JPH0732516B2 - Speaker - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a speaker, and in particular, a small amplitude of a vibration source such as a voice coil is amplified by a mechanical amplifying means such as a lever to a diaphragm. It relates to a speaker that transmits.

2. Description of the Related Art In recent years, audio equipment has been significantly miniaturized due to the progress of semiconductor technology and the advent of high-performance small circuit components. Speaker systems are becoming smaller regardless of home needs or in-vehicle systems, but there is a problem with the acoustic characteristics in the low frequency range.

That is, the on-axis sound pressure (P _r ) and the amplitude (X) of the speaker are given by the following equations.

Where ρ _O is the air density, ω is the vibration angular frequency, a is the effective radius of the diaphragm, r is the distance between the speaker and the microphone, V is the speed of the diaphragm, X is the amplitude of the diaphragm, and A is the force coefficient. E is the signal of the input voltage, the electrical resistance of R _E is a speaker, M _S is the vibration system mass of the loudspeaker, M _a load mass of air, Q _O is quality factor of the resonance, f _O
Is the lowest resonance frequency, and f is the frequency.

Therefore, the efficiency decreases as the effective radius of the diaphragm decreases. Further, from the formula (2), the amplitude of the diaphragm is inversely proportional to the square of the frequency above f _O , and therefore becomes large in the low range. However, if the winding width of the voice coil is reduced in order to improve efficiency, the amplitude range of the voice coil is narrowed, so that a distortion component is generated in the low frequency range. As a driving method capable of large amplitude, there is a speaker using a long voice coil, but the utilization factor of the voice coil loop length is deteriorated and the efficiency cannot be improved. Therefore, in order to improve efficiency and reduce distortion, it is necessary to amplify the amplitude of a small voice coil and transmit it to the diaphragm.
Some used levers, as shown in No. 6.

Hereinafter, the above-described conventional speaker will be described with reference to the drawings.

FIG. 3 shows a cross section of a conventional speaker using an amplitude amplification mechanism. In FIG. 3, 1 is a pot yoke, 2
Is a magnet, 3 is a pole piece, and a pot yoke 1
The pole piece 3 sandwiches the magnet 2 to form an annular magnetic gap 4. Reference numeral 5 is a support table fixed to the upper surface of the pole piece 3, and has a bearing portion of a fulcrum a so that the lever 6 can rotate. Some magnetic gap 4 of the, there is a voice coil bobbin 8 by winding a voice coil 7 to reciprocate in response to the signal input, its upper end, pivotally from the fulcrum a of the lever 6 at a distance of l ₁ It is held by the lever 6 at various connecting points b. Further, at a distance from the fulcrum a to l ₂ (however, l ₂ > l ₁ ), there is also a rotatable coupling point c, and a reinforcing ring 9 is attached. 10 is the bottom part and the reinforcing ring 9
It is a substantially frustoconical diaphragm fixed to the. A damper for supporting the voice coil bobbin 8 and an edge for supporting the diaphragm 10 are not shown.

The operation of the conventional speaker configured as described above will be described below.

When a signal current flows through the voice coil 7 in the magnetic gap 4 formed by the pot yoke 1, the magnet 2 and the pole piece 3, the voice coil 7 and the voice coil bobbin 8
The connection point b of is changed by x. Therefore, the lever 6 rotates about the rotatable fulcrum a provided on the support 5. At this time, the displacement X of the connecting point c of the lever 6 is And the displacement is amplified by l ₂ / l ₁ times. Therefore, the reinforcing ring 9 having the connecting point c and the vibration plate fixed to this
10 is amplified by l ₂ / l ₁ times with respect to the displacement of the voice coil 7.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, since the lever rotates about the fulcrum a, the connecting points b and c are l ₁ (1-cos θ) and l ₂ (1- Since it moves only by cos θ), bending force is applied to the voice coil bobbin and the reinforcing ring, and the voice coil comes into contact with the pole piece or pot yoke and produces abnormal noise, which is not suitable as an amplitude amplification mechanism. It was

In view of the above-mentioned problems, the present invention provides a speaker that reproduces a low sound region efficiently and with high fidelity.

Means for Solving the Problems In order to achieve this object, the speaker of the present invention includes a first drive rod capable of bending the end of a lever rotatably supported around a fulcrum and a voice coil. A second member that is rotatably joined and can bend the other end of the lever and the diaphragm.
It has a mechanical amplification mechanism joined by the drive rod of
The ratio of the length from the fulcrum of the lever to the joint with the first drive rod and the length from the fulcrum to the joint with the second drive rod is defined as the length of the first drive rod and the second drive rod. The ratio is almost equal to the ratio.

With this configuration, the driving force of the voice coil is sequentially transmitted to the first driving rod, the lever, the second driving rod, and the vibration plate, and the displacement of the voice coil, which is the driving unit, is changed by the lever principle. Displacement is greatly expanded (amplified by the ratio of the length from the fulcrum of the lever to the joint with the first drive rod to the length from the fulcrum to the joint with the second drive rod) Bass reproduction Will be good. Further, since the voice coil and the diaphragm are joined to both ends of the lever via the drive rod, the positional displacement of the joint between the voice coil and the diaphragm due to the rotational movement of the lever as shown in the above-mentioned conventional example. It is possible to prevent gap scraping of the voice coil.

Example An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional view of a main part of a speaker according to an embodiment of the present invention.

In FIG. 1, 11 is a frame, 12 is a vibrating plate, 13 is an edge in which the inner peripheral edge is adhered to the outer peripheral edge of the vibrating plate 12 and the outer peripheral edge is fixed to the frame 11, 14 is a lever, and 15 is a lower magnetic part A voice coil inserted in a gap (not shown) in the circuit, 16 a damper having an inner peripheral end fixed to the voice coil 15 and an outer peripheral end fixed to the frame 11, 17 an upper end fixed to the frame 11 and a lever at the lower end. A supporting portion that fixes 14 and has a bendable portion 17a, 1
The upper end of 8 is fixed to one end of the lever 14, the lower end is fixed to the upper end of the voice coil 15, and the bendable parts 18a, 18b are provided.
Is a second drive rod 19 having an upper end fixed to the diaphragm 12 and a lower end fixed to the other end of the lever 14 and having bendable portions 19a and 19b. is there. In addition, support rod 1
7. The first and second drive rods 18 and 19 are integrally formed by using polyester elastomer (trade name Hytrel), which is one of rubber-like polymer elastic bodies. Are configured. The operation of the speaker configured as above will be described below.

First, when a reproduction signal is passed through the voice coil 15 inserted in the magnetic gap, a force is generated by Fleming's left-hand rule, and the voice coil 15 vibrates up and down. This vibration is the first
Is transmitted to the lever 14 from the drive rod 18 of
The lever 14 reciprocates in the directions of arrows d and d ′ around a. This is further transmitted to the diaphragm 12 via the second drive rod 19 to generate sound.

Here, the relationship between the ratio of the lengths of the lever 14 from the fulcrum and the ratio of the lengths of the first drive rod 18 and the second drive rod 19 in the above configuration will be described. For the sake of explanation, FIG. 2 shows a schematic diagram of the above configuration. In FIG. 2, 12 is a diaphragm, 14 is a lever, 15 is a voice coil, 0 is a fulcrum on which the lever 14 is fixed to the support rod 17, and l ₁ is a fulcrum from the lever 14 to the first drive rod 18. The length to the fixed portion, l ₂ is the length from the fulcrum 0 of the lever 14 to the fixed portion with the second drive rod 19, e is the length of the first drive rod 18, and f is the second drive rod. 19 is the length, Y is the displacement when the voice coil 15 moves in the direction of the arrow g, X is the displacement of the diaphragm when the voice coil 15 is Y, and δ ₁ is the lever 14 and the first drive rod 18. fixing portion P ₁ of the displacement of the, [delta] ₂ is the displacement of the fixing portion P ₂ of the lever 14 and the second driving rod 19.

When the lever 14 is rotated motion around a fulcrum 0, the principle by the lever end displacement [delta] ₁ of P ₁ of 14 magnified [delta] ₂ of the displacement to _1x lever ratio l ₂ / l of the lever at the other end P ₂ Can be given.
Here, when the voice coil 15 is displaced upward by Y, P ₁ is displaced upward by δ ₁ , and the other end P ₂ is displaced downward by δ ₂ , and the diaphragm 12
Is displaced downwards in X. When the lever 14 is displaced, the angle between the first drive rod 18 and the vibration axis of the voice coil 15 is α, and the angle between the second drive rod 19 and the vibration axis of the diaphragm is β. If the rotation angle is θ, the following equation holds.

δ ₁ = Y−e (1-cosα) ………… (3) δ ₂ = (l ₂ / l ₁ ) δ ₁ ………… (4) δ ₂ = X−f (1-cosβ) …… ……(Five) From equations (3), (4), (5), (6), and (7) Becomes Equation (8) is the displacement Y of the voice coil 15 and the vibration plate 12
The relationship between the displacement X and the displacement X is shown. When the second term on the right side is not 0, the linearity deteriorates due to the relationship between X and Y, and distortion occurs. In addition, l ₂ / l ₁ = f / e is set (the lever ratio is made equal to the ratio of the length of the first drive rod 18 and the length of the second drive rod 19), and α = β, and the right side of the equation (8) 2 becomes 0, the displacement X of the diaphragm 12 is amplified by the lever ratio (l ₂ / l ₁ ) of the displacement Y of the voice coil 15, and no distortion is generated. Therefore, in this embodiment, the lever ratio (l ₂ / l ₁ ) is made equal to the length ratio (f / e) of the first and second drive rods.

As described above, according to the present embodiment, the position of the lever end portion is deviated toward the center due to the rotational movement in the conventional speaker provided with the mechanical amplification mechanism that amplifies the displacement of the diaphragm by the lever principle using the lever. A bending force may be applied to the voice coil bobbin and the diaphragm to cause the voice coil to come into contact with the pole piece or the pot yoke and generate an abnormal sound. However, according to the present embodiment, there are two places between the lever 14 and the voice coil 15. The lever 14 and the vibration plate are joined together by the bendable first drive rod 18.
By joining between 12 by a second drive rod 19 which can be bent at two places, the lever 14 reciprocates rotationally and the arrows d, d '
Bending portions 18a, 18b of the first drive rod 18 even when the first driving rod 18 is moved in the direction
Since the bent portions 19a and 19b of the second drive rod 19 are rotatable, the displacement of the end position of the lever 14 in the horizontal direction is absorbed, and the voice coil 15 and the diaphragm 12 do not move in the horizontal direction. This has the advantage that it can be moved only in the vertical direction and that the above-mentioned abnormal noise can be prevented from occurring. Further, the lever ratio (l ₂ / l ₁ ) and the first drive rod 18 and the second drive rod 19
By making the length ratios (f / e) equal to each other, the displacement of the voice coil 15 and the displacement of the vibrating plate 12 have a linear relationship, and the distortion due to the drive system can be eliminated.

Although the vibrating plate 12 is provided in the direction opposite to the voice coil 15 in this embodiment, the vibrating plate 12 may be disposed on the voice coil 15 side and the magnetic circuit side. In this case, since the first drive rod 18 and the second drive rod 19 can be arranged on the same side, the speaker as a whole can be made thin.

Further, the shape of the diaphragm 12 is not limited to a flat plate and may be a cone shape.

Advantageous Effects of Invention According to the present invention, a lever and a voice coil are rotatably joined by a bendable first drive rod, and the other end of the lever and a diaphragm are joined by a bendable second drive rod. With the configuration, it is possible to absorb the positional displacement of the lever end portion in the horizontal direction due to the rotational reciprocating motion of the lever and vibrate the voice coil and the diaphragm only in the vertical direction. Therefore, the lateral bending force is not applied to the voice coil and the abnormal noise generated by the voice coil coming into contact with the magnetic gap can be eliminated, and the displacement of the voice coil is amplified by the lever principle and transmitted to the diaphragm. Good bass reproduction is possible. Furthermore, by making the lever ratio (l ₂ / l ₁ ) equal to the ratio (f / e) of the lengths of the first and second drive rods, the displacement of the voice coil and the displacement of the diaphragm become a linear relationship, and the driving force is transmitted. It is possible to realize a speaker having excellent acoustic characteristics without causing distortion in the system.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a speaker according to an embodiment of the present invention, FIG. 2 is a schematic view showing a configuration of the speaker according to the embodiment, and FIG. 3 is a sectional view of a conventional speaker. 14 ... Lever, 17 ... Support rod, 18 ... First drive rod, 19
…… Second drive rod, 17a, 18a, 18b, 19a, 19b …… Bendable part.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Kosaku Murata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Mitsuru 1006 Kadoma, Kadoma City, Osaka Prefecture (56) Reference Bibliography Sho 51-19826 (JP, U)

Claims (1)

[Claims] 1. A one end of a lever rotatably supported around a fulcrum and a voice coil are rotatably joined by a bendable first drive rod, and the other end of the lever and a vibration plate. Is rotatably joined by a bendable second drive rod, and the length from the fulcrum of the lever to the joint portion with the first drive rod and the joint between the fulcrum and the second drive rod are joined. A speaker having a mechanical amplification mechanism, wherein a ratio of lengths up to a portion is substantially equal to a ratio of lengths of the first drive rod and the second drive rod.