Fuel supply aggregate with a rotary pump

A fuel supply aggregate has a fuel pump formed as a rotary pump and having at least one impeller with a plurality of vanes for supplying fuel from a tank, the fuel pump having an inlet connection, and a fuel throughflow noise damper located upstream of the fuel inlet connection of the fuel pump.

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.

DESCRIPTION OF PREFERRED EMBODIMENTS
 A first embodiment of an inventive fuel supply aggregate is shown in a
 longitudinal section in FIG. 1. It is inserted in a fuel tank of vehicle
 through an opening in its wall and is mounted in the opening by a flange
 1. A substantially cylindrical housing of the fuel supply module has a
 cylindrical inner chamber 11 and an outer chamber 12 which surrounds the
 inner chamber in a ring-shaped manner. An electric fuel pump of a rotatory
 type is accommodated in the inner chamber 11. An inlet connection or a
 suction pipe 3 of the fuel pump 2 extends through an opening in a bottom
 of the inner chamber 11.
 The pump 2 in a known matter has an electric motor which drives an impeller
 with a rotary speed of approximately 6000-24000 revolutions per minute.
 The impeller has 40-80 identical vanes which are uniformly distributed
 over its periphery. They have a diameter of approximately 35-50 mm. The
 fuel aspirated and supplied by the fuel pump 2 first passes in the
 connection at the fuel pump 2, a filter 4 in the outer chamber 12, and
 then is supplied to a supply conduit 5 of a not shown internal combustion
 engine.
 A flat-cylindrical pre-chamber 6 is arranged under the bottom of the
 housing 10. The chamber 6 is formed by a ring-shaped side wall 8 which is
 fitted or screwed on a complimentary projection 9 on the bottom of the
 housing 10, and a bottom wall which is formed by a suction filter 7 of a
 thin layer of a rigid, permeable fiber material. In order to better
 withstand the pressure of the fuel which flows in the fuel pump 2 through
 the suction filter 7, the suction filter is slightly curved downwardly.
 A noise damper 13 is arranged in the pre-chamber so that it covers the
 whole cross-section of the inlet connection 3 and therefore prevents
 exiting of a running noise of the pump 2 transmitted by the fuel, to the
 straight path from the inlet connection 3. In the shown example, the noise
 damper 13 extends over the whole horizontal cross-section of the
 pre-chamber 6 and is located close to the side wall 8. Due to this
 arrangement, also reflecting running noise can not be released from the
 suction pipe 3 without being dampened.
 The noise damper 13 has an inner design which will be explained in detail
 later on. The fuel pump 2 is supplied with energy through a plug connector
 14 and through electric conductors 15 extending through the flange 1.
 Fuel which is not used by the internal combustion engine is supplied
 through a return conduit 16 to a jet pump 17. The jet pump is located in
 the vicinity in the bottom of the tank and faces an opening 18 in the wall
 of the bucket 19. The bucket surrounds the pre-chamber 16. The fuel jet
 produced by the jet pump 17 removes fuel from the tank through the opening
 18 in the bucket 19 and supplies it to a fuel level in the bucket 19 which
 is higher when compared with the rest of the tank.
 FIG. 2 shows a second embodiment of the inventive fuel supply aggregate.
 Parts of this embodiment which correspond to the parts of the first
 embodiment are identified with the same reference numeral and not
 described in detail. The noise damper 20 in this embodiment includes a
 fixed housing with an outlet pipe 21 which is tightly inserted in the
 suction pipe 3 of the fuel pipe 2. In this embodiment an efficient damping
 also of reflected running noise is guaranteed without tightly connecting
 the noise damper 20 to the side wall 8. Therefore, inlet openings for the
 fuel can be arranged substantially arbitrarily on the cylindrical housing
 of the noise damper 20, including also Its upper side, depending on the
 preference.
 In a not shown variant of this embodiment, the inlet connection 3 of the
 fuel pump 2 can be provided with an inner thread and the outer pipe 21 of
 the noise damper can be provided with a complimentary outer thread. The
 noise damper 20 and the pre-chamber 6 can have such a cross-section that
 the noise damper can be freely turned about the axis of its outlet pipe
 and screwed into the suction pipe 3.
 FIG. 3 shows a perspective view of a further variant of a noise damper,
 which is used in the inventive fuel supply aggregate. The noise damper 20
 is inclined when seen from below, with the outlet pipe 21 facing away from
 an observer. The inlet opening is arranged at the side of the body of the
 noise damper which faces the observer. It is surrounded by a plurality of
 projections which form a ring. Further projections 24 can be arranged on
 the upper surface of the noise damper. The function of the projections is
 to support inwardly the mounting in the pre-chamber 6 of the suction
 filter 7. Its further objective is to prevent a contact of the suction
 filter 7 with the upper surface of the noise damper and the resulting
 reduction of the effective cross-sectional surface of the suction filter
 7, which can occur in the event of high pressure of the throughflow fuel,
 a short time increase of the fuel consumption, or progressing dirtying of
 the suction filter.
 The noise damper in its interior can be formed differently. It can be
 formed completely as a porous, vibration-damping material, for example an
 open pore foam material. Such a material provides a low flow resistance to
 the fuel and dampens the running noise exiting the inlet connection 3 by
 dissipation of the vibrations. This possibility comes into consideration
 particularly for the fuel supply aggregate shown in FIG. 1.
 Another possibility is shown in FIG. 4. The noise damper shown in this
 figure has a flat reflector which is arranged in a housing and formed as
 an air-filled chamber 20. Over its whole outer periphery, it is embedded
 in a porous, vibration-dampening material 26. The material 26 extends
 ring-shaped around the whole periphery of the chamber 20. The fuel which
 enters through the lower inlet opening 22 is laterally deviated on the
 reflector 25, passes through the porous material 26, and exits through the
 outlet pipe 21 in the fuel pump. The running noise coming from the fuel
 pump through the outlet pipe 21 is to a great degree reflected by the
 reflector 25 back into the pump. Further dampening is performed in the
 material 26.
 It will be understood that each of the elements described above, or two or
 more together, may also find a useful application in other types of
 constructions differing from the types described above.
 While the invention has been illustrated and described as embodied in fuel
 supply aggregate with a rotatory pump, it is not intended to be limited to
 the details shown, since various modifications and structural changes may
 be made without departing in any way from the spirit of the present
 invention.
 Without further analysis, the foregoing will so fully reveal the gist of
 the present invention that others can, by applying current knowledge,
 readily adapt it for various applications without omitting features that,
 from the standpoint of prior art, fairly constitute essential
 characteristics of the generic or specific aspects of this invention.