Communications: electrical – Audible indication – Diaphragm
Reexamination Certificate
1997-11-26
2001-03-27
Lieu, Julie (Department: 2736)
Communications: electrical
Audible indication
Diaphragm
C340S311200, C381S396000, C381S151000
Reexamination Certificate
active
06208237
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electro-mechanical and acoustic transducer for a portable terminal unit which can generate both vibration and sound by an alternating electric signal and a portable terminal unit in which the transducer is built. The portable terminal unit is, for instance, a portable telephone unit, a pager and a computer having a transmitter and a receiver, and the portable terminal unit performs communication with other distant unit on being carried with the user or placed in the vicinity of the user.
Conventionally, in a portable terminal unit such as a portable telephone unit, a small-size sound generator for generating bell sound and a micrometer for generating vibration to which a weight is attached tilting relative to axis of rotation are provided independently as means for informing the user of an incoming call.
In order to reduce the size and weight of the portable terminal unit, for the purpose of reducing the number of units, a prior art electro-mechanical and acoustic transducer of which generates both sound and vibration in a single unit has been devised and disclosed in Japanese Laid-open Utility Model Publication Number H5-85192.
In the prior art, when an alternating electric signal is input to a voice coil of the electro-mechanical and acoustic transducer, a force acts between the voice coil and a magnetic circuit unit. Since the electric signal which is input to the voice coil is electric signal of alternating current, the magnitude of the force varies with frequency of the alternating current. Consequently, a magnet held by a suspension is vibrated by the force acting on the magnetic circuit unit. This vibration is transmitted to a case through the suspension. As a result, the case vibrates.
The magnitude of vibration of mechanical vibration system is proportional to the sum of the masses of the magnet and the suspension of the mechanical vibration system. Since the mass of the suspension is small, the magnitude of vibration susbstantially depends on the mass of the magnet. However, since the mass of the magnet is not sufficient, the sufficient magnitude of vibration is not obtained form the mechanical vibration system even when the frequency of the electric signal which is input to the voice coil coincides with the resonance frequency of the mechanical vibration system. Therefore, when the electro-mechanical and acoustic transducer is provided in the portable telephone unit with a mass as much as 150 g, it is difficult to inform the user of the incoming call with sufficiently strong vibration.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to realize a small-size electro-mechanical and acoustic transducer which can generate both large vibration force and sound level.
To achieve the above-mentioned object, an electro-mechanical and acoustic transducer according to the present invention comprises a diaphragm, a magnetic circuit unit disposed so as to oppose to the diaphragm, a weight integrated with the magnetic circuit unit or attached to the magnetic circuit unit as a separate part, at least one suspension for holding a moving unit including the magnetic circuit unit and the weight, a holding member for holding the diaphragm and the suspension, and a driving unit for generating a force to drive the diaphragm and the magnetic circuit unit. The magnetic circuit unit includes a magnet, a plate and a yoke, and the driving unit is an electrodynamic unit which generates a driving force by means of a voice coil inserted in a magnetic gap of the magnetic circuit unit and fixed to the diaphragm at its one end. According to another aspect of the present invention, the magnetic circuit unit includes a magnet and a plate having a center pole, and the driving unit is an electromagnetic unit which generates a magnetic force between an exciting coil disposed on the periphery of the center pole and the diaphragm of a magnetic substance disposed with a gap with the magnetic circuit unit. For example, in the case of the electrodynamic unit, the weight is disposed on the periphery of the yoke. In the case of the electromagnetic unit, the weight is disposed on the periphery of the plate.
By the above-mentioned configuration, an electro-mechanical and acoustic transducer which can generate large vibration is realized. In the electro-mechanical and acoustic transducer, the mechanical vibration system is formed with the moving unit and the suspension, and the magnitude of vibration power of the mechanical vibration system is proportional to the product of the mass and the acceleration of the mechanical vibration system. In the electro-mechanical and acoustic transducer, since the weight is attached to the magnetic circuit unit integrally with or as separate part, the mass of the mechanical vibration system increases. Consequently, the electro-mechanical and acoustic transducer can generate large vibration. Since the electrodynamic unit and the electromagnetic unit, respectively, vibrate the diaphragm with vibrating the moving unit including the magnetic circuit unit and the weight, the electro-mechanical and acoustic transducer can generate sound.
In order to increase the mass of the mechanical vibration system, it is preferable that the weight attached to the magnetic circuit unit as a separate part made of a material having a specific gravity higher than at least iron.
In order to increase the mass of the mechanical vibration system and to prevent the magnetic flux generated by the magnet from being magnetically saturated, in the case of the electrodynamic unit, it is preferable that the yoke integrated with the weight has a magnetic flux passing portion formed so that the magnetic flux generated by the magnet is not magnetically saturated and the magnetic path is substantially formed and a weight portion for increasing the mass of the magnetic circuit unit. In the case of the electromagnetic unit, it is preferable that the plate has a magnetic flux passing portion formed so that the magnetic flux generated by the magnet is not magnetically saturated and the magnetic path is substantially formed and a weight portion for increasing the mass of the magnetic circuit unit.
The magnetic circuit unit in the case of being engaged and integrated with the weight, or the weight in the case of being engaged and attached with the magnetic circuit unit as a separate part may be rectangular. In this case, the mass of the mechanical vibration system can be increased without the dimensions of the electro-mechanical and acoustic transducer being increased.
In the case of the electrodynamic unit, in order to prevent the voice coil and the magnetic circuit unit from coming into contact with each other hence breaking the voice coil, it is preferable that the width of the magnetic gap of the magnetic circuit unit be larger than the maximum amplitude of the voice coil or the moving unit.
In order that the moving unit vibrates stably, it is preferable to hold the moving unit by disposing the suspensions at two positions on the diaphragm side of the moving unit and on the distal side of the moving unit to the diaphragm.
An electro-mechanical and acoustic transducer in accordance with the present invention comprises a diaphragm, a magnetic circuit unit disposed so as to be opposed to the diaphragm and including a yoke integrated with a weight, a magnet and a plate, a first suspension having a pair of fixing portions and fixed to a diaphragm side of the magnetic circuit unit, a second suspension having a pair of fixing portions and fixed to a distal side of the magnetic circuit unit to the diaphragm so as to be disposed in different positions from the fixing portions of the first suspension, a holding member connected to the diaphragm, having two openings and having four receiving portions connected to the fixing portions of the first and second suspension, a voice coil inserted in a magnetic gap of the magnetic circuit unit and fixed to the diaphragm, and a baffle disposed at one of the openings of the holding member.
By the above-me
Kuze Mitsukazu
Saiki Shuji
Usuki Sawako
Lieu Julie
Matsushita Electric - Industrial Co., Ltd.
Sheridan & Ross P.C.
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