Patent Grant
8498442
The present invention relates to a loudspeaker, a video device including the loudspeaker, and a portable information processing apparatus including the loudspeaker, and more particularly to a small-size loudspeaker capable of wideband reproduction, a video device including the loudspeaker, and a portable information processing apparatus including the loudspeaker.
Recently, particularly in mobile phones among portable information processing apparatuses, sets are being downsized and thinned with multi-functionalization such as installation of cameras, stereo reproduction of ringtone melodies, and the like, and with size increase of liquid crystal screens. This makes it difficult to obtain a space for placing a loudspeaker within a mobile phone set, and there is a demand for downsizing a receiver which is a loudspeaker for reproducing a reception sound of a mobile phone and downsizing a micro loudspeaker for reproducing a ringtone and/or a music signal.
In addition, not only mobile phones but also video devices, such as flat-screen televisions, including PDPs (Plasma Display Panels), liquid crystal panels, or the like are desired to be further thinned and frame-narrowed by narrowing outer frames enclosing the PDPs or the liquid crystal panels to a maximum extent in order to make screens appear larger according to a design demand. Therefore, loudspeakers installed in the flat-screen televisions are also desired to have small and slim shapes with narrow widths.
Further, in a receiver of a mobile phone, for example, as a mobile phone system advances from the third generation to the fourth generation, expansion of a low frequency range for a wider reproduction range is also desired.
As described above, downsizing and widening of a reproduction range are demanded in loudspeakers of mobile phones and flat-screen televisions.
In a conventional loudspeaker structure, however, downsizing causes a support (an edge, a damper, and the like) which vibratably supports a diaphragm to be reduced in width and accordingly to be increased in stiffness. As a result, the lowest resonance frequency of the loudspeaker becomes higher to fail to expand a low frequency range, which makes it difficult to widen a reproduction range. Thus, in the conventional loudspeaker structure, it is difficult to realize both downsizing and widening of a reproduction range.
As one of prior arts for solving this problem, a loudspeaker disclosed in Patent Document 1 has been proposed.
The magnet 2 is fixed to an inner bottom surface of the yoke 1 which has a box-like shape with an upper surface thereof opened. The plate 3 is fixed to an upper surface of the magnet 2. A magnetic gap G1 is formed between the yoke 1 and the plate 3. Thus, the yoke 1, the magnet 2, and the plate 3 constitute a magnetic circuit having the magnetic gap G1. The voice coil 4 is provided on the outer circumference of the diaphragm 5 and positioned within the magnetic gap G1. The butterfly damper 6 is a support that vibratably supports the diaphragm 5, and provided on the outer circumference of the diaphragm 5. The magnet 7 is provided on the outer circumference of the diaphragm 5. The magnetic fluid 8, which is held by magnetic force of the magnet 7, vibrates the diaphragm 5 in a stable manner because of its viscosity.
Operations and effects of the loudspeaker shown in
Further, even when the loudspeaker is downsized so that the width of the butterfly damper 6 is reduced, the butterfly damper 6 can show high stroke performance by increasing a length of a joint portion of the butterfly damper 6. Therefore, in the loudspeaker shown in
As described above, the loudspeaker shown in
However, in the loudspeaker shown in
Further, in the loudspeaker shown in
Therefore, an object of the present invention is to provide a loudspeaker capable of realizing both of downsizing and widening of a reproduction range and reducing non-linear distortion by a support as well as further improving a sound quality and efficiency, a video device including the loudspeaker, and a portable information processing apparatus including the loudspeaker.
To solve the conventional problems, a loudspeaker according to the present invention comprises: a diaphragm that vibrates back and forth to emit a sound; a magnetic circuit that is provided on a rear side of the diaphragm and has a magnetic gap on a diaphragm side; a voice coil that is directly or indirectly joined to the diaphragm and disposed within the magnetic gap; a magnetic fluid that is loaded within the magnetic gap; and a plurality of first edge pieces that are provided at different positions in an outer circumferential portion of the diaphragm for vibratably supporting the diaphragm, each of the first edge pieces having a non-linear cross-sectional shape.
According to the structure described above, a support that vibratably supports the diaphragm is formed by the plurality of edge pieces which are provided at the different positions in the outer circumferential portion of the diaphragm and each of which has a non-linear cross-sectional shape. As a result, even when the loudspeaker is downsized, the support has the reduced stiffness so that the lowest resonance frequency of the loudspeaker can be lowered to enable a reproduction range to be widened. Moreover, since a cross-sectional shape of the first edge piece is a non-linear shape, non-linear distortion by the support can be reduced. Further, unlike the conventional loudspeaker, there is no need for using the butterfly damper 6 and the magnet 7, and therefore a sound quality and efficiency can be improved. Further, unlike the conventional loudspeaker, the magnetic fluid is loaded within the magnetic gap, and therefore it is possible to prevent burnout of the voice coil which may be caused upon a large input and to suppress rolling motions of the voice coil so that the voice coil can vibrate in a stable manner.
Preferably, the diaphragm and each of the first edge pieces are formed integrally with each other. Alternatively, the diaphragm and each of the first edge pieces may be formed as separate pieces. Preferably, a cross-sectional shape of each of the first edge pieces is a curved shape or a corrugated shape. Preferably, a cross-sectional shape of the diaphragm is convex toward a front of the diaphragm. Alternatively, a cross-sectional shape of the diaphragm may be a linear shape. In this case, it may further be possible that a rib is formed on the diaphragm.
Preferably, the magnetic circuit includes: a yoke that has a box-like shape with its face on the diaphragm side being opened; a magnet that is fixed to an inner bottom surface of the yoke; and a plate that is fixed to a face of the magnet on the diaphragm side and cooperates with the yoke to form the magnetic gap therebetween; the magnetic fluid is loaded within the magnetic gap at least on an inner circumference side of the voice coil; and a hole is formed in the yoke, the magnet, and the plate so as to extend through the yoke, the magnet, and the plate.
Preferably, a relationship of f2/f1≦2 is satisfied where f1 represents the lowest resonance frequency of the loudspeaker without the magnetic fluid being loaded within the magnetic gap and f2 represents the lowest resonance frequency of the loudspeaker with the magnetic fluid being loaded within the magnetic gap.
Preferably, an end of each of the first edge pieces, which is joined to the outer circumferential portion of the diaphragm, is positioned inside an outer circumferential end of the diaphragm.
Preferably, an outer shape of the diaphragm seen from a front side thereof is a rectangular shape, and the first edge pieces are provided at either one of two pairs of opposed sides of the diaphragm. In this case, further preferably, the outer shape of the diaphragm is a rectangle, and the first edge pieces are provided at two short sides of the diaphragm.
Alternatively, it is advantageous that: the magnetic circuit includes: a yoke that is formed with a box-like shape with its face on the diaphragm side being opened and whose outer shape is a rectangular shape when seen from a front side of the diaphragm; a magnet that is fixed to an inner bottom surface of the yoke; and a plate that is fixed to a face of the magnet on the diaphragm side and cooperates with the yoke to form the magnetic gap therebetween; and first side walls of the yoke, which are opposed respectively to a pair of sides of the diaphragm at which the first edge pieces are not provided, are higher than second side walls of the yoke, which are opposed respectively to a pair of sides of the diaphragm at which the first edge pieces are provided. In this case, further advantageously, the loudspeaker further comprises a protector that is provided on the first side walls of the yoke so as to cover the front side of the diaphragm with interposition of a gap.
Preferably, the loudspeaker further comprises: a voice coil bobbin that is joined to the diaphragm for positioning the voice coil within the magnetic gap; and a plurality of second edge pieces that are provided at different positions on an outer circumference of the voice coil bobbin for vibratably supporting the voice coil bobbin, each of the second edge pieces having a non-linear cross-sectional shape.
Preferably, the voice coil is directly joined to the diaphragm; the magnetic fluid is loaded within the magnetic gap at least on an inner circumference side of the voice coil; and an inner shape of the voice coil seen from a front side of the diaphragm is a rectangular shape with corners rounded at a radius of 1 mm or larger.
Preferably, the magnetic circuit includes: a yoke that has a box-like shape with its face on the diaphragm side being opened; a magnet that is fixed to an inner bottom surface of the yoke; and a plate that is fixed to a face of the magnet on the diaphragm side and cooperates with the yoke to form the magnetic gap therebetween; the magnetic fluid is loaded within the magnetic gap on inner and outer circumference sides of the voice coil; and an air hole is formed in the yoke so as to pass air between outside of the yoke and a space that is formed within the yoke by being enclosed by the yoke, the magnet, the plate, the magnetic fluid, and the voice coil.
The present invention is also directed to a video device and a portable information processing apparatus, and the video device and the portable information processing apparatus according to the present invention comprise the above-described loudspeaker according to the present invention and a housing for the loudspeaker to be disposed therein.
According to the present invention, there can be provided a loudspeaker capable of realizing both of downsizing and widening of a reproduction range and reducing non-linear distortion by a support as well as further improving a sound quality and efficiency, a video device including the loudspeaker, and a portable information processing apparatus including the loudspeaker.
a)-1(c) show a structural example of a loudspeaker according to Embodiment 1.
a) and 2(b) show a structural example of a loudspeaker according to Embodiment 2.
a) and 3(b) show a structural example of a loudspeaker according to Embodiment 3.
a) and 4(b) show a structural example of a loudspeaker according to Embodiment 4.
a) and 5(b) show a structural example of a loudspeaker according to Embodiment 5.
a) and 6(b) show a structural example of a loudspeaker according to Embodiment 6.
a) and 7(b) show a structural example of a loudspeaker according to Embodiment 7.
a) and 8(b) show a structural example of a loudspeaker according to Embodiment 8.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A structure of a loudspeaker according to Embodiment 1 of the present invention will be described with reference to
Referring to
As shown in
As shown in
Here, the “non-linear shape” mentioned above means not being a linear shape. In other words, referring to an example shown in
The voice coil 16 is provided at the outer circumferential portion of the diaphragm 13 and positioned within the magnetic gap G2. In addition to the voice coil 16, the magnetic fluid 17 is also loaded in the magnetic gap G2. The magnetic fluid 17 holds the voice coil 16 within the magnetic gap G2 by means of its viscosity, to vibrate the voice coil 16 in a stable manner. In the present embodiment, the magnetic fluid 17 is loaded only on an inner circumference side of the voice coil 16 within the magnetic gap G2.
Operations and effects of the loudspeaker configured as above will be described. When a music signal is applied to the voice coil 16, the diaphragm 13 vibrates back and forth (in an up and down direction in
Further, since each of the edge pieces 14a to 14d has a curved cross-sectional shape, linearity against large amplitude of the diaphragm 13 can be ensured even when the loudspeaker is downsized, so that the width of each of the edge pieces 14a to 14d (corresponding to D2 in (c) of
Further, unlike a conventional loudspeaker shown in
As described above, according to the present embodiment, there can be provided the loudspeaker capable of realizing both of downsizing and widening of a reproduction range and reducing non-linear distortion by the support as well as further improving a sound quality and efficiency.
In addition, in the present embodiment, unlike in the conventional loudspeaker, the magnetic fluid 17 is loaded within the magnetic gap G2. As a result, heat generation of the voice coil 16 can be suppressed by a cooling effect of the magnetic fluid 17, and burnout of the voice coil 16 which may be caused upon a large input can be prevented.
Moreover, in the present embodiment, unlike in the conventional loudspeaker, the sound hole H1 is formed. This can prevent the lowest resonance frequency of the loudspeaker from becoming higher because of the air stiffness of a space that exists on the rear surface of the diaphragm 13 and is closed by the magnetic fluid 17. Further, it is also possible to utilize a sound from the sound hole H1 as a reproduction sound of the loudspeaker.
In the above description, the edge pieces 14a to 14d are made of the same material as that of the diaphragm 13, but the present invention is not limited thereto. For example, the edge pieces 14a to 14d may be made of a material softer than the diaphragm 13. In this case, the stiffness of the edge pieces 14a to 14d can be further reduced, so that a reproduction limit of a low frequency range can be further expanded. In this case, furthermore, by making the diaphragm 13 from a material having high rigidity, a reproduction limit of a high frequency range can also be expanded, to further widen the reproduction range.
In the above description, there is no mention of the material thickness of the edge pieces 14a to 14d, but the material thickness may be the same as that of the diaphragm 13 or may be smaller than that of the diaphragm 13. When the material thickness of the edge pieces 14a to 14d is smaller than that of the diaphragm 13, the stiffness of the edge pieces 14a to 14d can be further reduced, so that a reproduction limit of a low frequency range can be further expanded.
In the above description, the edge pieces 14a to 14d are formed integrally with the diaphragm 13, but the edge pieces 14a to 14d and the diaphragm 13 may be formed as separate pieces. In this case, the edge pieces 14a to 14d are joined to the outer circumferential end of the diaphragm 13 by bonding or welding.
In the above description, a cross-sectional shape of each of the edge pieces 14a to 14d is a curved shape, but it may be any shape as long as it is a non-linear shape. For example, it may be a corrugated shape.
In the above description, four edge pieces 14a to 14d are used as the support, but two or three edge pieces may be used. The number of edge pieces is not limited to four.
A structure of a loudspeaker according to Embodiment 2 of the present invention will be described with reference to
Referring to
As shown in
As shown in
The voice coil 26 is provided at the outer circumferential portion of the diaphragm 23 and positioned within the magnetic gap G3. In addition to the voice coil 26, the magnetic fluid 27 is also loaded in the magnetic gap G3. The magnetic fluid 27 holds the voice coil 26 within the magnetic gap G3 by means of its viscosity, to vibrate the voice coil 26 in a stable manner. In the present embodiment, the magnetic fluid 27 is loaded on each of inner and outer circumferences of the voice coil 26 within the magnetic gap G3.
A space R1 enclosed by the yoke 20, the magnet 21, the plate 22, the voice coil 26, and the magnetic fluid 27 is formed within the yoke 20. In the present embodiment, since the magnetic fluid 27 is loaded on each of the inner and outer circumferences of the voice coil 26, the space R1 is closed. Further, an air hole H3 is formed in the yoke 20 so as to pass air between the space R1 and the outside of the yoke 20.
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 1, when a music signal is applied to the voice coil 26, a sound is emitted from the diaphragm 13 and a sound from a rear surface of the diaphragm 23 is emitted through the sound hole H2. A great difference from Embodiment 1 is that the outer shape of the diaphragm 23 on the front side thereof is a rectangle, as described above. By forming the outer shape of the diaphragm 23 on the front side thereof into a rectangle and making the support from the edge pieces 24a and 24b, there is formed no corner on which stress particularly concentrates, and therefore the stiffness of the edge pieces 24a and 24b considerably decreases as compared with the normal edge that is formed throughout the outer circumferential portion of the diaphragm 23. As a result, the lowest resonance frequency of the loudspeaker can be considerably lowered. Thus, the structure of the loudspeaker according to the present embodiment provides a great advantage in downsizing and/or slimming the rectangle loudspeaker.
As described above, the structure of the loudspeaker according to the present embodiment is suitable for a rectangle loudspeaker capable of realizing both of downsizing and widening of a reproduction range and reducing non-linear distortion by the support as well as further improving a sound quality and efficiency.
In addition, according to the present embodiment, no edge is positioned at long sides of the diaphragm 23. Therefore, an effective vibration area of the diaphragm 23 can be easily expanded in a direction parallel to the short sides (an up and down direction in
Moreover, according to the present embodiment, the air hole H3 is formed in the yoke 20. Air trapped in the closed space R1 expands and contracts due to a temperature rise of the voice coil 26 and a pressure change of the operating environment of the loudspeaker. Due to the air thus expanding and contracting, stretching force is applied to the magnetic fluid 27, which may undesirably cause the magnetic fluid 27 to overflow from the magnetic gap G3. However, such a risk can be avoided because the air hole H3 suppresses variations in air pressure within the space R1.
In the above description, the edge pieces 24a and 24b are made of the same material as that of the diaphragm 23, but the present invention is not limited thereto. For example, the edge pieces 24a and 24b may be made of a material softer than the diaphragm 23. In this case, the stiffness of the edge pieces 24a and 24b can be more reduced, so that a reproduction limit of a low frequency range can be more expanded. In this case, furthermore, by making the diaphragm 23 from a material having high rigidity, a reproduction limit of a high frequency range can also be expanded, to further widen the reproduction range.
In the above description, there is no mention of the material thickness of the edge pieces 24a and 24b, but the material thickness may be the same as that of the diaphragm 23 or may be smaller than that of the diaphragm 23. When the material thickness of the edge pieces 24a and 24b is smaller than that of the diaphragm 23, the stiffness of the edge pieces 24a and 24b can be further reduced, so that a reproduction limit of a low frequency range can be further expanded.
In the above description, the edge pieces 24a and 24b are formed integrally with the diaphragm 23, but the edge pieces 24a and 24b and the diaphragm 23 may be formed as separate pieces. In this case, the edge pieces 24a and 24b are joined to the outer circumferential end of the diaphragm 23 by bonding or welding.
In the above description, a cross-sectional shape of each of the edge pieces 24a and 24b is a curved shape, but it may be any shape as long as it is a non-linear shape. For example, it may be a corrugated shape.
In the above description, one edge piece is provided at each of the short sides of the diaphragm 23, but the present invention is not limited thereto. It may be possible that two or three edge pieces are provided at each of the short sides of the diaphragm 23. This further reduces the stiffness of the support, so that the lowest resonance frequency of the loudspeaker is further lowered.
In the above description, each of the short sides of the diaphragm 23 is provided with the edge piece, but the present invention is not limited thereto. For example, each of long sides of the diaphragm 23 may be provided with the edge piece. In this case, an effective vibration area of the diaphragm 23 decreases as compared with the edge piece being provided at each short side. However, a length of the edge piece supporting the diaphragm 23 becomes longer. Therefore, the diaphragm 23 can more stably be supported. Alternatively, for example, it may be possible to provide edge pieces at each short side and at each long side of the diaphragm 23.
In the above description, the outer shape of the loudspeaker is a rectangle when seen from the front side thereof, but the present invention is not limited thereto. It suffices that the outer shape of the loudspeaker according to the present embodiment is a rectangular shape when seen from the front side thereof. It may be a square shape for example. In this case, the outer shapes of the yoke 20, the magnet 21, the plate 22, the diaphragm 23, and the voice coil 26 on the front side thereof correspond to the outer shape of the loudspeaker as seen from the front side thereof.
In the above description, the magnetic fluid 27 is loaded on each of the inner and outer circumferences of the voice coil 26, but the magnetic fluid 27 may be loaded only on the inner circumference side of the voice coil 26. In this case, it is not necessary to form the air hole H3 in the yoke 20, because the space R1 is not closed.
A structure of a loudspeaker according to Embodiment 3 of the present invention will be described with reference to
Referring to
The diaphragm 30 has a plate shape, and its cross-sectional shape is a linear shape as shown in
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 2, when a music signal is applied to the voice coil 26, a sound is emitted from the diaphragm 30 and a sound from a rear surface of the diaphragm 30 is emitted through the sound hole H2. A great difference from Embodiment 2 is that the diaphragm 30 has the plate shape and that the plurality of ribs L1 are formed on the diaphragm 30, as described above. By adopting the plate-shaped diaphragm 30, the total thickness of the loudspeaker (a length of the loudspeaker in an up and down direction in
As described above, according to the present embodiment, the total thickness of the loudspeaker can be reduced and a reproduction limit of a high frequency range can be more expanded, as compared with in Embodiment 2.
In the above description, the edge pieces 24a and 24b are made of the same material as that of the diaphragm 30, but the present invention is not limited thereto. For example, the edge pieces 24a and 24b may be made of a material softer than the diaphragm 30. In this case, furthermore, the diaphragm 30 may be made of a material having high rigidity. In the above description, in addition, there is no mention of the material thickness of the edge pieces 24a and 24b, but the material thickness may be the same as that of the diaphragm 30 or may be smaller than that of the diaphragm 30. In the above description, moreover, the edge pieces 24a and 24b are formed integrally with the diaphragm 30, but the edge pieces 24a and 24b and the diaphragm 30 may be formed as separate pieces. In this case, the edge pieces 24a and 24b are joined to an outer circumferential end of the diaphragm 30 by bonding or welding.
In the above description, the rigidity of the diaphragm 30 is increased by forming the plurality of ribs L1 on the diaphragm 30, but the present invention is not limited thereto. For example, the rigidity may be increased by forming one rib L1 on the diaphragm 30. Alternatively, the rigidity may be increased for example by adopting, as an internal structure of the diaphragm 30, a sandwich structure in which a honeycomb-shaped core is sandwiched by plate-shaped surface materials.
A structure of a loudspeaker according to Embodiment 4 of the present invention will be described with reference to
Referring to
The edge pieces 40a and 40b are a support that vibratably supports the diaphragm 23, and provided at an outer circumferential portion of the diaphragm 23. The edge pieces 40a and 40b are made of the same material as that of the diaphragm 23. The edge pieces 40a and 40b, and the diaphragm 23 are formed as separate pieces. The edge pieces 40a and 40b are members corresponding to parts of a normal edge that is formed throughout the outer circumferential portion of the diaphragm 23. In an example shown in
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 2, when a music signal is applied to the voice coil 26, a sound is emitted from the diaphragm 23 and a sound from a rear surface of the diaphragm 23 is emitted through a sound hole H2. A great difference from Embodiment 2 is that one end of each of the edge pieces 40a and 40b is located on the curved surface of the diaphragm 23, as described above. By locating the one end of the edge piece on the curved surface of the diaphragm 23, an extent of protruding of the edge piece beyond the outer circumferential end of the diaphragm 23 is reduced as compared with in Embodiment 2 where the one end of the edge piece is located at the outer circumferential end of the diaphragm 23. As a result, even though an outside dimension of the loudspeaker is the same as in Embodiment 2, an effective vibration area of the diaphragm 23 can be made larger and efficiency can be improved as compared with in Embodiment 2.
As described above, according to the present embodiment, efficiency can be improved as compared with in Embodiment 2.
In the above description, the edge pieces 40a and 40b are made of the same material as that of the diaphragm 23, but the present invention is not limited thereto. For example, the edge pieces 40a and 40b may be made of a material softer than the diaphragm 23. In this case, furthermore, the diaphragm 23 may be made of a material having high rigidity. In the above description, there is no mention of the material thickness of the edge pieces 40a and 40b, but the material thickness may be the same as that of the diaphragm 23 or may be smaller than that of the diaphragm 23.
In the above description, a cross-sectional shape of each of the edge pieces 24a and 24b is a curved shape, but it may be any shape as long as it is a non-linear shape. For example, it may be a corrugated shape.
In the above description, one edge piece is provided at a portion of the diaphragm 23 inside each short side thereof, but the present invention is not limited thereto. It may be possible that two or three edge pieces are provided at a portion of the diaphragm 23 inside each short side thereof. This further reduces the stiffness of the support, so that the lowest resonance frequency of the loudspeaker is more lowered.
A structure of a loudspeaker according to Embodiment 5 of the present invention will be described with reference to
Referring to
The diaphragm 50 has a plate shape, and its cross-sectional shape is a linear shape as shown in
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 4, when a music signal is applied to the voice coil 26, a sound is emitted from the diaphragm 50 and a sound from a rear surface of the diaphragm 50 is emitted through a sound hole H2. A great difference from Embodiment 4 is that the diaphragm 50 has a plate shape and that the edge pieces 51a to 51h are provided not only on the short sides but also on the long sides of the diaphragm 50, as described above.
By adopting the diaphragm 50 of plate shape, the total thickness of the loudspeaker (a length of the loudspeaker in an up and down direction in
As described above, according to the present embodiment, the total thickness of the loudspeaker can be reduced to support the diaphragm in a more stabilized manner than in Embodiment 4.
In the above description, the edge pieces 51a to 51h are made of the same material as that of the diaphragm 50, but the present invention is not limited thereto. For example, the edge pieces 51a to 51h may be made of a material softer than the diaphragm 50. In this case, furthermore, the diaphragm 50 may be made of a material having high rigidity. In addition, a rib may be formed on the diaphragm 50 in order to increase the rigidity of the diaphragm 50. In the above description, there is no mention of the material thickness of the edge pieces 51a to 51h, but the material thickness may be the same as that of the diaphragm 50 or may be smaller than that of the diaphragm 50.
In the above description, a cross-sectional shape of each of the edge pieces 51a to 51h is a curved shape, but it may be any shape as long as it is a non-linear shape. For example, it may be a corrugated shape.
In the above description, two edge pieces are provided at a portion of the diaphragm 50 inside each short side thereof and at a portion of the diaphragm 50 inside each long side thereof, but the present invention is not limited thereto. For example, it may be possible that three edge pieces are provided at a portion of the diaphragm 50 inside each short side thereof and at a portion of the diaphragm 50 inside each long side thereof.
A structure of a loudspeaker according to Embodiment 6 of the present invention will be described with reference to
Referring to
As shown in
The edge pieces 62a to 62d are provided at an outer circumferential portion of the diaphragm 23, as a support that vibratably supports the diaphragm 23. The edge pieces 62a to 62d are made of the same material as that of the diaphragm 23, and formed integrally with the diaphragm 23. As a result of the edge pieces 62a to 62d being formed integrally with the diaphragm 23, the number of components and assembling man-hours for the loudspeaker can be reduced. The edge pieces 62a to 62d are members corresponding to parts of a normal edge that is formed throughout the outer circumferential portion of the diaphragm 23. In an example shown in
The voice coil 26 is provided at the outer circumferential portion of the diaphragm 23 and positioned within the magnetic gaps G3 and G4. In addition to the voice coil 26, the magnetic fluid 27 is also loaded in the magnetic gaps G3 and G4. In the present embodiment, the magnetic fluid 27 is loaded only on an inner circumference side of the voice coil 26 within the magnetic gaps G3 and G4.
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 2, when a music signal is applied to the voice coil 26, a sound is emitted from the diaphragm 23 and a sound from a rear surface of the diaphragm 23 is emitted through the sound hole H2. A great difference from Embodiment 2 is that the long-side side wall 60b of the yoke 60 is higher than the short-side side wall 60a of the yoke 60, that the protector 61 is added, and that two edge pieces are provided at each short side of the diaphragm 23.
By making the long-side side wall 60b of the yoke 60 higher than the short-side side wall 60a of the yoke 60, magnetic flux within the magnetic gap G4 passing through the voice coil 26 flows substantially symmetrically about the plate 22 in a direction of vibration of the voice coil 26, as indicated by the reference character F in
Moreover, providing the protector 61 can prevent the diaphragm 23 from being externally damaged by accident.
Further, by providing two edge pieces at each short side of the diaphragm 23, the stiffness of the edge pieces can be further reduced as compared with in Embodiment 2, so that the lowest resonance frequency of the loudspeaker is further lowered.
As described above, according to the present embodiment, as compared with in Embodiment 2, a higher sound quality and a wider range can be realized, and damage to the diaphragm 23 can be prevented.
In the above description, the edge pieces 62a to 62d are made of the same material as that of the diaphragm 23, but the present invention is not limited thereto. For example, the edge pieces 62a to 62d may be made of a material softer than the diaphragm 23. In this case, furthermore, the diaphragm 23 may be made of a material having high rigidity. In the above description, there is no mention of the material thickness of the edge pieces 62a to 62d, but the material thickness may be the same as that of the diaphragm 23 or may be smaller than that of the diaphragm 23.
In the above description, a cross-sectional shape of each of the edge pieces 62a to 62d is a curved shape, but it may be any shape as long as it is a non-linear shape. For example, it may be a corrugated shape.
In the above description, two edge pieces are provided at each short side of the diaphragm 23, but the present invention is not limited thereto. For example, it may be possible that three edge pieces are provided at each short side of the diaphragm 23.
A structure of a loudspeaker according to Embodiment 7 of the present invention will be described with reference to
Referring to
The voice coil bobbin 70 is provided at an outer circumferential portion of the diaphragm 23. The voice coil 71 is provided on an outer circumference of the voice coil bobbin 70 and positioned within the magnetic gap G3. The edge pieces 72a and 72b are provided at an outer circumferential portion of the voice coil bobbin 70, as a support that vibratably supports the voice coil bobbin 70. Specifically, the edge piece 72a is provided on the outer circumference of the voice coil bobbin 70 so as to be immediately under the edge piece 24a, and the edge piece 72b is provided on the outer circumference of the voice coil bobbin 70 so as to be immediately under the edge piece 24b. Similarly to the edge pieces 24a and 24b, a cross-sectional shape of each of the edge pieces 72a and 72b is a curved shape, that is, a non-linear shape. The other end of each of the edge pieces 72a and 72b is located on an upper surface of a short-side side wall of the yoke 20 via the spacer 73. The other end of each of the edge pieces 24a and 24b is located on an upper surface of the other end of each of the edge pieces 72a and 72b via the spacer 74.
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 2, when a music signal is applied to the voice coil 26, a sound is emitted from the diaphragm 23 and a sound from a rear surface of the diaphragm 23 is emitted through a sound hole H2. A great difference from Embodiment 2 is that the edge pieces 72a and 72b are added. By adding the edge pieces 72a and 72b as the support, the voice coil 71 can more stably be held within the magnetic gap G3 even when the diaphragm 23 shows large amplitude. In combination with the cooling effect and the holding power due to the viscosity of the magnetic fluid 27, the loudspeaker with high input-resistance and high power output can be realized.
As described above, according to the present embodiment, the diaphragm and the voice coil can be supported in a more stabilized manner than in Embodiment 2.
In the above description, one edge piece is provided at each short side of the voice coil bobbin 70, but the present invention is not limited thereto. It may be possible that two or three edge pieces are provided at each short side of the voice coil bobbin 70. This further reduces the stiffness of the support, so that the lowest resonance frequency of the loudspeaker is further lowered.
In the above description, the edge piece is provided at each short side of the voice coil bobbin 70, but the present invention is not limited thereto. For example, in a case where the edge piece is provided at each long side of the diaphragm 23, the edge piece may accordingly be provided at each long side of the voice coil bobbin 70. For example, in addition, in a case where the edge piece is provided at each long side and at each short side of the diaphragm 23, the edge piece may accordingly be provided at each short side and at each long side of the voice coil bobbin 70.
In the above description, a cross-sectional shape of each of the edge pieces 72a and 72b is a curved shape, but it may be any shape as long as it is a non-linear shape. For example, it may be a corrugated shape.
A structure of a loudspeaker according to Embodiment 8 of the present invention will be described with reference to
Referring to
The magnet 80 is fixed to an inner bottom surface of the yoke 20 whose outer shape on the front side thereof is the track shape and which has a box-like shape with an upper surface thereof opened. The plate 81, whose outer shape on the front side thereof is the track shape, is fixed to an upper surface of the magnet 80. A magnetic gap G3 is formed between the yoke 20 and the plate 81. Thus, the yoke 20, the magnet 80, and the plate 81 constitute a magnetic circuit having the magnetic gap G3. A sound hole H2 is formed in the yoke 20, the magnet 80, and the plate 81 so as to extend along a central axis O through the yoke 20, the magnet 80, and the plate 81.
The diaphragm 82 has a plate shape, and its cross-sectional shape is a linear shape as shown in
The voice coil 83, whose outer shape and inner shape on the front side thereof are track shapes, is provided on the rib L2 of the diaphragm 82 and positioned within the magnetic gap G3. In addition to the voice coil 83, the magnetic fluid 27 is also loaded in the magnetic gap G3. In the present embodiment, the magnetic fluid 27 is loaded only on an inner circumference side of the voice coil 83 within the magnetic gap G3.
Operations and effects of the loudspeaker configured as above will be described. Similarly to in Embodiment 2, when a music signal is applied to the voice coil 83, a sound is emitted from the diaphragm 82 and a sound from a rear surface of the diaphragm 82 is emitted through the sound hole H2. A great difference from Embodiment 2 is that the diaphragm 82 has the plate shape and that the inner shape of the voice coil 83 on the front side thereof is the track shape.
By adopting the diaphragm 82 of plate shape, the total thickness of the loudspeaker (a length of the loudspeaker in an up and down direction in
Further, the front inner shape of the voice coil 83 is the track shape. In the following, effects obtained by this structure will be specifically described.
As shown in
In the recess B, on the other hand, the magnetic fluid creeping up does not reach an upper surface of the block. In the recess C, creeping-up of the magnetic fluid is hardly observed. This is because a larger corner radius can reduce a degree of contact between the magnetic fluid and an inner wall surface of the recess. That is, by setting a corner radius R of the front inner shape of the voice coil to 1.0 [m] or larger, creeping-up of the magnetic fluid from a corner can be prevented. As a result, a problem can be solved that a magnetic fluid creeps up from a magnetic gap over time to deteriorate sound pressure level characteristics.
As described above, according to the present embodiment, as compared with in Embodiment 2, the total thickness of the loudspeaker can be reduced, and a sound pressure level drop due to the magnetic fluid can be prevented.
In the above description, the edge pieces 24a and 24b are made of the same material as that of the diaphragm 82, but the present invention is not limited thereto. For example, the edge pieces 24a and 24b may be made of a material softer than the diaphragm 82. In this case, furthermore, the diaphragm 82 may be made of a material having high rigidity. In the above description, there is no mention of the material thickness of the edge pieces 24a and 24b, but the material thickness may be the same as that of the diaphragm 82 or may be smaller than that of the diaphragm 82. In the above description, the edge pieces 24a and 24b are formed integrally with the diaphragm 82, but the edge pieces 24a and 24b and the diaphragm 82 may be formed as separate pieces. In this case, the edge pieces 24a and 24b are joined to an outer circumferential end of the diaphragm 82 by bonding or welding.
In the above description, the rigidity of the diaphragm 82 is increased by forming the plurality of ribs L1 on the diaphragm 82, but the present invention is not limited thereto. For example, the rigidity may be increased by forming one rib L1 on the diaphragm 82. Alternatively, the rigidity may be increased for example by adopting, as an internal structure of the diaphragm 82, a sandwich structure in which a honeycomb-shaped core is sandwiched by plate-shaped surface materials.
The present embodiment describes an example of the loudspeakers according to Embodiments 1 to 8 described above being installed in a portable information processing apparatus.
In
Operations and effects of the mobile phone configured as above will be described. A reception signal received by an antenna (not shown) is processed in a signal processing section (not shown), and then inputted to the loudspeaker 94 to be converted into a reception sound.
Here, in a general loudspeaker, reproduction sound pressure level/frequency characteristics of the loudspeaker are measured by a microphone that is provided at a predetermined distance from the loudspeaker. On the other hand, in a receiver which is a loudspeaker that reproduces a reception sound, reproduction sound pressure level/frequency characteristics of the loudspeaker are measured by an acoustic coupler mounted on the loudspeaker. Generally used as the acoustic coupler are three types of acoustic couplers called Type 1, Type 3.2 low-leak, or Type 3.2 hi-leak according to the ITU (International Telecommunication Union) standard. Provided within these acoustic couplers is a narrow space in which a microphone is mounted, and the microphone measures reproduction sound pressure level/frequency characteristics of the receiver.
When the Type 1 acoustic coupler is mounted in the receiver, the above-mentioned space within the acoustic coupler is completely closed. Therefore, measured reproduction sound pressure level/frequency characteristics of the receiver are flat in a low frequency range equal to or lower than the lowest resonance frequency of the receiver. In the mobile phone, on the other hand, a reception sound is heard by putting the sound hole H5 to an ear, and it is difficult to completely close a space between the upper housing 90 of the mobile phone and the ear. Thus, the two types of acoustic couplers, namely the Type 3.2 low-leak or the Type 3.2 hi-leak, in which a sound hole for leaking a sound from the space within the acoustic coupler to the outside is formed, are used for measuring reproduction sound pressure level/frequency characteristics of a receiver under near actual-use conditions in which a user is using a mobile phone. A sound hole in the Type 3.2 low-leak is small so that low volume of sound is leaked through the sound hole, and a sound hole in the Type 3.2 hi-leak is large so that high volume of sound is leaked through the sound hole. This leaking of sound through the sound hole occurs mainly in the low frequency range. Therefore, when the acoustic coupler of Type 3.2 is used, reproduction sound pressure level/frequency characteristics are exhibited with sound pressure level in the low frequency range being considerably lowered as compared with when the acoustic coupler of Type 1 is used. Of course, the hi-leak acoustic coupler exhibits a greater decrease in sound pressure level in the low frequency range than the low-leak acoustic coupler. In recent years, since the liquid crystal screen 93 of the mobile phone becomes larger, the receiver is installed in the vicinity of an upper outer frame of the upper housing 90. Below the receiver, the liquid crystal screen 93 forms a plane and thus there is no problem about closing between the receiver and an ear. Above the receiver, however, no plane is formed and it is difficult to close a space between the receiver and an ear. Therefore, a reception sound reproduced by the receiver is considerably leaked from above the receiver. This condition is close to a state where measurement is performed using the Type 3.2 hi-leak acoustic coupler. Meanwhile, in the fourth-generation mobile phone which will be released a few years later, transmission characteristics of a reception sound will be improved, and a reproduction range of low-frequency-range sounds will be largely expanded to provide a higher quality of reception sound, as compared with in the existing mobile phones.
Here, a measurement result, using an acoustic coupler, of reproduction sound pressure level/frequency characteristics of a receiver is shown in
As seen from the characteristics IV shown in
As described above, by adopting the loudspeaker structure according to the present invention as a receiver of a mobile phone, a quality of a reception sound can be considerably improved. That is, the loudspeaker structure according to the present invention is suitable for a receiver of a recent mobile phone in which the receiver should be installed in an upper portion of the upper housing 90 due to enlargement of the liquid crystal screen 93, and suitable for a receiver of the fourth-generation mobile phone in which a reproduction range of low-frequency-range sounds will be largely expanded.
Next, conditions of the viscosity and the amount of the magnetic fluid which is loaded within the magnetic gap will be described. In the loudspeaker structure according to the present invention, the voice coil is held within the magnetic gap due to the viscosity of the magnetic fluid as described above, and the viscosity and the amount of the magnetic fluid affect holding power for the voice coil. Particularly in a receiver of a mobile phone, a vibration system constituted of a diaphragm and a voice coil has a light weight of several tens mg. Therefore, the viscosity of the magnetic fluid raises the lowest resonance frequency of the receiver.
With changing the amount of magnetic fluid having a viscosity of 100 mPa·s, when the amount of magnetic fluid exceeds 11 mg, f2 sees a sharp rise and exceeds 400 Hz, as seen from the characteristics V shown in
The present embodiment describes an example of the loudspeakers according to Embodiments 1 to 8 described above being installed in a video device.
In
Operations and effects of the flat-screen television configured as above will be described. An acoustic signal processed in a signal processing section (not shown) is inputted to each loudspeaker 102 to be converted into a sound.
A recent flat-screen television is more and more frame-narrowed by narrowing an outer frame, which is formed by the housing 100 enclosing an outer circumference of the display section 101, to a maximum extent in order to emphasize largeness of the display section 101. Therefore, a space for placing the loudspeaker 102 is narrow, and there is a demand for slimming the loudspeaker 102. If the conventional loudspeaker structure shown in
As described above, the loudspeaker structure according to the present invention is suitable for a loudspeaker of a flat-screen television which becomes slimmer and slimmer.
The loudspeakers according to Embodiments 1 to 8 described above are also applicable to an inner-ear headphone which is used for a portable player or the like. The inner-ear headphone has a problem that sound leak occurs to cause deficiency of low frequency sounds unless a space between a loudspeaker and a user's ear is closed by pressing the ear with a cushioning or the like. However, by applying the loudspeaker according to the present invention, sufficient low frequency sounds can be reproduced and a sufficient sound quality can be obtained even though some sound leak occurs when a user wears an inner-ear headphone. That is, it is not so necessary to press a user's ear with a cushioning or the like in order to obtain sufficient low-frequency-sound reproduction and a sufficient sound quality. Thus, an inner-ear headphone with excellent wearing comfort can be realized.
The loudspeaker according to the present invention is capable of realizing both of downsizing and widening of a reproduction range and reducing non-linear distortion by a support as well as further improving a sound quality and efficiency. The loudspeaker according to the present invention is installed in a video device such as a flat-screen television having a liquid crystal panel, a PDP, or an organic EL panel which becomes thinner and thinner, in a portable information processing apparatus such a mobile phone, and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-300129 | Nov 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/003074 | 10/28/2008 | WO | 00 | 7/15/2009 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/066415 | 5/28/2009 | WO | A |
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| International Search Report mailed Feb. 24, 2009 for International Application No. PCT/JP2008/003074. |
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| Number | Date | Country | |
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| 20110044489 A1 | Feb 2011 | US |
