GB2567036A

GB2567036A - Solenoid valve

Info

Publication number: GB2567036A
Application number: GB1811715.0A
Authority: GB
Inventors: Bhuvaneshwari Tarun; Chudasama Amit
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-09-29
Filing date: 2018-07-18
Publication date: 2019-04-03
Anticipated expiration: 2038-07-18
Also published as: GB2567036B; DE102018214616A1; GB201811715D0; GB201715783D0

Abstract

A solenoid valve 30 having an inlet 37, an outlet 38 and a pintle 36 that is movable between a first, partially open position and a second fully open position which provides a larger gap for fluid to flow through. The pintle may adopt the first position when the solenoid is energised, and the second position when the solenoid is de-energised. The solenoid valve may have a housing and the pintle may have a magnetic core that has a first surface, and a shaft that extends through a bore in the housing whilst the housing has a second surface which surrounds an entrance to the bore and an inhibitor that restricts movement of the pintle towards the valve seat. The inhibitor can be formed by a circumferential groove in the wall of the bore and a resiliently biased ball or pin, or an arrangement of a stop and projection.

Description

FIG. 4D

SOLENOID VALVE

TECHNICAL FIELD

The present disclosure relates to a solenoid valve. Aspects of the invention relate to a solenoid valve, to an internal combustion engine comprising the solenoid valve, to a vehicle comprising the internal combustion engine and/or solenoid valve, to a controller for controlling the solenoid valve, and to a method of operating the solenoid valve.

BACKGROUND

Internal combustion engines use pistons, which may be formed, for example, of aluminium, to convert the combustion of fuel into mechanical work. In a conventional lubrication circuit for an internal combustion engine, an electronic pump provides a flow of oil from a reservoir to the engine. A piston cooling jet (PCJ) acts to direct, spray or squirt oil on to (the inside of) a piston of the engine during operation so as to cool the piston and therefore maintain a predetermined operating temperature. The flow of oil to the PCJ from the reservoir and pump is controlled by a solenoid valve. The solenoid valve has two positions: energised (closed), in which the flow of oil supplied to the PCJ is zero, and de-energised (open), in which the flow of oil supplied to the PCJ is 100% of the available flow being provided to the PCJs via the oil gallery by the oil pump. The position of the valve is controlled in dependence on the monitored temperature of the piston based on the engine speed and load.

The solenoid valve is an electromechanical valve which is controlled by passing an electric current through the solenoid. This generates a magnetic field which interacts with a pintle (elongate member, plunger or pin) which is mounted within a guide. The application of the magnetic field causes the pintle to move linearly within the guide from an open position (when the solenoid is de-energised (no electric current passing)) and a closed position (when the solenoid is energised (electric current passing)). In the open position, the position of the pintle within the guide allows the flow of oil through the valve (from an inlet to an outlet), while in the closed position, the position of the pintle prevents the flow of oil through the valve.

An existing solenoid valve is controlled using a complete ON/OFF (100% duty cycle) pulse width modulation (PWM) control method. Here, the solenoid only operates under 2 conditions: fully open when de-energised (to permit the passage through the valve of oil) and fully closed when energised (to prevent the passage through the valve of oil). As a result, while the valve is open, engine oil is being directed to the pistons, and while the valve is closed, oil is not being directed to the pistons.

There may be a particular requirement, for example when using steel pistons, to have engine oil from the piston cooling jets provided via the solenoid valve to the inside of the pistons under all operating conditions and loads (that is, at all times while the engine is running), to ensure adequate piston cooling, albeit at different (non-zero) rates under different conditions. However, utilising the above described solenoid valve configuration, and either allowing the piston cooling jet solenoid to always be in the fully ON position or removing it altogether would require the use of an oil pump which is 92% larger in size than an existing oil pump used with the above solenoid valve and 19% larger in size than desirable for the intended engine configuration. In particular, such an oil pump would be impossible, or at least very challenging, to package into the engine. Further, there would be a potential penalty on fuel economy and increase in emissions because the oil pump is mechanically driven from the engine crankshaft via a belt. In order to ensure adequate oil supply to meet engine requirements (inclusive of piston cooling jets), the oil pump will have to work harder, meaning an increase in load of the engine (parasitic losses), which in turn reduces fuel economy and increases emissions as more fuel is burnt to compensate. Finally, there would be a reduction in oil pump durability due to higher oil flow requirements compared with the existing pump.

Another option would be to implement the variable oil flow rates by controlling the PCJ solenoid using different PWM duty cycles (for example off (0%), 25% on, 50% on and 100% on, rather than just off or 100% on). However, using this technique would preclude use of the existing solenoid valve as it would have durability and robustness issues, thus requiring a new PWM controlled and fully variable flow PCJ solenoid with larger dimensions and higher cost. Moreover, a larger PWM solenoid is not readily feasible with the intended engine configuration due to a lack of physical package space on the engine and a lack of flexibility in changing the cylinder block.

In US9022069, a pressure balanced solenoid operated valve includes a dedicated bleed port created in the body separately from a main inlet port, which opens into a flow path for a pressurized fluid for use when the valve is in the valve closed position, to continuously flow out through the valve outlet port.

It is an object of embodiments of the invention to at least mitigate one or more of the problems of the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a solenoid valve, internal combustion engine, vehicle, controller, a method and computer software as claimed in the appended claims.

According to an aspect of the invention, there is provided a solenoid valve, comprising:

an inlet;

an outlet; and a pintle, constrained to move between a first position and a second position, whereby in the first position the pintle allows a partial flow of fluid from the inlet through a gap provided between the pintle and a valve seat to the outlet, and in the second position the pintle allows a full flow of fluid from the inlet through a larger gap provided between the pintle and the valve seat to the outlet.

In this way, at least a partial flow of fluid is permitted by the pintle at all operating positions of the pintle. While it will be appreciated that a solenoid valve could be provided in which three or more static operating positions of the pintle are used to achieve three or more (non-zero) flow rates, preferably, only two operating positions (that is, positions at which the pintle is substantially static rather than moving between the first and second positions) are provided, corresponding to the first and second positions. In other words, the solenoid valve may be configured such that the pintle is only able to remain substantially static at the first position and the second position. Such a valve, not being fully variable, can be controlled simply using a pulse width modulation (on/off) technique in a similar to the prior art valves described above.

The partial flow of fluid and the full flow of fluid may follow the same flow path from the inlet to the outlet. In other words, fluid follows the same flow path from the inlet of the solenoid valve to the outlet of the solenoid valve when the pintle is in both the first and second positions. This provides the advantage that the same inlet and outlet of the valve provides both the partial flow and the full flow of fluid without the need for an additional inlet and/or outlet of the valve.

In the solenoid valve, which comprises a solenoid, preferably the pintle adopts one of the first and second positions when the solenoid is energised and the other of the first and second positions when the solenoid is de-energised. More preferably, the pintle adopts the first position when the solenoid is energised and the second position when the solenoid is de-energised. Accordingly, in the event of a power failure or electrical fault which prevents the solenoid being energised, the valve will adopt the open position to ensure that cooling occurs.

The present technique is applicable irrespective of the specific mechanical structure, dimensions and shape of the valve. However, in one example, the pintle is movable towards a valve seat, within which the outlet is optionally formed, to reduce the flow rate from the inlet to the outlet, and a gap is provided between the pintle and the valve seat when the pintle is in the first position. As a result, even when the pintle is extended to its maximum extent towards the valve seat, a gap is still provided to enable a partial flow of fluid.

Preferably, the pintle partially blocks the inlet when it is in the first position.

The partial flow may be within the range of 1% and 99% of a flow rate provided by the full flow, more preferably within the range of 10% and 90% of the full flow rate, and still more preferably within the range of 25% and 60% of the full flow rate. More preferably, the partial flow is approximately 40% of the flow rate provided by the full flow.

The partial flow may be approximately 10 litres per minute and the full flow may be approximately 25 litres per minute

A solenoid valve of the type described herein may be beneficial and applicable for various purposes, both within and outside of the automotive field. However, the solenoid valve is particularly applicable for controlling a flow of engine oil to a piston cooling jet of an internal combustion engine.

In one embodiment, the solenoid valve comprises a housing, the pintle comprises a magnetic core having a first surface, and a shaft which projects from the first surface and extends through a bore in the housing, the housing comprises a second surface which surrounds an entrance to the bore through which the shaft passes, and which faces the first surface of the magnetic core, and the solenoid valve comprises an inhibitor for restricting the movement of the pintle in a direction towards the valve seat such that an air gap is preserved around the shaft and between the first surface and the second surface when the pintle is in the first position, the air gap being completely or substantially unoccupied when preserved.

The inhibitor may be any structure, or combination of separate structures, which restricts movement of the pintle in a direction towards the valve seat.

In another embodiment, the solenoid valve comprises a housing, the pintle comprises a magnetic core having a first surface, the housing comprising a second surface which faces the first surface, an air gap being defined between the first surface and the second surface, and the solenoid valve comprises two or more inhibiting elements which interact with each other outside the air gap to maintain the air gap by inhibiting or preventing the pintle from moving beyond the first position towards the valve seat.

In another embodiment, the solenoid valve comprises a housing, the pintle extending through a bore in the housing towards the valve seat, wherein the housing comprises one or more first inhibiting elements and the pintle comprises one or more second inhibiting elements, the first and second inhibiting elements interacting inside the bore when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position towards the valve seat.

It should be understood that the terminology “at or near” does not necessarily require the inhibiting elements to provide a hard stop at the first position, but may instead provide a soft stop, whereby they start to resist further motion of the pintle before the pintle reaches the first position. In other words, the inhibiting elements interact when the pintle is in the vicinity of the first position, in some embodiments interacting in advance of the first position in order to bring the pintle to a stop smoothly at the first position, and in other embodiments interacting only when the pintle actually reaches the first position.

In another embodiment, the solenoid valve comprises a housing, the pintle extending through a bore in the housing towards the valve seat, the bore comprising a first opening distal from the valve seat and a second opening proximate the valve seat, the pintle comprising a piston portion extending between the second opening and the valve seat. The second opening is closer to the valve seat than the first opening. In other words, the second opening is located between the first opening and the valve seat. The housing comprises one or more first inhibiting elements and the piston comprises one or more second inhibiting elements, the first and second inhibiting elements interacting when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position towards the valve seat.

In another embodiment, the solenoid valve comprises a housing, the pintle comprises a magnetic core having a first surface, and a shaft which projects from the first surface and extends through a bore in the housing, the housing comprises a second surface which surrounds an entrance to the bore through which the shaft passes, and which faces the first surface of the magnetic core, wherein the housing comprises one or more first inhibiting elements and the shaft comprises one or more second inhibiting elements, the first and second inhibiting elements interacting when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position towards the valve seat.

The inhibiting elements may comprise one or more pairs of interengaging structures. The first inhibiting element may comprise a circumferential groove in the wall of the bore and the second inhibiting element may comprise a resiliently biased ball or pin for engaging the circumferential groove. It will be appreciated that a reverse arrangement could be provided, in which the groove is provided in the shaft and the ball or pin is provided in wall of the bore.

The groove may be shaped so that a force required to move the ball or pin out of the groove when the pintle is moved in a direction away from the valve seat is less than a force required to move the ball or pin out of the groove when the pintle is moved in a direction towards the valve seat.

A force applied to move the pintle from the first position towards the second position may be less than the force applied to move the pintle from the second position towards the first position.

The first inhibiting element may comprise a stop or wall, and the second inhibiting element may comprise a projection which is inhibited from moving past the stop.

According to another aspect of the invention, there is provided a controller for configuring the pintle of the solenoid valve to adopt either the first position or the second position.

According to another aspect of the invention, there is provided a method of controlling a solenoid valve having an inlet, an outlet, a solenoid, and a pintle, the pintle being constrained to move between a first position in which the pintle allows a partial flow of fluid from the inlet to the outlet and a second position in which the pintle allows a full flow of fluid from the inlet to the outlet, the method comprising energising and/or de-energising the solenoid to cause the pintle to move between the first position and the second position to control the flow rate permitted through the valve.

According to an aspect of the invention, there is provided computer software which, when executed by a computer, is arranged to perform a method according to an aspect of the invention.

The computer software is optionally stored on a computer-readable medium. The computer software may be tangibly stored on a computer-readable medium. The computer readable medium may be non-transitory.

It will be appreciated that embodiments of the present invention provide a constant bleed piston cooling jet (PCJ) solenoid valve which uses a shorter plunger (pintle), and thus does not fully close off the flow of cooling fluid through the valve even when the valve is closed to its maximum extent. This makes it possible to avoid increasing the size of an existing completely ON/OFF solenoid valve, and to avoid modifying the mounting interface onto the cylinder block in order to achieve a constant/continuous flow of engine oil from the oil filter housing to the piston cooling jets under all engine operating loads and conditions.

Unlike US9022069, which provides a different form of constant bleed solenoid valve, the constant bleed in the present invention is achieved by regulating the flow of fluid between the inlet and the outlet, rather than by achieving a bleed flow in the closed position using a dedicated bleed port in the valve body defining a separate channel from the main fluid flow path.

The main differences and advantages of the present technique are:

(a) No need for a constant bleed port/bypass port to achieve a constant bleed PCJ solenoid;

(b) Similar package space and dimensions as normally required for a fully ON/OFF solenoid valve;

(c) Reduced cost and complexity of design and manufacturing;

(d) No need for larger oil pumps on the engine in order to achieve/maintain the required oil pressures at the Piston Cooling Jets (PCJs) to squirt and cool the pistons; and (e) No modifications required to engine cylinder block mounting interface for the new constant bleed solenoid valve with shorter plunger/pusher.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Figures 1A and 1B show a schematic representation of a solenoid valve and piston cooling jets located within an internal combustion engine;

Figure 2 shows a schematic representation of a conventional (prior art) solenoid valve in a fully closed position;

Figures 3A and 3B show a schematic representation of the modified solenoid valve in both partially open (Figure 3A) and fully open (Figure 3B) positions; and

Figures 4A to 4D show schematic representations of other modified solenoid valves.

DETAILED DESCRIPTION

Referring to Figure 1A, a solenoid valve 10 is shown within an internal combustion engine setting, and in particular is shown proximate an engine block 12. The solenoid valve 10 regulates (controls) the flow rate of engine oil from an inlet oil gallery 14 to an outlet oil gallery 16. In particular, the flow of oil proceeds from an oil pump (not shown) to an oil filter housing (not shown), to the inlet oil gallery 14, and to the outlet oil gallery 16 via the solenoid valve 10, and then from the outlet oil gallery (PCJ Gallery) 16 to PCJ’s (as explained in Figure 1B below).

Referring to Figure 1B, an alternative view of the solenoid valve 10 within the engine setting is shown, in which a piston 11 is visible. Piston cooling jets 18 are disposed proximate the piston 11, for directing the engine oil to the piston 11. The piston cooling jets 18 are in fluid communication with the outlet oil gallery 16, such that oil driven through the solenoid valve and into the outlet oil gallery 16 is forced through the piston cooling jets 18 and into or onto the piston 11.

It will be appreciated from Figures 1A and 1B that there are significant space constraints within the engine, making it undesirable to adopt a form of solenoid valve which is larger than currently used.

Referring to Figure 2, a conventional solenoid valve 20 is shown in a closed position, in which substantially no flow of fluid is permitted through the valve 20. The valve 20 comprises a housing 22, a solenoid 24, a pintle 26, an inlet 27 and an outlet 28. The block arrow in Figure 2 indicates the direction of fluid flow into the inlet 27 of the valve 20. In use, to close the valve 20, an electric current is passed through the solenoid 24, which generates an electric field, which in turn interacts with the metal pintle 26 to move the pintle 26 with respect to the solenoid 24. More specifically, when the solenoid 24 is energised, the pintle 26 is driven (to the right, in Figure 2) to adopt the closed position shown in which it abuts a valve seat within which the outlet 28 is formed. This blocks the fluid flow path between the inlet 27 and outlet 28, substantially preventing fluid from flowing and thus resulting in a zero flow rate. When the electrical current to the solenoid 24 is switched off (the solenoid is deenergised), the magnetic field collapses and the pintle 26 returns to a rest position (to the left, in Figure 2 - rest position not shown) in which the fluid flow path between the inlet 27 and outlet 28 is unobstructed. A biasing means, for example a spring or other resiliently deformable element, (not shown) may be provided, in order to bias the pintle 26 into the open position in the absence of the solenoid 24 being energised.

Now referring to Figures 3A and 3B, a modified valve 30 is shown, in which fluid is permitted to pass through the valve 30 in both of two static states of the valve 30. The valve 30 is similar in structure to the valve 20, with an important difference as will be described below. The valve 30 comprises a housing 32, a solenoid 34, a pintle 36, an inlet 37 and an outlet 38. Part of an interior of the housing 32 forms a chamber and fluid flow path between the inlet 37 and the outlet 38. Another part of the interior of the housing 32 forms a guide within which the pintle is constrained to move linearly and reciprocally between two extreme positions. The pintle 36 has a first part 36a having a (relatively large) substantially cylindrical cross section which is surrounded (in both states) by the solenoid 34. It is this first part 36a of the pintle 36 with which the magnetic field generated by the solenoid 34 principally interacts. The pintle 36 may have a second part 36b having a (relatively small) substantially cylindrical cross section which has a leading end 36c. The outlet 38 is formed in a valve seat towards which the pintle 36 is able to travel to control the fluid flow rate through the valve 30. The block arrow in each of Figures 3A and 3B indicates the direction of fluid flow into the inlet 37 of the valve 30. In Figure 3A, the valve 30 is shown in a first state. In the first state, the pintle 36 is in a first (partially open) position in which the flow of fluid from the inlet 37 to the outlet 38 is restricted (partially obstructed, but not blocked entirely). In the second state, the pintle 36 is in a second (fully open) position in which the flow of fluid from the inlet 37 to the outlet 38 is substantially uninhibited. It will be appreciated that the actual flow rate will be function also of the geometry of the flow path between the oil reservoir and the piston cooling jets, and of the pump pressure.

A fluid flow path exists from an inlet to an outlet of the valve. The position of the pintle within the valve housing (guide) controls an extent to which this fluid flow path is obstructed. Constant bleed is therefore provided by way of the fluid flow path. No additional fluid flow path is required when the pintle is in the “closed” position, since a restricted flow is provided via the fluid flow path.

It can be seen from a comparison of Figures 3A and 3B that the pintle 36 moves rightwardly (in the Figure) towards the valve seat to adopt the first state (from the second state), and moves leftwardly (in the Figure) away from the valve seat to adopt the second state (from the first state). More specifically, and in analogous manner to Figure 2, in use, to restrict the flow rate through the valve 30, an electric current is passed through the solenoid 34, which generates an electric field, which in turn interacts with the metal pintle 36 to move the pintle 36 with respect to the solenoid 34. More specifically, when the solenoid 34 is energised, the pintle 36 is driven (to the right, in Figures 3A and 3B) to adopt the closed position shown in Figure 3A in which its leading edge 36c is relatively proximate to a valve seat within which the outlet 38 is formed. It can be seen that the side of the pintle 36 proximate the leading end 36c partially covers the inlet 37, thereby obstructing the fluid flow. It will be understood that in a different arrangement the pintle might partially cover an outlet.

In Figure 3A, it can be seen that the pintle 36, being shortened with respect to the pintle 26 of Figure 2, does not reach or abut with the valve seat when it is in the first position. This means that there is a gap, opening, or channel through which fluid is able to flow from the inlet 37 to the outlet 38 even when the valve 30 is in its most closed (first) state. The gap, opening, or channel is however larger when the valve 30 is in its most open (second) state, allowing a greater fluid flow rate. It should be understood that this is only one possible geometry for implementing the invention. In alternative embodiments, part of the pintle 36 may abut the valve seat, but be shaped to leave a partially open channel to the outlet 38. In still other embodiments, more complex inlet and/or outlet geometries and/or pintle shapes may be used, but still operating according to the premise that the pintle 36 (potentially via an intermediate component) allows a partial flow of fluid from the inlet to the outlet in a first position, and in which the pintle allows a full flow of fluid from the inlet to the outlet in a second position. In the present embodiment, in adopting the first position, the pintle 36 partially obstructs the fluid flow path between the inlet 37 and outlet 38, reducing the flow rate through the valve 30 compared with when the pintle 36 is in the second position. When the electrical current to the solenoid 34 is switched off (the solenoid is de-energised), the magnetic field collapses and the pintle 36 returns to a rest position (to the left, in Figure 3B) in which the fluid flow path between the inlet 27 and outlet 38 is unobstructed. A biasing means (not shown) may be provided, in order to bias the pintle 36 into the open position in the absence of the solenoid 34 being energised.

It will be appreciated that the two states of the valve 30 are distinguished by the different fluid flow rates through the valve 30 which they respectively permit. Unlike the valve 20 of Figure 2, with the valve 30 of Figures 3A and 3B the fluid flow rate is non-zero for both states. The valve 30 does not have a fully closed state.

If full flow is 100% of the available flow rate (dictated by the pump pressure and the geometries of the flow paths from the oil reservoir and the PCJs), partial flow can range anywhere between 1% and 99%. The partial flow parameter, is fully flexible, although fixed for a particular application. In practical terms, the partial flow rate for the automotive industry is preferably in the range of 10% and 90%, more preferably between 25% and 60%, and still more preferably approximately 40% of the full flow rate.

For example, the full flow rate may be approximately 25 litres per minute (more specifically, 25.5 litres per minute in the proposed implementation), while the partial flow rate may be approximately 10 litres per minute (more specifically, 10.5 litres per minute in the proposed implementation).

The operation of the valve 30 may be controlled by a controller (not shown), for example a microcomputer forming part of the control system of the engine and/or vehicle. The controller causes the solenoid 34 to be energised and de-energised, as described above, to achieve a desired flow rate with respect to time. A pulse width modulated control signal may be used to switch between low and high flow rates associated respectively with the first and second states of the valve 30. The control signal may be generated in dependence on a measured or derived temperature, for example of the pistons, in order that an increase in temperature can be reacted to with an increase in the flow rate through the valve 30.

From the above description, it will be understood that a valve 30 in accordance with an embodiment of the invention will still have only two positions, similar to the prior art, but instead of the energised position providing zero flow, at least a small amount of flow will be allowed past the valve and to the PCJs. In the described embodiment, this is achieved by shortening the pintle of the existing solenoid valve such that in the ‘closed’ position the pintle does not fully abut the valve seat. In other words, one embodiment of the invention is achieved by shortening the pintle of a solenoid valve such that the pintle does not abut the valve seat when the valve is in a fully energised position.

It will be appreciated that, since the pintle does not come into contact with the valve seat, another part of the pintle may come into contact with the housing of the solenoid valve when in a fully energised position. As will be explained in more detail below with reference in Figures 4A to 4D, when modifying an existing solenoid valve to utilise an embodiment of the invention as per Figure 3, this may result in an air gap between a magnetic core of the pintle and the housing being “closed” due to the magnetic core coming into contact with the housing, which may result in the valve “sticking” in the fully energised position. The following embodiments present options for preventing or at least alleviating this problem.

Referring specifically to Figure 4A, a solenoid valve 400 comprises an electromagnet 401 within a solenoid housing 403. The solenoid housing 403 is mounted to and around a valve housing 405. Together, the solenoid housing 403 and valve housing 405 may be considered as a single housing. Within the valve housing 403 is mounted a pintle, comprising a magnetic mobile core 402, a pusher (or shaft) 409 and a piston 410. The piston 410 defines the shaped terminus of the pintle, for partially closing off the flow of fluid through the valve 400 in the direction of arrows 415 by way of its proximity to a valve seat housing 411, which houses a valve seat 404, when the electromagnet 401 is energised. The valve housing 405 and the valve seat housing 411 may be considered as a single housing. The pusher 409 is a shaft which extends between the magnetic mobile core 402 and the piston 410. A mounting plate 408 is used to mount the solenoid onto the engine cylinder block. The magnetic mobile core 402 and the electromagnet 401 are positioned with respect to each other such that the magnetic mobile core 402 is generally surrounded by the electromagnet 401. As a result, when the electromagnet 401 is energised, the resulting electromagnetic field interacts with the magnetic mobile core 402 to drive the magnetic mobile core 402 (and thus the pusher 409 and piston 410) towards the valve seat housing 411. The valve 400 may be considered to comprise two chambers - a first chamber within which is disposed the magnetic mobile core 402, and a second chamber within which is disposed the piston 410 and the valve seat housing 411, and through which the fluid flows. Parts of the pintle are therefore present in both chambers, with the shaft 409 extending through a bore in the housing which joins the two chambers. As with Figure 3, even in the fully energised position, the piston 410 (terminal end of the pintle) does not come into contact with the valve seat housing 411, but instead a small gap is preserved to enable partial flow through the valve 400. A spring 406 biases the pintle away from the valve seat housing 411 when the electromagnet 401 is not energised.

It can be seen from Figure 4A that an air gap 414 is provided between the magnetic mobile core 402 and the interior of the valve housing 405. This air gap 414 is preserved in both the “open” and “partially open” positions of the valve 400 - that is, both when the electromagnet 401 is energised and when it is not energised. In order to achieve this, in Figure 4A a groove 413 is provided in the valve housing 405 in a region about, and surrounding, the pusher 409. Resiliently biased balls or pins 412 are provided on the shaft 409. A single ball or pin may be provided, or more preferably plural balls or pins (in Figure 4A, two are shown, but it will be appreciated that a larger number could be provided). It will be appreciated that, should the pintle be mounted in a manner which prohibits rotation about its longitudinal axis, a groove need not be provided. Instead, a recess having a similar shape to the protruding portion of the ball or pin may be provided at a circumferential position which is aligned with the ball or pin. A recess may be provided for each ball or pin, in alignment therewith. The ball or pin is movable between a retracted position in which it is received inside the shaft and is substantially flush with the surrounding surface of the shaft, and a protruding position in which it extends outwardly from the shaft. The recess or groove, and the balls or pins, are longitudinally positioned such that they are in engagement with each other when the pintle is in the first position.

The ball/pin and groove/recess are examples of first and second inhibitor elements for inhibiting or preventing the pintle from moving past the first position. It will be appreciated that the first inhibitor elements are part of and/or in longitudinally fixed relationship with the pintle and the second inhibitor elements are part of and/or in longitudinally fixed relationship with the housing (of which the bore is a part).

Generally, the embodiment of Figure 4A provides a solenoid valve in which the pintle comprises a magnetic core having a first surface, and a shaft which projects from the first surface and extends through a bore in the housing. The housing comprises a second surface which surrounds an entrance to the bore through which the shaft passes, and which faces the first surface of the magnetic core. The region between the first and second surfaces, and surrounding the shaft, is an air gap. The air gap is preserved when the pintle is in the first position, in a manner in which the air gap around the shaft and between the first and second surfaces is completely or substantially unoccupied. In order that the air gap be unoccupied, the solenoid valve comprises one or more inhibiting elements which interact with each other outside the air gap to inhibit or prevent the pintle from moving beyond the first position. For example, the inhibiting elements may be one or more first inhibiting elements which are part of the housing (for example an internal surface of the bore) and the one or more second inhibiting elements which are part of the pintle. The first and second inhibiting elements interact inside the bore when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position.

In Figure 4A, the inhibiting elements are pairs of inter-engaging structures, in particular, each pair comprising a ball (or pin) and a recess or portion of groove. It will be understood from Figure 4A that a net force Ni acting on the pintle in a direction towards the valve seat, when the solenoid is energised, is the force E resulting from the electromagnetic interaction between the solenoid and the core, minus the force S applied by the spring 406. That is, Ni = E + S. In contrast, a net force N₂ acting on the pintle in a direction away from the valve seat, when the solenoid is not energised, is simply the force S. That is, N₂ = S. In order that the ball or pin of the shaft is caused to climb out of the groove and be retracted back into the shaft, a threshold force of at least N_t is required to be applied to the pintle in either a direction towards or away from the valve seat. Preferably, the force Ni applied to move the pintle from the second position towards the first position is less than the force N₂ applied to move the pintle from the first position towards the second position. In particular, Ni should be greater than or equal to N_t, whereas N₂ should be less than N_t.

Referring now to Figure 4B, the groove is shaped so that a force required to move the ball or pin out of the groove in a direction away from the valve seat is less than a force required to move the ball or pin out of the groove in a direction towards the valve seat. In Figure 4B, a tapered bore is provided, which increases in diameter from the air gap, and then reduces in diameter at an end wall. The end wall may be considered as a stop, beyond which the ball or pin is inhibited from travelling. It will be appreciated that if the pintle is rotationally constrained, the bore may be tapered in cross section only at circumferential positions which are aligned with the balls or pins in the pintle. While the ball or pin is able to retract into the shaft of the pintle, the force required to cause this to happen in order to move the ball or pin past the end wall of the shaped groove is greater than the force acting on the pintle. In contrast, the shallow slope of the shaped groove as it narrows in the direction towards the air gap results in a lower force being required to gradually retract the ball or pin as it moves along the tapered bore.

Referring to Figure 4C, here a retracting ball or pin is replaced with a fixed projection from the shaft. The bore in this case has a first portion (closest to the valve seat) having a relatively small diameter, similar to the external diameter of the shaft, and a second portion (closest to the air gap) having a relatively large diameter, sufficient to accommodate both the shaft and the projection. As a result, the projection is able to move freely within the second portion, but is unable to enter the first portion. It will be appreciated that the second portion may potentially be provided with a larger diameter than the first portion onto within an area aligned to the projection. In this case, the second portion may be considered as comprising one or more channels extending along the bore, each channel receiving a projection. A step change in diameter as the first portion meets the second portions forms a wall, or stop, beyond which the projection is unable to pass. In the other direction, the pintle is constrained by spring 406 reaching its maximum compression or the piston 410 coming into contact with an interior surface of the valve housing 405.

Referring to Figure 4D, here a pair of inter-engaging structures (in this case a resiliently biased ball in the housing 405 and a groove in the piston 410) are provided outside of the bore (as well as outside of the air gap). Instead, the inter-engaging structures are provided proximate the valve seat, and in particular in the piston and surrounding part of the housing. These work in the same manner as in Figure 4A, although the structures shown in Figures 4B and 4C could be used instead.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The 5 claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

Claims

1. A solenoid valve, comprising:

an inlet;

2. A solenoid valve according to claim 1, wherein the partial flow of fluid and the full flow of fluid follow the same flow path from the inlet to the outlet.

3. A solenoid valve according to claim 1 or claim 2, configured such that the pintle is only able to remain substantially static at the first position and the second position.

4. A solenoid valve according to any preceding claim, comprising a solenoid, wherein the pintle adopts one of the first and second positions when the solenoid is energised and the other of the first and second positions when the solenoid is de-energised.

5. A solenoid valve according to claim 4, wherein the pintle adopts the first position when the solenoid is energised and the second position when the solenoid is deenergised.

6. A solenoid valve according to any preceding claim, wherein the outlet is formed within the valve seat.

7. A solenoid valve according to any preceding claim, wherein the pintle partially blocks the inlet when it is in the first position.

8. A solenoid valve according to any preceding claim, wherein the partial flow is within the range of 1% and 99% of a flow rate provided by the full flow, more preferably within the range of 10% and 90% of the full flow rate, and still more preferably within the range of 25% and 60% of the full flow rate.

9. A solenoid valve according to claim 8, wherein the partial flow is approximately 40% of the flow rate provided by the full flow.

10. A solenoid valve according to claim 8 or claim 9, wherein the partial flow is approximately 10 litres per minute and the full flow is approximately 25 litres per minute.

11. A solenoid valve according to any preceding claim, for controlling a flow of engine oil to a piston cooling jet of an internal combustion engine.

12. A solenoid valve according to any preceding claim, wherein the solenoid valve comprises a housing, the pintle comprises a magnetic core having a first surface, and a shaft which projects from the first surface and extends through a bore in the housing, the housing comprises a second surface which surrounds an entrance to the bore through which the shaft passes, and which faces the first surface of the magnetic core, and an inhibitor for restricting the movement of the pintle in a direction towards the valve seat such that an air gap is preserved around the shaft and between the first surface and the second surface when the pintle is in the first position, the air gap being completely or substantially unoccupied when preserved.

13. A solenoid valve according to any preceding claim, wherein the solenoid valve comprises a housing, the pintle comprises a magnetic core having a first surface, the housing comprising a second surface which faces the first surface, an air gap being defined between the first surface and the second surface, and the solenoid valve comprises two or more inhibiting elements which interact with each other outside the air gap to maintain the air gap by inhibiting or preventing the pintle from moving beyond the first position towards the valve seat.

14. A solenoid valve according to any preceding claim, wherein the solenoid valve comprises a housing, the pintle extending through a bore in the housing towards the valve seat, wherein the housing comprises one or more first inhibiting elements and the pintle comprises one or more second inhibiting elements, the first and second inhibiting elements interacting inside the bore when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position towards the valve seat.

15. A solenoid valve according to any one of claims 1 to 13, wherein the solenoid valve comprises a housing, the pintle extending through a bore in the housing towards the valve seat, the bore comprises a first opening distal from the valve seat and a second opening proximate the valve seat, the pintle comprising a piston portion extending between the second opening and the valve seat;

wherein the housing comprises one or more first inhibiting elements and the piston portion comprises one or more second inhibiting elements, the first and second inhibiting elements interacting when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position towards the valve seat.

16. A solenoid valve according to any one of claims 1 to 13, wherein the solenoid valve comprises a housing, the pintle comprises a magnetic core having a first surface, and a shaft which projects from the first surface and extends through a bore in the housing, the housing comprises a second surface which surrounds an entrance to the bore through which the shaft passes, and which faces the first surface of the magnetic core, wherein the housing comprises one or more first inhibiting elements and the shaft comprises one or more second inhibiting elements, the first and second inhibiting elements interacting when the pintle is at or near the first position to inhibit or prevent the pintle from moving beyond the first position towards the valve seat.

17. A solenoid valve according to any of claims 13 to 16, wherein the inhibiting elements comprise one or more pairs of interengaging structures.

18. A solenoid valve according to claim 14 or claim 16, wherein the first inhibiting element comprises a circumferential groove in the wall of the bore and the second inhibiting element comprises a resiliently biased ball or pin for engaging the circumferential groove.

19. A solenoid valve according to claim 18, wherein the groove is shaped so that a force required to move the ball or pin out of the groove when the pintle is moved in a direction away from the valve seat is less than a force required to move the ball or pin out of the groove when the pintle is moved in a direction towards the valve seat.

20. A solenoid valve according to claim 18, wherein a force applied to move the pintle from the first position towards the second position is less than the force applied to move the pintle from the second position towards the first position.

21. A solenoid valve according to claim 14, wherein the first inhibiting element comprises a stop or wall, and the second inhibiting element comprises a projection which is inhibited from moving past the stop.

22. An internal combustion engine comprising a solenoid valve according to any preceding claim.

23. A vehicle comprising the internal combustion engine of claim 22, or a solenoid valve according to any of claims 1 to 21.

24. A controller for configuring the pintle of the solenoid valve of any one of claims 1 to 21 to adopt either the first position or the second position.

25. A method of controlling a solenoid valve having an inlet, an outlet, a solenoid, and a pintle, the pintle being constrained to move between a first position in which the pintle allows a partial flow of fluid from the inlet to the outlet and a second position in which the pintle allows a full flow of fluid from the inlet to the outlet, the method comprising energising and/or de-energising the solenoid to cause the pintle to move between the first position and the second position to control the flow rate permitted through the valve.

26. Computer software which, when executed by a computer, is arranged to perform a method according to claim 25.