The present invention pertains to a fuel-supplying aggregate, for example for supplying fuel in a motor vehicle.
Fuel-supplying aggregates of the foregoing type have been known. Such fuel-supplying aggregates have been utilized in motor vehicles for supplying liquid fuel from a fuel container under high pressure to an internal combustion engine. Such a fuel-supplying aggregate is an electrically driven fuel pump which is used for pumping fuel from the fuel tank to the vehicle engine under a relatively high pumping pressure from 2 to 3 kg/cm.sup.2 and with a relatively small pumping speed from 40 to 150 l/h.
Even more particularly, the invention relates to a feedback or side passage pump with enclosed vanes or WESTCO-type pump, which operates according to the peripheral or WESTCO principle. Such a pump is disclosed, for example in German patent publication DE No. 3,209,763Al or U.S. Pat. No. 3,259,072. According to the WESTCO principle the optimization of the pump operation is realized by the outer diameter of the impeller, equal approximately to 20-65 mm and a geometric characteristic of the pump Rm=S/L which lies approximately within the range of 0.4 to 2 mm, wherein S is an enclosed cross-sectional area between the feeding passage wall and the periphery of the impeller and L is the length of the periphery of the portion of the impeller immersed in the feeding passage. The geometric characteristic or index Rm can ensure designing of the shape of the fuel-feeding passage and the impeller so that a very large play can be defined therebetween.
The description of the prior art WESTCO pump operation will be now given with the reference to FIGS. 1 and 2. The impeller 1 shown in FIG. 1, can be, for example very wide with a small radial extension of the vanes while the impeller, shown in FIG. 2, is very narrow with a great depth of immersion into a fuel-feeding passage 2. The fuel-feeding passage 2 and impeller 1 are enclosed with a pump housing 3. Thereby the length of the periphery of the portion of the impeller, immersed in the fuel feeding passage 2 is defined by points 5, 6, 7 and 8 on the impeller. The cross-sectional area 5 is at the one side defined by points 10, 11, 12 and 13 on the fuel-feeding passage 2 and at the other side by points 5, 6, 7 and 8 on the impeller 1.
On the scale M=10:1, the peripheral length L in FIG. 1 is about 8.5 mm and the cross-sectional area 5 is about 10.2 mm.sup.2. Therefore the uniform geometric characteristic value R.sub.m =1.2 mm. The differently configurated fuel feeding passages 2 can be formed: for example, fuel conveying passages designated by reference characters 15, 16 in FIGS. 1 and 2 are defined by dotted lines, or they can be formed in any other manner, but always under assumption that the required geometric ratio or value R.sub.m is within the range of approximately between 0.4 and 2 mm. Such designs of the pumps, however do not provide optimal pump effects. The designing of the pumps with taking into consideration of this so-called first characteristic geometric value R.sub.m is not sufficient to construct optimally operating pumps.