GB2325373A

GB2325373A - Loudspeaker unit

Info

Publication number: GB2325373A
Application number: GB9818737A
Authority: GB
Inventors: Syoji Tanaka
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1996-02-29
Filing date: 1997-02-07
Publication date: 1998-11-18
Anticipated expiration: 2017-02-07
Also published as: JP3233004B2; GB9818737D0; CN1123277C; CN1211380A; GB2325373B; WO1997032451A1; JPH09238396A

Abstract

A loudspeaker unit which can reproduce high-level sounds while having a thin structure. The loudspeaker unit is constituted in such a way that a damper (5) is positioned inside the magnetic gap (1 d) of a field section, the free end (5a) of the damper (5) is fitted to a diaphragm (7) fitted to the top section of a voice coil bobbin (3a), and the coil (3) is held in the magnetic gap (1d) by means of the damper (5) through the diaphragm (7). The hole formed of the internal surfaces of a plate (1c) and a magnet (1a) is used as the space (1e) in which the damper (5) can move. Therefore, the thickness of the speaker unit can be reduced, because there is no need of the spacial allowance for the downward displacement of the damper (5) above the field section. In addition, the horizontal deflection of the lower end section of the coil (3) becomes smaller and the lower end section is prevented from coming into contact with the field section even when rolling occurs, because the distance from the damper (5) to the lower end section of the coil (3) becomes shorter. Therefore, the unit can reproduce high-level sounds.

Description

t D E S C R I P T 10 N LOUDSPEAKER UNIT

Technical Field:

The present invention relates to a loudspeaker unit, which can reproduce high-level sounds while having a thin structure.

Background Art:

Much effort has been made to reduce the thickness of a loudspeaker unit in order to use it in a wall-hanging application, in a space-conscious place, or in a place where an esthetic consideration is needed. Some of the examples of thickness reduction in conventional loudspeaker units are described in the following with reference to the drawings.

Among the well-known thin structures is a unit formed of an integration of a large diameter voice coil and a flat diaphragm.

There is also another means for reducing the thickness as disclosed in Fig. 1 of the Japanese Utility Model Publication, No. 56-45278.

Fig. 13 shows structure of a conventional loudspeaker unit belonging to the former category, Fig. 14 shows that of the latter category.

In the loudspeaker unit of Fig. 13, a diaphragm 127 is flat-shaped, not cone-shaped, to make the contour of entire unit thin, a voice coil 123 having large diameter is employed to obtain a good frequency characteristic out of the flat diaphragm. Because the voice coil 123 has a large diameter, a magnetic unit 121 is formed in an inner magnetic type constituted with a magnet 121a, a yoke 121b t 2 and a plate 121c.

A damper 125 is fixed at the outer circumferential edge to a frame 122, the free end 125a is fitted to the outer surface of a bobbin 123a of a voice coil. The voice coil 123 is supported in a magnetic gap 121d. A lead wire 123b of voice coil is taken from the bobbin 123a, and is connected to a terminal board 124. The diaphragm 127 is attached to the top end section of the bobbin 123a, and is supported at the circumference by an edge 126 fixed to the frame 122.

In Fig. 14, a damper 135 is fixed at the inner edge to a fixing stand 131f mounted in a magnetic unit 131, and the free end 135a in the outer edge is fitted to the inner surface of a bobbin 133a of voice coil 133. Other structures remain the same as in the loudspeaker unit of Fig. 13.

With the above-described constitution where a deep cone-shaped diaphragm is eliminated, the thickness of a unit may be reduced by the value corresponding to the diaphragm.

In the above-described constitution, however, it is difficult to reduce the thickness of a unit small enough if a sufficient space is to be secured for an amplitude of a diaphragm.

Reproduction of high-level sounds is also difficult, because it easily generates abnormal sounds when rolling occurs in the vibrating system. These are two major problems.

Now in the following, the two problems with conventional thin units are described referring to the drawings. The first problem is described in the first place with reference to Fig. 15.

Structure of the loudspeaker unit of Fig. 15 is identical to the one described in Fig. 13. Symbol H1 represents thickness of a 3 yoke 141b, H2 is distance from the bottom end of voice coil 143 to the yoke 141b, H3 is an extruding length of bottom end section of voice coil 143 from a plate 141c, H4 is thickness of plate 141c, H5 is distance from the upper surface of magnetic unit 141 to the bottom surface of damper 145, H6 is height of damper 145. Symbol H7 + a represents distance from the upper surface of damper 145 to the rear surface of diaphragm 147, where a being a spacial allowance provided for preventing the lead wire 143b of voice coil from coming into contact with damper 145 or diaphragm 147 by resonance; it is usually 2 - 3mm. Symbol H8 denotes distance from the rear surface of diaphragm 147 to the top end of frame 142.

Assuming the largest amplitude of diaphragm in one side as X, then the formulae H2 = X, H5 = X and H7 = X have to be fulfilled. The overall height HT of a loudspeaker unit is; HT = H1 + H2 + H3 + H4 + H5 + H6 + H7 + a + H8. Including the above formulae, HT = M+X+M+H4+X+H6+X+ a +H8=3X+Hl+H3+H4+H6 + a +H8. This means that at least a space identical to 3-times the largest one-side amplitude of diaphragm is needed, however small the H1, H3, H4, H6, a, H8 may be. Namely, it is difficult to make a material reduction in the unit thickness if a sufficient amplitude is to be secured with a diaphragm.

There is a same problem also in the conventional unit of Fig. 14, although a small room is available for the thickness reduction by a value equivalent to the dimension a, the value that can be eliminated.

Now the second problem is described referring to Fig. 16. Structure of the loudspeaker unit of Fig. 16 is identical to the one described in Fig. 13. The rolling center point S of a vibrating system 4 t (the whole of voice coil, diaphragm and all other vibrating members) is located at a same level as the static height of free end 155a. Symbol Ll denotes distance from a plane on which an edge 156 is supporting a diaphragm 157, or the surface of diaphragm 1,57, to the rolling center point S. Symbol L2 is distance from the bottom end of voice coil 153 to the rolling center point S.

Assuming the horizontal displacement at the surface of diaphragm 157 caused by rolling of the vibrating system as A, the horizontal deflection B of the lower end section of voice coil 153 is represented with a formula, B = A X (L2 / LI). The greater the L2 with respect to L1, the greater is the (L2 / Ll), so is B. Therefore, voice coil 153 easily comes into contact with yoke 151 or plate 151c to generate abnormal sounds.

In a conventional thin loudspeaker unit employing a flat-shaped diaphragm, the Ll is smaller as compared with that of a normal loudspeaker unit using a deep cone-shaped diaphragm; therefore, the (L2 / Ll) becomes larger than that of a normal unit. A greater deflection is caused at the lower end section of voice coil when rolling occurs; as a result, abnormal sounds are readily generated.

The same problem shared by the conventional loudspeaker unit of Fig. 14.

Disclosure of the Invention:

The present invention provides a loudspeaker unit that has enough room for a sufficient amplitude despite a thin contour. In the loudspeaker unit, the danger of abnormal sounds due to rolling is alleviated and high-level sounds are reproduced.

An invented loudspeaker unit is constituted with a v damper positioned inside the magnetic gap of a magnetic unit,.the magnetic unit having a space underneath the damper in which space the damper can move. The entire vibrating system, excluding a voice coil bobbin vertically positioned in the magnetic gap, is fitted to the free end of damper to be supported. The voice coil bobbin is not fitted to a damper supporting the vibrating system.

In the above described structure, there is no need of the spacial allowance for the downward displacement of the free end of damper above the magnetic unit. Therefore, the loudspeaker unit thickness may be reduced as compared with a conventional unit by a value equivalent to the largest one-side amplitude. As the distance between the rolling center point and the lower end section of voice coil is substantially reduced, the horizontal deflection of the lower end section of voice coil becomes small even if rolling occurs.

Therefore, generation of abnormal sounds by the voice coil coming into contact with the magnetic unit may be prevented, and the loudspeaker unit may reproduce high-level sounds.

Brief Description of the Drawing:

Fig. 1 shows structure of a loudspeaker unit in accordance with a first exemplary embodiment of the present invention. Fig. 2 is a chart used to explain a first function and effect of the loudspeaker unit. Fig. 3 is a chart used to explain a second function and effect of the loudspeaker unit. Fig. 4 shows structure of a loudspeaker unit in accordance with a second exemplary embodiment of the present invention. Fig. 5 shows structure of a loudspeaker unit in accordance with a third exemplary embodiment of the present invention. Fig. 6 shows structure of a 6 0 loudspeaker unit in accordance with a fourth exemplary embodiment of the present invention. Fig. 7 shows structure of a loudspeaker unit in accordance with a fifth exemplary embodiment of the present invention. Fig. 8 shows structure of a loudspeaker unit in accordance with a sixth exemplary embodiment of the present invention. Fig. 9 shows structure of a loudspeaker unit in accordance with a seventh exemplary embodiment of the present invention. Fig. 10 shows structure of a loudspeaker unit in accordance with an eighth exemplary embodiment of the present invention. Fig. 11 shows structure of a loudspeaker unit in accordance with a ninth exemplary embodiment of the present invention. Fig. 12 shows structure of a loudspeaker unit in accordance with a tenth exemplary embodiment of the present invention. Fig. 13 shows structure of a conventional loudspeaker unit. Fig. 14 shows structure of other conventional loudspeaker unit. Fig. 15 is a chart used to explain a first problem with a conventional loudspeaker unit. Fig. 16 is a chart used to explain a second problem with a conventional loudspeaker unit.

Best Mode for Carrying Out the Invention: (Exemplary Embodiment 1)

A first exemplary embodiment of the present invention is described in the following referring to the drawings. Fig. 1 shows structure of a loudspeaker unit in accordance with a first exemplary embodiment of the present invention. The loudspeaker unit of Fig. 1 has a diameter 12cm. A magnetic unit 1 is an inner magnetic type. A magnet la has an outer diameter 55mm, an inner diameter 26mm, a thickness 9mm, which is made of a ferrite. A yoke 1b is made of a 7 c 2mm thick iron material. A plate 1c has an outer diameter 60mm, an inner diameter 30mm, a thickness 4mm, which is made of an iron material. A magnetic gap id has an inner diameter 60mm, an outer diameter is 64mm. A space le in which a damper can move corresponds to a hole formed of the internal surfaces of the plate Ic and the magnet la.

A frame 2 is made of an iron sheet of 0.6mm. thick. A voice coil 3 has a largest outer diameter 63.4mm. A voice coil bobbin 3a of the voice coil 3 has an inner diameter 60.6mm, which is made of a 0.075mm thick aluminum. A lead wire 3b of the voice coil 3 is tinsel cord.

Symbol 4 denotes a terminal board. Symbol 5 represents a damper, whose diameter of at the fixed end is 30mm, the height of corrugation is 2nim, which is made of a cotton cloth.

Symbol 5a denotes the free end of the damper 5. An edge 6 is made of a 0. 7mm thick foamed urethane. A flat-shaped diaphragm 7 has a diameter 80mm, a thickness 2mm, which is made of a plastic material. A protrusion in the center of diaphragm 7 has an outer diameter 10mm, an inner diameter 6mm, a height 10mm.

Damper 5 is fixed at the outer circumferential edge to plate 1c, while the free end 5a is fitted to the center protrusion of diaphragm 7. Diaphragm 7 is fitted to the upper end section of bobbin 3a, while the voice coil 3 is supported within the magnetic gap ld by the damper 5 via diaphragm 7. Namely, the bobbin 3a which is vertically positioned within the magnetic gap Id is not attached to the damper. This being a point which is totally different from a conventional loudspeaker unit.

A lead wire 3b is coming from the bobbin 3a and is 8 t connected to a terminal board 4. The diaphragm 7 is supported at the circumferential edge by the edge 6 fixed to frame 2.

The function and effect of a loudspeaker unit of the present embodiment is described in the following referring to Fig. 2 5 and Fig. 3.

In the first place, a first function and effect of the loudspeaker unit, namely, the function and effect caused as a result of the thin structure, is described. Fig. 2 is a chart used to explain the first function and effect. Structure of the loudspeaker unit of Fig. 2 is identical to the one described in Fig. 1.

In Fig. 2, H1 represents a thickness of yoke 11b, H1 = 2mm. H2 represents a distance between the bottom end of voice coil 13 and the yoke 11b, H2 = 8m.m. H3 is an extruding length of the lower end section of voice coil 13 from the plate 11c, H3 = lmm. H4 is a thickness of plate 11c, H4 = 4mm.

H6 is a height of damper 15, H6 = 2mm. H7 is a distance between the upper end of damper 15 and the rear surface of diaphragm 17, H7 = 8mm. H8 is a distance between the rear surface of diaphragm 17 and the top end of frame 12, H8 = 3mm. H9 is a distance between the upper level of magnetic unit 11 and the rear surface of diaphragm 17, H9 = 1Omm.

Assuming the largest one-side amplitude of diaphragm as X,then,X=8mm, H2=X=8mm,H7=X=8mm,H7+a =X+ a = lomm. Here, arepresents a spacial allowance provided for preventing the lead wire 13b of voice coil 13 from coming into contact with the magnetic unit 11 or the diaphragm 17 by resonance, a 2mm.

The overall height of the unit HT is; HT = H1 + H2 + H3 + 9 t H4+H6+M+H8,whenH6 k a;HT=Hl+H2+H3+H4+H7+ a + H8, when H6;S a (in the present embodiment, both of the above HT take a same value because H6 = a).

Because M=X andH7 = X, HT=Hi +X+H3 +H4+H6 +X+H8=2X+Hl+H3+H4+H6+H8,whenH6 k" a;HT=M+ X+M+H4+X+ a +H8=2X+Hl+H3+H4+ a +H8,whenH6:S a. In the present embodiment, both of the above HT take 'a same value because H6 = a.

While the overall height HT of conventional unit of Fig.

15 is represented by a formula HT = 3X + H1 + H3 + H4 + H6 + a + H8, that of the invented unit may be reduced by (3X + H1 + H3 + H4 +H6+ a +H8)-(2X+H1.+HS+H4+H6+H8)=X+ a,whenH6 k'a;orwhenH6 'S a,(3X+Hl+H3+H4+H6+ a +H8)-(2X+ M+M+H4+ a +H8)=X+H6. In the present embodiment, both of the above HT take a same value because H6 = a.

There is no need of providing spacial allowance for the downward displacement of the free end of damper above the magnetic unit; therefore, the thickness of an invented loudspeaker unit may be reduced by at least a value equivalent to the largest one-side amplitude.

Comparing the overall height of an invented loudspeaker unit and that of a conventional loudspeaker unit under equal dimensional conditions with respect to magnetic unit, diaphragm thickness and other relevant elements, the overall height of the invented unit may be reduced to as small as 28mm, against a marginal smallest height 38mm with the conventional unit of Fig. 15, assuming the largest one-side amplitude to be 8mm.

The second function and effect of a loudspeaker unit of c the present embodiment, viz. elimination of abnormal sounds, is described in the following. Fig. 3 is a chart used for explaining the second function and effect. Structure of the loudspeaker unit of Fig.

3 is identical to the one described in Fig. 1.

In Fig.3, the rolling center point S of a vibrating system (the whole of voice coil, diaphragm and all other vibrating members) is located at a same level of the static height of free end 25a of damper 25. Symbol Ll denotes a distance from a plane on which an edge 26 is supporting a diaphragm 27, or the surface of diaphragm 27, to the rolling center point S; Ll = 12mm (compares to the H6 + H7 + diaphragm thickness 2mm in Fig. 2).

Symbol L2 is a distance from the lower end section of voice coil 23 to the rolling center point S; L2 = 5mm (compares to the H3 + H4 in Fig. 2).

Assuming the horizontal displacement at the surface of diaphragm 27 caused by rolling of the vibrating system as A, the horizontal deflection B at the lower end section of voice coil 23 is represented with a formula, B = A X (L2 / Ll).

As the value L2 is as small as the thickness of plate 21c, the (L2 / Ll) makes a small value. In the present embodiment; (L2 Ll) = 0.42, B = A X 0.42.

For the sake of comparison, the Ll in the conventional unit described with reference to Fig. 16 is, Ll = 14mm (compares to the H6 + H7 + a + diaphragm thickness 2mm in Fig. 15); L2 = 13mm (compares to the H3 + H4 + H5 in Fig. 15); (L2 / LI) = 0.93, B = A X 0.93.

Namely, the horizontal deflection of the lower end section of voice coil is less than half that the conventional unit. Therefore, 11 c even when a diaphragm is displaced horizontally by rolling, the horizontal deflection of the lower end section of voice coil remai ns small. So the lower end section of voice coil is prevented from coming into contact with magnetic unit to make abnormal sounds.

As described in the above, in a loudspeaker unit of the present exemplary embodiment, there is no need of providing spacial allowance for the downward displacement of the free end of damper above the magnetic unit; therefore, the thickness of an invented loudspeaker unit may be reduced by at least a value equivalent to the largest one-side amplitude. In addition, the horizontal deflection of the lower end section of the voice coil becomes smaller and the lower end section is prevented from coming into contact with the magnetic unit even when rolling occurs, because the distance from the rolling center point to the lower end section of the voice coil is substantially reduced. Therefore, the loudspeaker unit can reproduce high-level sounds.

In the present exemplary embodiment, the hole formed of the internal surfaces of a plate and a magnet is used as the space in which the damper can move. In order to meet a larger movement of the damper, the space may be enlarged by providing a hole in the bottom of yoke. Or, depending on a situation, the hole formed of the internal surface of only a plate may be appropriated for the purpose.

In the present exemplary embodiment, the free end of a damper is fitted to a diaphragm having a protrusion in the central part. As an other exemplary way of fitting, the damper may be fitted to a diaphragm indirectly by providing a cylindrical structure at the central part of the diaphragm to be connected with the free end of damper.

12 c In the present exemplary embodiment, a damper is fixed to a plate. However, a damper may also be fixed to the inner surface of the upper portion or other such place of a magnet, or may be fixed on, for example, a spacer sheet attached on a plate.

The damper used in the present embodiment is a so-called flat damper having no ridge at the outer circumference. However, a damper having a ridge may of course be used for the same purpose.

Although a voice coil bobbin is not fitted to a damper which supports the vibrating system, the voice coil bobbin may be fitted to, for example, a damper-like protection net for protecting the magnetic gap from dust (not for supporting the vibrating system).

Or, an upholding damper may be employed for provisionally holding a bobbin during assembly of a loudspeaker unit; which damper is removed after the assembly is finished.

The aforedescribed are only examples and not to be understood limitedly.

(Exemplary Embodiment 2) Fig. 4 shows structure of a loudspeaker unit in accordance with a second exemplary embodiment of the present invention. The structure is identical to that of the loudspeaker unit of first embodiment described with reference to Fig. 1, with exception of a diaphragm 37. So, description on the identical portions is not repeated here.

A diaphragm 37 of the present embodiment is cone- shaped, which is provided with a fitting section 37a for fitting it to a voice coil bobbin 33a. The central part of diaphragm 37 is fitted to the free end 35a of a damper 35. The diaphragm 37 has a diameter 80mm, an overall height llmm, which is made of a 0.8mm thick is v paper.

The basic function and effect of the above described loudspeaker unit remain the same as those of the one described in the first embodiment.

Because the diaphragm 37 of the present embodiment is cone-shaped, a paper or other readily available materials may be used for a diaphragm to the saving of material cost. The fitting section 37a contributes to make the volume production easier.

The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 3) Fig. 5 shows structure of a loudspeaker unit in accordance with a third exemplary embodiment of the present invention. A magnetic unit 41, a frame 42, a voice coil 43, an edge 46 and a terminal board 44 of the loudspeaker unit of the present embodiment are identical to the ones in the first embodiment described with reference to Fig. 1. So description on these items is not repeated here.

A damper 45 of the present embodiment has a free end 45a in the outer circumference, and the damper 45 is fixed on a platform 41f provided in the bottom center of yoke 41b. The platform 41f has a diameter 8mm, a height 9mm excluding a protrusion for fitting with yoke 41b, which is made of a plastic material.

A diaphragm 47 has a flat shape, like the case with the first embodiment, a thickness 2mm, which is made of a plastic material. The diameter of the central protrusion is larger than that of the first embodiment, having an outer diameter 24mm, an inner 14 c diameter 2lmm, a height 14mm.

The basic function and effect of a loudspeaker unit of the present exemplary embodiment are identical to those of the first embodiment.

As a damper 45 of the present embodiment has the free end 45a in the outer circumference, the diameter of free end 45a is large. Accordingly, diameter of the central part of diaphragm 47 to which the damper is attached is also large. Thus the concentration of stress to the central part is eased. This allows to make the thickness of a diaphragm thin, and provides additional freedom in designing a diaphragm.

In the present embodiment, a platform is provided on the bottom of yoke. As an alternative, the platform may be attached, for example, on the central part of a frame extended to cover the back of yoke, making a hole in the bottom of the yoke.

The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 4) Fig. 6 shows structure of a loudspeaker unit in accordance with a fourth exemplary embodiment of the present invention. Diameter of the loudspeaker unit of the present embodiment is also 12cm. A frame 52, a diaphragm 57, an edge 56 and a terminal board 5, of the unit are identical to the ones in the first embodiment. Description on these items is not repeated here.

A magnetic unit 51 is an outer magnet type. A magnet 51a has an outer diameter 90mm, an inner diameter 50mm, a thickness 9mm, which is made of a ferrite. A yoke 51b has an outer diameter 85mm, a thickness 2nim, a pole diameter 45nim, a pole t height 14mm, which is made of an iron material. A plate 51c has an outer diameter 85mm, an inner diameter 49.1mm, a thickness 4mm, which is made of an iron material. A magnetic gap 51d has an inner diameter 45mm, an outer diameter 49.1mm.

A hollow provided in the top part of pole in yoke 51b is used as a space He in which the damper 55 can move in the present embodiment. Diameter of the hollow is 38mm at the entrance, 30mm at the bottom, with a 9mm depth. A voice coil 53 has a largest outer diameter 48.4mm. A bobbin 53a of voice coil 53 has an inner diameter 45.48mm, which is made of a 0.05mm thick aluminum.

A lead wire 53b of voice coil 53 is tinsel cord. A damper 55 has a corrugation height 1.5mm, which is made of a cotton cloth. Symbol 55a represents a free end of the damper 55.

In the present embodiment, the damper 55 is fixed at the outer circumference to the top part of pole in yoke 51b. In the same configuration as in the above described embodiments, the free end 55a is fitted to the central part of diaphragm 57, and the bobbin 53a positioned vertically in the magnetic gap 51d of magnetic unit 51 is not attached with a damper; which being the point of difference from the structure of a conventional loudspeaker unit.

The basic function and effect of a loudspeaker unit of the present exemplary embodiment are the same as those of the one in the first embodiment.

As the magnetic unit of a loudspeaker unit of the present embodiment is an outer magnetic type, diameter of the magnet 51a may be enlarged to a desired size without being limited by the diameter of voice coil 53. It is easy to raise the efficiency of a loudspeaker unit.

16 1 In the present embodiment, a hollow provided in the top part of pole in yoke is appropriated as a space in which the damper can move. As an alternative, the hollow can be a through hole. Also, a damper may be fixed to a spacer sheet attached on the pole.

The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 5) Fig. 7 shows structure of a loudspeaker unit in accordance with a fifth exemplary embodiment of the present invention. Structure of a loudspeaker unit of the present embodiment remains identical to that of the one described in the first embodiment with reference to Fig. 1, with an exception of a damper 65. Description on the identical portions is not repeated here.

A damper 65 of the present embodiment is provided with a step-down portion in the outer circumference so as the free end 65a of damper 65 comes at a lower position in the vertical direction by approximately 3mm from the position of the fixed end 65b locating at the outer circumference.

As the free end 65a is positioned lower in the vertical direction than the fixed end 65b, motion of the free end 65a is restricted earlier when moving downward than when moving upward.

Therefore, the lower end section of voice coil 63 is prevented from coming into contact with the bottom of yoke 61b. Thus the loudspeaker unit is prevented from generating abnormal sounds even when an excessive input is delivered to.

17 1 The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 6) Fig. 8 shows structure of a loudspeaker unit in accordance with a sixth exemplary embodiment of the present invention. Structure of a loudspeaker unit of the present embodiment remains identical to that of the one described in the first embodiment with reference to Fig. 1, with an exception of a plate 71c. Description on the identical portions is not repeated here.

A plate 71c of the present embodiment is bent upward to the vertical direction at a magnetic gap 71d. The plate 71c has an outer diameter 60mm in the bent portion, an inner diameter 30mm, which is made of a 1.5mm thick iron sheet bent upward by approximately 2.5mm. Dimensions of the magnetic gap 71d remain the same as in the loudspeaker unit of first embodiment.

As the plate 71c of the present embodiment has a shape that is bent upward at the magnetic gap 71c, a thin material may be used for the plate 71c to the reduction of material cost and for the reduction of weight.

Because the rolling center point, or the position of free end 75a of damper 75, comes closer to the lower end section of voice coil 73, the horizontal deflection of the lower end section of voice coil 73 becomes smaller even when rolling occurs.

Although the plate 71c of the present embodiment is bent upward to the vertical direction at the magnetic gap 71d, it may of 18 1 f course be bent downward to the vertical direction with an increased thickness of the magnet.

The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 7) Fig. 9 shows structure of a loudspeaker unit in accordance with a seventh exemplary embodiment of the present invention. Structure of a loudspeaker unit of the present embodiment remains identical to that of the one described in the sixth embodiment with reference to Fig. 8, with an exception of a damper 85. Description on the identical portions is not repeated here.

A damper 85 of the present embodiment is provided with a step-up portion of 2.5mm high at the outer circumference; diameter at the fixed end of damper 85 is 48mm, being larger than the inner diameter of plate 81c. The corrugation has a height 2mm, with an overall height 4.5mm. The damper 85 is made of a cotton cloth. The basic function and effect of a loudspeaker unit of the present

exemplary embodiment are the same as those of the one in the first and the sixth embodiments.

Although the overall height of damper 85 increases by a value equal to the step-up portion of the outer circumference, the rolling center point does not go higher because the plate 81c can be made with a thin material.

Further, as the plate 81c is bent upward in the vertical direction at the magnetic gap 81d and the diameter of fixed end of damper 85 is larger than the inner diameter of plate 81c, the damper can have a longer movable span (length between the fixed end and 19 1 the free end). So the linearity of a loudspeaker unit may be improved.

Furthermore, the fatigue of damper 85 is reduced to the elimination of a trouble due to breakage of damper 85. The reliability of a loudspeaker unit may be increased.

The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 8) Fig. 10 shows structure of a loudspeaker unit in accordance with an eighth exemplary embodiment of the present invention. Structure of a loudspeaker unit of the present embodiment remains identical to that of the one described in the first embodiment with reference to Fig. 1, with exceptions of a diaphragm 97 and a coupling cone 98. Description on the identical portions is not repeated here.

A diaphragm 97 of the present embodiment is not provided with a protrusion in the central part, but it is a flat diaphragm. A coupling cone 98 is provided for coupling the upper end section of a bobbin 93a of voice coil 93, the free end 95a of damper 95 and the diaphragm 97 together. The coupling cone 98 is fitted at the central part to the free end 95a.

The diaphragm 97 has a diameter SOmm, a thickness 2mm, which is made of a plastic material. The coupling cone 98 has an outer diameter 62mm, an overall height 10.5mm, which is made of a 0.5min thick paper. Around the outer circumference of the coupling cone 98 is a connecting portion for connection with the bobbin 93a; diameter of the connecting portion is 61mm.

The basic function and effect of a loudspeaker unit of the p present exemplary embodiment are the same as those of the one in the first embodiment.

As a coupling cone 98 is provided for coupling the upper end section of bobbin 93a, the free end 95a and the diaphragm 97, 5 there is no need of fitting the diaphragm 97 to the free end 95a. Thus, strength of burden on diaphragm 97 is very much alleviated, and the freedom of designing may be substantially increased.

Further, there is no need of a precise position aligning operation because fitting of the diaphragm 97 to the coupling cone 98 can be made in other process step separated from a process of fitting the voice coil 93, damper 95 and coupling cone 98 to the magnetic unit 91. This contributes to the higher efficiency in volume production of loudspeaker units.

Although a diaphragm used in the present embodiment is flat-shaped, it may take a cone shape, a domed shape or any other shapes.

The above described is only an example and not to be understood limitedly.

(Exemplary Embodiment 9) Fig. 11 shows structure of a loudspeaker unit in accordance with a ninth exemplary embodiment of the present invention. Structure of a loudspeaker unit of the present embodiment remains identical to that of the one described in the eighth embodiment with reference to Fig.10, with exceptions of a characteristics correction piece 107a and a coupling cone 108.

Description on the identical portions is not repeated here.

A coupling cone 108 of the present embodiment is fitted to a diaphragm 107 at a place in the vicinity of primary high resonance 21 t frequency node. The primary high resonance frequency node of the diaphragm 107 alone is located on a circle of 57mm diameter.

The characteristic correction piece 107a is affixed on the rear surface of diaphragm 107, which piece functions to shift the node of primary high resonance frequency towards the inner circumference of diaphragm 107. The diameter of primary high resonance frequency node on diaphragm 107 after the characteristics correction piece 107a is 54mm.

The coupling cone 108 has an outer diameter 62mm, whose surface to be affixed to diaphragm 107 has an outer diameter 56mm, an inner diameter 52mm, average diameter of the affixed circle being 54mm. Coupling cone 108 has an overall height 10.5mm, which is made of a 0.5mm thick paper. Characteristics borrection piece 107a has a diameter 8mm, a thickness 3mm, which is made of a foamed butyl rubber. The node on diaphragm 107 without the characteristics correction piece 107a is located on a circle of 57mm diameter.

The basic function and effect of a loudspeaker unit of the present exemplary embodiment are the same as those of the one in the first and the eighth embodiments.

As the coupling cone 108 of the present embodiment is affixed to diaphragm 107 at a place in the vicinity of primary high resonance frequency node, no peak of the primary high resonance frequency arises and the reproduction frequency range may be extended up to a secondary high resonance frequency. The primary high resonance frequency of the diaphragm 107 of the present embodiment is 1. 5kHz, the secondary high resonance frequency of which is 5kHz; therefore, the reproduction frequency range may be 22 v extended up to the value.

Although the diameter of a circle of coupling cone 108 to be -affixed to diaphragm 107 is smaller than the diameter of voice coil 103 in the present emodiment, it is also possible to make the diameter of affixing circle of coupling cone larger than that of voice coil as practiced in a tenth exemplary embodiment.

In the present embodiment, a characteristics correction piece 107a is attached on diaphragm 107. However, there is no need of correction piece 107a if a location of the primary high resonance frequency node on a diaphragm and an affixing location of coupling cone to the diaphragm coincide.

The above described is only an example and not to be understood limitedly. .

(Exemplary Embodiment 10) Fig.12 shows structure of a loudspeaker unit in accordance with a tenth exemplary embodiment of the present invention. A loudspeaker unit of the present embodiment has a same diameter 12cm. A frame 112, a terminal board 114, an edge 116 and a diaphragm 117 are identical to those of the one described in the eighth embodiment with reference to Fig.10. Description on these identical portions is not repeated here.

A magnetic unit 111 is an inner magnet type. A magnet 111a has an outer diameter 40mm, an inner diameter 22mm, a thickness 7mm, which is made of a ferrite. A yoke 111b has a thickness 2mm, which is made of an iron material. Aplate111chas an outer diameter 45mm, an inner diameter 24mm, a thickness 4mm, which is made of an iron material. A magnetic gap 111d has an inner diameter 45mm and an outer diameter 49.1nim.

23 t Like the cases with above embodiments excluding Fig.6, a hole formed of the internal surfaces of the plate 111c and the magnet 111a is used as the space Me in which the damper 115 can move. A voice coil 113 has a largest outer diameter 48.4mm. A bobbin 113a of voice coil 113 has an inner diameter 45.48mm, which is made of a 0.05mm thick aluminum. A lead wire 113b of voice coil 113 is tinsel cord.

A damper 115 has a diameter 24mm for the fixed end, a corrugation height 2mm, which is made of a cotton cloth. Symbol 115a represents a free end of the damper 115.

A coupling cone 118 has an outer diameter 58mm, an overall height 10mm, which is made of a 0.5mm thick paper. On a circle of diameter 46mm, a fitting portion is provided in the coupling cone for fitting with bobbin 113a. Average diameter of the circle for fitting with diaphragm 117 is 57mm, which coincides with the location of primary high resonance frequency node of diaphragm 117.

In the present embodiment, an elastic body 119 is provided between the coupling cone 118 and the diaphragm 117. The elastic body 119 has an outer diameter 58mm, an inner diameter 56mm, which is made of a 1mm thick butyl rubber.

The elastic body 119 provided between the coupling cone 118 and the diaphragm 117 contributes to sharply attenuate the level of high range sound pressure, and presents a frequency characteristic suitable to a low range dedication.

Although in the present embodiment the coupling cone 24 f 118 is affixed to the diaphragm 117 in a location of Primary high resonance frequency node, it may be affixed in other location depending on situation.

The above described is only an example and not to be 5 understood limitedly.

Industrial Applicability:

An invented loudspeaker unit is constituted with an inner magnet type magnetic unit, a damper is positioned inside the magnetic gap of the magnetic unit, a hole formed of the internal surface of magnetic unit is used as the space in which the damper can move, the inner circumference of damper is used as the free end to be fitted to a portion of a vibrating system, the portion of fitting being the central part of a diaphragm. With the above structure, the thickness of a loudspeaker unit can be reduced because there is no need of the spacial allowance for the downward displacement of a damper above the magnetic unit.

As the distance from the rolling center point to the lower end section of voice coil is significantly reduced the horizontal deflection of the lower end section of voice coil becomes smaller even when rolling occurs, and the lower end section of voice coil is prevented from coming into contact with the magnetic unit to make abnormal sounds. This enables it to reproduce high-level sounds.

A thin loudspeaker unit eliminating a possibility of abnormal sounds due to rolling may be implemented also by constituting it with an inner magnet type magnetic unit, positioning a damper inside the magnetic gap of the magnetic unit, using a hole formed of the internal surface of magnetic unit as the space in which f the damper can move, using the outer circumference of damper as the free end to be fitted to a portion of a vibrating system, the portion of fitting being the central part of a diaphragm.

The efficiency of a loudspeaker unit may be increased easily by constituting it in such a way that it has an outer magnet type magnetic unit, a damper is positioned inside the magnetic gap, a space in which the damper can move is provided in the top portion of a yoke pole, the inner circumference of damper is used as the free end to be fitted to a portion of a vibrating system, the portion of fitting being the central part of a diaphragm. In the structure described above, the magnet may be enlarged to a desired size without being restricted by the diameter of voice coil.

By placing the free end of a damper at a position lower in the vertical direction than the position of the fixed end of a damper, motion of the free end is restricted earlier when moving downward than when moving upward. Therefore, the lower end section of voice coil is prevented from coming into contact with the bottom of yoke to generate abnormal sounds. Thus the loudspeaker unit may not reproduce abnormal sounds even when an excessive input is delivered to.

By shaping a plate of magnetic unit in such a way that it is bent upward at the magnetic gap, a thin material may be used for making the plate to the reduction of material cost and for the reduction of weight. Further, by making the diameter of fixed end of damper larger than the inner diameter of plate, the linearity characteristic and the reliability of a loudspeaker unit may be improved.

By providing a coupling cone for coupling the upper end 26 section of voice coil bobbin, the free end of a damper and a diaphragm together, with the central Portion of the coupling cone fitted to the free end of the damper, there is no need of a precise position aligning operation when fitting a diaphragm to the coupling cone. This contributes to increase the efficiency in producing loudspeaker units in volume.

Further, by fitting a coupling cone to a diaphragm at a place in the vicinity of primary high resonance frequency node, no peak of the primary high resonance frequency arises and the reproduction frequency range may be extended up to a secondary high resonance frequency.

In addition, by providing an elastic body between the coupling cone and the diaphragm, the high range sounds may be sharply attenuated.

As described in the above, the present invention provides a substantial advantage in the practical application.

27 c

Claims

1. A loudspeaker unit comprising:

damper; and magnetic unit disposing said damper inside the magnetic gap thereof and having a space underneath said damper in which space said damper can move, wherein a vibrating system other than a bobbin of a voice coil positioned vertically in said magnetic gap is fitted to and is supported by the free end of said damper, while said bobbin is kept 10 free from said damper which supports said vibrating system.

2. The loudspeaker unit of claim 1, wherein said magnetic unit is an inner magnet type, a hole formed of the internal surface of said magnetic unit is used as said space, the inner circumference of said damper is said free end, and the portion of said vibrating system 15 to be fitted to said free end is the central part of a diaphragm.

3. The loudspeaker unit of claim 1, wherein said magnetic unit is an inner magnet type, a hole formed of the internal surface of said magnetic unit is used as said space, the outer circumference of said damper is said free end, and the portion of said vibrating system 20 to be fitted to said free end is the central part of a diaphragm.

4. The loudspeaker unit of claim 1, wherein said magnetic unit is an outer magnet type, said space is provided in the top portion of a yoke pole, the inner circumference of said damper is.said free end, and the portion of said vibrating system to be fitted to said free end is 25 the central part of a diaphragm.

5. The loudspeaker unit recited in one of claims 2, 3 and 4, wherein said free end is positioned at a place lower in the vertical direction than the fixed end of said damper.

28 f

6. The loudspeaker unit recited in one of claims 2, 3 and 5, wherein a plate of said magnetic unit is bent to the vertical direction at said magnetic gap.

7. The loudspeaker unit recited in one of claims 2 through 5, further comprising a coupling cone for coupling the upper end section of said bobbin, said free end and said diaphragm together, wherein the central portion of said coupling cone is fitted to said free end.

8. The loudspeaker unit of claim 7, wherein said coupling cone is fitted to said diaphragm at a place in the vicinity of primary 10 high resonance frequency node.

9. The loudspeaker unit of either claim 7 or 8, wherein an elastic body is provided between said coupling cone and said diaphragm.