EP3189238A1

EP3189238A1 - Pressure accumulator comprising an insert

Info

Publication number: EP3189238A1
Application number: EP15767222.1A
Authority: EP
Inventors: Wilfried LEMASSON; Gregory Schott; Eric Boucaux
Original assignee: Plastic Omnium Advanced Innovation and Research SA
Current assignee: Plastic Omnium Advanced Innovation and Research SA
Priority date: 2014-09-04
Filing date: 2015-09-04
Publication date: 2017-07-12
Also published as: FR3025565A1; WO2016034823A1; FR3025565B1; CN106795895A

Abstract

This vehicle pressure accumulator comprises a vessel (22) made of thermoplastic, a filament winding (24) around the vessel, a bladder and an insert (20, 30). The insert is made predominantly of a first material and at least partially of a second material which is a thermoplastic that can be welded to the material of which the vessel is made. In addition, the insert is of one piece and shaped in such a way that after the vessel has been welded it can be separated only by destroying the vessel or the insert, and it further comprises means to ensure sealing between the first material and the second material.

Description

Pressure accumulator comprising an insert

The invention relates to vehicle pressure accumulators.

Some types of hybrid vehicles include a hydraulic pump / motor system that can charge hydraulic accumulators with oil to store energy in the form of a pressure reserve. A hydraulic machine connected to the driving wheels of the vehicle can operate as a motor to deliver mechanical power to the wheels by taking the energy stored in the hydraulic accumulators, or as a pump to recharge these hydraulic accumulators during the braking of the vehicle, in order to recover at less in part the kinetic energy of the vehicle.

A particular type of hydraulic accumulator is a bladder accumulator which generally comprises an enclosure within which is disposed a bladder containing gas, preferably nitrogen. During energy recovery, oil is sent into the enclosure around the bladder. Thus, the bladder full of gas is compressed by the oil and, reciprocally, the bladder thus compressed tends to push the oil out of the enclosure by subjecting it to the increased pressure of the gas enclosed in the bladder. When it is desired to recover the energy stored in the accumulator, the oil is released from the enclosure and this oil, which transmits the pressure of the compressed gas into the bladder, supplies energy to a hydraulic motor.

Historically, several types of accumulators are known and distinguished according to the material of which they are made. The type I accumulators were totally metallic. Type II and III accumulators consist of fiber-coated metal, in part for Type II loudspeakers, entirely on Type III loudspeakers. Today, type IV enclosures include a plastic enclosure on which are wound filaments of composite materials embedded in a resin. This type of Type IV battery provides adequate strength while being lighter than type I, II, and III metal enclosures.

In order to allow a connection between the enclosure and the outside and between the bladder and the outside, metal inserts are placed on the enclosure, inserts whose function is to enable metal parts to be connected to the enclosure. or with the bladder, which are two non-metallic elements, while ensuring an optimal seal.

Known for this purpose inserts mounted in several parts. Two types of inserts are mainly known. Valve inserts, for connecting conduits for bringing oil in and out of the enclosure, and valve inserts for connecting gas lines to the bladder. A valve insert includes several components, namely a valve body, support members and connecting elements such as nuts and rings, to prevent extrusion of the bladder. A valve insert also includes a plurality of components, namely generally a valve body that allows the bladder to remain closed once it is filled with gas, and the same type of connecting elements as a valve insert for securing the insert and the valve body on the enclosure. The inserts of these two types all include at least one component which is at least partially overmolded with thermoplastic material, such as HDPE, to facilitate its welding to the plastic enclosure, which enclosure has been previously formed by blowing a parison. After welding of this component on the enclosure, the other components of the insert are arranged relative to each other, then they are fixed by screwing. Sealing is achieved by interposing a seal between the portion of the insert molded HDPE and the enclosure. Once the insert is in place, composite fibers are wrapped around the enclosure, for example carbon fibers coated with epoxy resin. These fibers improve the strength of the enclosure at the same time as they hold the insert in place.

However, such an arrangement causes risks of damage to the part of the overmolded insert, because this part is interspersed between two components screwed together and it undergoes a compression that can cause perforations and damage the tightness of the whole.

In addition, the entire assembly of the insert within the enclosure is now done manually. The assembly is therefore relatively long and complex because of the number of parts involved, especially since some parts are only present to hold the assembly in place.

An object of the invention is to provide a sealing system which does not present a risk of leakage.

Another object of the invention is to provide a simplified assembly of the insert within the enclosure.

For this purpose, according to the invention, there is provided a vehicle pressure accumulator, comprising an enclosure of thermoplastic material, a filament winding around the enclosure, a bladder and an insert, the insert consisting mainly of a first material and at least in part by a second material which is a thermoplastic material capable of being welded with the material constituting the enclosure, the insert being integral and shaped in such a way that it can not be separated after welding of the enclosure except by destruction of this last or the insert, and the insert further comprising means capable of sealing between the first material and the second material. Thermoplastic means any thermoplastic polymer, including thermoplastic elastomers, and mixtures thereof. The term "polymer" denotes both homopolymers and copolymers (especially binary or ternary). Examples of such copolymers are, but are not limited to: random copolymers, block copolymers, block copolymers and graft copolymers.

Any type of thermoplastic polymer or copolymer whose melting point is below the decomposition temperature is suitable. Synthetic thermoplastics having a melting range spread over at least 10 degrees Celsius are particularly suitable. Examples of such materials are those having a polydispersion of their molecular weight.

In particular, it is possible to use polyolefins, thermoplastic polyesters, polyketones, polyamides and their copolymers. A mixture of polymers or copolymers may also be used, as well as a mixture of polymeric materials with inorganic, organic and / or natural fillers such as, for example, but not limited to: carbon, clays, salts and the like. inorganic derivatives, natural or polymeric fibers. It is also possible to use multilayer structures consisting of stacked and solid layers comprising at least one of the polymers or copolymers described above.

A polymer often used is polyethylene. Excellent results can be obtained with high density polyethylene (HDPE).

The wall of the enclosure may consist of a single layer of thermoplastic material or two layers. One or more other possible additional layers may advantageously consist of layers of liquid and / or gas barrier material. Preferably, the nature and the thickness of the barrier layer are chosen so as to limit as much as possible the permeability of liquids and gases in contact with the inner surface of the enclosure. Advantageously, this layer may be based on a barrier resin, that is to say a resin impervious to fuel such as EVOH for example (ethylene copolymer - partially hydrolysed vinyl acetate).

"Monoblock" means a piece that can not be divided into several parts, except to destroy it. We will also talk about a piece that can not be dismantled and whose only way to separate it into different elements is to destroy it.

Thus, the insert being integral, it can be inserted and welded its overmolded portion during the blowing of the parison so as to facilitate and accelerate assembly of the assembly.

Preferably, the first material is metal.

Advantageously, the insert comprises at least one retention member of the bladder inside the enclosure.

Preferably, the retention member is a shutter capable of closing and opening a passageway between the inside and outside of the enclosure.

Advantageously, the retention member is a grid.

Thus, the orifices of the grid are large enough to let the fluid and small enough to prevent the bladder from leaving the enclosure. Any organ capable of performing these functions is similar to a grid in the sense of the invention.

Advantageously, the insert comprises a circular groove between two shoulders, adapted to accommodate the enclosure.

Thus, the insert is held in place on the groove and can not move relative to the enclosure, because of the shoulders.

Preferably, the means ensuring the sealing of the insert are an additive to the thermoplastic material of the insert allowing its adhesion with the enclosure

Alternatively, the means ensuring the sealing of the insert may consist of a seal.

Thus, the sealing system, whether made by joint or by adhesion, no longer presents a risk of perforation.

Preferably, the seal is located in a circumferential groove housing. Advantageously, the retention member is movably mounted relative to the insert. Thus, the retention member may be a valve, a valve or any other element that moves to close or open the passageway.

The subject of the invention is also a method for manufacturing a pressure accumulator as described above, in which:

a bladder is fixed to an insert;

a parison is placed around the bladder in an open mold;

- the mold is closed;

the parison is blown so as to form the enclosure;

- An overmolded part of the insert formed by the second material is welded to the parison during the closure of the mold.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which:

- Figure 1 illustrates a longitudinal longitudinal sectional view of a battery of the prior art;

FIG. 2 illustrates a view in longitudinal section of an insert of the prior art; - Figure 3 illustrates a longitudinal sectional view of an insert according to a first embodiment of the invention;

FIG. 4 illustrates a longitudinal sectional view of an insert according to a second embodiment of the invention;

- Figure 5 illustrates a longitudinal sectional view of a pressure accumulator having inserts according to the invention;

FIG. 6 illustrates a perspective view of an enclosure of a pressure accumulator;

- Figures 7 and 8 illustrate inserts respectively comprising a seal according to the first two embodiments and an additive adhering in the molded part according to a third embodiment; and

- Figures 9 to 12 schematically illustrate steps of a method of manufacturing an assembly comprising an enclosure and according to the invention.

FIG. 1 illustrates a pressure accumulator 1 for a vehicle according to the prior art, comprising an enclosure 2 made of high density polyethylene (HDPE) around which fibers 3 made of composite material are wound. The accumulator 1 comprises a bladder 4 located inside the chamber 2, a valve insert 5 to which a valve 6 is connected, and a valve insert 7 to which a valve 8 is connected. The latter is connected to the bladder 4.

In the context of the invention, a bladder comprises a variable volume organ. For example, a bladder may comprise flexible walls so that it is able to inflate and deflate. It can change shape when compressed or otherwise tense, and can return to its original shape when it is no longer subject to any pressure. This is particularly the case with the bladder 4.

The chamber 2 is tubular in shape with spherical ends. It has two orifices 11 and 12 respectively at each of its ends where the inserts 5 and 7 are located above.

The method of using a bladder pressure accumulator in general and the type of the invention in particular is as follows.

Before normal operation of the vehicle comprising the accumulator, the valve is opened at the valve insert so as to introduce gas into the bladder. Once the bladder is filled with a predetermined amount of gas, the valve is closed.

At the valve insert, the valve serves only to prevent the bladder from coming out of the enclosure (this is called "extrusion" of the bladder). Upstream of the valve, an element allows to open or close, in normal operation of the vehicle, the conduit for introducing oil into the chamber from a hydraulic circuit (not shown). When the driver of the vehicle brakes, it is possible, by a mechanism that is not described here, to transform the kinetic energy lost during braking into hydraulic energy, by bringing oil from the hydraulic circuit into the enclosure, then we close the path of passage of the oil. The oil contained in the chamber compresses then the bladder full of gas. The braking energy is thus "stored" in the pressure accumulator.

When it is desired to use the energy thus stored, the oil passageway is opened and, if the pressure exerted by the bladder filled with gas on the oil is greater than that exerted by the oil on the bladder. , then the oil is removed from the enclosure, to go into the hydraulic circuit that is connected to the vehicle's engine systems. The oil thus transmits the gas pressure of the chamber into the hydraulic circuit. The bladder regains a larger volume. This corresponds to the "destocking" of energy for its use in the engines.

Figure 2 is an enlarged view of a valve insert 5 'of the prior art.

It consists of several pieces that serve both to maintain it in place and to prevent the bladder 4 'to leave the enclosure 2'. Thus, there is notably an outer body 13 for holding the insert at the orifice 12 'of the enclosure, an inner body 14 surrounding the valve 6', an intermediate body 15, and an anti-rotation ring. extrusion 16, an internal shoulder ring 17 and an outer shoulder ring 17 '. Most elements of the insert 5 'are made of metal.

During assembly, the various elements of the insert 5 'and the valve, are manually mounted in the chamber 2' already blown. Thus, we begin by inserting the inner shouldered ring 17 in the enclosure. It may be necessary for this purpose to split the inner shoulder ring 17 and to deform it to pass through the orifice 19 of the enclosure. Then the inner body 14 is inserted and positioned in the internal shoulder ring 17. Then, the outer shoulder ring 17 'is screwed onto the inner body 14 and then to the outer body 13. All these operations are carried out since outside the enclosure and claim a dexterity and patience not insignificant.

As already explained, these operations are long, complex and entail risks of injury for the operator responsible for assembly. In addition, the arrangement of the parts is such that the outer body 13 of the insert 5 'and the inner shouldered ring 17 of the metal insert compress between them a portion 18 of the enclosure 2' HDPE. There is therefore a risk of perforation of the enclosure at this location. If necessary, the oil contained in the chamber 2 'may leak outwards. The seal between the insert 5 'and the enclosure 2' is not optimal.

Figure 3 shows a valve insert 20 according to a first embodiment of the invention. It is monobloc. "Monoblock" means, in accordance with what has already been explained, a piece that is not removable, the only way to divide it into various elements is to destroy it. This insert 20 is located at an orifice 19 of the same type as that provided for the valve insert of the enclosure of FIG. 1. Its shape is symmetrical about an axis 100. It comprises a groove 21, on which is held in place the chamber 22 of the accumulator, at the orifice 19 thereof. At the bottom of this groove 21, is provided a circular housing (or small groove) 23 'about the axis 100, adapted to collect a seal 23. This seal 23 allows for sealing between the enclosure and the insert . The fiber winding 24 is located on the entire outer surface of the enclosure 22, particularly at the orifice 19. At this level, the fibers 24 make it possible to reinforce the holding in place of the insert 20 on the 22. The groove 23 of the insert is surrounded, in the direction of the axis 100, by two shoulders 25 and 26. The upper shoulder 25 of the insert is located outside the chamber 22, while that the lower shoulder 26, wider, is located inside the chamber 22. The surface of the insert 20 which goes from one shoulder to another through the groove of the seal 23, is overmolded HDPE, material identical to that constituting the enclosure. Thus, the portion of the lower shoulder 26 of the insert, overmolded with HDPE, is welded to the enclosure 22 HDPE. Alternatively, any material capable of being welded with HDPE may be used to overmold the metal insert.

The insert comprises a valve 27. The latter is mounted to move in translation along the axis 100 in the valve insert 20. It makes it possible to retain the bladder (not visible) when the volume of the latter increases, so that that it does not leave the enclosure 22. Finally the insert 20 is connected to a passageway 28, which is shown but not detailed because it is not part of the invention. This passageway 28 makes it possible to circulate the oil between the enclosure 22 and a hydraulic circuit (not shown) outside the enclosure.

Figure 4 illustrates a second embodiment of the invention. This time this is a valve insert 30. This insert 30 also has a symmetrical shape about the axis 100, and is positioned at the end of the chamber opposite that of the valve insert 20 The insert 30 has the same general characteristics regarding its shape as the valve insert 20, namely a groove 31 situated at the orifice 39 of the enclosure 22, and two shoulders 35 and 36, respectively external and 22. The same parts as the valve insert 20 are overmolded with HDPE and welded to the enclosure. In this figure, the valve is not visible. The insert 30 also comprises a seal 33 housed in the groove 31.

Figure 5 shows the two previous inserts in a pressure accumulator 70 for vehicle. The bladder is not visible here.

Figure 6 is an outside view of an enclosure 32 of the type used in pressure accumulators, where the fiber winding is distinguished over the entire outer surface of the enclosure.

In a third embodiment, the insert, whether it is a valve insert or a valve insert, does not have a seal for sealing. This type of insert is visible in FIG. 8. This schematic view is to be compared with that of FIG. 7, where an insert with a seal 43 is distinguished.

The insert 50 of FIG. 8 comprises an additive in the over-molded part 57 made of HDPE of the insert 50, an adhesive additive such as a functionalized polymer ("grafted polymer"), in this case maleic anhydrous polyethylene, which makes it possible to glue the insert 50 and the enclosure 52 so that the seal between the insert 50 and the enclosure 22 is made by adhesion.

We will now describe a method of manufacturing an enclosure of a pressure accumulator comprising inserts according to the invention, with reference to Figures 9 to 12 which schematically illustrate the process.

Inside an unillustrated blowing installation, valve and valve inserts 20 according to the invention and an empty bladder 4 'are placed in the respective positions where these elements will be located. once the speaker is done. Thus, the bladder 4 'is attached to the valve insert 30, the valve insert 20 being located at the opposite end of the bladder 4', without contact therewith.

The chamber of the accumulator is then made around this assembly.

For this purpose, a parison 22 'is extruded around the inserts 30 and 20 and the bladder 4' between two parts 61 and 62 of an open mold. Then the mold is closed by directing its two parts 61 and 62 towards each other. These close on the parison 22 ', pinch so that the parison 22' closes at the grooves 23 and 33 of each insert. Simultaneously, the parison 22 'is compression welded at the lower shoulders 26 and 36 overmolded with HDPE of each insert 20 and 30. Then, the parison 22' is blown by injecting air into the parison 22 '. by a known method and not illustrated here. The walls of the parison are then crushed against the walls of the two parts 61 and 62 of the mold, and thus take the form of the chamber 22 of the pressure accumulator.

At the end of the process, the two parts of the mold are moved apart so as to remove the enclosure comprising the two inserts 20 and 30 and the bladder 4 '.

Thus, contrary to what is done in the state of the art, it was not necessary to mount the inserts in several parts in an enclosure, after having blown the latter. The blowing process of the enclosure and the insertion of the inserts take place at the same time, without risk of injury, which saves a lot of time. The material constituting the insert may comprise: steel, stainless steel, brass, aluminum. Other types of alloys are possible.

In another embodiment of the invention not illustrated, the insert is not made of metal but of composite material. Thus, it may be composed of charged or reinforced material, of polysulphonic type thermoplastic such as polysulfide of phenylene (also referred to as "PPS").

Of course, we can bring to the invention many changes without departing from the scope thereof.

Claims

A pressure accumulator (70) for a vehicle, comprising an enclosure (22) of thermoplastic material, a filament winding (24) around the enclosure, a bladder (4, 4 ') and an insert (20; 30; 40; 50) ), the insert being constituted mainly by a first material and at least partly by a second material which is a thermoplastic material capable of being welded with the material constituting the enclosure (22), the insert being integral and shaped so it can only be separated after welding of the enclosure by destruction of the latter or of the insert, and in that the insert further comprises means (23; 33; 43; 57) capable of sealing between the first matter and the second matter.

Accumulator according to the preceding claim, wherein the first material is metal.

Accumulator according to any one of the preceding claims, wherein the insert comprises at least one bladder retention member inside the enclosure.

Accumulator according to the preceding claim, wherein the retention member is a shutter adapted to close and open a passageway between the inside and outside of the enclosure.

Accumulator according to claim 3, wherein the retention member is a gate.

Accumulator according to any one of the preceding claims, wherein the insert comprises a circular groove (23; 33; 43) between two shoulders, adapted to collect the enclosure.

Accumulator according to at least one of the preceding claims, wherein the means ensuring the sealing of the insert are an additive (57) to the thermoplastic material of the insert allowing its adhesion with the enclosure (22).

8. Accumulator according to at least one of claims 1 to 6, in wherein the sealing means of the insert consist of a seal (23; 33; 43).

9. Accumulator according to the preceding claim, wherein the seal is located in a circumferential housing (23; 33; 43) of the groove.

10. Accumulator according to at least one of claims 3 to 9, wherein the retention member (27) is movably mounted relative to the insert.

A method of manufacturing a pressure accumulator according to at least one of claims 1 to 10, wherein:

a bladder (4 ') is fixed to an insert (30);

a parison (22 ') is placed around the bladder in an open mold (61, 62);

- the mold is closed;

the parison is blown so as to form the enclosure (22);