Patent Application
20060245614
The present invention contains subject matter related to Japanese Patent Application JP 2005-130309 filed in the Japanese Patent Office on Apr. 27, 2005, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vibrating device configured to apply vibration to a gas to generate a jet flow of the gas and, more specifically, relates to a jet flow generating apparatus including the vibrating device and an electronic apparatus including the jet flow generating apparatus.
2. Description of the Related Art
A known problem accompanying the advancement of the performance of personal computers (PCs) is an increase in the amount of heat dispersed from heat-generating bodies, such as integrated circuits (ICs). Various technologies for dispersing heat have been proposed, and products employing such technologies have been produced. As a method of dispersing heat, a heat-radiating fin composed of metal, such as aluminum, is disposed in contact with an IC so that heat is transmitted from the IC to the fin. As another method of dispersing heat, a fan may be used to disperse heat by, for example, forcefully exhausting warm air in the chassis of a PC by guiding low-temperature air around the heat-generating body. Moreover, both a heat-radiating fin and a fan may be used to increase the contact area of the heat-generating body and air at the heat-radiating fin while forcing the fan to exhaust warm air around the heat-radiating fin.
However, forced exhaust of air by means of a fan causes a thermal boundary layer to be generated at the surface of the heat-radiating fin on the side of the lower flow. As a result, heat is not efficiently dispersed from the heat-radiating fin. To solve this problem, for example, the thickness of the thermal boundary layer can be reduced by increasing the wind velocity produced by the fan. However, in order to increase the wind velocity, the number of revolutions per unit time of the fan has to be increased. As a result, noise, such as wind noise, caused by the fan moving through the air is generated.
There is also a method of efficiently radiating heat from the heat-radiating fin to the outside air by breaking down the thermal boundary layer without use of a fan as air-blowing means but, instead, using a vibration plate that reciprocates periodically (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2000-223871, 2000-114760, 2-213200, and 3-116961). In particular, the apparatuses according to Japanese Unexamined Patent Application Publication Nos. 2-213200 and 3-116961 each include a vibrating plate that divides the space inside a chamber substantially in half, an elastic body that is provided in the chamber to support the vibrating plate, and vibrating means for vibrating the vibrating plate. In such an apparatus, for example, when the vibrating plate is displaced in the upward direction, the volume of the upper space of the chamber decreases. As a result, the pressure in the upper space in the chamber increases. Since the upper space communicates with the outside air through an exhaust port, the raised pressure in the upper space causes some of the air inside the upper space to be exhausted to the outside. At the same time, the volume of the lower space of the chamber on the opposite side of the vibrating plate from the upper space increases, causing the pressure in the lower space to decrease. Since the lower space communicates with the outside air through an exhaust port, the lowered pressure in the lower space causes some outside air in the vicinity of the exhaust port to be drawn into the lower space. In contrast, when the vibrating plate is displaced in a downward direction, the volume of the upper space of the chamber increases. As a result, the pressure in the upper space in the chamber decreases. Since the upper space communicates with the outside air through an exhaust port, the lowered pressure in the upper space causes some outside air in the vicinity of the exhaust port to be drawn into the upper space. At the same time, the volume of the lower space of the chamber on the opposite side of the vibrating plate from the upper space decreases, causing the pressure in the lower space to increase. The raised pressure in the lower space causes some of the air inside the upper space to be exhausted to the outside. The vibrating plate is driven by, for example, electromagnetic force. By driving the vibrating plate in such a reciprocating manner, a movement for exhausting air inside to the chamber to the outside and a movement for taking outside air into the chamber are repeated periodically. As a result, a pulsating flow of air is generated by the periodical reciprocating movement of the vibrating plate. This pulsating flow impinges upon a heat-generating body, such as a heat-radiating fin (heat sink), causing the thermal boundary layer at the surface of the heat-radiating fin to be efficiently broke down. Consequently, the heat-radiating fin is efficiently cooled.
However, when the amount of heat generated by the heat-generating body is great, a device having a high cooling ability, i.e., a device having a great gas discharge amount, will be required. In particular, since the amount of heat generated by a central processing unit (CPU) has been increasing every year, it is necessary to efficiently cool a CPU. To increase the gas discharge amount, the amplitude of the vibrating plate can be increased. However, if the amplitude is increased too much, the vibrating plate will bend, and vibration will not be efficiently transmitted to the gas. As a result, extreme noise will be generated.
Embodiments of the present invention address the above-identified problems and other problems associated with known apparatuses to provide a vibrating device capable of suppressing noise without reducing the gas discharge amount, a jet flow generating apparatus including the vibrating device, and an electronic apparatus including the jet flow generating apparatus.
A vibrating device according to an embodiment of the present invention is configured to vibrate a gas inside a chassis to discharge the gas in a pulsating flow through an opening formed in the chassis and includes a frame, a vibrating plate, a supporting member that is attached to the frame and that is configured to support the vibrating plate in a manner such that the vibrating plate is vibratable, and a driving mechanism that is configured to drive the vibrating plate and includes a magnetic circuit member attached to the frame and a voice coil body. The voice coil body is configured to prevent the voice coil body from contacting the magnetic circuit member when the vibrating plate is vibrating and is attached to the vibrating plate in a manner such that the voice coil body is movable by means of a magnetic field generated by the magnetic circuit member.
Since the driving mechanism according to an embodiment of the present invention includes a voice coil body configured to prevent the voice coil body from coming into contact with the magnetic circuit member when the vibrating plate is vibrating, unwanted noise caused by the voice coil body contacting the magnetic circuit member is suppressed. Accordingly, noise can be suppressed, for example, while maintaining a predetermined gas discharge amount without reducing the frequency and amplitude of the vibrating plate.
The gas is, for example, air. However, the gas is not limited to air and, instead, may be an inactive gas, such as nitrogen gas, helium gas, or argon gas, or any other gas.
According to an embodiment of the present invention, the magnetic circuit member includes a magnet magnetized in the vibration direction of the vibrating plate and a yoke having a magnetic plate attached to the vibrating plate side of the magnet at a first position along the vibration direction and a magnetic cylinder forming a magnetic gap between the magnet plate and forming a space between the magnet. The voice coil body includes a tip, a coil, and a bobbin on which the coil is wound. The voice coil body moves in the vibration direction in the space to prevent at least one of the tip and the coil from coming into contact with the magnetic circuit member. The tip of the voice coil body may contact the magnetic circuit member if the voice coil body tilts in a direction other than the vibration direction. Therefore, the voice coil body can be moved so that at least one of the tip or the coil does not contact the magnetic circuit member.
The supporting member supports the vibrating plate at a second position that is a position along the vibration direction on a plane substantially orthogonal to the vibration direction of the vibrating plate. The tip of the voice coil body is disposed at a third position a predetermined distance away from the second position in the vibration direction. The predetermined distance is determined from a function of a third length that is the sum of a first length and a second length in which the first length is the minimum length from the center of the vibrating plate to the peripheral edge on the plane and the second length is half the length from the peripheral edge to the frame in the same direction as the first length.
More specifically, the following formula is satisfied:
d<[(G−t)R]/(2X)
where d [mm] represents the predetermined distance, R [mm] represents the third length, G [mm] represents the magnetic gap, t [mm] represents the thickness of the voice coil body in the space, and X [mm] represents the displacement in the vibration direction of the supporting member when the vibrating plate moves in a direction other than the vibration direction, the supporting member being disposed away from the center of the vibrating plate by a distance equal to the third length.
A practical length for the third length R is in the range of 5 to 100 mm when the size of the electronic apparatus including the vibrating device varies from a small portable audio apparatus to a large display apparatus.
In particular, it is desirable that, when the third length R is in the range of 10 to 40 mm, the predetermined distance d be in the range of 0 to 20 mm or 0 to 10 mm. For example, when a portable apparatus is to be provided as the electronic apparatus including the vibrating device, the most practical third length R for the portable apparatus is in the range of 10 to 40 mm. More desirable, the third length R is in the range of 15 to 35 mm. In this case, when the above-mentioned formula is applied, the distance d is in the range of 0 to 20 mm or 0 to 10 mm. When distance d equals zero, the supporting member will support the vibrating plate on the plane where the magnetic plate is disposed, reducing the thickness of the vibrating device.
The supporting member supports the vibrating plate at a second position that is a predetermined distance away from the first position in the vibration direction on a plane substantially orthogonal to the vibration direction. When the magnetic gap is smaller than the width of the space on the plane, the predetermined length is determined from a function of a third length that is the sum of a first length and a second length, where the first length is the minimum length from the center of the vibrating plate to the peripheral edge on the plane and the second length is half the length from the peripheral edge to the frame in the direction of the first length.
In this case, also, the following formula is satisfied:
d<[(G−t)R]/(2X)
where d [mm] represents the predetermined distance, R [mm] represents the third length, G [mm] represents the magnetic gap, t [mm] represents the thickness of the voice coil body in the space, and X [mm] represents the displacement in the vibration direction of the supporting member when the vibrating plate moves in a direction other than the vibration direction, the supporting member being disposed away from the center of the vibrating plate by a distance equal to the third length.
In this case, when a practical configuration is considered, it is desirable that, when the third length R is in the range of 10 to 40 mm, the predetermined distance d is in the range of 0 to 10 mm or 0 to 5 mm.
According to an embodiment of the present invention, the voice coil body is attached to the vibrating plate at a fourth position that is a position different from the second position along the vibrating direction. The fourth position is closer to the magnet than the second position or the fourth position is further from the magnet than the second position. In such case, the vibrating plate does not have to be flat and may be cone-shaped or a side plate may be provided. By providing a three-dimensional vibrating plate, instead of a flat vibrating plate, the rigidity of the vibrating plate is increased, and bending of the vibrating plate can be suppressed to enable efficient vibration. As a result, the gas discharge efficiency is increased. In particular, if the fourth position is provided opposite to the first position in the vibration direction relative to the second position, the thickness of the vibrating device can be reduced.
The side plate of the vibrating plate may be vertically disposed substantially parallel to the vibration direction of the vibrating plate but is not limited to a vertical position. The side plate may be disposed as a continuous structure. In other words, the side plate may be disposed at the periphery of a flat plate disposed substantially orthogonal to the vibration direction or more inward than at the periphery of the flat plate.
According to an embodiment of the present invention, the vibrating plate includes a first flat plate supported by the supporting member, and a second flat plate attached to the voice coil body and substantially parallel to the first flat plate. In this case, also, the vibrating plate is three-dimensional, instead of being flat, and the rigidity of the vibrating plate can be increased.
According to an embodiment of the present invention, the voice coil body is attached to the vibrating plate at substantially the same position as the second position in the vibration direction. In such a case, the vibrating plate is often flat. However, the shape is not limited thereto.
According to an embodiment of the present invention, the driving mechanism includes a vibrating plate that has a side plate supported by a supporting member and a flat plate attached to a voice coil body. The driving mechanism includes an electric supply line that is connected to the voice coil body and disposed along the first flat plate and the second flat plate. According to such a configuration, the vibrating plate and the electric supply line move as a unit, preventing the electric supply line from breaking when the vibrating plate vibrates.
According to an embodiment of the present invention, the cross-section of vibrating plate along a plane substantially orthogonal to the vibration direction is shaped as one of a circle, an oval, a polygon, and a polygon with rounded corners. A polygon with rounded corners is an area surrounded with straight lines and curved lines and may be any polygon having rounded corners.
A jet flow generating apparatus according to an embodiment of the present invention includes a frame, a chassis that has an opening and is configured to support the frame and accommodate gas inside, a vibrating plate configured to vibrate to discharge the gas in a pulsating flow through the opening, a supporting member that is attached to the frame and is configured to support the vibrating plate in a manner such that the vibrating plate is vibratable, and a driving mechanism that is configured to drive the vibrating plate and includes a magnetic circuit member attached to the frame, and a driving mechanism that is configured to drive the vibrating plate and that includes a magnetic circuit member attached to the frame and a voice coil body attached to the vibrating plate. The voice coil body is configured to prevent the voice coil body from contacting the magnetic circuit member when the vibrating plate is vibrating and is attached to the vibrating plate in a manner such that the voice coil body is movable by means of a magnetic field generated by the magnetic circuit member.
A jet flow generating apparatus according to another embodiment of the present invention includes a chassis that has an opening and that accommodates gas inside, a vibrating plate configured to vibrate to discharge the gas in a pulsating flow through the opening, a supporting member that is attached to the chassis and is configured to support the vibrating plate in a manner such that the vibrating plate is vibratable, and a driving mechanism that is configured to drive the vibrating plate and includes a magnetic circuit member attached to the chassis and a voice coil body attached to the vibrating plate. The voice coil body is configured to prevent the voice coil body from contacting the magnetic circuit member when the vibrating plate is vibrating and is attached to the vibrating plate in a manner such that the voice coil body is movable by means of a magnetic field generated by the magnetic circuit member.
An electronic apparatus according to an embodiment of the present invention includes a heat-generating body, a frame, a chassis that has an opening and that is configured to support the frame and accommodate gas inside, a vibrating plate configured to vibrate to discharge the gas in a pulsating flow through the opening toward the heat-generating body, a supporting member that is attached to the frame and that is configured to support the vibrating plate in a manner such that the vibrating plate is vibratable, and a driving mechanism configured to drive the vibrating plate and includes a magnetic circuit member attached to the frame and a voice coil body attached to the vibrating plate. The voice coil body is configured to prevent the voice coil body from contacting the magnetic circuit member when the vibrating plate is vibrating and is attached to the vibrating plate in a manner such that the voice coil body is movable by means of a magnetic field generated by the magnetic circuit member.
An electronic apparatus according to another embodiment of the present invention includes a heat-generating body, a chassis that has an opening and that accommodates gas inside, a vibrating plate configured to vibrate to discharge the gas in a pulsating flow through the opening toward the heat-generating body, a supporting member that is attached to the chassis and that is configured to support the vibrating plate in a manner such that the vibrating plate is vibratable, and a driving mechanism that is configured to drive the vibrating plate and that includes a magnetic circuit member attached to the chassis and a voice coil body attached to the vibrating plate. The voice coil body is configured to prevent the voice coil body from contacting the magnetic circuit member when the vibrating plate is vibrating and is attached to the vibrating plate in a manner such that the voice coil body is movable by means of a magnetic field generated by the magnetic circuit member.
The electronic apparatus may be a computer, such as a laptop PC or a desk top PC, a personal digital assistance (PDA), an electronic dictionary, a camera, a display apparatus, an audio/visual apparatus, a mobile phone, a game apparatus, a car navigation apparatus, a robot, or any other electrical appliance. The heat-generating body may be an electronic component, such as an IC or a resistor, or a heat-radiating fin (heat sink). However, the heat-generating body is not limited thereto and may be any type of device that generates heat.
As described above, according to an embodiment of the present invention, generation of noise can be suppressed without reducing the gas discharge amount.
Embodiments of the present invention will be described below with reference to the drawings.
A jet flow generating apparatus 10 includes a chassis 1 whose rear part is rounded and a vibrating device 15 disposed inside the chassis 1. On a front surface la of the chassis 1, rows of nozzles 2a and 2b are provided. As shown in
The vibrating device 15 has a structure similar, for example, to a speaker. The vibrating device 15 includes a frame 4, an actuator 5 that is mounted on the frame 4 and functions as a driving mechanism, and a vibrating plate 3 that is attached to the frame 4 by an elastic supporting member 6. The frame 4 has a circulation port 4a for allowing the air inside the chassis 1 to flow in and out of the frame 4. The circulation port 4a may include plurality of ports or may be at least one elongated hole.
The vibrating plate 3 is composed of, for example, resin, paper, or metal. If the vibrating plate 3 is composed of paper, the weight of the vibrating plate 3 can be significantly reduced. Paper cannot be shaped as freely as resin. However, paper is advantageous in reducing the weight of the apparatus. If the vibrating plate 3 is composed of resin, the vibrating plate 3 can be molded into any desired shape. If the vibrating plate 3 is composed of metal, some types of metal, such as magnesium, are light and can be molded by injection. Therefore, a desirable metal can be selected to compose the vibrating plate 3.
The flat yoke 18 is, for example, disk-shaped, as mentioned above. However, the shape of the flat yoke 18 is not limited and may instead by oval or rectangular. The cylindrical yoke 8 is, for example, cylindrical, as mentioned above. However, the cylindrical yoke 8 may instead be a prism. It may be desirable to provide the cylindrical yoke 8 and the flat yoke 18 so that the cross-sectional shapes of the surfaces of the cylindrical yoke 8 and the flat yoke 18 taken along a direction orthogonal to the vibration direction S are the same as that of the opposing surface of the vibrating plate 3.
The chassis 1 is composed of, for example, resin, rubber, or metal. Resin and rubber are suitable for mass-production since they can be easily molded. If the chassis 1 is composed of resin or rubber, noise generated when the actuator 5 is driven and wind noise generated by the vibration of the vibrating plate 3 can be suppressed. By composing the chassis 1 with resin or rubber, the sound damping rate is improved and noise can be suppressed. Moreover, by composing the chassis 1 with resin or rubber, the weight and production cost of the chassis 1 can be reduced. If the chassis 1 is composed of resin by injection molding, the nozzles 2a and 2b can be formed as a single unit with the chassis 1. If the chassis 1 is composed of a material having high heat conductivity, such as metal, heat generated at the actuator 5 can be transmitted to the chassis 1 and then dispersed outside of the chassis 1. The metal may be aluminum or copper. When heat conductivity is taken into consideration, not only metal but also carbon is suitable. It is also possible to use magnesium, which is a metal that can be molded by injection. If the magnetic field generated by the magnetic circuit of the actuator 5 affects other devices in the apparatus, a measure must be taken to prevent leakage of the magnetic field. As one measure, the chassis 1 may be composed of a magnetic material, such as iron. In this way, leakage of the magnetic field can be significantly reduced. If the apparatus is to be used in a high-temperature environment or under special conditions, the chassis 1 may be composed of ceramic.
As described above, when the chassis 1 is composed of a material having high heat conductivity so as to enable heat dispersion, it is desirable to also compose the frame 4 of a material having high heat conductivity. In such a case also, the frame 4 is composed of metal or carbon. However, when heat conductivity is not taken into consideration, the frame 4 may be composed of, for example, resin. If resin is used, a light-weight frame can be composed by injection molding at low production costs. Part of the frame 4 may be composed of a magnetic material. The same magnetic material may be used to compose the yokes of the actuator 5 to increase the magnetic flux density.
The elastic supporting member 6 is composed of, for example, rubber or resin. The elastic supporting member 6 has a bellows-like structure and is circular when viewed from the top. The vibrating plate 3 is mainly supported by the actuator 5. However, the elastic supporting member 6 also supports the vibrating plate 3 to prevent horizontal vibration, i.e., vibration in the direction orthogonal to the vibration direction S of the vibrating plate 3. As described above, the elastic supporting member 6 separates the upper chamber 11a and the lower chamber 11b and prevents air from flowing between the upper chamber 11a and the lower chamber 11b when the vibrating plate 3 vibrates. It is desirable that the bellows-like elastic supporting member 6 has one mountain fold and one valley fold, as shown in
However, the structure of the elastic supporting member 6 is not limited to that shown in
In the above-described structure, the nozzles 2a and 2b are provided on the chassis 1. However, instead, a single opening may be formed on the chassis 1.
The operation of the jet flow generating apparatus 10 having the above-described structure will be described below.
When, for example, a sinusoidal alternating current voltage is applied to the actuator 5, the vibrating plate 3 vibrates in a sinusoidal pattern. As a result, the volumes of the upper chamber 11a and the lower chamber 11b change. As the volumes of the upper chamber 11a and the lower chamber 11b change, the pressure of the upper chamber 11a and the lower chamber 11b change. As a result, a pulsating flow of air is generated through the nozzles 2a and 2b. For example, when the vibrating plate 3 is displaced in a direction that causes the volume of the upper chamber 11a to be increased, the pressure in the upper chamber 11a decreases, whereas the pressure in the lower chamber 11b increases. In this way, air outside the chassis 1 flows into the upper chamber 11a through the nozzles 2a, whereas the air in the lower chamber 11b is discharged to the outside through the nozzles 2b. In contrast, when the vibrating plate 3 is displaced in a direction that causes the volume of the upper chamber 11a to be decreased, the pressure in the upper chamber 11a increases, whereas the pressure in the lower chamber 11b decreases. In this way, the air in the lower chamber 11a is discharged to the outside through the nozzles 2a, whereas air outside the chassis 1 flows into the upper chamber 11b through the nozzles 2b. When air is discharged from the nozzles 2a and 2b, the air pressure in the area near the nozzles 2a and 2b is reduced. As a result, air in the area near the nozzles 2a and 2b is sucked into the nozzles 2a and 2b. This generates a combined jet flow. By discharging this combined jet flow toward a heat-generating body and high-temperature areas, the heat-generating body and the high-temperature areas are cooled.
When air is discharged from the nozzles 2a and 2b, noise is generated from each of the nozzles 2a and 2b. However, the noise is damped since the sound wave of the noise generated at the nozzles 2a and the sound wave of the noise generated at the nozzles 2b have inverse phases. As a result, noise is reduced, and a quiet apparatus can be provided.
Next, the operation of the vibrating device 15 in the jet flow generating apparatus 10 or 20 will be described. Before describing the operation, prevention means for horizontal vibration of a vibrating plate will be described with reference to
As shown in
A vibrating device 35 shown in
Since the vibrating devices 25 and 35 are capable of preventing horizontal vibration, they are advantageous in that noise generated by tilting of the voice coil body 19 due to horizontal vibration, as shown in
For example, if a jet flow generating apparatus is mounted on a portable electronic apparatus, such as a laptop PC, the jet flow generating apparatus is expected to be substantially the same size as a known axial fan in order to obtain a predetermined air discharge amount. As shown in the drawings, such as
A speaker that includes a vibrating plate that has an amplitude of 4 mm is a low-range to mid-range woofer speaker. To obtain such a large amplitude, two elastic supporting members 6 are disposed far apart from each other, as shown in
Although the vibrating device 15 included in the above-described jet flow generating apparatus 10 or 20 includes only one elastic supporting member 6, the resistive force applied to the vibrating plate 3 is reduced while horizontal vibration is significantly reduced by means of the structure described below. In this way, the voice coil body 19 is prevented from coming into contact with the magnetic circuit members. The structure is described in detail below.
a point O is the center of the vibrating plate 3 in the horizontal direction of the drawing;
G [mm] represents the width of a space between the cylindrical yoke 8 and the magnet 14 (which is equivalent to a magnetic gap, as described below);
t [mm] represents the thickness of the voice coil body 19 in the space;
r [mm] represents the distance from the center O of the vibrating plate 3 to the vertical wall of the voice coil body 19;
R [mm] represents the sum of the distance from the center O of the vibrating plate 3 to the peripheral edge and half the distance from the peripheral edge to the frame 4 (i.e., the distance from the center O to a point P);
d [mm] represents the distance in the vibration direction S between a position [2] of the elastic supporting member 6 supporting the peripheral edge of the vibrating plate 3 (i.e., second position) to a position [3] of an tip 19a of the voice coil body 19 (i.e., third position);
the point P is the position on the elastic supporting member 6 half way between the distance from the peripheral edge of the vibrating plate 3 to the frame 4;
X [mm] represents the displacement of the point P in the vibration direction S (i.e., the original vibration direction) when the vibrating plate 3 is tilted (refer to
Y [mm] represents the displacement of the tip 19a of the voice coil body 19 in the direction orthogonal to the vibration direction S when the displacement of the point P equals X (refer to
The thickness t is the sum of the thicknesses of the coil bobbin 9 and the coil 17 wound around the coil bobbin 9. For the configurations shown in
When the point P is displaced by X, the rotation of the vibrating plate 3 is substantially centered on the point O. As shown in
Y˜(d·X)/R (1)
Since the displacement Y is extremely small, the displacement depending on r (for example, the upward displacement of the tip 19a of the voice coil body 19 in the drawing caused by the rotation of the vibrating plate 3 due to tilting, as shown in
A margin m for the voice coil body 19 in the space G can be represented by the following formula:
m=(G−t)/2 (2)
where, m represents a margin on one side of the voice coil body 19. Here, it is assumed that the space G distributed equally on each side of the voice coil body 19. Depending on the design, either the inner margin or the outer margin may be larger than the other. In any way, if the displacement Y of the tip 19a of the voice coil body 19 exceeds the margin m, the tip 19a comes into contact with the magnetic circuit members. For the tip 19a to not contact the magnetic circuit members, the following relationship must hold:
Y<m (3)
Therefore, from Formulas 1, 2, and 3, the following relationship holds:
[(d·X)/R]<[(G−t)/2] (4)
In other words, for the tip 19a to not contact the magnetic circuit members, the distant d should satisfy the following:
d<[(G−t)R]/(2X) (5)
According to Formula 5, the smaller the distance d from the second position [2] at a support surface where the vibrating plate 3 is supported by the elastic supporting member 6 to the tip 19a, the less likely the voice coil body 19 comes into contact with the magnetic circuit members. If the displacement X is about 0.5 mm, which is a realistic value, the distance d will satisfy the following relationship:
d<(G−t)R (6)
The displacement X will be about 0.5 mm when the length R is in the range of 10 to 40 mm or 15 to 35 mm.
Here, the distance d was calculated from the dimensions of a vibrating device actually produced by the inventor. The dimensions of the vibrating device produced by the inventor were G=0.94 mm, t=0.35 mm, R=22 mm, and r=8 mm, and d=13 mm. By setting the distance d below 13 mm in an actuator produced by the inventor, noise caused by the voice coil body 19 coming into contact with the magnetic circuit members was prevented even when only one elastic supporting member 6 was provided. According to an experiment, noise was reliably reduced and the quietness of the apparatus was improved. The distance d may be in the range of 0 to 20 mm or, more desirably, 0 to 10 mm when the length R is in the range of 10 to 40 mm.
These values depend on the dimensions and margins of the components of the vibrating device 15. However, when the vibrating device 15 is to be used in a laptop PC, as mentioned above, it is desirable for the distance d to be 20 mm or less or, more desirably, 10 mm or less.
As described above, according to this embodiment, the voice coil body 19 can be prevented from coming into contact with the magnetic circuit members while the vibrating plate 3 is vibrating by setting the distance d to a suitable value. In this way, noise can be suppressed while maintaining a predetermined air discharge amount without reducing the frequency and amplitude of the vibrating plate 3. In other words, according to this embodiment, as described above, noise caused by horizontal vibration can be prevented while maintaining an amplitude similar to a woofer speaker although the diameter of the vibrating plate 3 is relatively small.
Moreover, since only one elastic supporting member 6 is required, electric power consumption is low, the structure is simple, and weight is reduced. Furthermore, the durability of the actuator 5 is increased since the voice coil body 19 and the magnetic circuit members do not come into contact.
In the above, the length R is in the range of 10 to 40 mm but is not limited thereto. As a small electronic apparatus including the vibrating device 15 and the jet flow generating apparatus 10 according to this embodiment, an audio player including a flash memory and a hard disk or an IC voice recorder may be realized. As a large electronic apparatus including the vibrating device 15 and the jet flow generating apparatus 10 according to this embodiment, a 20-inch display device, 30-inch display device, or a display device larger 50 inches may be realized. Accordingly, the length R may be in the range of 5 to 100 mm. When the length R is greater than 40 mm, it is desirable to drive the vibrating plate 3 with an amplitude greater than 4 mmp-p, as described above.
Accordingly, as shown in
In the following descriptions, a position where a coil bobbin 9 is mounted on a vibrating plate 3 is defined as a fourth position [4]. In the following, the fourth position [4] is further away from a magnet 24 than a second position [2]. However, for the vibrating devices shown in FIGS. 8 and 11, the fourth position [4] is closer to the magnet 14 than the second position [2].
A plate-shaped yoke 38 that is disposed on the magnet 24 of the vibrating device 75 has a diameter greater than that of the magnet 24. A yoke 28 for accommodating the magnet 24 is, for example, cylindrical and, as shown in
As shown in
d′<[(G−t)R]/(2X) (7)
In general, it is easy to design the vibrating device 75 so that the distance d′ is smaller than the distance d. According to such a design, the displacement of the voice coil body 19 is small, but the margin for the tilt is great. Similar to Formula 6, when a realistic value is assigned to the displacement X, the following relationship holds for the distance d′:
d′<(G−t)R (8)
In order to easily compare
The distance d′ is in the range of 0 to 10 mm or, more desirably, 0 to 5 mm when the length R is in the range of 10 to 40 mm.
To increase the margin for the tilting of the vibrating plate 23 in the vibrating device 75, which has the structure shown in
θ=tan −1(X/R) (9)
As shown in
Y=r(1−cos θ) (10)
The structures shown in
Here, similar to the above, if G=0.94 mm, t=0.35 mm, R=22 mm, and r=8 mm, from Formulas 9 and 19, θ=1.3° and Y=2 μm. In other words, although the displacement of the voice coil body 19 at the magnetic gap can be substantially ignored, the vibrating device 85 has a structure that can reliably compensate for tilting. Accordingly, the magnetic gap G can be narrowed. As a result, the magnetic efficiency is improved, and the vibrating device 85 can be magnetically driven efficiently. Consequently, energy consumption is reduced.
A cylindrical yoke 48 is fixed on the chassis 31. A frame having the same structure as that of the frame 4 (refer to
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2005-130309 | Apr 2005 | JP | national |
