JP4896255B2 - Magnetic circuit for microspeaker and microspeaker using the same - Google Patents

Description

  The present invention relates to a small and internal magnetic circuit for constituting a micro speaker and a micro speaker using the magnetic circuit.

  Conventionally, with the progress of miniaturization of microspeakers, the internal magnet type magnetic circuit that has a simple structure and can take a large size of the magnet has been dominant in terms of the ease of assembly as a magnetic circuit and the high magnetic flux density. . In this case, as shown in FIG. 10, a deep dish type yoke 1 having an outer peripheral wall forming an outer peripheral pole of the magnetic gap, a flat plate magnet 2 superimposed on the inner bottom surface of the yoke, and an inner periphery of the magnetic gap Since each component member composed of a flat pole piece 3 having an outer peripheral surface forming a pole and superimposed on the upper surface of the magnet is in contact with each other on a wide flat surface at the time of assembly, it is assembled and fixed by an adhesive, that is, an adhesion method Is suitable.

  An example of a general configuration and assembling method of the inner magnet type magnetic circuit of FIG. 10 is shown as a first conventional example in FIGS. 8 and 9 of Patent Document 1, for example. An adhesive is applied to the opposing surfaces of each member during the creation with a three-dimensional jig and during the construction with another jig for attaching the assembly to the yoke.

  On the other hand, FIG. 11 shows a method of assembling and fixing constituent members without using an adhesive in the above-described inner magnet type magnetic circuit. That is, a center hole is provided in each of the magnet 2A and the pole piece 3A to form an annular body, and a cylindrical or bottomed tubular projection 4A that penetrates the center hole of the magnet 2A and the pole piece 3A at the center of the inner bottom surface of the yoke 1A. When assembling, a magnet annular body is sandwiched between the inner bottom surface of the yoke 1A and the annular body of the pole piece, and at least the central hole inner peripheral wall of the pole piece 3A is placed on the outer peripheral surface of the projecting body 4A of the yoke 1A. It is press-fitted and fixed. Here, since the protrusion 4A of the yoke acts as a positioning means, no special jig is required for assembly by the press-fitting method. Therefore, in general, in the internal magnetic type magnetic circuit for a speaker, the configuration using the press-fitting method is simpler than the configuration using the adhesive method requiring an adhesive as a secondary material and a jig. And it is advantageous in terms of economy. Such an assembly method is also shown in FIGS.

Japanese Patent No. 3934182

  However, when the magnetic flux density in the magnetic gap is taken into consideration as an internal magnet type magnetic circuit, a press-fitting for press-fitting the protrusion 4A of the yoke by providing a center hole in the magnet 2A and the pole piece 3A as shown in FIG. In the configuration for the system, the area of the magnet 2A is reduced by the amount of the center hole, and a magnetic circuit is formed in the center hole as a parallel circuit. Therefore, the pole piece outer peripheral surface and the yoke outer peripheral wall inner surface The density of the magnetic flux flowing in the magnetic gap between them is significantly reduced. In particular, in a microspeaker having a small shape, the magnetic flux density in the magnetic gap tends to decrease because the area of the magnet is originally small. Accordingly, the press-fitting method is disadvantageous in terms of magnetic flux density, and an adhesion method in which a central hole is not provided between the magnet and the pole piece as shown in the first conventional example is advantageous.

  However, as speakers become smaller, another problem arises in the bonding method. In particular, in the case of a small-sized microspeaker, the constituent members also become small, and precise management of the adhesive application position and application amount is required. Since these managements must be originally incorporated in an assembly process that is not easy, the assembly process of the microspeaker using the adhesive method is further complicated and costly.

  The present invention eliminates the need for an adhesive and achieves a high magnetic flux density in spite of the configuration for the bonding method in which the center hole is not provided in the magnet, and at the same time simplifies the press-fitting method assembly process without providing the center hole in the magnet. An object of the present invention is to provide a magnetic circuit for a microspeaker that realizes performance and a microspeaker using the magnetic circuit.

In order to achieve the above object, the magnetic circuit for a micro speaker according to the first aspect of the present invention has a magnet 12 and an inner bottom surface bonded to one surface of the magnet 12 and a magnet outer peripheral surface and a space at the outer peripheral end. A yoke 11 having an upright portion, a pole piece 13 having an outer peripheral surface which is joined to the other surface of the magnet 12 and forms an inner peripheral pole of a magnetic gap, and a magnetically coupled magnetically to the upright portion of the yoke 11 A magnetic circuit for a microspeaker comprising a pole plate 14 having an inner peripheral surface forming an outer peripheral pole of a gap, wherein the pole piece 13 is opposite to the magnet 12 from a flat plate portion joined to the magnet 12 and the flat plate portion. And a magnetic body portion 13A having a cylindrical portion with an outer peripheral surface as an inner peripheral pole of the magnetic gap, and one end joined to the outer peripheral edge of the flat plate portion of the magnetic body portion 13A at the other end It consists of a cylindrical non-magnetic body portion 13B inserted into the space between the stone outer peripheral surface and the yoke upright portion, and the yoke 11 is joined to one surface of the magnet 12 and has a deep dish shape having an upright portion. 11A, an inner step for circumscribing the upright portion of the deep dish portion 11A at one end and positioning the pole plate 14 at the other end for forming a magnetic gap with the outer peripheral surface of the cylindrical portion of the pole piece 13 and acoustic radiation It has a cylindrical body portion 11B having an opening and circumscribing the non-magnetic portion 13B of the pole piece 13 in the middle and forming the magnetic coupling between the deep dish portion 11A and the pole plate 14. Features.
According to a second aspect of the present invention, in the magnetic circuit for a micro speaker according to the first aspect, the outer diameter L2 of the magnet is the inner diameter L1 of the magnetic gap at the outer peripheral surface of the cylindrical portion of the pole piece that forms the inner peripheral pole of the magnetic gap. It is characterized by being larger.
According to a third aspect of the present invention, in the magnetic circuit for a microspeaker according to any one of the first and second aspects, the nonmagnetic body portion 13B of the pole piece 13 has an outer peripheral edge of the flat plate portion of the magnetic body portion 13A at the one end. The yoke 11, the magnet 12, and the pole piece 13 are mechanically coupled with the other end inserted between the deep plate-like portion of the yoke 11 and the outer peripheral surface of the magnet. It is characterized by combining.
According to a fourth aspect of the present invention, there is provided a micro speaker according to the present invention, wherein the magnetic circuit for a micro speaker according to any one of the first and second aspects and a cylindrical voice coil VC inserted between inner and outer peripheral poles of a magnetic gap of the magnetic circuit. A vibration system in which an outer peripheral edge is coupled to one end of the diaphragm, and the outer peripheral edge of the diaphragm DP positioned within the acoustic radiation opening of the yoke cylindrical body portion is supported by the inner peripheral edge of the annular edge ED. The outer peripheral end of the ED is sandwiched between the pole plate 14 of the magnetic circuit and the inner step portion of the yoke cylindrical body.

  According to the present invention, the magnet constituting the magnetic circuit used for the microspeaker has a flat plate shape without a center hole, and the flat plate portion of the pole piece is joined to the entire surface of the magnet, and protrudes from the flat plate portion to form a magnetic gap. The diameter L2 of the magnet is made larger than the diameter L1 of the outer peripheral surface of the cylindrical portion forming the inner peripheral pole, and the magnetic flux density in the magnetic gap is increased from the large area magnet through the cylindrical portion. Particularly in a micro speaker having a small structure, these configurations of the present invention are extremely effective as means for improving magnetic flux density and increasing sound pressure. Furthermore, the pole piece includes a cylindrical nonmagnetic body portion joined to the flat plate portion at one end in addition to the magnetic body portion including the flat plate portion and the cylindrical portion, and the magnetic body portion is attached to the nonmagnetic body portion. Because it is press-fitted and prevented from coming off with a projection on one end, a magnet is inserted and the other end of the non-magnetic part is press-fitted between the outer peripheral surface of the magnet and the deep plate-like part of the yoke. Even before the magnet is magnetized, the body part is mechanically stable and stable at the assembly position without the need for assembly jigs and without using an adhesive between the members. Can be held. In a magnetic circuit for a micro speaker, it is not necessary to use a bonding process and an assembly jig that can be more complicated, and it is possible to improve the characteristics of the micro speaker and reduce the manufacturing cost.

The magnetic circuit for microspeakers by this invention, and the center sectional drawing of the microspeaker using the magnetic circuit. FIG. 2 is a development view for illustrating an assembling procedure of each constituent member of the micro speaker of FIG. 1. Sectional drawing which added the arrow which shows the flow of magnetic flux to sectional drawing of the same microspeaker as what is shown in FIG. For comparison with the magnetic flux density achieved by the microspeaker of FIG. 1 or FIG. 3 according to the present invention, a comparison is made by omitting the non-magnetic part of the pole piece of the magnetic circuit according to the present invention and using the press-fitting method for the magnetic circuit. Sectional drawing of the micro speaker as an example. An explanatory view showing a flow of magnetic flux of a magnetic circuit in the present invention is shown. (A) is explanatory drawing which shows distribution of the magnetic flux density of the magnetic circuit of this invention, (b) is explanatory drawing which shows distribution of the magnetic flux density in the space of a magnetic circuit. (A) is explanatory drawing which shows distribution of the magnetic flux density of the magnetic circuit in a comparative example, (b) is explanatory drawing which shows distribution of the magnetic flux density in the space of the magnetic circuit in the comparative example shown in FIG. The explanatory view showing the simulation result of the permeance coefficient in the magnetic gap of the magnetic circuit in the present invention is shown. It is explanatory drawing which shows the simulation result of the permeance coefficient in the magnetic gap of the magnetic circuit in the comparative example shown in FIG. Sectional drawing of an example of the micro speaker using the magnetic circuit by the conventional adhesion system. Sectional drawing of an example of the microspeaker using the magnetic circuit by the conventional press injection system.

  FIG. 1 shows a micro speaker in which a vibration system comprising a cylindrical voice coil, a dome-shaped diaphragm and an annular edge is incorporated in the magnetic circuit simultaneously with an embodiment of a magnetic circuit for a micro speaker according to the present invention. . In FIG. 2, each component of the magnetic circuit including the vibration system is shown in a state of being developed along an assembly procedure in which a press-fitting method is partially adopted.

  According to the present invention, the pole piece 13 joined to one surface of the flat magnet 12 having a flat plate shape is subjected to press working so as to protrude from the flat plate portion 13Aa and the flat plate portion 13Aa to the opposite side of the magnet 12. The magnetic body portion 13A including the cylindrical portion 13Ab and the cylindrical nonmagnetic body portion 13B formed by press processing that circumscribes the flat plate portion 13Aa at one end.

  As the magnet 12, a Nd—Fe—B sintered magnet having high magnetic properties is used, and since it is a flat and circular magnet, it becomes a transverse magnetic field (right angle magnetic field) material. Compared with magnets of (3), a material having a high (BH) max (a material having high magnetic properties) can be used. Further, as the non-magnetic body portion 13B, for example, brass, aluminum or the like is used.

  In the present invention, the nonmagnetic part 13B made of a nonmagnetic material and the magnetic part 13A made of a magnetic material are formed with a uniform thickness in any part after the press working, and the material after the press working Compared with the case of changing the thickness, only simple processing such as bending and drawing is performed, reducing the number of press processing steps (the number of progressive stages), reducing the load on the mold, and processing parts with high accuracy. Furthermore, it is possible to reduce the cost of parts. That is, in the change thickness press processing, the material thickness is selected in accordance with the thickness that is the largest after the press processing. Therefore, it is necessary to select a thicker material, which increases the material cost. Furthermore, in order to change the thickness of the material thinly, it is struck many times with a press, and in order to reduce the thickness, the greater the ratio of reduction to the basic thickness, the greater the man-hours for press work (progressive stage) Number) increases. In contrast, this is not the case with the present invention.

  When assembling the pole piece 13 and further assembling the magnetic circuit assembly including the pole piece 13, first, the cylindrical portion 13Ab of the magnetic portion 13A is protruded from one end of the non-magnetic portion 13B, and the magnetic body The part 13A is press-fitted into the non-magnetic body part 13B, and is prevented from coming off by a projection on the inner surface of one end of the non-magnetic body part 13B, and the pole piece 13 is assembled. Next, the magnet 12 is press-fitted into the non-magnetic body portion 13B, and one surface of the magnet 12 and the flat plate portion 13Aa of the pole piece magnetic body portion 13A are joined, and the other surface of the magnet 12 and the other end surface of the non-magnetic body portion 13B. To be the same. Furthermore, the yoke 11 of the present invention has a cylindrical body portion 11B and a deep dish portion 11A, and the inner bottom surface 11Aa of the deep dish portion 11A forming a part of the yoke 11 is joined to the other surface of the magnet 12. Then, the upright portion 11Ab of the outer peripheral edge is put on the other end of the nonmagnetic body portion 13B, the other end is press-fitted between the upright portion 11Ab and the outer periphery of the magnet, and fixed, thereby producing a magnetic circuit assembly.

  As a feature of the magnetic circuit assembly assembled by this new method, the magnetic body portion 13A of the pole piece 13 and the magnet 12 and the deep dish-like portion 11A of the yoke 11 are the pole piece even before the magnet is magnetized. Since the non-magnetic body portion 13B is mechanically firmly held at the assembly position, no adhesive is required for assembly and fixing, and simple pressing and pressing does not require any positioning jig. Even after the magnet 12 is magnetized, the magnetic part 13A of the pole piece, the magnet 12 and the deep dish-like part 11A of the yoke are held by the magnetic attractive force generated between these members at the mechanical holding position by the non-magnetic part 13B. The force is further increased, and an impact when dropped or the like does not lead to breakage of the magnetic circuit, and a highly reliable magnetic circuit can be obtained.

  The cylindrical body portion 11B of the yoke 11 has a height that can accommodate a magnetic circuit having a height including the vibration system of the microspeaker. The cylindrical body portion 11B is an acoustic whose one end is smaller in diameter than the cylindrical body portion. It has a radiation opening 11Bb, an inner step portion 11Ba is provided on the inner surface in the vicinity thereof, the other end is an open end 11Bc, and a slit-like terminal lead-out port 11Bd is provided from a part thereof to an intermediate portion. In the yoke cylindrical body portion 11B, for example, the inner peripheral edge of the annular edge ED is bonded to the outer periphery of the diaphragm DP having the outer peripheral edge bonded to one end of the cylindrical voice coil VC as shown in FIG. Is inserted from the open end 11Bc, the outer peripheral edge of the edge ED is placed on the inner step portion 11Ba, and the annular pole plate 14 whose inner peripheral surface forms the outer peripheral pole of the magnetic gap is attached to the inner surface of the yoke cylindrical body portion 11B. Is inserted between the voice coil VC of the vibration system and the outer peripheral edge of the edge ED is pressed and held on the inner step portion 11Ba, and a gap is provided on the outer peripheral surface of the voice coil VC.

  Further, the lead wire TW of the voice coil VC is led out along the terminal lead-out port 11Bd of the yoke cylindrical body portion 11B. Further, the magnetic circuit assembly of the magnet 12 and the magnetic body portion of the pole piece 13 and the non-magnetic body portion and the deep plate-like portion of the yoke is press-fitted into the yoke cylindrical body portion 11B, and the pole piece magnetic body portion The cylindrical portion 13Ab is inserted into the cylindrical space in the voice coil VC of the vibration system, and the bottom surface of the pole plate 14 is pushed toward the inner step portion 11Ba with one end surface of the non-magnetic member portion 13B, and the outer periphery of one end is yoked. The upper part 11Ab of the yoke deep dish part is joined to the inner surface of the open end 11Bc of the yoke cylindrical part.

  As a result, the pole plate 14 is magnetically coupled to the yoke deep dish portion 11A via the yoke cylindrical body portion 11B, and the inner peripheral surface of the pole plate 14 facing the voice coil VC and the pole piece cylindrical portion. Magnetic flux flows between the outer peripheral pole and the inner peripheral pole of the magnetic gap formed by the outer peripheral surface of 13Ab. The lead wire TW of the voice coil VC is led to the terminal lead-out port 11Bd of the yoke cylindrical body part through the lead-out groove 13Ba provided on one end face of the pole piece non-magnetic part 13B. It is latched by the terminal board 15 joined to the outer bottom face.

  In the present invention, as shown in FIG. 1, the outer diameter L2 of the magnet 12 is configured to be larger than the inner diameter L1 of the magnetic gap on the outer peripheral surface of the cylindrical portion of the pole piece 13 forming the inner peripheral pole of the magnetic gap. The shape of 12 is large and the magnetic force is large.

  FIG. 3 is a cross-sectional view of the microspeaker according to the present invention shown in FIG. 11A is a deep dish portion, 11B is a cylindrical body portion constituting a yoke, 12 is a magnet, 13B is a non-magnetic body portion, 14 is a pole plate, VC is a voice coil, DP is a diaphragm, and G is a magnetic gap. .

  FIG. 4 shows a micro speaker produced in order to contrast the magnetic flux density of the product of the present invention. In this micro speaker, the magnetic part 13A having the cylindrical part 13Ab is the same as that of the present invention, but the non-magnetic part 13B of the present invention is omitted. Further, a central hole is provided in the deep dish portion 11A and the magnet 12, the inner surface of the hollow portion of the cylindrical portion 13Ab is flush, and a cylindrical projection 16 made of a nonmagnetic material is press-fitted into the central holes of these members. The magnetic circuit was assembled and configured.

  FIG. 5 shows a state in which the magnetic flux of the magnet 12 flows from the cylindrical portion 13Ab → the pole plate 14 → the magnetic gap G → the cylindrical body portion 11B of the yoke 11 → the deep dish portion 11A → the magnet 12.

  6A and 6B show the magnetic flux distribution of the magnetic circuit portion of the micro speaker according to the present invention shown in FIG. 6A shows the magnetic flux distribution of the magnet 12, the cylindrical portion 13Ab, the pole plate 14, and the yoke 11, and FIG. 6B shows the magnetic flux density including the magnetic gap G other than the magnetic circuit.

  The scale on the right side of each figure shows the state of magnetic flux density by color and numerical value. The color changes from blue to finally red from the bottom to the top of the scale. That is, A blue → B sky blue → blue close to B ′ green → C green → D yellow → E orange → F red. The closer to red F, the denser the magnetic flux. Moreover, although the numerical value is attached | subjected beside each color, it shows that a magnetic flux is so dense that a numerical value is large.

  As shown in FIG. 6 (b), in the present invention, the portion of the magnetic gap G includes a substantially red to orange FE indicated by a numerical value 0.497 to 0.411 [T] (Tesla), and the surrounding yellow color. An area D is generated.

  In the present invention, since the magnetic flux density in the magnetic gap G can be improved as described above, the driving force of the voice coil VC coupled to the diaphragm DP can be improved. For this reason, the sound pressure can be increased.

  On the other hand, FIGS. 7A and 7B show the magnetic flux density by the micro speaker according to the comparative example shown in FIG.

  Even in the comparative example, there is a yellow to green region DC in the cylindrical portion 13Ab. As is apparent from the numerical value of the scale on the right side, the value is 1.619 to 1.469 [T]. The magnetic flux density is low.

  In the magnetic gap G, there are red, orange, and yellow FD regions, but the value on the right scale is 0.44 to 0.335 [T]. As is apparent from these, the magnetic flux density is lower than that of the product of the present invention.

  8 and FIG. 9 compare the permeance coefficients in the magnetic gap between the product of the present invention shown in FIG. 3 and the comparative example shown in FIG.

  As shown in FIG. 8, in the product of the present invention, the maximum value of the magnetic flux density was 0.421 [T], whereas in the comparative example, the maximum value of the magnetic flux density was 0.385 [T]. T] shows that the product of the present invention is superior.

  The reason why the magnetic flux density is lower in the comparative example than in the embodiment of the present invention is that the magnet area is reduced by the center hole and the magnetic flux flowing through the magnetic gap G is small.

  In the above embodiment, the diaphragm DP has a substantially dome shape, but other shapes can also be applied.

11 Yoke 11A Deep dish portion 11Aa Inner bottom surface 11Ab Upright portion 11B Cylindrical body portion 11Ba Inner step portion 11Bb Acoustic radiation opening 11Bc Open end 11Bd Terminal outlet 12 Magnet 13 Pole piece 13A Magnetic body portion 13Aa Flat plate portion 13Ab Tubular portion 13B Nonmagnetic part 14 Pole plate 15 Terminal plate VC Voice coil TW Coil lead wire DP Diaphragm ED Edge L1 Magnetic gap inner diameter L2 Magnet outer diameter G Magnetic gap

Claims (4)

  A magnet (12), a yoke (11) which is joined to one surface of the magnet (12) at the inner bottom surface and has a magnet outer peripheral surface and a space at the outer peripheral end and has a raised portion, and the other of the magnet (12) And an inner peripheral surface that forms an outer peripheral pole of the magnetic gap by being magnetically coupled to a rising portion of the yoke (11). A magnetic circuit for a microspeaker comprising a pole plate (14) provided with a flat plate portion joined to the magnet (12) and a plate plate opposite to the magnet (12) from the flat plate portion. A magnetic part (13A) having a cylindrical part that protrudes to the side and has an outer peripheral surface as an inner peripheral pole of a magnetic gap, and is joined to the outer peripheral edge of the flat part of the magnetic part (13A) at one end and the outer circumference of the magnet at the other end Surface and yoke upright The yoke (11) is joined to one surface of the magnet (12) and has a raised plate-like portion (upper portion) ( 11A) and one end circumscribing the upright portion of the deep dish portion (11A) and the other end positioning the pole plate (14) for forming a magnetic gap between the outer peripheral surface of the cylindrical portion of the pole piece (13). The magnetic field between the deep plate portion (11A) and the pole plate (14) that has a stepped portion and an acoustic radiation opening and circumscribes the nonmagnetic body portion (13B) of the pole piece (13) in the middle. A magnetic circuit for a microspeaker, characterized by comprising a cylindrical body part (11B) that forms a mechanical connection.   2. The magnetic circuit for a micro speaker according to claim 1, wherein the outer diameter L2 of the magnet is larger than the inner diameter L1 of the magnetic gap on the outer peripheral surface of the cylindrical part of the pole piece forming the inner peripheral pole of the magnetic gap.   The non-magnetic part (13B) of the pole piece (13) is provided with an inward protrusion for retaining the outer peripheral edge of the flat part of the magnetic part (13A) at the one end, and the upright part of the deep plate-like part of the yoke (11) The yoke (11), the magnet (12) and the pole piece (13) are mechanically coupled together with the other end inserted between the magnet and the outer peripheral surface of the magnet. A magnetic circuit for a microspeaker according to any one of the above. A magnetic circuit for a microspeaker according to claim 1 and a cylindrical voice coil VC inserted between inner and outer peripheral poles of a magnetic gap of the magnetic circuit, and an outer peripheral edge coupled to a yoke cylindrical shape. A vibration system in which the outer peripheral edge of the diaphragm DP located in the acoustic radiation opening of the body part is supported by the inner peripheral edge of the annular edge ED, and the outer peripheral end of the annular edge ED of the vibration system is a pole plate of the magnetic circuit A microspeaker characterized in that the microspeaker is sandwiched between an inner step portion of a yoke cylindrical body portion.

Images