JP2008042324A - Vibration generator and speaker instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a vibration generator capable of obtaining strong exciting force even at a low-frequency range to be excited, and to provide a speaker instrument capable of increasing the sound pressure at the low-frequency range by using a vibration generator. <P>SOLUTION: An exciting force generator 60 for composing the speaker instrument 10 has an actuator 20 actuated for vibrating an output shaft 78 to a yoke 66 fixed to a diaphragm 18, and a weight 80 provided in the output shaft 78 of the actuator 20. The actuator 20 gives counterforce following the excitation of the weight 80 to the diaphragm 18 as compelling force. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vibration generator and a speaker device.

2. Description of the Related Art A flat speaker is known that uses a giant magnetostrictive element as a drive source to apply a forced displacement to a flat diaphragm and vibrates the diaphragm to generate sound waves (see, for example, Patent Document 1).
JP 2005-244804 A JP-A-11-143476

  However, since the giant magnetostrictive element has a small expansion / contraction amount, that is, a displacement amount of forced displacement, in order to secure sound pressure in a low frequency range, the size of the giant magnetostrictive element must be increased to ensure the excitation amplitude. There is room for improvement in this respect.

  In consideration of the above facts, the present invention is a vibration generator capable of obtaining a strong excitation force even in the low frequency range of the vibration target, and increasing the sound pressure in the low frequency range using the vibration generator. It is an object to obtain a speaker device that can be used.

  The vibration generating device according to the invention of claim 1 is operated to vibrate an actuator that vibrates an output unit with respect to a main body fixed to a vibration target, and a weight provided at the output unit of the actuator. I have.

  In the vibration generating device according to the first aspect, when the actuator is operated, the weight provided at the output portion of the actuator is vibrated. For this reason, the reaction force accompanying the vibration of the weight is input as the excitation force (forced force) to the excitation target to which the main body of the actuator is fixed. In other words, the vibration of the vibration target is forced vibration due to force. Since this excitation force can be increased in proportion to the acceleration of the weight, a large excitation force can be obtained even if the vibration frequency of the object to be excited is a low frequency.

  Thus, in the vibration generator according to the first aspect, a strong excitation force can be obtained even in the low frequency range of the excitation target.

  The vibration generator according to a second aspect of the present invention is the vibration generator according to the first aspect, wherein the actuator vibrates the output unit with respect to the main body by periodically changing the applied magnetic field. The magnetostrictive element is included.

  In the vibration generating apparatus according to the second aspect, the actuator vibrates the weight by the expansion and contraction of the magnetostrictive element accompanying the change of the applied magnetic field. Since the magnetostrictive element generates a large stress with respect to a change in magnetic field, a mass having a relatively large mass can be vibrated at a high speed, and a large exciting force acting on an object to be excited can be obtained along with the vibration of the mass. . As a result, the vibration amplitude of the vibration target can be reliably increased.

  A vibration generator according to a third aspect of the present invention is the vibration generator according to the second aspect, wherein the actuator generates a magnetic field that changes in a time shorter than a period of an output vibration to be generated in the vibration target. An excitation device for applying to the magnetostrictive element at a period of output vibration is included.

  According to another aspect of the vibration generating device of the present invention, the actuator exciting device generates a magnetic field fluctuation only once in one cycle of the output vibration to be generated in the vibration target. As a result, the weight repeatedly performs the movement driven at a large acceleration by a short-time magnetic field fluctuation at the frequency of the output vibration described above. Thus, since the weight moves with a large acceleration, the excitation force (reaction force of the movement of the weight) with the frequency of the output vibration input to the object to be excited increases. Thereby, the vibration amplitude of the vibration target can be further increased.

  A speaker device according to a fourth aspect of the present invention is the speaker device according to any one of the first to third aspects, wherein a flat diaphragm and the diaphragm are fixed to the body of the actuator as the vibration target. And a vibration generator.

  In the speaker device according to the fourth aspect, since the diaphragm can be vibrated with a large amplitude by using the vibration generating device described above, the sound pressure in the low frequency region of the generated sound wave can be increased.

  As described above, the vibration generator according to the present invention has an excellent effect that a strong excitation force can be obtained even in the low frequency range of the excitation target. In addition, the speaker device according to the present invention has an excellent effect that the sound pressure in the low frequency region can be increased by using the vibration generator.

  A speaker device 10 to which a vibration generator according to an embodiment of the present invention is applied will be described with reference to FIGS. First, the overall configuration of the speaker device 10 will be described, and then the excitation force generator 60 as a vibration generator in the present invention will be described in detail.

(Overall configuration of speaker device)
FIG. 5A shows a plan view of the speaker device 10, and FIG. 5B shows a side sectional view taken along line 5B-5B in FIG. 5A. FIG. 5C shows a bottom view of the speaker device 10. As shown in FIGS. 5A and 5B, the speaker device 10 includes a case 12. The case 12 includes a substantially rectangular flat bottom wall (bottom plate) 14 and a rectangular frame-shaped peripheral wall 16 erected from the periphery of the bottom wall 14 over the entire periphery. In this embodiment, the bottom wall 14 is formed in a substantially square shape, and the peripheral wall 16 is formed in a square frame shape. The open end of the case 12 is closed by a diaphragm 18 as a cover.

  Specifically, the diaphragm 18 is formed in a rectangular flat plate shape substantially corresponding to the bottom wall 14 in a front view, and a peripheral edge portion 18A of the peripheral wall 16 is an end opposite to the substantially rectangular flat plate shaped bottom wall 14. It is joined to the part. In this embodiment, the case 12 and the diaphragm 18 are each made of a metal material, and the peripheral edge portion 18A of the diaphragm 18 is an end portion 16A of the peripheral wall 16 (open end of the case 12) over the entire circumference. Are joined by welding. As the metal goods constituting the case 12 and the diaphragm 18, for example, stainless steel having good heat resistance is used.

  As described above, in the speaker device 10, the sealed space R surrounded by the bottom wall 14, the diaphragm 18, and the peripheral wall 16 that connects them is formed between the case 12 and the diaphragm 18. . In the sealed space R, an actuator 20 that constitutes a main part of the excitation force generator 60 according to the present invention is disposed. As will be described in detail later, the actuator 20 is attached to the diaphragm 18 and is actuated by receiving power from the power supply lead wire 20A to vibrate the diaphragm 18 in the thickness direction. The speaker device 10 is used for an application (for example, an exhaust sound active silencer 30 to be described later) that generates sound waves outward of the sealed space R by vibration of the diaphragm 18.

  As shown in FIGS. 5B and 5C, the diaphragm 18 is formed with a bead 26 as a rigidity changing portion. As shown in FIG. 5C, the bead 26 is formed in an annular shape that is substantially coaxial with the actuator 20 in front view, and surrounds the actuator 20 between the actuator 20 and the rectangular frame-shaped peripheral wall 16. Is located. Further, as shown in FIG. 5B, the bead 26 is formed in a corrugated plate (convex) shape curved in a sine wave shape in the plate thickness direction of the diaphragm 18 in a sectional view.

  Accordingly, the bead 26 is a low-rigidity portion (spring portion) in the diaphragm 18 and functions as a vibration blocking portion that makes it difficult to transmit a dynamic displacement or load input to the center portion of the diaphragm 18 to the peripheral portion 18A side. It is supposed to be. For this reason, the diaphragm 18 fixed to the end portion 16A of the peripheral wall 16 at the peripheral portion 18A causes the inner portion of the bead 26 to vibrate more than the outer portion (the peripheral portion 18A side portion) of the bead 26 by the operation of the actuator 20. It is configured to easily vibrate in the plate thickness direction of the plate 18 (prone to generate divided vibration).

  The bead 26 is sized and shaped according to the vibration mode required for the speaker device 10 (the split vibration mode of the diaphragm 18). That is, in the speaker device 10, the dimensions and shape of the bead 26 are determined so that the sound wave in the frequency band to be generated becomes the plane wave Wf shown in FIG. In this embodiment, the speaker device 10 applied to the exhaust sound active silencer 30 described later has the diaphragm 18 in the frequency band of the secondary rotational component of the internal combustion engine 32 (idle speed to maximum speed). A bead 26 is provided so that a plane wave Wf is output from the bead.

  The speaker device 10 includes a sound absorbing material 28 filled in the sealed space R. The sound absorbing material 28 is made of, for example, glass wool, and is filled in the sealed space R so as to absorb (attenuate) air vibration, that is, sound generated in the sealed space R accompanying the vibration of the diaphragm 18. It has become.

  Further, a rib 22 is formed on the bottom wall 14 of the case 12. As shown in FIG. 5A, the ribs 22 are orthogonal to the plurality of (three in this modification) vertical ribs 22A along the two opposite sides of the bottom wall 14 in plan view, and the vertical ribs 22A. A plurality of (three in this modified example) horizontal ribs 22B along the line intersect with each other in a lattice shape and protrude from the outer surface of the bottom wall. The rib 22 functions as a means for reinforcing (stiffening) the bottom wall 14 and the bending rigidity of the bottom wall 14 is increased.

(Detailed configuration of excitation force generator)
As shown in FIG. 1, the speaker device 10 includes an excitation force generator 60 as a vibration generator for vibrating the diaphragm 18 at a predetermined frequency. The excitation force generation unit 60 includes the actuator 20 and a weight 80 as a weight that is excited by the actuator 20 as main components.

  The actuator 20 includes a yoke 66 as a main body fixed to the diaphragm 18 via a bracket 64. The yoke 66 has a cylindrical wall portion 66A formed in a substantially cylindrical shape, a bottom plate 66B that faces one end in the axial direction of the cylindrical wall portion 66A, and the other end in the axial direction of the cylindrical wall portion 66A. And a top plate 66C. A through hole 66D is formed in the axial center portion of the top plate 66C. On the bottom plate 66B in the cylindrical wall portion 66A of the yoke 66, a disc-shaped magnet 68 for setting a magnetic bias described later is disposed.

  A magnetostrictive element (super magnetostrictive element) 70 is disposed on the magnet 68. The magnetostrictive element 70 is formed in a columnar shape having a sufficiently smaller diameter than the inner diameter of the cylindrical wall portion 66 </ b> A, and is disposed coaxially with the axial center portion of the yoke 66. As shown in FIG. 3, the magnetostrictive element 70 expands and contracts in the longitudinal direction according to the strength of the acting magnetic field. The vertical axis of the diagram shown in FIG. 3 can be grasped as the amount of displacement of the other end 70B with respect to one end (bottom plate 66B side) 70A of the magnetostrictive element 70. Note that a spacer 72 is interposed between the magnetostrictive element 70 and the magnet 68 as necessary.

  The magnetostrictive element 70 is covered with a coil 74 as an excitation device from the outer peripheral side (radially outer side). The coil 74 is configured to be wound around a bobbin 76 held by a yoke 66, and causes a magnetic field generated by energization to act on the magnetostrictive element 70. That is, the other end 70B of the magnetostrictive element 70 is displaced with respect to the one end 70A according to the magnitude of the magnetic field applied from the coil 74.

  An output shaft 78 as an output unit is fixed to the other end 70B of the magnetostrictive element 70 described above. Specifically, the output shaft 78 has one end 78 </ b> A fixed to the other end 70 </ b> B of the magnetostrictive element 70, an intermediate portion 78 </ b> B inserted through the through-hole 66 </ b> D of the yoke 66, and the other end 78 </ b> C protruding outside the yoke 66. Yes. A bolt portion 78D is integrally formed on the other end 78C side of the output shaft 78.

  The excitation force generator 60 includes a weight 80 fixed to the other end 78 </ b> C of the output shaft 78 constituting the actuator 20. More specifically, the weight 80 is formed in a short cylindrical shape in this embodiment, and the nut 82 is screwed into the bolt portion 78D of the output shaft 78 inserted through the through hole 80A formed in the shaft center portion. As a result, the output shaft 78 is fixed to the other end 78C.

  Further, a flange 84 is formed so as to protrude radially outward from a portion of the output shaft 78 located in the yoke 66. A preload setting spring 86 is disposed between the flange 84 and the top plate 66C of the yoke 66 in a compressed state. The preload setting spring 86 applies an initial compressive displacement to the magnetostrictive element 70 by its urging force. Thereby, in the actuator 20, the magnetostrictive element 70 to which the magnetic field from the coil 74 is applied is configured to expand and contract mainly in the range of compression deformation.

  Further, the actuator 20 includes a controller 88 for energizing (powering) the coil 74. In this embodiment, the control unit 88 is configured to control the frequency and phase of power supply (voltage application) to the coil 74 so that the vibration plate 18 is vibrated at a predetermined frequency and phase by the actuator 20. . The control unit 88 and the coil 74 constitute an excitation device in the present invention.

  In the excitation force generator 60 configured as described above, the magnetostrictive element 70 energized at a predetermined cycle by the coil 74 of the actuator 20 causes the weight 80 to vibrate and displace relative to the yoke 66 via the output shaft 78. The reaction force accompanying the vibration of the weight 80 is transmitted to the diaphragm 18 as a forced force, that is, an exciting force via the yoke 66 and the bracket 64, so that the diaphragm 18 vibrates at the frequency of the exciting force. It has become. That is, the excitation force generator 60 is not a device that inputs displacement (for example, displacement with respect to the case 12) to the diaphragm 18, but inputs the excitation force F as schematically shown in FIG. It is configured as a device that generates forced vibration by force.

  Supplementing with FIG. 3, the displacement characteristics of the magnetostrictive element 70 with respect to the strength of the magnetic field are the same (symmetric) when the direction of the magnetic field is positive and negative, and the displacement occurs according to the scalar quantity of the magnetic field, and Has hysteresis according to the direction of change of the magnetic field. In this embodiment, the magnetic bias is set by the above-described magnet 68 so that the displacement of the magnetostrictive element 70 is used in the magnetic field region B of FIG. Therefore, the displacement y of the sine wave-like other end 70B (weight 80) can be obtained with respect to the sine wave-like input magnetic field M shown in FIG.

F of the exciting force (fluctuating load) that can be generated by the exciting force generator 60 is expressed as follows, assuming that the mass of the weight 80 is m [kg] and the acceleration of the weight 80 by the actuator 20 is α [m / s ² ]. = M × α [N], and when the weight 80 vibrates in a sine wave shape, the amplitude is A [m] and the frequency (frequency of the input magnetic field to the magnetostrictive element 70 by the coil 74) is f [Hz]. Then, since αmax = A × (2πf) ² , the maximum value (instantaneous value) of the excitation force F is Fmax = m × A × (2πf) ² . On the other hand, the force Fm that can be generated by the magnetostrictive element 70 is Fm = S × σ when the cross-sectional area of the magnetostrictive element 70 is S [m ² ] and the generated stress of the magnetostrictive element 70 is σ [Pa]. Fm = S × σ.

Therefore, the excitation force generator 60 obtains the excitation force F (Fmax) in accordance with the mass m of the weight 80, the excitation amplitude A, and the excitation frequency f within the range of the force Fm that can be generated by the magnetostrictive element 70. be able to. That is, the excitation force generator 60 can obtain a large excitation force F by applying a magnetic field having a high fluctuation rate to the magnetostrictive element 70 to increase the expansion / contraction acceleration and drive the weight 80 with a large acceleration. For this reason, the control unit 88 of the excitation force generating unit 60 performs an operation of driving the magnetostrictive element 70 at a frequency f ₇₀ higher than the frequency f ₁₈ for exciting the vibration plate 18 to be excited. It is configured to perform to repeat at the vibration frequency f ₁₈ energized coil 74 (voltage application). More specifically, for example, as shown in FIG. 4 (A), the control unit 88 performs a period T _{18 during} a period T ₁₈ (= 1 / f ₁₈ ) of the excitation frequency f ₁₈ of the diaphragm ₁₈ . Also, the coil 74 is configured to generate a variable magnetic field having a frequency f ₇₀ (= 1 / T ₇₀ ) higher than the frequency f _{18 for} one short period T ₇₀ .

For example, the frequency range required for the speaker device 10 is approximately 20 [Hz] to 500 [Hz], that is, the minimum period T ₁₈ min of vibration (sound generation) of the diaphragm ₁₈ is 2 [ms]. in view, the driving frequency _{f 70} of the magnetostrictive element 70 may be _f 70 = 1 [kHz]. In this case, for example, assuming that the weight 80 has a mass m = 0.1 [kg], an excitation amplitude A = 0.0001 [m], and an excitation frequency f = f ₇₀ = 1 [kHz], Fmax≈395 [N]. Thus, it can be seen that a sufficient excitation force F can be obtained without increasing the excitation amplitude A. The magnetostrictive element 70 has a response of 100 [kHz] or more and can follow the limit frequency of the magnetic field change. For this reason, it is possible to obtain a larger excitation force by exciting the weight 80 with a larger acceleration (high frequency), and for example, it has sufficient performance for use in the phase control of a sound wave described later.

  The mass m of the weight 80 is determined in accordance with the size and shape of the diaphragm 18 (vertical dimensions a and b shown in FIG. 2B for the rectangular diaphragm 18) and the sound pressure to be generated. In an example of constituting an exhaust sound active silencer 30 (main muffler 42) to be described later, the mass m of the weight 80 and the magnetostrictive element that drives the weight 80 so as to generate a sound pressure substantially equal to the exhaust sound of each frequency. 70 dimensions are determined.

Note that the control unit 88 replaces the configuration of applying a sine wave voltage having the frequency f ₇₀ as shown in FIG. 4A, and the pulse width T ₇₀ at the frequency f ₁₈ as shown in FIG. 4B. The pulse wave (1 [ms] in the above example) may be input. Even in the configuration of inputting this pulse wave, a large excitation force F can be obtained as in the case of inputting the above sine wave.

  Next, the operation of this embodiment will be described.

  In the speaker device 10 having the above-described configuration, when the coil 74 of the actuator 20 is energized, the actuator 20 vibrates the weight 80 in the contact / separation direction with the diaphragm 18 at a frequency corresponding to the energization frequency. The reaction force accompanying the vibration of the weight 80 acts on the diaphragm 18 as an excitation force, and the diaphragm 18 vibrates at the frequency of the excitation force. Due to this vibration, sound waves are generated outward (in the direction opposite to the sealed space R) in the speaker device 10.

  Here, since the speaker device 10 is configured to vibrate the diaphragm 18 using the reaction force generated when the actuator 20 vibrates the weight 80 as a vibration force, the speaker device 10 depends on the amplitude that can be generated by the actuator 20. A large excitation force can be applied to the diaphragm 18. In particular, since the actuator 20 uses the magnetostrictive element 70 as a driving source of the weight 80, the load 80 that has a large load Fm = S × σ and a relatively large mass m can be driven at a high frequency (high acceleration). As a result, it was possible to obtain a large excitation force F with a compact configuration. Thereby, in the speaker apparatus 10, a large sound pressure can be ensured in a low frequency region (for example, 20 Hz to 500 Hz), and a flat frequency characteristic can be obtained.

In particular, in the excitation force generator 60 that constitutes the speaker device 10, the controller 88 applies to the magnetostrictive element 70 a varying magnetic field having a period T ₇₀ that is shorter than the period T _{18 of} the sound wave output from the diaphragm 18. The acceleration of the magnetostrictive element 70, that is, the weight 80 is increased, and the diaphragm 18 can be reliably vibrated with a large constant vibration force without depending on the vibration amplitude A and mass m (larger than necessary). .

  Thus, in the speaker device 10 according to the present embodiment, the weight 80 is vibrated using the magnetostrictive element 70 having a large generated stress σ and good response, although the obtained vibration amplitude A is relatively small. By utilizing the reaction force associated with this, it was possible to achieve a sufficient sound pressure at a low frequency with a compact configuration. Further, other effects of the speaker device 10 will be supplemented below.

  In the speaker device 10, since the end 16 </ b> A of the peripheral wall 16 of the peripheral wall 16 constituting the case 12 and the peripheral edge 18 </ b> A of the diaphragm 18 are joined over the entire periphery, the waterproof and dustproof properties for the sealed space R are provided. Is secured. Moreover, since the case 12 and the diaphragm 18 are comprised with metal materials, such as stainless steel, heat resistance is favorable. Since the metal case 12 and the diaphragm 18 are joined to the end 16A and the peripheral edge 18A of the peripheral wall 16 over the entire circumference as described above, the mechanical strength against the external force and the like is high including the joining portion. . Thus, the speaker device 10 does not include a component made of rubber or resin as a component as in a speaker device used in a good environment such as a room, and does not use an adhesive or the like for joining the components. There are few restrictions on the usage environment.

  Here, in the speaker device 10, the flat diaphragm 18 is vibrated to generate sound waves, so that plane waves with high directivity in the sound wave transmission direction are easily output. For this reason, there is little attenuation with respect to the distance of sound pressure. In addition, low frequency sound can be generated without depending on the capacity of the case 12 (sealed space R), and the plane wave is less attenuated with respect to the sound pressure distance as described above. ) Large sound waves can be obtained. That is, as described above, it is possible to propagate a sound wave having a large sound pressure obtained by the large excitation force F, which is a reaction force accompanying the excitation of the weight 80, without being attenuated. Accordingly, the speaker device 10 can be reduced in size as compared with the cone-type speaker 100 that generates the diffused wave Wd as shown in FIG. 6B, for example. In particular, in the speaker device 10, since the bead 26 is formed on the diaphragm 18, it is possible to reliably generate a plane wave in a required frequency band.

  Further, in the speaker device 10, since the case 12 and the diaphragm 18 form a sealed space R, sound generated by vibration of the diaphragm 18 inside the sealed space R leaks outside the sealed space R. hard. Further, the case 12 having a closed cross-sectional structure with the diaphragm 18 has a predetermined rigidity, and the bottom wall 14 is reinforced by the ribs 22, so that the bending determined according to the rigidity (mainly of the bottom wall 14). It is effectively prevented that sound having a frequency component lower than the limit frequency of vibration (bending vibration) is transmitted outside the sealed space R. Further, since the sound absorbing material 28 is filled in the sealed space R, the medium and high frequency components (components having a frequency higher than the above-mentioned limit frequency) generated by the vibration of the diaphragm 18 inside the sealed space R are included. Is absorbed by the sound-absorbing material 28 and is prevented from passing outside the sealed space R (case 12).

  In the above embodiment, an example in which the annular bead 26 is provided in order to set the divided vibration mode of the diaphragm 18 so as to output a plane wave in a required frequency band is shown, but the present invention is limited to this. Instead, for example, the diaphragm 18 may be provided with an uneven shape instead of the bead 26 or together with the bead 26. The uneven shape may be formed in an annular shape, such as a bead 26, and may be formed so that the cross section has a rectangular wave shape, or may be formed intermittently in the circumferential direction of the diaphragm 18, for example.

(Exhaust sound active silencer)
Next, an exhaust sound active silencer 30 as a noise suppression device to which the above-described speaker device 10 is applied will be described with reference to FIGS. Note that an arrow FR appropriately shown in each figure indicates a front side in the vehicle longitudinal direction of an automobile to which the exhaust noise active silencer 30 is applied, an arrow UP indicates an upper side in the vehicle vertical direction, and an arrow W indicates a vehicle width direction. And

  FIG. 9 is a schematic plan view showing an exhaust system 34 of an internal combustion engine 32 having an exhaust sound active silencer 30 to which the speaker device 10 is applied. As shown in this figure, the exhaust system 34 includes an exhaust pipe 36 that guides exhaust gas discharged from the internal combustion engine 32 to the outside of the system, and an upstream end 36 A of the exhaust pipe 36 has an exhaust manifold of the internal combustion engine 32. 32A. On the other hand, the downstream end of the exhaust pipe 36 is an air release portion 36B. Between the upstream end 36A of this exhaust pipe 36 (exhaust system path formed) and the atmosphere opening portion 36B, a catalytic converter 38 for purifying exhaust gas, in order from the upstream side, for reducing exhaust noise. A sub muffler 40 and a main muffler 42 are provided. In this embodiment, the speaker device 10 is applied to the main muffler 42. That is, the main muffler 42 corresponds to an exhaust system part and a partition in the present invention.

  As shown in FIGS. 7A to 7C, the main muffler 42 includes a diaphragm 18 of the speaker device 10 provided in a pair in the vertical direction of the vehicle body and a peripheral portion of the upper and lower diaphragms 18 facing each other. A muffler side surface member 44 having a substantially rectangular frame shape in plan view welded and joined to the entire circumference of 18A forms a sound deadening chamber (expansion chamber or resonance chamber) 46 that is a closed space. The muffler side member 44 having a substantially rectangular frame shape in plan view is connected to an inlet pipe 48 connected to the upstream exhaust pipe 36 and an outlet pipe 50 whose end is the atmosphere opening portion 36B of the exhaust pipe 36. .

  As described above, a part of the outer wall of the main muffler 42 is constituted by the diaphragm 18 of the speaker device 10, and the diaphragm 18 directly acts on the exhaust gas flowing (diffused and discharged) inside the main muffler 42. Sound waves are emitted. Also, as shown in FIGS. 7A to 7C, the muffler side member 44 moves the flat main muffler 42 in the vertical direction with a small size in the vehicle vertical direction with respect to the vehicle longitudinal direction and the vehicle width direction. The dimensions are determined so as to be formed between the speaker devices 10.

The control unit 88 of each speaker device 10 is shown in FIG. 8A based on the output of, for example, a microphone provided in the main muffler 42 or an engine tachometer that outputs a signal corresponding to the rotational speed of the internal combustion engine 32. As shown, the applied voltage to the coil 74 of each actuator 20 (the frequency f _{18 of the} output vibration output by the diaphragm ₁₈ (period) so that the sound wave Sa of substantially equal sound pressure is output in the opposite phase to the exhaust sound Se. T ₁₈ ), phase, period added for each period of the output vibration, voltage application pattern of pulse width T ₇₀ , etc.) are controlled.

  In the exhaust noise active silencer 30 configured as described above, the exhaust gas of the internal combustion engine 32 flows through the exhaust system 34, and for example, with respect to the relatively low-frequency exhaust noise caused by the exhaust gas pulsation, The actuator 20 is driven so that the diaphragm 18 generates a sound wave having an approximately equal sound pressure with an opposite phase. For this reason, as shown in FIG. 8B, the exhaust noise Se and the sound wave Sa generated by the diaphragm 18 cancel each other, and the exhaust noise is reduced. In addition, the frequency band of the exhaust sound of the rotational secondary component of the internal combustion engine 32 is approximately 20 Hz to 500 Hz corresponding to the idle rotation to the maximum rotation speed.

  Here, since the exhaust sound active silencer 30 includes the speaker device 10 described above, the exhaust sound active silencer 30 can be used by being exposed to the outside of the vehicle in a high temperature environment and exhibiting a required silence performance. That is, the speaker device 10 formed by welding and joining the metal case 12 and the diaphragm 18 has good environmental resistance and deteriorates due to high-temperature exhaust gas as in the configuration using rubber or resin parts. Therefore, stable muffling performance is demonstrated over a long period of time. Further, even if the speaker device 10 is disposed under the vehicle body floor, intrusion of rainwater or splashed water from the road surface into the case 12 (sealed space R) due to splashing from the road surface is prevented, and the actuator 20 (electric system) Is protected. Furthermore, since the metal case 12 has a required mechanical (breaking) strength, the speaker device 10 is prevented from being damaged by a stepping stone or the like.

  Here, in the exhaust sound active silencer 30, the diaphragm 18 of the speaker device 10 constitutes the outer wall (partition) of the main muffler 42, and the diaphragm 18 serves as an exhaust gas in the main muffler 42, that is, a vibration source. In order to directly output sound waves, that is, to directly cancel the exhaust sound of exhaust gas having a large acoustic energy, for example, a configuration in which sound waves are output toward a relatively low energy exhaust gas that is opened to the atmosphere. In comparison, the exhaust noise suppression effect is greater. In addition, since sound waves are output in the main muffler 42 that is a closed space, the transmission loss of sound waves generated by the speaker device 10 is small compared to the configuration in which sound waves are output toward the exhaust gas released to the atmosphere. Sound can be canceled more effectively, and the effect of suppressing exhaust noise can be improved.

  And the speaker apparatus 10 which comprises the exhaust sound active silencer 30 drives the weight 80 with the actuator 20, and produces the sound wave Sa which is a plane wave of a large sound pressure in a low frequency range, and makes exhaust sound efficient. Can be counteracted. In particular, the speaker device 10 is set so that the bead 26 generates a plane wave up to the exhaust sound frequency band (idle rotation to maximum rotation speed) of the rotation secondary component of the internal combustion engine 32. It can cancel more efficiently.

  Furthermore, in the speaker device 10 in which the diaphragm 18 is covered with the case 12, the diaphragm 18 is prevented from leaking the sound emitted outward from the main muffler 42 to the outside. In particular, a component having a frequency lower than the limit frequency of the case 12 prevents transmission outside the sealed space R, and a component having a frequency higher than the limit frequency is absorbed by the sound absorbing material 28. The accompanying noise generation is prevented.

  Further, since the main muffler 42 is formed in a flat shape that is flat in the vertical direction, the height in the vertical direction of the vehicle body is kept low even if the speaker device 10 is disposed above and below the main muffler 42. On the other hand, since the upper and lower diaphragms 18 constitute a flat portion of the main muffler 42, that is, a wall portion having a large contact area with the exhaust gas, the exhaust sound of the exhaust gas is more effectively suppressed by the sound wave output of the diaphragm 18. can do.

  In the above embodiment, an example in which the speaker device 10 is applied to the exhaust sound active silencer 30 has been described. However, the present invention is not limited to this, and the speaker device 10 can be applied to various uses. Further, the excitation force generator 60 constituting the speaker device 10 can be applied to various uses other than the speaker application.

  Moreover, in the said embodiment, although the exhaust sound active silencer 30 showed the example provided with a pair of upper and lower speaker apparatus 10, this invention is not limited to this, For example, it seems that either upper or lower speaker apparatus 10 is provided. Anyway.

  Further, in the above embodiment, the exhaust sound active silencer 30 includes the pair of upper and lower speaker devices 10. However, the speaker device 10 may be disposed on the side surface in the vehicle width direction or the end surface in the vehicle longitudinal direction of the main muffler 42. good. Further, for example, the diaphragm 18 of the speaker device 10 may be formed in an elliptical shape corresponding to the longitudinal end face of the wound muffler, and the longitudinal end face of the wound muffler may be configured by the elliptical diaphragm 18. In this case, the exhaust sound active silencer 30 can be easily applied to an existing muffler.

It is side sectional drawing which shows the excitation force generation part which comprises the principal part of the speaker apparatus which concerns on embodiment of this invention. It is a figure which shows typically the speaker apparatus which concerns on embodiment of this invention, Comprising: (A9) is a side view, (B) is a top view. It is a diagram which shows the magnetic field-displacement characteristic of the magnetostrictive element which comprises the speaker apparatus which concerns on embodiment of this invention. (A). It is a diagram which shows the magnetic field generation pattern by the control part which comprises the speaker apparatus which concerns on embodiment of this invention, (B) is a diagram which shows the modification of a magnetic field generation pattern. It is a figure which shows the speaker apparatus which concerns on embodiment of this invention, Comprising: (A) is a top view, (B) is a sectional side view along the 5B-5B line of FIG. 5 (A), (C) is a bottom face. FIG. (A) is explanatory drawing which shows typically the plane wave which the speaker apparatus which concerns on embodiment of this invention generate | occur | produces, (B) is explanatory drawing which shows typically the diffused wave which the cone type speaker which concerns on a comparative example generate | occur | produces. . It is a figure which shows the exhaust sound active silencer to which the speaker apparatus which concerns on embodiment of this invention is applied, Comprising: (A) is a sectional side view, (B) is a top view, (C) is a rear view. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the silencing principle by the exhaust sound active silencer to which the speaker apparatus which concerns on embodiment of this invention is applied, Comprising: (A) is a diagram which shows separately the exhaust sound and the sound wave to cancel, (B) is a diagram combined with the exhaust sound and the sound wave to be canceled. 1 is a plan view of an exhaust system to which an exhaust sound active silencer to which a speaker device according to an embodiment of the present invention is applied is applied.

Explanation of symbols

10 Speaker device 18 Diaphragm (excitation target)
20 Actuator 60 Excitation force generator (vibration generator)
66 York (main body)
70 Magnetostrictive element 74 Coil (Excitation device)
78 Output shaft (output unit)
80 weight
88 Control unit (excitation device)

Claims (4)

An actuator that, by operating, vibrates the output unit with respect to the main body fixed to the vibration target;
A weight provided at the output of the actuator;
A vibration generating device.   The vibration generating apparatus according to claim 1, wherein the actuator includes a magnetostrictive element that vibrates the output unit with respect to the main body by periodically changing the applied magnetic field.   3. The actuator includes an excitation device that applies a magnetic field that changes in a time shorter than an output vibration cycle to be generated in the vibration target to the magnetostrictive element at the output vibration cycle. The vibration generator as described. A flat diaphragm,
The vibration generator according to any one of claims 1 to 3, wherein the vibration plate is fixed to the body of the actuator as the vibration target.
A speaker device comprising:

Images