JPH07327296A - Electromagnetic acoustic transducer - Google Patents

Abstract

PURPOSE:To provide on electromagnetic acoustic transducer which is easily mass-produced and reduced in size and thickness. CONSTITUTION:The electromagnetic acoustic transducer is equipped with a housing main body 2 which is cylindrical, a vibrator 4 which is supported by the housing body 2 and vibrates, a lid plate 8 which is formed of a thin plate as a member different from the housing body 2 and closes the opening part of the housing body 2 to form a resonance space on the front surface side of a resonance plate 10, and a magnetic driving part 6 which is installed on the back side of the vibrator 4 and vibrates the resonance plate 10. The lid plate is formed of a magnetic material and used as a restraining means for the movement range of the vibrator 4. The lid plate 8 has a sound radiation hole 42 formed deviating from a magnetic piece 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic sound converter for converting an input electric signal into sound by electromagnetic conversion.

[0002]

11 to 14 show the internal structure of a conventional electromagnetic acoustic transducer. These electromagnetic acoustic transducers include a housing 102, a vibrating body 104, a magnetic drive unit 106, and the like. The vibrating body 104 includes a resonance plate 108.
And the magnetic piece 110, and the magnetic piece 110 is the resonance plate 10
8 is a means for enhancing the substantial oscillating mass and constitutes a magnetic path with the magnetic drive unit 106. The magnetic drive unit 106 is
Pole piece 112, coil 114 and magnet 11
6 is provided. Then, on the upper surface side of the vibrating body 104,
A resonance chamber 118 surrounded by the housing 102 is formed, and a sound emission hole 120 is formed in the housing 102 as a means for emitting the resonance sound generated in the resonance chamber 118 to the outside.

A substrate 122 is attached to the rear side of the housing 102, and a pair of terminals 124 and 126 is attached to the rear side of the substrate 122. When an AC signal is applied between these terminals 124 and 126,
An alternating magnetic field corresponding to the level of the AC signal is generated in the magnetic drive unit 106, and the vibrating body 104 vibrates due to the magnetic field action of the alternating magnetic field. Is emitted to the outside from the sound output hole 120. Such an operation is basic as an electromagnetic acoustic transducer.

[0004]

By the way, looking at the form of the housing 102 used in these electromagnetic acoustic transducers, in the electromagnetic acoustic transducer shown in FIG. 11, the housing 102 is integrally molded with synthetic resin. The housing 102 forms a resonance chamber 118 that forms a relatively large space on the front side of the vibrating body 104. Further, in the electromagnetic acoustic transducers shown in FIGS. 12 and 13, the housing 102 is composed of two housing pieces, that is, an upper housing 102A and a lower housing 102B made of synthetic resin as separate bodies. And in FIG.
In the electromagnetic acoustic converter shown in (1), the space of the resonance chamber 118 is set to be narrow because of its flatness. The housing 102 of the electromagnetic acoustic transducer shown in FIG. 14 is formed by molding a metal plate. As described above, the housing 102 of the conventional electromagnetic acoustic transducer has various forms such as one made of synthetic resin or metal as a constituent material, one having a single structure or a plurality of constituents, and a wide or narrow resonance chamber 118. There is one.

By the way, such an electromagnetic acoustic transducer is
It is widely used as a means for generating ringing tones in mobile communications such as mobile phones, but in general, mass production, downsizing, high performance, low price, etc. are required. Conventionally, a housing 102 formed by molding a synthetic resin has been widely used.

However, since the housing 102 (FIG. 11) integrally molded of synthetic resin has a container structure,
To reduce the wall thickness to, for example, 0.5 mm or less,
It is technically difficult, and the molding accuracy is impaired, which hinders downsizing or flattening of the electromagnetic acoustic transducer as a product.

Further, as shown in FIG.
If the electromagnetic acoustic transducer is made thinner by narrowing the width of the electromagnetic resonance transducer, the resonance operation of the resonance chamber 118 is suppressed to that extent, which causes a problem that the operating characteristics of the electromagnetic acoustic transducer deteriorate.

In the electromagnetic acoustic transducer shown in FIG. 14, the drawing process of the metal plate is inferior to the forming process of the synthetic resin, it is not suitable for mass production, and it is difficult to reduce the cost.

Therefore, it is a first object of the present invention to provide an electromagnetic acoustic transducer which can be easily mass-produced and which has been made compact and thin.

A second object of the present invention is to provide an electromagnetic acoustic transducer which has improved acoustic efficiency and stabilized frequency characteristics.

A third object of the present invention is to provide an electro-acoustic transducer having an enhanced function of protecting the vibrating body.

[0012]

In order to achieve the first object, the electromagnetic acoustic transducer of the present invention includes a housing body (2) having a cylindrical body, as illustrated in FIGS. 1 and 2. A vibrating body (4) supported by the housing body and vibrating;
It is formed of a thin plate composed of a member separate from the housing body,
Resonance plate (10) closing the opening of the housing body
A lid plate (8) forming a resonance space on the front side of the above, and a magnetic drive unit (6) installed on the back side of the vibrating body to vibrate the resonance plate.

Further, in the electromagnetic acoustic transducer of the present invention, in order to achieve the second object, the cover plate is made of a magnetic material.

Further, in the electromagnetic acoustic transducer of the present invention, in order to achieve the third object, the cover plate is used as a means for regulating the moving range of the vibrating body.

In the electromagnetic acoustic transducer of the present invention, the position of the sound emission hole (42) formed in the cover plate (8) is arbitrary, but the cover plate has the magnetic piece (12) of the vibrating body. The sound output hole may be formed at a more displaced position.

[0016]

In the electromagnetic acoustic transducer of the present invention, the housing body is a tubular body, and the opening of the housing body of the tubular body is closed by a lid plate which is a member different from the housing body. Is. The lid plate is made of various materials such as a synthetic resin plate and a metal plate. With respect to the molding accuracy of the synthetic resin, a coin-shaped thin plate can achieve a molding accuracy of 0.5 mm or less as compared with the conventional container-shaped housing molding. In this way, when the housing body is set as the strength maintaining means and the closing means for the opening is the lid plate,
The lid plate can be made thin, and the electromagnetic acoustic transducer can be made thin, compact, and lightweight. Further, by making the lid plate thin, a resonance chamber having a necessary volume can be formed between the vibrating body and the lid plate, and the resonance effect can be enhanced.

Further, in the electromagnetic acoustic transducer of the present invention, the cover plate is made of a magnetic material such as permalloy. When the lid plate is formed of such a magnetic material, the lid plate is included in the closed magnetic circuit of the vibrating body. That is, since the lid plate is installed on the outer surface side of the vibrating body, the vibrating body is sandwiched between the magnetic drive unit and the lid plate, and magnetic leakage from the vibrating body can be reduced.

Further, in the electromagnetic acoustic transducer, it is known that the gap between the vibrating body and the iron core portion of the magnetic drive portion has a great influence on the frequency characteristic, and the influence is sharp. Due to the surrounding effect, the influence of the gap is reduced, and the frequency characteristic can be stabilized.

Further, when the vibration input is dropped or excessively input, the vibrating body may be mechanically displaced by receiving a mechanical shock such as being bounced up in addition to the vibration in the steady state. In the present invention, the mounting position of the cover plate with respect to the housing body is set within the movement allowable range of the vibrating body to prevent the vibrating body from moving more than necessary, thereby protecting the vibrating body from damage.

Also in such an electromagnetic sound transducer, the resonance sound can be emitted to the outside by forming a sound emission hole at an arbitrary position of the thin cover plate. In particular, if a sound emission hole is formed at a position displaced from the center position of the vibrating body, the distance between the vibration center of the vibrating body and the sound emission hole becomes longer, and the resonance space of the resonance chamber can be used effectively accordingly. , The resonance effect is obtained.

[0021]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

1 and 2 show an embodiment of the electromagnetic acoustic transducer of the present invention, FIG. 1 is a plan view thereof, and FIG. 2 is II of FIG.
-II sectional drawing is shown.

In this electromagnetic acoustic transducer, a housing body 2 having a cylindrical body is used as an exterior means. As the form of the housing main body 2, various tubular bodies such as a rectangular tubular body can be considered, but a cylindrical body is suitable as a form corresponding to the vibration mode of the vibrating body 4. Further, in the case of this embodiment, the housing body 2 is integrally molded of synthetic resin. The housing body 2 has a vibrating body 4 supported in the middle thereof, a magnetic drive unit 6 installed on the back side thereof, and a front opening side formed of a magnetic material plate or a synthetic resin plate. It is closed by a lid plate 8 made of a thin plate. One of the features is the thinning of the substrate 8.

In the vibrating body 4, a small-diameter magnetic piece 12 is attached to the center of a resonance plate 10 made of a magnetic material. The magnetic piece 12 is means for increasing the oscillating mass of the resonance plate 10, and forms a closed magnetic circuit with the resonance plate 10 and the magnetic drive unit 6.

The magnetic drive section 6 is an electric-magnetic field converting means, and causes an alternating magnetic field according to an input signal to act on the vibrating body 4. The magnetic drive unit 6 is provided with a pole piece unit 14. The pole piece portion 14 has a cylindrical magnetic core 1 on a disk-shaped base 16 made of a magnetic material.
8 is erected. In this embodiment, the magnetic core 18
Has a small-diameter portion 20 on the base end side thereof, the small-diameter portion 20 is inserted into the base 16 and the substrate 22, and the end portion thereof is caulked to be fixed to the base 16. In this embodiment, the base 1
The magnetic core 18 is used as a fixing means for the 6 and the substrate 22. A coil 24 is wound around the magnetic core 18, and ends of the coil are connected to terminals 26 and 28 provided upright on the substrate 22. An annular magnet 30 is installed on the outer periphery of the coil 24. The magnet 30 forms a closed magnetic circuit with the base 16, the vibrating body 4, and the magnetic core 18, and applies a constant magnetic field to the vibrating body 4, which is a bias magnetic field.

The tip of the magnetic core 18 is provided with a coil 24.
Although it is slightly exposed from the end face of, the gap 32 is provided between this tip face and the vibrating body 4. The gap 32 forms a vibration allowance space for the vibrating body 4, and during vibration,
The vibrating body 4 is prevented from colliding with the end surface of the magnetic core 18. In the electromagnetic acoustic transducer of this embodiment, the vibrating body 4
Is supported by the housing main body 2, and a first support step portion 34 is formed as a support means thereof. The support step portion 34 is formed at a position where an optimum gap 32 can be formed between the support step portion 34 and the tip of the magnetic core 18 of the pole piece portion 14. The support step portion 34 is formed to be larger than the inner diameter of the housing body 2, and the upper surface portion thereof has a flat surface in order to stabilize the support of the vibrating body 4. The magnetic force of the magnet 30 is used to hold the vibrating body 4 installed on the support step portion 34. In some cases, the support step portion 34 may be formed on the magnet 30 side to support the vibrating body 4.

A second support step 36 for supporting the cover plate 8 is formed in the opening of the housing body 2. The inner diameter of the wall surface portion 38 that surrounds the support step portion 36 is set to be larger than that of the support step portion 36. The lid plate 8 has a circular shape that matches the inner diameter of the support step portion 36 of the housing body 2, and the peripheral edge portion thereof is supported on the support step portion 36 of the housing 2 as well as the support step portion. The portion 36 is fitted and fixed in the wall surface portion of the housing body 2. The lid plate 8 can be formed of a magnetic material plate such as a resin plate or permalloy. That is,
The cover plate 8 forms a closing means for closing the opening of the housing body 2, and forms a resonance chamber 40 as a resonance space on the upper surface side of the vibrating body 4. The supporting step portion 36 is closely related to the size of the resonance chamber 40 to be formed on the front surface side of the vibrating body 4, and if the inner diameter of the housing body 2 is constant, the vibration is supported by the supporting step portion 34. The upper surface of the body 4 and the support step 36
The volume of the resonance chamber 40 is determined by the gap between the lid plate 8 and the inner surface of the lid plate 8.

A sound emission hole 42 is formed in the cover plate 8 as a means for emitting the resonance sound of the resonance chamber 40 to the outside. The sound output hole 42 may be formed at any position, and in the case of this embodiment, it is set at a position displaced from the center of the vibrating body 4, that is, the position of the magnetic piece 12. The shape and size of the sound output hole 42 are arbitrary, but in the case of this embodiment, the sound output hole 42 is circular and its size is almost the same as the magnetic piece 12 of the vibrating body 4. That is, there is a distance L1 between the center of vibration of the vibrating body 4 and the center of the sound output hole 42.
The diameter L2 of is related to the utilization of the resonance space of the resonance chamber 40.

Further, in the electromagnetic acoustic transducer of this embodiment, the cover plate 8 constitutes a regulating means for the vertical movement range of the vibrating body 4, and the gap between the magnetic piece 12 of the vibrating body 4 and the cover plate 8. L3
Has been narrowed. Moreover, the sound output hole 42 is formed by the magnetic piece 12
Since it is displaced from the position, the portion of the magnetic piece 12 of the vibrating body 4, that is, the center of gravity is received by the central portion of the cover plate 8.

With respect to the electromagnetic acoustic transducer configured as described above, its operation and the function of each part will be described.

When an AC signal is applied between the terminals 26 and 28, the coil 24 is excited by the AC signal. As a result, an alternating magnetic field that opposes the bias magnetic field generated by the magnet 30 is generated in the pole piece portion 14, and this alternating magnetic field acts on the vibrating body 4 through the magnetic core 18. As a result, the vibrating body 4 repeatedly vibrates in the vertical direction in the drawing, and the vibration causes the resonance chamber 40 to resonate. As a result, the resonance sound is emitted from the sound output hole 42 to the outside.

In such an electromagnetic acoustic transducer, the cover plate 8 is made of a thin plate, and the electromagnetic acoustic transducer is flattened,
The size and the weight are reduced. In this embodiment, the thin plate 8 is formed of a permalloy plate, but a thin plate can be achieved by using a resin plate as compared with the conventional molding of a container-shaped housing. In the case of a permalloy plate, its wall thickness is extremely thin, and can be set to a thickness of, for example, about 0.2 mm, so that the housing can be made thin.

When the cover plate 8 is made of a magnetic material, especially permalloy, the cover plate 8 functions as a shield plate for covering the front side of the vibrating body 4. Moreover, the lid plate 8 forms a closed magnetic path with the vibrating body 4 together with the magnetic drive unit 6 side, and magnetic leakage can be suppressed. In particular, since the vibrating body 4 is arranged between the lid plate 8 made of a magnetic plate and the magnetic core 18, the influence of the gap 32 between the vibrating body 4 and the magnetic core 18 on the center frequency Fo value is reduced. Therefore, the characteristics can be stabilized.

The distance between the lid plate 8 and the vibrating body 4 is set to a width slightly exceeding the vibration allowable range of the vibrating body 4 during normal operation, that is, the both are brought close to each other, so that the lid plate 8 is placed in the vibrating body 4. Function as a control means of the movement range of the. Moreover, the sound output hole 42
Since the position of is displaced from the center position of the vibrating body 4, the magnetic piece 12 hits the lid plate 8 to achieve the movement restricting function of the vibrating body 4, and as a result, the destruction of the vibrating body 4 can be prevented. .

In the electromagnetic acoustic transducer of this embodiment, the resonance chamber 40 is narrowed to flatten the electromagnetic acoustic transducer. However, by displacing the position of the sound output hole 42 from the center position of the vibrating body 4, a distance L1 is generated between the vibration center of the vibrating body 4 and the sound emitting hole 42.
1 is connected to the substantial expansion of the resonance space of the resonance chamber 40, and the resonance sound can be enhanced.

Further, since the housing body 2 has a relatively simple shape in which the supporting step portions 34 and 36 are formed on the cylindrical body, the molding accuracy of the synthetic resin is high, and the product can be made uniform and miniaturized. In addition, it is not necessary to set the wall thickness by the bent portion, and the manufacturing can be simplified.

Next, the experimental results of the electromagnetic acoustic transducer of the present invention will be described.

FIGS. 3 and 4 show operating characteristics depending on the material of the cover plate, FIG. 3 shows sound pressure characteristics at an input frequency of 1 kHz to 3 kHz, and FIG. 4 shows current consumption characteristics at an input frequency of 1 kHz to 3 kHz. In FIGS. 3 and 4, the characteristic A is that when Permalloy is used as the magnetic material,
Characteristic B is the case where brass is used as the non-magnetic material for cover plate 8, and characteristic C is the case where plastic is used as the non-magnetic material. When measuring the characteristics A to C, the applied voltage is a pulse voltage with an amplitude of 1.5 V with 0 V as a reference. Comparing the characteristics A, B and C, the peak point of the sound pressure level of the characteristic A is higher than that of the characteristics B and C, and the frequency shifts to 2.2 kHz. “A” indicates a difference in sound pressure level. Also, in comparison of the overall sound pressure level, 2k
Although the sound pressure levels of the characteristics B and C reach the peak point in the vicinity of Hz, the sound pressure level of the characteristic A is high as a whole. b indicates the difference in sound pressure level between the characteristics A and the characteristics B and C, and indicates an increase in sound pressure level of 5 dB or more. Also in the comparison of the consumption currents, the characteristic A is decreased in the entire frequency range as compared with the characteristics B and C, the internal resistance of the resonance part is remarkably increased, and the consumption current is decreased.
c shows the difference, and the current value far exceeds 5 mA. As described above, when the cover plate 8 is made of a magnetic material, magnetic leakage can be suppressed. As a result, the sound pressure level can be increased, the current consumption can be reduced, and the efficiency can be improved.

Next, FIG. 5 and FIG. 6 show operating characteristics depending on the position of the sound output hole 42. FIG. 5 shows an input frequency of 1 kHz to 3 kHz.
Sound pressure characteristics at kHz, FIG. 6 shows input frequency 1 kHz-
The current consumption characteristics at 3 kHz are shown. 5 and 6
In the characteristic A, the eccentric position (the embodiment of FIG. 2) and the characteristic B are
Is the characteristic of the central position. The measurement conditions are the same as the operating characteristics shown in FIGS. As is clear from the characteristics A and B, when the sound output hole 42 is eccentric, the resonance frequency is lowered and the sound pressure level is increased by the level difference g, which shows that the consumption current is reduced. This is because the sound output hole 42 is eccentric, and as a result, the sound pressure level is enhanced and the efficiency is improved due to the resonance effect of the resonance chamber 40.

Next, FIG. 7, FIG. 8, FIG. 9 and FIG. 10 show operating characteristics at an input frequency of 1 kHz to 3 kHz depending on the applied voltage. In FIG. 7, when the cover plate 8 is made of brass, FIG. FIG. 9 shows current consumption characteristics when the cover plate 8 is made of brass, FIG. 9 shows sound pressure characteristics when the cover plate 8 is made of permalloy, and FIG. 10 shows current consumption characteristics when the cover plate 8 is made of permalloy. There is. Throughout the drawings, the characteristic A is 1.0V, the characteristic B is 1.5V, and the characteristic B is 2.0V. Such a change in the applied voltage equivalently changes the size of the gap 32 between the vibrating body 4 and the magnetic core 18 of the magnetic drive unit 6, and how the gap 32 affects the frequency characteristic. This is because it is to see whether the magnetic envelopment effect due to As a result of such an experiment, brass, that is,
When a non-magnetic material is used, as is clear from FIG. 7, the frequency at the peak point of the sound pressure level decreases as the applied voltage increases. As is clear from FIG. 8, such a relationship also occurs in the consumed current, and the minimum resonance frequency Fo of the vibrating body 4 shows a significant frequency change e as the applied voltage increases. On the other hand, when permalloy, that is, a magnetic material is used for the cover plate 8, even if the applied voltage changes, the frequency at which the peak point of the sound pressure level changes does not change at all, as is apparent from FIG. Absent. That is, the sound pressure level changes only in a similar manner according to the applied voltage. As is clear from FIG. 10, such a relationship is the same in the consumption current, and the lowest resonance frequency Fo of the vibrating body 4 is obtained.
Causes a small frequency change f even if the applied voltage changes. Thus, when the lid plate 8 is made of a non-magnetic material, the minimum resonance frequency Fo, which is a typical value of the frequency characteristic, fluctuates remarkably and reacts sensitively to changes in the gap 32. When a magnetic material is used for the above, only the frequency fluctuation is recognized, and it is understood that the influence of the change in the gap 32 is small. As is clear from such operation characteristics, when the lid plate 8 is made of a magnetic material, there is no magnetic leakage, magnetic efficiency is improved, operation characteristics are stable, and excellent acoustic conversion characteristics are obtained. Has been obtained.

[0041]

As described above, according to the present invention,
The following effects can be obtained. a. Since the housing is composed of the housing body and the lid plate, and the lid plate is made thin, mass production is facilitated, and the electromagnetic acoustic transducer can be downsized, flattened, and lightweight. b. The lid plate can be set as the movement restricting means of the vibrating body, the displacement of the vibrating body due to an impact during transport or excessive input can be prevented, and the vibrating body can be protected from destruction. c. If the thin body is made of a magnetic material, the front side of the vibrating body can be shielded by the lid plate and magnetic leakage can be prevented,
Since the center frequency can be stabilized, stable operation can be realized.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of an electromagnetic acoustic transducer of the present invention.

2 is a sectional view taken along line II-II of the electromagnetic acoustic transducer shown in FIG.

FIG. 3 is a diagram showing frequency-sound pressure characteristics of an electromagnetic acoustic transducer made of a cover plate forming material.

FIG. 4 is a diagram showing frequency-current consumption characteristics of an electromagnetic acoustic transducer made of a material forming a cover plate.

FIG. 5 shows the frequency of the electromagnetic acoustic transducer depending on the position of the sound output hole.
It is a figure which shows a sound pressure characteristic.

FIG. 6 shows the frequency of the electromagnetic acoustic transducer depending on the position of the sound output hole.
It is a figure which shows a consumption current characteristic.

FIG. 7 is a diagram showing frequency-sound pressure characteristics of an electromagnetic acoustic transducer according to an applied voltage.

FIG. 8 is a diagram showing a frequency-current consumption characteristic of an electromagnetic acoustic transducer according to an applied voltage.

FIG. 9 is a diagram showing frequency-sound pressure characteristics of the electromagnetic acoustic transducer when the cover plate is made of permalloy.

FIG. 10 is a diagram showing frequency-current consumption characteristics of the electromagnetic acoustic transducer when the cover plate is made of permalloy.

FIG. 11 is a vertical sectional view of a conventional electromagnetic acoustic transducer.

FIG. 12 is a vertical sectional view of a conventional electromagnetic acoustic transducer.

FIG. 13 is a vertical sectional view of a conventional electromagnetic acoustic transducer.

FIG. 14 is a vertical sectional view of a conventional electromagnetic acoustic transducer.

[Explanation of symbols]

 2 housing body 4 vibrating body 6 magnetic drive unit 8 lid plate 10 resonance plate 12 magnetic piece 42 sound output hole

Claims (4)

[Claims] 1. A housing main body having a cylindrical body, a vibrating body supported by the housing main body and vibrating, and a thin plate made of a member different from the housing main body to close an opening of the housing main body. And a magnetic drive unit that is installed on the back side of the vibrating body and vibrates the resonance plate, the electromagnetic acoustic transducer. 2. The electromagnetic acoustic transducer according to claim 1, wherein the lid plate is made of a magnetic material. 3. The electromagnetic acoustic transducer according to claim 1, wherein the cover plate is used as a means for restricting a moving range of the vibrating body. 4. The cover plate has a sound output hole formed at a position displaced from the magnetic piece of the vibrating body.
The electromagnetic acoustic transducer described.