Internal-combustion engines – Intake manifold
Reexamination Certificate
2001-05-17
2003-09-23
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Intake manifold
C123S184570
Reexamination Certificate
active
06622680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air intake duct as a passageway for supplying the air to an engine, and a method for manufacturing such an air intake duct, and particularly relates to an air intake duct in which noise is reduced at the time of air intake and a method for manufacturing such an air intake duct. The present invention also relates to a method for welding resin molded pieces with each other by use of a hot plate, and particularly relates to a hot plate welding method for welding molded pieces which are made of different kinds of resins different in melting point, by use of a hot plate.
The present application is based on Japanese Patent Applications No. 2000-144930, 2000-156420, and 2000-217330, which are incorporated herein by reference.
2. Description of the Related Art
In an air intake system of a motorcar engine, there is a problem that noise is generated in an air cleaner hose, an air intake duct, or the like, at the time of air intake. Such an air intake noise is harsh on the ears particularly at the time of a low engine speed. Conventionally, therefore, a side branch
101
and/or a resonator
102
are provided in an air intake duct
100
so as to reduce noise of a specific frequency calculated on the basis the Helmholtz resonance theory or the like, as shown in FIG.
17
.
However, the side branch
101
may reach about 30 cm in length at the longest, and the resonator
102
may reach 14 liters in volume at the largest. Thus, there is a problem that such a noise absorbing apparatus occupies a large space in an engine room so as to reduce the degree of freedom in mounting other parts.
Therefore, Unexamined Japanese Utility Model Publication No. Sho. 64-22866 discloses that an orifice is disposed in an air intake duct and an air intake passageway is narrowed in the position of the orifice so as to reduce air intake noise. By narrowing the air intake passage way in such a manner, the acoustic mass increases so that the air intake noise in a bass range can be reduced.
In addition, Unexamined Japanese Utility Model Publication No. Hei. 3-43576 discloses an air intake noise reducing apparatus comprising two air intake ducts connected in parallel in an air cleaner case, branch ducts branching from the two air intake ducts respectively, a common resonator to which the respective branch ducts are connected, and an on-off valve provided on the upstream side of a connection portion of a branch duct in one of the air intake ducts, the on-off valve being opened selectively in accordance with the running condition of an engine.
According to the apparatus disposed in the aforementioned 3-43576, the on-off valve is controlled to change over the number of air intake ducts between one and two in accordance with the engine speed. Thus, the intake air quantity can be controlled in accordance with the engine speed, and the air intake noise can be reduced.
However, in the aforementioned method in which the air intake passageway is narrowed, there is a problem that the intake air quantity is insufficient at a high engine speed so that the output is lowered.
In addition, in the apparatus disclosed in the aforementioned 3-43576, an electronic control circuit, an electromagnetic on-off valve, a diaphragm actuator, or the like, is used to drive the on-off valve. That is not desirable from the point of view of the cost. In addition, because the electronic control circuit, the electromagnetic on-off valve, or the like, is required, the apparatus becomes so complicated that it is not only expensive but also considerable in the number of man-hour for maintenance.
Therefore, Unexamined Japanese Patent Publication No. Hei. 11-343938 discloses an air intake duct formed of non-woven fabric containing thermoplastic resin fibers by thermal compression molding. By forming an air intake duct out of a non-woven molded body in such a manner, it is possible to reduce the air intake noise effectively. In addition, in the same publication, there is a statement that the following three can be considered as the reason why the air intake noise is reduced, and it is considered that the air intake noise is reduced by the synergistic effect of the three reasons.
(1) Since the non-woven fabric is an elastic body, the non-woven fabric has a vibration damping operation, and sound waves are restrained from being generated by vibrations of duct walls.
(2) Energy of sound waves entering a large number of gaps among the fibers of the non-woven fabric is weakened by the operation of the viscosity and heat conduction of the gaps, and the fibers themselves resonate with the fluctuation of sound pressure so that the sound energy is attenuated.
(3) At least a part of the duct walls have some degree of permeability. Since a part of the sound waves pass such duct walls, stationary waves are restrained from being generated.
There is, however, a problem that the non-woven fabric molded body is so expensive, in comparison with general resin molded bodies, that the air intake duct formed of the non-woven fabric molded body becomes much more expensive than conventional air intake ducts.
By the way, resin molded articles are used in various fields because they have properties that they do not corrode or rot as metal or wood does, and they are inexpensive and light in weight. In addition, most of resin molded articles are formed of thermoplastic resin in order to save global resources by recycling. Then, various molding methods such as compression molding, transfer molding, injection molding, extrusion molding, blow molding, and so on, are used. With the advance of molding machines and mold structures, resin molded articles having complicated shapes have been able to be molded easily.
However, there is a case that it is still difficult to manufacture a molded article having a complicated shape by molding at a time. In addition, it is often necessary to form parts of a molded article out of different kinds of resins. In such a case, a plurality of molded pieces are molded respectively, and thereafter integrated by welding.
Welding resin molded pieces is performed as follows. That is, joint surfaces of a pair of molded pieces to be welded are heated. The molded pieces are brought into pressure contact in the condition that at least one of the joint surfaces is melted. In that state, both the molded pieces are cooled. As the method of heating the joint surfaces, there are known a method using a heated hot plate; a method in which a pair of molded pieces are subjected to vibration in the condition that they are brought into pressure contact with each other, so that they are heated by frictional heat; and so on. The former is called a hot plate welding method, and the latter is called a vibration welding method. Further, a method for vibrating molded pieces by use of ultrasonic vibration is called an ultrasonic welding.
Of such welding methods, the hot plate welding method is carried out as follows. In this method, joint surfaces of a pair of molded pieces to be welded with each other are brought into contact with the surfaces of a hot plate heated to a temperature not lower than softening points of the molded pieces so that the molded pieces are melted. After the hot plate is removed, the joint surfaces of the pair of molded pieces are brought into pressure contact with each other, and cooled in that condition. Since the hot plate welding method is simple in equipment and easy in welding, it is used broadly especially.
However, when molded pieces formed of resins different in melting point are welded with each other by use of the hot plate welding method, there may arise a failure. For example, to weld two molded pieces having a large difference in melting point from each other, it is necessary to heat the hot plate to a temperature not lower than the melting point of the higher-melting molded piece. If both the molded pieces are brought into contact with such a hot plate, the lower-melting molded piece may be melted in a portion other than the joint portion thereof, or softe
Hirose Yoshikazu
Ito Shinji
Kawahara Tadashi
Kino Hitoshi
Komori Takahiro
Ali Hyder
Posz & Bethards, PLC
Toyoda Gosei Co,., Ltd.
Yuen Henry C.
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