Internal-combustion engines – Intake manifold
Reexamination Certificate
2000-11-29
2003-04-29
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Intake manifold
C123S184610, C181S214000
Reexamination Certificate
active
06553953
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a suction duct as a passageway for supplying the air to an engine, and particularly relates to a suction duct in which noise at the time of sucking the air is lowered.
BACKGROUND ART
In a suction system of a motorcar engine, there is a defect that noise is generated in an air cleaner hose, a suction duct, or the like, when the air is sucked. This suction noise is harsh particularly at a low engine speed. Therefore, a side branch
201
and/or a resonator
202
is hitherto provided in a suction duct
200
as shown in
FIG. 25
, so as to reduce noise at a specific frequency calculated on the basis of Helmholtz resonance theory and so on.
The side branch
201
is, however, about 30 cm long if it is the longest, and the resonator
202
has a volume of 14 liters if it is the largest. Thus, the space in an engine room occupied by such noise absorption equipment increases and results in a defect that the degree of freedom to mount other parts is lowered.
Therefore, JP-U-64-22866 discloses a method in which an orifice is disposed in a suction duct, and suction noise is reduced by reducing the suction. By narrowing a suction passageway thus, acoustic mass increases so that suction noise in a low tone range can be reduced.
In addition, JP-U-3-43576 discloses a suction noise reduction apparatus which comprises two suction ducts connected in parallel to an air cleaner case, branch ducts branching from the two suction ducts respectively, and a common resonator to which all the branch ducts are coupled. The suction noise reduction apparatus further comprises an on-off valve which selectively opens in accordance with the driving condition and which is provided on the upstream side of a branch duct connecting portion in one of the suction ducts.
According to the apparatus disclosed in this publication JP-U-3-43576, the on-off valve is controlled in accordance with an engine speed so that the number of suction ducts is switched to one or two. Thus, the quantity of sucked air can be controlled in accordance with the engine speed, and suction noise can be reduced.
In the above-mentioned method in which the suction passageway is narrowed, however, there is a defect that the quantity of sucked air is insufficient at a high engine speed so that the output is lowered.
In addition, in the apparatus disclosed in this publication JP-U-3-43576, an electronic control circuit, an electromagnetic on-off valve, a diaphragm actuator, or the like, is used for driving the on-off valve. Those are not preferable in terms of the cost. In addition, since an electronic control circuit, an electromagnetic on-off valve, or the like, is necessary, the apparatus becomes not only complicated and expensive but also large in the number of man-hour for maintenance.
DISCLOSURE OF THE INVENTION
The present invention was developed in the light of such circumstances. It is an object of the present invention to provide a suction duct in which without narrowing a suction passageway and without using any electronic control circuit, any electromagnetic on-off valve, or the like, suction noise at a low engine speed can be lowered with a simple and low-priced configuration, and a sufficient quantity of the air can be supplied at a high engine speed.
A suction duct according to the present invention is characterized in that at least a part of a duct wall is formed out of a molded body of non-woven fabric in a suction duct disposed between an outside air intake of a motorcar and an intake manifold of an engine.
PET (polyethylene terephthalate) fibers, PP (polypropylene) fibers, PE (polyethylene) fibers, etc. can be used as fibers constituting this non-woven fabric. In view of fiber variation, quality, price, and so on, however, it is preferable that PET fibers are used.
In addition, it is preferable that the permeability per 1m
2
of the molded body in the case of air with a pressure difference of 98 Pa is not larger than 6,000 m
3
/h in the above-mentioned suction duct. That is, “permeability” herein means the quantity of the air passing through a test specimen in terms of unit area and unit time when the pressure difference between two chambers sectioned by the test specimen is set to be 98 Pa.
The above-mentioned suction duct is preferably configured so that the whole of the duct wall is formed out of the molded body, the non-woven fabric contains high-melting fibers of high-melting thermoplastic resin and low-melting fibers of low-melting themoplastic resin having a lower melting point than that of the high-melting fibers, and the ratio of the low-melting fibers to the non-woven fabric is higher than that of the high-melting fibers.
In the case where the suction duct is molded by compression molding, “low-melting” herein means that a melting point is lower than the temperature in the compression molding, while “high-melting” means a melting point is higher than the temperature in the compression molding.
In addition, the suction duct may be configured so that the whole of the duct wall is formed out of the molded body, the non-woven fabric contains thermoplastic fibers constituted by a core material consisting of high-melting thermoplastic resin and a coating layer applied onto the surface of the core material and consisting of low-melting thermoplastic resin having a lower melting point than that of the core material, and the volume of the coating layer is larger than that of the core material.
The molded body of the above-mentioned suction duct may be formed out of non-woven fabric having a functional layer to which a predetermined function is given. Preferably, this functional layer is a water-repellent layer.
Further, according to the present invention, there is formed a suction duct which comprises a first segment having a substantially semicircular sectional shape and constituted by a molded body made of synthetic resin and a second segment having a substantially semicircular sectional shape and constituted by a molded body made of non-woven fabric, and in which the first and second segments are coupled integrally with each other.
The present inventors made researches earnestly on the relationship between the material of a suction duct and the noise generated therefrom. As a result, it was found out that, when a duct wall was formed out of permeable material having predetermined permeability, it was difficult to generate a standing wave so that suction noise was reduced conspicuously. The present invention was developed on the basis of such a discovery.
Noise generated at the time of air suction is chiefly caused by an acoustic standing wave generated inside a suction duct. The frequency of the standing wave depends on the length, diameter and material of the suction duct, and so on. Therefore, according to the present invention, at least a part of a duct wall of a suction duct is formed out of a molded body of non-woven fabric.
The reason why suction noise is reduced by forming a duct wall out of a non-woven fabric molded body is unknown in detail. However, the following three reasons are considered.
(i) Since non-woven fabric is an elastic body, it has a vibration damping effect, so that an acoustic wave is restrained from being generated by the vibration of the duct wall.
(ii) The energy of an acoustic wave entering a large number of gaps among fibers of the non-woven fabric is weakened by the effect of the viscosity and heat conduction of the gaps. In addition, the fibers themselves resonate with the fluctuation of the sound pressure so that the sound energy attenuates.
(iii) Since at least a part of the duct wall has a certain measure of permeability, an acoustic wave partially passes through the duct wall so that a standing wave is restrained from being generated.
It is considered that suction noise is reduced by the synergistic effect of these reasons.
However, when the permeability of the non-woven fabric molded body is too high, there is a defect that an acoustic wave inside the suction duct penetrates the duct wall and leaks to the outside so that noise increases. It
Fujihara Kazuo
Hattori Masaru
Hirose Yoshikazu
Ishihara Hidetoshi
Ito Kuniyasu
Argenbright Tony M.
Harris Katrina B.
Posz & Bethards, PLC
Toyoda Gosei Co,., Ltd.
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