Internal-combustion engines – Engine speed regulator – Specific throttle valve structure
Reexamination Certificate
2000-06-21
2002-08-06
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Specific throttle valve structure
C251S305000
Reexamination Certificate
active
06427661
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a duct system with a throttle valve, especially an air intake duct of an internal combustion engine in which a throttle valve is arranged pivotably in a cross section of the duct. Furthermore, the invention relates to a throttle valve for installation in such a duct system. The invention also relates to a process for controlling a throttle valve in an air intake duct of an internal combustion engine.
It is generally known use throttle valves to close and to open the cross-section of an air intake duct for combustion air for an internal combustion engine. Furthermore, these throttle valves can also be utilized in a partially opened state. This use offers the advantage of reducing the air intake noise in operating ranges of the motor in which the complete cross-section of the air intake duct is not needed to provide combustion air. This occurs through partial closure of the throttle valve. In this way, the cross-sectional area of the flow channel on the raw air side is maintained as small as possible while matched to the operating condition. At the full power operating point, the supply of air to the motor is assured by complete opening of the cross-section of the duct. The remaining cross-sectional area between the wall of the duct and the throttle valve can be adjusted, for example, proportionally to the required mass flow. This achieves in a first approximation the same average rate of flow in the vicinity of the throttle valve.
The continuous adjustment of the throttle valve, however, raises problems. When small cross-sectional areas are required, narrow gaps result between the wall of the duct and the throttle valve which can lead to unfavorable flow conditions. Particularly, if the throttle valve and the cross-section of the duct have a round configuration, a whistling noise, which is more unpleasant than the intake
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air noise that is to be avoided, can arise through the resulting sickle-shaped gap.
One possibility for solving this problem is proposed in European patent EP 889 228. According to this proposal the intake duct of the internal combustion engine has two partial cross sections which are separated from each other by an intermediate wall. The throttle valve is disposed in only one of the partial cross-sections, so that at low rotational speeds (rpm) of the motor, the one partial cross-sectional area of the intake duct can be closed. In this way a reduction of the air intake noise can be achieved.
The multi-chamber profile of the described air intake arrangement, however, causes additional expense. A higher expenditure for materials results, which also leads to an increase in the overall weight of the air intake system and makes the manufacturing process more difficult. For these reasons the proposed solution is less economical, and therefore its use is precluded at the least in modestly priced variants of motor vehicle lines.
SUMMARY OF THE INVENTION
It is the object of the invention therefore, to provide a device for decreasing the cross-section of a duct system which is reliable in operation and inexpensive to manufacture and which exhibits favorable acoustic characteristics.
These and other objects of the invention are achieved by the throttle apparatus and by the process for controlling a throttle valve which are described and claimed hereinafter.
The duct system of the invention includes a throttle valve which is pivotably arranged in a cross section of the duct system. The duct system conducts a fluid which is to be throttled. In accordance with the invention, however, the throttle valve is dimensioned such that in the closed position it leaves a residual cross-sectional area open. The term “closed position” refers to that position of the throttle valve in which it covers or closes off the maximum surface of the cross-sectional area which is to be throttled. If the throttle valve has a flat construction, then the closed position is achieved when the surface of the throttle valve is positioned perpendicular to the direction of flow of the fluid stream through the duct.
In contrast to conventional throttle valves, however, in this closed position the residual cross-section remains open and available for passage of fluid. If the throttle valve is utilized in the intake region of the air intake duct of an internal combustion engine, then a complete closure of the air intake cross section is not desired. Therefore, the throttle valve can be dimensioned such that in the closed position it does not completely cover the cross-section of the air intake duct. The perpendicular orientation of the valve is of great advantage from an acoustic point of view. In this way it is possible to for the throttle valve to reflect the sound waves which pass from the internal combustion engine through the air intake duct to the mouth of the air intake. This leads to a reduction in the air intake noise, since the sound waves cannot leave the system through the air intake opening. The reflected sound waves are superimposed over incoming ones, which may lead to a partial or complete cancellation or suppression.
In this way the air intake noise of the internal combustion engine can be decreased, primarily in the lower and medium rotational speed ranges. At the same time, whistling noises, like those which arise with conventional throttle valves when they are closed up to a tiny remaining gap, are prevented. In order to prevent the whistling noises, the residual cross section is advantageously designed to have an annular configuration around the throttle valve. It is not necessary thereby for the throttle valve to have a round configuration. An oval or a rectangular configuration is just as possible, wherein the cross-section of the duct system must match the form of the valve flap.
The throttle valve can be driven by various types of actuators. Candidates include, for example, electrical step motors or continuously adjustable vacuum boxes. A stepped adjustment of the throttle valve is also possible. Even an embodiment with only two steps, i.e. a closed throttle valve and an open throttle valve, which can be economically controlled with a vacuum box, will result in the acoustic advantages described above. However, then the acoustics of the intake duct cannot be continuously adapted to the operating conditions of the internal combustion engine. Instead, operating ranges must be defined in which the different step positions of the throttle valve are used.
In accordance with one particularly advantageous embodiment of the invention, the throttle valve is arranged in the narrowest cross-section of a duct section having a venturi-form cross-sectional configuration. The venturi-form configuration of the duct likewise has an advantageous effect on the acoustics of the intake duct.
It is not necessary for the throttle valve to be round. Instead it can take different forms, for example rectangular. The cross-section of the associated duct section must be appropriately matched to the form of the valve flap. Accordingly, the residual cross-sectional area surrounding the throttle valve and bounded by the walls of the duct system also does not have to be round. Instead, the annular residual cross-section is matched to the contours of the valve flap and the duct. The important thing in the configuration of the residual cross-sectional area is merely that regardless of the position of the valve flap, no regions are produced in which the spacing between the edge of the valve flap and the wall of the duct system is so small that whistling noises can arise.
The acoustic effects described above can be utilized especially efficiently if the residual cross-section amounts to a surface portion equal to from 10 to 40 percent of the overall surface area of the cross-section in which the throttle valve is positioned. In this way, on the one hand, a sufficiently large cross-section is available for operating conditions of the motor which require a maximum amount of air, and on the other hand, the cross-sectional area can be effectively decreased by the thr
Castro Arnold
Crowell & Moring LLP
Filterwerk Mann & Hummel GmbH
Wolfe Willis R.
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