JP2011030013A - Moving-magnet type speaker and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin moving-magnet type speaker by providing a quantitative guideline about a weight of a magnetic circuit and by suppressing an increase in inductance while sustaining a magnetic flux density of a voice coil. <P>SOLUTION: The moving-magnet type speaker 10 generates a sound wave by the vibration of a vibrating plate 1 having a magnetic circuit comprising a magnet 5 and a magnetic body 4 through the magnetic circuit in response to the magnetic field generated by a voice coil 6 to which a voice current flows. The magnetic circuit is structured so that the total weight of the magnetic circuit is 0.5 to 2.0 times to the total weight of an added weight and a weight of the vibrating plate 1. The voice coil 6 is structured so that it is divided into a plurality of components and its inductance is decreased, and a decrease in its sound current in high register is prevented. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a movable magnet type speaker among electrodynamic speakers and a method for manufacturing the same.

  As a standard configuration of the above electrodynamic speaker, a magnetic circuit composed of a magnet and a yoke is fixed to the frame, and a diaphragm on which the voice coil is fixed is attached to the frame so as to vibrate. 2. Description of the Related Art There is known a movable linear speaker that outputs sound by supplying a sound current and generating a driving force to vibrate a diaphragm with respect to a magnet.

In general, “efficiency” indicating a ratio of supplied audio current converted into sound energy is known as an index representing the characteristics of a speaker. Regarding the efficiency of the above-described conventional movable-line-ring type speaker, for example, it is explained as follows in the section on efficiency of 8.4.3 in Non-Patent Document 1. In other words, the efficiency η of the conventional movable coil type speaker, the vibrating plate side radiation resistance R _s, B magnetic flux density, the voice coil winding length l, the angular frequency of the sound omega, the voice coil mass m _c,
The vibration system mass excluding voice coil m _d, when the vibrating plate on one side additional mass M _s, the voice coil electrical resistance was r _e, is shown as number 1.

In Equation 1, the voice coil winding length l is because they rely on negative relative to the voice coil mass m _c, is not a clear relationship between efficiency η and the voice coil mass m _c in this state. Therefore, the voice coil density [rho _c, the voice coil winding cross-sectional area S, with the voice coil conductivity and kappa, voice coil using a _{m c = ρ c Sl, r} e = l / (κS) the relationship When the winding length l is eliminated, Equation 1 is transformed into Equation 2.

Thus, maximum efficiency is when the value of the resulting expression by partially differentiated by the efficiency of the number 2 eta voice coil mass m _c is zero, i.e., as shown in Equation 3, the voice coil mass m _c but the maximum efficiency is obtained when equal to the sum of the vibration system mass m _d other than the voice coil and the diaphragm added mass 2M _s.

For example, if an example in a movable wire ring speaker having an actual aperture of about 16 cm is shown, m _c = 2 g, m _d = 5 g, and M _s = 1.7 g. When these values are compared with Equation 3, Rather than m _c = m _d + 2M _s , m _c <m _d + 2M _s . This is because, if the voice coil mass m _c increases, the pole spacing is the magnetic flux density B decreases increases because it is necessary to increase the magnet to compensate for the decrease. Further, it is explained that the diaphragm divides and vibrates at the time of high sound output and the substantial value of m _d + 2M _s decreases.

In addition to the “efficiency”, “voice coil inductance” that is proportional to the substantially square of the voice coil winding length is known as an index representing the characteristics of the speaker. As for the voice coil inductance of the conventional movable wire ring type speaker, an example is shown in the section of electrical impedance characteristics and equivalent circuit of 8.4.2 in Non-Patent Document 1. According to this, when the frequency of the sound current of 10kHz electrical resistance _{r e} of the voice coil is about 8ohms, inductance _{l e} is about 0.6MH.

Assuming that the speaker exemplified in this section is for a general band, the inductance l _e that does not hinder the generation of at least about 10 kHz treble needs to be about 0.6 mH or less. Since the electrical resistance r _e of the voice coil it is not limited to 8ohms, evaluation of the inductance l _e of the voice coil rather than by its raw value, the electrical time constant defined by the ratio of the electrical resistance r _e It should be evaluated by τ _e = l _e / r _e or the crossover frequency f _c = 1 / (2πτ _e ) derived from the electrical time constant τ _e . In this example, the crossover frequency _{f c} is approximately 2 kHz.

  Further, for example, Non-Patent Document 2 describes a permanent magnet magnetic circuit used for an electrodynamic speaker.

  As another configuration of the electrodynamic speaker, the magnetic circuit and the voice coil are exchanged with respect to the movable wire ring speaker, and the magnetic circuit is fixed to the diaphragm and the voice coil is fixed to the frame. A movable magnet type speaker is known. For example, Patent Documents 1 to 3 describe a movable magnet type speaker.

  The advantage of the movable magnet type speaker is that the voice coil is not attached to the diaphragm unlike the movable wire ring type speaker, so there is no possibility that the tinted wire of the voice coil always vibrates together with the diaphragm and breaks. . However, as can be seen from the fact that Non-Patent Document 3 does not describe the movable magnet type speaker, the movable magnet type speaker is not yet in a general state.

Japanese Patent No. 293609 Japanese Patent No. 1223828 Japanese Patent No. 3421654

Masaaki Kawamura "Introduction to Electroacoustic Engineering" Shoshodo Mitsuyoshi Okawa "Introduction to Permanent Magnet Magnetic Circuit" General Electronic Publisher Patent Search Guidebook-Small Speaker Technology-JPO http://www.jpo.go.jp/shiryou/s_sonota/pdf/pat_guidebook/h19_12.pdf

  When trying to realize a movable magnet type speaker having the above advantages, there are mainly the following three problems. The first problem is a decrease in efficiency. In the conventional movable wire ring type speaker, the mass of the magnetic circuit occupies most of the mass of the speaker. For example, for a diaphragm having a diameter of about 16 cm, a magnetic circuit of about 400 g or more is often used. For this reason, in a movable magnet type speaker, simply exchanging the mounting position of the magnetic circuit and the voice coil of the conventional movable ring type speaker increases the mass of the vibrating diaphragm and the magnetic circuit. The mismatch becomes large and the efficiency becomes very low. Therefore, only a small sound could be output with respect to the supplied audio current.

  As a method for solving the first problem, a method of reducing the size and weight of the magnetic circuit from that of the movable ring type speaker is conceivable. However, if the magnetic circuit is simply reduced in size, it becomes difficult to link the voice coil in a state in which the magnetic flux is converged by the yoke and the magnetic flux density is sufficiently increased, and the efficiency of the speaker is lowered. was there.

  In order to solve such problems, it is conceivable to increase the product of the magnetic flux density B and the voice coil winding length l in order to increase the efficiency of the electrodynamic speaker. Therefore, a method for reducing the magnetic circuit size and compensating for the decrease in the magnetic flux density B associated with the size reduction by increasing the voice coil winding length l can be considered. In this method, the inductance of the voice coil increases. However, there was a third problem that it was difficult to produce a high tone.

  From this point of view, in Patent Document 1, the main diaphragm and another diaphragm for producing a high sound are provided side by side with a magnetic circuit shared. However, in this solution, the structure of the speaker is complicated, and there is a possibility that the size of the speaker increases in the vibration direction. Further, in the configuration disclosed in Patent Document 2, the configuration of the core 10 is complicated, and there is a risk of increasing the size in the vibration direction. In the configuration of Patent Document 3, there is a problem that the moving magnet does not enter the fixed coil, or the length of the part that has entered is insufficient, and thus the diaphragm cannot be driven efficiently. As described above, it has been difficult to solve the first to third problems and realize a movable magnet type speaker. In particular, it has been difficult to realize a thin movable magnet type speaker with a simple configuration.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a movable magnet type speaker whose efficiency is improved by giving a quantitative guide regarding the mass of a magnetic circuit, and a method for manufacturing the same. To do.

  In order to achieve the above object, a movable magnet type speaker according to the present invention comprises a magnet and a magnetic material (for example, the ferromagnetic thin plate 4 in the embodiment) according to a magnetic field generated by a voice coil through which an audio current flows. A diaphragm having a magnetic circuit is configured to vibrate through the magnetic circuit to generate a sound wave, and the total mass of the magnetic circuit is 0. 0 relative to the total mass of the additional mass and the mass of the diaphragm. 5 to 2.0 times.

  In this case, the movable magnet type speaker includes a frame, and the voice coil is divided into a plurality of parts to reduce inductance and prevent a decrease in voice current in a high frequency range, and different positions in the frame. And the diaphragm is attached to the frame so as to be able to vibrate in the axial direction of the voice coil with a predetermined gap in the axial direction of the voice coil. It is preferable that a circuit is fixed to the diaphragm and faces the voice coil.

  The voice coil is a solenoid coil, and the magnet has a columnar shape and is magnetized in the longitudinal direction thereof, and one end face is fixed to the magnetic body and is magnetically connected to the magnetic body, and the other end face is Preferably, the voice coil is configured to be inserted into a hollow portion of the voice coil to be magnetically coupled to the voice coil.

  Further, the magnet preferably has a dimensional ratio of 1 or more, and the magnetic body extends outward from the outer shape of the voice coil along a plane perpendicular to the longitudinal direction of the magnet. .

  In order to achieve the above object, according to the method of manufacturing a movable magnet type speaker according to the present invention, a diaphragm having a magnetic circuit made up of a magnet and a magnetic material in accordance with a magnetic field generated by a voice coil through which an audio current has passed is provided. A method of manufacturing a movable magnet type speaker that generates a sound wave by vibrating through a circuit, wherein the total mass of the magnetic circuit is 0.5-2 with respect to the total mass of an additional mass and a mass of the diaphragm. A first magnetic circuit manufacturing process of 0.times., A voice coil manufacturing process for dividing the voice coil into a plurality of parts to reduce inductance and prevent a decrease in voice current in a high sound range, and the magnet. A second magnetic circuit formed so as to have a ratio of 1 or more and extending the magnetic body to the outside of the outer shape of the voice coil along a plane perpendicular to the longitudinal direction of the magnet Manufacturer With the door.

  In the movable magnet type speaker according to the present invention, the total mass of the magnetic circuit is 0.5 to 2.0 times the total mass of the additional mass and the mass of the diaphragm. By constructing based on the quantitative guideline regarding the mass of the magnetic circuit, it is possible to improve the efficiency by eliminating the mismatch between the vibration plate and the mass of the magnetic circuit and the load air. Can do. Therefore, it is possible to realize a movable magnet type speaker that can output a sufficiently loud sound that can be heard with respect to the supplied audio current.

  The voice coil is preferably divided into a plurality of parts to reduce inductance and prevent a decrease in voice current in the high sound range. As described above, in the past, the product of the magnetic flux density B and the voice coil winding length l was increased by increasing the voice coil winding length l in order to increase the efficiency. Inevitably occurred, and it was difficult for high-pitched sounds to occur. On the other hand, when the voice coil is divided into a plurality of parts as described above, the inductance can be reduced while maintaining the product of the magnetic flux density B and the voice coil winding length l. A decrease in current can be prevented.

  The magnet has a columnar shape and is magnetized in the longitudinal direction. One end face is fixed to the magnetic body and magnetically connected to the magnetic body, and the other end face is inserted into the hollow portion of the voice coil to be magnetically coupled. It is preferable that it is comprised so that it may carry out. When a voice current is supplied to the voice coil 6, the strongest magnetic field is generated in the central portion on the central axis. However, when configured as described above, the magnetic pole of the magnet exists in the region where the strongest magnetic field is generated. An open end face can be positioned. Therefore, it is possible to further improve the efficiency of the movable magnet type speaker 10 by causing the strongest magnetic field to act on the magnet to vibrate.

  Furthermore, it is preferable that the dimensional ratio of the magnet is 1 or more, and the magnetic body extends outside the outer shape of the voice coil. When configured in this manner, the magnetic force lines of the magnet can be sufficiently guided outward by the magnetic material. For example, even at the peripheral end of the voice coil, the induced magnetic force lines are linked to the voice coil. Large electromagnetic force can be generated.

  The manufacturing method of the movable magnet type speaker according to the present invention is the first magnetic circuit manufacturing in which the total mass of the magnetic circuit is 0.5 to 2.0 times the total mass of the additional mass and the mass of the diaphragm. A voice coil manufacturing process in which a voice coil is divided into a plurality of parts to reduce inductance, a magnet is formed so that a dimensional ratio thereof is 1 or more, and a magnetic body is outside an outer shape of the voice coil of the magnet And a second magnetic circuit manufacturing process for extending the distance. Since the movable magnet type speaker is manufactured through the above three manufacturing steps, the movable magnet type speaker is capable of outputting a high sound range by reducing the inductance while maintaining the magnetic flux density of the voice coil, and improving the efficiency. A speaker can be realized.

It is a top view of the movable magnet type speaker concerning the present invention. It is sectional drawing which shows the II-II part in FIG. It is a graph which shows the relationship between the efficiency of the said movable magnet type speaker, and mass ratio (beta). The mass ratio β = the mass of the diaphragm including the magnetic circuit mass / additional mass.

  Hereinafter, a movable magnet type speaker 10 according to an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the arrow directions shown in the drawings are defined as front and rear, left and right, and up and down.

  First, the configuration of the movable magnet type speaker 10 will be described with reference to FIGS. Note that the movable magnet type speaker 10 described below is an example in which the present invention is applied to a so-called full range type speaker that handles the entire sound range, but the present invention is not limited to this and is a so-called tweeter that handles the high sound range, or a low sound range. It can also be applied to woofers that are in charge.

  The movable magnet type speaker 10 includes a ring-shaped fixed support portion 20 and a disk-shaped vibrating portion 30 attached to the front side of the fixed support portion 20. In addition, the shape of the fixed support part 20 and the vibration part 30 is not limited to the said shape, Other shapes may be sufficient.

  The fixed support portion 20 includes a frame 3 formed in a ring shape, four solenoid-type voice coils 6, and a voice coil lead wire 8. In the frame 3, four voice coil insertion holes 7 penetrating in the front-rear direction are formed. The voice coil 6 is formed so that its inner diameter is larger than the outer diameter of a magnet 5 described later. One voice coil 6 is embedded in each of the voice coil insertion holes 7 with its central axis facing front and rear, and is bonded and fixed to the voice coil insertion hole 7. With this configuration, the magnet 5 inserted back and forth with respect to the voice coil 6 can vibrate back and forth along the central axis of the voice coil 6.

  The four voice coils 6 embedded in the frame 3 are connected in series by voice coil lead wires 8 embedded in a groove (not shown) provided on the rear surface of the frame 3. The end portion of the voice coil lead wire 8 is drawn to the outside as a speaker input 9, and this speaker input 9 is electrically connected to an external voice current output device (not shown). With this configuration, the same voice current is supplied to each of the four voice coils 6 via the voice coil lead wire 8.

  The vibration unit 30 includes a disk-shaped vibration plate 1, an elastic body 2 bonded in the vicinity of the periphery of the vibration plate 1, a ferromagnetic thin plate 4 provided adjacent to the elastic body 2, and a magnet 5. . In the following description, the ferromagnetic thin plate 4 and the magnet 5 are collectively referred to as a magnetic circuit. In FIGS. 1 and 2, four elastic bodies 2, four ferromagnetic thin plates 4 and four magnets 5 are used in correspondence with the four voice coils 6, respectively.

  The diaphragm 1 can be formed using various materials. However, in order to improve the efficiency of the movable magnet type speaker 10, it is preferable that the diaphragm 1 be formed using a material that is as light as possible and that does not deform during vibration. As shown in FIG. 2, the elastic body 2 is formed in a cylindrical shape using an elastically deformable material. For example, a resin tube can be used.

  The elastic body 2 is bonded to the vibration plate 1 and the frame 3 in a state where the elastic body 2 is held back and forth, that is, the vibration plate 1 is attached to the frame 3 via the elastic body 2. The thickness corresponding to the diameter of the elastic body 2 is formed so that the open end face of the magnet 5 is located at the center in the front-rear direction on the central axis of the voice coil 6 when the diaphragm 1 is stationary. ing. The open end face of the magnet 5 corresponds to the rear end face of the magnet 5 in FIG. As the elastic body 2, it is also possible to use a so-called deformable edge used for a general speaker.

  The ferromagnetic thin plate 4 is formed in a disc shape, and its diameter is larger than the outer diameter of the voice coil 6. Further, it is desirable that the thickness of the ferromagnetic thin plate 4 is such that the magnetic flux does not leak from the surface opposite to the surface on which the magnet 5 is fixed. In that respect, the thicker the front and rear thickness of the ferromagnetic thin plate 4 is, the better. However, considering that the vibrating portion 30 is lightly formed, it is not practical to make it extremely thick, and an optimum value is selected. The ferromagnetic thin plate 4 formed in this way is adhered and fixed to the rear surface of the diaphragm 1 so as to be adjacent to the elastic body 2 in the vicinity of the periphery of the diaphragm 1.

  The magnet 5 is formed in a columnar shape and is magnetized in an axial direction corresponding to the front-rear direction in FIG. 2 so that the dimensional ratio represented by the front-rear height / diameter is approximately 1. The magnet 5 is placed on and fixed to the ferromagnetic thin plate 4 so that the center of the front end face of the magnet 5 coincides with the center of the ferromagnetic thin plate 4. The total mass of the four ferromagnetic thin plates 4 and the four magnets 5 formed in this way is set to be substantially the same as the mass of the diaphragm 1. In the present embodiment, for example, the case where the vibration plate 1 is about 5 g, one ferromagnetic thin plate 4 is about 0.5 g, and one magnet 5 is about 0.75 g is illustrated.

  Here, as with the ferromagnetic thin plate 4 and the magnet 5, the elastic body 2 can be cited as a member that vibrates together with the vibration plate 1. However, since the entire elastic body 2 does not vibrate, Mass is negligible. The magnet 5 is not limited to the configuration with the dimensional ratio of approximately 1, and may have a configuration with the dimensional ratio of approximately 1 or more. From such a configuration, the magnet 5 and the diaphragm 1 fixed to the magnet 5 are positioned so as to vibrate back and forth along the central axis of the voice coil 6.

  Up to here, the configuration of the movable magnet type speaker 10 has been described. Hereinafter, the operation of the movable magnet type speaker 10 according to the present invention will be described.

  When a voice current is supplied from the outside via the speaker input 9, this voice current is inputted to each of the voice coils 6 via the voice coil lead wire 8. In the voice coil 6, a magnetic field corresponding to the input voice current is generated, and electromagnetic force acts on the ferromagnetic thin plate 4 and the magnet 5 by this magnetic field. By doing so, the ferromagnetic thin plate 4, the magnet 5 and the diaphragm 1 are integrally vibrated back and forth to generate sound waves. When the diaphragm 1 is displaced forward, the elastic body 2 is stretched back and forth while adhering to the diaphragm 1 and the frame 3, and the diaphragm 1 is returned to the stationary position shown in FIG. On the other hand, a force to return backwards is applied.

  As described above, when a voice current is input and a magnetic field is generated in the voice coil 6, the strongest magnetic field is generated in the central portion on the central axis of the voice coil 6, and the magnetic pole of the magnet 5 is centered on this position. Is configured to vibrate the open end face in the back and forth direction. Therefore, the efficiency of the movable magnet type speaker 10 can be improved.

  In the conventional movable ring speaker, it is difficult to efficiently radiate Joule heat generated in the voice coil because of the structure in which the voice coil is attached to the vibration side. On the other hand, in the movable magnet type speaker 10 to which the present invention is applied, the Joule heat generated in the voice coil 6 is transmitted to the frame 3 which is in close contact with the outer periphery of the voice coil 6 and is dissipated. It is possible to prevent the coil 6 from being exposed to high temperatures. Furthermore, by forming the frame 3 using a material having a high heat transfer coefficient, heat can be transferred to the frame 3 more efficiently and radiated.

  Further, in the conventional movable wire ring type speaker, there is a possibility that the tinsel wire may be cut as described in the background art, but such a situation does not occur in the movable magnet type speaker 10 and the failure due to the disconnection is reduced. Stable operation is ensured. Furthermore, in the conventional movable wire ring type speaker, a relatively large magnet is required. However, in the movable magnet type speaker 10, the magnetic circuit is configured in a small size to save resources. The structure is considered.

  Up to here, the operation of the movable magnet type speaker 10 has been described. Hereinafter, three characteristic configurations of the movable magnet type speaker 10 according to the present invention will be described in detail.

  First, the first characteristic configuration of the movable magnet type speaker 10 will be described. The first characteristic configuration described below is that the magnetic circuit is composed of the ferromagnetic thin plate 4 and the magnet 5 described above, and the effects of this configuration will also be described.

  Since the magnet 5 used in the movable magnet type speaker 10 is a columnar magnet having a dimensional ratio of 1 or more as described above, according to the description of the single magnet section of 2.3.1 in Non-Patent Document 2, there are 3 or more. The permeance coefficient is obtained. As a result, for example, if a rare earth magnet having a residual magnetic flux density of 1T is used, an operating point magnetic flux density of 0.7T or more can be obtained. However, the surface magnetic flux density is lower than this. In the movable magnet type speaker 10, it is difficult to sufficiently converge the magnetic flux using the large-sized ferromagnetic thin plate 4 due to the mass-related conditions, and thus a shape that can obtain a high magnetic flux density with the magnet 5 alone is suitable. Yes.

  Further, the maximum amplitude of the diaphragm 1 in the movable magnet type speaker 10 is limited to the height of the front and rear of the magnet 5 due to its structure, but the magnet 5 having the same volume and having a large front and rear height of 1 or more. By using this, a sufficient maximum amplitude can be secured. Furthermore, since the magnetic circuit of the movable magnet type speaker 10 has a configuration in which the ferromagnetic thin plate 4 as a yoke is added to the single magnet 5, it is possible to obtain a higher magnetic flux density.

  Further, in the movable magnet type speaker 10, only the component extending radially in the radial direction of the magnet 5 among the lines of magnetic force generated by the magnetic circuit is linked to the voice coil 6, and the axis corresponding to the front-rear direction in FIG. Generate electromagnetic force in the direction. Therefore, the shape of the ferromagnetic thin plate 4 is preferably a shape that generates more magnetic lines of force in the magnet 5 in the radial direction and generates a large electromagnetic force from the viewpoint of efficiency. Considering this point, in the movable magnet type speaker 10, the diameter of the ferromagnetic thin plate 4 is formed larger than the outer diameter of the voice coil 6. Thereby, the magnetic lines of force can be sufficiently induced in the radial direction of the magnet 5, so that, for example, even at the peripheral end portion of the voice coil 6, the induced magnetic lines of force are linked to the voice coil 6 to generate a large electromagnetic force. Can be generated.

  Further, in the movable magnet type speaker 10, since the ferromagnetic thin plate 4 is formed in a thin plate shape, when the ferromagnetic thin plate 4 is fixed to the vibration plate 1, it protrudes in the front-rear direction around the magnet 5. There is no composition to do. Therefore, it is possible to arrange the frame 3 and the voice coil 6 densely in the space around the magnet 5. Further, as described above, the voice coil 6 is embedded in the frame 3, but since the ferromagnetic thin plate 4 is formed in a thin plate shape, it is stronger than the frame 3 when the diaphragm 1 vibrates. There is no possibility of interference with the magnetic thin plate 4. For this reason, the frame 3 can be formed in a flat plate shape, and the entire movable magnet type speaker 10 can be easily thinned in the front-rear direction which is the vibration direction.

  Further, the movable magnet type speaker 10 has a configuration in which the magnetic force lines can be sufficiently guided in the radial direction of the magnet 5 by the ferromagnetic thin plate 4, so that the magnet 5 and the voice coil are compared with the conventional configuration. Even when the gap with 6 is set large, sufficient efficiency can be ensured. As described above, when the gap between the magnet 5 and the voice coil 6 is set large, the maintenance work of the movable magnet type speaker 10 is facilitated.

  The first characteristic configuration of the movable magnet type speaker 10 has been described above. Next, a second characteristic configuration of the movable magnet type speaker 10 will be described.

  The second characteristic configuration described below is based on the total mass of the magnetic circuit with respect to the total mass of the additional mass that is the mass of air that vibrates together with the vibration of the diaphragm 1 and the mass of the diaphragm 1. It is the point which is comprised so that it may be 0.5 times or more and 2.0 times or less, and the effect by this structure is also demonstrated collectively. In this embodiment, it is configured to be 1.0 times. The additional mass is the mass of air in a substantially hemispherical area in contact with the diaphragm 1 and is an amount proportional to the cube of the radius of the diaphragm 1.

First, it is fixed to the diaphragm 1, since a magnetic circuit instead of the voice coil, the number 1, it is necessary to replace the voice coil mass m _c a magnetic circuit mass m _m. By performing this replacement, the efficiency η of the movable magnet type speaker 10 is expressed by Formula 4.

Here, to find the optimum value of the magnetic circuit mass m _m, it is necessary to introduce a relationship between the voice coil winding length l and the magnetic circuit mass m _m. This relationship is not as obvious relationship between the voice coil winding length l and the voice coil mass m _c in a conventional movable coil type speaker, it can be considered as follows. If a lightweight magnetic circuit capable of interlinking a high magnetic flux density with a voice coil and the optimum shape of the voice coil are determined, the similarity between the magnetic circuit and the voice coil when changing the size thereof is determined. If the dimension is enlarged or reduced while maintaining the optimum shape, the optimum shape is maintained and the desired magnetic flux density is not reduced.

  What has been described above can also be understood from the fact that the magnetic circuit and the voice coil in the movable-wire-ring type loudspeaker that is currently commercially available and mainstream are almost similar regardless of the size. In place of the method of changing the sizes of the magnetic circuit and the voice coil while maintaining the similar relationship as described above, a method of providing a plurality of pairs of magnetic circuits and voice coils having the same dimensions is also possible. Even when this method is adopted, the optimum shape is maintained and the magnetic flux density does not change.

Regardless of which method is employed, the mass of the magnetic circuit and the mass of the voice coil are in a proportional relationship. Therefore, the α and proportional constant, it is possible to represent the magnetic circuit mass m _m as in equation 5.

  By eliminating the voice coil winding length l from equation (4) using equation (5), equation (6) is obtained.

6 is not only simply replaced the voice coil mass m _c in equation 2 to the magnetic circuit mass m _m, it should be noted that it contains α mass ratio between the magnetic circuit and the voice coil in the denominator . This number 6 is by using magnets of high magnetic flux density lighter, or by increasing the voice coil mass m _c is the magnetic circuit of the constant mass from the relationship shown in Formula 5, increase efficiency η It shows that it is possible. The maximum efficiency of the movable magnet type speaker 10 is when the value of the resulting expression by partially differentiated by the number 6 efficiency η magnetic circuit mass m _m is zero, i.e. when shown in Formula 7 .

That is, in the moving magnet type speaker 10 includes a magnetic circuit mass m _m, the maximum efficiency is obtained when equal and vibration system mass excluding a magnetic circuit including the additional mass. In this movable magnet type speaker 10, the mass of the vibration system other than the magnetic circuit is approximately the mass of the diaphragm 1. Therefore, maximum efficiency can be obtained by making the total mass of the magnetic circuit equal to the mass of the diaphragm 1 including the additional mass. Here, mass _{M o} diaphragm 1 including additional mass, the ratio between the total mass and _{M o} of the magnetic circuit beta, _i.e., the number at the _{m d + 2M s = M o} , m m = βM o 6 8 is obtained by transforming.

Furthermore, in Equation 8, when the mass of diaphragm 1 including the additional mass is equal to the total mass of the magnetic circuit, that is, when the maximum value of η at β = 1 is set as η _max , Equation 9 is obtained.

FIG. 3 shows the relationship between η / η _max and β shown in Equation 9. As can be seen from FIG. 3, η / η _max > 0.888 is obtained in the range of 0.5 ≦ β ≦ 2. That is, if the total mass of the magnetic circuit is in the range of 0.5 to 2.0 times the mass of the diaphragm 1 including the additional mass, an efficiency exceeding 88.8% of the maximum efficiency can be obtained. it can.

In the movable magnet type speaker 10, assuming that the mass of the vibration system other than the magnetic circuit can be regarded almost as the mass of the diaphragm 1, as described above, the diaphragm 1 including the additional mass is about 5 g, one ferromagnetic. Since the thin body plate 4 is about 0.5 g and the single magnet 5 is about 0.75 g, the mass M _{o of the} diaphragm 1 including the additional mass is about 5 g, and the magnetic circuit mass m _m = (0.5 + 0.75) × 4. = About 5 g. That is, the movable magnet type speaker 10 has a maximum efficiency of β = 1, and can output a sufficiently loud sound that can be heard with respect to the supplied audio current.

  The second characteristic configuration of the movable magnet type speaker 10 has been described above. Next, a third characteristic configuration of the movable magnet type speaker 10 will be described. The third characteristic configuration described below is that a plurality of pairs each corresponding to the magnetic circuit and the voice coil 6 are provided. The effects of this configuration will also be described.

  As described above, the total mass of the magnetic circuit has an optimum value, and providing a plurality of magnetic circuits and voice coils while satisfying the condition is nothing other than providing them separately. Here, the fact that the inductance of the voice coil can be reduced by dividing the voice coil into a plurality of parts and electrically connecting the divided voice coils will be described in detail below.

The voice coil 6 in the movable magnet type speaker 10 is a solenoid type coil. The inductance L of the solenoid type coil has a Nagaoka coefficient determined by a ratio of a solenoid diameter and an axial length as K, and a magnetic permeability as a space constant. It is known that it is expressed by Formula 10 where μ, solenoid cross-sectional area is A, number of turns is n, and axial length is 1 _s .

Here, in the solenoid type coil, not only the solenoid diameter and the axial length but also the dimensions of all the components including the winding diameter and the winding length are defined as “total dimensions”. That is, by changing the overall dimension, the coil can be enlarged or reduced while maintaining the similar relationship. If the shape of the coil is constant, the physics teaches that the inductance L is proportional to the overall dimensions of the coil, and it can be confirmed from Equation 10. That is, the solenoid cross-sectional area A is proportional to the square of the total size, the axial length l _s is proportional to the first power of the overall dimensions, permeability mu, Nagaoka coefficient K and the number of turns n is proportional to the zero power of the overall dimensions To do. Therefore, the inductance L as a whole is proportional to the first power of the overall dimension.

Here, considering the case where the winding length is halved without changing the winding diameter of the voice coil, the volume of the voice coil winding is halved. On the other hand, in order to halve the volume of the voice coil winding without changing the overall shape of the voice coil, the total dimension may be set to 0.5 ^1/3 = 0.7937 times. In this way, even if the number of turns is the same as the original, it is derived from the above theory that the inductance L is 0.7939 times. In the above, since it is assumed that the winding length is halved without changing the winding diameter, the number of turns is changed to winding length / solenoid circumference = 0.5 / 0.7937 = 0.63 times. Is done. In this case, the inductance L is 0.7937 × 0.63 ² = 0.315 times because the factor of the overall dimension is further multiplied by the square of the number of turns.

  When two voice coils whose winding lengths are halved with respect to the original voice coil formed in this way are connected in series to a distance where the mutual magnetic coupling can be ignored, the entire inductance L Is the sum of the inductance of each voice coil coil. That is, it decreases to 0.315 × 2 = 0.63 times the initial inductance L before being divided into two.

  When the configuration of the voice coil is changed as described above, since the original electric wire is divided into two parts of the same length and connected in series, the electrical resistance of the entire voice coil is the same as before the division. Each voice coil has half the volume while maintaining the similar relationship without changing its shape, so the magnetic circuit necessary to link each voice coil with the same magnetic flux density as before the division However, the volume can be halved by reducing the size by 0.7937 times while maintaining the similar shape without changing the shape.

  In this way, since two magnetic circuits having a half volume are used, the total mass of the magnetic circuit does not change as a whole. That is, for each of the voice coil and the magnetic circuit, the product of the magnetic flux density B and the voice coil winding length l, and the electric resistance are obtained by dividing the sum of the volume and mass without changing them and positioning them apart from each other. The inductance L can be reduced with the value before the division.

  In the above description, the case of dividing into two parts has been described as an example, but it is obvious that the inductance L can be reduced without limit by further increasing the number of divisions in the same manner. For example, if each of the voice coils divided into two is further divided into two and eventually divided into four, the inductance L is reduced to 0.63 × 0.63 = 0.3969 times the original value. Can do.

  Therefore, for example, if the electrical resistance is 8Ω and the inductance L is 1 mH at the time of one voice coil before division, it is determined that this configuration is not practical because the inductance L is too large and the high-frequency output is not sufficient. May be. On the other hand, in the movable magnet type speaker 10, by dividing the voice coil into four pieces and connecting them, the inductance L can be reduced to 0.3969 mH and a value that does not hinder the output of high sound can be achieved. If there is a problem in the output of treble even with this inductance L, it can be dealt with by further increasing the number of divisions.

In the above description, we considered the case where the winding length was halved without changing the voice coil winding diameter, but in the following, when the winding cross-sectional area was halved without changing the voice coil winding length Think about it. This corresponds to the winding diameter being 0.5 ^1/2 = 0.7071 times, and the volume of the voice coil winding is also halved in this case. Therefore, similarly to the above-described example, after the overall dimensions of the voice coil are increased by 0.7937 times, the number of turns is considered to be changed to winding length / solenoid circumferential length = 1 / 0.7937 = 1.26 times. Then, the inductance L is 0.7937 × 1.26 ² = 1.26 times since the factor of the overall dimension is further multiplied by the square of the number of turns. When two voice coils having a half winding cross-sectional area formed in this way are connected in parallel with a distance where the magnetic coupling between them is negligible, the total inductance L is half of the inductance of each voice coil. It becomes. In other words, the initial inductance L can be reduced to 1.26 / 2 = 0.63 times.

  As described above, when the winding cross-sectional area of the voice coil is changed, the original electric wire is halved in cross-sectional area and connected in parallel, so that the electric resistance does not change from the original value. Each voice coil has half the volume while maintaining the similar relationship without changing its shape, so the magnetic circuit required to link each voice coil with the same magnetic flux density as the original is also shaped. The volume can be halved by reducing it to 0.7937 times while maintaining the similar shape without changing. In this way, since two magnetic circuits having a half volume are used, the total mass of the magnetic circuit does not change as a whole.

  As described above, when the voice coils are divided in parallel, the product of the magnetic flux density B and the voice coil winding length l in each divided voice coil is the same value as before the division. However, when these are connected in parallel, only half the audio current before division flows through each winding. Therefore, the substantial contribution of each voice coil to the product of the magnetic flux density B and the voice coil winding length l is half before the division. By connecting two voice coils in parallel, the magnetic flux density B And the voice coil winding length l are the same as before the division.

  As described above, the inductance L can be similarly reduced in either case where the voice coil is divided in series or in parallel. Of course, the same effect can be obtained when a combination of series and parallel is used.

  In the movable magnet type speaker 10, as described above, the voice coil 6 is divided into four parts while maintaining a similar relationship, thereby reducing the overall inductance of the voice coil 6, and the voice coil 6 at the time of high-frequency output. This prevents a decrease in the audio current supplied to the. In other words, the inductance is reduced by dividing the voice coil 6 so as not to hinder the output in the high sound range. For this reason, it is possible to avoid a decrease in output in the high sound range due to inductance. In the above description, the configuration in which the voice coil 6 is divided into four parts is illustrated. However, depending on design items such as a configuration capable of sufficiently outputting up to which high frequency sound, characteristics of the voice coil 6, and the like. The number of divisions is determined.

  Moreover, in the above-mentioned embodiment, although the cylindrical magnet 5 was illustrated and demonstrated, it is not limited to this structure. Instead of the magnet 5, for example, a rectangular column magnet having a rectangular cross section is used, and instead of the voice coil 6, the internal space is configured using a square coil shape corresponding to the outer shape of the magnet. May be. The dimensional ratio at this time is represented by the ratio between the longitudinal dimension and the equivalent diameter obtained by replacing the cross-sectional area of the magnet with a circle of the same area.

DESCRIPTION OF SYMBOLS 1 Diaphragm 2 Elastic body 3 Frame 4 Ferromagnetic thin plate 5 Magnet 6 Voice coil 7 Voice coil insertion hole 8 Voice coil lead wire 9 Speaker input 10 Movable magnet type speaker 20 Fixed support part 30 Vibration part

Claims (5)

A diaphragm having a magnetic circuit composed of a magnet and a magnetic body according to a magnetic field generated by a voice coil through which an audio current flows is a movable magnet type speaker that vibrates through the magnetic circuit and generates sound waves,
The total mass of the magnetic circuit is 0.5 to 2.0 times the total mass of the additional mass and the mass of the diaphragm. The movable magnet type speaker includes a frame,
The voice coil is divided into a plurality of parts to reduce inductance and prevent a decrease in voice current in a high sound range, and is fixed at different positions in the frame with its axial direction aligned,
The diaphragm is attached to the frame so as to vibrate in the axial direction of the voice coil with a predetermined gap in the axial direction of the voice coil;
The movable magnet type speaker according to claim 1, wherein the plurality of magnetic circuits are fixed to the diaphragm and face the voice coil. The voice coil is a solenoid coil;
The magnet has a columnar shape and is magnetized in the longitudinal direction, and one end face is fixed to the magnetic body and is magnetically connected to the magnetic body, and the other end face is inserted into the hollow portion of the voice coil. The movable magnet type speaker according to claim 1, wherein the movable magnet type speaker is configured to be magnetically coupled to a voice coil. The magnet has a dimensional ratio of 1 or more,
The movable magnet type according to any one of claims 1 to 3, wherein the magnetic body extends outward from the outer shape of the voice coil along a plane perpendicular to the longitudinal direction of the magnet. Speaker. This is a method of manufacturing a movable magnet type speaker in which a diaphragm having a magnetic circuit composed of a magnet and a magnetic body vibrates through the magnetic circuit in response to a magnetic field generated by a voice coil through which an audio current flows, and generates sound waves. And
A first magnetic circuit manufacturing step in which the total mass of the magnetic circuit is 0.5 to 2.0 times the total mass of the additional mass and the mass of the diaphragm;
Voice coil manufacturing process for dividing the voice coil into a plurality of parts to reduce inductance and prevent a decrease in voice current in a high sound range;
The magnet is formed so that a dimensional ratio thereof is 1 or more, and the magnetic body is spread outside the outer shape of the voice coil along a plane perpendicular to the longitudinal direction of the magnet. And a second magnetic circuit manufacturing process. A method of manufacturing a movable magnet type speaker.

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