EP4735751A1

EP4735751A1 - Pressure regulator

Info

Publication number: EP4735751A1
Application number: EP24745357.4A
Authority: EP
Inventors: Diego Guerrato
Original assignee: Phinia Delphi Luxembourg SARL
Current assignee: Phinia Delphi Luxembourg SARL
Priority date: 2023-06-30
Filing date: 2024-06-28
Publication date: 2026-05-06
Also published as: WO2025003483A1; GB2631447B; CN121420130A; KR20260030149A; GB202309978D0; GB2631447A

Abstract

A pressure regulator (1) for a common rail of a high pressure hydrogen injection system, the pressure regulator (1) comprising: an inlet (5) for delivering fuel into the pressure regulator (1), an outlet (10) for supplying fuel out of the pressure regulator (1) and into the common rail, a fuel path for fuel flow between the inlet (5) and the outlet (10), a valve (20) movable between a closed position, wherein the valve (20) is arranged to block the fuel path, and a plurality of open positions, wherein the valve (20) is arranged to at most partially block the fuel path, each open position corresponding to a different position of the valve (20) with respect to the fuel path, a dual-spring system (25) arranged to urge the valve (20) towards the closed position, the dual-spring system (25) comprising a first spring (35) with a first compression characteristic and a second spring (40) with a second compression characteristic different to the first compression characteristic, and a solenoid actuator (30) configured to draw the valve (20) away from the closed position against the action of the dual-spring system (25) to one of the open positions when the solenoid actuator (30) is supplied with current, wherein the pressure regulator (1) is configured such that: the valve (20) is maintained in the closed position when the solenoid actuator (30) is not supplied with current, the first spring (35) is compressed by a first distance thereby providing a first phase of movement of the valve (20), when the solenoid actuator (30) is supplied with current less than or equal to a current threshold, and the second spring (40) is compressed by a second distance thereby providing a second phase of movement of the valve (20) following the first phase of movement, when the solenoid actuator (30) is supplied with current exceeding the current threshold.

Description

PRESSURE REGULATOR

FIELD OF THE INVENTION

This invention relates to a pressure regulator for a common rail of a fuel injection system. In particular, the invention relates to a pressure regulator for regulating the pressure of a high pressure gaseous fuel such as hydrogen in the common rail of a high pressure gaseous fuel injection system.

BACKGROUND

In fuel injection systems (FISs), it is known for a fuel pump to supply fuel to a high- pressure accumulator (or common rail), from where it is delivered by means of a dedicated fuel injector into each cylinder of an engine for combustion.

Maintaining an acceptable delivery accuracy from the fuel injector is a technical challenge, particularly as the quantity of fuel to be delivered can vary across a broad range. The problem can be exacerbated by variations in common rail pressure and so it is important to maintain consistent pressures within the common rail at all times, regardless of the timing of the injector injection cycles. For this purpose, one or more pressure regulators are provided between the fuel pump and the common rail to regulate the pressure of the fuel within the common rail.

Up until now, such a pressure regulator has typically included a valve arrangeable to limit the amount of fuel passing out of the regulator and into the common rail and a solenoid actuator configured to control the position of the valve. The position of the valve (and hence the rate of flow of fuel out of the pressure regulator) is proportional to the amount of current supplied to the solenoid actuator.

One issue with these pressure regulators is that they are not capable of precisely controlling fuel pressures in the common rail both when very low fuel pressures are needed therein (i.e. , when the engine is in low demand e.g., when the engine is idling) and when much larger pressures are needed therein (i.e., when the ending is in high demand). To provide both precisely, the pressure regulator has to be able to accurately alter very low flow rates e.g., around just a few tenths of grams of fuel per second (i.e. by moving the valve in the regulator by only a few microns) as well as provide higher flow rates e.g., around tens of grams of fuel per second (i.e., by moving the valve in the regulator by thousands of microns). Maintaining acceptable delivery accuracy at both ends of these ranges is therefore difficult.

In particular, it is difficult to precisely provide very small changes of movements of the valve in the regulator to bring about precise changes in very low rates of fuel out of the pressure regulator. This is particularly difficult because the valves of such pressure regulators tend to experience stiction and friction that result in them moving (or “jumping”) much more than desired.

It is against this background that the invention has been devised to provide an improved means of regulating pressure in the common rail of a fuel injection system.

SUMMARY OF THE INVENTION

According to a first aspect, there is provided a pressure regulator for a common rail of a high pressure hydrogen injection system, the pressure regulator comprising: an inlet for delivering fuel into the pressure regulator, an outlet for supplying fuel out of the pressure regulator and into the common rail, a fuel path for fuel flow between the inlet and the outlet, a valve movable between a closed position, wherein the valve is arranged to block the fuel path, and a plurality of open positions, wherein the valve is arranged to at most partially block the fuel path, each open position corresponding to a different position of the valve with respect to the fuel path, a dual-spring system arranged to urge the valve towards the closed position, the dual-spring system comprising a first spring with a first compression characteristic and a second spring with a second compression characteristic different to the first compression characteristic, and a solenoid actuator configured to draw the valve away from the closed position against the action of the dual-spring system to one of the open positions when the solenoid actuator is supplied with current, wherein the pressure regulator is configured such that: the valve is maintained in the closed position when the solenoid actuator is not supplied with current, the first spring is compressed by a first distance thereby providing a first phase of movement of the valve, when the solenoid actuator is supplied with current less than or equal to a current threshold, and the second spring is compressed by a second distance thereby providing a second phase of movement of the valve following the first phase of movement, when the solenoid actuator is supplied with current exceeding the current threshold.

Each of the open and closed positions of the valve is associated with a different rate of flow of the fuel out of the pressure regulator. When the valve is closed, the rate of fuel flow out of the pressure regulator is zero. The more open the valve is, the more fuel flow there is out of the pressure regulator. The pressure regulator can thus be used to control the level of fuel pressure within the common rail

The invention allows for different control over the movement of the valve depending on whether the solenoid actuator is supplied with lower or higher currents. In one embodiment, the compression characteristics of the springs may be such that the pressure regulator provides more precise control of the position of the valve (i.e., slower movement of the valve) when supplied with lower currents (i.e., in open positions of the valve closer to the closed position) and less precise control of the position of the valve (i.e., less slow movement of the valve) when supplied with higher currents. This would advantageously mean that the fuel pressure in the common rail is more precisely controlled for lower pressures (i.e., when the engine is in low power mode) and less precisely controlled for higher pressures (i.e., when the engine is in high power mode).

During the first phase of movement of the valve, a second length of the second spring may remain substantially the same. In other words, the pressure regulator may be configured such that the second spring remains at substantially the same level of compression (i.e., “uncompressed”) during the first phase of movement of the valve.

Likewise, during the second phase of movement of the valve, a first length of the first spring may remain substantially the same. In other words, the pressure regulator may be configured such that the first spring (35) remains at substantially the same level of compression during the second phase of movement. Particularly, when the solenoid actuator is supplied with a current equal to the current threshold, the first spring is “fully compressed”, i.e., it can be compressed no more, and as more current is supplied to the solenoid actuator, the second spring beings to compress thereby providing the second phase movement of the valve. The second movement of the valve preferably immediately follows the first movement of the valve such that as the current increases from below, through and above the current threshold the valve continues to move in a smooth fashion and there is no period where current applied to the solenoid actuator increases and the valve stays in the same position.

The first spring may have a first stiffness and the second spring may have a second stiffness. The first stiffness is preferably larger than the second stiffness.

As a result of this, the first spring is more resistant to compression than the second spring. This means that as current supplied to the solenoid actuator is increased, the valve is moved more slowly (or “precisely”) during the first phase of movement than in the second phase of movement, and more precise control over fuel rates out of the pressure regulator at lower currents is achieved. In other words, more precise control over the movement of the valve is provided at lower currents and less precise control over the movement of the valve is provided at higher currents The first spring and the second spring may be arranged in series.

The first spring may be preloaded with a first force and the second spring may be preloaded with a second force. The first force is preferably less than the second force.

This allows for a compact arrangement of the pressure regulator. Although arranged in series, since the first spring is preloaded with less force than the second spring, only the first spring is compressed under the action of the solenoid actuator initially (i.e., during the first phase of movement). Only after the first spring is “fully compressed”, i.e., after it can be compressed no more, is the force provided by the solenoid actuator large enough to bring about compression of the second spring.

The first spring is preferably preloaded with just enough force to keep the valve in the closed position when the solenoid actuator is not energised/ supplied with current, but begins to compress straight away when the solenoid actuator is energised/ supplied with current. The solenoid actuator may comprise a movable armature coupled to the valve. The movable armature may be configured to compress the first and second springs in dependence on the current supplied to the solenoid actuator.

The armature is optionally rigidly coupled to the valve such that a movement of the armature causes a corresponding movement of the valve. The armature may be magnetic and the solenoid actuator may comprise a solenoid configured to act on the magnetic armature in dependence on the current supplied to the solenoid actuator.

The armature may be configured to compress the first spring through direct engagement with the first spring.

In a preferred embodiment, the dual-spring system comprises an intermediate element. The armature may be configured to compress the second spring through engagement with the intermediate element.

The pressure regulator may be configured such that a gap is defined between the armature and the intermediate element when the solenoid actuator is not supplied with current. The armature may be operable to compress the second spring via the intermediate element only once the armature has moved through the gap.

In this way, the armature is only operable to compress the second spring via the intermediate element after the first spring is compressed by a first amount. In particular, the width of the gap preferably corresponds to the first distance that the first spring is compressed when the solenoid is provided with a current equal to (or exceeding) the current threshold. In this way, the compression of the second spring begins immediately after the first spring is finished compressing, and hence the second movement of the valve immediately follows on from the first movement of the valve.

The pressure regulator may be configured such that the armature remains engaged with the intermediate element during the second phase of movement, thereby preferably preventing the armature from compressing the first spring during the second phase of movement. Preferably, the intermediate element includes a first annular portion defining a first recess. The first recess may enclose at least a part of the first spring.

Preferably, the intermediate element includes a second annular portion defining a second recess. The second recess may enclose at least a part of the second spring.

The armature may be annular and may define an armature recess. The armature recess may enclose at least a part of the intermediate element.

These configurations allow for a compact arrangement of the pressure regulator.

In an embodiment, the pressure regulator comprises a first adjustment means for adjusting a first preload on the first spring. Additionally or alternatively, the pressure regulator comprises a second adjustment means for adjusting a second preload on the second spring.

The first and second adjustment means allow for precise control of the first and second compression characteristics of the spring, and can usefully be used to ensure that the second movement of the valve immediately follows the first movement of the valve such that as the current increases from below, through and above the current threshold the valve continues to move in a smooth fashion and there is no situation where current applied to the solenoid actuator same position.

The invention also extends to a fuel injection system comprising the pressure regulator described above. The fuel injection system is preferably a high pressure hydrogen injection system.

Preferred and/or optional features of the pressure regulator may be incorporated alone or in appropriate combination in the fuel injection system also.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, preferred non-limiting embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional front view of a pressure regulator in accordance with one embodiment of the invention, wherein the pressure regulator comprises a valve, and wherein the valve is arranged in a closed position;

Figure 2 shows the pressure regulator of Figure 1 , wherein the valve of the pressure regulator is arranged in a first open position;

Figure 3 shows the pressure regulator of Figures 1 and 2, wherein the valve of the pressure regulator is arranged in a second open position, the valve being more open in the second open position than in the first open position;

Figure 4 shows a partial enlarged view of the pressure regulator of Figure 1 ; and

Figure 5 is a graph showing how the rate of fuel flowing out of the pressure regulator changes in dependence on the current supplied to a solenoid actuator of the pressure regulator.

In the drawings, as well as in the following description, like features are assigned like reference signs. Throughout this description, terms such as ‘upper’ and ‘lower’, and other directional references, are used with reference to the orientation of the pressure regulator as shown in the accompanying drawings. However, it will be appreciated that such references are not limiting and that pressure regulators according to the invention can be used in any orientation.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 , 2 and 3 show a pressure regulator 1 for a common rail (not shown) of a fuel injection system (not shown), in particular a high pressure hydrogen injection system.

The pressure regulator 1 comprises an inlet 5 for delivering fuel into the pressure regulator 1 , an outlet 10 for supplying fuel out of the pressure regulator 1 and into the common rail, and a fuel path for fuel flow between the inlet 5 and the outlet 10. The pressure regulator 1 further comprises a valve 20 that is movable between a closed position, wherein the valve 20 is arranged to block the fuel path (as shown in Figure 1), and a plurality of open positions, wherein the valve 20 is arranged to at most partially block the fuel path, each open position corresponding to a different position of the valve 20 with respect to the fuel path (as shown in Figures 2 and 3).

To control the movement of the valve 20, the pressure regulator 1 is provided with a dual-spring system 25 and a solenoid actuator 30. The dual-spring system 25 is arranged to urge the valve 20 into the closed position. The dual-spring system 25 comprises a first spring 35 with a first compression characteristic and a second spring 40 with a second compression characteristic different to the first compression characteristic. The solenoid actuator 30 is configured to draw the valve 20 away from the closed position against the biasing force of the dual-spring system 25 to one of the open positions, when the solenoid actuator 30 is supplied with current.

The pressure regulator 1 is configured such that:

1) the valve 20 is maintained in the closed position when the solenoid actuator 30 is not supplied with current,

2) the first spring 35 is compressed by a first amount, thereby providing a first phase of movement of the valve 20, when the solenoid actuator 30 is supplied with current less than or equal to a current threshold, and

3) the second spring 40 is compressed by a second amount, thereby providing a second phase of movement of the valve 20 following the first phase of movement, when the solenoid actuator 30 is supplied with current exceeding the current threshold.

In this way, the movement of the valve 20 is determined by the first spring 35 during the first phase of movement and by the second spring 40 during the second phase of movement, and the amount of movement of the valve 20 is determined in dependence on the amount of current provided to the solenoid actuator 30. As the current applied to the solenoid actuator 30 increases from zero, the first spring 35 undergoes compression (i.e. , its length is shortened) and the valve 20 undergoes the first phase of movement. If the current exceeds the current threshold, the second spring 40 undergoes compression (i.e., its length is shortened) and the valve 20 undergoes the second phase of movement. If the current does not exceed the current threshold, only the first spring 35 undergoes compression (i.e., its length is shortened) and the valve 20 undergoes only the first phase of movement. The second spring 40 remains at the same level of compression in this instance.

Hence, depending on the particular compression characteristics of the springs 35, 40, it is possible to have one type of movement of the valve 20 when the actuator 30 is supplied with lower currents, and another type of movement of the valve 20 when the actuator 30 is supplied with higher currents. In one particularly preferred embodiment, the compression characteristics of the springs 35, 40 may be selected such that the pressure regulator 1 provides slower movement of the valve 20 (i.e., more precise control over the position of the valve 20) when the solenoid actuator 30 is supplied with lower currents, and less slow movement of the valve 20 (i.e., less precise control of the position of the valve 20) when the solenoid actuator 30 is supplied with higher currents, as show in Figure 5. To this end, the first spring 35 provides a relatively greater resistance to the movement of the valve 20 during the first phase and the second spring 40 provides a relatively lower resistance of movement to the valve 20 in the second phase.

Such an arrangement is particularly advantageous because it means that the pressure regulator 1 is able to control the change of flow of the fuel out of the pressure regulator 1 more precisely when the currents applied to the solenoid actuator 30 are lower (i.e., in open positions of the valve 20 closer to the closed position). As such, fuel pressure in the common rail can be precisely controlled when lower pressures are needed (i.e., when there is lower demand for fuel in the engine) and also when higher pressures are needed (i.e., when there is higher demand for fuel in the engine).

More detail about the pressure regulator 1 will now be provided.

The pressure regulator 1 typically forms part of a fuel injection system (FIS) (not shown), preferably a gaseous fuel injection system, more preferably a high pressure hydrogen fuel injection system, i.e. a fuel injection system for injecting gaseous fuel in the form of high pressure hydrogen into an engine cylinder for combustion. In addition to the pressure regulator 1 , the fuel injection system may comprise a fuel pump (not shown) for pumping fuel into the inlet 5 of the pressure regulator 1 , a common rail (not shown) for receiving fuel exiting the outlet 10 of the pressure regulator 1 , and at least one fuel injector (not shown) for injecting fuel from the common rail into at least one engine cylinder (not shown) for combustion.

The pressure regulator 1 is preferably arranged between the fuel pump and the common rail, i.e. before the common rail. In this way, the pressure regulator 1 is operable to control the flow of fuel into and hence maintain pre-defined levels of fuel pressure inside the common rail, regardless of the action of the or each fuel injector.

The pressure regulator 1 - as shown in the embodiment of Figures 1 , 2 and 3 - is provided with a regulator body 45 that extends along longitudinal axis L.

The regulator body 45 comprises upper and lower housing sections 50, 55 that may be integrally formed or fixedly coupled etc. The lower section 55 comprises the inlet 5 through which fuel enters the pressure regulator 1 from the fuel pump and the outlet 10 out of which fuel exits the pressure regulator 1 into the common rail. The inlet 5 and the outlet 10 are arranged along perpendicular axes, with the inlet aligned with the axis of movement of the valve 20. The inlet 5 and outlet 10 meet at a junction region of the inlet 5 and outlet 10 which defines a valve seat 60 with which the valve 20 is co-operable to control the flow of fuel between the inlet 5 and the outlet 10.

In one embodiment, the inlet 5 takes the form of an in-channel that extends upwards along axis L towards the centre of the lower section 55 of the regulator body 45 from the base of the lower section 55. The in-channel extends vertically through the middle of the lower section 55. Meanwhile, the outlet 10 takes the form of two out-channels that extend inwards along an axis perpendicular to axis L towards the centre of the lower section 55 from opposing side walls of the lower section 55. The out-channels extend horizontally through the middle of the lower section 55

The valve 20 is configured to move up and down (along the axis L) - i.e., towards and away from the valve seat 60 - to control the amount of fuel passing between the inlet 5 and the outlet 10, and hence to control the amount of fuel exiting the pressure regulator 1. To this end, the valve 20 comprises a valve head 65 that is configured to engage with the valve seat 60 to block the fuel path, or to at most partially block the fuel path when it is moved away from the valve seat 60. The valve 20 further includes a valve pin 70 rigidly connected to the valve head 65 which is moveable with the valve head 65. The valve pin 70 includes a main stem which extends away from the valve head 65, and upwards along the axis L into the upper section 50.

The valve head 65 is shaped such that it can be arranged to completely (or substantially) block the fuel path between the inlet 5 and the outlet 10 when the valve 20 is arranged in the closed position against the valve seat 60. Preferably, the valve 20 is shaped so that it extends across both the in-channel and the out- channels when arranged in the closed position (as shown in Figure 1).

In Figures 2 and 3, the valve 20 is arranged in open positions. To this end, the valve head 65 has been moved upwards (under the pulling of the valve pin 70) along axis L. In each of these positions, the valve head 65 no longer blocks the in- channel and the out-channels, and fuel from the inlet 5 can pass through the fuel path and out the outlet 10 of the pressure regulator 1 .

The valve 20 is open to a greater extent in Figure 2 than in Figure 1 and is open to a greater extent in Figure 3 than in Figure 2. In fact, in Figure 3 the valve 20 is the most open it can be, i.e. , it is in its fully open position.

The more open the valve 20, the more fuel can pass through the pressure regulator 1 and hence the higher the flow rate of fuel out the pressure regulator 1 , and hence the higher the pressure of the fuel in the common rail (not shown). Indeed, the flow rate of fuel out of the pressure regulator 1 is substantially proportional to how open the valve 20 is. Of course, when the valve blocks the fuel path - i.e., when the valve 20 is closed, (as in Figure 1), the fuel exiting the pressure regulator 1 is substantially zero.

The upper section 50 of the regulator body 45 defines at least two separate and enclosed chambers therein, each in the form of bores defined in the upper section 50 of the body 45. The first (or centre) chamber 85 is located in the centre of the upper section 50, while the second chamber 90 is annular and extends around/ entirely surrounds the first chamber 85, i.e., about axis L. In other words, the first and second chambers 85, 90 are concentric with the first chamber 85 being arranged more inwardly than the second chamber 90/ the second chamber 90 extending all the way around the outside of the first chamber 85, i.e., in the plane perpendicular to the axis L. To define the two chambers 85, 90, the upper section of the regulator 1 extends fully around each of the chambers 85, 90 on all sides thereof.

Inside the chamber 90, a solenoid 95 is arranged. In particular, it takes the form of a coil that is looped around the annular cavity defined by the chamber 90, i.e. the coil extends all the way around the annular chamber and hence is looped around the first chamber 85 and axis L. For this reason, the second chamber 90 is also known as a ‘solenoid chamber’. The solenoid 95 is electromagnetic and is configured to control a magnetic field when supplied with an electric current. To this end, the solenoid 95 is electrically coupled to a current supply. Preferably, parts of the upper section 50 of the regulator body 45 surrounding the solenoid chamber 90 is provided by way of ferromagnetic parts 100a, 100b, 100c, which provide a path for the magnetic flux of the solenoid 95.

Inside the first or middle chamber 85, a movable magnetic armature 105 is arranged, the movable magnetic armature 105 being configured to move within the first chamber 85 under the action of the solenoid 95. For this reason, the first chamber 85 is also known as the ‘armature chamber’.

The first chamber 85 and the magnetic armature 105 are shaped such that the magnetic armature 105 can move between upper and lower walls 110, 115 of the first chamber 85. In a preferred embodiment, the first chamber 85 defines a substantially cylindrical cavity and the magnetic armature 105 has a substantially cylindrical exterior. Each have substantially the same radius (extending about axis L), but the height of the chamber is longer than the height of the cavity (along axis L). This allows the magnetic armature 105 to move up and down along axis L within the first chamber 85 under the influence of the solenoid 95.

Preferably, the pressure regulator 1 is configured such that there is always a slight gap between the armature 105 and each of the upper and lower walls 110, 115 of the first chamber 85 regardless of the position of the armature 105 within the first chamber 85. This prevents the armature 105 from coming into engagement with the upper and lower walls 110, 115 as it moves along the axis L

The magnetic armature 105 and the solenoid 95 are configured such that when the solenoid 95 is provided with current, it attracts the magnetic armature 105 and draws the magnetic armature 105 towards the solenoid 95 and hence upwards along the L axis towards the top of the armature chamber 85. To this end, the armature 105 may be made of any suitable material to render it magnetic and hence movable by the solenoid 95 when provided with current. The armature 105, the solenoid 95 and the ferromagnetic parts 100 make up the solenoid actuator 30 described above.

To provide a compact arrangement, the movable armature 105 is annular and defines a first substantially cylindrical armature recess 123 therein to accommodate both the valve pin 70 and parts of the dual-spring system 25, particularly the first spring 35 and a housing I sleeve 120 for accommodating the first spring 35.

The recess 123 is provided centrally in the armature 105 and extends downwardly from the upper surface of the armature, part-way along the length of the armature 105, to define a base or floor 125 for the recess 123. The base 125 of the recess 123 defines an abutment surface for direct engagement with a lower end of the first spring 35. In this way, the armature 105 is able to compress the first spring 35 through direct engagement with the first spring 35. In other words, the armature 105, by way of the abutment surface thereof, physically contacts the first spring 35 to apply compression thereto.

A passage extends down from the base 125 of the recess 123 to the lower surface of the armature 105. The passage tightly/ rigidly accommodates the valve pin 70 such that when the armature 105 is moved, the valve 20 moves along with it.

As stated above, the pressure regulator 1 is provided with the dual-spring system 25 to urge against/ resist the movement of the solenoid actuator 30.

The dual-spring system 25 is provided with a substantially cylindrical spring housing/ sleeve 120 for accommodating/ housing the first spring 35 within the armature 105. Preferably, this spring housing 120 also accommodates the second spring 40, as shown in Figure 1 , thereby simplifying the arrangement of the pressure regulator 1 .

The spring housing 120 is held in place in the regulator body 45 by way of a guide 140, within which it is received. The guide 140 is tightly arranged within a bore of the upper section 50 of the regulator body 45 above the armature chamber 85, the bore extending vertically along axis L all the way through the middle of the upper section 85 from the top of the upper section 50 to the armature chamber 45. The guide 140 extends all the way from above the upper section 50, down along axis L until the armature chamber 85 (and defines at least a part of the upper wall 110 of the armature chamber 85 there). The spring housing 120 is enclosed within an internal cavity of the guide 140, said cavity extending vertically along axis L all the way through the middle of the guide 140 from its upper end to its lower end. However, the spring housing 120 is not contained completely within the guide 140 and instead extends out from the bottom of the internal cavity of the guide 140, into the armature chamber 85 and into the recess in the armature 105.

To provide a compact arrangement of the pressure regulator 1 , the first spring 35 and the second spring 40 are preferably arranged in series. In other words, the first spring 35 and second spring 40 are aligned along the axis L and are connected together between the upper end of the first spring 35 and the lower end of the second spring 40.

To this end, the spring housing 120 includes a first annular portion 145 at its lower end that defines a first recess that accommodates the first spring 35, a second annular portion 150 at its upper end that defines a second recess that accommodates at least a part of the second spring 40, and an annular middle section 160 between the first and second annular portion 145, 15 that defines a middle recess therein for slidably accommodating an upper section 130 of the valve pin 70. In this way, the spring housing 120 encloses at least a part of the first spring 35, at least part of the second spring 40 and at least a part of the valve pin 70 extending through the first and second springs 35, 40.

The recess defined in the lower annular portion 145 of the spring housing 120 defines a step 162 at its upper surface where it meets with the middle section 160 of the spring housing 120. The step 162 defines an abutment surface for the first spring 35, and so defines a surface against which the upper end of the first spring 35 is compressed under the action of the armature 105 during the first phase of movement. Likewise, the middle section 160 of the spring housing 120 is configured to apply force to the second spring 40 to compress it when the middle section 160 is moved upwards under the action of the armature 105 during the second phase of movement.

The valve pin 70 is slidably received within the first spring 35, the recess of the middle section 160 and the lower end of the second spring 40 such that, as the armature 105 is moved, the valve pin 70 (rigidly connected to the armature 105 within the passage) can move through the first spring 35, the middle section 160 and the second spring 40, while simultaneously still functioning as a guide for each of the first and second springs 35, 40.

The first annular portion 145 of the housing 120 (and hence the first spring accommodated therein) is slidably arranged within the recess 123 of the armature 105.

The end of the second spring 40 opposite the middle section 160 (i.e. , the upper end of the second spring 40) is fixedly connected to, and hence held in position by, an end plate 135 of the pressure regulator 1 that extends across the end of the second spring 40, i.e. in the plane perpendicular to axis L, above the upper section 10 of the body 45. The end plate 135 is connected to guide 140 and is thereby fixable in a position relative to the regulator body 45. Since the end plate 135 is fixable in position, when the armature 105 is moved upwards under the effect of the solenoid 95, the first and second springs 35, 40 may be compressed.

An explanation as to how the armature 105 is operable to engage with the dualspring system 25 to control the movement of the valve 20 will now be provided.

As shown in Figure 1 , when the valve 20 is in the closed position - i.e., when the solenoid 95 is not provided with any current and the dual-spring system 25 urges the valve 20 into the closed position - the abutment surface of the recess floor 125 in the armature 105 is arranged to directly engage with/ is physically touching the lowermost end 175 of the first spring 35. In this condition, the first spring 35 extends out the bottom of the first recess of the first annular portion 145 and the second spring 40 extends out the top of the second recess of the second annular portion 150. Accordingly, a first gap 165 is defined/ extends between the recess floor 125 of the armature 105 and the lowermost end 180 spring housing 120 along the L axis (as best seen in Figure 4) and a second gap 170 is defined/ extends between the spring housing 120 and the end plate 135 along the L axis (as best seen in Figure 1). Accordingly, the armature 105 is disengaged with the lowermost end 180 of the housing 120 in this position.

If the solenoid 95 is supplied with current less than the current threshold, the armature 105 is moved upwards by a first amount, and the armature 105 starts to compress the first spring 35 (i.e., shorten its length). Because the first spring 35 has a different compression characteristic to the second spring 40, only the first spring 35 is compressed in this first phase of movement of the armature (i.e., only the length of the first spring 35 is shortened) . When the first and second springs 35, 40 are arranged in series, the first spring 35 is preferably preloaded with a greater force than the second spring 40 such that only the first spring 35 undergoes compression (only the length of the first spring 35 is shortened) during the first phase of movement of the armature 105.

As the first spring 35 is compressed (i.e., as its length is shortened), the first gap 165 between the recess floor 125 and the lowermost end 180 of the spring housing 120 starts to close. During this first phase of movement, the first spring 35 undergoes compression while the second spring 40 remains at the same level of compression.

Referring to Figure 2, when current applied to the solenoid 95 reaches the current threshold, the armature 105 has moved all the way through the first gap 165 and the first gap 165 is closed by the armature 105 such that the abutment surface of the recess floor 125 of the armature 105 now directly engages with/ abuts against/ physically touches the lowermost end 180 of the housing 120.

Because the spring housing 120 is rigid, the lowermost end 180 of the spring housing 120 prevents the armature 105 from compressing the first spring 35 any further in this position (it is “fully” compressed), and if more current is applied to solenoid beyond the current threshold (such that the armature 105 is pulled upwards even further), the armature 105 applies an upward force on the housing 120 only, thereby forcing the spring housing 120 (and the “fully” compressed first spring 35 accommodated inside) to move upwards. In other words, the first spring 35 remains at the same level of compression within the housing spring 120 (i.e. , its length remains the same) as the second spring 40 underdoes compression (i.e., its length is shortened). At this point, as the spring housing 120 is applying an upward force on the second spring 40, the second spring 40 begins to compress (i.e., its length is shortened) as it reacts against the end plate 135. The first spring 35 remains at substantially the same level of compression/ length during this phase of movement. Since the valve pin 70 is rigidly engaged with the housing 120, the compression of the second spring 40 moves the valve 20 further up, thereby providing the second phase of movement of the valve 20.

In this way, it can be understood how the spring housing 120 acts as the ‘intermediate element’ between the armature 105 and the second spring 40, since the armature 105 is only able to compress the second spring 40 through engagement with the spring housing 120, and because the spring housing 120 transfers the motion of the armature 105 from the first spring 35 to the second spring 40.

The armature 105 is therefore operable to compress the second spring 40 via the intermediate element 120 only once the armature 105 has moved through the first gap 165/ the first spring 35 is compressed by a first compression amount. Thereafter, the armature 105 remains engaged with the intermediate element 120, thereby preventing the armature 105 from compressing the first spring 35 any further, while simultaneously applying compression to the second spring 40.

In Figure 3, the maximum possible current is applied to the solenoid 95 such that the valve 20 is in the most open position possible. Here both the first and second springs 35, 40 are “fully” compressed (i.e., as compressed as possible under the movement of the armature 105). In this condition, the first and second springs 35, 40 are completely enclosed within the first and second annular portions 145, 150 respectively such that there is no gap between the recess floor 125 of the armature 105 (i.e. the first gap 165 is closed) and the spring housing 120 and no gap between the spring housing 120 and the end plate 135 (i.e., the second gap 170 is closed). Despite this, there is still preferably a slight armature gap 185 between the armature 105 and the upper wall 110 of the armature chamber 85. This is achieved when the sum of the lengths of the first and second gaps 165, 170 is less than the length of the gap between the armature 105 and the upper wall 110 of the armature chamber 85 when the solenoid is not supplied with current. This arrangement advantageously ensures that the armature 105 does not come into engagement with the upper wall 110 of the armature chamber 85 during use of the pressure regulator 1.

In view of the above, it can be understood how the first gap 165 determines when the switch occurs between the first spring 35 compressing and the second spring 40 compressing (i.e., the switch point), while the second gap 170 determines the limit on how much the second spring 40 can compress and hence the limit on how much the valve 20 can be opened.

Figure 5 relates to one preferred configuration of the solenoid actuator 30 and the dual-spring system 25, where the pressure regulator 1 delivers fuel into the common rail in accordance with the curve. Here, the current applied to the solenoid 95 is shown on the X-axis of the graph, while the rate of fuel flowing out of the pressure regulator 1 is shown on the Y-axis of the graph.

In this configuration, the first spring 35 has a first stiffness that is larger than a second stiffness of the second spring 40. This has the effect that the first spring 35 is more resistant to compression than the second spring 40 and so it compresses more slowly than the second spring 40. In other words, because the first spring 35 is stiffer, a larger change of force (i.e., current) is required to generate a smaller change of lift , whereas because the second spring 40 is softer, a smaller change of force (i.e., current) is required to generate a larger change of lift. This means that as the current supplied to the solenoid actuator 30 is increased, the valve 20 is moved more precisely during the first phase of movement than in the second phase of movement, and more precise control of the valve 20 at lower currents is achieved.

Accordingly, the curve takes the form of a first line 190 extending up from the origin O of the graph with a first gradient to point P and a second line 195 extending from point P with a second gradient up to point M (the second gradient being larger than the first gradient).

Here:

• The first line 190 corresponds to the first phase of movement of the valve 20,

• The second line 195 corresponds to the second phase of movement of the valve 20,

• Point O corresponds to the point where valve 20 is closed (i.e., when the regulator 1 is in the configuration of Figure 1),

• Point P corresponds to the switch point between the two springs 35, 40 (where the current supplied to the solenoid 95 equals current threshold Ce - i.e., when the regulator 1 is in the configuration of Figure 2), and

• Point M corresponds to the point where the valve 20 is in its most open position (where the maximum current CM is applied to the solenoid 95 - i.e., when the regulator 1 is in the configuration of Figure 3).

The curve takes the form of straight lines because the rate of fuel flowing out of the pressure regulator 1 (i.e., the delivery flow) is substantially proportional to the current supplied to the solenoid 95 for all levels of current. This is because the force generated by the solenoid actuator 30 is substantially proportional to the current supplied thereto, and because the flow of fuel out of the pressure regulator 1 is substantially proportional to the force generated by the solenoid actuator 30, regardless of which of the first and second springs 35, 40 is undergoing compression.

The gradients of the two lines - i.e., the rate of change of flow out of the pressure regulator 1 per unit of current - differ depending on whether less current is supplied to the solenoid 95 or more current is supplied to the solenoid 95. The first line 190 shows a more gentle slope, while the second line 195 has a steeper slope. This is because when low levels of current (i.e., less than the current threshold Ce) are supplied to the solenoid, the first spring 35 determines the first phase of movement of the valve 20 and because when high levels of current (i.e., more than the current threshold Ce) are supplied to the solenoid, the second spring 40 determines the second phase of movement of the valve 20, and because the valve 20 moves more slowly when compressing the first spring 35 compared to the second spring 40. Hence, the rate of change of flow out of the pressure regulator 1 can be controlled more precisely for lower currents than for higher currents. This allows for precise control of low pressure fuel in the common rail both when the engine has a low demand for fuel (e.g., when the engine is idling) and when the engine has a high demand for fuel.

Other features of the pressure regulator 1 will now be described.

To control how much current is provided to the solenoid 95 (i.e., to control the operation of the pressure regulator 1), the fuel injection may be provided with an Electronic Control Unit (ECU) (not shown). Since the common rail (not shown) must work with a predefined pressure, the ECU acts to maintain it by means of the pressure regulator 1 . The pressure regulator 1 delivers a given amount of fuel in dependence on the signal received by the ECU.

In one particularly preferred embodiment, the first spring 35 is preloaded with just enough force to keep the valve 20 in the closed position when the solenoid actuator 30 is not energised, and the armature 105 only begins to compress the first spring 35 after the solenoid actuator 30 is energised. Likewise, the second preload of the second spring 40 is preferably configured such that immediately after the first spring 35 is “fully” compressed (i.e. after the armature 105 has passed all the way through the first gap 165), the force being provided by the solenoid actuator 30 is large enough to commence the compression of the second spring 40.

To this end, the pressure regulator 1 comprises a first adjustment means for adjusting the first preload on the first spring 35, and a second adjustment means for adjusting the second preload on the second spring 40. In this way, the preloads can be fine-tuned to achieve the above-mentioned advantageous operation of the pressure regulator 1 (where the first spring 35 engages as soon as current is supplied to the solenoid 95 and where the second spring 40 engages immediately after the first spring 35 is ‘fully’ compressed) .

The first adjustment means may be provided by a movable form of the guide 140 which is adjustable to move up and down along the axis L under operator control. In particular, the guide 140 may be configured such that a user can adjust the vertical position thereof, and hence control the vertical position of the intermediate element 120, and hence control how compressed the first spring 35 is during operation of the pressure regulator 1 (and hence adjust the first preload of the first spring 35). In one example, therefore, instead of the lower end of the guide 140 being flush with the lower end of the housing 100c, the lower end of the guide 140 may project into the armature chamber 185. When the intermediate element 120 is then inserted into the assembly, it drops into a lower position (i.e. , closer to the armature 105), hence reducing the first gap 165. This alters the switch point of the characteristic shown in Figure 5. A first nut 205 can then be used to secure the guide 140 in the correct, adjusted position.

Additionally or alternatively, the first adjustment means may take the form of a shim (not shown) that may be arranged between the top of the first spring 35 and the housing 120 to adjust the first gap 165 between the recess floor 125 and the housing 120, and hence the compression level of the first spring 35 during operation of the pressure regulator 1 (and hence adjust the first preload of the first spring 35).

The second adjustment means may be provided by a movable form of the end plate 135 that can move up and down along the axis L. In particular, the end plate 135 may be configured such that a user can adjust the vertical position thereof, and hence control how compressed the second spring 40 is during operation of the pressure regulator 1 (and hence adjust the second preload of the first spring 35). A second nut 210 may be used to ensure that the end plate 135 stays in position. A self-locking feature (not shown) can be used to fix the second nut 210 in position.

Variations on the pressure regulator 1 described above will also be apparent to the skilled person. For example, the pressure regulator 1 may also be used as part of a liquid (e.g., diesel) injection system. Likewise, the intermediate element 120 may take other forms than the above-described spring housing/ sleeve.

Feature reference numerals

Pressure regulator 1

Inlet 5

Outlet 10

Valve 20

Dual-spring system 25 Solenoid actuator 30

First spring 35

Second spring 40

Body 45

Upper section 50

Lower section 55

Valve seat 60

Valve head 65

Valve pin 70

First/ centre/ armature chamber 85

Second I annular/ solenoid chamber 90

Solenoid 95

Ferromagnetic parts 100a, 100b, 100c

Armature 105

Upper wall of the first chamber 110

Lower wall of the first chamber 115

Spring housing/ sleeve/ intermediate element 120

Recess of the armature 123

Recess base or floor 125

Upper section of valve pin 130

End plate/ second adjustment means 135

Guide/ first adjustment means 140

First annular portion 145

Second annular portion 150

Middle section of the housing 160

Step 162

First gap 165

Second gap 170

Lowermost end of the first spring 175

Lowermost end of the housing 180

Armature gap 185

First part of the curve 190

Second part of curve 195

First nut 205

Second nut 210

Claims

CLAIMS:

1. A pressure regulator (1) for a common rail of a high pressure hydrogen injection system, the pressure regulator (1) comprising: an inlet (5) for delivering fuel into the pressure regulator (1), an outlet (10) for supplying fuel out of the pressure regulator (1) and into the common rail, a fuel path for fuel flow between the inlet (5) and the outlet (10), a valve (20) movable between a closed position, wherein the valve (20) is arranged to block the fuel path, and a plurality of open positions, wherein the valve (20) is arranged to at most partially block the fuel path, each open position corresponding to a different position of the valve (20) with respect to the fuel path, a dual-spring system (25) arranged to urge the valve (20) towards the closed position, the dual-spring system (25) comprising a first spring (35) with a first compression characteristic and a second spring (40) with a second compression characteristic different to the first compression characteristic, and a solenoid actuator (30) configured to draw the valve (20) away from the closed position against the action of the dual-spring system (25) to one of the open positions when the solenoid actuator (30) is supplied with current, wherein the pressure regulator (1) is configured such that: the valve (20) is maintained in the closed position when the solenoid actuator (30) is not supplied with current, the first spring (35) is compressed by a first distance thereby providing a first phase of movement of the valve (20), when the solenoid actuator (30) is supplied with current less than or equal to a current threshold, and the second spring (40) is compressed by a second distance thereby providing a second phase of movement of the valve (20) following the first phase of movement, when the solenoid actuator (30) is supplied with current exceeding the current threshold.

2. The pressure regulator (1) of Claim 1 , wherein the first spring (35) has a first stiffness and the second spring (40) has a second stiffness, and wherein the first stiffness is larger than the second stiffness.

3. The pressure regulator (1) of Claim 1 or Claim 2, wherein the first spring (35) and the second spring (40) are arranged in series, and wherein the first spring (35) is preloaded with a first force and the second spring (40) is preloaded with a second force, and wherein the first force is less than the second force.

4. The pressure regulator (1) of any preceding claim, wherein the solenoid actuator (30) comprises a movable armature (105) coupled to the valve (20), and wherein the movable armature (105) is configured to compress the first and second springs (35, 40) in dependence on the current supplied to the solenoid actuator (30).

5. The pressure regulator (1) of Claim 4, wherein the armature (105) is configured to compress the first spring (35) through direct engagement with the first spring (35).

6. The pressure regulator (1) of Claim 4 or Claim 5, wherein the dual-spring system (25) comprises an intermediate element (120) and the armature (105) is configured to compress the second spring (40) through engagement with the intermediate element (120).

7. The pressure regulator (1) of Claim 6, wherein the pressure regulator (1) is configured such that a gap (165) is defined between the armature (105) and the intermediate element (120) when the solenoid actuator (30) is not supplied with current, and the armature (105) is operable to compress the second spring (40) via the intermediate element (120) only once the armature (105) has moved through the gap (165).

8. The pressure regulator (1) of Claim 6 or Claim 7, wherein the pressure regulator (1) is configured such that the armature (105) remains engaged with the intermediate element (120) during the second phase of movement, thereby preventing the armature (105) from compressing the first spring (35) during the second phase of movement.

9. The pressure regulator (1) of any of Claims 6 to 8, wherein the intermediate element (120) includes a first annular portion (145) defining a first recess, and wherein the first recess encloses at least a part of the first spring (35).

10. The pressure regulator (1) of any of Claims 6 to 9, wherein the intermediate element includes a second annular portion (150) defining a second recess, and wherein the second recess encloses at least a part of the second spring (40).

11. The pressure regulator (1) of any of Claims 6 to 10, wherein the armature (105) is annular and defines an armature recess (123) , and wherein the armature recess (123) encloses at least a part of the intermediate element (120).

12. The pressure regulator (1) of any preceding claim, wherein the pressure regulator (1) comprises a first adjustment means (140) for adjusting a first preload on the first spring (35).

13. The pressure regulator (1) of any preceding claim, wherein the pressure regulator (1) comprises a second adjustment means (135) for adjusting a second preload on the second spring (40).