Technical Field

The present invention relates to a hydraulic fluid supply circuit for engines, specifically internal combustion engines, and a regulator valve for regulating a flow of hydraulic fluid.

Background

Internal combustion engines, such as four- stroke diesel engines, may comprise variable valve train components. Valve train assemblies may include a camshaft that rotates with engine speed to sequentially move a rocker arm and valve. An eccentric cam lobe determines the movement of, for example, a push rod for each revolution of the camshaft. Valve train assemblies may comprise hydraulic lash adjusters (HLAs) for taking up slack in a valve train. Engines equipped with HLAs can suffer from the so-called phenomena of “pump-up” of the HLA. Pump-up occurs when the oil pressure in the HLA is unbalanced inside the valve train system. In this condition, the HLA elongates and can prevent complete closure of the valve. Reducing or eliminating the effect of pump-up in hydraulic fluid supply circuits helps to reduce fuel consumption because energy losses are minimised.

Summary

Aspects of the present invention are listed in the accompanying claims.

Features of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which:

List of Figures

Figure 1 illustrates schematically a perspective view of an engine sub-assembly comprising a hydraulic fluid supply circuit according to an example;

Figure 2 illustrates schematically a side view of a conventional valve train assembly;

Figure 3 illustrates schematically a longitudinal cross-sectional view of an hydraulic lash adjustor; Figure 4 illustrates schematically a perspective view of a regulator valve according to an example;

Figure 5 illustrates schematically separated parts of the regulator valve shown in Figure 4;

Figure 6 illustrates schematically a cross-sectional side view of the regulator valve shown in Figure 4 in an open position according to an example;

Figure 7 illustrates schematically a cross-sectional side view of the regulator valve shown in Figure 4 in a closed position according to an example;

Figure 8 illustrates hydraulic fluid pressures of a hydraulic circuit at different temperatures with and without a regulator valve according to an example; and

Figure 9 illustrates hydraulic fluid flow rates of a hydraulic circuit at different temperatures with and without a regulator valve according to an example.

Throughout, like reference signs denote like features.

Description

Referring to Figure 1, a schematic perspective view of an engine sub-assembly 100 comprising a hydraulic fluid supply circuit 5 according to an example is shown. The hydraulic fluid supply circuit 5 is suitable for an internal combustion (IC) engine. The IC engine may comprise a plurality of cylinders (not shown) and may be a compression ignition (Cl) engine suitable for diesel fuel combustion. Preferably, the IC engine is a four-stroke combustion engine.

The engine sub-assembly 100 shown in Figure 1 comprises a valve train assembly 202 to open and close valves 211 (of which one is shown in Figure 2) of the engine. The valve train assembly 202 comprises four rocker arm assemblies. In some examples, the valve train assembly 202 comprises a single rocker arm assembly. Although three rocker arm assemblies 201, 20G, 201” are fully visible in the view shown, the fourth rocker arm assembly comprises the same features and operates in the same manner. Each rocker arm assembly 201, 20G, 201” acts on a respective valve stem 210, 210’, 210” against the force of a valve spring (not shown) to thus open a respective valve 211. The valve train assembly 202 also comprises a plurality of Hydraulic Lash Adjusters (HLA) 200 (of which one is visible in Figure 1). Each HLA 200 is to take up slack in the valve train assembly 202 by accounting for thermal variation of the valve train assembly 202 and/or engine components. The specific operation of each HLA 200 is described in more detail below in relation to Figure 3. Although only one HLA

200 is visible in Figure 1, each of the four rocker arm assemblies 201, 20 G, 201” comprises a respective HLA 200 to interact with each respective rocker arm 204, 204’, 204”. One end 208 of each rocker arm 204, 204’, 204” engages the respective valve stem 210, 210’, 210”. The other end 212 of each rocker arm 204, 204’, 204” is mounted for pivotal movement on the respective HLA 200. Each rocker arm 204, 204’, 204” is also provided with a roller 214 mounted on an axle 216 carried by the rocker arm 204, 204’, 204”. In the example shown, each roller 214 is mounted on a different respective axle 216. In some examples, the axle 216 is a common axle that each roller 214 is mounted on.

The valve train assembly 202 is shown schematically in Figure 2. A cam 218, mounted on a cam shaft 215, comprises a cam profile. The cam profile comprises a base circle 219 and a lobe 217 to engage the roller 214 and thus pivot the rocker arm 204 anti-clockwise, as shown in Figure 2. This depresses the valve stem 210 against the force of a valve spring (not shown) and thus opens the valve 211. As the cam 218 continues to rotate, and the base circle 219 of the cam profile engages the roller 214, the valve spring returns the valve 211 and the rocker arm 204 to the position shown in Figure 2.

As is well known, the HLA 200 has a chamber (not illustrated in Figure 2) for containing hydraulic fluid (such as oil) and a spring (also not illustrated in Figure 2) arranged to enlarge the chamber and thus extend the HLA 200. Hydraulic fluid flows into the chamber via a one-way valve (also not illustrated in Figure 2), but can escape the chamber only slowly, for example via closely-spaced leak-down surfaces. Accordingly, the HLA 200 of Figure 2 can extend to accommodate any slack in the valve train assembly 202, such as between the cam 218 and the roller 214. After the HLA 200 is extended, however, the chamber, filled with hydraulic fluid, provides sufficient support for the pivoting movement of the rocker arm 204.

Although the arrangement described above works well during normal running conditions, problems can arise when starting the engine from cold. As the engine components heat up, there is expansion and relative movement between them. To accommodate this, the HLA 200 expands as described above. However, the heating of some engine components causes a different type of movement which requires the subsequent shrinking of the HLA 200 to ensure that the valve 211 closes. This does not however occur sufficiently quickly, because the HLA 200 can shrink only slowly, especially when the hydraulic fluid is still cold. This results in the valve 211 remaining open (see open valve 21 G, as shown by dotted lines in Figure 2), causing starting problems.

Referring to Figure 3, the HLA 200 is shown in detail. The HLA 200 has a cylindrical body 222 formed with a longitudinal blind bore 224. A plunger assembly 226 is mounted for sliding motion inwardly and outwardly of the bore 224. The plunger assembly 226 and blind bore 224 define between them a high-pressure chamber 228 at the lower end of the HLA 200. An aperture 230 at the bottom of the plunger assembly 226 allows hydraulic fluid to flow between a low-pressure chamber, or reservoir, 232 within the plunger assembly 226 to the high-pressure chamber 228.

Below the aperture 230, a ball valve is provided. The ball valve comprises a ball 234 captured by a cage 236 and biased by a spring 238 to a position closing the aperture 230.

The plunger assembly 226 is biased outwardly of the body 222 by a spring 240. The plunger assembly 226 is formed of two parts, an outer part 246 which carries an outer end surface 242, and an inner part 248, which slides in the bore 224 by engagement between an outer surface 244 of the inner part 248 and internal walls of the bore 224. The outer part 246 has a stem 250 mounted for sliding movement within a bore 252 in the inner part 248, and has an enlarged head 254. The outer part 246 is retained within the bore 252 by a clip 256 held in a groove 258.

A spring washer 260 is mounted between the head 254 of the outer part 246 and the top of the inner part 248, and biases the outer part 246 outwardly.

In operation, each time the lobe 217 of the cam 218 (see Figure 2) operates to open the valve 211, the outer part 246 of the HLA 200 is first pushed inwardly to compress the spring 260 before further movement is prevented by the high-pressure chamber 228. Only then does the valve 211 start to open. As the base circle 219 of the cam 218 is reached, the lost motion between the outer and inner parts 246, 248 of the plunger assembly 226 is restored by the spring 260. If subsequent expansion of the engine components results in the requirement for the HLA 200 to contract in order to permit closing of the valve 211, this is permitted by the movement between the outer part 246 relative to the inner part 248 of the plunger assembly 226. Thus, the difference between the desired versus actual HLA position would be taken up by the outer part 246 not completely returning to the outer position shown in Figure 3.

If, at a later stage, there is a tendency for an increased amount of slack in the valve train assembly 202, the outer part 246 will first tend to move back to its outer position due to the force of the spring 260 before any additional slack is taken up by outward movement of the inner part 248 of the plunger assembly 226 and expansion of the chamber 228 under the force of the spring 240.

To achieve correct operation, the spring 260 is specified so that the force it applies to the valve stem 210 when it is fully compressed is less than the pre-load force of the valve spring in the closed position of the valve 211. This ensures that the valve spring is sufficiently powerful to close the valve 211 against the force produced by the spring 260. Also, the pre-load force of the spring 260 is calculated to be greater than the sum of the HLA return spring 240 and the hydraulic fluid pressure forces in the chamber 228. In other words, the spring 260 is sufficiently powerful as to prevent the inner part 248 of the plunger 226 from moving outwardly to take up the lost motion between the inner part 248 and outer part 246.

Referring back to Figure 1, each HLA 200 is provided in the hydraulic fluid supply circuit 5. The circuit 5 is to supply each HLA 200 with pressurised hydraulic fluid to operate the HLA 200. In some circumstances, the hydraulic fluid pressure forces in the chambers 228 and/or 232 (shown in Figure 3) of a given HLA 200 exceed normal operating conditions. This may occur when the hydraulic fluid pressure across the HLAs 200 becomes unbalanced. In this condition, an HLA 200 receives an excess pressure (e.g. overpressure) which results in an elongation of the HLA 200. This can result in an open valve 21 G when the valve 211 should be closed. An unbalanced valve train assembly 202 resulting in excessive hydraulic fluid pressures is referred to as “pump-up” of the HLA 200.

To avoid the problems associated with pump-up of the HLA 200, and other possible problems with excessive pressure on the HLA 200, the inventors have devised the hydraulic fluid supply circuit 5, shown in Figure 1, and a regulator valve 1 shown in Figures 1, and 4 to 7. Test data is shown in Figures 8 and 9.

The circuit 5 comprises the regulator valve 1 for regulating a flow of hydraulic fluid from a pressurised source to the HLA 200. In some examples, the pressurised source of hydraulic fluid is hydraulic fluid expelled from a pump (not shown), such as an engine oil pump.

The circuit 5 is to inhibit pump-up of the HLA 200 in order to provide a balanced valve train assembly 202. This enables each valve event to be accurately controlled so that each valve 211 is not open when it should be closed.

The circuit 5 comprises a first section 104, 106, fluidically connected to the HLAs 200, and a second section 102, fluidically connected to the pressurised source. The first section 104, 106 comprises a first portion 104 and a second portion 106 which are joined at a junction. The regulator valve 1 is positioned between the first section 104, 106 and the second section 102 to regulate the flow of hydraulic fluid from the second section 102 to the first section 104, 106.

Hydraulic fluid is supplied to the regulator valve 1 in an inlet direction 2 with a second pressure P2 and second flow rate Q2. Hydraulic fluid travels from the regulator valve 1 and towards the HLA 200 in an outlet direction 4 with a first pressure PI and first flow rate Ql. As shown in Figures 8 and 9, the regulator valve 1 is to control a hydraulic fluid pressure or hydraulic fluid flow rate in the first section 104, 106, respectively, as shown by the first pressure PI and first flow rate Ql readings.

The hydraulic supply circuit 5 is provided in a housing 110 of the engine. In the example shown in Figure 1, the housing 110 is a cylinder head of the engine. However, in some examples, the housing 110 may be a cylinder block of the engine. In other examples, the housing 110 may be both the cylinder block and cylinder head of the engine.

The first section 104, 106 and the second 102 section form a hydraulic fluid gallery of the cylinder head. The first section 104, 106 may be referred to as the HLA gallery, and the second section 102 may be referred to as the hydraulic fluid supply gallery. In the example shown in Figure 1, the regulator valve 1 is provided within the hydraulic fluid gallery of the cylinder head. In the example shown, the inlet direction 2 is orthogonal to the outlet direction 4. In some examples, the inlet direction 2 may be parallel to the outlet direction 4.

Referring to Figures 4 to 7, the regulator valve 1 is shown in greater detail.

Figure 4 shows a schematic perspective view of the regulator valve 1 according to the example. The regulator valve 1 comprises an inlet 12, an outlet 14, an inner body 20, and a hollow outer body 10. In this example, the inner body 20 acts as a piston to reciprocate within the outer body 10. The inlet 12 is to enable hydraulic fluid to flow into the regulator valve 1 from the second section 102 shown in Figure 1. The outlet 14 is to enable hydraulic fluid to flow out of the regulator valve 1 to the first section 104, 106 shown in Figure 1.

The inlet 12 and outlet 14 are separated by a first shoulder portion 19 of the outer body 10, as best shown in Figure 5. The first shoulder portion 19 is to engage with an internal wall of the gallery to prevent fluidic connection between the inlet 12 and outlet 14 around the periphery of the outer body 10. As best shown in Figures 6 and 7, the first shoulder portion 19 is a thickened portion of the outer body 10. The first shoulder portion 19 has a greater diameter than a diameter of a portion of the outer body 10 that forms the inlet 12. The diameter of the first shoulder portion 19 is also greater than a diameter of a portion of the outer body 10 that forms the outlet 14. In some examples, the diameter of the first shoulder portion 19 is greater than a diameter of a portion of the outer body 10 that contributes to forming at least a part of the inlet 12. In some examples, the diameter of the first shoulder portion 19 is greater than a diameter of a portion of the outer body 10 that contributes to forming at least a part of the outlet 14.

As shown in Figures 5-7, the regulator valve 1 comprises a first end 11 that is tapered. This helps to increase an efficiency of flow of the hydraulic fluid as the hydraulic fluid arrives at the regulator valve 1. The tapered first end 11 encourages hydraulic fluid towards the inlet 12 in a more efficient fashion that a non-tapered or flat end, which is orthogonal to a direction of flow of the hydraulic fluid. The tapered first end 11 helps guide the hydraulic fluid towards the inlet 12, which is arranged at the periphery of the outer body 10.

As best shown in Figure 5, a second end 13 of the regulator valve 1 comprises a second shoulder portion 18 of the outer body 105. The second shoulder portion 18 is to engage with an internal wall of the gallery to prevent passage of hydraulic fluid past the second end 13 of the regulator valve 1. The first and second shoulder portions 19, 18 serve to fluidically contain the outlet 14. Thus, the first and second shoulder portions

19, 18 combine to prevent hydraulic fluid exiting the regulator valve 1 through the outlet 14 and connecting with the inlet 12 around the periphery of the outer body 10. As best shown in Figures 6 and 7, the second shoulder portion 18 is a thickened portion of the outer body 10.

The second shoulder portion 18 has a greater diameter than a diameter of a portion of the outer body 10 that forms the inlet 12. The diameter of the second shoulder portion 18 is also greater than a diameter of a portion of the outer body 10 that forms the outlet 14. In some examples, the diameter of the second shoulder portion 18 is greater than a diameter of a portion of the outer body 10 that contributes to forming at least a part of the inlet 12. In some examples, the diameter of the second shoulder portion 18 is greater than a diameter of a portion of the outer body 10 that contributes to forming at least a part of the outlet 14.

As shown in Figures 4 and 5, the inlet 12 and outlet 14 of the regulator valve 1 each comprise a plurality of apertures. Although three apertures are visible for each of the inlet 12 and outlet 14 in the views of Figures 4 and 5, the inlet 12 and outlet 14 of the regulator valve 1 in this example comprise six apertures. In some examples, a single aperture may be used for the inlet 12 and/or the outlet 14. In some examples, the number of apertures used for the inlet 12 may be different to the number of apertures used for the outlet 14. The apertures of the inlet 12 and outlet 14 are circular. In some examples, at least one aperture of the inlet 12 and/or outlet 14 may be non-circular and may comprise at least one linear portion.

The apertures of the inlet 12 and outlet 14 are arranged radially around the perimeter of the outer body 10. In the example shown, the apertures of the inlet 12 and outlet 14 are equally spaced from each other. In some examples, a spacing or gap between adjacent apertures of the inlet 12 may vary. In some examples, a spacing or gap between adjacent apertures of the outlet 14 may vary. The apertures of the inlet 12 and the apertures of the outlet 14 are arranged circumferentially around the outer body 10. Further, each of the apertures of the inlet 12 is aligned with an adjacent aperture of the outlet 14 in the longitudinal direction of the outer body 10. As shown in Figure 5, the inlet 12 is located closer to the first end 11 than the outlet 14 is located to the first end 11. The outlet 14 is closer to the second end 13 than the inlet 12 is to the second end 13. Nevertheless, the inlet 12 is located closer to the first end 11 than the outlet 14 is located to the second end 13.

As best shown in Figures 6 and 7, the outlet 14 of the regulator valve 1 is positioned at a substantially central portion along the length of the regulator valve 1. That is, the outlet 14 is located about halfway (50% of the distance) from the first end 11 to the second end 13 of the regulator valve 1 along the longitudinal axis A-A of the regulator valve 1. The inlet 12 of the regulator valve 1 is positioned at approximately a quarter distance along the length of the regulator valve 1. That is, the inlet 12 is located about 25% of the distance from the first end 11 to the second end 13 of the regulator valve 1 along the longitudinal axis A-A of the regulator valve 1.

Figure 5 shows schematically separated parts of the regulator valve 1 shown in Figure 4 as an exploded view. The inner body 20 of the regulator valve 1 is shown outside of the outer body 10 for demonstration purposes. In use, the inner body 20 is contained within a bore 17 of the outer body 10 and the inner body 20 is configured to move with respect to the outer body 10.

The inner body 20 is contained within the outer body 10 by an end stop 15 (see Figures 6 and 7) and a circlip 50. The end stop 15 is a portion of the outer body 10 that protrudes into the bore 17 further than a first end 21 of the inner body 20, as best shown in Figures 6 and 7.

The circlip 50 is part of a biasing arrangement 60, shown in Figure 5. The biasing arrangement 60 is configured to urge the inner body 20 towards the first end 11 of the outer body 10.

The circlip 50 abuts a seat 40 onto which a spring 30 is located and expands into a groove in the outer body 10 once inserted into the outer body 10. The spring 30 is to pass over a second end 23 of the inner body 20 and surround an end portion 20a of the inner body 20. The spring 30 continues over the second end 23 until one end of the spring 30 abuts a first head portion 26 of the inner body 20. Thus, the circlip 50 not only retains the inner body 20 in the outer body 10 but also opposes a force between the spring 30 and the inner body 20.

The circlip 50 is a type of retainer. In some examples, a retainer other circlip 50 may be used as long as the retainer performs the retaining and spring force opposing functions. The circlip 50 is advantageous because it distributes force exerted by the spring 30 evenly and is easy to install and remove in the outer body 10 due to its mechanically flexibility.

As shown in Figure 5, the first head portion 26 of the inner body 20 is arranged between a first end 21 of the inner body 20 and the second end 23 of the inner body 20. The first end 21 is first insertable into the outer body 10 when the regulator valve 1 is assembled. Once assembled, the first end 21 is to abut the end stop 15 (see Figure 6 and 7) by action of the spring 30 on the first head portion 26 of the inner body 20. The first end 21 comprises a second head portion 28 which is raised away from a neck portion 27 in a similar manner to the first head portion 26.

Ramped portions 25, 29 are provided on the first and second head portions 26, 28. The ramped portions 25, 29 descend away from each of the first and second head portions 26, 28 in the longitudinal axis A-A direction towards the neck portion 27.

The neck portion 27 is a constriction of the inner body 20. That is, the neck portion 27 is relatively narrower than the first and second head portions 26, 28. The neck portion comprises an aperture 22 to allow hydraulic fluid to flow into and out of the inner body 20. Pressure exerted by the hydraulic fluid on the inner body 20 by flowing through the aperture 22 of the inner body 20 enables the regulator valve 1 to operate. This operation is discussed below in relation to Figures 6 and 7.

As shown in Figure 5, the outer body 10 comprises a neck portion 10a arranged between the first and second shoulder portions 19, 18. The neck portion 10a is a constriction of the outer body 10. That is, the neck portion 10a is relatively narrower than the first and second shoulder portions 19, 18. The neck portion 10a comprises the inlet 14.

A ramped portion 13a is provided on the second shoulder portion 18, which descends away from the second shoulder portion 18 in the longitudinal axis A-A direction of the regulator valve 1 and towards the neck portion 10a.

The outer body 10 further comprises an end portion 10b. The end portion 10b comprises the outlet 12. The end potion 10b is shown with substantially the same diameter as the neck portion 10a of the outer body 10. The end portion 10b comprises a conical shaped end which is shown as the first end 11.

Figures 6 and 7 show different orientations of the regulator valve 1 during operation of the regulator valve 1. Figure 6 shows schematically a cross-sectional side view of the regulator valve 1 in an open position and Figure 7 shows the same view of the regulator valve 1 in a closed position.

When installed in the circuit 5 of Figure 1, the regulator valve 1 is configured to prevent hydraulic fluid pressure or flow rate in the first section 104, 106 of the circuit 5 exceeding a first pre-determined value. In this example, the first pre-determined value is between 1.5bar and 2bar, as shown in Figure 8. In some examples, the first pre determined value is less than or equal to 2bar.

In the open position, the regulator valve 1 provides for fluidic connection between the inlet 12 and outlet 14. Here, the inlet 12 and outlet 14 are fully open. This is because the plurality of apertures of the inlet 12 are unblocked by the inner body 20. Hydraulic fluid can therefore flow through the inlet 12 and out of the outlet 14 when the regulator 1 is arranged in the open position.

In the open and regulated positions, the spring 30 exerts a force between an end stop 45 of the seat 40 and the first head portion 26 of the inner body 20 to urge the inner body 20 towards the first end 11 of the regulator valve 1. That is, the spring 30 is arranged as a compression spring to oppose a compression force acting on the spring 30. The spring 30 is arranged to bias the inner body 20 towards the first end 11 of the regulator valve 1.

In the open position, as shown in Figure 6, the first end 21 of the inner body 20 abuts the end stop 15 of the outer body 10. The inner body 20 is thus prevented to move away from the second end 13 of the regulator valve 1 by the end stop 15 of the outer body 10.

The regulator valve 1 is arrangeable between the open position and the regulated position by relative movement of the inner body 20 and the outer body 10. The inner body 20 is slidably moveable inside the bore 17 of the outer body 10. Portions of the inner wall of the bore 17 of the outer body 10 are to guide the first and second shoulder portions 19, 18 for translational motion of the inner body 10 within the bore 17. The hydraulic fluid in a second bore portion 17b of the bore 17 will, to some extent, act as a lubricant to reduce wear of the first and second shoulder portions 19, 18 and the portions of the inner wall. The regulator valve 1 is configured to retain hydraulic fluid in the second bore portion 17b. This occurs because passage of hydraulic fluid into a first bore portion 17a is prevented by the positional relationship between the second shoulder portion 18 and the portions of the inner wall of the bore 17.

The inner body 20 comprises an internal passage 6. The internal passage 6 is fluidically connected to a chamber 7 of the regulator valve 1. The internal passage 6 also fluidically connects the outlet 14 to the chamber 7. As shown in Figures 6 and 7, the chamber 7 is formed between the inner body 20 and outer body 10. Specifically, the chamber 7 is formed between the first end 21 of the inner body 20 and the conical shaped end of the end portion 10b of the outer body 10. In use, the chamber 7 is to expand and contract by hydraulic fluid pressure in the chamber 7 which causes relative movement of the inner body 20 and the outer body 10. Therefore, the chamber 7 may be referred to as an expansion chamber. The internal passage 6 connects an intermediate chamber 3 of the bore 17 to the expansion chamber 7. The intermediate chamber 3 surrounds the neck portion 27 of the inner body 20. The intermediate chamber 3, internal passage 6 and expansion chamber 7 form a space inside the outer body 10 that is to be occupied by hydraulic fluid, in use. The volume of the second bore portion 17b to contain hydraulic fluid therefore comprises respective volumes of the intermediate chamber 3, internal passage 6 and expansion chamber 7.

Since the internal passage 6 fluidica!ly connects the outlet 14 to the chamber 7, the internal passage 6 enables a supply of hydraulic fluid to the chamber 7 via the internal passage 6. This supply of hydraulic fluid provides for relative movement of the inner body 20 and the outer body 10 depending upon hydraulic fluid pressure in the chamber 7. When the expansion chamber 7 contracts, the inner body 20 is to enable a release of hydraulic fluid from the expansion chamber 7 via the internal passage 6. Hydraulic fluid supplied to the expansion chamber 7, via the internal passage 6, is to cause expansion of the expansion chamber 7 to arrange the regulator valve 1 in the regulated position or a further regulated position. Expansion of the chamber 7 is caused by an increase of fluid pressure in the chamber 7. The regulated position, or a further regulated position, corresponds to a first position of the regulator valve 1 that is to respectively inhibit or further inhibit the flow of hydraulic fluid from the inlet 12 to the outlet 14.

The internal passage 6 is arranged to enable a release of hydraulic fluid from the chamber 7 to cause contraction of the chamber 7 on the basis of a decrease of fluid pressure in the chamber 7. This arranges the regulator valve 1 in a second position to reduce the inhibition of flow of hydraulic fluid from the inlet 12 to the outlet 14 relative to the first position. The second position may be a regulated position of the regulator valve 1 or the open position of the regulator valve 1.

The internal passage 6 comprises a first aperture 22 and a second aperture 24. The first aperture 22 is located between the first and second ends 21, 23 of the inner body 20. The second aperture 24 is located at the second end 23 of the inner body 20. In the open position, the aperture 22 is fluidically connected to the inlet 12 and the outlet 14. In the regulated position, the aperture 22 remains fluidically connected to the outlet 14 but flow of hydraulic fluid through the inlet 12 is inhibited relative to the open position.

When the regulated position is a closed position of the regulator valve 1, the inlet 12 and outlet 14 are fluidically disconnected. In the closed position, the inlet 12 is fully blocked. That is, in the closed position, the first 104, 106 and second 102 sections of the circuit 5, as shown in Figure 1, are fluidically disconnected.

The internal passage 6 of the inner body 20 provides access to the expansion chamber 7. Hydraulic fluid is configured to flow between the intermediate chamber 3 and expansion chamber 7 by passing through the first and second apertures 22, 24 of the internal passage 6. The internal passage 6 therefore comprises a channel to transport hydraulic fluid to and away from the expansion chamber 7. In the example shown, the internal passage 6 is the only link between the intermediate chamber 3 and the expansion chamber 7 because tolerances between the inner body 20 and outer body 10 are to prevent passage of hydraulic fluid past the first shoulder portion 19 of the inner body 20.

The first aperture 22 of the internal passage 6 comprises two diametrically opposed openings. In some examples, the first aperture 22 may comprise a single opening. The second aperture 24, in this example, comprises a single opening, although in some examples, the second aperture 24 may comprise a plurality of openings. The first and second apertures 22, 24 are orthogonal to each other. The first aperture 22 is radial to the longitudinal axis A-A of the regulator valve 1, whereas the second aperture 24 is coaxial with the longitudinal axis A-A. An area of the first aperture 22 is double the area of the second aperture 24. In the example provided, this increased area of the first aperture 22 is because the first aperture 22 comprises two openings, each of equal size to the single opening of the second aperture 24. In other examples, the area of the first aperture 22 may be equal to the area of the second aperture 24. The regulator valve 1 comprises a reserve chamber 8 that is an annular space formed when the regulator valve 1 in arranged in the open position. The reserve chamber 8 is to balance the position of the outer body 20 relative to the inner body 10. The reserve chamber 8 is to collect hydraulic fluid so that relative movement of the inner and outer bodies 20, 10 is less resistant and results in less wear of the engaging parts. In the regulated and closed positions, the expansion chamber 7 comprises the annular space, as shown in Figure 7. The reserve chamber 8 is formed by a widening of the bore 17 and is not configured to directly abut the inner body 20. The reserve chamber 8 has a length, in the longitudinal axis A-A direction, that is less than the length of the second head portion 28 of the inner body 20, in the same direction. The length of the reserve chamber 8 is less than half of the length of the second head portion 28.

In use, hydraulic fluid is pressurised by a source, such as a pump. In this example, the pump is an engine oil pump. The hydraulic fluid is supplied under pressure from the pressurised source to the first section 104, 106. The hydraulic fluid fills the second bore portion 17b and is fluidically connected between the inlet 12 and outlet 14 of the regulator valve 1 to fluidically connect the first section 104, 106 and the second section 102. The increase in hydraulic fluid pressure in the expansion chamber 7 causes the expansion chamber 7 to expand by relative movement of the inner body 20 and outer body 10. As the expansion chamber 7 expands, the inner body 20 slides along the inner wall of the outer body. The outer body 10 is constrained in the circuit 5 and does not move. The force exerted on the inner body 20, by the hydraulic fluid pressure, must exceed the force of the spring 30 in order to cause the spring 30 to compress. If the hydraulic pressure is high enough, the regulator valve 1 will move towards a closed position, as shown in Figure 7, wherein the second head portion 28 of the inner body 20 completely closes over the inlet 12. In this state, the first section 104, 106 and the second section 102 of the circuit 5 are fluidically disconnected. Prior to closure of the inlet 12, the regulator valve 1 is arranged in a regulated position, whereby the flow of hydraulic fluid from the second section 102 to the first section 104, 106 is inhibited relative to the open position. In the regulated position, hydraulic fluid may flow between the second section 102 and first section 104, 106 but the flow is restricted compared to when the regulator valve 1 is arranged in the open position.

The inhibiting of hydraulic fluid in the regulated position is to prevent hydraulic fluid pressure or hydraulic fluid flow rate in the first section 104, 106 exceeding a first pre-determined value, for example a pressure between 1.5bar and 2bar. The first pre determined value, in this example, is selected so that the regulator valve 1 is configured to inhibit pump-up of the HLAs 200. If the hydraulic fluid pressure or flow rate in the regulator valve 1 reaches the first pre-determined value, the regulator valve 1 is configured to respond by fluidically disconnecting the first section 104, 106 from the second section 102.

When the regulator valve 1 has fluidically disconnected the first section 104, 106 from the second section 102, the regulator valve 1 is configured to fluidically reconnect the first section 104, 106 to the second section 102 in response to the hydraulic fluid pressure or flow rate in the regulator valve 1 reducing below a second pre-determined value. In some examples, the first pre-determined value is substantially the same as the second pre-determined value.

The regulator valve 1 is switchable between fluidically reconnecting the first section 104, 106 to the second section 102 and fluidically disconnecting the first section 104, 106 from the second section 102 to maintain a substantially constant hydraulic fluid pressure or flow rate in the first section 104, 106. That is, the circuit 5 is arranged for intermittent connection of the first 104, 106 and second 102 sections by continual fluctuation of the regulator valve 1 between fluidically connecting and disconnecting the first 104, 106 and second 102 sections. In other words, the regulator valve 1 automatically regulates the flow of hydraulic fluid from the second section 102 to the first section 104, 106 by action of the hydraulic fluid on the regulator valve 1. The inner body 20 is cyclically movable relative to the outer body 10 between the open and closed positions to maintain a substantially constant hydraulic fluid pressure or flow rate in the first section 104, 106. The substantially constant hydraulic fluid pressure may be between 1.5bar and 2bar.

Figures 8 and 9 respectively show hydraulic fluid pressures and flow rates of the circuit 5 with and without a regulator valve 1. Examples for different hydraulic fluid temperatures are also shown. The data was collected using 5W-30 oil as the hydraulic fluid.

As shown in Figure 8, when no regulator valve 1 is used, as shown by pressure line 300, the first pressure PI in the first section 104, 106 of the circuit 5 is proportional to the second pressure P2 in the second section 102 of the circuit 5. When the hydraulic fluid pressure in the first section 104, 106 exceeds 2bar, the FILAs 200 can become over-pressurised and lead to damage of the FILAs 200 or unwanted opening of the valve 211. A circuit 5 without the regulator valve 1 is therefore at risk of operating at pressures which are undesirably high and the FDLAs 200 can suffer from pump-up. When a regulator valve 1 is used, the first pressure PI in the first section 104,

106 of the circuit 5 is limited. Therefore, the first pressure PI has a maximum value regardless of the value of the second pressure P2 in the second section 102 of the circuit 5. This maximum value is also shown to be regardless of hydraulic fluid temperature when in the range 30degC to lOOdegC, as shown by pressure lines 330 (30degC), 360 (60degC), and 390 (lOOdegC). The maximum pressure of the first pressure PI is equal to the first pre-determined hydraulic pressure value, which is between 1.5bar and 2b ar in this example.

As shown in Figure 9, when no regulator valve 1 is used, as shown by flow rate lines 430’ (30degC), 460’ (60degC), and 490’ (lOOdegC), the first flow rate Q1 in the first section 104, 106 of the circuit 5 is substantially proportional to the second flow rate Q2 in the second section 102 of the circuit 5. When the hydraulic fluid pressure in the second section 102 exceeds 2bar, the HLAs 200 can become over-pressurised and lead to damage of the HLAs 200 or unwanted opening of the valve 211. A circuit 5 without the regulator valve 1 is therefore at risk of operating at pressures which are undesirably high and the HLAs 200 can suffer from pump-up.

When a regulator valve 1 is used, the first flow rate Q1 in the first section 104, 106 of the circuit 5 is limited but may vary depending on temperature of the hydraulic fluid. Therefore, the first flow rate Q1 has a maximum value for each temperature regardless of the value of the second pressure P2 in the second section 102 of the circuit 5. When the hydraulic fluid is at a temperature of 30degC, the maximum first flow rate Q1 is between 1 and 1.5 litres per minute even when the second pressure P2 is above 2b ar as shown by flow rate line 430. When the hydraulic fluid is at a temperature of 60degC, the maximum first flow rate Q1 is between 2 and 2.5 litres per minute even when the second pressure P2 is above 2b ar as shown by flow rate line 460. When the hydraulic fluid is at a temperature of lOOdegC, the maximum first flow rate Q1 is between 2.5 and 3 litres per minute even when the second pressure P2 is above 2.5bar as shown by flow rate line 490.

Advantageously, the regulator valve 1 , and the circuit 5 comprising the regulator valve 1, allows the risk of pump-up of the HLAs 200 to be reduced or avoided entirely. The HLAs 200 are therefore not exposed to excessive pressures or unbalanced pressure, which can both separately lead to damage of the HLAs 200 or unwanted opening of the valve 211. Further, a smaller pump can be used to provide the pressurised source of hydraulic fluid because energy losses are minimised.

The regulator valve 1 allows for excess hydraulic fluid to be distributed away from the regulator valve 1 when not needed. This helps with the management of the hydraulic fluid in the circuit 5.

In an engine application, the pump is proportional to the engine speed and so a flow of hydraulic fluid increases with engine speed. The benefit of the regulator valve 1 is that the pressure supplied to the HLAs never exceeds a first pre-determined value regardless of the speed of the engine. This helps to provide a more robust system comprising the regulator valve 1 than a system without the regulator valve 1.

It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. It is also understood that the regulator valve 1 as described herein is not limited to an engine application and can be applied to any hydraulic fluid application.

Reference Signs List

1 regulator valve

2 inlet direction

3, 7, 8, 228, 232 chamber

4 outlet direction

5 hydraulic fluid supply circuit

6 internal passage 10 outer body

10a, 27 neck portion 10b, 20a end portion 11, 21, 208 first end 12 inlet

13, 23, 212 second end 13a, 25, 29 ramped portion 14 outlet

15, 45 end stop 17 bore

17a, 17b bore portion 18, 19 shoulder portion 20 inner body

22, 24, 230 aperture 26, 28 head portion

30, 238, 240 spring 40 seat 50 circlip 60 biasing arrangement 100 engine sub-assembly 102 second section

104, 106 first section 110 housing 200 Hydraulic Lash Adjuster (HLA) 201, 201’, 201” rocker arm assembly 202 valve train assembly

204, 204’, 204” rocker arm 210 valve stem

211, 21 G valve

214 roller

215 camshaft

216 axle

217 lobe

218 cam 219 base circle 222 cylindrical body

224, 252 bore

226 plunger assembly

234 ball

236 cage

242 outer end

244 outer surface

246 outer part

248 inner part

250 stem

254 enlarged head

256 clip

258 groove

260 spring washer

A-A longitudinal axis

PI, P2 pressure of the hydraulic fluid

300, 330, 360, 390 pressure line

Ql, Q2 flow rate of the hydraulic

430, 430’, 460, 460’, 490, 490’ flow rate line