The present disclosure relates to a speaker magnetic circuit and a speaker driver.
An electroacoustic transducer that includes a diaphragm connected to a voice coil and cylinder shaped magnet having a larger diameter than the voice coil is disclosed in International Publication (WO) No. 2020/218042. A microspeaker having a magnet disposed inside a yoke formed in a circular cylinder shape is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2012-39353.
A ring shaped magnet is employed in an external magnet structure in which a magnet is disposed outside, as in the electroacoustic transducer as described in WO No. 2020/218042, and so this makes it difficult to achieve a compact magnetic circuit. Although an internal magnet structure in which a magnet is disposed inside a yoke, as in the microspeaker described in JP-A No. 2012-39353, is easily made compact, securing magnetic flux density and adjusting frequency characteristics therein is difficult.
An object of the present disclosure is to provide a speaker magnetic circuit and a speaker driver that enable magnetic flux density to be secured and frequency characteristics to be adjusted in an internal magnet structure.
A speaker magnetic circuit according to a first aspect includes a yoke cover that is formed from a tubular magnetic body with a diaphragm attachable to an end portion on an axial direction one-side; a magnet arranged at an inside of the yoke cover; a volume adjusting member that is formed from a tubular non-magnetic body, that is provided between the yoke cover and the magnet, and that is formed with a first groove extending in an axial direction; and a yoke base that is formed from a magnetic body, that is provided at an axial direction other-side of the magnet, and that is formed with a second groove at a position corresponding to the first groove, wherein: the first groove and the second groove configure a duct portion that communicates a space inside the yoke cover at the axial direction one-side with a space at the axial direction other-side therein.
In the above aspect, the yoke cover is formed from the tubular magnetic body and a diaphragm is attachable to the axial direction one-end portion of the yoke cover. Moreover, the magnet is arranged at the inside of the yoke cover and configures a magnetic circuit between the magnet and the yoke cover. The yoke base formed from the magnetic body is also provided at the axial direction other-side of the magnet. This thereby enables the magnetic flux density of the magnetic circuit to be raised.
The volume adjusting member is provided between the yoke cover and the magnet. The volume adjusting member is formed from the tubular non-magnetic body, and the first groove is formed to the volume adjusting member so as to extend in the axial direction. The second groove is formed to the yoke base at a position corresponding to the first groove, and the duct portion is configured by the first groove and the second groove. The space at the axial direction one-side of the magnet is communicated through the duct portion with the space at the axial direction other-side thereof, and so air at a periphery of the diaphragm is accordingly able to move through the duct portion to the outside of the yoke base when the diaphragm vibrates, thereby enabling damping of frequency characteristics to be adjusted. Note that reference here to the “first groove” is not limited to an indentation shaped portion formed so as to indent a portion of the volume adjusting member, and is broadly defined to include a slit shaped portion.
A speaker magnetic circuit according to a second aspect is the first aspect, wherein the volume adjusting member extends in the axial direction, from an axial direction one-end portion of the yoke cover to the yoke base, so as to fill a gap between the magnet and the yoke cover.
In the above aspect, the volume adjusting member extends in the axial direction as far as the yoke base, and so this thereby enables the volume inside the yoke cover to be adjusted merely by changing the shape and/or size of the first groove, enabling easy adjustment of the lowest resonance frequency (F0). For example, a volume at the inside of the yoke cover can be reduced by adjusting the size of the first groove of the volume adjusting member. As a result this enables the lowest resonance frequency (F0) to be suppressed from becoming lower.
A speaker magnetic circuit according to a third aspect is the first aspect or the second aspect, wherein a projection portion is provided at the volume adjusting member so as to project from an axial direction other-end portion thereof toward a yoke base side; and an engagement indentation for engaging with the projection portion is formed to the yoke base.
In the above aspect, the projection portion formed to the volume adjusting member engages with the engagement indentation formed to the yoke base, and this accordingly enables relative movement between the volume adjusting member and the yoke base to be suppressed even without fixing these two components together with a means such as bonding or the like. This thereby enables a state of alignment between the positions of the first groove formed to the volume adjusting member and the second groove formed to the yoke base to be maintained.
A speaker magnetic circuit according to a fourth aspect is any one of the first aspect to the third aspect, wherein a yoke top formed from a magnetic body with a smaller diameter than a diameter of the magnet is provided at an axial direction one-side of the magnet; and the volume adjusting member includes a ring shaped portion that is formed in a ring shape and is able to support the yoke top from a radial direction outer side, and a side wall portion that extends from a peripheral end portion of the ring shaped portion toward an axial direction other-side and that is able to support the magnet from the radial direction outer side.
In the above aspect, the ring shaped portion of the volume adjusting member supports the yoke top, and the side wall portion of the volume adjusting member supports the magnet, thereby enabling the central axes of the yoke top and the magnet to be suppressed from displacing. Namely, positioning between the yoke top and the magnet can be performed by the volume adjusting member for adjusting the volume without providing a separate member for positioning.
A speaker magnetic circuit according to a fifth aspect is the fourth aspect, wherein the yoke cover includes a top face portion abutted by the ring shaped portion of the volume adjusting member, and a side wall portion that extends in the axial direction from a peripheral end portion of the top face portion and that covers the volume adjusting member from the radial direction outside; and the top face portion is formed with an opening portion through which the yoke top is inserted, and with an upstand portion that projects from an opening edge of the opening portion further toward the axial direction one-side than the yoke top.
In this aspect, the volume adjusting member can be positioned by abutting the ring shaped portion of the volume adjusting member against the top face portion of the yoke cover. The yoke top is inserted through the opening portion of the top face portion, and the upstand portion formed to the opening edge of the opening portion projects further toward the axial direction one-side than the yoke top. Magnetic field lines accordingly pass obliquely from the yoke top toward the upstand portion, enabling the magnetic flux density of the magnetic circuit to be raised at the position of the coil arranged between the yoke top and the yoke cover. The yoke top and the yoke cover can be positioned in the axial direction by the volume adjusting member, thereby enabling the magnetic field lines to flow in a desired direction.
A speaker driver according to a sixth aspect includes the speaker magnetic circuit of any one of the first aspect to the fifth aspect, a diaphragm provided at an axial direction one-end portion of the yoke cover; and a coil that is attached to the diaphragm and that causes the diaphragm to vibrate by current being passed through the coil.
In the above aspect, the air at the inside of the yoke base moves through the duct portion when the diaphragm is vibrated. This thereby enables adjustment of frequency characteristics to be performed easily.
The speaker magnetic circuit and the speaker driver of the present disclosure enable magnetic flux density to be secured and frequency characteristics to be adjusted in an internal magnet structure.
Explanation follows regarding a speaker driver 10 according to an exemplary embodiment, with reference to the drawings. Note that Z in
Speaker Driver 10 Overall Configuration
As illustrated in
As illustrated in
The volume adjusting member 14 is a tubular shaped member arranged inside the yoke cover 12, and is formed from a non-magnetic body. The volume adjusting member 14 of the present exemplary embodiment is, as an example, formed by a metal member having aluminum as a main component. The volume adjusting member 14 is configured including a ring shaped portion 44 formed in a substantially ring shape, and a side wall portion 46 extending from a peripheral end portion of the ring shaped portion 44 toward the axial direction other-side (opposite side to the Z direction). Details regarding the volume adjusting member 14 will be described later.
The yoke top 16 and the magnet 18 are arranged at the inside of the volume adjusting member 14. As illustrated in
The yoke top 16 is arranged at the axial direction one-side of the magnet 18. The yoke top 16 is formed from a magnetic body in a shape that combines a truncated cone with a circular pillar, with the truncated cone shaped portion abutting a face of the magnet 18 on the axial direction one-side. The axial direction length of the yoke top 16 is shorter than that of the magnet 18, and the external diameter of the yoke top 16 is a smaller diameter than that of the magnet 18. In other words, the magnet 18 is formed longer in the axial direction than the yoke top 16, and is formed with a larger diameter than that of the yoke top 16. A beveled portion 16A is moreover formed to the yoke top 16 by beveling an axial direction one-end portion thereof.
As illustrated in
The screen 22 is arranged at an axial direction other-side of the yoke base 20. As illustrated in
As illustrated in
The terminal 26 is attached to a face on the axial direction other-side of the metal plate 24. The terminal 26 is formed in a substantially circular plate shape, with a communication hole 26A that is formed in a central portion of the terminal 26 communicating with the air hole 24B of the metal plate 24. An electrode 27 is provided on an axial direction other-side face of the terminal 26, and a non-illustrated lead wire extending from the coil 28 is connected to the electrode 27.
The coil 28 and the diaphragm unit 30 are arranged at the axial direction one-side of the yoke cover 12. As illustrated in
As illustrated in
A central portion of the diaphragm 33 is formed in a substantially flat plate shape, and an edge portion 33A is formed to an outer peripheral portion of the diaphragm 33 so as to bulge out toward the axial direction one-side. The coil 28 is moved in the axial direction by passing current through the coil 28, in a configuration such that the diaphragm 33 vibrates along with this movement.
The lid member 32 is arranged at the axial direction one-side of the diaphragm unit 30. The lid member 32 is formed from a non-magnetic body such as stainless steel, aluminum, or the like in a substantially circular cylinder shape. An opening portion 32A is formed in a central portion of the lid member 32, with sound generated by vibration of the diaphragm 33 output to outside the driver 10 through the opening portion 32A.
The lid member 32 is formed with a larger diameter at the axial direction other-side than at the axial direction one-side, and the diaphragm unit 30 is sandwiched against the yoke cover 12 by a step portion 32B between a small diameter portion and a larger diameter portion thereof. Furthermore, an axial direction other-end portion of the lid member 32 is attached to the yoke cover 12.
Magnetic Circuit 11 Configuration
Next, detailed description follows regarding a configuration of the speaker magnetic circuit 11, which is a relevant portion of the present disclosure. The speaker magnetic circuit 11 is configured including the yoke cover 12, the volume adjusting member 14, the yoke top 16, the magnet 18, and the yoke base 20.
As illustrated in
The side wall portion 42 extends in the axial direction as far as the position of the terminal 26, with an end face on the axial direction other-side of the side wall portion 42 substantially flush with an end face on the axial direction other-side of the terminal 26. An opening portion 42A is formed in an axial direction other-end portion of the side wall portion 42, with components such as the volume adjusting member 14, the magnet 18, the yoke base 20, the metal plate 24, and the terminal 26 arranged at the inside of the yoke cover 12 through the opening portion 42A.
As illustrated in
An upstand portion 40B is formed to an opening edge of the opening portion 40A of the top face portion 40 so as to project out toward the axial direction one-side. The upstand portion 40B is formed in a substantially circular arc shape as viewed along the axial direction, and is formed up to just before where the cut out portion 42B is formed to the side wall portion 42. Moreover, as illustrated in
As stated above, the volume adjusting member 14 is configured including the ring shaped portion 44 and the side wall portion 46, with the axial direction one-side of the ring shaped portion 44 abutted against the top face portion 40 of the yoke cover 12. An opening portion 44A having a slightly larger diameter than that of the opening portion 40A of the yoke cover 12 is formed to a central portion of the portion 44, with the opening portion 44A communicating with the opening portion 40A of the yoke cover 12. Furthermore, a projection portion 44B projects out from an inner peripheral face of the ring shaped portion 44 toward the radial direction inside, with an inner diameter of the axial direction other-end portion of the opening portion 44A being a smaller diameter than the inner diameter at the axial direction one-end portion due to the presence of this projection portion 44B. The projection portion 44B is configured so as to be able to support the yoke top 16 from the radial direction outside.
The side wall portion 46 extends from a peripheral end portion of the ring shaped portion 44 toward the axial direction other-side, and is configured so as to be able to support the magnet 18 from the radial direction outside. As an example in the present exemplary embodiment, an axial direction other-end portion of the side wall portion 46 extends as far as the same position as the axial direction other-end portion of the magnet 18. The volume adjusting member 14 accordingly extends in the axial direction from the axial direction one-end portion of the yoke cover 12 as far as the yoke base 20 so as to fill a gap between the magnet 18 and the yoke cover 12.
Moreover, as illustrated in
A projection portion 46B is provided to the side wall portion 46 so as to project out from the axial direction other-end portion of the volume adjusting member 14 toward the yoke base 20 side. The projection portion 46B is formed at a position on the opposite side of the axial center to the first groove portion 46A. Namely, the projection portion 46B is formed at a position rotated by 180° about the axial center with respect to the first groove portion 46A.
As illustrated in
Inside of the yoke cover 12, a space at the axial direction one-side and a space at the axial direction other-side thereof are placed in communication with each other through the duct portion D. Namely, in cases in which a space (axial direction one-side space) at a periphery of the coil 28 is enlarged when the diaphragm 33 vibrates, air from outside the driver 10 is introduced to inside the driver 10 through the communication hole 26A, the air hole 24B, and the duct portion D. When this occurs the pressure is regulated by the mesh member 22A of the screen 22. In the opposite scenario, when the space at the periphery of the coil 28 is constricted when the diaphragm 33 vibrates, air inside the driver 10 is pushed outside the driver 10 through the duct portion D, the air hole 24B, and the communication hole 26A, and pressure is regulated.
As illustrated in
Magnetic Circuit 11 Assembly Method
Next, description follows regarding a method of assembling the speaker magnetic circuit 11. Note that in the following description only part of a procedure to assemble the speaker magnetic circuit 11 is illustrated and described. Moreover, in the following description the top side of the page is taken as being a upward direction, and the bottom side of the page is taken as being a downward direction.
As illustrated in
The yoke top 16 is fitted into the circular cylinder portion 100B of the jig 100 with the smaller diameter portion facing downward. When this is performed, for example, a taper profile is formed to an inner face at an upper end portion of the circular cylinder portion 100B and a truncated cone shaped portion of the yoke top 16 is supported thereby.
As illustrated in
The magnet 18 is then inserted inside the volume adjusting member 14, resulting in the state illustrated in
After the yoke base 20 has been inserted inside the yoke cover 12, as illustrated in
After the metal plate 24 has been fitted and the speaker magnetic circuit 11 assembled, the terminal 26 is bonded to the axial direction other-side of the speaker magnetic circuit 11, and the diaphragm unit 30 with the coil 28 attached thereto and the lid member 32 are attached to the axial direction one-side of the speaker magnetic circuit 11.
Operation
Next, description follows regarding the operation of the present exemplary embodiment.
The yoke base 20 is provided at the axial direction other-side of the magnet 18 in the speaker driver 10 according to the present exemplary embodiment, thereby enabling the magnetic flux density of the magnetic circuit to be raised. Namely, a magnetic flux density can be secured even with a compact driver 10.
Moreover as illustrated in
The first groove portion 46A is formed to the side wall portion 46 of the volume adjusting member 14 so as to extend in the axial direction. The second groove 20A is formed to the yoke base 20 at a position corresponding to the first groove portion 46A, with the first groove portion 46A and the second groove 20A configuring the duct portion D. The air at the periphery of the diaphragm 33 is accordingly able to move to the outside of the yoke base 20 through the duct portion D when the diaphragm 33 vibrates, thereby enabling frequency characteristics to be adjusted. For example, acoustic control can be performed using the duct portion D to raise or lower the sound pressure of a specific frequency. Moreover, foreign matter can be suppressed from intruding inside the driver 10 by the mesh member 22A of the screen 22.
In particular, in the present exemplary embodiment the projection portion 46B formed to the volume adjusting member 14 is engaged with the engagement indentation 20B formed to the yoke base 20. This thereby enables relative movement between the volume adjusting member 14 and the yoke base 20 to be suppressed from occurring in the circumferential direction even without mechanically joining the two components together, enabling good performance of the duct portion D to be maintained. Note that due to the second groove 20A and the engagement indentation 20B being formed in the yoke base 20 of the present exemplary embodiment with different shapes to each other, the yoke base 20 is not able to be assembled with the wrong orientation during assembly of the speaker magnetic circuit 11.
Furthermore, due to the volume adjusting member 14 extending in the axial direction as far as the yoke base 20 in the present exemplary embodiment, the volume inside the yoke cover 12 can be adjusted merely by changing the shape and/or size of the first groove, enabling the lowest resonance frequency (F0) to be easily adjusted. For example, the volume inside the yoke cover 12 can be reduced by adjusting the first groove of the volume adjusting member 14. Lowering of the lowest resonance frequency (F0) can be suppressed as a result thereof. Moreover, the volume inside the yoke cover 12 can be finely regulated merely by changing the shape of the volume adjusting member 14, enabling a desired lowest resonance frequency (F0) to be obtained.
Furthermore, in the present exemplary embodiment the ring shaped portion 44 of the volume adjusting member 14 supports the yoke top 16, and the side wall portion 46 of the volume adjusting member 14 supports the magnet 18. This thereby enables a large misalignment between the axial centers of the yoke top 16 and the magnet 18 to be suppressed from occurring. Namely, positioning of the yoke top 16 and the magnet 18 can be performed without providing a separate member for positioning.
Moreover, as illustrated in
Note that although the first groove portion 46A is formed in the volume adjusting member 14 only at a single location in the present exemplary embodiment, there is no limitation thereto. For example, structures of modified examples illustrated in
As illustrated in
Moreover, although not illustrated, there are also second grooves 20A formed to the yoke base 20 at respective positions corresponding to the two first groove portions 46A. This means that there are two duct portions D formed in the present modified example.
As illustrated in
Moreover, although not illustrated, there are also second grooves 20A formed to the yoke base 20 at respective positions corresponding to the three first groove portions 46A. There are accordingly three duct portions D formed in the present modified example.
By increasing the number of the first groove portions 46A in the first modified example and the second modified example as described above from those of the exemplary embodiment, the first groove portions 46A are formed at uniform intervals in the circumferential direction, with this resulting in uniform flow of air, and enabling vibration of the diaphragm 33 to be stabilized.
Supplementary Explanation
Although the driver 10 and the speaker magnetic circuit 11 according to an exemplary embodiment have been described above, obviously various embodiments may be implemented within a range not departing from the spirit of the present disclosure. For example, although the beveled portion 16A is formed to the yoke top 16 in the above exemplary embodiment as illustrated in
Moreover, although in the exemplary embodiment described above the upstand portion 40B of the yoke cover 12 projects out further toward the axial direction one-side than the yoke top 16, in a configuration in which magnetic field lines are oriented obliquely from the vicinity of the beveled portion 16A of the yoke top 16 toward the upstand portion 40B, there is no limitation thereto. For example, an axial direction one-end portion of the upstand portion 40B and an axial direction one-end portion of the yoke top 16 may be at the same position. Such cases are a configured with the magnetic field lines oriented in a radial direction from the yoke top 16 toward the upstand portion 40B.
Furthermore, although in the above exemplary embodiment the length of the side wall portion 46 of the volume adjusting member 14 is set to a length so as to cover the magnet 18 entirely, there is no limitation thereto. For example, the side wall portion 46 may be formed shorter in the axial direction than the configuration illustrated in
Furthermore, although in the exemplary embodiment described above the first groove portion 46A is formed as a substantially slit shape in the side wall portion 46 of the volume adjusting member 14, there is no limitation thereto, and the first groove portion 46A may be formed in another shape. For example, the first groove portion 46A may be formed so as to indent the side wall portion 46 toward the radial direction outside. The duct portion D can be configured from the first groove portion 46A and the second groove 20A in such cases too.
The entire content of the disclosure of Japanese Patent Application No. 2021-030902 is incorporated by reference in the present specification.
All publications, patent applications and technical standards mentioned in the present specification are incorporated by reference in the present specification to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by respect.
Number | Date | Country | Kind |
---|---|---|---|
2021-030902 | Feb 2021 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP22/04953 | 2/8/2022 | WO |