 14 moves to the right at a constant speed corresponding to the difference value in accordance with the input signal x = x (t). The switching waveforms such as W _{1 to} W ₃ shown in FIG. 8 have the best linearity and operate smoothly with respect to the input signal x as shown in FIG. 7A (the distortion is minimized). Adjusted to

In the backward process of the step 60, the initial position i = 0 from the difference value _(A P -A _C) Number of the group corresponding to only the left side to displace the magnet 14 by reversing the magnetic pole to the (i = -1, -2 ... position) . A specific operation is performed in the same manner as described above for the forward process in step 58 using the control signals CN ₀ , LCN ₁ , LCN ₂ ... And the switching circuits SW ₀ , LSW ₁ , LSW ₂ . Details of such an operation are self-evident from the description of the forward process, and thus the description thereof is omitted. The magnet 14 is reciprocated in response to a change in the amplitude of the audio signal by the forward process in step 58 and the reverse process in step 60, and the diaphragm 16 vibrates, so that the audio signal is converted into sound.

  According to the linear motor type speaker described above, since there is no edge or damper that fixedly supports the diaphragm 16, there is no amplitude limitation due to the edge or damper or distortion due to non-linearity, and high-fidelity reproduction is possible from low to high frequencies. become. In addition, the maximum amplitude of the diaphragm 16 depends only on the length of the electromagnet 10, and a large amplitude operation is possible, so that a high output can be obtained. In addition, since the magnet 14 holding the diaphragm 16 is reciprocated in a magnetic levitation state that is not in contact with the electromagnet 10, various distortions associated with edges and dampers can be eliminated. Furthermore, since it has a simple structure with no edges or dampers, it has durability and can stabilize operation and sound quality over a long period of time.

  In the above linear motor type speaker, if it is possible to generate a large magnetic force by increasing the current flowing through each coil group of the electromagnet 10 or increasing the magnetic flux density by configuring the magnet 14 with a neodymium alloy or the like, The transient response of the diaphragm 16 can be further improved. Further, if the change in the position of the reversal magnetic pole in the electromagnet 10 is increased, the diaphragm 16 can move in a large range and can generate a large amplitude sound. Of course, the polarities of the magnetic poles shown in FIGS. 1, 4 and 5 for the electromagnet 10 and the magnet 14 may be opposite to those shown in the figure.

  FIG. 9 shows an installation example of the linear motor type speaker according to the present invention, and the same parts as those in FIG.

  In the example of FIG. 9, a conduit (duct) 24 is attached to the rear end portion of the electromagnet 10, and the conduit 24 communicates with the space under the floor through a hole provided in the floor 26. As another example, the conduit 24 may be communicated with another chamber through a hole provided in the wall 28. In any example, it is possible to prevent the speaker sound generated from behind the electromagnet 10 from coming in front of the electromagnet 10 and deteriorating the response frequency characteristics.

It is a partial side sectional view showing a linear motor type speaker according to an embodiment of the present invention. It is sectional drawing which follows the A-A 'line of FIG. It is sectional drawing of the speaker which concerns on a modification. (A)-(F) are all perspective views which show the process process in the manufacturing method of a cylindrical magnet. It is a circuit diagram which shows a speaker drive circuit. 6 is a flowchart showing the flow of drive processing in the circuit of FIG. 5. (A) and (B) are waveform diagrams showing an input signal and an initial setting signal, respectively. It is a signal waveform diagram for demonstrating the magnetic pole movement operation | movement in the circuit of FIG. It is sectional drawing which shows the example of speaker installation. It is sectional drawing which shows the conventional cylindrical electrodynamic speaker.

Explanation of symbols

10: cylindrical electromagnet, 12a to 12d: coil, 12, C ₀ , RC ₁ , RC ₂ , LC ₁ , LC ₂ : coil group, 14: cylindrical magnet, 16: diaphragm, 18: horn, 20: cabinet 22: sound absorbing material, 24: conduit, 26: floor, 28: wall, 30: audio signal source, 31: amplifier, 32: small computer, 34: switching circuit group.

Claims (2)

A cylindrical electromagnet having an elongated cylindrical body made of a non-magnetic body and a large number of coil groups arranged in parallel along the longitudinal direction of the cylindrical body, and each coil group includes: A coil group including a plurality of coils arranged in the circumferential direction and connected in series in the winding direction; and
A cylindrical magnet disposed in the cavity of the cylindrical body and having an outer dimension slightly smaller than the cavity dimension in a direction perpendicular to the longitudinal direction of the cylindrical body, the inner side and the outer side of the cylindrical magnet having different polarities. The first and second magnetic poles to be
A diaphragm attached to the cylindrical magnet so as to block air flow in the cavity of the cylindrical magnet;
The coil group other than one or a plurality of coil groups among the many coil groups is energized so that the cylindrical magnet is magnetically levitated with the inner side of the cylindrical body having the same polarity as the second magnetic pole. And energizing means for energizing the one or plurality of coil groups so that the polarity of the magnetic poles is reversed with respect to the other coil groups;
In response to the amplitude change of the audio signal, the currents of the plurality of coil groups among the plurality of coil groups are caused to vibrate the diaphragm by reciprocally displacing the cylindrical magnet while the magnetic pole is magnetically levitated by polarity reversal. And a linear motor type speaker provided with control means for switching and controlling the direction of the speaker.   The linear motor type speaker according to claim 1, wherein the cylindrical magnet is made of a permanent magnet.

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