Audio devices

Abstract

The present invention provides an audio device that enables the construction of a thinner box containing a speaker unit with a large magnetic circuit section. [Solution] In the sound device 1, a speaker unit 20 is housed inside a box 10. The rear plate 32b of the magnetic circuit section 30 constituting the speaker unit 20 is made thin, and an auxiliary plate 35 embedded in the rear wall 11 of the box 10 is magnetically bonded to the rear plate 32b. Because a part of the yoke constituting the magnetic circuit section 30 is embedded in the rear wall 11, the internal space 15 of the box 10 can be used efficiently, and the box 10 can be made thin. The yoke consists of a center yoke 32, a front plate 33, and an auxiliary plate 35.

Description

Technical Field

[0001] The present invention relates to an acoustic device such as an in-vehicle device in which a speaker unit is built into a thin box.

Background Art

[0002] In paragraph

[0002] of Patent Document 1, it is described that "in an in-vehicle speaker, when it is desired to produce a heavy bass, a method such as installing a subwoofer housed in a large cabinet in the trunk of the car is adopted. However, when the car is small or when it is not desired to sacrifice the trunk space, etc., when a large cabinet cannot be attached, for example, a vibrator is attached to the floor surface under the seat of the car, etc., and the floor surface is vibrated. Thus, the interior of the car is used as a cabinet for reproduction."

[0003] In FIG. 4 of Patent Document 1, an example of a vibrator is shown. This vibrator has a yoke provided on the inner bottom surface of a case fixed to the floor surface of a vehicle or the like. The yoke has a column portion in the center and a flange portion at the bottom, and the flange portion is fixed to the inner bottom surface of the case. A ring-shaped magnet is fixed on the flange portion of the yoke, and a top plate having a large hole is fixed on the magnet. A magnetic gap is formed between the column portion of the yoke and the hole of the top plate. A frame is fixed on the top plate, a voice coil bobbin is supported by the frame by two butterfly dampers, and a voice coil wound around the lower end of the voice coil bobbin is located in the magnetic gap. A weight to which the upper end portion of the voice coil bobbin is connected is supported by the butterfly damper. This vibrator has a low-frequency component of an audio signal applied to the voice coil, causing the weight to vibrate up and down, and the vibration of the weight is transmitted to the floor surface of the vehicle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The vibrator described in Patent Document 1 is designed to be placed in a space with limited height inside a vehicle, such as the floor under the seats, and therefore requires a thin case. To obtain an effective excitation force in the low-frequency range, a large magnet is required to vibrate the weight up and down with a large amplitude. This requires securing space within the case to accommodate the large magnet and the weight that operates with a large amplitude, which limits the degree to which the case can be made thin.

[0006] As an in-car audio system, a so-called powered woofer is used, which houses a speaker unit that acts as a woofer and electronic devices such as an amplifier within a box. This powered woofer is also installed in a space with limited height, such as the floor under the seat. In powered woofers as well, since it is necessary to vibrate the diaphragm of the speaker unit with a large amplitude in the low-frequency range, there is a challenge in reducing the vertical thickness of the box, similar to the vibrator described in Patent Document 1.

[0007] The present invention aims to solve the above-mentioned conventional problems and to provide an acoustic device that can secure space inside the box for arranging a magnetic circuit section including a relatively large drive magnet, while also reducing the thickness of the box. [Means for solving the problem]

[0008] The present invention relates to an acoustic device having a box and a speaker unit housed in the internal space of the box, The box has a front wall portion having an opening, and a rear wall portion facing the front wall portion. The speaker unit comprises a frame, a diaphragm supported by the frame so as to be freely vibrable, a voice coil that vibrates together with the diaphragm, and a magnetic circuit section that applies a magnetic field to the voice coil, wherein the magnetic circuit section comprises a magnet and a yoke made of a magnetic material, and a magnetic gap is formed in a part of the yoke in which the voice coil is located. The sound pressure emitted from the diaphragm is capable of being released into the external space through the opening, and a portion of the yoke is located inside the rear wall.

[0009] The acoustic device of the present invention has a yoke that has a front plate that contacts the front of the magnet, a rear plate that contacts the rear of the magnet, and an auxiliary plate located inside the rear wall, wherein the rear plate and the auxiliary plate are magnetically connected.

[0010] In the acoustic device of the present invention, it is preferable that the thickness dimension of the rear plate in the front-to-back direction is smaller than the thickness dimension of the front plate in the front-to-back direction, and that the sum of the thickness dimensions of the rear plate and the auxiliary plate in the front-to-back direction is equal to or greater than the thickness dimension of the front plate.

[0011] In the acoustic device of the present invention, it is preferable that a gap is formed in the yoke that is continuous with the magnetic gap to the rear, and that the contact portion between the outer end of the auxiliary plate and the rear plate is located outside the outer inner surface of the gap.

[0012] The acoustic device of the present invention can be configured such that the auxiliary plate is formed separately from the rear plate.

[0013] In the acoustic device of the present invention, for example, the auxiliary plate is embedded inside the rear wall by insert molding. Alternatively, a hole is formed in the rear wall, and the auxiliary plate is inserted inside the hole.

[0014] The acoustic device of the present invention has the rear plate and the auxiliary plate formed integrally, The auxiliary plate can be configured to be located inside the hole formed in the rear wall.

[0015] The sound device of the present invention, for example, has an electronic device built into the box together with the speaker unit. [Effects of the Invention]

[0016] In the present invention, a portion of the yoke constituting the magnetic circuit in the speaker unit is embedded inside the rear wall of the box. Therefore, the box can be made as thin as possible without having to thin the magnetic circuit. [Brief explanation of the drawing]

[0017] [Figure 1] A perspective view of the acoustic device according to the first embodiment of the present invention, viewed from the front. [Figure 2] Figure 1 shows a longitudinal cross-sectional view of the acoustic device cut along line II-II. [Figure 3] (A) is a partially enlarged cross-sectional view showing a portion of the cross-section of the acoustic device shown in Figure 2, and (B) is a partially enlarged cross-sectional view showing the process of assembling the speaker unit to the rear wall of the box. [Figure 4] This shows a modified version of the sound device of the first embodiment, where (A) is a partially enlarged cross-sectional view showing an enlarged portion of the cross-section of the sound device, and (B) is a partially enlarged cross-sectional view showing the process of assembling the speaker unit to the rear wall of the box. [Figure 5] This shows another modification of the sound device of the first embodiment, where (A) is a partially enlarged cross-sectional view showing an enlarged portion of the cross-section of the sound device, and (B) is a partially enlarged cross-sectional view showing the process of assembling the speaker unit to the rear wall of the box. [Figure 6] This explains the preferred size of the auxiliary plate that constitutes the yoke of the magnetic circuit section. (A) is an enlarged cross-sectional view of a portion of Figure 3(A), and (B) is an enlarged cross-sectional view of a portion of Figure 5(A). [Figure 7] Partial enlarged cross-sectional view showing the acoustic device according to the second embodiment of the present invention,

Embodiments for Carrying out the Invention

[0018] The acoustic devices 1 and 101 according to the embodiments of the present invention are in-vehicle powered subwoofers, and are fixedly used on the floor surface in a space under a seat, for example, inside a vehicle cabin. In the acoustic device 1, the Y1 - Y2 direction is the front - rear direction, the Y1 direction is the front, and the Y2 direction is the rear. The main sound - emitting direction is the front (Y1 direction).

[0019] As shown in FIGS. 1 to 3, the acoustic device 1 according to the first embodiment has a box 10. As shown in FIG. 2, the box 10 has a rear wall portion 11 located in the rear (Y2 direction), a front wall portion 12 located in the front (Y1 direction) opposite to the rear wall portion 11, and side wall portions 13 covering four sides. The rear wall portion 11 is a bottom plate formed of a synthetic resin material or a non - magnetic metal material. The front wall portion 12 and the four - sided side wall portions 13 are integrally formed of a synthetic resin material or a metal material. As shown in FIG. 1, a circular opening 14 is formed to penetrate through the front wall portion 12 in the front - rear direction. As shown in FIG. 2, the integrally formed front wall portion 12 and side wall portions 13 are placed on the rear wall portion 11, thereby forming an internal space 15 of the box 10. The internal space 15 is a cube and functions as an enclosure in the acoustic device 1. In the internal space 15, a speaker unit 20 operating as a subwoofer and an electronic device including an amplifier circuit and a power supply circuit for driving the speaker unit 20 are housed.

[0020] As shown in Figure 2, the speaker unit 20 has a frame 21. The frame 21 is made of a non-magnetic or magnetic material and has a tapered shape with a diameter that gradually widens towards the front (Y1 direction). A magnetic circuit section 30 is fixed to the rear (Y2 direction) of the frame 21. The magnetic circuit section 30 is a so-called external magnet type and has a ring-shaped drive magnet 31. A center yoke 32 is provided on the magnetic circuit section 30. The center yoke 32 is integrally formed with a center pole 32a located inside the drive magnet 31 and a rear plate 32b that protrudes outward from the rear of the center pole 32a, and the drive magnet 31 is fixed to the front surface of the rear plate 32b. A ring-shaped front plate 33 is fixed to the front surface of the drive magnet 31. The front plate 33 is located on the outer circumference of the center pole 32a, and a magnetic gap G is formed between the inner surface of the front plate 33 and the outer surface of the center pole 32a. As shown in Figures 2 and 3(A), the yoke constituting the magnetic circuit section 30 has an auxiliary plate 35 in its rear portion. The auxiliary plate 35 is separated from the rest of the yoke and is magnetically attached to the rear surfaces of the center pole 32a and the rear plate 32b. The center yoke 32, the front plate 33, and the auxiliary plate 35 constitute the yoke of the magnetic circuit section 30, and these are made of a magnetic material, i.e., a magnetic metal material such as iron.

[0021] As shown in Figures 3(A) and 3(B), the auxiliary plate 35 and the rear wall portion 11 of the box 10 are integrated by insert molding. That is, the auxiliary plate 35 is held in the cavity of the mold, and molten resin material is injected into the cavity, thereby integrating the rear wall portion 11 and the auxiliary plate 35. As shown in Figure 3(B), the front surface 35a of the auxiliary plate 35 is flush with the front surface 11a of the rear wall portion 11, and the rear surface 35b of the auxiliary plate 35 is flush with the rear surface 11b of the rear wall portion 11. The rear surface 35b of the auxiliary plate 35 may be covered with a portion of the resin material that constitutes the rear wall portion 11, but by making the rear surface 35b of the auxiliary plate 35 and the rear surface 11b of the rear wall portion 11 flush, the thickness dimension of the auxiliary plate 35 that constitutes part of the yoke can be maximized.

[0022] As shown in Figure 2, a diaphragm 22 is provided inside the frame 21 of the speaker unit 20. The diaphragm 22 is tapered (cone-shaped), and a bobbin 23 is fixed to its center. A voice coil 24 is wound around the rear end of the bobbin 23, and the voice coil 24 is inserted into the magnetic gap G of the magnetic circuit section 30. A cap member 27 is attached to the front of the diaphragm 22, which closes the hollow cylindrical portion of the bobbin 23 from the front. The outer periphery of the diaphragm 22 is supported by the frame 21 via an elastically deformable edge member 25, and the outer periphery of the bobbin 23 is supported by the frame 21 via an elastically deformable damper member 26. Due to the elastic deformation of the edge member 25 and the damper member 26, the vibrating section, including the diaphragm 22, bobbin 23, and voice coil 24, is supported to vibrate freely in the front-rear direction (Y1-Y2 direction). The magnetic circuit section 30 and the voice coil 24 constitute a magnetic drive unit that drives the vibrating section, including the diaphragm 22, in the forward and backward directions.

[0023] As shown in Figure 3(B), a female screw hole 32c is machined into the rear surface 32d of the center pole 32a of the center yoke 32, and a screw insertion hole 35c is formed in the auxiliary plate 35. In the assembly process of the sound device 1, the speaker unit 20 is installed on the front surface 35a of the rear wall 35. The rear surface 32d of the center yoke 32 is attracted to the front surface 35a of the auxiliary yoke 35 by the magnetic force of the drive magnet 31, and the speaker unit 20 is further fixed to the front surface 35a of the rear wall 35 by inserting the fixing screw 5 into the screw insertion hole 35c and screwing it into the female screw hole 32c. Then, the center yoke 32 and the auxiliary plate 35 are magnetically joined, and the auxiliary plate 35 comes to function as part of the yoke of the magnetic circuit section 30.

[0024] After fixing the speaker unit 20 to the front surface 35a of the auxiliary plate 35, the speaker unit 20 is covered by the upper part of the box, which is an integrated front wall 12 and side wall 13, and the side wall 13 is fixed to the rear wall 11. At this time, as shown in Figure 2, the front end peripheral portion 21a of the frame 21 of the speaker unit 20 abuts against the outer surface of the opening 14 in the front wall 12. As a result, the diaphragm 22 and cap member 27 of the speaker unit 20 are exposed inside the opening 14, and the sound pressure generated by the vibration of the diaphragm 22 can be released from the opening 14 into the external space in front (Y1 direction).

[0025] In the sound device 1, which operates as a powered woofer, the low-frequency components of the audio signal are supplied to the voice coil 24 from the amplifier circuit of the electronic device built into the box 10, causing the diaphragm 22 to vibrate back and forth at low frequencies. Because the internal space 15 of the box 10 is a small, sealed space, the air inside the internal space 15 easily acts as a damper to suppress the vibration of the diaphragm 22. In order to drive the diaphragm 22 with a large amplitude to overcome air resistance, it is necessary to increase the mass of the vibrating system including the diaphragm 22 and to use a large, powerful drive magnet 21 to drive the heavy vibrating system. In addition, the drive magnet 21 needs to have a large thickness in the front-to-back direction, which is the magnetization direction, in order to suppress demagnetization. As a result, the front-to-back dimension of the magnetic circuit section 30 becomes large, but in this sound device 1, the auxiliary plate 35 embedded in the rear wall 11 of the box 10 functions as part of the yoke, so the front-to-back space occupied by the magnetic circuit section 30 in the internal space 15 of the box 10 can be saved, making it possible to make the overall dimensions of the box 10 thin.

[0026] Figures 4(A) and 4(B) show modified examples of the acoustic device 1 of the first embodiment. In the acoustic device 1 shown in Figure 4, a circular hole 11c is opened in the rear wall portion 11 of the box 10. A stepped portion 11d is formed on the periphery of the hole 11c, widening towards the rear (Y2 direction). The auxiliary plate 135 is formed separately from the center yoke 32 and is also formed separately from the rear wall portion 11. The auxiliary plate 135 has a flange portion 135b that protrudes outwards from the rear side of its periphery.

[0027] In the assembly process of the sound device 1, as shown in Figure 4(B), the speaker unit 20 is installed on the front surface 11a of the rear wall portion 11 from the front, and the auxiliary plate 135 is inserted into the hole 11c of the rear wall portion 11 from the rear. As shown in Figure 4(A), when the flange portion 135b of the auxiliary plate 135 is fitted into the stepped portion 11d of the peripheral edge of the hole 11c, the auxiliary plate 135 is positioned relative to the rear wall portion 11, and the front surface 11a of the rear wall portion 11 and the front surface 135a of the auxiliary plate 135 become flush. With the center yoke 32 and the auxiliary plate 135 attracted to each other by the magnetic force of the drive magnet 31, the center yoke 32 and the auxiliary plate 135 are fixed to each other by the fixing screws 5.

[0028] Figures 5(A) and (B) show other modifications of the acoustic device 1 of the first embodiment. In this acoustic device 1, a center pole 132a and a rear plate 132b that protrudes outward from the rear of the center yoke 132 are formed on a center yoke 132 provided on the magnetic circuit section 30, and an auxiliary plate 132c that protrudes rearward from the center pole 132a and the rear plate 132b is integrally formed. As shown in Figure 5(B), a circular hole 11c that penetrates from front to back is formed in the rear wall section 11. In the assembly process, the speaker unit 20 is assembled to the rear wall section 11 from the front, and the auxiliary plate 132c that protrudes from the center yoke 132 is inserted into the hole 11e of the rear wall section 11. The rear plate 132b and the rear wall section 11 are fixed together by adhesive or screws. As shown in Figure 5(A), once the assembly is complete, the rear surface 132d of the auxiliary plate 132c and the rear surface 11b of the rear wall portion 11 become the same plane.

[0029] Figure 6(A) is a partially enlarged view of Figure 3(A). The front-to-rear thickness dimension H2 of the rear plate 32b is smaller than the thickness dimension of the front plate 33. The sum of the front-to-rear thickness dimensions H3 of the rear plate 32b and the auxiliary plate 35 is equal to or greater than the thickness dimension H1 of the front plate 33. Figure 6(B) is a partially enlarged view of Figure 5(A), and in Figure 6(B) as well, the front-to-rear thickness dimension H2 of the rear plate 132b is smaller than the thickness dimension H1 of the front plate 33. The sum of the front-to-rear thickness dimensions H3 of the rear plate 32b and the auxiliary plate 132c is equal to or greater than the thickness dimension H1 of the front plate 33. In the acoustic device 1, the thinness of the rear plates 32b and 132b saves space in the front-to-back direction within the internal space 15 of the box 10. However, the large sum of the thickness dimensions of the rear plates 32b and 132b and the auxiliary plates 35 and 132c allows for the suppression of magnetic saturation of the magnetic flux circulating within the yoke in the magnetic circuit section 30.

[0030] As shown in Figure 6(A), in the magnetic circuit section 30, a gap 38 is formed that extends backward (in the Y2 direction) from the magnetic gap G, and the outer inner surface 38a of the gap 38 coincides with the inner surface 31a of the drive magnet 31 (the inner surface of the central hole of the ring-shaped drive magnet 31). In Figure 6(A), the magnetic flux lines mf flowing through the yoke of the magnetic circuit section 30 are schematically shown, but in the yoke located behind the drive magnet 31, the magnetic flux density passing through is high in the region 40 near the position of the outer inner surface 38a of the gap 38, making magnetic saturation likely to occur. For this reason, it is necessary that the rear plate 32b and the auxiliary plate 35 overlap at the position of the outer inner surface 38a of the gap 38. That is, the contact portion 39 between the outer end of the auxiliary plate 35 and the rear plate 32b must be located outside (on the outer circumference side) of the outer inner surface 38a of the gap 38. In the cross-sectional view shown in Figure 6(A), if the width dimension from the outer inner surface 38a to the contact portion 39 is W2, and the width dimension from the outer inner surface 38a to the outer peripheral edge of the rear plate 32b is W1, then W2 must be greater than zero and less than or equal to W1 (W1≧W2>0).

[0031] In Figure 6(B), the contact portion 39 between the outer end of the auxiliary plate 35 and the rear plate 132b is close to the outer inner surface 38a, and the width dimension W2 is less than or equal to 1 / 4 of the width dimension W1. In this modified example as well, the rear plate 132b and the auxiliary plate 132c overlap on the outer inner surface 38a, and the thickness dimension of the yoke is large, H3, so magnetic saturation is less likely to occur in the region 40 near the position of the outer inner surface 38a where the magnetic flux density is high.

[0032] Figure 7 shows a part of the acoustic device 101 according to a second embodiment of the present invention. The magnetic circuit section 230 of the speaker unit provided in the acoustic device 101 is a so-called internal magnet type. The drive magnet 231 is located inside the magnetic gap G, and a front inner plate 233a is fixed in front of the drive magnet 231. A rear yoke 232 is fixed behind the drive magnet 231. The rear yoke 232 is an integrated part of a rear plate 232b joined to the rear surface of the drive magnet 231 and an outer peripheral yoke 232a located on the outer circumference. An auxiliary plate 35 is embedded in the rear wall 11 by insert molding, and the rear plate 232b and the auxiliary plate 35 are magnetically coupled, and the rear plate 232b and the auxiliary plate 35 are fixed together with fixing screws 5.

[0033] In the internal magnetic circuit section 230 shown in Figure 7, the magnetic flux density passing through the yoke is high in the region 40 including the outer inner surface 38a of the gap 38. In the acoustic device 101, the rear yoke 232b and the auxiliary plate 35 are superimposed at the position of the outer inner surface 38a of the gap 38 that is continuous to the rear from the magnetic gap G, and the thickness dimension in the front-rear direction of the yoke formed behind the drive magnet 231 is increased. Therefore, it is possible to reduce the internal resistance to magnetic flux in the aforementioned region. [Explanation of symbols]

[0034] 1,101 Sound equipment 10 boxes 11 Rear wall 12 Front wall 13 Side wall section 14 Opening 20 speaker units 22 Diaphragm 30,230 Magnetic circuit section 31,231 drive magnets 33 Front plate 32b, 132b, 232b Rear Plate 35,132c Auxiliary plate 38 gaps 38a outer inner surface 39 Contact area

Claims

1. In an acoustic device having a box and a speaker unit housed in the internal space of the box, The box has a front wall portion having an opening, and a rear wall portion facing the front wall portion. The speaker unit comprises a frame, a diaphragm supported by the frame so as to be freely vibrable, a voice coil that vibrates together with the diaphragm, and a magnetic circuit section that applies a magnetic field to the voice coil, wherein the magnetic circuit section comprises a magnet and a yoke made of a magnetic material, and a magnetic gap is formed in a part of the yoke in which the voice coil is located. An acoustic device characterized in that the sound pressure emitted from the diaphragm can be released into the external space through the opening, and a part of the yoke is located inside the rear wall.

2. The acoustic device according to claim 1, wherein the yoke has a front plate that contacts the front of the magnet, a rear plate that contacts the rear of the magnet, and an auxiliary plate located inside the rear wall, and the rear plate and the auxiliary plate are magnetically connected.

3. The acoustic device according to claim 2, wherein the thickness dimension of the rear plate in the front-rear direction is smaller than the thickness dimension of the front plate in the front-rear direction, and the sum of the thickness dimensions of the rear plate and the auxiliary plate in the front-rear direction is equal to or greater than the thickness dimension of the front plate.

4. The acoustic device according to claim 2, wherein a gap is formed in the yoke that is continuous with the magnetic gap to the rear, and the contact portion between the outer end of the auxiliary plate and the rear plate is located outside the outer inner surface of the gap.

5. The acoustic device according to any one of claims 2 to 4, wherein the auxiliary plate is formed separately from the rear plate.

6. The acoustic device according to claim 5, wherein the auxiliary plate is embedded in the interior of the rear wall portion by insert molding.

7. The acoustic device according to claim 5, wherein a hole is formed in the rear wall and the auxiliary plate is inserted into the hole.

8. The rear plate and the auxiliary plate are formed integrally, The acoustic device according to any one of claims 2 to 4, wherein the auxiliary plate is located inside the hole formed in the rear wall.

9. The sound device according to any one of claims 1 to 4, wherein an electronic device is built into the box together with the speaker unit.

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