Vehicle with gaseous fuel and automatic purge system

FIELD OF THE INVENTION

p0001The present invention relates to gas storage tanks in a motor vehicle regardless of its engine, particularly but not only suitable for storing gaseous hydrogen and / or oxygen gas stored in a vehicle fuel cell .

STATE OF THE ART

p0002One problem that gas storage installation on a vehicle is the danger in case of fire in the vicinity of the tank, and in case of excessive rise in pressure. It has been proposed for liquefied petroleum relief valves gas vehicles to leave gradually flee the gas in case of overpressure, eg caused by abnormal heating due to fire, as it must at all costs avoid the risk explosion, even that fuel feeds a fire under a restricted flow. Thus, safety valves that are opened irreversibly under the effect of a warm-up have already been proposed in the prior art: the reader is referred for example the request<patcit id="pcit0001" dnum="JP60073200A"><text>JP60 / 073200</text></patcit> which discloses such a safety valve wherein the sealing member is a membrane closing an orifice and a final element controlling opening is a pellet made of shape memory alloy carrying a needle, so that, in case of temperature rise, the pellet shape memory alloy changes its shape and pushes the needle against the membrane to cause rupture of said membrane.

p0003However, it is not sufficiently robust solution to find location in an automobile and play a security role only knows in case of fire, and play it for sure in case of fire. Thus, for example, knows no satisfactory solution to prevent the gas escaping fuel tank aggravates a fire that could have occurred without the fuel supply system is the cause. Thus, in case of accident involving several vehicles, if one of these vehicles lose its fuel then spreads on the floor, for example in gasoline, there is a significant risk that gasoline will ignite and that another vehicle is immobilized over the fire. In this case, if fire occurs in the tank of a gaseous fuel of the other vehicle, assuming that the latter is equipped with a discharge valve in case of overpressure, it must first wait for the tank pressure rises before such safety play its role. Also, if the pressure prevailing in the tank is low because the residual fuel amount is small, it will take longer before such safety both to the point that the material of the tank may have lost its mechanical properties to the point of surrender and thus cause an explosion even before the pressure is high enough that the discharge valve in case of overpressure action.

p0004If we could act sooner to purge the reservoir would improve vehicle safety conditions storing a gaseous fuel under pressure, including fuel cell vehicles that run on hydrogen.

p0005In the field of fuel cell vehicles, the patent application <patcit id="pcit0002" dnum="WO03035419A"><text>WO03 / 035419</text></patcit> provides means for removing hydrogen is not consumed by the battery, collecting leaks around the stack, collecting leakage around the tank and installing a pressure relief valve on said reservoir. Again, there are no plans to improve safety in case of fire.

p0006The document <patcit id="pcit0003" dnum="EP1070620A"><text>EP 1070620</text></patcit> discloses a vehicle according to the preamble of claim 1 and a thermally triggered safety valve.

BRIEF DESCRIPTION OF THE INVENTI0N

p0007An object of the invention to ensure that, in case of fire, the fluid reservoir under pressure existing on board a vehicle is automatically purged into such a short time as possible, taking the fluid as far as possible to the place where the fire started.

p0008This objective is achieved according to the invention by a vehicle as defined in claim 1, or a valve as defined in claim 9.

p0009The invention provides a vehicle equipped with a tank for storing a fluid under pressure, said reservoir being connected to at least one purge line, the said purge line leading to at least one discharge orifice, the purge line being connected to the reservoir by means of at least one safety valve, characterized in that the safety valve is a thermally triggered valve, normally closed and capable of opening spontaneously under the effect of a temperature rise the safety valve being installed in a predefined area of ​​the vehicle and the discharge orifice being distant from the said predefined region.

p0010The invention also provides a thermal release valve having a release mechanism using a triggering member made of a shape memory alloy of characteristics such that, when subjected once to a temperature increase causing it to beyond a predefined temperature threshold, it adopts a memorized shape and adopts it thermally irreversible.

p0011Two practical embodiments of an application to a hydrogen tank are described below.

p0012The first embodiment uses a safety valve having an opening mechanism controlled by a pellet made of shape memory material. Another embodiment provides a safety valve controlled by a mechanism comprising a capsule destroyed by the effect of heat. In both cases, the two embodiments have the advantage that they work even when the electrical system controlling the entire operation of the vehicle is off. Indeed, the elements required to control the safety valves operate on thermomechanical principles.

p0013One can for example install the reservoir itself to the vehicle rear. in particular it can also be installed in the floor, in the central part of it because it is an area unlikely to be distorted even when particularly violent crash of the vehicle. It is possible to route the pipeline to ensure proper flow of pressurized fluid from the vehicle passing in a particularly sensitive area fire and install the safety valve there.

p0014For example, determining that there is a risk that a fire exists under the floor of a vehicle, the drain line can travel under the floor in order to install this place a thermally triggered valve, and the purge pipe continues until the discharge port which is disposed away from the floor, for example on the vehicle roof. It is this application which is illustrated in more detail below.

p0015But there are many other possible applications. If we consider that we must guard against the consequences of a fire in the engine compartment, the pipe can also be installed to reach the front of the vehicle, for example in the compartment housing the battery fuel producing electric power for the vehicle, so as to install the thermally triggered valve, and the purge pipe travels to the discharge orifice which is arranged away from this compartment, for example at the rear of the vehicle. Can be treated in the same way a number of areas where we consider there is a significant risk of fire starting and which we want to cancel or at least reduce the consequences. One can for example treat the interior of a vehicle. the tank of any gas having some danger can be treated, including all gases cited above.

p0016Let us add that one can install in parallel several drain pipes starting all of a single reservoir, leading all the same discharge port, each vehicle passing through a zone in which a fire is likely to arise, in order to install a thermally triggered valve.

p0017A nonlimiting example of use of the invention is illustrated below in the case where the tank is of a particular type, described in patent application <patcit id="pcit0004" dnum="EP03028056A"><text>EP 03 / 028056.4</text></patcit> filed on 8 December 2003.

BRIEF DESCRIPTION OF FIGURES

p0018In the following figures:<ul><li>The <figref idrefs="f0001">figure 1</figref> is a view of a passenger car showing the general layout of the organs of the invention;</li><li>The <figref idrefs="f0002">2</figref> shows a safety valve in a normally closed configuration, associated with a multi-cell tank;</li><li>The <figref idrefs="f0003">3</figref> shows the same safety valve than the <figref idrefs="f0002">2</figref>, This time in the open configuration;</li><li>The <figref idrefs="f0004">4</figref> shows another safety valve in a normally closed configuration, associated with the same multi-cell tank;</li><li>The <figref idrefs="f0005">5</figref> shows yet another safety valve in a normally closed configuration, always associated to the same tank.</li></ul>

DESCRIPTION REALISATI0N BEST MODE OF THE INVENTION

p0019To the <figref idrefs="f0001">figure 1</figref>There is shown a passenger vehicle having a floor 10 including at least one tank 2 to the storage on the vehicle of a pressurized gas. It may be any fluid stored at high pressure, for example liquefied petroleum gas, compressed natural gas or compressed hydrogen, or oxygen. In the following, it is assumed that the tank 2 is a tank for storing one gaseous fluid, for example hydrogen gas, without this being limiting.

p0020the <figref idrefs="f0002">figures 2</figref> and following, it is seen that the container 2 comprises a very large number of cells 20 of small volume, interconnected. The reservoir comprises a base 21 which has as many recesses that cell 20. The recesses all extend from a first face 22 to the opposite face 23. They are all opening at the first face 22 and not opening at the opposite face 23. Each recess is closed by a plug 24, except where one installs a security valve, which then takes the place of such a plug. The caps 24 are screwed onto the base 21, a seal 24A is provided in a suitable groove. For details on the constitution of the reservoir 2, the reader should refer to the patent application<patcit id="pcit0005" dnum="EP03028056A"><text>EP 03 / 028056.4</text></patcit> supra.

p0021A shielding plate 25 is pressed against the lower surface 23 of the tank 2. A header pipe 3 is disposed just under the cover plate 25 longitudinally of the vehicle. This collection pipe 3 is here very flat rectangular section, which also appears well on these figures. The vehicle front side, the header pipe 3 is closed by a wall 31 of the vehicle rear side, the header pipe 3 is one or two shanks 32 which are coupled pipes 33. The header pipe 3 and pipes 33 together form the drain line. The pipes 33 join the discharge ports 34. These are located on the rear vertical wall 11 of the vehicle 1 at a level near the pavilion 12.

p0022The header pipe 3 comprises a number of first bores 30 (see <figref idrefs="f0002">2</figref>) Formed at least on one of the large faces of the header pipe 3. Furthermore, the header pipe 3 comprises a number of second holes 30B formed on the other of the large faces of the header pipe and facing each the first bores 30. the first holes and second holes 30B are made for example at five locations as seen in the <figref idrefs="f0001">figure 1</figref>. The first and second holes 30 and 30B are exactly opposite of five cells 20 of the reservoir 2. The shroud 25 also has five holes, too exactly in the same five cells 20 of the reservoir 2.

p0023Safety valves are screwed into the tank 2, instead of as many plugs 24 as already reported, that is to say opposite the five places mentioned above. The header pipe 3 is held pressed against the shroud 25 and therefore against the tank 2 so as to ensure the communication with the safety valves and the sealing with respect to the outside. In this example, we used three thermal switch valves 5 and two pressure threshold valve 6, the structure of each of these valve types being detailed below. Thus, the header pipe 3 allows the parallel connection of several cells 20 and, when one or more of the safety valves for certain cells 20 is opened, the gaseous fluid escaping through the or safety valves is collected by the draining conduit and discharged to one or more discharge port 34.

p0024We now turn to the details of making a thermally triggered safety valve 5. A first embodiment is illustrated in <figref idrefs="f0002">figures 2</figref> and <figref idrefs="f0003">3</figref>.

p0025There is shown a body 50 having a thread 51 to be screwed onto the reservoir 2. This body 50 comprises a seat 52 closed by a ball 53 can be installed a spring 59 that causes a moderate preload tending to push the ball 53 against its seat 52. Moreover, the pressure of the fluid inside the cell 20, the higher the ball 53 tends to press firmly against the seat 52, thus ensuring a perfect seal.

p0026From below the seat 52, there is shown a chamber 54 communicating with conduit 55 terminating on the side wall of the body 50. The center body 50 includes a bore within which is mounted a sleeve 56 which guide a central piston 57. on the opposite side to the seat 52, the body 50 comprises a collar 58 threadedly receiving an obturator 70. the obturator has on one side a central cylindrical wall 73 and a peripheral ring 72. on the inner side, the shutter 70 traps a pellet 7 made of shape memory alloy, which is also supported on a ring 71, itself mounted against the body 50. Note that, when the body 50 has been screwed onto the container 2, the body 50 from the tank 2. with the first 30 and second holes 30B made on collecting pipe 3, and through similar holes made on the protective plate 25, when installing said protective plate and collecting duct , the flange 58 of each body 50 remains accessible from the outside. Can be screwed into the stopper 70 on the body 50 while trapping the protective plate 25 and the header pipe 3 through the ring 72 of each shutter 70, said ring pressing the exterior wall of the header pipe 3. the header pipe 3 is thus sealingly held on the body 50.

p0027The <figref idrefs="f0002">figures 2</figref> and <figref idrefs="f0003">3</figref> show a shutter 70 of blind type, that is to say it comprises a thin central cylindrical wall 73, to isolate the wafer 7 from the outside. This has the advantage of providing mechanical protection against external attacks, without significantly delaying the heating of the wafer 7. But we can also consider using a fastener free from this thin central cylindrical wall, allowing direct contact of the heat source (flame) with the wafer 7 to a minimum reaction time.

p0028The valve proposed by the invention may be useful in applications other than the one passenger vehicle described above. She is kind to permanently open as soon as it is subjected to a first temperature rise. It comprises a ball cooperating with a seat and a spring pushing the ball against the seat to maintain the valve in a normally closed position at ambient temperature, and has an alloy pellet shape memory having a first shape at ambient temperature, a piston being interposed between the ball and the pellet. According to an essential characteristic of the valve according to the invention, the shape memory alloy pellet is type adopting a stored form with the first time it is subjected to a temperature rise. Thus, the piston pushes the ball out of his seat when the pellet switches from the first shape to the memorized shape.

p0029It is known that the shape memory alloys are transformed from a crystalline structure to another during the passage in a specific temperature zone. It is this transformation that the shape memory alloys derive their properties and their denomination. As a result, one can give to any object made of shape-memory alloy two different shapes: one at low temperature and the other at high temperature called below "memorized shape." The temperature zone in which occurs the transformation depends on the composition of this alloy and education that is subjected to this alloy exerting some mechanical stresses in the temperature conditions specified.

p0030This having been established, as regards the realization of the wafer 7, for example using a NiTi shape memory metal. This alloy undergoes a change in its crystal structure when cooled, ie he spends his hard condition, austenitic structure (high temperature), its easily deformable state, martensitic structure (low temperature) . The transition temperature chosen for the wafer 7 is about 90 ° C (to within + or - 5 ° C). A material having the required properties is well known to those skilled in the art; for information, it is available for example from Special Metals Corporation, New Hartford, NY. The pellet as initial Fonne a spherical cap (similar to that contained in the<figref idrefs="f0003">3</figref>). At room temperature, the pellet is in the martensite state (soft). It can be relatively easily deformed mechanically so as to reach an approximately plate (disk shaped, illustrated in<figref idrefs="f0002">2</figref>). When the chip joins a temperature of about 90 ° C, it changes phase and changes from Martensite Austenite state to state (hard). It thus returns to its original shape (memorized shape) which is a spherical cap. This form persists even after returning to room temperature. This means that the material chosen is irreversible in its form while being reversible in its structure as it rose from the Austenite state (hard) in the martensite state (soft). The only way to get him back to a disk shape is an external mechanical action.

p0031Preferably, in position normally closed at room temperature, there remains a slight clearance between the wafer 7, the central plunger 57 and the ball 53, so that it remains firmly pressed against its seat 52. At the <figref idrefs="f0002">2</figref>, It is seen the shape of the chip 7 at room temperature.

p0032To the <figref idrefs="f0003">3</figref>, It is seen that the shape takes the same pellet 7 under the effect of a rise in temperature (memorized shape). The degree of deformation depends on the sizing of the pad 7 itself. For a pellet produced as described above, the deformation starts when the wafer 7 has reached the temperature of 75 ° C. Once caught the mounting kits, the pellet is developing a major effort. As soon as we raised enough ball, the force developed by the chip decreases, but still enough to fight against the force developed by the spring. It reached the maximum deformation as shown in<figref idrefs="f0003">3</figref> 7 when the pellet has reached the temperature of 100 ° C. Moreover, it turns out that such a pellet 7 is able to develop a big enough effort to push the piston 57 against internal pressure that is applied on the ball side of the cell containing the fluid under high pressure ( of the order of 200 to 300 bar), and against the pressure of a retaining spring.

p0033As already indicated, after thermal stress and subsequent cooling in such a pellet 7, if one wished to make it resume its initial shape, for example for reconditioning of the thermally triggered safety valve 5, it is necessary to mechanically deform. With the pellet 7, because a sufficient heating made him permanently said memorized shape, the valve 5 opens certain and remains open even if the temperature rise decreases or ceases.

p0034Just indicated that the thermal release valve 5 has a pellet 7 made of shape memory alloy. This is a preferred embodiment of a release mechanism using a triggering member made of a shape memory alloy, said shape memory alloy being such that it adopts characteristics when subjected a first time to a rise in temperature causing it beyond a predefined temperature threshold, a memorized shape, and this thermally irreversibly.

p0035Of course, a number of seals are used to ensure perfect sealing of the assembly, as shown clearly in the drawings without the need of further explanation. The ducts 55 leading to the side wall of the body 50 are in direct communication with the header pipe 3 so that, in case of opening of the thermally triggered safety valve 5, the gases enter the chamber 54 then cheminent through conduits 55 leading to the side wall of the body 50 where they join the header pipe 3, without being able to escape into the external environment at the thermally triggered safety valve 5 of the header pipe 3.

p0036It is obviously possible to add other types of valves such as a pressure threshold valve 6 such as that shown in <figref idrefs="f0005">5</figref>. This uses the same body 50 as the body of the thermally triggered valve 5. From the side of the tank body 50 that receives an insert 63 having at its center 630 a calibrated rupture membrane. The insert 63 is interchangeable. The chamber 54 is closed by a cap 67. The body 50 receives a nut 70 of a shutter-type blind identical to that used in<figref idrefs="f0001">figures 1</figref> and <figref idrefs="f0002">2</figref>.

p0037Thus, in a particularly advantageous embodiment of the invention, the tank of the vehicle has a plurality of cells interconnected to provide fluid flow necessary for the use of the vehicle, at least two cells are each connected to the bleed line , each cell being connected to the purge line by means of at least one safety valve, one of the safety valves being the said thermally triggered valve, the other of the safety valves being a pressure threshold valve automatically and permanently opening (opening irreversible destruction for example by a lid) beyond a predefined pressure threshold.

p0038To the <figref idrefs="f0004">4</figref>There is shown an alternative embodiment of a thermal release valve 8, wherein the release mechanism uses a destructible capsule under the effect of heat (not used in the <figref idrefs="f0001">figure 1</figref>). There is shown a body 80 having a thread 81 to be screwed onto the reservoir 2. This body 80 has a first bore 82 closed by a central piston 83 having a head 88 and a skirt 880 defining a hollow central area open on one side and closed on the other side by the head 88. the body comprises a central duct 86 defining a second bore 84 having a slightly larger diameter than the first bore 82. the central piston 83 is guided in the second bore 84. the interior of the central duct 86 communicates with one or more ducts 85 leading to the outer wall of the chimney 86. the chimney 86 is closed by a shutter 87. a capsule 89 is interposed between the shutter 87 and a support washer 90 deposited against the head 88 of the piston 83. the capsule 89 breaks at a preset temperature. For example, one can find such capsules crashing at a temperature of about 90 ° C in JOB GmbH Kurt-Fischer-Strasse 30, D-22926 Ahrensburg.

p0039Body 80 also comprises a third bore 91 within which is mounted a sleeve 92 defining a substantially annular space around the chimney 86. This space is in communication with the header pipe 3. When the capsule 89 is broken, more nothing prevents the central piston 83, which acts on the fluid pressure in the cell 20, backward against the shutter 87, thereby the cell 20 in connection with the interior of the chimney 86, with the duct or ducts 85, with the substantially annular space surrounding the fireplace, and finally with the header pipe 3.

p0040Various gaskets ensure perfect sealing of the assembly, as shown in the drawing without the need of further explanation. Apart from the central trigger mechanism, the valve of<figref idrefs="f0004">4</figref> is quite similar to that of <figref idrefs="f0002">figures 2</figref> and <figref idrefs="f0003">3</figref>, Its purpose is identical in all cases.