Internal-combustion engines – Intake manifold – Manifold tuning – balancing or pressure regulating means
Reexamination Certificate
1999-04-16
2001-04-03
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Intake manifold
Manifold tuning, balancing or pressure regulating means
Reexamination Certificate
active
06209503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an intake duct as a passageway adapted to supply air to an engine, and more particularly to an intake duct capable of reducing noise during use.
2. Description of the Related Art
Intake systems used with motor vehicle engines generate noise in conjunction with the intake of air. This intake noise is offensive to persons in the motor vehicle, particularly when the engine is running at low speeds. Conventionally, side branches and/or resonators have been provided in such intake ducts to reduce the noise at a specific frequency, calculated, for instance, in accordance with the Helmholtz's resonance theory.
However, the side branches may be as long as about 30 cm, and the resonators may have a volume as great as 14 litters. To install these devices in the engine compartment, increased space is needed which necessarily decreases the amount of room available for installing other parts.
Japanese Utility Model application laid-open No. Sho 64-22866 discloses an arrangement where orifices are provided in an intake duct, and intake air is throttled at the positions of the orifices; thereby reducing intake noise. By throttling the intake passage in this manner, the acoustic mass increases, and consequently, the intake noise of the engine at low frequencies can be reduced.
Japanese Utility Model application laid-open No. Hei 3-43576 discloses a device for reducing intake noise that includes two intake pipes, and a valve which selectively opens and closes the upstream side of one of the intake pipes in accordance with the an operating mode of the engine.
An intake duct shown in
FIG. 49
for example, corresponds to the intake duct disclosed in Japanese Utility Model application laid-open No. Hei 3-43576, and includes a first intake pipe 1000 of a small diameter and a second intake pipe 2000 of a larger diameter. In the second intake pipe 2000, a valve 3000 is pivotably provided. A pivot shaft of the valve 3000 is connected to a center of a disk-like cam 4000, and a spring 5000, one end being fixed to a vehicle body, is secured to a periphery of the cam 4000. The spring 5000 is arranged such that the biasing force thereof is reduced to a minimum when valve 3000 fully closes the second intake pipe 2000.
With the intake duct thus arranged and the intake pressure of the second intake pipe 2000 less than a predetermined value, valve 3000 fully closes the second intake pipe 2000 so that air is drawn through only the first intake pipe 1000; this reduces intake noise across low frequencies. When the intake pressure exceeds the predetermined value, valve 3000 pivots against the biasing force of spring 5000, which is transmitted through cam 4000, to increase the opening area of the second intake pipe 2000 in proportion to the intake pressure, thus enabling a sufficient amount of air to be supplied.
The above-described method of throttling the intake passage, however, produces a problem when the engine runs at a high--speed since the amount of intake air is insufficient and lowers the engine output.
With the device disclosed in Japanese Utility Model application laid-open No. Hei 3-43576, there is a state where valve 3000 is held between a fully closed position and its fully-open position to prolong the time period the second intake pipe 2000 is half closed. In this case, the problem is that since the acoustic mass is small, the intake noise is large even though the engine is running at a low speed, resulting in booming noise of low frequencies entering the passenger compartment of the motor vehicle.
Furthermore, Japanese Utility Model application laid-open No. Hei 3-43576 discloses the use of an electronic control circuit, an electromagnetic valve, and a diaphragm actuator, or the like, for operating a valve member. The use of these parts increases in the total number of parts used, and also increases the complexity of the device, both of which are less favorable in terms of production costs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an intake duct capable of: 1) reducing intake noise when an engine runs at low speeds; 2) introducing a sufficient amount of air when the engine runs at a high speed; 3) preventing the generation of low frequency booming noise; and 4) being produced at low costs without using any electronic control circuit, electromagnetic valve or the like.
In a first aspect of the present invention, the intake duct, as a passageway adapted to supply air to an engine, includes a first intake passage, a second intake passage, a valve member pivotably provided in the second intake passage for opening and closing the second intake passage, and a biasing device for biasing the valve member towards a closed position in the second intake passage. The valve member has been designed to have limited movement when it opens the second intake passage and yet exhibit easy movement when it closes the second intake passage.
As noted above, the intake duct made in accordance with the present invention has first and second intake passages, and a valve member which opens and closes the second intake passage. When the engine runs at a low speed, intake pressure in the second intake passage is equal to or less than a predetermined value. So, by determining the biasing force of the biasing device to be greater than such a predetermined value, when the engine runs at a low speed the valve member closes the second intake passage and only the first intake passage remains open. Accordingly, when the engine runs at a low speed, the resultant intake passage is in a throttled state thus increasing the acoustic mass, and thereby reducing low frequency intake noise.
When the engine runs at a high speed, the intake pressure in the second intake passage exceeds the biasing force so that the valve member opens the second intake passage. This resultant intake passage is enlarged, and consequently, a sufficient amount of air can be supplied to the engine running at a high speed. Intake noise is generated at this time, but in comparison to the engine noise it is so small so as to not be perceived.
The intake duct of the present invention further includes valve adjusting mechanism adapted to limit the movement of the valve member when the valve member opens the second intake passage and to facilitate movement of the valve member when the valve member closes the second intake passage.
The movement of the valve member is limited or facilitated by the valve adjusting mechanism. When the intake pressure is at a predetermined value or less and the valve member closes the second intake passage, the valve member is held in its fully closed position by the biasing force exerted by the biasing device and as limited by the valve adjusting mechanism. When the engine runs at a high speed, the intake pressure is greater than the predetermined value and when it overcomes the biasing force the valve member will be held in its opening state within the second intake passage. At this time, the limiting force of the valve adjusting mechanism for limiting the movement of the valve member is small so that when the intake pressure decreases the valve member readily moves with the biasing force in such a direction so as to close the second intake passage. Once the valve member closes the second intake passage, the limiting force is exerted by the valve adjusting mechanism. This results in a time period in which the valve member opens half of the second intake passage to decrease, thus preventing booming noises from being perceived.
To improve these operational advantages further, it is preferable to decrease the opening area of the first intake passage and to increase the opening area of the second intake passage. Where the intake duct has a branch arrangement wherein two intake passages, including first and second intake passage, respectively, are joined to define a single intake passage, it is preferable to make the first intake passage thinner to increase the acoustic mass further while making the second intake pass
Fujihara Kazuo
Hirose Yoshikazu
Ishihara Hidetoshi
Kino Hitoshi
Komada Minoru
McMahon Marguerite
Pillsbury Madison & Sutro LLP
Toyoda Gosei Co,., Ltd.
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