GB2240590A - Petrol pump for fuel injection systems - Google Patents

Abstract

The pump is modular in structure and comprises a self-contained motor 1, a cover 2 that can be coupled to the motor and has a fuel outlet pipe 12 and a pumping device comprising a stator 5 and a cover 6, the motor 1, the cover 2 and the pumping device lying within a cylindrical casing 3 having flanged mouths 4 and 18. The stator 5 and cover 6 define a cylindrical cavity 10 within which an offset rotor 7 having radial blades 9 is rotatable about a shaft 14 which engages in cavity 15 of the rotor. A hole (16), Fig 3, which may have a polygonal section or a tapered cylindrical section is provided in the rotor 7 for engagement by motor shaft 17. The pumping device consists of parts of plastic or thermoset material except for the shaft 14 which is of metal. <IMAGE>

Description

PETROL PUMP FOR EXPLOSION MOTOR INJECTION SYSTEMS The instant invention

relates to a new petrol pump, especially designed for medium pressure single-point injection systems, though the invention can also be used.

with slight changes, in high pressure pumps for multi-point injection, and can at all events be used both submerged and on line.

Within the field of petrol pump structures for singlepoint injection systems, the pumping elements employed used to consist of a turbine coupled to an electric motor, both elements revolving at high speeds, some 6,000 to 7,000 r.p.m.

These pumping elements are made of plastic or thermoset materials, and therefore upon assembly the turbine is connected to the electric motor's shaft, with the rotor having to be balanced and its windings streamlined with plastic material, because of the high revolving speed under the usual working conditions, in order to reduce vibration and the torque effect stemming from hydrodynamic resistance, originating in the said high speed revolution within the fuel in which all such elements will be immersed. Because of such pumps' physical operating principle, they can only work if and when submerged in the vehicles' fuel tank.

Another type of pump. used for this same purpose, likewise comprises an electric motor, coupled to a pumping element, which is in this case of a volumetric nature, generally made of metallic materials and with very tight f its 1 between the parts, to which the f uel line pipe connecting elements, usually made of plastic, must be added. The most frequent problems in these pumps lie in the f act that the dirt in the petrol can block the pump when its particles have a size of one-hundredth of a millimetre, which can hardly be trapped by a f ilter, with normal maintenance, without special care and without same being clogged after a short while. This type of pumps can be f itted both on line and in the fuel tank.

The essential problem deriving f rom either type of conventional pump lies in the fact that they share an integrated structure such that the rotor-motor supports and their brushes are located at the f uel inlet and outlet elements.

To summarize the structural characteristics of the pumps used in singlepoint injection systems, operating at a pressure of roughly one bar, the following can be stated:

Turbine pumps need an electric motor with a high output torque and a high revolutions rate, this entailing manifold and varied problems. on the one hand, such problems affect the economic side, since a rotor-motor must be perfectly balanced in order to avoid vibrations and streamlined in order to lower the resisting torque due to hydrodynamic resistance within the petrol. Another problem is mechanical, negatively affecting the pumpts life. since the collector wears more the higher the speed of revolution.

For their part, displacement pumps, with their pumping element made of metallic materials and with very narrow play between their mobile parts. in addition to requiring plastic parts as petrol inlet element. have their greatest disadvantages in the fact that, since there is very little 1 i i play between the mobile parts, these pumps are highly sensitive to problems generated by dirt particles, at the same time as they cause abrasion that heats the petrol and can lead to the well-known cavitation effect. Furthermore, because of its high inertia, when they start to move, they operate for quite some time in the micromotor's starting torque area, with high current intensities in the collector thereof, with the resulting damage and shortening of their useful life. Besides this, they comprise a great many precision parts, that as aforesaid are made of metal and must be sintered, this entailing a high manufacturing cost.

The petrol pump subject of the invention fully solves these problems in explosion motor injection systems, and to such end focusses its characteristics on two essential aspects, on the one hand modularity thereof, i.e., constructing same with physically independent parts that can be easily coupled to each other, as opposed to the integrated nature of any of this sort of conventional pumps, and on the other, the low revolutions rate, which results in a longer life, less noise, the use of a small motor, which may on the other hand comprise a market element because of the aforesaid modularity, and finally the fact that it is unnecessary for such motor to be balanced or streamlined, likewise because of the low revolutions rate at which the pump works.

More specifically, and in order to achieve the above, the petrol pump subject hereof consists of a conventional low revolutions rate micromotor, some 3,000 to 3,500 revs., whose shaft lies within a stator, comprising a cylindrical body and a cover, which stator is slightly off-centre as regards the motor shaft, which is locked together with a rotor lying within the stator body and provided with a series of radial seats for respective blades, preferably made of teflon, so that between the stator body and cover, the rotor and the latter's blades there are a series of chambers of varying volume, and when their volume increases they face a fuel inlet port, disposed in the stator body, whereas when the volume thereof decreases, they in turn face another port, this time for the fuel to leave and which is disposed in the stator cover.

According to another characteristic of the invention, the stator is provided with a shaft which is largely inserted in the rotor to become the main pump shaft, bearing with the strain generated during normal operation thereof, transmitting same from the rotor to the stator without such strain affecting the motor shaft, which acts on the rotor at the remaining sector thereof, i.e., where the shaft associated to the stator body leaves the shaft associated to the stator body free.

For its part, and in order to ensure appropriate positioning of the motor as regards the stator, such motor is provided with a protuberance that surrounds the driving shaft thereof, which protuberance can be fitted into a hole in the stator cover, through which the said motor shaft penetrates into the same.

All the parts making up the pump are made of plastic or thermoset materials, save for the metallic shaft, and such parts are duly enveloped within a cylindrical casing, flanged at one of its ends to prevent such parts from penetrating any further, and which is also flanged at its other end after the packet is made up, which packet also has an outlet pipecover, coaxially and externally coupled to the motor and wherein are inserted or integrated this lattev's lead-in terminals, preferably of the f ast-on type,, with their sockets 1 1 1 pointing to the inside in order to be directly connected to the motor by merely adapting the said cover.

In order to provide a fuller description and contribute to the complete understanding of the characteristics of this invention, a set of drawings is attached to the specification which, while purely illustrative and not fully comprehensive, shows the following:

Figure 1.- Is a perspective view of the constituent parts of a petrol pump for explosion motor injection systems, according to the object hereof.

Figure 2.- Is a side elevation and cross-section of the above view as a whole, duly assembled.

Figure 3.- Is, finally, a likewise side elevation and cross-sectional close-up on the constituent parts of the stator-rotor pump sector.

The petrol pump subject hereof, supplying at a pressure of roughly one kg/cm2, for explosion motor single point injection systems, has a modular structure where the electric motor (1) is a self-contained market part assembled on one side to the pump outlet cover (2), and on the other to the pumping device, these three basic elements thus being coaxially coupled and housed with no clearance within a tubular container or cylindrical casing (3) provided at one end with an internal perimetric rim or f lange (4) preventing 35 further penetration of the llpacke V1 consisting of the above elements as a whole.

This modular structure allows the motor (1) to be structured, as aforesaid, as a self-contained single part, easily assembled in the unit and which can be acquired from specialised manufacturers at satisfactory price and quality levels.

For its part, the pumping device comprises a stator, namely a body (5) and a cover (6), within which there is a rotor (7), cylindrical in nature, revolving urged by the continuous current micromotor (1) and having radial slots (8) freely and slidingly housing respective rectangular blades (9), preferably made of teflon, which the centrifugal force keeps permanently in touch with the internal wall of the cylindrical cavity (10) defined within the stator, which cavity is offset as regards the rotor (7), and therefore the volume between the rotor, each pair of blades thereof and the stator's internal cavity (10) surface gradually increases every half-turn of the rotor and decreases every other halfturn.

In the half-turn in which these changing volumes increase, the respective chambers defined by the blades (9) afford passage to an inlet port (11) provided in the stator body and through which such chambers are flooded with fuel due to their suction effect, while in the other half-turn in which such changing volumes decrease, a thrust effect is generated and the fuel is ejected towards the pipe (12) in the outlet cover (2) through. an outlet port (13) conveniently located at the stator cover (6).

This obviously means that during normal pump operation. the rotor is under different suction and thrust -pressures of roughly one kg/cm2, which generates a force that 1 i 1 constantly urges same in the thrust-suction direction. This f orce, acting upon the rotor, is taken up by a shaft (14) appropriately disposed at the base of stator body (5), as specifically shown in figure 3, about which shaft revolves rotor (7) which is provided to such end with a housing (15) for the said shaft (14), which housing takes up a large part, though not all, of the rotor thickness, with a free space therein where a hole (16) is found for the motor (1) shaft (17) to be coupled, which hole can have a polygonal section or a cylindrical section with a taper, for the shaft (17) to be suitably angularly imbedded in the rotor (7), with such shaft (17) merely driving the rotor, and the motor (1) bearings having at no event to withstand the strain generated at the rotor, which is transmitted to the stator through the shaft (14) implanted in the latter.

After implanting all these elements within the cylindrical casing (3) they are perfectly set by means of the flange existing at the opposite end (18) of the said casing (3).

It should also be noted that, in order for the motor (1) to be suitably positioned as regards the stator, such motor has a protuberance (19) at the front bearing of its shaft (17), which protuberance has the same diameter as a hole (20) existing in the stator cover into which it f its tightly.

In light of the above structure, the pump obtained is of the displacement type, with a small diameter and high capacity and pressure characteristics, despite operating at an unusually low revolution rate, which is especially important to lower the abrasion of the motor and the pump elements, lengthening their usef ul lif e, since, as af oresaid, the motor shaft does not have to bear with the rotor strain whilst back-balanced, same being transmitted straight to the stator through the shaft (14).

The size of the pump shaf t diameter is designed to establish a layer of petrol of a certain minimum width between same and its rotor housing, for a hydrodynamic lubrication effect, though play between the two exceeds 0.1 mm, thereby eliminating this element's abrasion problems and allowing some misalignment between the motor shaft and the pump shaft.

Furthermore, a rim (21) in the stator body allows the cover (6) to be placed thereon to hold the rotor inside same.

The pumping elements' parts are made of plastic or thermoset materials, save for the metallic shaft (14).

These materials will obviously resist any type of automobile fuel at the usual working temperatures, i.e., their dimensions will not be considerably worn or modified, and mechanical characteristics will not be lost, among them significantly a high abrasion strength, part of which comes from the high sphere or fibre glass content. Furthermore, the blades must afford a maximum abrasion strength, and fluorinated plastic, very strong to chemical attack, is therefore used.

In addition, and because of the little weight of these materials and their good frictional characteristics, these parts can have a clearance exceeding 0.1 mn both diametrically and axially, without any vibration, noise or heating of the pumping parts resulting, which might lower the pump's efficiency. There is no sensitivity to dirt particles present in petrol, which amount to no more than some hundredths of a millimetre in size.

1 -C i 1 Another principal advantage of the above structure lies in the fact that due to the combined effect of the bladest clearance and stretching property, the maximum operating pressure is automatically limited, and the conventional pressure -limiting valve present in metallic displacement pumps is no longer necessary.

The large margins for the pumping group's constituent parts, previously referred to, allows the relevant parts to be obtained directly by injection molding, at a low cost.

But, furthermore, and this is of the essence, the pumping system using free blades driven by a centrifugal force with parts made of plastic, is a device that affords is high efficiency at low revolutions, and a small motor can therefore be used, as aforesaid, which in addition need not have a balanced and streamlined rotor, which is clearly advantageous so far as cost reduction is concerned, not to mention the advantages that result from having a longer useful life and a lower noise level.

Because of its volumetric features, the pump can also be used on line, merely adding a part including a petrol inlet pipe, coupled to the stator body and which is similar to the outlet pipe (12) projecting from the cover (2) where. as also mentioned above, the micromotor (1) lead-in terminals (22) are inserted.

A f inal note should be made in the sense that the aforesaid structure is also useful to obtain high pressure pumps for multi-point injection, of some three bars, with slight changes such as reducing the play between mobile pump parts, optimising the characteristics of its non-metallic materials, reducing the stretching properties in the blades and increasing the revolution rate in order to keep up 1 - 10 volumetric efficiency.

We feel that the device has now been described at sufficient length for any expert in the art to have grasped the full scope of the invention and the advantages it offers.

Y The materials, shape, size and layout of the elements may be altered provided that this entails no modification of the essential features of the invention.

The terms used to describe the invention herein should be taken to have a broad rather than a restrictive meaning.

is 1 9 CLAM 1.- Petrol pump for explosion motor injection systems, essentially characterised in its modular structure. with a motor consisting of a self-contained market part assembled on one side to a cover provided with an outlet for the fuel and on the other to a pumping device, such elements being coaxially interconnected and housed with no clearance in a tubular cylindrical casing having flanged mouths.

2.- Petrol pump for explosion motor injection systems, according to claim 1, characterised in that the pumping device comprises a stator, namely a body and a cover, which define a cylindrical receptacle where there is a likewise cylindrical offset rotor, especially characterised in that the said rotor is axially provided with a seat for coupling of a shaft duly locked together at the bottom of the stator body, and also provided, as a continuation of the said seat. with a facetted cylindrical or polygonal hole for coupling of the motorts input shaft driving such rotor, so that the shaft locked together with the stator actually takes up the radial strain generated by the rotor, which is in turn provided with a plurality of radial slots to house respective blades which the centrifugal force displaces against the stator bodyts internal perimetric surface.

3.- Petrol pump for explosion motor injection systems, according to preceding claims, characterised in that the parts integrating the pumping device are made of plastic or thermoset material, save for the metallic shaft associated to the stator body. it being envisaged that the micromotor will have a low revolutions rate, some 3,000 to 3.500, and the mobile parts a relatively large ciearance. therefore hardly being sensitive to dirt in the petrol.

4 0 4.- Petrol pump for explosion motor injection systems, according to preceding claims, characterised in that the low revolutions rate motor also has a low output and does not require a balanced and streamlined rotor.

5.- Petrol pump for explosion motor injection systems, according to preceding claims, characterised in operating without distinction both submerged and on line, in which case the stator body, which contains the fuel intake, has a tubular extension for coupling to the intake, similar to the pipe existing in the cover closing the packet at the micromotor end and through which the fuel exits, from the annular chamber defined between the motor and the cylindrical casing, from the pressure group and through an outlet port provided in the stator cover.

6.- Petrol pump for explosion motor injection systems, according to preceding claims, characterised in that the rotor blades are elastic and this, together with the clearance of the mobile elements thereof, therefore limits such pumpts maximum working pressure.

7.- Petrol pump for explosion motor injection systems, according to preceding claims, characterised in that by further adjusting the mobile elements thereof and with its motor working at a higher rate, it becomes a high pressure pump for multi-point injection systems.

8.- Petrol pump for explosion motor injection systems, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

Published 1991 at The Patent Office. State House. 66/71 HighHolbom. LDndonWCIR4TP. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys, Newport. NPI 7HZ. Prinfed by Multiplex techniques ltd, St Mary Cr2y. Kent.

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