Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1999-06-25
2001-10-30
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C417S540000
Reexamination Certificate
active
06308691
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to fuel supply aggregates. More particularly, it relates to a fuel supply aggregate of an internal combustion engine of a motor vehicle.
In the above mentioned supply aggregates, mainly volumetric pumps, such as substantially toothed gear pumps have been used. These pumps operate with a revolution frequency of several tens hertz and produce a noise spectrum which is dominated by the revolution frequency and several low harmonics. This noise can be dampened by a vibration-dampening suspension of the supply pump without difficulties. Therefore, it can be no longer heard in addition to the running noise of the simultaneously operating the internal combustion engine.
The manufacturing cost for a fuel supply aggregate can be reduced and its reliability can be increased when instead of the volumetric pump, a rotary pump can be used. For example, such a pump can be used which during its pump action on the at least one rotatable impeller provides an acceleration applied to the fluid to be pumped.
Rotary pumps because of their construction have a different noise spectrum than volumetric pumps. A rotary pump for use in a fuel supply aggregate must be compact, and therefore the diameter of the impeller must be small. In order to obtain however the required pumping action, the impeller must rotate with high speed and must carry on its periphery a great number of vanes, frequently 40-80 pieces in order to move the fluid to be pumped. The running noise of these pumps has not only a portion of the rotation frequency of the impeller and several low harmonics, but also additionally a portion of a frequency which corresponds to the product of the rotary speed and the number of the vanes. The last portion forms a high frequency whistle tone with a frequency up to 16 kHz which is found by many people as unacceptable. Since such a frequency portion is not contained in the running noise of an internal combustion engine supplied by the fuel aggregate, it is clearly heard at low intensities.
The disadvantage of the rotary pumps prevented their use in fuel supply aggregates, in particular for motor vehicles. It has been attempted to fight the vessel noise by a different design of the vanes of the impeller and an irregular arrangement of the vanes on the impeller. As a result the spectrum of the vessel noise is wider, the noise is thereby similar to a high frequency noises, and is no longer so penetrating. However, the high frequency noise remains still hearable.
The solution, when compared to a rotary pump with a uniformly shaped impeller, is relatively costly. The reason is that the manufacture of the non uniformly shaped impeller is substantially more expensive and its imbalance requires an increased care.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fuel supply aggregate, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a fuel supply aggregate which has a fuel pump formed as rotatory pump and having at least one impeller with a plurality of vanes for supplying fuel from a tank, wherein a fuel throughflow noise damper is arranged upstream of a fuel inlet connection of the fuel pump.
When the fuel supply aggregate is designed in accordance with the present invention, it has the advantage of a favorable price and a simpler construction of a supply aggregate with a rotary pump with a non loud operational noise of a volumetric pump.
A place-saving arrangement for the noise damper is provided by its location in a pre-chamber before an inlet connection of the rotatory pump. A wall of the pre-chamber can be formed partially by a suction filter, through which the fuel to be supplied enters in the pre-chamber.
In accordance with the present invention, the noise damper can extend between the suction filter and the inlet connection over a whole cross-sectional surface of the pre-chamber.
The noise damper can be arranged also in a housing with an outlet pipe which is mounted by close to an inlet connection of the rotary pump. For example it can extend into it or be screwed in it.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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Frank Kurt
Kaeser Stephanie
Miller Carl S.
Robert & Bosch GmbH
Striker Michael J.
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