WO2008004729A1

WO2008004729A1 - Vibrator

Info

Publication number: WO2008004729A1
Application number: PCT/KR2006/005562
Authority: WO
Inventors: Yun Gyu Kang
Original assignee: Yea Il Electronics Co., Ltd.
Priority date: 2006-07-07
Filing date: 2006-12-19
Publication date: 2008-01-10

Abstract

A vibrator for improving vibration force through double oscillation of an oscillator and increasing vibration transfer efficiency through the concentration of vibration force on a case. The vibrator, in response to an electrical signal applied thereto, vibrates according to variation in the magnetic force of a coil and the resultant interaction of attraction and repulsion between the coil and a magnet, and includes: a first motion unit supporting either the coil or the magnet, oscillating through the interaction therebetween; and a second motion unit supporting the first motion unit in such a fashion that the first motion unit repetitively moves up and down. The second motion unit is repetitively moved up and down by the motion force from the first motion unit. The motion force is transferred to the second motion unit, thus causing repetitive up/down motion of the second motion unit.

Description

VIBRATOR

Technical Field

[1] The present invention relates to a vibrator and, more particularly, to a vibrator which, in response to an electric signal applied thereto, vibrates according to variation in the magnetic force of a coil and the resultant interaction of attraction and repulsion between the coil and a magnet. Background Art

[2] Typically, portable mobile communication terminals such as a mobile phone (a cellular phone and a Personal Communication Systems (PCS) phone), a Personal Digital Assistant (PDA), notebooks and others have an electronic acoustic transducer installed therein in order to be able to output sound.

[3] The electronic acoustic transducer is in general classified into a device capable of outputting voices and sounds, such as a speaker, a receiver, a buzzer and others, and a vibrator outputting stereo sound by generating them using a vibration force.

[4] The vibrator is typically divided into a motor-driven type that generates vibrations using the centrifugal force of a rotating pin eccentrically fixed to the rotating shaft of a motor, and a solenoid type that generates vibrations using an oscillator linearly moving in a coil that generates magnetic force when an electric signal (power source) is applied thereto.

[5] For reference, a solenoid has the literal meaning of "a cylindrical coil of wire", which is called a solenoid coil, and means a transducer that transforms electrical energy into mechanical energy using magnetic force generated in an air gap.

[6] The solenoid generally includes a magnetic circuit constituted by a metallic oscillator moving around a coil in response to magnetic force, a surrounding case, and a magnetic material corresponding to a core in the coil, whereby, in response to current applied to the coil, magnetic flux flows in the magnetic circuit surrounding the coil, which produces a magnetic force in the oscillator to thus operate the solenoid.

[7] Compared to the motor-driven type vibrator, the vibrator using such a solenoid has advantages in that the consumption of vibration energy is low, and upon the application of an AC signal, mechanical resonance occurs due to the physical characteristics of the magnetic circuit and the oscillator at a specified frequency, so that the vibration force can be changed, that is, the magnitude of the vibration force can be regulated according to the resonant frequency. On the contrary, it also has problems in that constitutional elements are very complex, and thus the manufacturing cost is increased and productivity is decreased. [8] In the meantime, the motor-driven type vibrator, in particular, a coin type vibrator, obtains vibration force through eccentric rotating motion or linear reciprocating motion.

[9] However, in a coin type vibrator having such an eccentric rotating motion structure, it is impossible to obtain a great quantity of vibration force (because of the short lifetime due to the limited supply of lubrication oil between a bearing and a shaft), and also in the linear reciprocating motion structure, there is a problem in that there is an upper limit to vibration force due to the short moving distance.

[10] In addition, presently, the lifetime of the vibrator is restricted to about 50,000 hours, and when the eardrum of a user is exposed to the vibrator and a loud sound is emitted therefrom, hearing damage results, that is, the eardrum is often ruptured. Disclosure of Invention Technical Problem

[11] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a vibrator capable of increasing vibration force through double oscillation of an oscillator while increasing vibration transfer efficiency through the concentration of vibration force on a case. Technical Solution

[12] In order to accomplish the above object, there is provided a vibrator which, in response to an electric signal applied thereto, vibrates according to variation in the magnetic force of a coil and a resultant interaction of attraction and repulsion between the coil and a magnet. The vibrator includes: a first motion unit, supporting either one of the coil or the magnet, oscillating through the interaction therebetween; and a second motion unit supporting the first motion unit in such a fashion that the first motion unit repetitively moves up and down, the second motion unit repetitively moving up and down due to the motion force transferred from the first motion unit.

[13] In the invention, when the coil and the magnet are repelled from / attracted to each other by the variation in the magnetic force of the coil, the first motion unit, movably supporting either the coil or the magnet, starts repetitive up/down motion.

[14] Then, the motion force is transferred to the second motion unit, which supports the first motion unit, so that the second motion unit also starts repetitive up/down motion.

[15] Accordingly, the repetitive up/down motion force of the second motion unit is added to the repetitive up/down motion force of the first motion unit. Advantageous Effects

[16] In this way, the motion force is transferred to the second motion unit supporting the first motion unit so that the second motion unit also starts repetitive up/down motion. [17] Accordingly, the repetitive up/down motion force of the second motion unit is added to the repetitive up/down motion force of the first motion unit to thereby increase the vibration force. [18] Further, the present invention can makeaudible output and vibration output using a single structure, thereby considerably simplifying the constitutional elements and the structure of the multi-functional sound output device.

Brief Description of the Drawings [19] The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[20] FIG. 1 is an exploded perspective view of the construction of the present invention;

[21] FIG. 2 is a cross sectional view of the construction of the present invention;

[22] FIGS. 3 and 4 are cross sectional views illustrating operational positions of the present invention; [23] FIG. 5 is a cross sectional view illustrating another embodiment of the present invention; [24] FIG. 6 is a cross sectional view illustrating still another embodiment of the present invention; [25] FIG. 7 is a cross sectional view illustrating a further embodiment of the present invention; [26] FIG. 8 is a cross sectional view illustrating yet another embodiment of the present invention;

[27] FIG. 9 is a cross sectional view of FIG. 8;

[28] FIG. 10 is a cross sectional view illustrating a variation to the embodiment shown in

FIG. 8; [29] FIGS. 11, 12 and 13 are cross sectional views illustrating a still further embodiment of the present invention; and [30] FIGS. 14 and 15 are cross sectional views illustrating yet a further embodiment of the present invention.

Best Mode for Carrying Out the Invention [31] To supplement the detailed description of the present invention, there are provided drawings, in which FIG. 1 is an exploded perspective view of the construction of the present invention, FIG. 2 is a cross sectional view of the construction of the present invention, FIGS. 3 and 4 are cross sectional views illustrating operational positions of the present invention, FIG. 5 is a cross sectional view illustrating another embodiment of the present invention, FIG. 6 is a cross sectional view illustrating still another embodiment of the present invention, FIG. 7 is a cross sectional view illustrating a further embodiment of the present invention, FlG. 8 is a cross sectional view illustrating yet another embodiment of the present invention, FlG. 9 is a cross sectional view of FlG. 8, FlG. 10 is a cross sectional view illustrating a variation to the embodiment shown in FlG. 8, FIGS. 11, 12 and 13 are cross sectional views illustrating a still further embodiment of the present invention, and FIGS. 14 and 15 are cross sectional views illustrating yet a further embodiment of the present invention, wherein a reference numeral 11 denotes a first motion unit, a reference numeral 12 denotes a second motion unit, a reference numeral 12a denotes a resilient frame, a reference numeral 13 denotes a support member, and a reference numeral 13a denotes a supporting slant portion.

[32] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[33] Referring first to FIGS. 1 and 2, the vibrator 10 of this embodiment, in response to an electric signal applied thereto, vibrates according to variation in the magnetic force of a coil C and the resultant interaction of attraction and repulsion between the coil C and a magnet M. The vibrator 10 also includes a first motion unit 11 supporting either the coil C or the magnet M, oscillating through interaction therebetween, and a second motion unit 12 supporting the first motion unit 11 in such a fashion that the first motion unit 11 can repetitively move up and down. The second motion unit 12 also repetitively moves up and down through the motion force from the first motion unit 11.

[34] Herein, the coil C may be an annular voice coil, for example, fixed to a case 1 of the vibrator 10.

[35] Here, the end portion of the coil C is connected to an external electric signal source by being soldered thereto, or is connected in the form of a contact through a terminal to a printed circuit board (PCB) provided on the case 1.

[36] The case may be a main body Ia or a cover Ib.

[37] Meanwhile, the magnet M consists of magnets 1 and 2 (Ml and M2) which are concentric and have different diameters. Herein, it is preferable that the magnets be separated to form an air gap therebetween.

[38] As constructed above, the magnetic force applied to the coil C is increased to improve the vibration force considerably.

[39] In addition, the magnet M may be, for example, a single magnet.

[40] In such a vibrator, although the vibration force thereof may be reduced, the diameter thereof can also be reduced such that it can be used as a compact type device, such as a bone conduction transducer. In addition, a top plate T is seated on the magnet M to concentrate the magnetic force thereon.

[41] Herein, in the case where the magnet M consists of the magnets 1 and 2 (Ml and

M2), top plates 1 and 2 (Tl and T2) are preferably seated on the respective magnets. [42] The first motion unit 11 may be a yoke, a leaf spring with low elastic modulus, or a synthetic resinous oscillator, for example.

[43] In the case where the first motion unit 11 is a yoke or a leaf spring, the magnet M is preferably seated thereon, and in case of the synthetic resinous oscillator, the coil is preferably seated thereon.

[44] Herein, the first motion unit 11 may be perforated at its center portion, or may be curved in one direction and perforated at its center portion.

[45] The first motion unit 11 supports the magnet M or the coil C. However, it is preferable that the first motion unit supports the magnet M thereon in view of the correlation between weight and vibration force since the magnet M exhibits excellent vibration force.

[46] Further, the second motion unit 12 may be a leaf spring having a high elastic modulus, for example, surrounding the first motion unit 11, from one surface to the circumference thereof.

[47] At this time, the second motion unit 12 is fixed at its center portion to the case 1, and protrudes at its outer peripheral portion in one direction, wherein the center portion and the outer peripheral portion may be connected by at least three elastic frames 12a, each being curved in a circular shape.

[48] The elastic frame 12a is made shorter to improve its lower frequency characteristics.

[49] In addition, the outer peripheral portion of the second motion unit 12 has an end portion bent inward so that it catches the first motion unit 11 or the magnet M including the same.

[50] Herein, the outer peripheral portion of the second motion unit 12, which is bent inwards, surrounds the upper surface of the top plate T seated on the magnet M in such a fashion that it is flush with the top plate T through making the top plate stepped in the same thickness as that of the second motion unit 12, or otherwise may fixedly surround the upper surface of the top plate T without forming the step.

[51] In addition, a support member 13 may be provided between the first motion unit 11 and the second motion unit 12 to secure the range of downward repetitive motion of the first motion unit 11.

[52] Herein, the support member 13 may be a ring supporting the lower portion of the outer peripheral portion of the first motion unit 11 with respect to the second motion unit 12, a protruding step formed on the lower surface of the outer peripheral portion of the first motion unit 11, or a protruding step formed on an inner peripheral portion of the second motion unit 12.

[53] In addition, the second motion unit 12 may be fixed at its outer peripheral portion to the inner peripheral portion of the main body Ia through impregnation injection molding, or may be supported and fixed thereto by the insertion of a ring into both surfaces of the outer peripheral portion.

[54] In addition, to secure a range of downward repetitive motion of the first motion unit

11 with respect to the second motion unit 12, a supporting slant portion 13a may be formed so as to have an inclined surface except for the surface of the first motion unit

11 which contacts the second motion unit 12.

[55] As constructed above, in the supporting slant portion 13a of the first motion unit 11, a vertex portion coming into contact with the second motion unit 12 supports the first motion unit 11 with respect to the second motion unit 12 like the support member 13, to thereby secure the range of downward repetitive motion. [56] As a result, it is possible for the first motion unit 11 to support itself with respect to the second motion unit 12 without a separate support member 13. [57] Furthermore, the main body Ia of the case 1 is provided at its center portion with a step Ic that protrudes upward and has a perforated center. [58] In addition, in conformity with the hole formed on the step of the main body Ia, a rod type shaft Id having a recess at its end portion may be formed in the center portion on one surface of the cover Ib of the case 1. [59] As constructed above, the recessed portion of the shaft Id formed at the center portion on one surface of the cover Ib enables press-fitting of the second motion unit

12 into the step Ic of the main body Ia, and the leading end thereof passes through the center portion of the second motion unit 12 and the hole of the step Ic of the main body Ia to be exposed outside. The end portion of the leading end is then fixed by pressing to thereby complete the casing between the cover Ib and the main body Ia.

[60] The operation of the present invention constructed above will now be explained.

[61] First, as shown in FIGS. 1 and 2, when an alternating current electrical (AC) signal is inputted to the coil C from outside, the coil C and the magnet M, i.e., the magnets 1 and 2 (Ml and M2), are repelled/attracted from/to each other by the variation in magnet force.

[62] In this case, as shown in FIGS. 3 and 4, the coil C fixed to the cover Ib is in a fixed state, and the magnets 1 and 2 Ml and M2 supported by the first motion unit 11 repetitively move up and down.

[63] Then, the first motion unit 11 supporting the magnets 1 and 2 (Ml and M2) also starts to repetitively move up and down. At this time, the motion of the first motion unit is the repetitive up/down motion of linearly reciprocating up and down.

[64] Then, the motion force is transferred to the second motion unit 12, which supports the first motion unit 11, so that the second motion unit 12 also starts to repetitively move up and down while being supported at the center thereof on the main body Ia, to thereby transfer vibration force to the case 1. Herein, the motion of the second motion unit 12 is the repetitive up/down motion of oscillating motion.

[65] Due to this construction, vibration force is improved through the addition of the repetitive up/down motion of the second motion unit 12 to the repetitive up/down motion of the first motion unit 11.

[66] This is also adapted to the embodiment as shown in FIGS. 4 and 5.

[67] The embodiment shown in FlG. 5 is a structure in which the outer peripheral portion of the second motion unit 12, which is bent inward, fixedly surrounds a portion of the upper surface of the top plate T seated on the magnet M.

[68] In addition, the embodiment shown in FlG. 6 is a structure in which a separate fixing member 12 passes through the center portion of the second motion unit 12, and is exposed and riveted to the outside of the hole of the step Ic of the main body Ia.

[69] Furthermore, as shown in FlG. 7, it can adopt a structure in which the outer peripheral portion of the second motion unit 12 is impregnated into and fixed to the main body Ia, and the first motion unit 11, the magnet M, and the top plate T are in contact with the outer peripheral surface of the inner annular step 12b of the second motion unit 12, and are fixed together by bending the end of the annular step.

[70] In addition, as shown in FlG. 8, to secure the range of downward repetitive motion of the first motion unit 11 with respect to the second motion unit 12, the supporting slant portion 13a may be formed to have an inclined surface except the surface of the first motion unit 11 that is in contact with the second motion unit 12.

[71] Herein, as shown in FlG. 9, the first motion unit 11 may consist of a yoke only, and, as shown in FlG. 10, a weight 15 made of nonconductive tungsten may be further adhered to the surface of the first motion unit opposite the coil C of the yoke.

[72] In addition, it may be constructed such that the magnet M and the top plate T seated on the first motion unit 11 are one in number, respectively, and the number of windings of the coil C is increased.

[73] In this construction, in the supporting slant portion 13a of the first motion unit 11, a vertex portion, which comes into contact with the second motion unit 12, supports the first motion unit 11 with respect to the second motion unit 12, like the support member 13, to thereby secure the range of downward repetitive motion. As a result, it is possible for the first motion unit 11 to support itself with respect to the second motion unit 12 without requiring the support member 13.

[74] In addition, in the case where the weight 15 made of tungsten is further adhered to the yoke of the first motion unit 11, the weight increases the weight of the first motion unit 11 to improve the vibration force.

[75] The invention as constructed above can be used as a bone conduction speaker that transfers sounds through bone conduction and a linear vibrator, and can be adapted to a headset for MP3s or as a receiver of a cellular phone. [76] Conventionally, the bone conduction speaker had a structure that transfers sounds through vibrating air through oscillation of an oscillating plate, and current consumption of about 50[mA] at 2V. However, the present invention has a structure that transfers sounds through vibration in the first and second motion units 11 and 12 of an oscillator, not in the oscillating plate, and current consumption of about 23 [mA]. Thus, the same output can be obtained even with low current consumption, so that it is possible to considerably reduce the consumption of a battery. Herein, the voltage and the current are merely exemplary ones, which may be changed and adapted according to specifications of products.

[77] In particular, in the case of the conventional multi-functional sound output device equipped with a sound output section and a vibration output section to thereby output sounds and vibration, the present invention can output the audible output and the vibrating output using a single structure, thereby considerably simplifying the constitutional elements and the structure of the multi-functional sound output device.

[78] In addition, according to the present invention, there can be provided a separate magnetic body M3 at an inner surface or an outer surface, or inner and outer surfaces of the coil C fixed to the cover Ib, as shown in FIGS. 11, 12 and 13.

[79] Herein, the magnetic body may be a magnet, which may be adhesively fixed to or impregnated and fixed to the cover Ib to which the coil C is fixed.

[80] As constructed above, before the alternating signal is input to the coil C, an attraction force is applied to the magnets 1 and 2 Ml and M2, the top plates 1 and 2 Tl and T2, and the yoke through the interaction of magnetic forces therebetween, and when the alternating signal is input to the coil C, the input signal is added to the magnetic force of the magnetic body M3 itself to thereby further enhance the vibration force.

[81] In addition, as shown in FIGS. 14 and 15, a buffer pad Pl or P2 may be provided to the cover Ib or the top plate T to reduce the impact force produced during the up/down motion of the first motion unit 11 when the upper surface of the top plate T comes into contact with the cover Ib.

[82] Herein, the buffer pad Pl provided on the cover Ib may be adhered and fixed to the center portion of the cover Ib where the shaft Id is formed, and the buffer pad P2 provided on the upper surface of the top plate T may be adhered and fixed to the center portion or the outer peripheral portion, or the center portion and the outer peripheral portion of the top plate T.

[83] In this case, it is possible to minimize the generation of impact sounds, i.e., noise, when the top plate T and the cover Ib are brought into contact with each other by a strong vibration force.

[84] Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[85] As set forth before, according to the present invention, when a coil and a magnet are repelled from / attracted to each other by the variation in magnetic force of the coil, a first motion unit movably supporting either the coil or the magnet starts repetitive up/ down motion.

Industrial Applicability

[86] In this way, the motion force is transferred to the second motion unit supporting the first motion unit so that the second motion unit also starts repetitive up/down motion. [87] Accordingly, the repetitive up/down motion force of the second motion unit is added to the repetitive up/down motion force of the first motion unit to thereby increase the vibration force. [88] Further, the present invention can makeaudible output and vibration output using a single structure, thereby considerably simplifying the constitutional elements and the structure of the multi-functional sound output device.

Claims

[I] A vibrator 10 which, in response to an electric signal applied thereto, vibrates according to variation in a magnetic force of a coil C and a resultant interaction of attraction and repulsion between the coil C and a magnet M, the vibrator 10 comprising: a first motion unit 11 supporting either one of the coil C and the magnet M, which oscillate due to an interaction therebetween; and a second motion unit 12 supporting the first motion unit 11 in such a fashion that the first motion unit 11 can repetitively move up and down, the second motion unit 12 repetitively moving up and down due to the motion force from the first motion unit 11. [2] The vibrator as claimed in claim 1, wherein the coil C is an annular voice coil fixed to the center portion of the case 1 of the vibrator 10. [3] The vibrator as claimed in claim 2, wherein the case 1 comprises a main body Ia and a cover Ib. [4] The vibrator as claimed in claim 1, wherein the magnet M comprises annular magnets 1 and 2 (Ml and M2), concentrically arranged and having different diameters. [5] The vibrator as claimed in claim 4, wherein the magnets 1 and 2 (Ml and M2) are separated from each other to form an air gap therebetween. [6] The vibrator as claimed in claim 1, wherein a top plate T is seated on the magnet

M. [7] The vibrator as claimed in claim 4, wherein top plates 1 and 2 (Tl and T2) are seated on upper surfaces of the magnets 1 and 2 (Ml and M2). [8] The vibrator as claimed in claim 7, wherein the magnet 1 (Ml) is provided with a step in an outer peripheral portion of an upper surface thereof.

[9] The vibrator as claimed in claim 1, wherein the first motion unit 11 is a yoke.

[10] The vibrator as claimed in claim 1, wherein the first motion unit 11 is a leaf spring having a low elastic modulus.

[II] The vibrator as claimed in claim 1, wherein the first motion unit 11 is an oscillating plate made of a synthetic resin.

[12] The vibrator as claimed in any one of claims 1, 9, and 10, wherein the magnet M is seated on the first motion unit 11. [13] The vibrator as claimed in any one of claims 1 to 11, wherein the coil is seated on the first motion unit 11. [14] The vibrator as claimed in claim 1, wherein the first motion unit 11 is perforated in a center portion thereof. [15] The vibrator as claimed in claim 1, wherein the first motion unit 11 is perforated in a center portion thereof so as to be bent in one direction. [16] The vibrator as claimed in claim 1, wherein the second motion unit 12 comprises a leaf spring that has a high elastic modulus and surrounds the first motion unit

11 from a surface portion to an outer peripheral surface thereof. [17] The vibrator as claimed in claim 1, wherein the second motion unit 12 is fixed at a center portion thereof to the case 1, and the outer peripheral portion thereof protrudes in one direction, the center portion and the outer peripheral portion being connected with each other by at least three elastic frames 12a, each forming a curve in a circular shape. [18] The vibrator as claimed in claim 1, wherein an end portion of the outer peripheral portion of the second motion unit 12 is bent inward to catch the first motion unit

11, seated thereon, or to catch the magnet M, which includes the first motion unit

11. [19] The vibrator as claimed in claim 1, wherein a support member 13 is provided between the second motion unit 12 and the first motion unit 11 to secure a range of downward repetitive motion of the first motion unit 11. [20] The vibrator as claimed in claim 19, wherein the support member 13 is a ring supporting the lower portion of the outer peripheral portion of the first motion unit 11 with respect to the second motion unit 12. [21] The vibrator as claimed in claim 19, wherein the support member 13 is a projection step formed at the lower surface of the outer peripheral portion of the first motion unit 11. [22] The vibrator as claimed in claim 19, wherein the support member 13 is a projection step formed on an inner peripheral surface of the second motion unit

12. [23] The vibrator as claimed in claim 1, wherein an outer peripheral portion of the second motion unit 12 is impregnated into an inner peripheral surface of a main body Ia and is injection-molded. [24] The vibrator as claimed in claim 3, wherein the case 1 is provided at a center portion of the main body Ia thereof with a step Ic protruding upward and having a center hole. [25] The vibrator as claimed in claim 3 or 24, wherein the case 1 is provided at a center portion on one surface of the cover Ib thereof with a rod type shaft Id having a recess formed in an end portion thereof, the shaft corresponding to a center hole of the step Ic of the main body Ia. [26] The vibrator as claimed in claim 1, 3, or 24, wherein the cover Ib is provided at a center portion on one surface thereof with a recessed shaft Id, and a recessed portion of the shaft Id enables press-fitting of the second motion unit 12 to the step Ic of the main body Ia in such a manner that the leading end thereof passes through the center portion of the second motion unit 12 and a hole of the step Ic of the main body Ia so as to be exposed outside, and is then riveted by pressing the end portion of the leading end to thereby couple the cover Ib and the main body Ia together.

[27] The vibrator as claimed in claim 1, wherein a supporting slant portion 13a is formed at the lower surface of the first motion unit 11 contacting the second motion unit 12 to secure a range of downward repetitive motion of the first motion unit 11 with respect to the second motion unit 12.

[28] The vibrator as claimed in claim 27, wherein, in the supporting slant portion 13a of the first motion unit 11, a vertex portion of the lower surface coming into contact with the second motion unit 12 supports the first motion unit 11 with respect to the second motion unit 12.

[29] The vibrator as claimed in claim 9 or 27, wherein a weight 15 made of non- conductive tungsten is further adhered to a surface opposite the coil C of a yoke.

[30] The vibrator as claimed in claim 1, 2, or 3, wherein a separate magnetic body M3 is provided to an inner surface of the coil C fixed to the center portion of the cover Ib.