JP4764183B2 - Silencer duct for cooling - Google Patents

Description

  The present invention relates to a duct used for cooling a large capacity battery mounted on a vehicle such as an automobile with a medium such as air.

  A large-capacity battery mounted on a hybrid vehicle or a fuel cell vehicle with an internal combustion engine and an electric motor is repeatedly charged and discharged while the vehicle is running, and is equivalent to the square of the current in the chemical reaction of the electrolyte and the internal resistance of the battery. The amount of generated heat is generated. Therefore, in order to keep the battery temperature within an appropriate range, it is essential to install a cooling circuit. In such a cooling circuit, air (cooling air) is generally used as a cooling medium, and the air flowing in the cooling circuit is circulated by a fan unit having a fan and an electric motor that rotates the fan to cool the battery. .

  In recent years, the capacity of an electric motor for driving a vehicle tends to be increased, and the battery capacity is increasing accordingly. Such a trend toward an increase in size is due not only to an improvement in vehicle performance, but also because this type of vehicle has begun to be recognized socially, and high-end vehicles are being introduced in response to the growing needs of consumption. Furthermore, for motor-driven vehicles that have completed the social experiment stage, reduction of vehicle noise is a natural issue.

  In addition, a hybrid vehicle equipped with an internal combustion engine and an electric motor has a function of stopping idling of the internal combustion engine during a temporary stop. As a result, the noise level in the room is minimized during the suspension, and the fan unit noise and airflow noise stand out. Therefore, a cooling duct is required for the cooling duct to reduce such noise and improve the comfort of the vehicle and the quality of the vehicle.

  And since the fan in a fan unit is comprised with many blade | wings and the noise frequency band to generate | occur | produce ranges from about 1 kHz to 8 kHz, application of the sound-absorbing material which exhibits a sound-absorbing effect to the maximum in this frequency band is desirable. .

  However, the conventional cooling duct does not have a silencing function, and the attenuation amount of the airflow sound is not sufficient. As a simple method for attenuating the airflow sound, there is a method of controlling by reducing the rotational speed of the fan. However, in this method, since the cooling capacity is reduced, the cooling capacity must be prioritized even if the vehicle habitability is reduced.

  On the other hand, it is generally known that when a sound absorbing material is added in the duct, a silencing effect can be obtained in a high frequency band. For example, in Japanese Patent Application Laid-Open No. 2005-71759 (Patent Document 1), an intake / exhaust unit, a cooling pipe, and a curved portion of the cooling pipe are provided for absorbing sound generated by the intake / exhaust unit. A vehicle battery cooling structure including a sound absorbing means is disclosed. This document describes that a sound absorbing material made of a fiber material such as a polyethylene terephthalate nonwoven fabric is provided as an acoustic absorbing means in an opening part of which a part of a pipe line is notched.

  However, even if such a sound absorbing material is used, the noise reduction effect in the specific frequency band of the battery cooling fan airflow noise is not sufficient, and for example, it is difficult to obtain a high noise reduction effect with a small volume. Further, this cooling structure is a structure in which the inside and the outside of the cooling pipe line communicate with each other through a sound absorbing material. Accordingly, if the opening where the sound absorbing material is disposed is enlarged to increase the silencing effect, the cooling air leaks to the outside from the pipe line, so there is a limit to improving the silencing effect by expanding the opening. .

In general, as a method for reducing noise of a fan unit or the like, it is known to use a silencer such as a resonance type silencer or an expansion room type silencer. However, the resonance muffler exhibits a silencing effect only at a specific frequency, and particularly has a low silencing effect in a high frequency band. On the other hand, the expansion room type silencer exhibits a silencing effect in a wide frequency band compared to the resonance type silencer, but the duct inner diameter changes abruptly at the expansion silencer connection, thereby increasing the ventilation resistance and cooling. Wind flow rate is reduced. Further, in the expansion type silencer, if it is intended to obtain a higher noise reduction effect, it is necessary to secure a very large expansion room capacity, which goes against the requirement for downsizing the mounting space.
JP 2005-71759 A (Claim 1, paragraph numbers [0051] [0052] [0063])

  An object of the present invention is to provide a cooling silencer duct that can effectively reduce noise in a wide frequency band (such as airflow noise).

  Another object of the present invention is to provide a cooling silencer duct that has a high sound absorption capacity even when the air flow rate is high and can reduce airflow noise without lowering the cooling capacity.

  Still another object of the present invention is to provide a cooling silencer duct having high sound absorption capability and capable of effectively reducing airflow noise even with a small volume.

  As a result of intensive studies to achieve the above-described problems, the inventors of the present invention accommodate and hold a sound absorbing material in an expansion chamber (expansion chamber) formed in a part of the duct body in a duct for conducting cooling air. Thus, it was found that noise in a wide frequency band can be reduced, and the present invention has been completed.

In other words, the cooling silencer duct according to the present invention is a duct for conducting cooling air, the duct main body, an expansion chamber formed in the duct main body and expanded in the circumferential direction, and accommodated and held in the expansion chamber. Sound absorption material. The sound absorbing material may have a passage through which cooling air can pass, and the shape thereof may be annular. In this duct, the inner wall of the duct body and the inner wall of the sound absorbing material may be smooth and may be formed flush with each other. The sound absorbing material may be made of a plastic foam such as a polyurethane foam. As specific properties of such a sound absorbing material, the density of the sound absorbing material is about 40 to 48 kg / m ³ , and the air permeability according to JIS K6400-7 A method is 0.5 to 1.3 dm ³ / It may be about seconds. The cooling silencer duct of the present invention may be mounted on a fan unit having a fan and an electric motor that rotates the fan. In particular, the cooling silencer duct of the present invention is suitable as a battery cooling duct mounted on a vehicle such as an automobile.

  In the present invention, since the expansion chamber having a specific structure and the sound absorbing material accommodated in the expansion chamber are combined, when used as a duct for conducting cooling air, the sound absorbing action by the expansion chamber and the sound absorbing action by the sound absorbing material are used. Thus, airflow noise in a wide frequency band can be effectively reduced. In addition to high air permeability and excellent cooling capacity, airflow noise can be reduced without reducing the cooling capacity. Moreover, since the expansion chamber and the sound absorbing material are combined, the sound absorbing ability is high, and the air flow noise can be effectively reduced even with a small volume. Furthermore, in a duct provided with a resonance silencer, noise in a specific frequency band can be effectively reduced. Therefore, this duct is suitable as a battery cooling duct mounted on a vehicle such as an automobile.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as necessary.

[Silence duct for cooling]
FIG. 1 is a schematic cross-sectional view illustrating an example of a cooling silencer duct according to the present invention. The cooling silencer duct 1 is accommodated and held in a hollow cylindrical duct main body 2, an expansion chamber 3 formed in the duct main body 2 and radially expanded over the entire circumference, and the expansion chamber 3. The sound absorbing material 4 and the fitting portions 5 formed at both ends of the duct main body 2 are configured.

  The duct main body 2 has a hollow cylindrical (cylindrical) shape or a tube shape, and the duct main body 2 has a gas introduction port and an exhaust port for ventilating a cooling medium (usually air) through the air passage inside. have. The duct body 2 is formed of a soft polymer component such as a thermoplastic elastomer or rubber.

  In an expansion chamber 3 formed in a part of the duct body 2, a sound absorbing material 4 is accommodated in order to reduce airflow noise. The shape of the expansion chamber 3 is formed by extending the diameter of the duct body 2 over a part of the longitudinal direction of the duct body 2. For example, the expansion chamber 3 has a transverse section of the duct body 2. The shape, that is, the cross-sectional shape along the central axis direction (longitudinal direction) of the duct body 2 is a convex shape (square shape). In this example, the expansion chamber 3 is expanded about 1.3 to 2 times the inner diameter of the duct body 2 in the radial direction. On the other hand, in the axial direction, an expansion chamber is formed over a length of about 100 to 200 mm.

  The sound-absorbing material 4 is a ring-shaped (annular) sound-absorbing material formed of a polyurethane-based foam having open cells in order to enhance sound absorption, and is closely accommodated and held inside the expansion chamber 3. That is, since the outer diameter of the annular sound absorbing material 4 is substantially the same as the inner diameter of the expansion chamber 3, the sound absorbing material 4 is filled in close contact with the inner wall of the expansion chamber 3. As a result, the annular sound absorbing material 4 is firmly fixed to the duct main body 2 along with the ring-shaped structure, and the sound absorbing material 4 is prevented from dropping even when an air flow or vibration is applied.

  Furthermore, the inner diameter (the size of the hole) of the annular sound absorbing material 4 is substantially the same as the inner diameter of the duct body, for example, 1/2 to 2 times (particularly 1 / 1.5-1 to the inner diameter of the duct body). .5 times). Therefore, the inner wall 6 of the duct body 2 and the inner wall of the sound absorbing material 4 are smooth and flush with each other, so that the air permeability of the cooling medium (cooling air) can be improved.

  The fitting portions 5 at both ends of the duct body 2 are formed as mounting portions having a diameter larger than the diameter of the duct body 2 in order to connect to the suction port and the discharge port of the fan unit.

  In the cooling silencer duct shown in FIG. 1, the duct body is integrally formed, but the duct body may be composed of a plurality of duct members that can be attached to each other. Moreover, these duct members may be mutually attachable or separable in the axial direction (longitudinal direction) of the duct body. FIG. 2 is a schematic sectional view showing another example of the cooling silencer duct of the present invention. The cooling silencer duct shown in FIG. 2 differs from the cooling silencer duct shown in FIG. 1 in that the duct body is composed of two duct members that are separable from each other in the longitudinal direction. Specifically, the duct main body 22 of the cooling silencer duct shown in FIG. 2 has a duct member having a first extension portion (attached extension portion) 22a formed at one end portion, and the other end portion. And a duct member having a second expansion portion (mounting expansion portion) 22b that is formed and has an inner diameter substantially the same as the outer diameter of the first expansion portion 22a, with respect to the first expansion portion 22a. The second extension 22b can be attached or fitted. That is, the first expansion portion 22a and the second expansion portion 22b form an expansion chamber 23 for housing the sound absorbing material 24. In particular, this cooling silencer duct has a structure in which the duct main body 22 is separable in the axial direction in the expansion chamber 23, so that it is easy to accommodate the sound absorbing material in the expansion chamber at the time of manufacture. Specifically, for example, by mounting or fitting the duct member having the second expansion portion 22b in a state where the sound absorbing material 24 is inserted or mounted in advance on the duct member having the first expansion portion 22a, A cooling silencer duct can be constructed. The duct body may be structured to be separable in a direction perpendicular to the axial direction.

  In FIG. 2, a state in which the end surface of the first extension portion 22 a is not in contact with the inner wall of the second extension portion 22 b is illustrated, and the gap between the second extension portion 22 b and the sound absorbing material 24 is illustrated. There may be voids. In such a case, the space may be filled with a sound absorbing member, and the end portion of the first extension portion 22a is extended so as to be in close contact with the side wall of the second extension portion 22b. It is good also as a structure which does not produce a space | gap between them.

  In addition, although the first extension portion 22a and the second extension portion 22b are not shown, a protrusion is formed on one of the outer wall of the first extension portion 22a and the inner wall of the second extension portion 22b. On the other side, a recess in which the protrusion can be engaged or locked may be formed. The locking method between the first extension portion 22a and the second extension portion 22b is not particularly limited, and the projection or projection formed on the one side and the projection formed on the other and the projection in the axial direction. A locking mechanism may be configured by a guiding recess that guides and a fitting recess that extends in the circumferential direction from the guiding recess at the back of the guiding recess and accommodates or fits the protrusion. Further, the locking method may be a method using a reinforcing tool such as a screw.

  Furthermore, it is not the structure which fits the 1st expansion part 22a and the 2nd expansion part 22b, and the structure which can contact both the end surfaces by making both into the same diameter and not fitting may be sufficient. . In this case, in order to fix both and prevent leakage of the cooling medium, the contact portion may be sealed using a seal member or the like. Further, a flange portion may be formed at the end portion to facilitate contact or butting of both end faces and connection of the first and second extension portions.

  FIG. 3 is a schematic sectional view showing still another example of the cooling silencer duct of the present invention. In this example, the silencer has the same structure as the duct shown in FIG. 1 except that a resonance silencer 37 is further formed in addition to the expansion chamber 33 that houses and holds the sound absorbing material 34. The resonance silencer 37 includes a hollow neck that communicates with the duct body, and a resonance chamber that extends radially from the neck and extends in the longitudinal direction.

  The resonance silencer 37 is formed in parallel with the expansion chamber 33 in the axial direction of the duct body 32. In addition, the formation position of an expansion chamber and a resonance type silencer is not specifically limited, For example, an expansion chamber has a suction inlet side (duct upstream side) and a discharge outlet side (duct downstream side) rather than a resonance silencer. It may be arranged on either side.

  The resonance silencer is not particularly limited as long as the sound wave energy can be attenuated by resonance absorption, and may be a conventional resonance silencer, for example, a Helmholtz resonator. The Helmholtz resonator and the duct body are connected by a neck portion. Examples of the neck include a single hole type, a slit type, and an insertion type. The resonator can effectively mute a predetermined frequency by adjusting the inner diameter and length of the neck and the capacity of the resonator. Therefore, it is also effective to form a plurality of resonance silencers. For example, silencers having different frequency bands for silence may be provided.

  In other words, the cooling silencer duct forms a resonance silencer 37, so that in addition to the effect of the expansion chamber containing the sound absorbing material, noise generated due to air column resonance corresponding to its length (particularly, (A relatively low frequency band of less than 1 kHz) can also be suppressed.

  In the present invention, the shape of the duct main body is not particularly limited as long as it is a hollow shape capable of ventilating the cooling medium, and may be, for example, a hollow elliptic cylinder shape, a hollow polygonal column shape, or the like. Further, the duct body may be a straight tube, and may be bent or curved secondarily or tertiaryly. The inner diameter and length of the duct body can be selected according to the application. In the case of battery cooling use mounted on a vehicle, the inner diameter of the duct body is, for example, about 10 to 200 mm, preferably about 20 to 150 mm, and more preferably about 30 to 100 mm. The length of the duct body (full length including the expansion chamber) is, for example, about 50 to 1000 mm, preferably about 100 to 800 mm, and more preferably about 150 to 600 mm.

  The material of the duct body is not particularly limited as long as the cooling medium does not leak and can be molded. For example, various plastics (for example, olefin resins such as polyethylene and polypropylene, vinyl resins such as vinyl chloride resin) Resins, polyester resins such as polyethylene terephthalate, polyamide resins such as polyamide 6, thermoplastic resins such as polycarbonate resins; rubber or thermoplastic elastomers; polyurethane resins, and the like) can be used. Of these materials, soft resins such as thermoplastic elastomers and rubbers are preferable from the viewpoints of productivity, moldability, heat resistance, and the like. Examples of the thermoplastic elastomer include olefin elastomers, styrene elastomers, polyester elastomers, polyurethane elastomers, polyamide elastomers, and the like. Examples of the rubber include diene rubbers such as polybutadiene and polyisoprene, acrylic rubber, olefin rubbers such as ethylene-propylene rubber and ethylene-propylene-diene rubber, urethane rubber, silicone rubber, and butyl rubber.

  The shape of the expansion chamber is not particularly limited as long as the sound absorbing material can be accommodated and held. For example, the shape of the expansion chamber is not limited to the case where the cross-sectional shape along the axial direction of the duct body is a convex shape. Alternatively, it may be a dome shape), a mountain shape (triangular shape), or the like. In addition, although the expansion chamber 3 is extended and formed in the uniform magnitude | size over the perimeter of a part of duct main body 2, you may be expanded by the nonuniform magnitude | size.

  The size of the expansion chamber is not particularly limited as long as the sound absorbing material can exert a sound absorbing effect. For example, in the radial direction, the expansion chamber is 1/3 times or more (for example, 1/3 to 3 times) the radius of the duct body. ), Preferably 1/2 to 2 times, more preferably about 1 / 1.5 to 1.5 times the length of the expanded diameter. Further, in the axial direction, the length can be selected according to the length of the duct body, but is, for example, 1/10 to 1 / 1.2, preferably 1/5 to 1 / 1.3 with respect to the total length of the duct body. More preferably, the expansion chamber may be formed over a length range of about 1/3 to 1 / 1.5 times.

  The specific inner diameter and length of the expansion chamber can be selected according to the application. In the case of a battery cooling application mounted on a vehicle, the inner diameter of the expansion chamber is, for example, about 90 to 250 mm, preferably about 95 to 200 mm, and more preferably about 100 to 150 mm. The length of the expansion chamber is, for example, about 60 to 250 mm, preferably about 80 to 230 mm, and more preferably about 100 to 200 mm.

  The number of expansion chambers is not particularly limited, and a plurality of expansion chambers having different sizes (diameters and / or lengths) may be formed to adjust the sound absorption characteristics. That is, a plurality of expansion chambers may be formed according to the level of noise, the length of the duct, and the like. However, if the expansion chamber has the above-mentioned size, usually a single silencing effect can be obtained. Further, the formation position of the expansion chamber is not particularly limited, and may be formed at an appropriate position of the duct main body, for example, at the center of the duct main body. Also, the suction chamber side (the duct upstream side) and the discharge port side (the duct downstream side). It may be formed on at least either side.

  The shape of the fitting portion of the duct body is not limited to the above shape, and can be appropriately selected according to the shape and structure of the suction port and the discharge port of the fan unit, and the diameter of the fitting portion is larger than the diameter of the duct body. May be reduced. Moreover, you may form the latching or engagement part for connecting and fixing with a suction inlet and a discharge outlet as a fitting part. Further, the fitting portion of the duct body may be configured so that the fan unit and the battery unit can communicate with each other. For example, the duct body has a structure that can be connected to the fan unit suction port or discharge port and the battery unit discharge port or suction port. There may be.

  The shape of the sound absorbing material is not particularly limited as long as the cooling medium can be ventilated, but preferably has a passage through which cooling air can pass, and in particular, an annular shape (ring shape) having a vent hole in the center. Is preferred. The shape of the sound absorbing material is preferably the same shape as that of the expansion chamber. When both are made into the same shape, the sound absorption efficiency can be increased and the sound absorbing material can be stably accommodated and held in the expansion chamber. The inner diameter of the annular sound absorbing material (the size of the hole) may be different from the inner diameter of the duct main body, but is usually substantially the same size.

  As a material of the sound absorbing material, various materials having sound absorbing properties, for example, various porous flexible materials can be used. Specifically, fiber aggregates (natural fibers, semi-synthetic fibers such as acetate fibers, polyethylene fibers, polypropylene fibers, polyester fibers, polyamide fibers, synthetic fibers such as acrylic fibers, inorganic fibers such as glass fibers and carbon fibers) Fiber aggregates), non-woven fabrics (non-woven fabrics formed by needle punching, dry or wet methods, non-woven fabrics formed by fibers including heat-sealing fibers), woven fabrics, synthetic resin foams, and the like. These materials can be used alone or in combination of two or more. Among these materials, plastic foams such as polyolefin foams (polyethylene foam, foamed ethylene-vinyl acetate copolymer, etc.), polyurethane foams, and polyvinyl chloride foams from the viewpoint of sound absorption and moldability. The body is preferred.

  The cell structure of the plastic foam may be any of a closed cell structure, an open cell structure, or a combination of both, but a structure containing at least open cells is preferable from the viewpoint of improving sound absorption. The ratio of open cells is 60 to 100% (for example, 65 to 99.9%) in all bubbles, and preferably about 70 to 99%.

  Furthermore, in the present invention, among these plastic foams, it is suitable for mounting on a vehicle, for example, there is no risk of fluff falling off, high heat resistance, high dimensional stability, economical efficiency Polyurethane foam is particularly preferred because of its high point. The polyurethane foam is a conventional polyurethane foam, such as a polyisocyanate compound (for example, an aromatic diisocyanate such as phenylene diisocyanate or tolylene diisocyanate, an aliphatic diisocyanate such as hexamethylene diisocyanate, or an alicyclic diisocyanate such as isophorone diisocyanate. Or a terminal isocyanate group-containing urethane prepolymer and a polyol component (for example, an alkylene glycol such as ethylene glycol or tetramethylene glycol or an alkylene oxide adduct thereof, a polyether polyol or a polyester polyol) or a polyamine component (for example, ethylenediamine). Aliphatic polyamines such as diaminotoluene and diaminodiphenylmethane And etc.), blowing agents (water, carbon dioxide, air, and the like) volatile blowing agent, it may be a foam formed by the composition comprising a curing agent.

The density of the sound absorbing material can be selected from a range of about 10 to 100 kg / m ³ , and for example, ^{30 to} 70 kg / m ³ , preferably 40 to 48 kg / m ³ , more preferably 42 in order to improve the sound deadening property. it is a ~46kg / ^{m 3} about.

The air permeability of the sound absorbing material (method based on JIS K6400-7 A method) can be selected from a range of about 0.1 to ⁵ dm ³ / sec. For example, 0.3 to ² dm ³ for improving the sound deadening property. / Sec, preferably 0.4 to 1.4 dm ³ / sec, more preferably 0.5 to 1.3 dm ³ / sec (especially 0.6 to 1.2 dm ³ / sec).

  In the present invention, by controlling the density and air permeability of the sound-absorbing material, it is not necessary to dispose a bulky sound-absorbing material, making it possible to reduce the size of the silencer, and generating airflow noise in a wide frequency band with a small volume. Can be suppressed. Therefore, the characteristics of such a sound absorbing material are particularly useful in vehicle applications in which airflow noise in a wide frequency band from the battery cooling system greatly affects the sound transmission characteristics to the vehicle interior space.

  Furthermore, since the cooling sound deadening duct of the present invention accommodates and holds the annular sound absorbing material having such characteristics in the expansion chamber, the structure of the expansion chamber and the characteristics of the sound absorbing material are integrated into a small volume. Despite this, even airflow noise in a high frequency band (for example, about 1 to 8 kHz) can be effectively silenced and the cooling capacity of the cooling system is improved because the air flow rate of the cooling medium is not impaired. it can.

[Method of manufacturing a silencer duct for cooling]
The cooling silencer duct of the present invention can be produced by a conventional method. Specifically, the duct body can be obtained by a conventional molding method such as blow molding or injection molding. Of these molding methods, blow molding is widely used from the viewpoint of simplicity.

  When the sound absorbing material is a plastic foam, for example, a foam obtained by a method of foaming by mechanical stirring, a method of using a reaction product gas, a method of using a foaming agent, etc., is converted into a conventional molding method (continuous Foam molding or the like). The air permeability and density of the sound absorbing material are not particularly limited, but the foaming ratio is controlled by adjusting the component and amount of the foaming agent, the bubble opening diameter is controlled by adjusting the component and viscosity of the resin material, etc. Can be adjusted. In the case of fibers or nonwoven fabrics, for example, fibers may be obtained by a conventional spinning method and then molded using a binder resin or the like.

  As a method for accommodating the sound absorbing material in the expansion chamber of the duct main body, there is a method in which the sound absorbing material is composed of a plurality of sound absorbing elements, in addition to the method using the split type duct shown in FIG. For example, the plurality of sound absorbing elements may be equally divided (2 to 6 or the like) along the longitudinal direction of the duct body, and may be formed in a radial cross section. When the sound absorbing material is divided into a plurality of parts, the insertion into the expansion chamber is facilitated.

  The cooling silencer duct of the present invention is used for reducing airflow noise generated from a duct for conducting cooling air, for example, a fan unit (a fan unit having a fan and an electric motor that rotates the fan). It is mounted on a vehicle (transportation vehicle such as an automobile) and is used for reducing airflow noise generated from a fan unit used for cooling a battery (secondary battery, fuel cell, etc.). Further, the cooling silencer duct of the present invention is mounted on a use in which a large-capacity battery is mounted and a comfortable vehicle living space is required, for example, a hybrid vehicle having an internal combustion engine and an electric motor, or a fuel cell vehicle. This is particularly useful as a duct for cooling a battery.

  In order to describe the present invention more specifically and in detail, examples are shown below, but the present invention is not limited to these examples. Below, the detail of the polyurethane-type foam used as a sound-absorbing material and the performance evaluation method of a sound-absorbing material are shown.

[Polyurethane foam]
Product name "Achilles Aeron", manufactured by Achilles Co., Ltd .: Ether-based soft urethane foam with countless fine bubbles (continuous by urethanization reaction based on polyether polyol and polyisocyanate and carbon dioxide generation reaction by foaming agent) Foam manufactured by foaming method).

[Performance evaluation of sound absorbing material]
The relationship between the air permeability and the sound absorption rate in the polyurethane foam annular sound absorbing material having the structure shown in FIG. 2 was evaluated. The air permeability of the sound absorbing material was adjusted by changing the bubble opening diameter in the production of the polyurethane foam. The air permeability was measured in accordance with JIS K6400-7 A method, and the sound absorption characteristics were measured using a normal incidence sound absorption coefficient measuring device according to the 2-microphone method (ISO 10534-2). FIG. 4 shows the relationship between the air permeability and the sound absorption rate of the sound absorbing material. This sound-absorbing material showed high sound-absorbing characteristics in a range of air permeability of 0.5 to 1.3 dm ³ / sec. The density of the sound absorbing material having such air permeability was 40 to 48 kg / m ³ .

Example 1
Using a sound absorbing material made of polyurethane foam having a permeability of 0.7 dm ³ / sec, a battery cooling duct shown in FIG. 2 (inner diameter of the duct body: 60 mm, overall length of the duct body: 300 mm, inner diameter of the expansion chamber: 120 mm, Extended chamber length: 150 mm) was manufactured, and the noise attenuation characteristics were evaluated. FIG. 5 shows a partial perspective schematic view of a noise attenuation characteristic measuring apparatus. This apparatus is composed of a speaker 51 and an enclosure 52. A cooling silencer duct 53, which is a measurement object, is attached to the enclosure 52, and the sound pressure on the inlet side is measured by a microphone 54. The sound pressure on the outlet side is measured by the microphone 55. The noise attenuation characteristic is represented by a sound pressure ratio for each frequency band at a sound pressure level obtained by analyzing the sound pressure of the microphone 54 and the sound pressure of the microphone 55 by one-third octave. FIG. 6 shows the evaluation results of the noise attenuation characteristics. In the graph of FIG. 6, the vertical axis represents the sound pressure ratio (dB) between the microphone 54 and the microphone 55 as the noise attenuation characteristic. From this graph, it can be seen that the greater the noise attenuation value, that is, the sound pressure ratio, the higher the silencing effect.

Comparative Example 1
In the cooling silencer duct of Example 1, the noise attenuation characteristics of the cooling silencer duct without the sound absorbing material were evaluated. FIG. 7 shows the evaluation results of the noise attenuation characteristics. As is apparent from the graph of FIG. 7, the noise attenuation characteristics of the duct of Comparative Example 1 were lower than that of the duct of Example 1 in the high frequency band of 1 kHz or higher.

Example 2
A battery cooling duct was produced in the same manner as in Example 1 except that a sound absorbing material made of polyurethane foam having an air permeability of 1.5 dm ³ / sec was used. FIG. 8 shows the results of evaluating the noise attenuation characteristics of the obtained cooling silencer duct. As is apparent from the graph of FIG. 8, the duct of Example 2 shows good noise attenuation characteristics, but the noise attenuation characteristics in the high frequency band of 1 kHz or higher are slightly reduced as compared with the duct of Example 1. .

On the other hand, when the air permeability is reduced, the sound absorption rate of 4 kHz or more tends to decrease, as is apparent from the graph of FIG. There is a limit to reducing the air permeability because of loss. Therefore, the air permeability range of 0.5 to 1.3 dm ³ / sec is a range in which the performance of the expansion chamber as a silencer is not lost, and combined with the effect of the sound absorbing material, the silencing performance is maximized with a small volume. It can be seen that this is the range that can be fully demonstrated.

FIG. 1 is a schematic cross-sectional view illustrating an example of a cooling silencer duct according to the present invention. FIG. 2 is a schematic sectional view showing another example of the cooling silencer duct of the present invention. FIG. 3 is a schematic sectional view showing still another example of the cooling silencer duct of the present invention. FIG. 4 is a graph showing the relationship between the air permeability and the sound absorption rate of the annular sound absorbing material made of polyurethane-based foam. FIG. 5 is a partial perspective schematic view of an apparatus for measuring the noise attenuation characteristics of a cooling silencer duct. FIG. 6 is a graph showing noise attenuation characteristics of the cooling silencer duct of the first embodiment. FIG. 7 is a graph showing noise attenuation characteristics of the cooling silencer duct of Comparative Example 1. FIG. 8 is a graph showing noise attenuation characteristics of the cooling silencer duct of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cooling silencer duct 2 ... Silencer duct body 3 ... Expansion chamber 4 ... Sound absorbing material 5 ... Fitting part 6 ... Inner wall 37 ... Resonance type silencer

Claims (7)

And Dialog transfected body, is formed in the duct body, and an expansion chamber which extends in the circumferential direction, is composed of this expanded chamber accommodating retained sound absorbing material, a duct for conducting cooling air,
The duct body includes two duct members separable in the axial direction in the extension chamber, a first extension portion is formed at one end of the duct member, and a first extension portion is formed at the end of the other duct member. A second extension portion having an inner diameter substantially the same as the outer diameter of the one extension portion is formed, and the second extension portion can be attached to or fitted to the first extension portion;
A cooling silencer duct , wherein the sound absorbing material has an annular shape and has a passage through which the sound absorbing material can pass cooling air.   2. The cooling silencer duct according to claim 1, wherein the inner wall of the duct body and the inner wall of the sound absorbing material are smooth and are flush with each other.   2. The cooling silencer duct according to claim 1, wherein the sound absorbing material is made of a plastic foam. 4. The cooling silencer duct according to claim 3 , wherein the plastic foam is a polyurethane foam. Density of the sound absorbing material is 40~48kg / ^{m 3,} and a cooling muffler duct of claim 1, wherein air permeability in conformity with JIS K6400-7 A method is 0.5~1.3dm ³ / sec.   2. The cooling silencer duct according to claim 1, which is mounted on a fan unit having a fan and an electric motor for rotating the fan.   The noise-reduction duct for cooling according to claim 1, which is a duct for cooling a battery mounted on a vehicle.

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