Patent Publication Number: US-2023163327-A1

Title: Valve for fuel cell vehicle systems with secondary safety device

Description:
DESCRIPTION 
     The present invention belongs to the sector of components for fuel cell vehicle systems, designed for installation on board vehicles, such as motor vehicles, commercial vehicles, vehicles for transporting goods and people. In particular, a valve for managing the flow of gas, in particular, hydrogen, between a tank and the fuel cell group, is the subject of the present invention. 
     As known, a fuel cell vehicle system comprises a tank for storing high-pressure hydrogen, up to 350 or 700 bars, a multi-function valve (often referred to as an OTV valve), applied to the tank, a pressure reducing valve (referred to as HPR valve), downstream of the OTV valve, further secondary valves, downstream of the HPR valve, and finally the fuel cell group for producing an electric current. 
     Due to the elevated pressure of storing hydrogen in the tank, the role of the HPR valve is fundamental; in fact, if the hydrogen were supplied to the fuel cell group at elevated pressures, it would risk breaking. Therefore, it is essential to also comprise safety systems to prevent the high-pressure hydrogen from reaching the fuel cell group. 
     To this end, known HPR valves today comprise a safety device (called a PRV valve), which, on detecting a pressure greater than a threshold value at the HPR valve outlet, allow the sudden release of hydrogen. 
     It is the object of the present invention to obtain a pressure reducing valve, which further increases the level of safety. 
     Such object is achieved by a pressure reducing valve according to claim  1 . The dependent claims identify further advantageous embodiments of the invention. 
    
    
     
       The features and advantages of the pressure reducing valve according to the present invention will become apparent from the following description, given by way of a non-limiting example, according to the figures of the accompanying drawings, wherein: 
         FIG.  1    shows a diagram of a fuel cell vehicle system, comprising an HPR valve according to an embodiment of the invention; 
         FIG.  2    illustrates a sectional view of the pressure reducing valve, in a configuration of normal operation; 
         FIG.  3    represents a sectional view of the pressure reducing valve, in a configuration of activation of a secondary safety device; 
         FIG.  4    shows an enlargement of a part of the pressure reducing valve, wherein the secondary safety device is in a configuration of non-activation; and 
         FIG.  5    shows an enlargement of a part of the pressure reducing valve, wherein the secondary safety device is in a configuration of activation. 
     
    
    
     With reference to the figures of the accompanying tables, an example of a fuel cell vehicle system is globally denoted with  1 , comprising: 
     a tank  2  for storing high-pressure hydrogen, for example, up to 350 or 700 bars;   a multi-function or OTV  4  valve, applied to the tank  2  and adapted to regulate the inlet of gas to the tank when refueling and the outlet of gas when using the system, preferably, in addition to having further safety functions;   a pressure reducing valve or HPR  6  valve, arranged downstream of the OTV  4  valve, adapted to reduce the pressure from an upstream value p1, with which the gas exits the OTV  4  valve, to a downstream value p2;   preferably, further secondary valves  8 , arranged downstream of the HPR  6  value; and   a fuel cell group  10 , adapted to produce an electric current by means of transforming the hydrogen.   

     For reasons of clarity, a pressure reducing valve according to an embodiment will be described below; however, the invention is also applicable to reducing valves having a different configuration. 
     The HPR  6  valve comprises a valve body  20 , for example, made in a single piece of a metal material, typically of aluminum, a first stage unit or high-pressure stage unit  40 , arranged in the valve body  20 , and a second stage unit or low-pressure stage unit  60 , arranged in the valve body  20  downstream of the first stage unit  40 . 
     The HPR  6  valve further comprises an inlet body  22 , having an inlet  24 , applied to the valve body  20  upstream of the first stage unit  40 , and an outlet body  26 , having an outlet  28 , applied to the valve body  20  downstream of the second stage unit  60 . 
     The valve body  20  has a calibrated inlet passage  30 , a first stage piston chamber  32 , an intermediate passage  34 , a second stage piston chamber  36  and an outlet passage  38 . 
     The first stage unit  40  comprises a first stage piston  42 , elastic thrust means  44 , a front gasket  46  and a rear gasket  48 . The first stage piston  42 , cooperating with the gaskets,  46 ,  48 , is slidable sealingly housed in the first stage piston chamber  32 . 
     The first stage piston  42  is configured to act as a splitter between the inlet passage  30  and the intermediate passage  34 . 
     The second stage unit  60  comprises a second stage piston  62  , elastic thrust means  64 , a front gasket  66  and a rear gasket  68 . An internal passage  70  is made between the ends of the second stage piston  62 . The second stage piston  62 , cooperating with the gaskets,  66 ,  68 , is slidable sealingly housed in the second stage piston chamber  36 . 
     The second stage piston  62  is configured to act as a splitter between the intermediate passage  34  and the internal passage  70  or the outlet passage  38 . 
     In a configuration of normal operation of the HPR valve, the opening action made on the first stage piston  42  by the pressure of the gas present in the inlet passage  30  and by the thrust means  44  is balanced by the closing action made on the first stage piston  42  by the pressure of the gas present in a bottom compartment  54 ; in such a configuration, the first stage piston  42  splits the passage between the inlet passage  30  and the intermediate passage  34 , causing a drop in pressure. 
     Similarly, in such configuration, the opening action made on the second stage piston  62  by the pressure of the gas present in the intermediate passage  34  and by the thrust means  64  is balanced by the closing action made on the second stage piston  62  by the pressure of the gas present in the outlet passage  38 ; in such a configuration, the second stage piston  62  splits the passage between the intermediate passage  34  and the internal passage  70  or the outlet passage  38 , causing a further drop in pressure. 
     The HPR  6  valve further comprises a primary safety device  80  adapted to make a sudden exit of the gas from the outlet passage  38  when the pressure of the gas in said outlet passage  38  exceeds a predetermined threshold value. 
     For example, the outlet body  26  is provided with a safety passage  82  in communication with the outlet passage  38 , which is closed by a shutter  84  of the primary safety device  80 . Said primary safety device  80  further comprises thrust means  86  adapted to permanently act in order to keep the shutter  84  on closing of the safety passage  82 . 
     When the pressure of the gas in the outlet passage  38  exceeds the predetermined threshold value, the shutter  84  opens the safety passage  82  and the gas suddenly exits outside through said safety passage  82 , for example, by passing inside a shutter-door  88  of the primary safety device  80 , inside a spring  90  of the thrust means  86  and through a vent hole  92  made in a closing body  94  of the primary safety device  80 . 
     From the configuration of normal operation, it is possible that, for example, due to a jamming of the first stage piston or the second stage piston, the gas pressure in the outlet passage  38  increases, until it exceeds the predetermined threshold value, causing the activation of the primary safety device  80 . 
     Preferably, the primary safety device  80  is reversible, since when the gas pressure in the outlet passage  38  returns below the threshold value, the shutter  84  closes the safety passage  82  again, and the HPR valve  6  returns to normal operation, if the conditions are right. 
     Furthermore, according to the invention, there is comprised a secondary safety device  200 , mechanically independent of the first stage unit  40 , preferably acting upstream of the first stage unit  40 , to limit the passage of gas from the inlet  24  to the inlet passage  30  when the gas flow exceeds a predetermined threshold value. 
     According to an embodiment, the inlet body  22  has an upstream duct  100  with a calibrated section, in communication with the inlet  24 , a main compartment  102 , upstream of which the upstream duct  100  opens out, and a downstream duct  104 , downstream of the main compartment  102 , in communication with the inlet passage  30  of the valve body  20 . 
     The secondary safety device  200  comprises a flow shutter  202  accommodated in the main compartment  102 , which is configured to be hit by the gas flow passing from the upstream duct  100  towards the downstream duct  104  and movable beneath the action of said gas flow to limit the passage of the gas from the upstream duct  100  towards the downstream duct  104 . 
     According to a preferred embodiment, the flow shutter  202  consists of an element extending along a shutter axis X, between an upstream end  204 , facing the upstream duct  100 , and a downstream end  206 , facing the downstream duct  104 . The flow shutter  202  has an internal shutter passage  208 , between the upstream end  204 , where at least one inlet opening  204   a  opens, and the downstream end  206 , where at least one outlet opening  206   a  opens. 
     For example, the inlet opening  204   a  is arranged on a plane orthogonal to the shutter axis X, for example, coaxial to the section of the upstream duct  100  and preferably has a greater diameter than that of the section of the upstream duct  100 . 
     For example, furthermore, a plurality of outlet openings  206   a  is provided, arranged in a ring, forming radial passages between the shutter passage  208  and the downstream duct  104 . 
     Preferably, furthermore, an auxiliary opening  206   b  is present at the downstream end  206 , for example, coaxial to the inlet opening  204   a . 
     The secondary safety device  200  further comprises thrust means  210 , comprising, for example, a spring  212 , permanently acting on the flow shutter  202  to keep the gas passing from the upstream duct  100  to the downstream duct  104 . 
     For example, the thrust means  210  act to keep the upstream end  204  of the flow shutter  202  in abutment against the wall in which the upstream duct  100  opens. 
     According to a preferred embodiment, the connection between the main compartment  102  and the downstream duct  104  is made by a main aperture  214 , which, in order to limit the passage of gas towards the downstream duct,  104 , is closed by the downstream end  206  of the flow shutter  202 . 
     For example, the main aperture  214  is delimited by an abutment wall  216 , having a truncated-cone shaped abutment surface  218 , converging towards the main aperture  214 . Correspondingly, the downstream end  206  of the flow shutter  202  comprises an annular closing wall  220 , having a truncated-cone shaped closing surface  222 , converging in the closing direction. 
     According to a preferred embodiment, the secondary safety device  200  comprises a compass  224 , accommodated in the main compartment  102 , for example, screwed therein, comprising an annular guide wall  226 , having an axial extension, and a bottom wall  228 , having a radial extension, in which the main aperture  214  opens. 
     Preferably, the outer dimension of the flow shutter  202  is defined so that said shutter is translationally guided by the guide wall  226 . 
     In a rest configuration of the secondary safety device, in which the gas flow from the upstream duct  100  towards the downstream duct  104  is less than a predetermined threshold value, the main aperture  214  is not obstructed and the gas passes from the upstream duct  100  towards the downstream duct  104 . In such a configuration, the flow shutter  202  is in a limit opening position, which is such as to keep the main aperture  214  free; for example, in the limit opening position, the flow shutter  202  is in abutment against the wall in which the upstream duct  100  opens, and is kept in such a position by the action of the thrust means  210 . 
     In a configuration of activation of the secondary safety device  200 , in which the gas flow from the upstream duct  100  towards the downstream duct  104  is greater than a predetermined threshold value, the main aperture  214  is obstructed by the flow shutter  202  and the passage of gas from the upstream duct  100  towards the downstream duct  104  is lowered or stopped. In such a configuration, the action of the gas flow on the shutter has overcome the action of the thrust means  210  and the flow shutter  202  is in a limit closing position, which is such as to split or close the main aperture  214 ; for example, in the limit closing position, the flow shutter  202  is in abutment against the abutment wall  216 , in which the main aperture  214  opens. 
     However, the secondary safety device  200  is configured to act in a mechanically independent manner of the first stage unit  40 , in the sense that it is not influenced by the configuration of the latter, for example, by the position taken by the components thereof. Advantageously, this ensures the intervention of said secondary safety device  200  also when there is a jamming of the first stage unit, as well as of the second stage unit. 
     Overall, the HPR valve, equipped with the secondary safety device  200 , comprises three operating configurations: 
     a configuration of normal operation, in which the gas pressure of the second stage unit  60 , i.e. in the outlet passage  38 , is less than a threshold value and the gas flow upstream of the first stage unit  40 , i.e. passing from the upstream duct  100  to the downstream duct  104 , is less than a threshold value; in such a configuration, the primary safety device  80  is deactivated and the secondary safety device is deactivated;   a first anomaly configuration, in which the gas pressure downstream of the second stage unit  60  is greater than a threshold value and the gas flow upstream of the first stage unit  40  is less than a threshold value; in such a configuration, the primary safety device  80  is activated (the gas exits outside) and the secondary safety device is deactivated;   a second anomaly configuration, in which the gas pressure downstream of the second stage unit  60  is greater than a threshold value and the gas flow upstream of the first stage unit  40  is greater than a threshold value; in such a configuration, the primary safety device  80  is activated and the secondary safety device is activated (the flow of gas to the first stage unit is lowered or stopped).   

     Innovatively, the valve according to the present invention, equipped with secondary safety device, allows an increase in the level of reliability, since it blocks the gas flow upstream of the pressure reducer, in the case where, despite the gas exiting outside due to an overpressure, the flow of gas towards the pressure reducer continues to increase. 
     As anticipated, the pressure reducing valve described above is one example of application of the invention. 
     According to a variant, the pressure reducing valve is provided with only one pressure reducing stage and the secondary safety device is arranged upstream of said single reducing stage. 
     According to a further variant, the pressure reducing valve is devoid of a primary safety device arranged downstream of the second reducing stage or downstream of the single reducing stage, and is provided only with the secondary safety device, arranged upstream of the first reducing stage or upstream of the single reducing stage. 
     According to a further variant, the secondary safety device acts downstream of the first stage unit, but upstream of the second stage unit. 
     According to the variants described above, the pressure reducing stages are mechanical. 
     According to a further variant, at least one of the reducing stages is electronic. In other words, in such an embodiment variant, the piston, which creates the restriction causing the reduction in pressure, is activated by a proportional solenoid, to which a signal is sent which is representative of the gas pressure upstream of the piston and translationally controls said piston so as to increase or reduce the restriction, thus decreasing or increasing the gas pressure downstream of the piston, respectively. 
     Clearly, in order to satisfy contingent needs, a person skilled in the art can make changes to the reducing valve described above, all contained in the scope of protection as defined by the following claims, as well as the aforesaid variants.