JPH0736638B2 - 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 axial sound pressure P _r and the amplitude X of the speaker are given by the following equations.

Where ρ ₀ is the density of air, 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 ₀ is the sharpness of the resonance, f ₀
Is the lowest resonance frequency, and f is the frequency.

Therefore, the efficiency decreases as the effective radius of the diaphragm decreases. Further, according to the equation (2), the amplitude of the diaphragm is inversely proportional to the square of the frequency above f ₀ , and therefore becomes large in the low sound range.
However, if the voice coil winding width 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.
As shown in Japanese Patent Laid-Open Publication, there is one using a lever.

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

FIG. 2 shows a cross section of a conventional speaker using an amplitude amplification mechanism. In FIG. 2, 1 is a pot yoke, 2
Is a magnet, 3 is a pole piece, and a pot yoke 1
The pole piece 3 holds the magnet 2 and forms 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. In the magnetic gap 4, there is a voice coil bobbin 8 around which a voice coil 7 that reciprocates in response to a signal input is wound. The upper end of the voice coil bobbin 8 is a fulcrum a of the lever 6.
Is held on the lever 6 at a connection point b which is pivotable at a distance from 1 to ₁₁ . 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. Reference numeral 10 denotes a substantially frustoconical diaphragm fixed to the reinforcing ring 9 at the bottom. 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 an abnormal sound. Further, since the fulcrum a and the connecting points b and c are structured such that they can be rotated by fitting the hole and the shaft or the bearing and the shaft, there is always a gap in the connecting portion. Therefore, when the speaker is operated,
When the vibration of the voice coil is transmitted by the lever, there is a problem that an abnormal sound is generated due to the rattling of the clearance, and it is not suitable as a vibration amplification mechanism.

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

Means for Solving the Problems In order to achieve this object, a speaker of the present invention is supported by a support rod made of polyester elastomer, and the end of a lever rotatable around a fulcrum and a voice coil are made of polyester elastomer. Is rotatably joined by a first drive rod made of, and the other end and the diaphragm are rotatably joined by a second drive rod made of polyester elastomer, and each joint has a structure with no clearance. It is composed of a mechanical amplification mechanism.

Action With this configuration, the driving force of the voice coil is sequentially transmitted from the first drive rod to the lever, the second drive rod, and the diaphragm, and the displacement of the diaphragm is expanded compared to the displacement of the voice coil by the lever principle. Therefore, good reproduction of low sound (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) Is. 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 and the lever due to the rotational movement of the lever as shown in the conventional example is caused. It is possible to prevent gap scraping of the voice coil. Further, the support rod joined to the fulcrum of the lever, the first drive rod and the second drive rod are made of polyester elastomer which is a thermoplastic having rubber elasticity. Since the first and second drive rods are bent so that the lever can be rotated, abnormal noise due to looseness in the joint clearance is not generated unlike the conventional example, and polyester is also used. Since the elastomer has an appropriate internal loss, unnecessary vibration can be absorbed, and high fidelity reproduction becomes possible.

Embodiment One embodiment 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 where the inner peripheral edge is adhered to the outer peripheral edge of the diaphragm 12 and the outer peripheral edge is fixed to the frame 11, 14 is a lever, and 15 is the lower end of the magnetic circuit. A voice coil inserted in a gap (not shown), 16 is a damper whose inner peripheral end is fixed to the voice coil 15 and outer peripheral end is fixed to the frame 11, 17 is an upper end fixed to the frame 11, and a lever 14 is fixed to the lower end. A support rod made of polyester elastomer having a bendable portion 17a fixed thereto, 18 has an upper end fixed to the lever 14, a lower end fixed to an upper end of the voice coil 15, and a bendable portion 18a, 18b. The first drive rod 19 made of polyester elastomer is a second drive rod 19 made of polyester elastomer having upper end portions fixed to the diaphragm 12 and lower end portions fixed to the lever 14 and having bendable portions 19a and 19b. is there. 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 driving force is generated by Fleming's left-hand rule, and the voice coil 15 vibrates vertically. This vibration
The lever 14 reciprocates from the first drive rod 18 in the directions of arrows d and d '. This is further via the second drive rod 19 to the diaphragm 12
Sound is transmitted to.

As described above, according to the present embodiment, the support rod 17, the first drive rod 18, and the second drive rod 19 fixed to the lever 14 are each made of a polyester elastomer having rubber elasticity. In addition, since the reciprocating motion of the lever 14 is performed by bending the bent portions 17a, 18a, 18b, 19a, 19b, as in the conventional example, the fulcrum a of the lever and the driving points b, c are formed by the bearing and the shaft. It has an advantage that abnormal noise due to rattling of the bearing portion does not occur unlike a speaker having a portion. The polyester elastomer used here is a polyester / polyether block copolymer of a rigid hard segment of polytetramethylene terephthalate and a soft segment of poly (tetramethylene oxide) glycol having rubber elasticity. Therefore, physical properties such as elastic modulus and internal loss can be freely controlled by changing the ratio of the hard segment and the soft segment in the copolymer. The polyester elastomer in this example has an elastic modulus of 6.
8 × 10 ⁸ dyn / cm ^{2 The} internal loss is 0.12, which is much larger than the internal loss of 0.01 in general engineering plastics such as polyethylene terephthalate, and when used as the support rod 17 or drive rods 18 and 19, the lever and driving force are increased. It has a function of absorbing unnecessary vibration generated in the transmission system, and enables high fidelity reproduction. Furthermore, in a conventional speaker equipped with a mechanical amplification mechanism, the position of the lever end shifts toward the center due to rotational movement, so bending force is applied to the voice coil bobbin and diaphragm, causing the voice coil to contact the pole piece or pot yoke and produce abnormal noise. Although it may occur, according to the present invention, the lever 14 and the voice coil 15 are joined by the bendable first drive rod 18 at two places, and the lever 14 and the diaphragm 12 are joined at two places. By connecting with the second drive rod 19 which can be bent at
Even when moving in the direction, since the bent portions 18a, 18b, 19a, 19b are rotatable, the lateral displacement of the end portion of the lever 14 is absorbed and the voice coil 15 and the diaphragm 12 are not moved laterally. Instead, it is possible to move only in the vertical direction and prevent the occurrence of the above-mentioned abnormal sound.

The polyester elastomer in this example has physical properties of an elastic modulus of 6.8 × 10 ⁸ dyn / cm ² and an internal loss of 0.12, but the ratio of the hard segment and the soft segment is changed according to the purpose to make it soft or hard. It is possible to control the acoustic characteristics. Further, in the embodiment, the diaphragm 12 is the voice coil 15
However, the diaphragm 12 may be disposed on the voice coil 15 side. In this case, the first drive rod 18 and the second drive rod 19 can be arranged on the same side, and the speaker can be thinned. Further, the shape of the diaphragm 12 is not limited to a flat plate and may be a cone shape.

According to the present invention, the lever and the voice coil are composed of the first drive rod made of polyester elastomer, the lever and the diaphragm are made of the second drive rod made of polyester elastomer, and the fulcrum of the lever is made of the polyester elastomer.
Unlike the conventional example, when the lever reciprocates, there is no rattling of the bearing part and no abnormal noise is generated when the lever reciprocates so that there is no gap. It is possible to reproduce the bass sound in good condition. Further, since the driving force is transmitted through the polyester elastomer having rubber elasticity, it is possible to absorb unnecessary vibration generated by the resonance of the lever and the like, and it is possible to realize a speaker having excellent acoustic characteristics.

[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, and FIG. 2 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.

Front page continuation (72) Inventor Kosaku Murata 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. References Japanese Patent Laid-Open No. 58-133097 (JP, A) Actually published 51-19826 (JP, U)

Claims (1)

[Claims] 1. An end portion of a lever having a support rod made of polyester elastomer, a first drive rod and a second drive rod, supported by the support rod without a gap, and rotatable about a fulcrum. And the voice coil are rotatably joined by the first drive rod so that there is no gap, and the other end of the lever and the vibration plate are rotatably joined by the second drive rod so that there is no gap. A speaker that is joined to form a mechanical amplification mechanism.