JPH1193670A - Fan shroud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fan shroud for effectively reducing fan noise to be generated caused by rotation of a cooling fan and vibration of the fan shroud. SOLUTION: A fan shroud has a double pipe structure composed of an inner pipe 41 and an outer pipe 42 and is divided into interference chambers 48 by partition plates 41 so that the circumferential pipe length LF in a double pipe may be one quarters of the specified acoustic wave length. Opening parts 49 are provided on the inner pipe 41 of respective interference chambers 48. Since acoustic waves entered from the opening parts 49 are reflected while the phase is reversed at 180 deg. after the acoustic wave is transmitted by one quarters length, noise having the specified acoustic wave length is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan shroud for a cooling fan installed in a construction machine or a large vehicle.

[0002]

2. Description of the Related Art FIG. 5 shows a schematic layout of peripheral devices of a fan shroud used in construction machines such as hydraulic excavators and crawler cranes. In FIG. 5, the cooling fan 1
1 is a suction fan directly connected to the prime mover 12,
A radiator 13 is disposed in front of the radiator 13. A fan shroud 14 is attached to a side surface of the radiator 13 to form an air passage between the cooling fan 11 and the radiator 13. When the prime mover 12 is driven and the cooling fan 11 rotates, the cooling air sucked in from the front of the radiator 13 passes through the radiator 13, passes through the inside of the fan shroud 14, and is discharged to the rear of the cooling fan 11. . At that time, when the cooling fan 11 rotates, fan noise such as fan rotation noise depending on the number of rotations, wind noise, and turbulent noise due to a turbulent flow of air along the fan shroud 14 is generated.

[0003] On the other hand, in recent years, there has been a movement to regulate noise of construction machines in order to preserve the living environment of residents. For example, noise evaluation at the maximum no-load rotation speed of the engine, that is, work in place of stationary noise evaluation has been performed. Noise assessment has also been adopted. This evaluation evaluates the noise in the dynamic state of the body of a construction machine, in fact, the ambient noise during a simulated work load such as excavation, running, turning, etc. Has been requested. In response to such a request, fan noise is measured as shown in FIG. 6, for example, as described in JP-A-7-11956.
A method has been proposed in which a sound absorbing material 15 is attached to the inner surface of the fan shroud 14 to absorb fan noise.

[0004]

However, the magnitude of these fan noises is, as shown in FIG. 5, the ratio L2 of the cover length L2 of the fan shroud 14 to the cooling fan 11 and the blade length L1 of the cooling fan 11. / L1, the size of the tip clearance L3 which is the gap between the blade tip of the cooling fan 11 and the fan shroud 14, the fan shroud 1
It depends on many factors, such as the shape of 4 and the 11 shape of the cooling fan. Therefore, in order to effectively reduce the fan noise generated by such factors, it is not sufficient to use only the sound absorbing material.

[0005] In addition to the fan noise such as the above-described fan rotation noise, wind noise, and turbulent noise on the shroud wall surface, the fan noise may be caused by vibration of the fan shroud 14 as a noise source. Such vibration of the fan shroud 14 is caused by the driving of the
2 propagates to the fan shroud 14 via the frame, and the rotation of the cooling fan 11 causes the cooling fan 1 to rotate.
This is caused by the periodic pressure fluctuation of the air near 1. Therefore, the vibration frequency includes a relatively low frequency of about several hundred Hz. Thus, in particular, when the vibration frequency of the fan shroud 14 matches its natural frequency, the fan shroud 14 emits a resonance sound, resulting in a significant increase in fan noise.

[0006] Even if a relatively low-frequency noise caused by the vibration of the fan shroud 14 is to be absorbed by attaching a sound absorbing material to the surface of the fan shroud 14 described above, the sound absorbing material is not suitable for its characteristics. This is effective when absorbing relatively high frequency noise of HZ or higher, and has a small sound absorbing effect for low frequency noise. Further, in order to prevent the resonance of the fan shroud 14, it is conceivable to increase the rigidity of the fan shroud 14, but merely increasing the rigidity is not preferable because it increases the weight.

An object of the present invention is to provide a fan shroud that effectively reduces fan noise generated by the various factors described above.

[0008]

[Means for Solving the Problems]

(1) Referring to FIGS. 1 to 3 showing one embodiment, the invention of claim 1 is directed to a radiator 3 and a cooling fan 1.
And a fan shroud 4 that forms a passage for cooling air that exchanges heat with cooling water circulating in the radiator 3.
Applied to The above object is achieved by providing a chamber 48 in which sound waves of the cooling air flowing between the cooling fan 1 and the sound wave are made incident and interfere or resonate with each other to reduce noise caused by the cooling air. (2) The invention according to claim 2 is applied to the fan shroud 4 which is disposed between the radiator 3 and the cooling fan 1 and forms a passage for cooling air that exchanges heat with cooling water circulating in the radiator 3. Then, an inner pipe 41 that forms a cooling air passage between the cooling pipe 1 and the cooling fan 1, an outer pipe 42 disposed as a double pipe with respect to the inner pipe 41, and the inner pipe 41 and the outer pipe 42.
A plurality of closed spaces divided at predetermined angles in the circumferential direction in the annular space between the cooling fan 1 and the opening 49, into which sound waves of cooling air passing between the cooling fan 1 and the cooling space 1 enter. The above object is achieved by providing a plurality of chambers 48 for reducing noise of cooling air by interfering or resonating incident sound waves. (3) In the invention of claim 3, at least two rows of the chambers 48 are provided in the direction in which the cooling air flows, and the frequency bands of the sound waves to be reduced in each of the chambers are shifted from each other.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. However, the present invention is not limited to this.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic layout diagram of a fan shroud and its peripheral components. In FIG. 1, a rotating shaft 1a of a cooling fan 1 is connected to a prime mover 2 via a belt, a pulley, and a clutch (not shown). The cooling fan 1 is a suction fan, and a radiator 3 is disposed in front of the cooling fan. Between the radiator 3 and the cooling fan 1, a fan shroud 4 whose detailed shape is shown in FIGS. 2 and 3 is arranged to form a cooling air passage. One end of the fan shroud 4 is attached to a side surface of the radiator 3, and the other end is disposed outside the outer periphery of the cooling fan 1. The ratio L2 of the cover amount L2 between the cooling fan 1 and the fan shroud 4 to the blade length L1 of the cooling fan 1
/ L1 and the size of the tip clearance L3 in the blade height direction of the fan shroud 4 and the cooling fan 1 are not directly related to the present invention, and these values are optimized in terms of noise, efficiency, and the like. It is determined.

Next, the detailed shape of the fan shroud 4 will be described with reference to FIGS. FIG. 2 is an enlarged view of the fan shroud 4 shown in FIG. 1, and FIG.
FIG. 3 is a sectional view taken along line I-III. As shown in FIGS. 2 and 3, the fan shroud 4 includes an inner pipe 41 having a different inner diameter D1 and D2 in the front-rear direction and a length W, and an outer diameter D3 and a length W outside the inner pipe 41. The outer pipe 42 has a double pipe structure, and the inner pipe 41 and the outer pipe 42 are each formed by bending a flat plate into a circular shape. Closed plates 43 and 44 are joined to the front and rear end surfaces of the inner tube 41 and the outer tube 42, and the cross section of the double tube has a box shape surrounded by the inner tube 41, the outer tube 42, and the closed plates 43 and 44. doing. As shown in FIG. 2, the inner space of the double pipe is composed of two intermediate plates 45 having an inner diameter D1 and an outer diameter D3 each having an outer peripheral edge and an inner peripheral edge joined to an inner pipe 41 and an outer pipe 42, respectively.
Thereby, it is divided into three donut-shaped spaces of a front room 46a, an intermediate room 46b, and a rear room 46c. That is, three rows of donut-shaped chambers are juxtaposed in the direction in which the cooling air flows. The anterior chamber 46a further includes, as shown in FIG.
6 and a plurality of partitioning plates 47 attached to the closing plate 43 and the intermediate plate 45, are equally divided in the circumferential direction to form six interference chambers 48 having a pipe length LF inside the double pipe. In the interference chamber 48 formed by the plurality of partition plates 47 as described above, one opening 49 is provided in the inner pipe 41 near the partition plate 47, and each interference chamber 48 is provided through the opening 49. It communicates with an air passage of cooling air passing inside the inner pipe 41. Although not shown, the intermediate chamber 46b and the rear chamber 46c are equally divided in the circumferential direction by the partition plate 47 similarly to the front chamber 46a, and interference chambers having pipe lengths of LM and LR are formed. ing.

Next, the operation of this embodiment will be described. When the prime mover 2 is driven and the cooling fan 1 rotates,
Air is sucked in from the front of the radiator 3. This air becomes cooling air and exchanges heat with the motor cooling water flowing inside the radiator 3 to lower the temperature of the cooling water. The heat-exchanged cooling air passes through the inner pipe 41 of the fan shroud 4 and is discharged to the rear of the cooling fan 1. in this way,
When the cooling air passes through the inside of the fan shroud 4, it becomes a sound wave and enters the interference chamber 48 through the opening 49. The sound wave that has entered the interference chamber 48 propagates in the interference chamber 48 in the circumferential direction, is reflected by the end partition 47, and has a phase of 18
It reverses by 0 ° and propagates again toward the opening 49. Therefore, each of the pipe lengths LF, LM, LR is 1/1 of the sound wave to be silenced.
If the wavelength is set to each of the four wavelengths, noise at a predetermined frequency is muted by interference between the incident wave and the reflected wave. In this case, for example, the pipe lengths LF, L are set so that the wavelengths are 1/4 wavelength of the primary, secondary, and tertiary natural frequencies of the fan shroud 4.
If M and LR are set respectively, it is possible to reduce low-frequency resonance sound caused by vibration of the fan shroud 4.

As described above, according to the present embodiment, the fan shroud 4 has a double-pipe structure, and its internal space is divided into a plurality of chambers by the partition plate 47 and the intermediate plate 45, and the length of the pipe is predetermined. Since the interference chamber is formed so as to have a quarter wavelength of the frequency, even low-frequency noise can be reduced. Further, the fan shroud 4 has a structure reinforced by a plurality of partition plates 47 and intermediate plates 45, and its rigidity is increased, so that vibration and noise of the fan shroud 4 are reduced.

In the above embodiment, the fan shroud 4
Has been described as a so-called interference type silencing structure, but a resonance type silencing structure may be employed as shown in FIG. FIG.
It is a schematic sectional drawing of fan shroud 4 provided with the resonance type noise reduction structure. In FIG. 4, the internal space of the fan shroud 4, which has a double-pipe structure as in the case of the interference-type silencing structure shown in FIGS. 2 and 3, is divided into three parts by a plurality of intermediate plates 45 in the front-rear direction. A chamber 46b and a rear chamber 46c are formed. These front room 46a, intermediate room 46b, rear room 4
6c is also divided in the circumferential direction by a partition plate (not shown) so as to form a resonance chamber having a predetermined volume V. The inner tube 41 of each resonance chamber thus formed is provided with a neck 50 having a plate thickness t and an opening area S to form a resonator. The resonance frequencies determined by the volume V, the plate thickness t, and the opening area S of the resonator are the resonance provided in the front chamber 46a, the resonator provided in the intermediate chamber 46b, and the resonance provided in the rear chamber 46c. The values are different from one another in each case. When sound waves enter such a resonator, the amplitude of air in the neck at a predetermined resonance frequency increases, and friction occurs, so that only energy near this frequency is silenced. Therefore, by appropriately setting the volume V, the plate thickness t, and the opening area S, a predetermined noise can be suppressed.

In the above embodiment, the internal space of the double pipe is divided into three in the axial direction. However, the present invention is not limited to this. In some cases, it is not necessary to divide equally. further,
The pipe length may be set so as to reduce not only the fan shroud resonance sound but also fan noise such as fan rotation noise, wind noise, and turbulent noise on the fan shroud wall surface. Furthermore, a sound absorbing material may be attached to the double pipe surface. It is also conceivable that the shape of the air passage is formed in a so-called bellmouth shape so as to avoid a sudden change in the shape of the air passage of the fan shroud and to provide a smooth air flow. Furthermore, although the cooling fan is a suction fan, the fan shroud can have the same configuration even if it is a push-in fan in which a cooling fan is installed in front of the radiator. Furthermore, the interference type silencing structure and the resonance type silencing structure may be combined to simultaneously perform silencing of a plurality of acoustic frequencies. Further, the shapes and the number of intermediate plates and partition plates may be set so that the natural frequency of the fan shroud has a predetermined value. Furthermore, the present invention can also be applied to a system in which an oil cooler is installed in a stage preceding a radiator.

[0016]

As described above in detail, according to the first aspect of the present invention, since the interference chamber or the resonance chamber is provided in the fan shroud, the predetermined sound can be reduced. According to the second aspect of the present invention, the fan shroud has a double pipe structure, and the inside of the double pipe is divided so as to have a predetermined angle in the circumferential direction. Fan noise can be effectively reduced. Furthermore, according to the third aspect of the present invention, the interference chamber or the resonance chamber is provided in two or more rows in the flow direction of the cooling air.
Noise at a plurality of acoustic frequencies can be reduced at the same time.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram of a fan shroud according to an embodiment and peripheral components thereof.

FIG. 2 is an enlarged view of a fan shroud according to the embodiment.

FIG. 3 is an enlarged view of a fan shroud according to the embodiment, and is a cross-sectional view taken along line III-III of FIG. 2;

FIG. 4 is an enlarged view of a fan shroud as a modification according to the present embodiment.

FIG. 5 is a schematic layout diagram of a fan shroud and its peripheral parts according to the related art.

FIG. 6 is a diagram in which a sound absorbing material is attached to a fan shroud according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cooling fan 3 Radiator 4 Fan shroud 41 Inner tube 42 Outer tube 48 Interference room, resonance room 49 Opening

Claims (3)

[Claims] 1. A fan shroud arranged between a radiator and a cooling fan and forming a passage of a cooling air for exchanging heat with cooling water circulating in the radiator, wherein a sound wave of the cooling air flowing between the cooling fan and the cooling fan. A fan shroud characterized by comprising a chamber for receiving noise and interfering or resonating the sound wave to reduce noise due to the cooling wind. 2. A fan shroud which is arranged between a radiator and a cooling fan and forms a passage of cooling air for exchanging heat with cooling water circulating in the radiator, wherein the cooling air flows between the cooling fan and the cooling fan. An inner tube forming a passage; an outer tube arranged as a double tube with respect to the inner tube; and a plurality of circumferentially divided predetermined angles in an annular space between the inner tube and the outer tube. A plurality of chambers each having an opening through which sound waves of cooling air passing between the cooling fan and the cooling fan enter, and interfering or resonating sound waves incident from the opening to reduce noise of the cooling air. A fan shroud comprising: 3. The apparatus according to claim 1, wherein at least two rows of the chambers are provided in a direction in which the cooling air flows, and frequency bands of sound waves to be reduced in the respective chambers are shifted from each other. Fan shroud.