Abstract:
A fluid pressure regulator includes a regulation chamber arrangement in which a piston is received, in the regulation chamber arrangement, a first chamber and a second chamber being defined by opposite parts of the piston. The first chamber and the second chamber include respectively a first inlet and a second inlet for the fluid, the first inlet and the second inlet being connected to a first environment at a first pressure. The first chamber and the second chamber include respectively a first outlet and a second outlet for the fluid, the first outlet and the second outlet being connected to a second environment at a second pressure. The piston is movable in the regulation chamber arrangement in response to a variation of pressure of the fluid in the first chamber to open/close the second outlet to regulate the second pressure. The fluid pressure regulator includes a valve device to open/close the first outlet to induce the pressure variation in the first chamber.

Description:
This application is a national phase of PCT International Application No. PCT/IB2008/000035 filed Jan. 9, 2008. PCT/IB2008/000035 claims priority to IT Application No. MO2007A000004 filed Jan. 11, 2007. The entire contents of these applications are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a pressure regulator for regulating the pressure of a fluid. 
     In particular, the invention refers to a pressure regulator that can be used in a gaseous fuel supply system, such as for example, natural gas, liquefied petroleum gas, hydrogen or similar, for regulating the pressure of the gaseous fuel flowing from a pressurized gaseous fuel source to an operating device, such as for example an internal combustion engine. 
     Mechanical pressure regulators are known, comprising a body inside which a regulation chamber is obtained. 
     Inside the regulation chamber a diaphragm or a piston is positioned, which divides this regulation chamber into a first chamber or upper chamber, and a second chamber or lower chamber. 
     The first chamber is connected to an environment at a reference pressure, for example, atmospheric pressure. 
     The second chamber comprises an inlet and an outlet for the gaseous fuel connected respectively to a source of gaseous fuel and to an operating device of gaseous fuel. 
     The known mechanical regulators furthermore comprise a valve for regulating a flow of gaseous fuel between the inlet and the outlet. 
     This valve is fixed to a first side of the diaphragm/piston, facing the second chamber, and is provided with a seat positioned in the second chamber, at the fuel flow inlet, between the inlet and outlet. 
     The known mechanical regulators furthermore comprise a spring positioned in the first chamber and fixed to a second side of the diaphragm/piston, facing the first chamber and opposite the first side. 
     During use, the spring exerts an elastic force on the diaphragm/piston, which acts on the valve by positioning and maintaining the valve at a certain distance from the seat in such a manner as to define a port through which a desired flow of gaseous fuel is allowed to flow. 
     In other words, by means of the diaphragm/piston, the spring positions the valve in a determined operating position which corresponds to a desired outlet pressure from the regulator. A limit of known mechanical regulators is that the outlet pressure varies with respect to a nominal pressure value in the operating range of the regulator, i.e. the outlet pressure changes with variation of an inlet regulator pressure and a required flow rate. 
     A further limit of known mechanical regulators is that they do not allow to regulate of the above-mentioned outlet pressure during operation, i.e. they work with a constant nominal outlet pressure which depends on the above-mentioned reference pressure. 
     In fact, this outlet pressure is determined by the operating position of the valve which depends on the elastic force exerted by the spring on the valve by means of the diaphragm/piston. 
     This elastic force depends on the features of the spring, on the preload and, in particular, on the elastic constant, and therefore, cannot be modified during operation. 
     A still further limit is that known mechanical regulators need periodic calibration in order to maintain and thus preserve the original performances. 
     This is due to the diaphragm which is subject to a time drift and permanent deformations. 
     Another drawback is that these regulators cannot be used at low temperatures, in the absence of a heat exchange between the gaseous fuel and a suitable heat source. 
     This is due to the diaphragm which, because of its sensitivity to temperature, becomes rigid at low temperatures. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to improve the pressure regulators. 
     A further object is to obtain pressure regulators which enable the outlet pressure to be changed. 
     A still further object is to provide pressure regulators which can be controlled during operation. 
     A still further object is to make pressure regulators that are more reliable and precise than known regulators, without the need to carry out periodic calibrations during the useful life thereof. 
     A still further object is to provide pressure regulators having a lower sensitivity to low temperatures than known mechanical regulators. 
     According to the invention, there is provided a fluid pressure regulator comprising a regulation chamber arrangement in which a piston is received. The arrangement includes a first chamber and a second chamber defined by opposite parts of the piston, the first chamber and the second chamber comprising respectively a first inlet and a second inlet for the fluid. The first inlet and the second inlet are connected to a first environment at a first pressure, the first chamber and the second chamber comprising respectively a first outlet and a second outlet for the fluid, the first outlet and the second outlet are connected to a second environment at a second pressure, the piston being movable in the regulation chamber arrangement in response to a variation of pressure of the fluid in the first chamber to open/close the second outlet to regulate the second pressure the fluid pressure regulator includes a valve means device to open/close the first outlet to induce the pressure variation in the first chamber. 
     In one embodiment of the invention, the regulator comprises a control and management unit for controlling the valve device by means of pulse width modulation cycles. 
     This enables pressure regulators to be obtained, which allows, during operation, to regulate and change said second pressure electronically. 
     In fact, in said control and management unit a pressure set-point value is entered, representing said second pressure, this set-point value may be fixed or variable. 
     Said control and management unit then compares said second pressure measured by a pressure sensor positioned downstream of said second outlet with the pressure set-point. 
     Subsequently, in the event of a possible deviation, detected between the second outlet pressure and the pressure set-point, the control and management unit processes an electric signal which is sent to the valve device, which creates a pressure variation in the first chamber that enables the piston to be moved in order to make the second pressure equal to the pressure set-point. 
     Furthermore, the regulator according to the invention, is more reliable and precise as compared to known mechanical regulators and can also be used at low temperatures. 
     In fact, said regulator does not use the diaphragm used in known mechanical regulators, which was sensitive to temperature and time drift. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention can be better understood and carried into effect with reference to the attached drawings in which some embodiments of the invention are shown by way of non-limiting example, in which: 
         FIG. 1  is a schematic view of a pressure regulator, in a first operating configuration, inserted in a gaseous fuel supply system; 
         FIG. 2  is a schematic view of the pressure regulator of  FIG. 1  in a second operating configuration. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1  and  FIG. 2 , a gaseous fuel supply system  1  is shown, such as for example natural gas, liquefied petroleum gas, hydrogen or similar, comprising a tank  2  or cylinder, arranged for containing gaseous fuel at a desired inlet pressure PIN. 
     The tank  2  supplies the gaseous fuel at inlet pressure PIN to a pressure regulator  3  arranged for supplying gaseous fuel at an outlet pressure POUT to a fuel dosing device  6 , for example, injectors, of a gaseous fuel operating device  7 , for example, an internal combustion engine. 
     In other words, the regulator  3  is interposed between the tank  2  and the fuel dosing device  6 , receives gaseous fuel from the tank  2  at an inlet pressure PIN and supplies the gaseous fuel to the fuel dosing device  6  at a fixed or variable desired outlet pressure value, POUT. 
     The regulator  3  comprises a body  8  inside which a regulation chamber  9  is obtained. 
     The regulation chamber  9  is provided with a first chamber  10  and a second chamber  11 , the first chamber  10  being operatively positioned above the second chamber  11 . 
     The first chamber  10  and second chamber  11  comprise, respectively, a first inlet  12  and a second inlet  13  for the gaseous fuel, the first inlet  12  and second inlet  13  being connected to the tank  2  by means of a first conduit  20  and a second conduit  21 , respectively. 
     Furthermore, the first chamber  10  and second chamber  11  comprise, respectively, a first outlet  14  and a second outlet  15  ( FIG. 2 ) connected to a control chamber  16  of regulator  3  and to the fuel dosing device  6  by means of a third conduit  22  and a fourth conduit  23 , respectively. 
     The regulator  3  further comprises a fifth conduit  24  provided with a first door  36  and a second door  37  arranged for connecting fifth conduit  24  to control chamber  16  and to fourth conduit  23 , respectively. 
     The regulator  3  is further provided with a piston  18  positioned in the regulation chamber  9  so as to define the first chamber  10  and the second chamber  11 . 
     In particular, between the piston  18  and the regulation chamber  9 , a passage  100  is provided, suitably sized, arranged for allowing the flow of gaseous fuel between the first chamber  10  and the second chamber  11 . 
     The piston  18  comprises a first end surface  38  and a second end surface  39 , opposite one another and facing, respectively, the first chamber  10  and second chamber  11 , the first end surface  38  being wider than the second end surface  39 . 
     The piston  18  is movable between a first closed position C 1 , shown in  FIG. 1 , and a first open position A 1 , shown in  FIG. 2 , in which the piston  18  respectively prevents/allows the flowing of the gaseous fuel from the second chamber  11  to fuel dosing device  6  by means of the second outlet  15 . 
     In other words, the piston  18  is movable towards or away from the second outlet  15 , so as to partially or completely occlude the second outlet  15  by means of an end  19  of the piston  18 . 
     In this manner, it is possible to change the dimension of a port, not shown, defined between the end  19  and the second outlet  15 , to allow a controlled passage of gaseous fuel from second chamber  11  to fuel dosing device  6 . 
     The regulator  3  further comprises a first spring  25 , positioned in the first chamber  10  and arranged for moving the piston  18  towards the second outlet  15 . 
     The regulator  3  further comprises a solenoid valve  26  arranged for controlling a first pressure P 1  present in the first chamber  10 . 
     The solenoid valve  26  is movable between a second closed position C 2  shown in  FIG. 1 , and a second open position A 2  shown in  FIG. 2 . 
     The solenoid valve  26  is provided with a shutter  27  arranged for opening/closing the first outlet  14  of the first chamber  10 , respectively, when the solenoid valve  26  is in the second open position A 2  and in the second closed position C 2 , the shutter  27  being controlled to move away from the first outlet  14  by a solenoid  28  which comprises a coil  29  wound around a supporting element  30 . 
     Inside the coil  29  a passage  33  is obtained inside which a pin  34  fixed to the shutter  27  can slide. 
     The regulator  3  further comprises a second spring  31  resting on the pin  34  and positioned in the passage  33 . 
     In particular, the second spring  31  is arranged for positioning the solenoid valve  26  in the second closed position C 2 , i.e. to push the shutter  27  against the first outlet  14  so as to close the first outlet  14 . 
     The solenoid valve  26  is controlled by a control and management unit  4  using a pulse width modulated square wave signal, or PWM (Pulse Width Modulation) and/or a frequency modulated signal. 
     In the control and management unit  4  a pressure set-point value PSET is entered, which represents the desired outlet pressure POUT from the regulator  3 , this set-point value PSET may be fixed or variable. 
     The control and management unit  4  compares the outlet pressure POUT measured by a pressure sensor  5  positioned downstream of the second outlet  15  with the set-point pressure PSET using, for example, a proportional, integral and differential (PID) control algorithm, or a proportional and integral (PI) control algorithm. 
     Subsequently, in function of a possible deviation, detected between the outlet pressure POUT and the pressure set-point PSET, the control and management unit  4  processes an electric signal which is sent to the solenoid  28 , which suitably drives the shutter  27  in order to make the outlet pressure POUT equal to the pressure set-point PSET. 
     The operation of the regulator  3  is described below, with reference to  FIGS. 1 and 2 , in which regulator  3  is in a first configuration A and in a second configuration B, respectively. 
     In the first configuration A, the coil  29  is not energized and the solenoid valve  26  is in the second closed position C 2 , in which, owing to a pressing force exerted by the second spring  31 , the shutter  27  is kept abutted against the first outlet  14 , i.e. closes the first outlet  14 . 
     In the first configuration A, a first force FP 1  due to the first pressure P 1  present in the first chamber  10  and an elastic force FEL exerted by the first spring  25  act on first end surface  38  of the piston  18  by pushing the piston  18  towards the second outlet  15 . 
     On the other hand, in the first configuration A, a second force FP 2  due to a second pressure P 2  present in the second chamber  11  and a third force FP 3  due to the outlet pressure POUT act on the second end surface  39  of the piston  18 , the outlet pressure POUT being lesser than the input pressure PIN which is present in fourth conduit  23 , by pushing the piston  18  away from the outlet  15 . 
     In the first configuration A, the first pressure P 1  is equal to the second pressure P 2  and both are equal to the inlet pressure PIN but, since the first end surface  38  has a planar configuration and the second end surface  39  tapers toward the second outlet, the cross-sectional area of the first end surface is greater than the cross-sectional area of the second end surface  39  so that the module of the first force FP 1  will be greater than the module of the second force FP 2  and the sum of the modules of the first force FP 1  and the elastic force FEL will be greater than the sum of the modules of the second force FP 2  and the third force FP 3 , and therefore, the piston  18  is kept in the first closed position C 1 . 
     In the second configuration B, the coil  29  is energized and the solenoid valve  26  is in the second open position A 2 , in which the shutter  27  is raised with respect to the first outlet  14 . 
     In this manner, since the first outlet  14  has a first diameter dl greater than a second diameter d 2  of the first inlet  12 , there is a flow of gaseous fuel from the first chamber  10  towards the control chamber  16  and from the control chamber  16  towards the fuel dosing device  6  by means of the fifth conduit  24 . 
     This flow of gaseous fuel causes reduction of the first pressure P 1  in the first chamber  10  and consequently of the first force FP 1 . 
     When the first force FP 1  reaches such a value for which the sum of the modules of the first force FP 1  and the elastic force FEL is lesser than the sum of the modules of the second force FP 2  and the third force FP 3 , the piston  18  is moved away from the second outlet  15 , i.e. the piston  18  passes from the first closed position C 2  to the first open position A 1 , in which a controlled flow of gaseous fuel flows towards the fuel dosing device  6  from the second chamber  11  which is constantly supplied with gaseous fuel at inlet pressure PIN. 
     Subsequently, the pressure sensor  5  detects the outlet pressure POUT at the regulator outlet  3  and sends a signal to the control and management unit  4  which compares this outlet pressure POUT with the pressure set-point PSET and sends appropriate control signals to the solenoid valve  26  if the solenoid valve  26  detects a deviation between these values. 
     The regulator  3  further allows effective regulation of a minimum flow of gaseous fuel towards the fuel dosing device  6 , also in maximum pressure conditions for the above-mentioned gaseous fuel. 
     In fact, by operating the solenoid valve  26  suitably, it is possible to let a small flow of gaseous fuel flow out from the first chamber  10 , in such a manner that the variation of the first pressure P 1  in the first chamber  10  is not such as to move the piston  18 , which remains in the first closed position C 1 . 
     This small flow, controlled by the control and management unit  4 , flows from the first chamber  10  towards the fuel dosing device  6  by means of the fifth conduit  24 . 
     In other words, it is possible to provide a small flow of fluid without operating the piston  18 , i.e. by-passing the piston  18 . 
     It should be noted how the solenoid valve  26 , suitably controlled by the control and management unit  4 , enables the first pressure P 1  to be regulated and thereby regulates the start and the duration of the delivery of gaseous fuel towards the fuel dosing device  6 . 
     In order to ensure optimum operation of the regulator  3 , the first diameter d 1  must be small enough to contain the pressure forces acting on the shutter  27 . 
     In other words, the first diameter d 1  must be small enough to allow the second spring  31  to keep the solenoid valve  26  in the second closing position C 2  when the coil  29  is not energized. 
     Furthermore, the first diameter d 1  must be greater than the second diameter d 2  so that a flow rate of gaseous fuel exiting the first chamber  10  is greater than a further flow rate of gaseous fuel entering the first chamber  10 . 
     Again, a first volume defined by the first chamber  10  must be much lower, when the piston  18  is in the first closing position C 1 , than a second volume defined by the second chamber  11 . 
     This enables in a gaseous fuel inlet step, the first chamber  10  to be filled faster as compared to the second chamber  11  to avoid undesirable opening, i.e. not controlled by the solenoid valve  26 , of the piston  18 . 
     Besides, it should be noted how the regulator  3  can be inserted and used in any position in a gas pipe (not shown) between a supply device and a operating device, or can be used as a regulator for vehicles with engines supplied by fuel cell, or used for regulating the pressure of any fluid. Also it should be noted how the regulator  3  is controlled, during operation, by the control and management unit  4  which allows, in a first case to regulate and in a second case to change, the outlet pressure POUT electronically. 
     In the first case, the electronic control is able to compensate any drifts, which may occur during the life of the regulator  3 , without the need for periodic calibrations. In the second case, the electronic control is able to compensate any drifts of operating device  7  of the gaseous fuel and/or provide the outlet pressure POUT required to satisfy any evolved strategies of the operating device  7 . Furthermore, the electronic control is able to diagnose any faults of the regulator  3  as well as the operating device  7  in order to make a safety strategy.