GB2553130A

GB2553130A - Valve assembly with pilot operated recirculation valve

Info

Publication number: GB2553130A
Application number: GB1614459.4A
Authority: GB
Inventors: Shepherd Paul
Original assignee: Concentric Birmingham Ltd
Current assignee: Concentric Birmingham Ltd
Priority date: 2016-08-24
Filing date: 2016-08-24
Publication date: 2018-02-28
Anticipated expiration: 2036-08-24
Also published as: GB2553130B; GB201614459D0

Abstract

A valve assembly for a lubrication system has a recirculation valve 30 which includes a first resilient biasing means 33, such as a spring, which biases the valve to its closed position in which first port 301 is disconnected from second port 302. A control valve 70 controls the force required to move the recirculation valve from the closed position into an open position, against the force of the first resilient biasing means. The control valve has a first position (Figure 1a) in which movement of the recirculation valve against the spring requires a first fluid pressure, and a second position (Figure 1b) in which movement of the recirculation valve against the spring requires a second fluid pressure. The recirculation valve has a first pilot fluid port 51, and the valve moves to its open position if a fluid pressure applied to the first pilot fluid port exceeds a pressure threshold. The valve assembly may further comprise a second resilient biasing means 75, such as a spring, which in use biases the control valve to its first position, and the control valve may comprise a solenoid actuator 77 working against the spring, such that the threshold pressure is further dependent on the force from the solenoid actuator.

Description

(54) Title of the Invention: Valve assembly with pilot operated recirculation valve Abstract Title: Pilot Operated Recirculation Valve Assembly (57) A valve assembly for a lubrication system has a recirculation valve 30 which includes a first resilient biasing means 33, such as a spring, which biases the valve to its closed position in which first port 301 is disconnected from second port 302. A control valve 70 controls the force required to move the recirculation valve from the closed position into an open position, against the force of the first resilient biasing means. The control valve has a first position (Figure 1a) in which movement of the recirculation valve against the spring requires a first fluid pressure, and a second position (Figure 1b) in which movement of the recirculation valve against the spring requires a second fluid pressure. The recirculation valve has a first pilot fluid port 51, and the valve moves to its open position if a fluid pressure applied to the first pilot fluid port exceeds a pressure threshold. The valve assembly may further comprise a second resilient biasing means 75, such as a spring, which in use biases the control valve to its first position, and the control valve may comprise a solenoid actuator 77 working against the spring, such that the threshold pressure is further dependent on the force from the solenoid actuator.

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Valve Assembly With Pilot Operated Recirculation Valve

The present invention relates to a valve assembly. More specifically, the present invention relates to a valve assembly comprising a recirculation valve, for example a recirculation valve for a lubrication system for controlling or regulating oil recirculation in internal combustion engines.

Lubricating oil is circulated through engines in order to reduce friction between moving parts and to remove heat from pistons, bearings and shafts. Oil pumps are known to include valve assemblies comprising a recirculation valve for controlling or regulating the delivery of oil to the main gallery of an engine lubrication system. Such valve assemblies are designed to open the recirculation valve when the pressure of oil in the lubricating system reaches a predetermined value and thus prevent excess oil flow being delivered to the engine main gallery.

One example of a known recirculation valve is a directional control valve having a control chamber, a spring and a spool. When the pressure of the oil in the main gallery exceeds the pressure in the control chamber by more than the compression pressure of the spring, the spool moves beyond the brake edge of the pump, allowing oil to flow from the outlet of the pump to the infet. In this way, excess oil is recirculated and not delivered to the main gallery of the engine lubrication system.

Since such recirculation valves only open at a single, predetermined recirculation pressure, which is controlled by the compression pressure of the spring, it is only possible to regulate the engine oil pressure at a single, predetermined feedback pressure value. This can result in a delivery of oil flow that is greater than the optimum amount at a given operating condition. For example, during operating conditions where the piston cooling jets are inoperable a much lower pump output can be tolerated. Reducing the pump output to the ideal optimum reduces the work that the pump must do and in turn reduces the parasitic drag on the engine, leading to increased engine efficiency.

In view of the aforesaid, it is an object of the present invention to provide a valve assembly, which can be used to regulate recirculation fluid pressures, in particular oil pressures, at two or more different predetermined maximum fluid pressures. It is a further object, to provide a valve assembly, which is particularly simple in construction and exhibits a long service life.

According to a first embodiment, the invention relates to a valve assembly for a pump, the valve assembly comprising a recirculation valve with a first port and a second port, the recirculation valve being moveable between a closed state, in which the first port is disconnected from the second port, and an open state, in which the first port is connected to the second port. The valve assembly further comprises a first resilient biasing means adapted to bias the recirculation valve in its closed position and a control valve adapted to control the force required to move the recirculation valve from the closed position into the open position, against the first resilient biasing means. The control valve comprises a first position, in which movement of the recirculation valve against the first resilient biasing means requires a first fluid pressure, and a second position, in which movement of the recirculation valve against the first resilient biasing means requires a second fluid pressure. The recirculation valve comprises a first pilot port, the recirculation valve being adapted to move from its closed state into its open state if a fluid pressure applied to the first pilot port exceeds the aforesaid first or second fluid pressure.

In simple terms, the valve assembly according to the present invention comprises a control valve, which is adapted to alter the fluid pressure necessary to move the recirculation valve between its closed and opened states. For example, if the control valve is in its first position, the control valve may work together with the first resilient biasing means to bias the recirculation valve in its closed position. In this case, the first fluid pressure required to move the recirculation valve against the first resilient biasing means is relatively high. If the same control valve is then moved into its second position, the control valve may, for example, stop supporting the first resilient biasing means, hence the second pressure required to move the recirculation valve against the first resilient biasing means would then be defined by the biasing force of the first resilient biasing means alone. In this example, the first fluid pressure of the first position of the control valve would be higher than the second fluid pressure in the second state of the control valve.

The present invention has the advantage that the assembly can be used to control fluid pressure, in particular engine oil pressure at various, that is at least two, predetermined feedback pressures, such that fluid flow (e.g. oil flow) is never greater than the optimum amount at a given operating condition.

The pilot port of the control valve is directly connected to the first pilot port of the recirculation valve means that the connection between the pilot ports does not include any flow-restricting devices, such as throttles or proportional spool valves. In other words, the pressure acting on the pilot port of the control valve is always identical to the pressure acting on the first pilot port of the recirculation valve.

In another embodiment, the control valve comprises a first port and a second port, wherein in the first position, the second port is disconnected from the first port, and in the second position, the second port is connected to the first port, and wherein the second port is connected to a second pilot port of the recirculation valve. According to this embodiment, the control valve is constructed as a pilot valve for the recirculation valve. Pressurised fluid applied to the first port of the control valve can be used as a pilot pressure applied to the second pilot port of the recirculation valve, in the first position of the control valve. The second pilot port, which is connected to the outlet of the control valve, can thus be used to determine the fluid pressure required at the first fluid port in order to move the recirculation valve against the first resilient biasing means.

In another embodiment, the second pilot port of the recirculation valve is arranged to support the first resilient biasing member in biasing the recirculation valve port to its closed position. As mentioned previously, the valve assembly may be arranged such that fluid pressure applied from the second port (outlet) of the control valve to the second pilot port of the recirculation valve acts together with the first resilient biasing member to bias the recirculation valve towards its closed position. That is, if the control valve is in its first, connected position, a first fluid pressure required to move the recirculation valve from its closed into its open position is the sum of the pressure supplied by the first resilient biasing member and the second pilot pressure. Alternatively, as will be described in more detail below, the second pilot port of the recirculation valve may also be arranged to support the recirculation valve in moving towards the open position, that is against the first resilient biasing member.

According to another embodiment, the recirculation valve comprises a regulator spool, the regulator spool comprising a first end face opposite a second end face. The regulator spool is preferably received in a cavity of a valve block, between the inlet port and the outlet port, and adapted to connect the inlet port and the outlet port with each other, in the open position of the recirculation valve.

According to another embodiment, the regulator spool comprises a first shoulder portion arranged between the first and second end face, the first shoulder portion defining a bearing surface for the first resilient biasing means. In other words, the first resilient biasing means may be arranged along the outer diameter of the regulator spool, between the first and second end face, thereby reducing the space requirements of the regulator spool.

In another embodiment, the first end face is connected to the first pilot port of the recirculation valve and the second end face is connected to the second pilot port of the recirculation valve. According to this embodiment, the first and second pilot ports are constructed as pressure surfaces, which are arranged directly opposite each other. Fluid pressure applied to the first and second pilot ports will thus work against each other, depending on the ratio of surface areas between the first and second pilot ports.

Alternatively, the first end face of the regulator spool may be connected to the second pilot port of the recirculation valve. In this case, the regulator spool may further comprise a second shoulder portion arranged between the first shoulder portion and the first end face, the second shoulder portion being connected to the first pilot port of the recirculation valve.

In another embodiment, the control valve may comprise a pilot port and is adapted to move from its first position into its second position if a fluid pressure applied to the pilot port exceeds a threshold pressure. In this case, it is preferred to connect the pilot port of the control valve directly to the first pilot port of the recirculation valve, such that said pilot ports are subjected to the same fluid pressure at any time. The control valve could also comprise a solenoid actuator instead of or in addition to the pilot port, which is adapted to either move or assist movement of the control valve from its first position into its second position upon activation of the solenoid.

According to another aspect, the valve assembly may comprise a second resilient biasing means adapted to bias the control valve in its first position. Alternatively, the second resilient biasing means could also be used to bias the control valve in its second position. In this embodiment, the first threshold required to move the control valve from its first position into its second position, is preferably dependent on a biasing force of the second biasing member only. That is, if the fluid pressure applied on the pilot port of the control valve exceeds the biasing force of the second biasing member, the control valve is transferred from its first position into its second position, and can thereby change the fluid pressure required to move the recirculation valve.

In another embodiment, the control valve comprises a solenoid actuator, arranged to work against the second resilient biasing means, in such a way that the first threshold is further dependent on a force applied by the solenoid actuator. For example, the solenoid actuator may either be used to overcome the biasing fore of the second resilient biasing means alone or together with the aforementioned pilot port pressure. In the latter case, the solenoid actuator is adapted to reduce the force required at the pilot port to overcome the biasing force of the second resilient biasing means, such that the threshold pressure is reduced and lower pressure at the pilot port of the control valve will be sufficient to move the control valve from its first position into its second position. Of course, it is equivalently feasible to arrange the solenoid actuator such that activation thereof supports the biasing force of the second resilient biasing means. In this alternative example, the first threshold would be the sum of the forces applied by the second resilient biasing means and the solenoid actuator.

In another embodiment, the solenoid actuator comprises an on/off solenoid. Accordingly, the control valve of this embodiment can have two different threshold pressures, required to move the control valve against the second biasing means. One threshold pressure is determined by the forces applied when the solenoid is turned off and another determined by the forces applied when the solenoid is on. Alternatively, the solenoid actuator may comprise a proportional solenoid. This embodiment would enable the valve assembly to be adjusted to an infinite amount of different pressure thresholds required to move the control valve between its first and second position. The threshold pressure could then be set continuously by changing the actuation energy applied by the solenoid.

According to another embodiment, the second resilient biasing means is adapted to bias the control valve in its first position. Alternatively, the second resilient biasing means can also be adapted to bias the control valve in its second position.

The present invention further relates to a pump comprising a high pressure port, a low pressure port and a valve assembly as described hereinbefore. The high pressure port of the pump is connected to the first port of the recirculation valve, wherein the low pressure port of the pump is connected to the second port of the recirculation valve.

In a preferred embodiment, the pump may be an oil pump for an engine lubrication system. In a particular embodiment, the invention further relates to an engine lubrication system, comprising an oil sump, a pump as described hereinbefore and a main oil gallery. The main oil gallery is connected to the high pressure port of the pump and therefore also to the inlet port of the recirculation valve. The main oil gallery may further be connected to the first pilot port of the control valve and recirculation valve.

An example of a valve assembly according to the present invention will now be described with reference to the accompanying figures in which:

FIGURE la is a schematic cross-section of a first embodiment of the valve assembly according to the present invention with the control valve in its first position;

FIGURE lb is a schematic cross-section of a first embodiment of the valve assembly with the control valve in its second position;

FIGURE lc is a first schematic diagram, illustrating the main gallery pressure over the pump displacement of the first embodiment, in a deactivated state of the solenoid;

FIGURE Id is a second schematic diagram, illustrating the main gallery pressure over the pump displacement of the first embodiment, in an activated state of the solenoid;

FIGURE le is a third schematic diagram, illustrating the main gallery pressure over the pump displacement of an alternative embodiment, in an activated state of the solenoid;

FIGURE 2a is a schematic cross-section of a second embodiment of the valve assembly according to the present invention with the control valve in its first position;

FIGURE 2b is a schematic cross-section of the second embodiment of the valve assembly with the control valve in its second position;

FIGURE 3a is a schematic cross-section of a third embodiment of the valve assembly of the present invention with the control valve in its first position;

FIGURE 3b is a schematic cross-section of the third embodiment of the valve assembly with the control valve in its second position;

FIGURE 4a is a schematic cross-section of a fourth embodiment of the valve assembly according to the present invention with the control valve in its first position; and

FIGURE 4b is a schematic cross-section of the fourth embodiment with the control valve in its second position.

The following description of the exemplary embodiments refers specifically to the application of the valve assembly within an engine lubrication system. However, it should be understood that the valve assembly can generally be utilised in any hydraulic system requiring a recirculation valve with adjustable brake points.

Figures la and lb show a schematic cross-section of a first embodiment of the valve assembly according to the present invention. The valve assembly is part of a pump system 100 of an engine lubrication system (not shown). The engine lubrication system typically comprises an oil sump 1, which is connected to an inlet or low pressure port 21 of oil pump 2. The outlet or high pressure port 22 of pump 2 is connected to a main oil gallery 3 of the lubrication system. In the example of Figures la and lb, oil flow restricting devices such as oil coolers or oil filters are generally depicted as throttle 5, arranged between the pump outlet 22 and the main oil gallery 3. The pressurised lubrication oil provided to the oil main gallery 3 is then distributed to commonly known engine parts, such as pistons or the cam shaft, which act as further resistance to the oil flow depicted as throttle 6. After the engine oil is provided to the different parts of the engine depicted generically as throttle 6, the oil is reverted back to sump 1.

As mentioned hereinbefore, it is commonly known to prevent excess oil flow provided by pump 2 from being delivered to the engine main gallery 3. To this end, the valve assembly of the present invention is connected to pump 2. In particular, the high pressure or outlet port 22 of pump 2 is connected to a first port 301 of a recirculation valve 30. The low pressure or inlet port 21 of pump 2 is connected to a second port 302 of the recirculation valve 30.

The recirculation valve 30 illustrated in Figures la and lb is constructed as a spool valve comprising a regulator spool 31 that defines a control chamber 32, which is in fluid communication with the first port 301. The regulator spool 31 of the recirculation valve 30 is generally moveable between a first position, shown in Figures la and lb, in which the first port 301 is disconnected from the second port 302, into a second position (to the left in Figures la and lb), in which the control chamber 32 connects the first port 301 with the second port 302. Of course, it will be understood that, in the open position of the recirculation valve 30, the outlet port 22 of the pump 2 is directly connected to the inlet port 21 and the fluid flow provided by pump 2 is hence recirculated via recirculation valve 30. That is, in the open position of the recirculation valve 30, the pressure in the main oil gallery can no longer rise.

The regulator spool 31 is biased towards its first position shown in Figure la by means of a first resilient biasing means, such as compression spring 33. The regulator spool 31 comprises a first end face 34 at the first end of the regulator spool and a second end face 35 at a second, opposite end of the regulator spool 31. Between the first end face 34 and the second end face 35, there is a first shoulder portion 36 which defines a bearing surface for compression spring 33. The regulator spool 31 is received within a first bore 41 of a valve block 40. The bore 41 comprises a first shoulder portion 42, which is designed as a stop which engages the first end face 34 of the regulator spool 31 in its first position. A second shoulder portion 43 is located at an opposite end region of bore 41 and functions as a second bearing surface for compression spring 33.

Bore 41 and the first pressure face 34 of the regulator spool 31 act together as a first pilot port 51 of the recirculation valve. The pilot port 51 is directly connected to the main oil gallery 3 of the engine lubrication system, as indicated by conduit 50. Accordingly, the main oil gallery pressure is fed back and applied to the first pilot port 51 of the recirculation valve 30. In a mode of operation, which will be described in more detail with regards to Figure lb below, the main oil gallery pressure applied to the first pilot port and therefore to the first end face 34 of the recirculation valve 30 will act against the biasing force exerted by the compression spring 33. In said mode, if the force acting on first end face 34 overcomes the compressive load of spring 33, the regulator spool 31 moves to the left in Figures la and lb, and thus opens the connection between the first and second ports 301, 302 of the recirculation valve 30.

Figures la and lb further schematically show a control valve 70, which is adapted to control the force required to move the recirculation valve 30 from its closed position to the open position. The control valve 70 is constructed as a 3/2 valve, meaning that the control valve 70 comprises three ports 71, 72 and 73, and two operating positions. The first operating position is shown in Figure la. The second operating position is shown in Figure lb. a first port 71 is always connected to the main oil gallery 3 (connection not illustrated) and thus the inlet port 71 of control valve 70 always has a pressure level equivalent to the main gallery pressure. A second port 72 of the control valve 70 is connected to the second end face 35 of the regulator spool 31, which defines a second pilot port 52 of the recirculation valve 30. The outlet port 72 of control valve 70 is connected to the second end face 35 via bore 45 of valve block 40, connecting the outlet 72 to the second end region of first bore 41, opposite the first pilot port 51.

In the first mode of operation depicted in Figure la, the first port 71 of control valve 70 is connected to the second port 72, thereby connecting the second end portion 44 of bore 41 to the main gallery pressure. Accordingly, in the first position of the control valve 70 of the first embodiment, the main oil gallery pressure is applied to the second end face 35, which acts as a second pilot port 52 of the regulator spool 31. It follows that, in the first position of control valve 70, the pilot pressure acting on the first pilot port 51 acts against the combined forces created by the second pilot port 52 and the compression spring 33.

The second position of the control valve 70 is shown in Figure lb. As illustrated, the second port 72 of the control valve 70 is connected to a third (drain) port 73 in the second position of the control valve 70. The inlet port 71, however, is shut off. Accordingly, oil present in the second end portion 44 of the first bore 41 is drained in the direction of oil sump 1. In other words, in the second position of the control valve 70, no pressurised fluid acts on the second pilot port 52. The force exerted by the first pilot port 51 on the first end face 34 then only needs to overcome the force created by compression spring 33 to open recirculation valve 30. In the second position of the control valve 70, the recirculation valve 30 is biased towards its first position by the compression spring 33 only.

The control valve 70 illustrated in Figures la and lb is a 3/2 directional on/off valve. However, in a non-illustrated embodiment, the control valve could be constructed as a proportional valve to meter the fluid flow provided to the second pilot port/the oil sump. According to this embodiment,

The control valve 70 of Figures la and lb is a pilot operated solenoid valve. In its rest position, the control valve 70 is biased towards its first position via a second resilient biasing means 75. The control valve 70 further comprises a pilot port 76, which is directly connected to the first pilot port 51 of the recirculation valve 30, via third and fourth bores 46, 47 of the valve block 40. In particular, the third and fourth bores 46, 47 connect the first end portion of the first bore 41 to the pilot port 76 of control valve 70. As a consequence, the main gallery oil pressure is applied simultaneously to the first pilot port 51 of the recirculation valve and the pilot port 76 of the control valve 70.

The pilot port 76 is arranged such that pilot pressure acting on the pilot port 76 acts against the second resilient biasing means 75 to move the control valve from its first position (Figure la) into its second position (Figure lb). The control valve 70 shown in Figures la and lb further comprises a solenoid actuator 77, which is adapted to assist the pilot port 76 in moving the control valve 70 from its first position into its second position. The solenoid actuator 77, too, is adapted to act against the biasing force of the second resilient biasing means 75. As mentioned previously, in the first position of the control valve 70, movement of the recirculation valve 30 from its closed position into its open position is countered by the combined forces of compression spring 33 and second pilot port 52

Figs, lc to le schematically show the main oil gallery pressure behaviour during different states/set-ups of the valve assembly. It should be noted that the values for the main oil gallery pressure and the pump displacement do not represent any real world pressures/flows and are intended for comparison of the different states of the valve assembly. A first pressure threshold, required to move the control valve 70 from its first position (Fig. la) into its second position (Fig. lb) against the biasing force of the second biasing means 75, is labelled as P70. A second pressure threshold, required to move the recirculation valve 30 against the combined forces of the compression spring 33 and the pressurised second pilot port 52, is labelled as P33+52. A third pressure threshold, required to move the recirculation valve 30 against the force of the compression spring 33, is labelled as P33.

Fig. lc schematically illustrates a state, in which the solenoid actuator 77 is not energised. In this state, the second fluid pressure threshold P33+52 will be required to act on pilot port 51 to overcome the biasing force of the first resilient biasing means, i.e. compression spring 33, and the biasing force of the second pilot port 52 to move the recirculation valve into its open position. Once that second pressure threshold P33+52 is reached, the recirculation valve 30 opens and thus regulates the main oil gallery pressure. Since the pilot pressure acting on the first and second pilot ports 51, 52 is identical, the recirculation valve can only be activated, if the first end face 34 has a larger surface area than the second end face 35 of regulator spool 31. The fluid pressure P33+52 required to open the recirculation valve 30 represents a first predetermined maximum value for the main oil gallery pressure. It should be noted that, according to this embodiment, the pressure threshold P70, required to move the control valve 70 into its second position is arranged to be higher than the pressure threshold P33+52. Accordingly, if the solenoid actuator 77 is not energised, the control valve 70 will remain in its first position, as the main oil gallery pressure will not rise above the second pressure threshold P33+52,

If the solenoid actuator 77 is active, the threshold pressure required to move the control valve 70 from its first position into its second position is reduced. As such, the control valve 70 will move from its first position into its second position at a lower main gallery oil pressure, thereby relieving the second pilot port 52 of the recirculation valve 30.

In Fig. Id, the solenoid actuator is energised, thus the main gallery pressure P33+52, required to move the recirculation valve into its open position is higher than the pressure P70 required on pilot port 76 to move the control valve 70 into its second position. In the embodiment of Fig. Id, this is illustrated by a pressure threshold P70, which has a reduced value compared to the embodiment of Fig. lc (3 instead of 6). This is because the solenoid actuator supports the pilot port 76 in moving the control valve 70 against the second biasing means 75, thereby reducing the amount of pressure needed at the pilot port 76. Once the main gallery pressure is high enough to move the control valve 70 into its second position, the first and second ports

71, 72 of the control valve 70 are disconnected, thereby relieving fluid pressure from the second fluid port of the recirculation valve 30. Consequently, the pressure acting on first pilot port 51 of the recirculation valve 30 is then only required to overcome the compression force of spring 33 to move the recirculation valve 30 from its closed position into its open position. Depending on the size and arrangement of the solenoid 70, the pressure threshold 70, required to move the control valve 70, may be higher or lower than the pressure threshold P33. If the pressure threshold P70 is higher than the pressure threshold P33 (illustrated in Fig. Id), then the recirculation valve 30 will be transferred into its open position, as soon as the control valve P70 is moved into its second position. Once the recirculation valve 30 is in its open position, the pressure will start to drop to the threshold P33. However, as soon as the main oil gallery pressure falls below the threshold pressure P70, the control valve 70, will move back into its first position, thereby pressurising the second pilot port 52. As a consequence, the recirculation valve 30 will again be moved into its closed position and the main gallery pressure will rise again until the pressure threshold P70 is reached. In this way, the main gallery pressure will be regulated to be maintained around the pressure threshold P70, which represents a second (lower) predetermined maximum value for the main oil gallery pressure, when the solenoid 77 is energised.

Fig. le shows another, alternative embodiment of the valve assembly with an energised solenoid 77. In this embodiment, the solenoid is arranged to reduce the control valve 70 pressure threshold P70 to a value below the threshold P33, required to move the recirculation valve 30 against the compression spring 33. Accordingly, once the main oil gallery pressure exceeds the threshold P70, the control valve 70 is transferred into its second position, thereby relieving the fluid pressure from second pilot port 52. However, the main oil gallery pressure will still not be sufficient to move the recirculation valve 30 into its open position. As such, the main oil gallery pressure will keep rising until threshold P33 is reached and the recirculation valve 30 opens. In this case, the second (lower) predetermined maximum value for the main oil gallery pressure is defined by the first biasing means, i.e. spring 33.

In both cases described in Figs Id and le, the second maximum fluid pressure will be lower than the first maximum fluid pressure. In this way, the valve assembly according to the first embodiment is able to provide two different maximum oil gallery pressures, depending on the state of activation of the solenoid actuator of the control valve 70. It will be appreciated from the discussion of Figs. Id and le that the value of the second maximum oil gallery pressure is directly dependent on the force provided by the solenoid actuator 77. Accordingly, if the solenoid is a proportional solenoid, rather than the illustrated on/off solenoid, the valve arrangement could be used to continuously change the value of the second maximum oil gallery pressure. In other words, the valve assembly would be arranged to maintain the main oil gallery pressure at any value between the pressure P33, required to overcome spring 33 alone, and the pressure P33+52, required to overcome spring 33 supported by pilot port 52.

Figures 2a and 2b show a schematic of an engine lubrication system with an oil pump 200 including a valve assembly according to a second embodiment of the present invention. Identical parts of the first and second embodiments shown in Figures 1 and 2 are labelled with identical reference signs. In contrast to the first embodiment, the feedback pressure of the second embodiment, which is applied to the first port 51 of the recirculation valve 30 and to the pilot port 76 of the control valve 70, is not the main oil gallery pressure but the high pressure provided by outlet port 22 of the pump 2. In particular, this is achieved by connecting the first pilot port 51 of the recirculation valve 30 and the pilot port 76 of the control valve 70 directly to the first port 301 of the recirculation valve. To this end, the valve block 40 comprises a further bore 48 connecting the inlet port 301 of the recirculation valve 30 to its first pilot port 51.

The function of the second embodiment according to Figures 2a and 2b is substantially identical to the function of the first embodiment. That is, in the first position of the control valve 70, shown in Figure 2a, the recirculation valve 30 is prevented from moving into its open position. In the second position of the control valve 70, the recirculation valve can be moved into its open position if the high pressure outlet flow provided by the pump 2 exerts a force on the first end face 34 of the regulator spool 31 that exceeds the force applied by the compression spring 33 on the first shoulder portion 36 of the regulator spool 31. Again, the pressure required to move the control valve 70 from its first position into its second position (Figure 2b) can be varied by actuation of the solenoid actuator 77, thereby changing the fluid pressure required to move the recirculation valve 30 from its closed to its open position.

Figures 3a and 3b show another engine lubrication system comprising a pump 300 including a valve assembly according to a third embodiment of the present invention. Identical parts of the first and third embodiment are labelled with identical reference signs. In contrast to the first and second embodiments, the valve body 40 of the third embodiment comprises a second bore 345 connecting the outlet port 72 of the control valve 70 with the second control chamber 37 formed between the first shoulder 36 of the regulator spool 31 and the second shoulder portion 43 of the first bore 41. That is, according to the third embodiment, the outlet port 72 of the control valve 70 is directly connected with the second control chamber 37, which houses the compression spring 33. Accordingly, the second control chamber 37 acts as the second pilot port 352 and the pilot pressure is applied to the first shoulder portion 36 of the regulator spool 31. The third embodiment, therefore, differs from the first embodiment in that the pilot pressure (main gallery oil pressure) is applied to the surface area of shoulder portion 36, rather than the surface area of the second end face 35 of the regulator spool 31. One advantage of this arrangement is that the compression spring 33 remains lubricated constantly.

The function of the third embodiment is largely identical to the function of the first and second embodiments with the exception that the surface area of the second pilot port 352 is slightly different. Again, Figure 3a show the control valve 70 in its first position, whereas Figure 3b shows the control valve 70 in its second position.

A fourth embodiment of the valve assembly according to the present invention is shown in Figure 4a together with an engine oil pump assembly 400. Identical parts of the first and fourth embodiments are labelled with identical reference signs. According to the fourth embodiment, the first pilot port 451 of the recirculation valve 30 is connected to a second shoulder portion 438, which is arranged between the first end face 434 and the second end face 35 of the regulator spool 31. The second shoulder portion 438 is arranged opposite to the first shoulder portion 36, i.e. towards the first end face 434. Again, the outlet 72 of the control valve 70 is connected to a second pilot port 452 of the recirculation valve 30. However, in this embodiment, the second pilot port 452 is arranged at the first end face 434 of the recirculation valve 30. It will be appreciated that the first and second pilot ports 451, 452 of this embodiment act together to overcome the biasing force applied by the compression spring 33, in order to move the recirculation valve 30 from its closed position in Figures 4a and 4b to its open position (not illustrated).

The function of the valve assembly according to the fourth embodiment is substantially different to the function of the first three embodiments. In particular, while the valve assembly is still adapted to provide at least two different maximum fluid pressures for the engine lubrication system, actuation of the control valve 70 will now increase the maximum fluid pressure.

In the first position of the control valve 70, shown in Figure 4a, both the first and second pilot ports 451, 452 of the recirculation valve 30 are pressurised with the oil pressure of the main oil gallery. Accordingly, the forces exerted on the first end face 434 and on the second shoulder 438 via the main gallery oil pressure act together against the biasing force of the compression spring 33. It follows that the maximum oil pressure of the main oil gallery, in this position of the control valve 70, is defined by the biasing force of the compression spring and the combined surface area of the first end face 434 and the second shoulder portion 438.

In the second position, shown in Figure 4b, the control valve 70 connects the second pilot port 452 of the recirculation valve 30 with the third port (drain) 73 of the control valve, which in turn is connected to the oil sump 1. It will be appreciated that, in the second position of the control valve 70, the main oil gallery pressure is only applied to the second shoulder portion 438. Therefore, the effective surface area, which is used to act against the compression spring 33, is reduced. It follows that the second fluid pressure required to move the recirculation valve into its open position when the control valve 70 is in its second position, is higher than the first fluid pressure mentioned hereinbefore.

It should be understood that the fluid pressure required to move the control valve 70 of the fourth embodiment from its first position into its second position is predetermined to be higher than the fluid pressure required to move the recirculation valve 30 into its open position, if the solenoid actuator 77 is not activated. This will guarantee, that without activating the solenoid actuator 77, the control valve will not unintentionally move from its first position shown in Figure 4a into its second position shown in Figure 4b.

If the solenoid actuator 77 is activated, the fluid pressure required at the pilot port 76 to move the control valve 70 into its second position (Figure 4b), is configured to be lower than a fluid pressure required to move the recirculation valve 30 into its open position, when using the first and second pilot ports 451, 452 together. In other words, if the solenoid actuator 77 is activated, the control valve 70 will move from its first position into its second position, before the fluid pressure reaches a level, which is high enough to move the recirculation valve 30 from its closed position into its open position. As described hereinbefore, the second pilot port 452 is then vented towards the oil sump 1 and only the first pilot port 451 is used to move the recirculation valve 30 from its closed position into its open position. This will automatically result in an increase of the maximum oil pressure within the main oil gallery to a second pressure value.

From the foregoing, it should be clear that all of the described embodiments provide at least two maximum pressure values for the main oil gallery. However, in contrast to the fourth embodiment, the second maximum pressure value of the first three embodiments is lower than the first maximum pressure value. Moreover, it should be noted that in the first three embodiments, a movement of the recirculation valve 30 is prevented for as long as the control valve 70 remains in its first position. In contrast to this, the recirculation valve 30 of the fourth embodiment can move from its closed to its open position in both states of the control valve 70.

While the first and second resilient biasing means have been depicted as compression springs, it should be understood that, depending on the biasing required, any alternative resilient biasing means could be utilised. Additionally, the illustrated, pilot-operated solenoid valve 70 could also be constructed as a purely solenoid actuated control valve, which is exclusively operated through electric switching signals.

Claims

1. Valve assembly for a lubrication system, the valve assembly comprising:

• A recirculation valve with a first port and a second port, the recirculation valve being movable between a closed state, in which the first port is disconnected from the second port, and an open state, in which the first port is connected to the second port;

• a first resilient biasing means adapted to bias the recirculation valve in its closed position;

• a control valve adapted to control the force required to move the recirculation valve from the closed position into the open position, against the first resilient biasing means, the control valve comprising a first position, in which movement of the recirculation valve against the first resilient biasing means requires a first fluid pressure, and a second position, in which movement of the recirculation valve against the first resilient biasing means requires a second pressure;

wherein the recirculation valve comprises a first pilot port, the recirculation valve being adapted to move from its closed state into its open state if a fluid pressure applied to the first pilot port exceeds said first or second fluid pressure.

2. The valve assembly according to claim 1, wherein the control valve comprises an inlet port and an outlet port, wherein in the first position, the outlet port is connected from the inlet port, and in the second position, the outlet port is disconnected from the inlet port, and wherein the outlet port is connected to a second pilot port of the recirculation valve.

3. The valve assembly according to claim 2, wherein the second pilot port of the recirculation valve is arranged to support the first resilient biasing member in biasing the recirculation valve towards its closed position.

4. The valve assembly according to claim 2, wherein the second pilot port of the recirculation valve is arranged to support the first pilot port in moving the recirculation valve towards its open position, against the biasing force of the first resilient biasing member.

5. The valve assembly according to claim 3 or 4, wherein the recirculation valve comprises a regulator spool, the regulator spool comprising a first end face opposite a second end face.

6. The valve assembly according to claim 5, wherein the regulator spool comprises a first shoulder portion arranged between the first and second end face, the first shoulder defining a bearing surface for the first resilient biasing means.

7. The valve assembly according to claim 5 or 6 in combination with claim 3, wherein the first end face is connected to the first pilot port of the recirculation valve and the second end face is connected to the second pilot port of the recirculation valve.

8. The valve assembly according to claims 5 or 6 in combination with claim 4, wherein the first end face is connected to the second pilot port of the recirculation valve.

9. The valve assembly according to claim 8, wherein the regulator spool further comprises a second shoulder portion arranged between the first shoulder portion and the first end face, the second shoulder portion being connected to the first pilot port of the recirculation valve.

10. The valve assembly according to any one of claims 1 to 9, wherein the control valve is an on/off valve.

11. The valve assembly according to any one of claims 1 to 9, wherein the control valve is a proportional valve.

12. The valve assembly according to any one of claims 1 to 11, wherein the valve assembly comprises a second resilient biasing means adapted to bias the control valve in its first position.

13. The valve assembly according to claim 12, wherein the control valve comprises a pilot port, the control valve being adapted to move from its first position into its second position if a fluid pressure applied to the pilot port exceeds a threshold pressure.

14. The valve assembly according to claim 13, wherein the pilot port of the control valve is directly connected to the first pilot port of the recirculation valve.

15. The valve assembly according to claim 13 or 14, wherein the threshold pressure is dependent on a biasing force of the second biasing member.

16. The valve assembly according to claim 15, wherein the control valve comprises a solenoid actuator, arranged to work against the second resilient biasing means, in such a way that the threshold pressure is further dependent on a force applied by the solenoid actuator.

17. The valve assembly according to claim 16, wherein the solenoid actuator comprises an on/off solenoid.

18. The valve assembly according to claim 16, wherein the solenoid actuator comprises a proportional solenoid.

19. A pump system comprising:

• a pump comprising a high pressure port and a low pressure port; and • a valve assembly according to any one of claims 1 to 14, wherein the high pressure port of the pump is connected to the first port of the recirculation valve, and wherein the low pressure port of the pump is connected to the second port of the recirculation valve.

20. The pump according to claim 19, wherein the high pressure port of the pump is directly connected or connectable to the first pilot port of the recirculation valve.

21. The pump according to claim 19or 20, wherein the high pressure port of the pump is directly connectable to the second pilot port of the recirculation valve, via the control valve.

22. The pump according to claim 21, wherein the high pressure port of the pump is directly connected or connectable to the inlet port of the control valve.

23. The pump according to any one of claims 19to 22, wherein the pump comprises a pump housing and wherein the vale assembly is arranged within the pump housing.

24. The pump according to any one of claims 19to 23, wherein the pump is an oil pump.

25. Engine lubrication system, comprising an oil sump, a pump according to claim 24and a main oil gallery.

26. Engine lubrication system according to claim 25, wherein the main oil gallery is connected to the high pressure port of the pump.

Intellectual

Property

Office

Application No: GB1614459.4