GB2247283A

GB2247283A - Rotary positive displacement pumps

Info

Publication number: GB2247283A
Application number: GB9115108A
Authority: GB
Inventors: Gerd Rosemann
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1990-08-23
Filing date: 1991-07-12
Publication date: 1992-02-26
Anticipated expiration: 2011-07-12
Also published as: IT1248353B; ITRM910462A1; ITRM910462A0; DE4026618A1; GB2247283B; FR2666124A1; GB9115108D0; FR2666124B1

Abstract

To reduce the humming sound produced by a vaned-cell pump or toothed-wheel pump with an internal axle the rotating parts of the pump are so constructed that each pumping cell has its own, individual minimal cell volume and/or maximal cell volume, or its own delivery volume, which is different in every other cell.

Description

1 VANED-CELL PUMP OR TOOTHED-WHEEL PUMP WITH AN INTERNAL AXLE

The invention relates to a vaned-cell pump or a toothed-wheel pump with an internal axle, as described in the preamble of Claim 1.

Pumps of this kind are often used, in conjunction with electric motors, as fuel pumps for feeding fuel to internal combustion engines in motor vehicles.

But it has been found that when a pump of this kind is operating under load it makes a humming sound, which the passengers in the vehicle can find disagreeable. Attempts have therefore been made for many years to find a way to reduce the noise. One known method, described in the German Patent Specification 36 24 532, is concerned only with bubble noise (cavitation). Bubbles formed in each pumping cell when the fuel is under suction collapse noisily when the suction is replaced by pressure. But, as already mentioned just above, this known method is concerned only with bubble noise. No method has hitherto been found for reducing the humming sound made when bubble-free fuel is conveyed, apart from subsequent sounddamping measures.

On careful investigation it was found that each pumping cell produces a suction pulse followed by a pressure pulse once in each revolution of the pump. The pulses are added regularly to each other, producing sound waves which, at high revolutions, make a clearly audible hum.

In the course of further investigations it was found that the humming noise varies in intensity from example to example of the pump.

2 X Measurements made on the individual examples showed that the noisiest pumps were those which had the narrowest tolerance gaps and the least deviation from perfect symmetry. The pumps with the widest tolerance gaps and the least symmetry were the quietest.

From these findings it was inferred that the production of noise is influenced by the number of similar sound-producing events taking place in each unit of time.

From this starting point the intention in the present invention is therefore to make the conventional pump less noisy by modifying it in such a way that only a few similar sound-producing events take place in each unit of time.

Claims

The problem is solved by the characteristics claimed in Claim 1. Further advantageous developments are described in the subsidiary claims. The advantages achieved will now be described with the help of several examples of the invention. The invention starts out from a conventional vaned-cell pump, or toothedwheel pump with an internal axle. A pump of this kind has several enclosed pumping chambers. In each revolution of the pump the volume of each pumping chamber changes from a minimal volume (the pumping chamber containing only a dead space where no fluid is conveyed) to a maximal volume, which is the minimal volume plus the volume conveyed by this pumping chamber. Pumps of this kind are used, for example, for feeding fuel to internal combustion engines.

1 1 i 0 Y 1 1 i i i i 1 1 i i i i 1 i f i 3 1 Starting from a conventional pump of this kind, the rotating parts of the pump, i.e. the vaned-cell rotor, or the inner and outer rotors, are modified in such a way that the minimal and maximal volumes, or the delivery degree, of the individual pumping cells varies from cell to cell, i.e. is different in each individual pumping cell.

To make the minimal cell volume vary from cell to cell, modifications are made to portions of those walls of the rotating parts of the pump which cooperate with walls of the pump housing, or with walls of other rotating parts, without forming seals with them. The purpose is to make these wall portions differ from cell to cell, i.e. to make them different in each individual cell. For example, the wall portions can have cut-away regions formed by drilling blind holes of different diameters to different depths.

Another modification (Claim 5) of the conventional pump is concerned with those walls of the rotating pump parts which form controlling edges of the inlet mouths of the suction and pressure channels. According to the invention these walls are of different constructions for each pumping cell.

What is obtained is that, with each rotation of the pump, each pumping chamber becomes connected with the suction channel, or with the pressure channel, before reaching minimal or maximal cell volume, the earliness of the connection varying from cell to cell. Consequently with each rotation of the pump, each pumping chamber conveys a different quantity of liquid, or achieves a different delivery degree.

4 Furthermore, if desired (Claim 6), those portions of the walls of the rotating parts of the pump which cooperate with other walls so as to make seals with them can be constructed in such a way that each pumping cell has its own, different, tolerance gaps. Consequently, by the effect of leakage, each individual pumping cell delivers a different volume of liquid in each revolution of the pump, or achieves a different delivery degree. For this purpose a vaned-cell pump, for example, can be given an unround rotor, i.e. a rotor with an unround contour, so that in the course of each revolution the narrowest tolerance gap between the rotor and the pump housing varies continually. On the other hand, a toothed- wheel pump can have an irregular tooth contour and/or an irregular tooth- gap contour so that, here again, the narrowest tolerance gap between the rotating inner and outer rotors, or in between their teeth and tooth-gaps, varies continuously in the course of each revolution.

An entirely different solution is described in Subsidiary Claim 8. In this case the electric motor drives the pump through a coupling which is flexible in torsion.

This arrangement can also be applied, additionally, to the pumps of Claims 1 to 7. What is obtained is that the speed of rotation of the pump varies in the course of each revolution, in response to the suction and outlet pressure waves. Consequently the events take place irregularly, i. e. with irregular timing, and do not add up together. This makes the pump operate more quietly.

i 1 1 i i i 1 i 1 I 1 k CLAIMS 1. A vaned-cell pump, or a toothed-wheel pump with an internal axle, with several enclosed pumping cells whose volumes change from a minimal to a maximal volume, and back again, during each revolution of the pump, particularly for feeding fuel to an internal combustion engine; the pump having suction and pressure channels connected axially to the pumping cell, characterised in that the rotating parts of the pump are constructed in such a way that each pumping cells has its own individual minimal or maximal volume, or both, which is different in all the other cells, or its own individual delivery volume, which is different in all the other cells.

2. A pump as claimed in Claim 1, characterised in that certain portions of those walls of the rotating parts of the pump which cooperate with outer walls without forming seals with them differ in construction from cell to cell, in regard to minimal cell volume (dead space).

3. A pump as claimed in Claim 2, characterised in that the walls have cutout regions of different sizes.

4. A pump as claimed in Claim 3, characterised in that the cut-out regions are formed by drillings of different diameters or different depths.

5. A pump as claimed in Claim 1 or in one of the Claims 2 to 4, characterised in that those walls of the rotating pump parts which form controlling edges of the inlet mouths of the suction and pressure channels are of different constructions for each pumping chamber.

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6 6. A pump as claimed in Claim 1 or in one of the Claims 2 to 5, characterised in that those portions of the walls of the rotating parts of the pump which cooperate with other walls so as to form seals with them are constructed in such a way that each pumping cell has its own different, tolerance gaps.

7. A pump as claimed in Claim 6, characterised in that the vaned-cell rotor is unround in contour, or the inner and outer rotors have irregular tooth contours or tooth-gap contours.

8. A pump as described in the preamble of Claim 1, or in one of the Claims 1 to 7, characterised in that the pump is driven by an electric motor through a coupling which is flexible in torsion.

Published 1992 atThe Patent Office. Concept House. Cardiff Road. Newport. Gwent NP9 IRH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Marv Crav. Kent.

A.

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