Internal-combustion engines – Engine speed regulator – Specific throttle valve structure
Reexamination Certificate
2003-10-07
2004-08-10
Hirsch, Paul J. (Department: 3754)
Internal-combustion engines
Engine speed regulator
Specific throttle valve structure
C123S403000
Reexamination Certificate
active
06772730
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a throttle-valve assembly having a housing, which has a continuous throttle opening through which a gaseous medium can flow in a main flow direction, in which a throttle valve fastened pivotably on a throttle-valve shaft is arranged in the throttle opening, in which the throttle-valve shaft can be pivoted by an actuator arranged in the housing, in which, starting from the axis of rotation of the throttle-valve shaft downstream along the main flow direction of the gaseous medium, the throttle opening has an approximately straight cylinder section with a height H
1
and a radius R
Z
and in which a spherical-cap section adjoins the approximately straight cylinder section.
To control the quantity of fresh gas for a motor vehicle, use is generally made of throttle-valve assemblies. Throttle-valve assemblies comprise a housing having a throttle opening and a throttle element arranged in the throttle opening. The throttle element assumes a certain position in the throttle opening to allow through a certain quantity of fresh gas. For this purpose, the throttle element can be activated mechanically or electronically.
Housings of throttle-valve assemblies are generally produced from plastic or metal. Housings of throttle-valve assemblies which are manufactured from metal, for example, aluminum, may have particularly low tolerances. Low tolerances are necessary for a throttle-valve assembly, in the region of the throttle valve, particularly if the intention is for the quantity of flow medium passing through the throttle opening of the throttle-valve assembly to be able to be influenced even by a particularly small movement of the throttle valve. In the closing region of the throttle valve, these requirements are also referred to as leakage-air requirements. However, metal housings of throttle-valve assemblies have the disadvantage that, after the housing has been produced, for example by die-casting, complicated re-machining of the housing is required. For example, re-machining of housings made of aluminum is necessary in order to ensure the functional requirements provided in and on the housing. Functional requirements are, in particular, the flow passage, the holder for the actuator and gear axis spacings. Precise machining of the bearing seats is also usually necessary, since the correct operating play (bearing clearance) is produced only by the press fit on the needle bearing.
Throttle-valve assembly housings manufactured from plastic have a lower weight than throttle-valve assembly housings which are manufactured essentially from metal, in particular aluminum. Furthermore, plastic, as the material, can also be adapted in an especially simple manner to a wide variety of geometric configurations of the housing. Moreover, in the case of plastic housings produced by injection molding, inserts, for example bearings for mounting the throttle-valve shaft, can be placed into the injection mold provided for the housing and encapsulated with plastic.
The throttle opening of a throttle-valve assembly usually has an approximately cylindrical cross section. The approximately cylindrical cross section of the throttle opening has the effect of causing a continuous increase in the quantity of flow medium flowing through over the working range of the throttle valve when the throttle valve is opened. This may prove disadvantageous if the throttle valve and the throttle opening have a particularly large diameter, for example 90 mm or more. This is because, from a certain opening angle of the throttle valve, the mass of flow medium passing through the throttle opening only changes to a particularly small extent per unit of time, in particular at a particularly large diameter of the throttle valve, when the position of the throttle valve changes, which means that a finely graduated control of the power of the motor vehicle is no longer possible from a certain opening angle of the throttle valve.
SUMMARY OF THE INVENTION
The invention is therefore based on the object of specifying a throttle-valve assembly of the type mentioned above, which reliably ensures a finely graduated control of the medium passing through the throttle opening during operation of the throttle-valve assembly, in particular for throttle valves having a particularly large diameter.
According to the invention, this object is achieved by virtue of the fact that the spherical-cap section has a central point which, starting from the axis of rotation of the throttle-valve shaft downstream along the main flow direction of the gaseous medium, is displaced by a distance H
2
, with the spherical-cap section having a radius R
K
which is approximately determined by the following equation:
R
K
=[R
Z
2
+(
H
1
−H
2
)
2
]
1/2
.
The invention starts from the consideration that a throttle-valve assembly which reliably ensures a finely graduated control of the medium passing through the throttle opening during operation of the throttle-valve assembly, in particular for throttle valves having a particularly large diameter, is to be manufactured with a particularly low outlay on production. The throttle valve is therefore to remain unchanged in its shape and design in order, for cost reasons, to be able to continue installing standard throttle valves in the throttle-valve assembly. Since the housing of a throttle-valve assembly is usually adapted to specific installation requirements, a finely graduated control of the medium passing through the throttle opening during operation of the throttle-valve assembly is to be reliably ensured by means of a special shaping of the throttle opening. In addition to the simple cylinder shape of the throttle opening, a spherical cap can be impressed in a particularly simple manner into the throttle opening of a throttle-valve assembly. The radius of the spherical cap and distance of the central point of the spherical cap from the central point of the throttle-valve shaft are available in this case as parameters for the design of the spherical cap. Extensive considerations and calculations have led to the surprising result that displacement of the central point of the spherical cap relative to the central point of the throttle-valve shaft linked to a requirement for the radius of the spherical cap has the effect of reliably ensuring a sensitive control of the medium passing through the throttle opening even for throttle valves having a particularly large diameter.
Starting from the axis of rotation of the throttle-valve shaft upstream counter to the main flow direction of the gaseous medium, the throttle opening advantageously has an approximately straight cylinder section with a height G
1
and a radius P
Z
, with a spherical cap section adjoining the approximately straight cylinder section, the spherical-cap section having a central point which, starting from the axis of rotation of the throttle-valve shaft upstream along the main flow direction of the gaseous medium, is displaced by a distance G
2
, with the spherical-cap section having a radius P
K
which is approximately determined by the following equation:
P
K
=[P
Z
2
+(
G
1
−G
2
)
2
]
1/2
.
The characteristic curve along the throttle-valve assembly can additionally be flattened by the fact that the throttle opening has a spherical-cap section both downstream and upstream of the axis of rotation of the throttle-valve shaft, the radius of both spherical caps being spaced apart from the central point of the throttle-valve shaft and the radius of the spherical caps satisfying at least one of the equations stated above.
In an advantageous manner, the value of R
Z
is equal to the value of P
Z
and the value of R
K
is equal to the value of P
K
. A throttle opening of a throttle-valve assembly, which opening is constructed symmetrically relative to the closed position of the throttle valve, can be produced with particularly little outlay. In this case, the parameters H
1
, H
2
and R
Z
can be used to adapt the particular throttle-valve assembly t
Farber Martin A.
Hirsch Paul J.
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