Pressure regulator assembly for a system for supplying gaseous fuel to an internal combustion engine

Abstract

A pressure regulator assembly (5) for a system (1) for supplying gaseous fuel to an internal combustion engine (2), comprising a first pressure reducer (7) adapted to be connected to a fuel tank (3) and a second pressure reducer (8) driven by an electric actuator (42), and having an inlet port (38) connected to an outlet port (27) of the first pressure reducer (7) and an outlet chamber (39) for guiding the decompressed gaseous fuel to the engine (2); an intercepting member (22) of the first pressure reducer (7) is moved by a piston (25), which separates the outlet port (27) of the first pressure reducer (7) from an intermediate chamber (28), which accommodates a mechanical spring (29) for pushing the piston (25) and is pressurized at a pressure value equal to the pressure value of the outlet chamber (39) of the second pressure reducer (8).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian Patent Application No. 102019000025390, filed on December 23, 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a pressure regulator assembly for a system for supplying gaseous fuel to an internal combustion engine. Background Art

[0004] As is well known, a system for supplying gaseous fuel (for example, LPG gas or methane) to an internal combustion engine comprises a high-pressure gas tank, a plurality of injectors, a pressure regulator assembly interposed between the gas tank and the injectors for varying the pressure of the gas directed to the injectors, and an electronic command and control unit for controlling the flow of gas to the injectors in response to changes in the operating conditions of the engine itself.

[0005] Therefore, the sensitivity and precision of the pressure regulator assembly are crucial for the correct operation of the supply system, regardless of the engine's operating conditions and in order to always be able to ensure the high performance level of the engine itself.

[0006] Various types of pressure regulator assemblies are currently known. One type is a so-called two-stage electromechanical regulator assembly, which includes a first control stage defined by a mechanical pressure reducer and a second pressure reduction stage defined by a solenoid valve controlled by an electronic control unit in the direction of gaseous fuel flow. The solenoid valve controlled by the control unit regulates the flow rate of fuel delivered to the injector.

[0007] The mechanical pressure reducer comprises a shut-off valve for the gaseous fuel at the inlet, which is commanded to open by the action of a spring of suitable dimensions, on which the action of the gases leaving the same mechanical pressure reducer is exerted.

[0008] Even if known regulator assemblies of the above-mentioned type are commonly used, they do not make it possible to regulate the outlet pressure, ie the flow rate of the gaseous fuel to the engine, in a simple and especially precise manner, especially in the presence of sudden changes in the speed of the same engine.

[0009] The aforementioned situation is essentially due to the reasons of the implementation characteristics and therefore due to the reasons of the operation of the mechanical pressure reducer. In fact, a mechanical spring is provided in the pressure reducer, which exerts such a force on the opening that it causes the pressure value of the fuel leaving the pressure reducer to be almost constant.

[0010] Known mechanical springs tend to have high inertia, which reduces the response time of the entire regulator assembly.

[0011] Finally, since the outlet of the mechanical pressure reducer is in direct communication with the inlet of the solenoid valve, the gaseous fuel exerts an opening thrust on the solenoid valve, which is counteracted by the action of the mechanical spring of the same solenoid valve, which operates when closed. Specifically, it is precisely the high pressure at the inlet to the solenoid valve that makes precise control of the same solenoid valve to a defined flow rate complex and relatively difficult, furthermore requiring the spring to exert a high thrust that counteracts the opening action exerted by the fuel at the inlet to the solenoid valve. Summary of the Invention

[0012] The object of the present invention is to provide a pressure regulator assembly which is extremely simple from a constructional point of view, has limited burden and weight, and is easy to control.

[0013] In particular, the object of the present invention is to provide a pressure regulator assembly which is capable of precisely varying the fuel flow rate within a wide flow rate range without varying the burden and cost, or without varying the flow rate with limiting costs and burden, when compared to known regulator assemblies.

[0014] According to the present invention, a pressure regulator assembly for a system for supplying gaseous fuel to an internal combustion engine is provided; the regulator assembly comprises a first pressure reducer adapted to receive the gaseous fuel at an inlet and a second pressure reducer arranged in series with the first pressure reducer and comprising an electric actuator and a mechanical return spring for regulating the pressure / flow rate of the gaseous fuel supplied to the engine; the first pressure reducer comprises:

[0015] - fuel inlet chamber;

[0016] - fuel outlet chamber;

[0017] - an intermediate chamber arranged between the inlet chamber and the outlet chamber;

[0018] - a partition member interposed in a fluid-tight manner between the intermediate chamber and the outlet chamber;

[0019] - a communication passage from the inlet chamber to the outlet chamber;

[0020] - an intercepting body integrally connected to the partition member and configured to intercept fuel transported along the communication passage; and

[0021] a mechanical opening spring housed in the intermediate chamber and urging the partition member towards the outlet chamber;

[0022] The second pressure reducer includes an inlet conduit in communication with the outlet chamber of the first pressure reducer;

[0023] - an outlet chamber for the gaseous fuel directed towards the engine; and

[0024] - a valve body inserted between the inlet duct and the outlet chamber and driven by the electric actuator and by the return spring, characterized in that the intermediate chamber is a sealed chamber and it also includes a communication duct between the intermediate chamber and the outlet chamber of the second pressure reducer.

[0025] Furthermore, the invention relates to a method for supplying gaseous fuel to an internal combustion engine.

[0026] According to the present invention, a method of supplying gaseous fuel to an internal combustion engine is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will now be described with reference to the accompanying drawings showing non-limiting implementation examples, in which:

[0028] Figure 1 An internal combustion engine supplied by a supply system equipped with a pressure regulator assembly according to the present disclosure is shown schematically and essentially in blocks;

[0029] Figure 2 Shown in cross-section and to an exaggerated scale Figure 1 pressure regulator;

[0030] Figure 3 Schematically and essentially shown in blocks Figure 2 Details;

[0031] Figure 4 is similar to Figure 3 The graph shows Figure 3 variations in the details of

[0032] Figure 5 A diagram showing a conventional pressure regulator and a pressure regulator according to the present invention. Figure 3 and Figure 4 The operation of two different pressure regulators is shown in FIG. DETAILED DESCRIPTION

[0033] exist Figure 1 1 , numeral 1 denotes as a whole a system for supplying a gaseous fuel (such as LPG or methane) to an internal combustion engine 2 of a vehicle, not shown.

[0034] The system 1 comprises a tank 3 containing fuel to be supplied to the engine 2 , an injector assembly 4 which is known per se and will not be described in detail, and a fuel pressure regulator assembly 5 interposed between the tank 3 and the injector assembly 4 .

[0035] Furthermore, the system 1 comprises an electronic control unit 6 , also known per se and not described in detail, which is electrically connected to the injector assembly 4 and to the regulator assembly 5 to supply the engine 2 with a predetermined flow rate of fuel based on the operating conditions of the engine 2 itself.

[0036] Reference again Figure 1 , especially reference Figure 2 , the regulator assembly 5 comprises, in succession, in the direction of forward flow of fuel from the tank 3 towards the engine 2, a pressure reducer 7 with mechanical and pneumatic actuation and an electric pressure reducer 8, the latter being electrically commanded and controlled by the control unit 6 and consisting of a servo valve, advantageously a proportional valve.

[0037] refer to Figure 2 The regulator assembly 5 comprises a base body 10 accommodating a fuel heating device, known per se and shown schematically, and a hollow body 12 coupled to the base body 10 in a fluid-tight manner.

[0038] The hollow body 12 extends from the base body 10 and delimits, together with the base body 10 itself, two recesses 13 and 14 which are open on one side and are connected to each other on the other side by a connecting duct 15 extending in the base body 10 (see Figure 2 ) connected.

[0039] The hollow body 10 comprises a part 16 which delimits the recess 13 and which in fact defines the outer housing of the pressure reducer 7 (see Figure 2 ) and a component 18 that delimits the recess 14 and defines the outer housing of the pressure reducer 8.

[0040] The pressure reducer 7 comprises a closing body 19 for closing the fluid-tight recess 13 and a hollow rod 19A extending coaxially with the axis 20 in the recess 13 (see FIG. Figure 2 ).

[0041] The rod 19A in turn comprises an intermediate part 21 coupled to the part 16 in an axially sliding and fluid-tight manner, an end part adapted to bear against a non-metallic support 23 and an opposite end part 24 permanently connected to a plunger 25 .

[0042] The body 23 is coupled to the closing body 19 in a fluid-tight manner and defines, together with the closing body 19 itself, a chamber 26 communicating with the outside. Furthermore, the body 23 defines, together with the sealing body 23A traversed by the rod 19A, a fuel inlet chamber 13A which is connected to the fuel inlet chamber by means of a pipe H ( Figure 1 and Figure 2 ) is connected to tank 3 and isolated from chamber 26.

[0043] Reference again Figure 2 , the plunger 25 delimits, together with the body 10 and the member 16, an outlet chamber 27 in which the conduit 15 emerges ( Figure 2 ).

[0044] Reference again Figure 2, the plunger 25 then delimits, together with the part 16 , an intermediate sealed chamber 28 . The intermediate chamber 28 houses a helical spring 29 which presses against a surface 25A of the piston 25 on one side and against a shoulder P of the part 16 on the other side.

[0045] refer to Figure 2 , and especially with reference to Figure 3 , the surface 25B of the piston 2 opposite the contact surface 25A of the spring 29 and delimiting the chamber 27 has an extension greater than the extension of the surface 25A itself.

[0046] exist Figure 4 In the variant shown in FIG, the piston 25 comprises two circular flanges 32 and 33 axially remote from one another along the axis 20 and both commonly connected to the rod 19A.

[0047] The flange 32 is coupled to the component 16 in a fluid-tight manner, delimits the outlet chamber 27 , and has an outer diameter D1 that is smaller than the outer diameter D2 of the flange 33 .

[0048] The flange 33 is coupled to the fluid-tight component 16 and subdivides the intermediate chamber 28 into two chambers 34 and 35 , wherein the chamber 35 is a sealed chamber accommodating the spring 29 and the chamber 34 is a chamber communicating with the outside and therefore at ambient pressure.

[0049] Reference again Figure 2 The reducer 8 further comprises an end piece 36 which is inserted in a fluid-tight manner in the component 18 and is traversed by a conduit 38 which communicates on one side with the conduit 15 (cf. Figure 2 ), and is connected to the annular outlet chamber 39 on the other side.

[0050] The outlet chamber 39 is formed between the tubular member 18 and the end member 36 and communicates with the inlet of the injector assembly 4 through the conduit K to supply the decompressed gaseous fuel ( Figure 1 ).

[0051] Inside the chamber 39, the pressure reducer 8 comprises a movable valve body 40 known per se for adjusting the passage section of the duct 38. The movable valve body 40 is permanently connected to a movable body 41 of an electric actuator 42 of the pressure reducer 8 and is pushed by the action of a coil spring 43 and closes the duct 38.

[0052] The electric actuator 42 is known per se and will not be described in detail, and it moves the movable shutter body 40 along an axis 44 which is advantageously, but not necessarily, parallel to the axis 20 under the control of the electronic control unit 6 .

[0053] Reference again Figure 2, the outlet chamber 39 of the reducer 8 is placed in fluid communication by means of a duct 45 which emerges on one side in the chamber 39 and on the other side in the chamber 28 or 35 housing the spring 29 ( Figure 4 ).

[0054] From what has just been said, it seems obvious that, thanks to the presence of the duct 45, the same pressure value is present in the chambers 39, 28 or 35, namely the pressure P2 present in the outlet chamber 39 of the reducer 8. It can therefore be seen that during operation, both the force of the spring 29 and the force of the pneumatic spring resulting from the action of the pressure P2 acting on the surface 25A of the piston 25 act on the piston 35. The pressure P1 at the outlet from the reducer 7 will therefore be the sum of the "mechanical" component generated by the spring 29 and the "pneumatic" component generated by the pressure P2.

[0055] It is therefore evident from the above that the pressure reducer 7 is “servo- and closed-loop-controlled” when compared to known solutions, and in particular a pressure reducer whose outlet pressure P1 is variable not only in a continuous manner but also in a manner proportional to the pressure P2 of the fuel sent and guided to the injector assembly 4, or however variable as a function of the pressure P2 of the fuel sent and guided to the injector assembly 4.

[0056] The above content can be obtained by Figure 5 The operating diagram shown in FIG is directly derived, where line A represents the constant trend of the outlet pressure P1 for a conventional pressure regulator having a mechanical pressure reducer with a mechanical spring when the pressure P2 changes, and line B ... Figure 3 The pressure reducer 7 shown in FIG also changes when the pressure P2 changes. Line C represents the change in the pressure P1. Figure 4 The pressure reducer 7 of the structure shown in FIG also changes the pressure P1 when the pressure P2 changes.

[0057] An examination of the trends of curves B and C immediately reveals that in both of the described embodiments of the reducer 7, the force exerted by the associated spring 29 is significantly less than that exerted by the springs used in conventional mechanical reducers. Indeed, in the reducer 7, when the pressure P2 approaches zero, the pressure P1, which is essentially the force generated solely by the mechanical component, is always less than the value of the pressure P1 of the conventional regulator. As the force of spring 29 decreases while maintaining the geometry of the rod-barrel assembly, curve B shifts downward, remaining substantially parallel to itself, as shown by curve D.

[0058] The situation in which the force exerted by the spring 29 is always at a minimum is also represented by line C, where the inclination is different when compared with curves B and D due to the fact that the surface 25B is larger than the surface 25A.

[0059] In conclusion, it is obvious that once the force of the spring 29 and / or the ratio between the surfaces 25A and 25B are determined, it is possible to construct the regulator assembly 5, or more precisely to produce its specific characteristic line in such a way that, for a higher pressure P2, with the same maximum outflow cross-section corresponding to the passage cross-section of the duct 38, it is possible to have a greater flow rate than in the case of known pressure regulators.

[0060] Controlling the pressure reducer 7 based on pressure P2 thus allows for easier control of the outlet pressure of the pressure reducer 8, whose valve 40 is specifically commanded to open by pressure P1. The electric actuator 42 generates a magnetic field that tends to open the valve 40, thus acting in the same direction as the compressive force generated by pressure P1. The spring 43, in turn, exerts an opposing force, i.e., causing it to close the valve 40.

[0061] Therefore, in the pressure regulator, when the electric pressure reducer 8 is kept closed and the outlet pressure P2 is equal to the atmospheric pressure value, the force exerted by the fuel on the valve 40 is minimal. It follows that the force required by the spring 43 to keep the valve 40 in the sealed state will also be minimal when compared with known solutions, and its dimensions can therefore be determined accordingly.

[0062] Therefore, when it is necessary to provide low flow rates, and in this case, usually when operating at relatively low P2 pressure values ​​(see Figure 5 ), it is possible to implement metering in an extremely more precise manner, since the effort required to move the valve 40 against the action of the spring 43 is low and the pressure P1 is low.

[0063] When a high flow rate is desired, and a high flow rate is obtained with a high P2 value (see Figure 5 ), again when compared to known solutions, it is possible to have a higher flow rate because the value of pressure P1 is higher and because pressure P1 acts on the opening of valve 40, valve 40 will move easily in the opening, thereby minimizing the contraction.

[0064] It is clear from the above that in the regulator 5 the two pressure reducers 7 and 8 are commanded and controlled solely by means of the electric actuator 42 and therefore by sending separate command and control signals.

[0065] As is evident from the foregoing, modifications and variations are foreseeable without departing from the scope of protection of the present invention. In particular, the reducers 7 and 8 may be embodied in a manner other than that described by way of example. The conduit 45 may not be formed within the body 12, but rather from a channel at least partially external to the body 12 itself.

[0066] Furthermore, in the pressure reducer 7 , the piston 25 may be replaced by a different fluid-tight partition member, for example of the type comprising a membrane, without this changing the pressure reducer 7 itself or the method of operation of the assembly 5 .

Claims

1. A pressure regulator assembly for a system for supplying gaseous fuel to an internal combustion engine; the pressure regulator assembly comprising a first pressure reducer adapted to receive the gaseous fuel at an inlet and a second pressure reducer arranged in series with the first pressure reducer, and comprising an electric actuator and a mechanical return spring for regulating the pressure / flow rate of the gaseous fuel supplied to the internal combustion engine; The first pressure reducer comprises: - fuel inlet chamber; - fuel outlet chamber; - an intermediate chamber arranged between the inlet chamber and the outlet chamber; - a partition member interposed in a fluid-tight manner between the intermediate chamber and the outlet chamber; - a communication passage from the inlet chamber to the outlet chamber; - an intercepting body integrally connected to the partition member and configured to intercept the fuel transported along the communication passage; and a mechanical opening spring housed in the intermediate chamber and urging the partition member towards the outlet chamber; the second pressure reducer including an inlet conduit in communication with the outlet chamber of the first pressure reducer; - a second outlet chamber for said gaseous fuel directed towards said internal combustion engine; and - a valve body inserted between the inlet duct and the second outlet chamber and driven by the electric actuator and by the return spring, characterized in that the intermediate chamber is a sealed chamber and it also includes a connecting duct between the intermediate chamber and the second outlet chamber of the second pressure reducer.

2. The pressure regulator assembly according to claim 1, characterized in that The partition member has a first head surface defining the intermediate chamber and a second head surface opposite to the first head surface and defining the outlet chamber; the extension of the first head surface is smaller than the extension of the second head surface.

3. The pressure regulator assembly according to claim 1, characterized in that The partition member has a first head surface defining the intermediate chamber and a second head surface opposite the first head surface and defining the outlet chamber; The extension of the first head surface is greater than the extension of the second head surface.

4. The pressure regulator assembly according to claim 3, characterized in that The partition member defines a further annular chamber arranged between the first head surface and the second head surface; the further annular chamber communicates with the outside.

5. The pressure regulator assembly according to any one of claims 1 to 4, characterized in that It comprises a single electronic command and control unit for the first and second pressure reducing stages; the control unit controls the pressure regulator assembly by sending a single command signal to the electric actuator.

6. The pressure regulator assembly according to any one of claims 1 to 4, characterized in that The second pressure reducer is a continuously controlled proportional valve.

7. The pressure regulator assembly according to any one of claims 1 to 4, characterized in that The separation member is a piston or comprises a membrane.

8. A method for supplying gaseous fuel to an internal combustion engine by using a pressure regulator assembly as described in claim 1; the method includes the steps of applying a pneumatic action on the partition member of the first pressure reducer acting in the same direction as the mechanical action applied by the mechanical opening spring, and pressurizing the intermediate chamber with a pressure equal to the pressure existing in the second outlet chamber of the second pressure reducer.

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