JP2008075567A - Membrane vibration resonator and control device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane vibration resonator silencing the sound of a predetermined frequency and exerting a stable silencing effect even when temperature fluctuates. <P>SOLUTION: The membrane vibration resonator uses a diaphragm 3 formed of dielectric elastomer whose elastic coefficient changes with application of a voltage. The elastic coefficient of the diaphragm can be changed by the application of the voltage and a change of the elastic coefficient by fluctuation of atmospheric temperature is canceled by a change of the elastic coefficient by the application of the voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a membrane vibration resonator capable of suppressing intake noise of an intake system connected to an engine or an intake system for air conditioning, and a control device thereof.

  Conventionally, side branch type resonators and Helmholtz type resonators have been used in order to suppress intake noise of an intake system connected to a vehicle engine. However, according to these conventional resonators, when the sound pressure of a low frequency component having a relatively low frequency in the intake noise is suppressed, the resonator becomes large and the arrangement space becomes large.

  For example, in the case of a side branch type resonator, the natural frequency of a sound that can be silenced by resonance depends on the length of the side branch. On the other hand, the wavelength is longer for lower frequency components. For this reason, in order to suppress a low frequency component with a side branch type resonator, it is necessary to increase the length of the side branch. Therefore, the arrangement space for the resonator is increased.

  In the case of a Helmholtz type resonator, the natural frequency of a sound that can be silenced by resonance can be expressed by the following equation.

  In the formula, f represents a natural frequency (resonance frequency), c represents the speed of sound, l represents the length of the communication tube, V represents the volume of the hollow chamber, and S represents the cross-sectional area of the communication tube. When suppressing the low frequency component, it is necessary to reduce the natural frequency f. In order to reduce the natural frequency f, it is necessary to increase l or V with respect to S. Therefore, also in this case, the space for arranging the resonators becomes large.

  Therefore, Japanese Utility Model Laid-Open No. 02-080710 introduces a resonator having a small arrangement space. The resonator described in the document includes an elastic film and a cup member. The cup member is attached to the surge tank with the cup opening turned down. An elastic film is interposed between the cup opening and the surge tank. The inside of the cup and the inside of the surge tank are blocked by the elastic film.

  The natural frequency of the elastic membrane is set to be equal to the resonance frequency of air column resonance inside the surge tank. According to the resonator described in this document, air column pulsation inside the surge tank can be suppressed by the membrane vibration effect of the elastic membrane.

  Japanese Patent Application Laid-Open No. 2003-065173 proposes a low noise duct using membrane vibration. This low noise duct is composed of a communication short tube communicating with the duct body, a membrane sheet that closes the communication hole of the communication short tube, and a protective cap that is attached to the communication short tube so as to cover the film sheet. is there.

  According to these resonators, a silencing effect can be obtained by resonance of the elastic film or the film-like sheet. Therefore, the entire volume can be reduced, and the arrangement space can be reduced.

  However, in the case of the conventional resonator described above, it is difficult to maintain a desired sound pressure suppression effect for a long time. In other words, the natural frequency of the elastic membrane must always be maintained at a frequency equal to the resonance frequency of the air column resonance. Here, the natural frequency of the elastic film depends on the tension of the elastic film. However, the tension of the elastic film gradually decreases as time passes after the elastic film is installed. For this reason, in the case of the above-described resonator, it is difficult to maintain a desired sound pressure suppression effect for a long time.

  Japanese Patent Laid-Open No. 2006-125381 discloses a resonator that is disposed in an intake system having a tubular body section that defines an intake port for taking in outside air and an intake passage that communicates the intake port and the combustion chamber of the engine. One end of the pipe is connected to the pipe body, the other end is closed, and a branch pipe section that divides the silencing chamber into the interior, and the silencing chamber is divided into at least one air spring chamber and the intake air propagating from the intake passage There has been proposed a membrane vibration resonator including at least one diaphragm having a natural frequency lower than the frequency of a sound to be silenced among noises.

According to this membrane vibration resonator, the diaphragm is equivalent to the mass of the communication pipe part of the conventional Helmholtz type resonator. Therefore, the installation space can be small. Moreover, the mass effect of the diaphragm is used. In other words, the sound pressure of the sound to be silenced is suppressed by a resonance phenomenon between the diaphragm and the air in the air spring chamber adjacent to the back side of the diaphragm.
Actual Kaihei 02-080710 JP2003-065173 JP 2006-125381

  By the way, when the elastic film, the film-like sheet, or the diaphragm described in each of the above-mentioned patent documents is formed from resin, rubber, or the like, the tension, elastic modulus, and the like vary depending on the ambient temperature. For this reason, the resonators described in Patent Documents 1 and 2 have a problem that the sound pressure suppression effect varies depending on the temperature as in the case of deterioration over time. Further, even the resonator described in Patent Document 3 has a problem that the mass effect changes because the elastic modulus of the diaphragm changes depending on the temperature, and the frequency that can be silenced changes.

  The present invention has been made in view of the above circumstances, and it is an object to be solved to be able to mute a sound having a predetermined frequency even if the temperature fluctuates so that a stable muffling effect is exhibited.

  A feature of the membrane vibration resonator of the present invention that solves the above-described problem is that it is disposed in an intake system having a tubular portion that constitutes an intake passage, and has at least one resonance tube having one end branched and connected to the tubular portion. A diaphragm vibration resonator having at least one diaphragm which is partitioned into two resonance chambers and has a natural frequency, and the diaphragm is made of a dielectric elastomer whose elastic coefficient is changed by application of a voltage.

  The control device for a membrane vibration resonator according to the present invention is characterized in that the membrane vibration resonator according to claim 1, a temperature detection means for detecting a physical quantity related to the atmospheric temperature of the diaphragm, and a voltage application means for applying a voltage to the diaphragm. And a control means for controlling the voltage application means based on the temperature detected by the temperature detection means, and changing the frequency of the sound that can be silenced by changing the elastic coefficient of the diaphragm according to the ambient temperature. It is in.

  In the membrane vibration resonator of the present invention, the diaphragm is formed of a dielectric elastomer whose thickness and elastic modulus change with application of voltage. Therefore, by applying a voltage to the diaphragm, the thickness and elastic modulus of the diaphragm can be freely controlled, and the elastic coefficient can be changed. For example, when a diaphragm is disposed in a state where a predetermined tension is applied at normal temperature, when the temperature decreases, the diaphragm increases in elasticity and contracts to increase the tension. In this case, when a predetermined voltage is applied to the diaphragm, the generated Coulomb force causes the diaphragm to become smaller in cross section and deformed in the extending direction, lowering the tension and lowering the elastic modulus. As a result, the increase in the elastic modulus due to the decrease in temperature cancels out the decrease in the elastic modulus due to voltage application, and the diaphragm vibrates at the predetermined natural frequency and has the predetermined physical properties. Is done.

  Further, the degree of expansion and the elastic modulus of the diaphragm can be changed depending on the magnitude of the applied voltage, and the elastic coefficient can be controlled to a predetermined value. Therefore, the frequency of the sound to be silenced (hereinafter referred to as the target frequency) can be easily varied, and the sound of a plurality of frequencies can be silenced with one diaphragm.

  The membrane vibration resonator of the present invention includes a resonance tube having one end branched and connected to a tube body portion, and at least one diaphragm having a natural frequency while partitioning the inside of the resonance tube into at least one resonance chamber. The other end of the resonance tube may be closed or opened.

  The diaphragm is held in the resonance tube or the other end of the resonance tube so as to vibrate, and the resonance tube is partitioned into at least one resonance chamber. For example, when a single diaphragm that divides the center of the resonance tube is disposed, resonance chambers are formed on both sides of the diaphragm. When the other end of the resonance tube is opened, a resonance chamber is formed on the resonance tube side of the diaphragm. There may be one diaphragm or a plurality of diaphragms. When a plurality of sheets are arranged, a resonance chamber is also formed between the diaphragms.

  The resonance pipes may be formed to have the same diameter over the entire length, but the communication pipe part communicating with the intake passage, and the cross-sectional area perpendicular to the propagation direction of the intake noise communicated with the communication pipe part. It is also preferable to have a structure including a hollow chamber larger than the communication pipe portion. In the latter case, the communication pipe part constitutes the communication pipe part of the Helmholtz type resonator, and the cavity chamber constitutes the cavity part of the Helmholtz type resonator. In the latter case, the communication pipe portion may be inside the hollow chamber. Further, the diaphragm may be formed in the communication pipe portion or in the hollow chamber.

  According to the structure comprising the communication pipe portion communicating with the intake passage and the hollow chamber communicating with the communication pipe portion and having a cross-sectional area perpendicular to the propagation direction of the intake noise larger than that of the communication pipe portion, the same shape Helmholtz Compared with the type of resonator, the target frequency can be shifted to the lower frequency side. In addition, the physique can be made smaller than a Helmholtz type resonator having the same target frequency.

  The diaphragm is formed of a dielectric elastomer whose elastic coefficient changes with application of voltage. The dielectric elastomer can be selected from the group consisting of silicone elastomers, acrylic elastomers, polyurethanes, copolymers containing PVDF, ethylene / propylene / diene elastomers, and combinations thereof. In this way, dielectric elastomers whose elastic modulus changes with the application of voltage are disclosed in JP-T 2001-514278, JP-T 2003-526213, JP-T 2003-505865, JP-T 2003-506858, JP-T This is described in detail in JP-A-2005-527178 and JP-T-2005-522162.

  The application direction of the voltage to the diaphragm is generally the thickness direction, but in some cases, it can be applied in a direction perpendicular to the thickness direction. When a voltage is applied in the thickness direction, the voltage may be applied directly to the diaphragm, but it is desirable to form a pair of electrodes on the diaphragm and apply the voltage to the diaphragm via the electrodes. Here, since the diaphragm expands and contracts as the thickness changes, it is desirable that the electrode has flexibility. Such flexible electrodes include graphite, carbon, conductive polymers, conductive grease such as carbon grease or silver grease, colloidal suspensions, high aspect ratio conductive materials such as carbon microfibers and carbon nanotubes, and It can be selected from the group consisting of a mixture of ion conductive materials.

  A control device for a membrane vibration resonator of the present invention includes a membrane vibration resonator of the present invention, a temperature detection means for detecting a physical quantity related to the atmospheric temperature of the diaphragm, a voltage application means for applying a voltage to the diaphragm, a control means, Have

  As a physical quantity related to the atmospheric temperature of the diaphragm, the atmospheric temperature may be detected directly or estimated from the air temperature. Therefore, a general temperature sensor can be used as the temperature detection means.

  The voltage application means can be composed of the above-described flexible electrode, a power source, and a transformer device.

  The control means controls the voltage application means based on the temperature detected by the temperature detection means, and preferably uses an ECU.

  The control device of the present invention preferably further includes a rotation speed detection means for detecting a physical quantity related to the engine rotation speed. Thereby, the target frequency to be silenced can be set according to the actual driving situation, and intake noise can be further suppressed.

  The rotation speed detection means may directly detect the engine rotation speed, or can calculate the engine rotation speed by calculation from the depression amount of the accelerator pedal, the vehicle speed, and the like.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Example 1)
FIG. 1 shows a cross-sectional view of the membrane vibration resonator of this embodiment. The membrane vibration resonator includes a communication pipe portion 1 branched from an intake duct, a cavity chamber 2 communicating with the communication pipe portion 1 and having a cross-sectional area perpendicular to the propagation direction of intake noise larger than that of the communication pipe portion 1. And a diaphragm group 3 ′ for partitioning the hollow chamber 2. In the hollow chamber 2, resonance chambers 20 and 21 are respectively formed on both sides of the diaphragm group 3 ′.

  As shown in FIG. 2 in an enlarged manner, the diaphragm group 3 ′ includes a 100 μm-thick diaphragm body 30 formed from a silicon-based dielectric elastomer, and a 20 μm-thick silicon system formed on both front and back surfaces of the diaphragm body 30. Six diaphragms 3 made of the flexible electrode layer 31 are laminated. The flexible electrode layer 31 of each diaphragm 3 is electrically connected to each side, and a positive electrode 32 and a negative electrode 33 are formed on both sides of each diaphragm 3.

  The membrane vibration resonator of the present embodiment is disposed on the upstream side of the air cleaner case 4 as shown in FIG. The positive electrode 32 and the negative electrode 33 of each diaphragm 3 are connected to the control unit 5 using an ECU. A temperature sensor 22 is disposed in the hollow chamber 2.

  As shown in FIG. 3, the control unit 5 includes a calculation unit 50, an input unit 51, an output unit 52, and a storage unit 53. The detection signal of the temperature sensor 22 and the actual rotational speed of the engine 6 are input to the input unit 51, and the calculation unit 50 calculates based on the input value while referring to the information in the storage unit 53, and calculates the calculation result. The data is sent to the output unit 52. The output unit 52 applies a predetermined DC voltage to the positive electrode 32 and the negative electrode 33 based on the calculation result.

  The elastic modulus (k) of the diaphragm 3 changes depending on the temperature (T) in the hollow chamber 2. The relationship is as shown in the graph of FIG. 5, and this relationship is stored in the storage unit 53.

  Further, there is a substantially proportional relationship between the engine speed (R) and the resonance frequency (F) of the primary explosion component that is the main cause of noise, and the sound to be silenced by detecting the engine speed (R). Resonance frequency (F) (target frequency) is calculated. The storage unit 53 stores a relational expression (F = f (R)) between the engine speed (R) and the resonance frequency (F).

  Furthermore, in a general membrane vibration resonator, it is known that the resonance frequency (F) is substantially proportional to the elastic coefficient (k) of the diaphragm 3, and the target elastic coefficient (K) of the diaphragm 3 is determined from the resonance frequency (F). Can be calculated. The storage unit 53 stores a relational expression (k = f (F)) between the resonance frequency (F) and the elastic coefficient (k) of the diaphragm 3.

  On the other hand, as a characteristic of the dielectric elastomer constituting the diaphragm body 30 of the diaphragm 3, when a voltage (V) is applied in the thickness direction, the film is deformed in the extending direction, and the elastic coefficient (k) is lowered. However, as shown in FIG. 5, the degree of change in the elastic modulus (k) is larger as the temperature is lower, and the degree of change in the elastic modulus (k) is smaller as the temperature is higher.

Therefore, in this embodiment, the range of t ₁ ≦ T <t ₂ in FIG. 5 is mode I, the range of t ₂ ≦ T <t ₃ is mode II, and the range of t ₃ ≦ T <t ₄ is mode III. Divided into three ranges. And the tension | tensile_strength is set so that the diaphragm 3 may have a high elastic modulus (k) in the high temperature area which is mode III.

  When the temperature (T) decreases from mode III to mode II or mode I, the elastic modulus (k) of the diaphragm 3 increases. Therefore, it is necessary to apply the voltage (V) to lower the elastic modulus (k). However, since the relationship between the voltage (V) and the elastic coefficient (k) is different in each mode, a relational expression between the voltage (V) and the elastic coefficient (k) is prepared for each mode and stored in the storage unit 53. Keep it.

The relationship between the voltage (V) and the elastic modulus (k) is the relational expression (k = f ₁ (V)) in FIG. 6 in mode I, and the relational expression (k = f ₂ (V) in FIG. 7 in mode II. In mode III, the relational expression in FIG. 8 (k = f ₃ (V)) is obtained.

  Hereinafter, the control content of the control part 5 is demonstrated along the flowchart shown in FIG.

  When the engine is started in step 100, in step 101, the engine speed (R) detected from the ECU and the temperature (T) in the cavity 2 are input.

  In step 102, information in the storage unit 53 is referred to based on the input engine speed (R), and the relational expression (F = f (R)) between the engine speed (R) and the resonance frequency (F) is obtained. The resonance frequency (F) (target frequency) of the sound to be muted is determined. Further, the target elastic modulus (K) of the diaphragm 3 is obtained from the relational expression (k = f (F)) between the resonance frequency (F) and the elastic coefficient (k) of the diaphragm 3.

  In Steps 103 to 105, the information in the storage unit 53 is referred to based on the input temperature (T), and in Steps 106 to 108, which mode is determined.

When it is determined that the mode is I, the relational expression (k = f ₁ (V)) in FIG. 6 is referred to from the information in the storage unit 53, and the elastic modulus (k) of the diaphragm 3 is determined as the target elasticity in step 109. A voltage having a coefficient (K) is applied to the diaphragm 3. If it is determined that the mode is II, the relational expression (k = f ₂ (V)) of FIG. 7 is referred to from the information in the storage unit 53, and the elastic modulus (k) of the diaphragm 3 is determined as the target elasticity in step 110. A voltage having a coefficient (K) is applied to the diaphragm 3. If it is determined that the mode III is selected, the relational expression (k = f ₃ (V)) in FIG. 8 is referred to from the information in the storage unit 53, and the elastic modulus (k) of the diaphragm 3 is determined in step 111. A voltage (V) having an elastic modulus (K) is applied to the diaphragm 3.

  Thereby, the elastic coefficient (k) of each diaphragm 3 can be made into the target elastic coefficient (K), and the sound of the target frequency is silenced by the vibration of the diaphragm group 3 ′ and the resonance of the communication pipe portion 1 and the cavity chamber 2. be able to.

  In step 112, the above control is repeated until the engine is stopped.

  Therefore, according to the membrane vibration resonator and its control device of the present embodiment, the elastic coefficient of the diaphragm group 3 ′ can be changed according to the temperature (T) of the cavity chamber 2, and the diaphragm group 3 ′ is optimally vibrated. As a result, the sound of the target frequency obtained according to the engine speed (R) can be reliably silenced.

(Example 2)
In the present embodiment, control is performed based on the flowchart shown in FIG. 9 using the same apparatus as in the first embodiment except that the temperature sensor 22 is not provided.

  The storage unit 53 includes a relational expression (F = f (R)) between the engine speed (R) and the resonance frequency (F), and a relational expression between the resonance frequency (F) and the elastic coefficient (k) of the diaphragm 3. (K = f (F)) is stored.

  When the engine is started in step 200, the engine speed (R) detected from the ECU is input in step 201.

  In step 202, the information in the storage unit 53 is referred to based on the input engine speed (R), and from the relational expression (F = f (R)) between the engine speed (R) and the resonance frequency (F). The resonance frequency (F) (target frequency) of the sound to be muted is determined. Further, the target elastic modulus (K) of the diaphragm 3 is obtained from the relational expression (k = f (F)) between the resonance frequency (F) and the elastic coefficient (k) of the diaphragm 3.

  In step 203, a voltage (V) having the elastic modulus (k) of the diaphragm 3 as the target elastic modulus (K) is applied to the diaphragm 3. In step 112, the above control is repeated until the engine is stopped.

  Therefore, according to the control device of the membrane vibration resonator of the present embodiment, the sound of the resonance frequency (F) (target frequency) that changes according to the engine speed (R) can be silenced and generated according to the traveling situation. Different noises can be effectively silenced.

  In the first and second embodiments, a plurality of the diaphragms 3 including the diaphragm main body 30 and the pair of flexible electrode layers 31 are stacked and used, but only one diaphragm 3 is used as shown in FIG. May be. Further, as shown in FIG. 11, a plurality of the diaphragms 3 can be arranged at intervals.

(Example 3)
FIG. 12 shows the membrane vibration resonator of this example. In addition, the same code | symbol as Example 1 is attached | subjected and demonstrated to the site | part provided with the function similar to Example 1. FIG.

  This membrane vibration resonator is provided along the side surface of an air cleaner case 4 as a tube body portion, and includes a communication pipe portion 1 communicating with the air cleaner case 4 and a hollow chamber 2 communicating with the communication pipe portion 1. The pipe portion 1 is located inside the hollow chamber 2. Three diaphragms 3 are arranged in the communication pipe portion 1.

  The communication pipe portion 1 has a cylindrical shape with an inner diameter of 80 mm and a length of 20 mm, one end communicates with the air cleaner case 4 and extends toward the inside of the cavity chamber 2, and the other end opens into the cavity chamber 2. The hollow chamber 2 is formed in a box shape having internal dimensions of 260 mm × 120 mm × 32 mm. The volume V of the hollow chamber 2 excluding the volume (0.1 liter) of the communication pipe section 1 is 0.88 liter.

  The diaphragm 3 is composed of a diaphragm main body 30 having a thickness of 500 μm formed of a dielectric elastomer similar to that of the first embodiment, and a flexible electrode layer 31 having a thickness of 20 μm formed on both front and back surfaces of the diaphragm main body 30. Similar to 1, a voltage is applied through a pair of flexible electrode layers 31.

  The membrane vibration resonator of the present invention can be used for a duct of an air conditioner in addition to the intake device for the engine shown in the embodiment.

It is a schematic sectional drawing of the air intake duct using the membrane vibration resonator which concerns on one Example of this invention. It is sectional drawing of the diaphragm group used for the membrane vibration resonator which concerns on one Example of this invention. It is a block diagram of the control part in the control apparatus of the membrane vibration resonator which concerns on one Example of this invention. It is a flowchart which shows the process of the control part in the control apparatus of the membrane vibration resonator which concerns on one Example of this invention. 4 is a graph showing a relational expression stored in a control unit in the control device for a membrane vibration resonator according to an embodiment of the present invention. 4 is a graph showing a relational expression stored in a control unit in the control device for a membrane vibration resonator according to an embodiment of the present invention. 4 is a graph showing a relational expression stored in a control unit in the control device for a membrane vibration resonator according to an embodiment of the present invention. 4 is a graph showing a relational expression stored in a control unit in the control device for a membrane vibration resonator according to an embodiment of the present invention. It is a flowchart which shows the process of the control part in the control apparatus of the membrane vibration resonator which concerns on 2nd Example of this invention. It is a schematic sectional drawing of the air intake duct using the membrane vibration resonator which concerns on the other aspect of one Example of this invention. It is sectional drawing of the membrane vibration resonator which concerns on the other aspect of one Example of this invention. It is sectional drawing of the membrane vibration resonator based on 3rd Example of this invention.

Explanation of symbols

1: Communication pipe part 2: Cavity part 3: Diaphragm 3 ': Diaphragm group 4: Air cleaner 5: Control part 6: Engine 22: Temperature sensor
30: Diaphragm body 31: Flexible electrode layer

Claims (3)

A resonance tube disposed at an intake system having a tube portion constituting an intake passage, one end of which is branched and connected to the tube portion, and at least one having a natural frequency while partitioning the resonance tube into at least one resonance chamber. A diaphragm vibration resonator including a plurality of diaphragms,
The membrane vibration resonator, wherein the diaphragm is made of a dielectric elastomer whose elastic coefficient changes with application of voltage. A membrane vibration resonator according to claim 1;
Temperature detecting means for detecting a physical quantity related to the atmospheric temperature of the diaphragm;
Voltage applying means for applying a voltage to the diaphragm;
Control means for controlling the voltage application means based on the temperature detected by the temperature detection means,
A control device for a membrane vibration resonator, wherein the frequency of a sound that can be silenced is varied by changing an elastic coefficient of the diaphragm according to an ambient temperature.   The control device for a membrane vibration resonator according to claim 2, further comprising a rotational speed detection means for detecting a physical quantity related to the engine rotational speed.

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