WO2014045218A1

WO2014045218A1 - A pressure regulator device for fuel plants in internal combustion engines, particularly for the automotive field

Info

Publication number: WO2014045218A1
Application number: PCT/IB2013/058665
Authority: WO
Inventors: Silvio TARTARI; Luca Sartorello; Marco BUZZONI; Francesco CAPPELLOZZA; Mauro BOTTARI
Original assignee: Omvl S.P.A.
Priority date: 2012-09-20
Filing date: 2013-09-19
Publication date: 2014-03-27
Also published as: CN104685437A; CN104685437B; RU2659119C2; ITPD20120274A1; RU2015106846A; EP2898388A1

Abstract

A pressure regulator device (10) for fuel gas plants in internal combustion engines, particularly for the automotive field, is described, the device being interposed between a tank for the gas at high pressure and a line (4) for sending the gas to the engine. The device comprises at least a first stage (1) for gas pressure reduction, bearing respective gas inlet (la) and outlet (lb) openings, the inlet opening (la) being in fluid communication with the gas tank, the pressure of the gas regulated by the first stage (2) being of an intermediate value between the gas pressure upstream and downstream of the device, at least a second stage (2) for gas pressure regulation, of the type comprising a regulating resilient membrane (15) placed downstream of the first stage (1), the membrane separating between them a first and a second chamber ( 16, 17) of the second stage (2), the regulated gas being supplied with the intermediate pressure into the first chamber (16) and the gas being delivered from the first chamber (16) at the preselected pressure for sending to the engine. The second stage (2) bears respective gas inlet (2a) and outlet (2b) openings, the outlet opening (2b) from the second stage (2) being in fluid communication with the line (4) for sending the gas to the engine. The device further comprises a secondary circuit associated with the device and connected in parallel with the second pressure regulation stage (2), the circuit comprising an auxiliary duct (21) designed to connect, with fluid communication, the second chamber (17) of the second stage (2) with the line (4) for sending gas to the engine, a valve unit comprising a valve seat (22) with a respective shutter member (23) and an electromagnetic actuator (24) operatively connected to the shutter member (23) in order to control the latter with respect to the valve seat (22), the actuator (24) being controlled by an electronic control unit (30) which, according to the pressure value at the outlet from the device (10) controls the opening of the shutter member (23) in order to regulate the gas pressure in the first chamber (16) of the second stage (2), so as to keep the pressure value at the outlet of the device stable.

Description

A pressure regulator device for fuel gas plants in internal combustion engines, particularly for the automotive field

Field of the invention

The present invention relates to a pressure regulator device for fuel gas (for instance, methane) plants in internal combustion engines, particularly for the automotive field, having the features set out in the preamble of main claim 1.

Technological background

It has long been known to install conversion plants in automotive vehicles which are able to supply their engines also with gas, thus providing, overall, a mixed supply or a supply with a single fuel gas. Plants of this type are generally formed by a high-pressure gas tank, a pressure reducer/regulator which brings the gas to the appropriate pressure for supply to the engine, and a series of ducts and relative accessories to facilitate charging of the tank and to ensure the optimum operation of the plant as a whole.

As is known to persons skilled in the art, the pressure regulator is a key component of a plant for engines supplied with fuel gases. The pressure regulator has to ensure that the fuel gas is supplied in the required quantity and at the required pressure. It must in particular keep the output pressure constant:

in response to both gradual pressure variations in the input pressure and sudden variations;

during the service life of the regulator itself;

in response to variations of the gas flows required by the engine;

in response to slow or sudden variations in the ambient temperature or the temperature of the heating circuit of the pressure regulator/reducer device.

The pressure regulator must also ensure that the supply is sensitive to and responds swiftly to the engine requirements. The sensitivity and precision of a pressure regulator are essential for the correct operation of the supply plant of an injection engine, as the fuel must be accurately metered to the engine.

Pressure regulators with a resilient membrane having a one-stage, two- stage or three-stage pressure reduction are known. These regulators comprise a first stage which comprises a first chamber communicating with the fuel tank by means of a first valve, part of the inner surface of the first chamber being formed by a first resilient membrane. Like the first stage, the subsequent stages also comprise a chamber, part of whose inner surface is formed by a resilient membrane.

It is difficult for regulators designed in this way to guarantee an output pressure which is stable over time; the main reasons for this are:

- the resilient membrane is affected by temperature variations and temperature increases cause reductions of the output pressure;

- input pressure variations affect the output pressure, especially in the case of a one-stage pressure reducer;

- the pressure regulation is affected by the differences in gas flow required by the engine, especially when high rates of flow are required;

- the membrane deteriorates over time, losing its properties of strength and resilience that initially ensure correct pressure regulation.

A further drawback of conventional regulators with resilient membranes is that, from the point of view of strength and reliability, they do not perform as well in the latest generation of injection plants in which there are typically highly exacting overpressures, pulses and cut-offs which a conventional regulator with a membrane is unable swiftly to compensate. Various solutions have been used in the past to resolve the above- mentioned problems of stabilising pressure in the various operating conditions.

Pressure variations due to temperature variations have in particular been resolved either by correcting injection times through control by the electronic control unit, or by reducing the temperature variation range by using a thermostat, or by using different regulation technologies, for instance the piston technology in which the function of the membrane is replaced by a moving piston of metal material.

Output pressure variations due to variations in the input pressure have been partly resolved by dividing the pressure reduction into a plurality of stages; the more stages there are, the more independent the input pressure value is, but, as will be appreciated, the bulk, connections and cost of the regulator increase accordingly. As an alternative, this problem has been resolved by an appropriate system of compensation which prevents any variation of the output pressure if the input pressure varies.

The decline of the output pressure from the required pressure as a result of the ageing of the membrane has been resolved by replacing the membrane. The extreme fluid-dynamic conditions to which the membrane is subject limit its life and performance over time, making it necessary to replace it after a predetermined number of kilometres of the vehicle and/or requiring a manual recalibration of the regulation pressure, both of which operations entail a cost for the user of the system. As an alternative, piston regulators, which do not require the replacement of parts, have been developed.

These piston pressure regulators do, as mentioned above, resolve some of the typical problems of conventional membrane regulators, but have worse performance characteristics in other respects. Response times to engine requirements are in particular longer with a worse dynamic response and higher instantaneous fluctuations which are not absorbed by the membrane. The economic aspect is just as significant as a piston regulator costs more and requires more complex production technologies.

The other solutions listed require the acquisition of a plurality of data and the electronic processing of these signals substantially increases the complexity of the software and hardware of the supply system. The known actuators used are affected by high pressure variations and are therefore necessarily more complex in constructional terms which is reflected in the cost of the device.

Lastly, in recent years, electronic pressure regulators have been developed whose feature is that they vary the pressure supplied to the injectors as a function of predetermined data such as the engine parameters, in order to widen the range of fuel flows and improve the stability of the output pressure. The main drawback of these regulators is that they require numerous data and a control algorithm which processes them and supplies the regulator with the correct signal to ensure that the output pressure is the desired pressure. In this case as well, the software and hardware are very complex with the direct consequence that costs are increased and installation times and problems are increased. The variables required for the operation of the regulator are also greater, as are the possible causes of its failure to operate.

Description of the invention

The object of the present invention is to provide a pressure regulator able to resolve the above-mentioned problems without giving up the advantages of the membrane technology and the simplicity in terms of components and installation of conventional regulators, thereby also ensuring that costs are kept down.

The objects of the present invention are in particular to:

- ensure a stable output pressure in response to variations of the external ambient temperature;

- ensure a stable output pressure in response to variations of the input pressure;

- ensure a stable output pressure in response to variations in the required flow;

- ensure a stable output pressure over the life of the regulator;

retain the membrane technology, and therefore the advantages that it provides, avoiding costly maintenance operations;

provide an economic device which can be readily installed;

provide a device which is simple to use and does not require the acquisition of numerous data for its operation, thus reducing the possible causes of its failure to operate.

These objects are achieved by a pressure regulator device embodied in accordance with the appended claims.

Brief description of the drawings

The invention will be described in further detail in the following description of a preferred embodiment thereof, illustrated by way of non-limiting example, with reference to the appended drawings, in which :

Fig. 1 shows an overall diagram of the pressure regulator device of the invention;

Fig. 2 is a view, on an enlarged scale and partly in cross-section, of a detail of the diagram of Fig. 1. Preferred embodiment of the invention

With reference to the appended drawings, a pressure regulator device for automotive plants with an engine supplied by a fuel gas, embodied in accordance with the invention, is shown overall by 10. The device is intended to be placed between a tank for the gas (for instance methane) at high pressure and the engine, neither of which are shown.

The device comprises a first pressure reduction stage 1 in fluid communication via a line 3 with the tank of pressurised fuel gas; in the tank, the gas is at the pressure Pin.

Inlet and outlet openings in the first stage 1 are shown by la and lb respectively.

Downstream of the first stage 1, the device comprises a second pressure regulation stage 2 with respective inlet and outlet openings 2a, 2b.

The inlet opening 2a is in fluid communication with the outlet lb of the first reduction stage and the outlet 2b is in fluid communication with the user device, i.e. with a delivery line 4.

The two regulation stages 1, 2 may be housed in the same body or as an alternative in two separate bodies of the device.

At the inlet opening la of the first reduction stage 1, a valve seat 5 is provided with a respective shutter 6 slidably guided to and from the seat. This shutter may for instance slide along or parallel to the main axis of the first regulation stage 1. The shutter member 6 is operatively connected to a resilient pressure-regulating membrane 7, housed in a respective seat (shown diagrammatically and bearing the reference numeral lc) in the body of the first reduction stage 1. In an embodiment, the regulation membrane 7 may also move along or parallel to the main axis of the first regulation stage 1. In a preferred embodiment, the shutter member 6 and the regulation membrane 7 are in particular coaxial with one another. In an embodiment, the shutter member 6 and the regulation membrane 7 are mechanically connected by a connection pin or rod 8. In accordance with the above-mentioned structure, a movement of the resilient membrane 7 towards the shutter member 6 causes the shutter member 6 to move away from the corresponding seat 5 and thus to open the inlet passage la.

The regulation membrane 7 divides the inner volume of the first stage 1 into a front chamber 11 and a rear chamber 12, the inlet and outlet openings la, lb being provided in the front chamber.

An opposing spring 13, designed to urge the membrane 7 in the direction of the shutter member 6, is housed in the rear chamber 12. The opposing spring 13 is calibrated as a function of the desired output pressure of the first stage (for instance 4 bar in a preferred embodiment).

The front chamber 11 is also the "compensation chamber" as it is the chamber in which the gas acts on the membrane 7 so that the latter is in equilibrium with the opposing spring 13 at the desired output pressure of the gas (shown by Pout). This front chamber 11 communicates, via the outlet lb, with an outlet duct 14 for the gas from the first stage 1. The output pressure of the gas from the first stage 1 is the regulated pressure PI of the gas in the chamber 11, for instance 4 bar.

The rear chamber 12 is separated from the front chamber 11 by means of the resilient membrane 7 which also ensures leak-tightness between the two chambers 11, 12. The rear chamber 12 may be in fluid communication with atmosphere, and as a result the air that it contains is at atmospheric pressure, or may be in fluid communication with the engine intake manifold (not shown), and as a result the air that it contains is at the pressure of said intake manifold.

Like the first stage 1, the second regulation stage 2 is also provided in a body 2c (shown only diagrammatically), whose inner volume is divided by a resilient membrane 15 which defines a first (front) chamber 16 and a second (rear) chamber 17. The inlet and outlet openings 2a, 2b are provided in the first chamber 16.

The inlet 2a of the second regulation stage 2 is in direct fluid communication with the outlet lb of the first stage 1 and with the chamber 16 of the second stage 2, without the interposition of interception members.

The regulation membrane 15 is operatively connected to a shutter member 18 designed to intercept the outlet opening 2b of the second regulation stage 2. A seat 19 engaged by the shutter 18 is provided at the outlet 2b, the shutter being slidably guided to and from the seat. This shutter member 18 may for instance slide along or parallel to the main axis of the second regulation stage 2.

The regulation membrane 15 may move along or parallel to the main axis of the body of the second regulation stage 2 and is connected to the shutter member 18 such that its movement towards the shutter member causes the latter to be urged against its own seat 19 and therefore to close the outlet passage 2b.

The second chamber 17 houses an opposing spring 20 which tends to urge the membrane 15 into the forward position, i.e. towards the shutter member 18. This opposing spring 13 is calibrated as a function of the pressure difference desired to enable the opening of the valve seat 19 connected to the membrane 15.

The first front chamber 17 is also the "compensation chamber" as it is the chamber in which the gas acts on the membrane 15 so that the latter is in equilibrium with the opposing spring 13 and with the pressure in the second chamber, shown by P3, at the desired output pressure of the gas Pout.

In accordance with a main feature of the invention, the device 10 comprises a secondary circuit (servo-assisting the main circuit of the regulation stages) connected in parallel to the second regulation stage 2, as will be described in further detail below.

The secondary circuit in particular comprises an auxiliary duct 21 for connecting, with fluid communication, the rear second chamber 17 of the second stage 2 with the line 4 for sending the gas to the engine, and a valve unit disposed on the duct 21. The valve unit comprises a valve seat 22 with a respective shutter 23 and an electromagnetic actuator 24 associated with the shutter for controlling the latter relative to the valve seat 22.

With reference to Fig. 2, the electromagnetic actuator 24 is structured such that it has an inlet passage 25 communicating with the rear second chamber 17 by means of a duct section 21, and an outlet passage 26 communicating with the duct of the line 4 for sending the gas to the injector units (not shown) of the engine via the other auxiliary duct section 21.

The inlet passage 25 communicates with a chamber 27 disposed at the rear of the shutter member 23 of the electromagnetic actuator. The shutter is associated with the seat 22 in order to act on and close it. The shutter member 23 is also associated with an opposing spring 28 normally tending to urge the shutter member into the position closing the seat. Such a configuration provides an electrovalve associated with the shutter member 23 such that when the electromagnet (of the electromagnetic actuator) is not excited, the opposing spring 28 maintains the shutter member 23 in the closed position, thereby intercepting the flow of fluid from the second chamber 17.

The valve seat 22 may be opened solely by supplying the electromagnet. This causes a displacement of the shutter member 23 and thus the opening of the seat 22. When the seat 22 is opened, the fluid flows into the duct 4.

In accordance with the invention, the actuator 24 is controlled by an electronic control unit 30 which, as a function of the pressure value at the outlet from the device, controls the opening of the shutter member 23 in order to regulate the gas pressure in the second chamber 17 of the second stage 2, so as to keep the pressure value at the outlet of the device stable.

The control unit is designed to send the actuation control to the electrovalve 22-24, which control is actuated as a function of the analysis or the comparison of the pressure value Pout detected downstream of the device, for instance by a pressure transducer positioned in the injector unit, and the desired output pressure value (a preferred value is, for instance, equivalent to 2 bar). The pressure transducer detects the pressure and supplies a signal representative of the pressure detected to the control unit.

The second chamber 17 of the second stage 2 is also in fluid communication with the corresponding first chamber 16 via a through hole 31 (which passes, for instance, through the membrane 15). The hole 31 is selected to have a cross- section whose amplitude is lower than the minimum passage section in the secondary circuit in order to ensure that the system functions correctly, as will be described in greater detail below.

When the device 10 is not operative and/or the gas flow is zero, the valve seat 5 of the inlet passage la is closed as the membrane 7 is kept in its position of equilibrium by the pressure PI in the chamber 11 which is, in these circumstances, the set regulation pressure of the first stage 1 (for instance 4 bar). In these circumstances, as the chamber 11 is connected to the chamber 16, and the latter is in turn connected to the chamber 17 which is in turn connected to the chamber 27, the pressure in these chambers is the same, i.e. PI. The valve seat 19 is closed as the force of the opposing spring 20 acts on the membrane 15 which is in turn mechanically connected to the shutter member 18. The valve seat 22 is kept closed as the shutter member 23 is urged into the forward position (with respect to the seat) by the opposing spring 28 and the electrovalve 22-24 is not excited.

Therefore, when the system is actuated, the electrovalve 22-24 is excited and thus enables the opening of the shutter member 23 of the actuator 24, the opening of the duct enables the passage of the gas from the chamber 17 for use, and therefore the pressure of the gas P3 in the chamber 17 drops. As mentioned above, the area of the passage hole 31 between the two chambers 16, 17 is smaller than the minimum passage area in the secondary circuit, making it possible to create a pressure differential between the chambers 16, 17, in favour of the latter, the differential being such as to enable the seat 19 to be opened by supplying gas from the second stage 2. This pressure in practice moves the membrane 15 towards the retracted position until reaching an equilibrium with the force of the spring 20 and a pressure in the (rear) second chamber 17 appropriately regulated to supply the desired pressure as output. In this condition of equilibrium, the membrane 15 is in an intermediate position; as a result the shutter member 18 also moves towards the retracted position with respect to its seat 19, opening the seat.

The gas flows through the duct 4 at the regulated pressure P2 (2 bar) to the injector unit.

Similarly, during the operation of the system, the equilibrium between the forces at play on the membrane 15 guarantees the desired pressure P2 as output. In particular, the force acting to the rear of the membrane 15 (i.e. on the surface of the membrane facing the chamber 17) is generated by the pressure P3 as well as by the spring 20. This pressure P3 is controlled by the actuator 24 which is in turn controlled by the control unit as a function of the pressure signal Pout; this pressure P3 is varied in order to keep the output pressure at the desired value.

This kinematic arrangement of the moving members makes it possible to locate the correct relative positioning between the shutter member 18 and the relative sealing valve seat 19, thus ensuring the flow of gas at constant pressure needed to supply the engine throughout its operating range.

For instance, a drop in the pressure Pout, to 1.5 bar, with respect to the desired value of 2 bar is read by the electronic control unit which controls the actuator 24 by prolonging the opening of the shutter member 23 in order to lower the pressure P3 which entails a larger opening of the passage through the seat 19 in order to increase the pressure Pout and keep it at the desired value of 2 bar. The control and compensation of the pressure are therefore carried out directly on the basis of the pressure signal Pout alone; this means that if, for any of the reasons listed above (ageing of the membrane, temperature increase, etc.) the pressure Pout were to vary, i.e. to rise or to drop, it is immediately compensated, providing optimum stability of the regulation system in all working conditions.

In particular, if the pressure of the gas in the outlet passage is lower than a predetermined value, the membrane of the second stage is urged against the resilient means 20, following a pressure drop in the second chamber 17, and the shutter member 18 therefore opens the passage at the outlet 2b.

It will also be appreciated that if the pressure difference between P2 and P3 is very low during operation, that means that the flow of gas between the chamber

17 and the line 4 is very low. The task of the secondary circuit and the actuator 24 is not in practice to ensure a certain rate of flow, as is the case in known electronic pressure regulator devices, but to vary the pressure P3, making it possible to obtain a circuit and an actuator 24 of small dimensions and simpler construction which is therefore cheaper and more reliable.

Stress should also be placed on the advantage that, in the device designed in this way, there is no need for an input electrovalve disposed in the high pressure duct, as the electrovalve 22-24 of the actuator stands in for its function, i.e. when it is kept shut, the pressures at play are such that both the shutter members 6 and

18 are kept in the closed position.

The device is thus able to keep the desired output gas pressure, for instance 2 bar, stable. In a further embodiment, the electronic control unit processes, in addition to the pressure signal Pout, other characteristic data, such as one or more of the following parameters: speed of rotation of the engine, opening times of the gas injectors provided in the engine, combustion air flow, engine torque requirement. As a function of these data, a control may be supplied to the actuator 24 in order to vary the pressure Pout to another desired value, for instance 3 bar, and keep it stable.

This second desired value may have the value of the pressure PI regulated by the first stage as a maximum value.

It will also be appreciated that the control unit 30 may advantageously be provided with means for controlling the actuator 24 in order to vary the outlet pressure from the device 10 to a preselected number of desired values, i.e. according to a predefined function or curve.

Moreover, in a further embodiment, the actuator 24 is controlled by means of a variable electric current adjusted by electronic control. In this case, the pressure output from the device may for instance be proportional to the mean current.

The invention therefore achieves the objects as defined and provides the advantages discussed above with respect to known solutions.

Claims

1. A pressure regulator device (10) for fuel gas plants in internal combustion engines, particularly for the automotive field, the device being placed between a tank of the gas at high pressure and a line (4) for sending the gas to the engine, the device comprising :

- at least a first stage (1) for gas pressure reduction, bearing respective gas inlet (la) and outlet (lb) openings, the inlet opening (la) being in fluid communication with the gas tank, the pressure of the gas regulated by the at least first stage (1) being of an intermediate value between the gas pressure upstream and downstream of the device,

- at least a second stage (2) for gas pressure regulation, of the type comprising a regulating resilient membrane (15) placed downstream of the at least first stage (1), the membrane separating between them a first and a second chamber (16, 17) of the at least second stage (2), the regulated gas being supplied with the intermediate pressure into the first chamber (16) and the gas being delivered from the first chamber (16) at the preselected pressure for sending to the engine, the at least second stage (2) bearing respective gas inlet (2a) and outlet (2b) openings, the outlet opening (2b) from the at least second stage (2) being in fluid communication with the line (4) for sending the gas to the engine,

characterized in that it comprises a secondary circuit associated with the device and connected in parallel with the at least second stage (2) for pressure regulation, the circuit comprising :

an auxiliary duct (21) for connecting, with fluid communication, the second chamber (17) of the at least second stage (2) with the line (4) for sending the gas to the engine, a valve unit arranged on the auxiliary duct (21), the valve unit comprising a valve seat (22) with a respective shutter member (23) and an electromagnetic actuator (24) operatively associated with the shutter member (23) for controlling the latter relative to the valve seat (22), - the actuator (24) being controlled by an electronic control unit (30) which, according to the pressure value at the outlet from the device (10), controls the opening of the shutter member (23) in order to regulate the gas pressure in the first chamber (16) of the at least second stage (2), so as to keep the pressure value at the outlet of the device stable.

2. A device according to claim 1, wherein the at least first reduction stage (1) is of the resilient membrane type.

3. A device according to claim 1, wherein the at least first reduction stage (1) is of the piston type.

4. A device according to one of the preceding claims, comprising a resilient means (28) associated with the shutter member (23) in order to urge the latter to close the valve seat (22) against the action of an electromagnet of the actuator (24), which electromagnet is provided for the opening of the valve seat (22).

5. A device according to one of the preceding claims, wherein there is provided a passage (31) for communication between the first and the second chamber (16, 17) of the at least second regulation stage (2).

6. A device according to claim 5, wherein the passage (31) is provided in the membrane (15) separating the first and second chamber (16, 17) of the at least second stage (2).

7. A device according to either claim 5 or claim 6, wherein the passage (31) has a cross-section of width less than the minimum passage cross-section provided in the secondary circuit.

8. A device according to one of the preceding claims, wherein there are provided in the control unit (30) means for controlling the actuator (24) in order to vary the outlet pressure from the device (10) to a preselected number of desired values, i.e. according to a predefined function or curve.

9. A device according to one of the preceding claims, wherein there are provided in the control unit (30) means for controlling the actuator (24) as a function of one or more of the following parameters:

- gas pressure at outlet,

- engine rotation speed,

opening time of fuel gas injectors provided in the engine,

- combustion air capacity,

- torque demand at the engine.

10. A device according to one of the preceding claims, wherein the actuator (24) is controlled by means of a variable electric current adjusted by electronic control.

11. A device according to one of the preceding claims, wherein the regulating membrane (15) is operatively connected to a shutter member (18) able to be engaged on a valve seat (19) provided at the outlet opening (2b) from the second stage, such that the pressure is adjusted, by the action of the membrane (15) on the shutter member (18), from the intermediate value at the inlet of the second stage to the value of the pressure at the outlet from the device.

12. A device according to one of the preceding claims, wherein, at the inlet opening (la) at the first reduction stage, a valve seat (5) is provided with a respective shutter member (6) slidably guided to and from the seat.

13. A device according to claim 12, wherein the shutter member (6) is operatively connected to an resilient pressure-regulating membrane (7), housed in a respective seat made in the body of the first reduction stage (1).

14. A device according to one of the preceding claims, wherein a pressure transducer is provided, able to measure the pressure (Pout) downstream of the device and transmit to the control unit (30) a signal representing the pressure (Pout).