WO2012085350A1

WO2012085350A1 - Thin loudspeaker construction.

Info

Publication number: WO2012085350A1
Application number: PCT/FI2011/051144
Authority: WO
Inventors: Timo Kujala; Petteri Hirvanen
Original assignee: Nexu Oy
Priority date: 2010-12-23
Filing date: 2011-12-21
Publication date: 2012-06-28
Also published as: FI20106369A0

Abstract

Loudspeaker construction, which comprises a body (9), a sound-producing vibrating element (8), and at least one electromagnet. There are mainly at least two magnets (4, 7), of which at least one is attached to the vibrating element (8) and at least one is attached to the body structures (9). At least one of the magnets is an electromagnet (4) and the other is an electromagnet, a permanent magnet, or a piece (7) of ferromagnetic material, located within the area of influence of the magnetic flux of the electromagnet.

Description

THIN LOUDSPEAKER CONSTRUCTION

The present invention relates to a loudspeaker construction and more specifically to a loudspeaker construction that can be extremely thin.

The specific construction of the traditional loudspeaker type in present audio use, which is depicted as the prior art in Figures 1a and 1b, is characterized in that the magnetic moment of the voice coil 5' is always significantly less than that of the permanent magnet, which consists of pieces 1', 2', 3', and 4'. This ratio can also be observed in the mutual dimensions and weights of the voice coil and the magnet. Due to this kind of construction, the thickness of the loudspeaker compared to the movement produced by the vibrating element, i.e. the cone 6', is extremely large.

The voice coil of a traditional loudspeaker consists of a thin cylindrical tube, around which there is a winding. The voice coil is the part of a traditional loudspeaker that is most liable to break. The air gap remaining between the iron core and the permanent magnet is very small. For this reason, the conductor wire must be wound as a thin layer around the cylindrical tube of the voice coil.

Because the space is small, only a limited amount of conductor wire can be wound.

Due to the construction, the narrow air gap significantly increases the risk that the voice coil will begin to rub on the permanent magnet. This can happen, for example, to a loudspeaker that is installed in a space in which moisture condenses and which does not have sufficient ventilation for long periods of time, such as in automobiles. As a result of this, the dimensions of the parts 1' and 4' of the permanent magnet increase as a result of corrosion. The air gap then becomes too restricted for the movement of the voice coil, as a result of which the

loudspeaker is unable to operate normally and thus causes distortions and mechanical noises. Finally, the lacquering of the winding of the voice coil is damaged, causing a short-circuit, when the loudspeaker element ceases to function. A manufacturing fault in the positioning of the voice coil can also cause the aforementioned damage. A mechanical, external force can also detach the gluing of the pole piece 1', in which case the pole piece, being of a ferromagnetic material, will tend to move towards the permanent magnet, thus completely preventing the movement of the voice coil.

Due to the numerous similar poor properties plaguing a traditional loudspeaker, there has been for a long time in the field a need to develop a loudspeaker construction, in which the said drawbacks would not appear.

The present invention is intended to create a loudspeaker construction, the risk of the breaking of which is very low, and which, on account of its size and/or weight, is suitable for very many applications, for which a traditional loudspeaker is not suitable.

The aforementioned and other advantages and benefits of the present invention are achieved in the manner described as characteristic in the accompanying claims.

Alternatives of the loudspeaker construction according to the present invention are presented in greater detail in the accompanying figures, in which: Figure 1a shows a cross-section of a traditional loudspeaker;

Figure 1b shows an exploded view of the loudspeaker of Figure 1a;

Figure 2 shows an exploded view of one embodiment according to the invention;

Figure 3 shows a cross-section of the embodiment of Figure 2;

Figures 4 and 5 show exploded and cross-sectional views of a second

embodiment of the invention;

Figure 6 shows various construction alternatives of the embodiment shown in Figures 2 and 3; and

Figure 7 shows correspondingly construction alternatives of the embodiment of Figures 4 and 5.

Figures 1a and 1b show a traditional loudspeaker, in which are used a voice coil 5' and a permanent magnet, which consists of the following components: a

permanent-magnet core 3' and permanently attached ferromagnetic pieces, which are a rearmost magnet body 2', a foremost magnet body 4', and the voice-coil pole piece attached to the rearmost magnet body. The voice coil consist of a thin cylindrical tube, around which is a winding. A vibrating cone 6' is attached to the voice coil 5' as well as being attached to the frame 7' by mountings. The voice coil is generally wound with thin copper wire. The figure also shows the voice coil's movement guide 8' and the connector 9', to which the loudspeaker's control signal is fed. A hole 10' permits a flow of air to move in the construction.

In the present presentation, the loudspeaker construction according to the invention is referred to as thin loudspeaker. Briefly, the operation of the thin loudspeaker is based on at least two magnets, the magnetic moments of which are close to each other, and the magnetic flue of at least one magnet can be varied according to some frequency or frequencies. The magnet pairs or groups react to the variations in the electromagnetic field by moving. The ratios of the magnetic moments can be selected in order to optimize the properties of the loudspeaker for different requirements, which is not possible when using traditional loudspeakers.

The loudspeaker constructions according to the invention are of two different types. In the first type, which is depicted as an example in Figures 2 and 3, the permanent magnet and electromagnet are opposite to each other. In the second type, which, for its part, is depicted in Figures 4 and 5, the permanent magnet and electromagnet are placed at least partly one inside the other. A ferromagnetic iron core, or an non-magnetic material is used as the material of the winding support 5 of the electromagnet 4 of the embodiments shown in

Figures 2 - 5. The winding support 5 and the end plates 2 protect the winding of the electromagnet. The control signal is connected to the terminals 3 of the winding of the electromagnet. The mounting 6 of the thin loudspeaker to the vibrating element can be similar to that in traditional loudspeakers. Air holes 10 are marked in the casing 9, though they are often not essential for the operation of the loudspeaker according to the invention. Figures 4 and 5 show a second embodiment, in which the fixed electromagnet 4 and the permanent magnet 7 attached to the vibrating surface by means of a positioning platform 11 are located one inside the other. The permanent magnet can be secured in place, for example, by an adhesive, by screws, by rivets, or integrated in the construction, or by means of a combination 1 of these.

Unlike in a traditional loudspeaker construction, the permanent magnet of the loudspeaker according to the invention can, if necessary, always be made from a single piece, and thus it is simple, light, and cheap. Without exception, the permanent magnet of a traditional loudspeaker is made from several pieces.

In the characteristic construction of the thin loudspeaker, the electromagnet's cooling plates 2 and iron core or winding support 5 protect the winding, preventing the winding from rubbing on the moving parts. Thus, in the thin loudspeaker, there is no narrow air gap between the winding and permanent magnet according to the characteristic construction of a traditional loudspeaker, and for this reason it is not liable to mechanical damage caused by external impacts. In a traditional loudspeaker, the winding of the voice coil is in the immediate vicinity of the moving components and, for this reason, is extremely liable to damage. In the thin loudspeaker, the winding support and permanent magnet are close to each other, but the tolerance is nevertheless considerably greater by an order of magnitude than that in a traditional loudspeaker and, due to the low friction, they are not liable to be damaged, even if they rub together. From the point of view of manufacturing technology, the thin loudspeaker can be regarded as having the advantage of not being particularly susceptible to errors in tolerance.

Thanks to the technical construction of the thin loudspeaker, the loudspeaker can be made very thin and light. In a thin loudspeaker it is also possible to exploit the entire diameter of the loudspeaker enclosure, so that the length of the winding wire can be defined as required in each case while the iron core/winding support can nevertheless be low. Thus, strong magnetic fields can be created. This permits permanent magnets of a smaller size to be used, so that a great degree of freedom in the design of loudspeaker elements is achieved. In the elements of loudspeaker constructions according to the invention, the number and locations of the cones, mountings, electromagnets, and permanent magnets can be varied. If a very powerful loudspeaker with smaller dimensions is needed, two permanent and electromagnets can be used, as shown in Figure 6a. The permanent and electromagnets can also be the other way round, as shown in Figure 6b, i.e. two permanent magnets 7in the body have a single common electromagnet 4 attached to the vibrating element 8.

If the electromagnet is attached to the vibrating element, greater mass will be obtained in the vibrating element, without increasing the total mass of the element. Figure 6c shows a solution, in which two vibrating elements 8 are used, which there are permanent magnets 7, which are acted on by a common electromagnet 4 located in the centre of the body. If it is desired that the element is magnetic only during operation, it can be implemented using two electromagnets 4" according to Figure 6d, in which case the loudspeaker will be completely non-magnetic in the quiescent state. Alternating current is fed to one electromagnet 4 and direct current or anti-phase alternating current to the other 4". In all the various

constructions, permanent magnets can be replaced with electromagnets. The same effect is also created by replacing the permanent magnet with a

ferromagnetic piece.

The double construction of the vibrating element shown in Figure 7a, in which both vibrating elements make the same movement, can also be implemented from the Type-2 construction. In this construction, the permanent-magnet structure 7 is in the centre. The said structure 7 is attached to both cones 8 and moves in a hole inside the electromagnet 4.

The elongated element according to Figure 7b, which fits into a small space, can be implemented by using a permanent magnet 7 moving inside an electromagnet 4, which permanent magnet is attached to an elongated cone 8 manufactured from a flexible material. The cone is attached at only one end to the case 9. The permanent magnet 7 is attached to a vibrating element 8.

By means of the construction shown in Figure 7c, very small-sized loudspeakers can be implemented, in such a way that the permanent magnet 7, which is at least partly inside the electromagnets 4, also acts at the same time as the vibrating element. The suspension 6 is attached to the body of the electromagnet.

If a large path of movement is desired for the cone, such a construction can be made, for example, using helical springs and a possible guide pin, according to Figure 7d. In this construction, there is a moving permanent magnet 7 inside the electromagnet 4, which at the same time also acts as a vibrating element. The helical spring or other spring material 13 acts as a mounting and the construction can include a possible guide 14. The spring 13 is secured by an attachment collar 15, which is of a durable non-magnetic material.

Thanks to the new type of characteristic construction of the thin loudspeaker according to the invention, it is possible to build extremely small loudspeakers that are specifically thin and light in mass with a durable structure, which are also able to reproduce very low frequencies effectively.

Using a thin loudspeaker, a higher efficiency and better operational reliability than in traditional loudspeakers can be achieved. The characteristic construction of the thin loudspeaker permits the use of permanent magnets of considerably small size. The voice coil of a traditional loudspeaker is replaced with a powerful electromagnet or electromagnets, depending on the desired properties, such as the target size, power range, sensitivity, and frequency range.

Highly suitable applications for the loudspeaker construction according to the invention are all structures, in which traditional loudspeakers are either too unreliable, such as fixed solutions integrated in various structures, or which are unsuitable by their dimensions or weight. Thin loudspeakers withstand very demanding environmental conditions, such as cold, heat, dust, moisture, and external mechanical strain, and retain their operating ability even under water. Numerous fields, such as various welfare applications, can be given as

applications:

- work and leisure massage chairs,

- physic therapy beds, for instance, in hospital, in welfare and care institutions for the elderly, and in both the private and public sectors,

- blood-circulation activating seats in work vehicles (trucks, tractors, forestry machines, buses, taxis, etc., as well as aircraft and long-distance trains and buses),

- chairs maintaining concentration, e.g., in control rooms.

Thanks to their construction, reliability, and ease of production, thin loudspeakers according to the invention are also suitable for many of the applications of traditional loudspeakers, such as:

- computers

- game consoles

- flat-panel televisions

- lifts

- public-address-system loudspeakers indoors and outdoors

- trains, ships, oil-drilling rigs

- audio loudspeakers

- special applications (for example, underwater research).

The loudspeaker construction according to the invention brings many different advantages compared to traditional loudspeaker constructions. Specific basic constructions are described above, which can be varied in many ways within the scope of the inventive idea and the accompanying Claims.

Claims

1. Loudspeaker construction, which includes a body (9), a sound-producing vibrating element (8), and the necessary structures for producing movement in the vibrating element (8), including at least one electromagnet (4) and, in addition, either a piece of ferromagnetic material, a permanent magnet (7), or an additional electromagnet, characterized in that at least one of the aforementioned is attached to the vibrating element (8') and at least one is attached to the body structures (9¹) in an essentially opposed position, or with one at least partly inside the other.

2. Loudspeaker construction according to Claim 1 , characterized in that, in the nesting position, the piece of a ferromagnetic material, or the permanent magnet (7) is located essentially inside an annular electromagnet.

3. Loudspeaker construction according to Claim 1 , characterized in that, in the case of the electromagnet (4) and permanent magnet (7)/second electromagnet (4"), the magnetic moments of the said magnets are of the same order of magnitude and their mutual relationsships can be adjusted if desired.

4. Loudspeaker construction according to Claim 1 , characterized in that it includes two magnets, of which one is an electromagnet (4) and the other is a permanent magnet (7).

5. Loudspeaker construction according to any of the above Claims, characterized in that the permanent magnet (7) is a one-part piece.

6. Loudspeaker construction according to any of the above Claims, characterized in that the permanent magnet/magnets (7) of the construction are moving elements and the electromagnet/magnets (4) are stationary, or vice versa.

7. Loudspeaker construction according to Claim 1 , characterized in that there are at least two vibrating elements (8').

8. Loudspeaker construction according to any of the above Claims, characterized in that the electromagnet/magnets (4) and the permanent magnet/magnets (7) are located essentially centrally relative to the vibrating element (8).

9. Loudspeaker construction according to any of the above Claims, characterized in that the electromagnet/magnets (4) and the permanent magnet/magnets (7) are located in an arrangement with one at least partly inside the other.

10. Loudspeaker construction according to any of the above Claims,

characterized in that the magnets (4, 7) are in an essentially opposing order relative to each other.

11. Loudspeaker construction according to any of the above Claims,

characterized in that the construction comprises two electromagnets (4, 4"), one of which is located in the obdy (9) and the other is located in the vibrating element (8).

12. Loudspeaker construction according to any of the above Claims,

characterized in that the construction comprises two vibrating elements (8), two permanent magnets (7), and one electromagnet (4).

13. Loudspeaker construction according to any of the above Claims,

characterized in that the positioning of the magnet or magnets relative to the vibrating element (8) is eccentric.

14. Loudspeaker construction according to any of the above Claims,

characterized in that the electromagnet/magnets (4) contain a metal core or winding frame (5), which, if desired, can be of a non-magnet material.

15. Loudspeaker construction according to any of the above Claims,

characterized in that the winding support (5) insulates the electromagnet's winding (4) and the permanent magnet (7) from each other.