Rotary kinetic fluid motors or pumps – With sound or vibratory wave absorbing or preventing means...
Reexamination Certificate
2000-02-03
2002-05-21
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With sound or vibratory wave absorbing or preventing means...
C415S228000, C416S16900R, C416S189000
Reexamination Certificate
active
06390770
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fan apparatus including a fan revolved to produce a flow of air, and more particularly to a fan apparatus capable of reducing noise generated due to the revolution of the fan, and a shroud for use with the fan apparatus.
BACKGROUND ART
Heretofore, a side-branch type pulsation reducing apparatus disclosed in JP, A, 9-425756, for example, has been known as a prior-art apparatus in which a small stream path branched from a main stream of a fluid induced by a fluid machine, and a stream going through the branched stream path and back is caused to interfere with the main stream, thereby properly modifying the form of a wave propagating in the main stream.
The disclosed apparatus is installed in, e.g., a construction machine such as a hydraulic excavator. A bottom-equipped side branch is branched from and connected to a delivery line of a hydraulic pump driven by an engine. The pulsation of a hydraulic fluid delivered from the hydraulic pump propagates through the delivery line and a passage in the side branch as well. The pulsation of the hydraulic fluid propagating through the side branch passage is reflected by a wall surface at the end of the side branch, and returns to the delivery line again through the side branch passage. By previously deciding a particular frequency of the pulsation wave to be reduced and appropriately adjusting a length of the side branch passage depending on the particular frequency, therefore, the pulsation wave of the hydraulic fluid, which goes through the side branch passage and returns to the delivery line, is caused to interfere with the pulsation wave propagating straightforward through the deliver line in such a relationship that the hills of one wave collide with the valleys of the other wave. Of the pulsation of the hydraulic fluid advancing straightforward through the deliver line, the pulsation of the particular frequency can be thereby reduced primarily. In this case, the particular frequency is set to, e.g., a pump pulsation frequency (150-1000 hertz) that corresponds to the engine revolution speed of a hydraulic excavator during ordinary excavating work.
On the other hand, an engine apparatus installed in a construction machine and a motor vehicle, for example, comprises an engine, a rotary shaft to which a driving force of a crankshaft of the engine is transmitted, a fan fitted over the rotary shaft, a heat exchanger disposed in front (upstream) of the fan, and a shroud fixed downstream of the heat exchanger. An propeller fan is usually employed as the fan in many cases, and the heat exchanger includes a radiator to which engine cooling water is supplied in a circulating manner. When the engine is driven, rotation of the crankshaft is transmitted to the rotary shaft to revolve the fan, whereupon air is introduced to the heat exchanger from the upstream side for cooling the heat exchanger. The air having passed the heat exchanger is introduced to the suction side of the fan through the shroud and flows into the fan. Then, the air flowing out of the fan further cools the engine.
It has been hitherto known that noise occurs in the above engine apparatus due to revolution of the fan. One conceivable method of reducing the noise is to apply the structure of the above apparatus disclosed in JP, A, 9-42576 to the fan in the engine apparatus. Specifically, by providing a side branch which has a predetermined length and is branched from a wall surface of the shroud defining an air flow passage in an enclosed space extending from the heat exchanger to the fan, a sound wave going through a side branch passage and returning to the shroud is caused to interfere with a sound wave propagating straightforward downstream in the shroud. Of the noise propagating in the shroud, the noise component of a particular frequency can be thereby reduced primarily. In this case, the particular frequency is set to, e.g., a frequency of the fan rotary shaft that corresponds to the engine revolution speed of a hydraulic excavator during ordinary excavating work.
DISCLOSURE OF THE INVENTION
However, the inventors of this application have found that the noise cannot be reduced sufficiently by applying the structure of the above apparatus disclosed in JP, A, 9-42576 to the fan in the engine apparatus. The reasons are as follows.
In the structure introducing air to the suction side of the fan through the shroud like the above engine apparatus, there are two main noise sources. The first is wind chopping noise generated from the ends of fan blades upon the blades revolving while chopping the air flow (referred to simply as wind chopping noise hereinafter). The wind chopping noise occurs regardless of whether the shroud is provided or not. The second is collision noise generated from the wall surface of the shroud upon an air flow colliding against the shroud wall surface after coming out of the fan (referred to simply as collision noise hereinafter). Of those noise sources, the collision noise is dominant in the structure introducing air to the suction side of the fan through the shroud. The side branch type structure such as employed in the apparatus of JP, A, 9-42576 intends to reduce the wind chopping noise primarily, and therefore cannot reduce the collision noise. Thus the noise cannot be reduced sufficiently as a whole.
In consideration of the above result, the inventors of this application have found that it is effective to damp a radial component of the air flow coming out of the fan for reducing the collision noise.
An object of the present invention is to provide a fan apparatus capable of sufficiently reducing noise generated due to revolution of a fan, and a shroud for use with the fan apparatus.
To achieve the above object, the present invention provides a fan apparatus comprising a fan having a plurality of blades and producing an air flow with revolution thereof, and at least one shroud disposed upstream of the fan and introducing the air flow to the suction side of the fan, wherein damping means for taking in the air flow coming out of the fan and damping a radial component of the air flow under an interference action is provided in an outer periphery side of the fan.
The air flow produced with the revolution of the fan is introduced to the suction side of the fan through the shroud, and flows out to the blown-off side of the fan. At this time, noise generates from two main noise sources, i.e., wind chopping noise generated from the ends of fan blades upon the blades turning while chopping the air flow with the revolution of the fan, and collision noise generated from a wall surface of the shroud upon the air flow colliding against the shroud wall surface after coming out of the fan. Of those noise sources, the latter is dominant. Usually, a downstream portion of the shroud is arranged in overlapping relation to the radial outer periphery side of the fan to some extent, and the air flow coming out of the fan radially outward collides against the downstream portion of the shroud, thereby generating the collision noise.
Taking into account the above, in the present invention, the damping means is provided in the outer periphery side of the fan to take in the air flow coming out of the fan and to damp the radial component of the air flow under an interference action, whereby the collision of the air flow against the shroud wall surface is moderated. It is therefore possible to reduce the collision noise that is the dominant noise source, and to reduce the noise generated due to the revolution of the fan sufficiently.
In the above fan apparatus, preferably, the damping means includes at least one bottom-closed pipe disposed with the open side thereof facing the outer periphery side of the fan.
Also, to achieve the above object, the present invention provides a fan apparatus comprising a fan having a plurality of blades and producing an air flow with revolution thereof, and at least one shroud disposed upstream of the fan and introducing the air flow to the suction side of the fan, wherein the fan apparatus includ
Hitachi Construction Machinery Co. Ltd.
Look Edward K.
Mattingly Stanger & Malur, P.C.
Nguyen Ninh
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