JPS5931110Y2 - electrodynamic speaker - Google Patents

Description

[Detailed description of the invention] This invention relates to an electrodynamic speaker with low magnetic leakage, high efficiency,
The present invention provides an electrodynamic speaker with low distortion.

FIG. 1 shows a conventional electrodynamic speaker.

In FIG. 1, 1 is a yoke with which a center pole 2 is integrally formed, 3 is an annular magnet fixed to the upper surface of the yoke 2, and 4 is an annular plate fixed to the upper surface of the magnet 3. An annular magnetic gap is formed between the inner circumferential surface of the center pole 4 and the outer circumferential surface of the center pole 2, thereby forming an outer magnet type magnetic circuit.

5 is a frame fixed to the upper surface of the plate 4, 6 is a diaphragm, and the outer periphery of this diaphragm 6 is an annular edge member 7.
It is supported by the frame 5 via.

A coil bobbin 8 is connected to the diaphragm 6, and the coil bobbin 8 is supported by a damper 9.

Reference numeral 10 denotes a voice coil wound around the coil bobbin 8, and this voice coil 10 is arranged in the magnetic gap.

11 is a dust cap attached to the diaphragm 6.

In FIG. 1, a broken line a indicates leakage magnetic flux from the magnetic circuit.

In the conventional speaker shown in Fig. 1, there is a large amount of leakage magnetic flux, and the utilization rate of the magnet 3 is poor, reducing the efficiency of the speaker. The disadvantage is that the leakage magnetic flux from the radiator affects the surrounding circuits.

FIG. 2 shows another conventional electrodynamic speaker.

In this conventional example, a magnetic circuit is housed within a frame 5' and is magnetically shielded by the frame 5' to prevent leakage magnetic flux from affecting other circuits.

However, in the conventional speaker shown in FIG. 2, although the leakage magnetic flux to the outside of the frame 5' is reduced, the frame 5'
As a result, the magnetic flux leakage within the magnetic gap 10 is increased compared to the conventional speaker shown in FIG. 1, and as a result, the magnetic flux density within the magnetic gap for driving the voice coil 10 is reduced, which further reduces the efficiency of the speaker.

The magnetic flux density of the magnetic gap of the speaker shown in Figure 1 is 78
00 Gauss, whereas the magnetic flux density of the magnetic gap due to the Spippy force shown in Figure 2 is 6800 Gauss, and due to the influence of the magnetic shielding by the frame 5', the magnetic flux density of the magnetic gap is reduced by 1000 Gauss. .

Table 1 shows the leakage magnetic flux density at points A-F of the conventional speaker shown in FIG.

Table 2 shows the leakage magnetic flux density at point MR of the conventional speaker shown in FIG.

FIG. 3 shows the magnetic circuit of the conventional speaker shown in FIGS. 1 and 2. In the conventional magnetic circuit, the state of magnetic leakage above and below the magnetic gap is indicated by broken lines, c
Different as shown in .

FIG. 4 shows the magnetic flux density in the magnetic gap of the magnetic circuit of the conventional speaker shown in FIG.

As is clear from Fig. 4, the magnetic flux density (■) in the magnetic gap of the conventional magnetic circuit is asymmetrical in the upper and lower sides (top side and bottom side of the plate 4), and as a result, the voice coil 1
The driving force acting on zero becomes non-linear, and the sound pressure distortion of the speaker increases.

The present invention eliminates the above-mentioned drawbacks of the conventional technology, and one embodiment of the present invention will be described below.

FIG. 5 shows an electrodynamic speaker according to an embodiment of the present invention, and FIG. 6 shows only its magnetic circuit.

In FIGS. 5 and 6, reference numeral 12 designates a yoke in which an outer peripheral wall 13 is formed on the outer periphery and a center pole 14 that is higher than the height of the outer peripheral wall 13 is integrally formed. A magnet 15 is fixed.

16 is an annular plate fixed to the upper surface of the magnet 15, and the upper surface of this plate 16 and the yoke 1
It is located on the same plane as the upper surface of the outer peripheral wall 13 of No. 2.

17 is an annular plate having the same shape as the plate 16, and this plate 17 is fixed to the upper surface of the plate 16.

18 is an annular magnet fixed to the upper surface of the plate 17; 19 is an annular yoke integrally formed with an outer peripheral wall 20; this yoke 19 is fixed to the upper surface of the magnet 18; An end surface of the wall 20 is joined to an end surface of the outer peripheral wall 13 of the yoke 12.

As shown in FIG. 6, the magnets 15 and 18 are arranged so that the magnetization directions are opposite and the same poles (S poles in FIG. 6) face each other.

Further, a magnetic gap is formed between the inner circumferential surface of the annular play 1-16, 17 and the outer circumferential surface of the center pole 14.

Note that the upper surface of the center pole 12 is located between the plate 17 and the yoke 19.

The flow of magnetic flux in the magnetic circuit of the speaker in this example is as follows:
This is shown by the broken line f in FIG.

The yoke 12.19 surrounding the magnet 15.18 has the same polarity (
In FIG. 6, the magnetic leakage becomes extremely small.

Table 3 shows the leakage magnetic flux density at points G to L of the magnetic circuit shown in FIG.

As is clear from Table 3, according to the speaker of the present invention, the leakage magnetic flux density is approximately 1/10 that of the conventional example shown in FIG.
Moreover, it can be reduced to about 1/2 of the conventional example shown in FIG.

FIG. 7 shows the magnetic flux density in the magnetic gap of the speaker of the present invention, and the magnetic flux density (■) of the present invention is increased compared to the magnetic flux density I of the conventional speaker.

In other words, in the conventional example, the magnetic flux density of the magnetic gap is 7800
Gauss, but in the present invention it is 8200 Gauss.

Further, as is clear from FIG. 7, according to the present invention, the flat portion of the magnetic flux density distribution in the magnetic gap becomes wider.

The reason for the improvement in the magnetic flux density in the magnetic gap and the expansion of the flat portion of the magnetic flux density distribution according to the present invention can be explained as follows.

The magnetic circuit of the speaker of the present invention is equivalent to two identical magnetic circuits X and Y joined together, as shown in FIG.

If both magnetic circuits When Z is made small, the leakage magnetic fluxes of the same magnetic circuits X and Y repel each other iy
As shown in j, the magnetic gap 21 of each magnetic circuit X, Y
It is suppressed in the ゜22 direction.

For this reason, the magnetic flux density of the magnetic gap increases and the flat portion of the magnetic flux density distribution is expanded.

In addition, in the present invention, as shown in FIG. 7, the magnetic leakage is the same above and below the magnetic gap, so the magnetic flux density distribution is symmetrical.

Therefore, according to the speaker of the present invention, the efficiency of the speaker is improved, and sound pressure distortion due to the asymmetry of the magnetic flux density distribution can be reduced.

FIG. 10 shows a second embodiment of the invention.

In FIG. 10, reference numeral 23 denotes a ring-shaped support base fixed on the yoke 19, and the outer peripheral portion of the dome-shaped diaphragm 24 is fixed to this support base 23.

FIG. 11 shows a third embodiment of the invention.

In FIG. 11, 25 is a flat diaphragm.

FIG. 12 shows the sound pressure frequency characteristics of the conventional speaker shown in FIG. 2 and the speaker of the present invention shown in FIG.

Note that the volumes of the two magnets 15 and 18 of the speaker in the present invention used for measurement are the same as the volume of one magnet 3 in the conventional example.

As is clear from FIG. 12, even if the same volume of magnet is used, the efficiency of the speaker (2) of the present invention is improved by about 2.5 dB compared to the conventional example (2).

■ and ■ in FIG. 12 indicate the second harmonic distortion of the present invention and the conventional example, respectively. According to the present invention V, the magnetic flux density distribution is symmetrical, so compared to the conventional example ■,
Distortion at 150 Hz can be reduced by 2 to 8 dB.

In each of the above embodiments, two plates 1-16 and 17 are used, but one plate having the thickness of two plates may also be used.

The electrodynamic speaker of the present invention has the above configuration, and according to the present invention, the following effects can be obtained.

(1) Magnetic leakage is reduced, and other circuits are not affected by leakage magnetic flux even when used in television receivers and radio receivers.

(2) The magnetic flux density in the magnetic gap is improved, improving efficiency.

(3) The magnetic flux density distribution in the magnetic gap becomes symmetrical above and below the magnetic gap, and the flat portion expands, reducing distortion.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional electrodynamic speaker, Figure 2 is a sectional view of another conventional electrodynamic speaker, Figure 3 is a sectional view of the magnetic circuit of a conventional electrodynamic speaker, and Figure 4 is a sectional view of a conventional electrodynamic speaker. is a diagram showing the magnetic flux density distribution of the magnetic gap in the magnetic circuit of a conventional electrodynamic speaker, FIG. 5 is a cross-sectional view of an electrodynamic speaker according to an embodiment of the present invention, and FIG. 6 is a diagram showing the magnetic circuit of the same speaker 7 is a diagram showing the magnetic flux density distribution of the magnetic gap of the same magnetic circuit, and FIGS. 8 and 9 are equivalent diagrams for explaining the flow of magnetic flux in the magnetic circuit of the electrodynamic speaker of the present invention. 10 and 11 are cross-sectional views of other embodiments of the present invention, respectively, and FIG. 12 is a sound pressure frequency characteristic diagram of the electrodynamic speaker of the present invention and the conventional electrodynamic speaker. 5...Frame, 6...Diaphragm, 7.
...Edge member, 8...Coil bobbin,
9... Damper, 10... Voice coil, 11... Dust cap, 12...
・Yoke, 13...Outer peripheral wall, 14...
Center pole, 15... Magnet, 16,
17...Plate, 18...Magnet, 19...Yoke, 20...Outer peripheral wall, 21.22...Magnetic gap, 23・・・・・・
...Support stand, 24...Dome-shaped diaphragm, 25.
...Flat plate diaphragm.

Claims (1)

[Scope of utility model registration request] The first yoke has an outer circumferential wall formed on its outer circumferential portion and a center pole formed at its inner center, and the second yoke has an outer circumferential wall formed on its outer circumferential portion and a hole formed in the center. The end faces of the outer peripheral wall are joined, and first and second annular magnets having opposite magnetization directions with respect to the center pole are placed between the first and second yokes, and the eleventh and second annular magnets are connected to each other. An annular plate held between magnets is arranged to form a magnetic gap between the center pole and the plate, a coil bobbin fixed to the diaphragm is inserted into the hole of the second yoke, and the coil bobbin is wound around the coil bobbin. An electrodynamic speaker in which a rotated voice coil is placed in the magnetic gap.