EP1092093B1 - Membrane pump and membrane therefor - Google Patents

Description

The invention relates to a device for transmitting a volume of fluid under pressure, in particular intended for a pump petrol for a direct injection engine. She is also relating to a pump equipped with such a device.

More specifically, the invention relates, according to its first aspect, a device for transmitting a volume of fluid under pressure, comprising at least one enclosure and one deformable membrane of generally rounded shape, this membrane comprising a central part movable between two extreme positions, a peripheral part by which it is fixed in said enclosure to define a first and a second fluid chamber and, between its part peripheral and its central part, an intermediate part whose cross-section in a transverse plane has a shape substantially U-shaped.

Such a device is for example described in the documents FR 2,422,086 and US 4,153,391.

A device for transmitting a volume of fluid under pressure, for example intended for a fuel pump, comprises conventionally an enclosure and a fixed deformable membrane in said enclosure to define two fluid chambers.

While the aforementioned US patent document 4,153,391 relates an application in which the central part of the membrane is directly driven by mechanical means, the present invention aims to allow application in which the membrane is displaced by the fluid of one of the two rooms which it delimits.

In such an application, a mechanism such as a pump pistons prints back and forth to a piston which moves into the first chamber, containing for example oil.

This movement causes a constant volume displacement of the oil in the first chamber. This displacement that of the membrane itself in the second room, this one containing for example gasoline.

The movement of the membrane has the effect of repressing gasoline, especially to a collector. A system gas supply to the second bedroom is planned to fill this room again.

In such an application, the membrane therefore has both function of ensuring sealing between the liquids contained in each of the rooms and allow the movement of the second liquid due to displacement of the first liquid.

Conventionally, the membrane of such a device is substantially flat and it is fixed in the enclosure by means from its peripheral edge.

During the operation of the device, such a membrane can deform on either side of its rest position.

It is therefore in high demand in terms of its peripheral edge, which leads to fatigue risks.

The object of the invention is to overcome these drawbacks by proposing a membrane device for the transmission of a volume of fluid under pressure, in which the membrane does not not likely to deteriorate under the effect of constraints to which it is subjected during use, and this thanks to a particular geometry and characteristics allowing this membrane to work optimally.

To this end, the device of the invention, moreover conforms to the generic definition given in the preamble above, is essentially characterized in that the mounting of the membrane in the enclosure is such that, what whatever the position of the central part of the membrane, the curved bottom of the U-shaped intermediate part is not contact with the walls of the enclosure or with any other part of the device, so that said part intermediate is able to wind and / or unwind freely during movement of the membrane, during operation of the device, without the peripheral part of the membrane undergoes traction.

Contrary to what is provided for in the patent document FR 2 422 086 cited above, the curved bottom of the part U-shaped intermediate of the membrane, which is the most stressed, is protected from any friction wear.

Throughout the description, we understand by "plan transverse "a plane perpendicular to that in which extends the membrane itself and passing through an axis of symmetry of the membrane.

Preferably, the membrane is mounted in the device so that at mid-course, it presents its shape in the state free.

Also preferably, the connecting parts of the branches of the U-shaped intermediate part with the part central and the peripheral part of the membrane rest on parts of the device whose shape they match. These connection parts can rest freely on said parts or be adhered to them, for example by overmolding.

The thickness of the intermediate part of the membrane is lower than that of the central part and the part membrane device.

Advantageously, the device comprises a pusher resiliently mounted in the second fluid chamber and which is attached to the central part of the membrane.

Preferably, this pusher comprises a part for guiding the displacement of the membrane.

Preferably, the membrane has means to avoid its deterioration against sharp edges of said enclosure, consisting in particular, in its central part, of a shape hollow or in a rigid valve fixed to the membrane.

Preferably, the device comprises means for evacuate the fluid from the first chamber, which may be trapped between said enclosure and the intermediate part in U of the membrane, these means being notably constituted by drainage channels made in the device itself or even in said valve.

The peripheral part of the membrane has advantageously a seal.

In an exemplary embodiment, the transmission device a volume of pressurized fluid according to the invention comprises several membranes which are formed in a single block.

The invention also relates to a pump, such as a pump. gasoline engine for direct injection, equipped with a device for transmitting a volume of fluid under pressure according to the invention.

La figure 1 est une vue en coupe transversale, schématique et partielle, d'un dispositif de transmission d'un volume de fluide sous pression selon l'invention, avec une membrane en position haute.

La figure 2 est une vue similaire à la figure 1, dans laquelle la membrane est en position basse.

La figure 3 est une vue similaire à la figure 1, illustrant une variante de réalisation de la membrane selon l'invention.

La figure 4 est une vue générale en perspective d'un bloc de trois membranes selon l'invention.

The invention will be better understood and other objects, advantages and characteristics thereof will appear more clearly on reading the description which follows and which is given with reference to the appended drawings, in which:

Figure 1 is a schematic and partial cross-sectional view of a device for transmitting a volume of pressurized fluid according to the invention, with a membrane in the high position.

Figure 2 is a view similar to Figure 1, in which the membrane is in the down position.

Figure 3 is a view similar to Figure 1, illustrating an alternative embodiment of the membrane according to the invention.

Figure 4 is a general perspective view of a block of three membranes according to the invention.

The elements common to the different figures will be designated by the same references.

Referring first to Figure 1, the device transmission of a volume of fluid under pressure according to the invention forms an enclosure in which is fixed a membrane 1.

This membrane thus makes it possible to define a first chamber of fluid 2, located here above the membrane 1 and a second fluid chamber 3, located here under the membrane 1.

In the first chamber 2 can move a piston 4.

In the example illustrated in FIG. 1, the piston 4 is in high position.

Between the piston 4 and the membrane 1 is a volume fluid constant which can in particular be oil.

In the second chamber 3 is provided a pusher 5 which is resiliently mounted so as to push the membrane 1 against the spacer 6. The chamber 3 is filled with a fluid, especially gasoline.

This elastic mounting is carried out by means of a spring 7 which is mounted between the wall of the chamber 3 and the bottom 50 of the button.

Furthermore, in the example illustrated in FIG. 1, the pusher 5 is extended by a cylindrical guide part 51 which is designed to slide in a corresponding bore 3a of the bedroom 3.

In the example illustrated in Figure 1, the membrane 1 has a generally circular shape. This also appears on the Figure 4 which shows three membranes 41, 42, 43 similar to the membrane 1, formed in a single block.

The membrane 1 could have another general shape rounded, for example an oval shape. However, it is a circular shape which seems the most advantageous.

Thus, Figure 1 shows the membrane 1 in section along a diameter.

It appears that the membrane has a central part 10, under which the pusher 5 is fixed, a peripheral part 11 by which the membrane is fixed in the device, and an annular intermediate portion 12 which has, in diametral section, a substantially U-shaped. This part U-shaped is not in contact with any part of the device.

As illustrated in FIG. 1, the peripheral part 11 of the membrane 1 preferably has an annular seal sealing 13.

A function of the membrane 1 being to ensure sealing between the liquid contained in the first chamber 2 and that contained in the second chamber 3, this seal 13 contributes to this function being well ensured by the membrane.

In the example illustrated, channels 60, 61 are provided in the spacer 6. These channels have two parts substantially perpendicular, one of which opens into the space 2a between the bottom of the U-shaped part 12 and the spacer 6 and the other, in the orifice 6a of the spacer.

The function of these channels 60 and 61 will be explained later.

We can also note that the presence of the spacer 6 is not necessary for the operation of the device according to the invention.

As illustrated in FIG. 1, the opening 6a of the spacer 6 has a reduced size compared to the upper part 2b of chamber 2.

First of all, this tightening in bedroom 2 is not mandatory. In addition, the spacer could be made of a room with the rest of the device.

It can also be seen that the pusher 5 has lateral orifices 52, 53, the role of which will be explained in the continuation of the description.

We will now focus on the operation of the device of transmission of a volume of pressurized fluid which comes to be described, and this with reference to FIGS. 1 and 2.

In the position illustrated in FIG. 1, the membrane 1 is in the high position.

The pusher 5 and the piston 4 are also in their respective high position.

When the piston 4 is pushed into the chamber 2 by suitable means, liquid, such as oil, contained in chamber 2 also moves, which causes the downward movement of the membrane 1.

This displacement of the membrane 1 takes place against the pushing force exerted by the elastic means 7.

The membrane 1 then comes in the low position illustrated at Figure 2.

Thanks to the guide part 51 of the pusher 5, which cooperates with the bore 3a of the chamber 3, the pusher can guide the movement of the membrane in the chamber 3.

Due to the displacement of the membrane, the liquid contained in chamber 6, for example petrol, is pumped back to outside the device.

The orifices 52, 53 made in the pusher 5 allow to evacuate the fluid contained in the space 3b between the bottom of the U and the wall of the chamber 3.

The means of evacuation of the liquid contained in the chamber 3 are not illustrated in the figures.

When the device according to the invention equips a pump gasoline for a direct injection engine, chamber 3 conventionally leads into a collector which is itself connected to the engine.

In addition, at the exit of room 3 can be provided a pressure valve which is not illustrated in the figures.

In this case, the fluid contained in the chamber 3 is not evacuated only if it has reached a predetermined pressure.

When the pusher switches to the high position illustrated in the Figure 1, the membrane 1 is again pressed against the spacer 6, thanks to the elastic means 7. The membrane 1 is then in the high position illustrated in the figure 1. When changing from the low position to the high position, the membrane is still guided in its movement thanks to the guide part 51 of the pusher 5.

During this movement, the chamber 3 is again filled with liquid such as gasoline, by suitable means which are not illustrated.

When the membrane 1 returns to its high position, a volume of liquid from the first chamber is trapped between the spacer 6 and the bottom of the intermediate U-shaped portion 12, in the space referenced 2a.

The presence of the evacuation channels 60 and 61 allows the flow of liquid from this space 2a into the upper part 2b of the fluid chamber 2.

Thus, the presence of these drainage channels makes it possible to avoid an overpressure in space 2a which would be detrimental to the operation of the device.

When the diaphragm moves between the high position illustrated in Figure 1 and the low position illustrated in Figure 2, it is essentially the intermediate part 12 of the membrane which undergoes a deformation.

The mounting of the membrane in the enclosure is such that the bottom of the intermediate part 12 in U is not in contact with the walls of the enclosure or with any other part of the device. Thus, the intermediate part 12 can be unroll and unwind freely while moving the membrane during operation of the device, without the peripheral part 11 of the membrane does not undergo traction.

This is an essential difference with membranes classics who work essentially at the level of their fixation in the device.

To minimize deformation of the membrane and therefore constraints to which it is subjected, the membrane is preferably mounted in the device so that halfway, that is to say at an intermediate position between the high position illustrated in Figure 1 and the low position illustrated in Figure 2, the membrane has its shape to the free state, that is to say without constraints.

In addition, to further limit the traction forces, the connecting parts between the constituent parts of the membrane have a particular shape.

Thus, the connection part 14 between a branch of the intermediate part 12 and the peripheral part 11 has a suitable shape to match the shape of the wall 30 of bedroom 3.

Similarly, the connection part 15 between the other branch of the intermediate part 12 and the central part 10 has a suitable shape to match that of the pusher 5.

Note that the connecting parts 14 and 15 can either rest freely on the parts of the device whose they follow the form, or be adhered to these last, for example by overmolding.

As illustrated in Figure 1, the membrane 1 is pushed against the spacer 6 when it is in position high.

The opening 6a formed in the spacer 6 has edges which can cause damage to the membrane.

This is why, in the example illustrated in FIG. 1, the central part 10 of the membrane has a hollow shape 10a which makes it possible to avoid contact between the membrane and the edges of the orifice 6a.

In the example illustrated in FIG. 3, a rigid valve 8 is fixed on the central part 10 of the membrane.

The presence of this valve 8 also makes it possible to avoid a direct contact between the membrane 1 and the sharp edges of the spacer 6, when the membrane is in the high position.

When this valve 8 is provided, the evacuation channels between parts 2a and 2b of chamber 2 can be made in valve 8 itself. These channels consist of grooves, such as those referenced 8a in FIG. 3.

The thickness of the membrane is advantageously lower in the U-shaped intermediate part 12 than in the central 10 and peripheral parts 11. The stiffness of the membrane in the intermediate part 12 is thus reduced by such that the intermediate part 12 only works unwinding. Furthermore, this lower stiffness avoids transmit the forces undergone by the membrane in this intermediate part, towards the peripheral part fixed in the device.

The above description was made for a device for transmission of a volume of pressurized fluid which does not understands that a piston 4.

In the case where such a device comprises several pistons, the associated membranes can be assembled in a block unit.

This is illustrated in Figure 4 which shows a block of three membranes 41, 42 and 43 which are connected together by flat walls, so as to form a unitary block.

The device for transmitting a volume of fluid under pressure which has just been described can in particular be used to equip a fuel pump for an injection engine direct.

The reference signs inserted after the characteristics techniques set out in the claims are for the sole purpose to facilitate understanding of these and do not could limit its scope.

Claims (12)

1. A device for transmitting a volume of pressurised fluid, the device comprising at least one enclosure and one generally rounded deformable membrane (1), said membrane having a central portion (10) mobile between two extreme positions, a peripheral portion (11) fixed into said enclosure to define a first fluid chamber (2) and a second fluid chamber (3) and, between its peripheral portion (11) and its central portion (10), an intermediate portion (12) whose cross section is substantially U-shaped, which device is characterised in that the mounting of the membrane (1) in the enclosure is such that, regardless of the position of the central portion of the membrane, the curved bottom of the U-shaped intermediate portion (12) is not in contact with the walls of the enclosure or with any other part of the device, so that said intermediate portion (12) is able to roll up and unroll freely during movements of the membrane when the device operates, without applying traction to the peripheral portion (11) of the membrane.
2. A device according to claim 1, characterised in that the membrane (1) is mounted in the device so that at mid-travel the membrane has the shape it has in the free state.
3. A device according to claim 1 or claim 2, characterised in that the portions (14, 15) connecting the branches of the U-shaped intermediate portion (12) to the central portion (10) and the peripheral portion (11) of the membrane (1) rest on parts (5, 30) of the device whose shape they espouse.
4. A device according to claim 3, characterised in that said connecting portions (14, 15) are stuck to said parts (5, 30) of the device whose shape they espouse, in particular moulded onto them.
5. A device according to any of claims 1 to 4, characterised in that the intermediate portion (12) of the membrane is thinner than the central portion (10) and the peripheral portion (11) of the membrane.
6. A device according to any of claims 1 to 5, characterised in that it includes a plunger (5) spring-mounted in the second fluid chamber (3) and fixed to the central portion (10) of the membrane (1).
7. A device according to claim 6, characterised in that said plunger (5) has a portion (51) for guiding the movement of the membrane (1).
8. A device according to any of claims 1 to 7, characterised in that the membrane (1) has in its central portion (10) means for preventing it from being damaged by sharp edges of said enclosure, said means including a recessed shape (10a) or a rigid valve (8) fixed to the membrane.
9. A device according to any of claims 1 to 8, characterised in that it includes means for evacuating from the first chamber (2) fluid likely to be trapped between said enclosure and the U-shaped intermediate portion (12) of the membrane, said means including evacuation passages (60, 61; 8a) in the device itself or in said valve (8).
10. A device according to any of claims 1 to 9, characterised in that the peripheral portion (11) of the membrane (1) includes a seal (13).
11. A device according to any of claims 1 to 10, characterised in that it comprises a plurality of membranes (41, 42, 43) formed in one piece.
12. A pump, such a fuel pump for a fuel-injected engine, equipped with a device according to any of claims 1 to 11 for transmitting a volume of pressurised fluid.

Images