Method of controlling an internal combustion engine

Abstract

A method of controlling an internal combustion engine 1 comprising an electric lubricant pump 4 and a turbocharger 10, comprising determining whether the internal combustion engine 1 is operating in a

Description

Field of the disclosure 5 The present disclosure relates to turbochargers. In particular, the present disclosure relates to lubrication of a turbocharger. Background 10 Turbochargers typically comprise a compressor and a turbine. The compressor may be connected to the turbine by a bearing section comprising a bearing. Turbochargers bearings may be supplied with a continuous supply of lubricant (e.g. oil) to bearing surfaces to maintain shaft stability and prevent excessive wear of the bearing surfaces. LO 15 In order to provide suitable lubrication, the lubricant may be supplied to the bearing section under pressure. If the turbocharger bearing is operated without sufficient lubricant pressure, the bearing surfaces may become worn and / or the bearing may seize. Low lubricant pressure is particularly prevalent during start-up of an internal combustion engine, CM as lubricant pressure may lower whilst the internal combustion engine is at rest. CM 20 Lubricant flow may be supplied by a pump connected to an internal combustion engine. Conventionally, the pump is driven by the internal combustion engine. Accordingly, during normal operation of the turbocharger / internal combustion engine, the lubricant pressure supplied to the turbocharger is dependent on the engine speed of the internal combustion 25 engine. Summary According to a first aspect of the disclosure, a method of controlling an internal combustion 30 engine comprising an electric lubricant pump and a turbocharger is provided. The method comprises determining whether the internal combustion engine is operating in a normal operating mode where a turbo boost of the turbocharger is above a boost threshold or a low demand operating mode where the turbo boost is no greater than the boost threshold. When it is determined that the internal combustion engine is operating in the normal 35 operating mode the method comprises supplying electrical power to the electric lubricant pump to cause lubricant to be supplied to the turbocharger at a pressure of at least a predetermined lubricant pressure. When it is determined that the internal combustion engine is operating in the low demand operating mode, the method comprises reducing the electrical power supplied to the electric lubricant pump to reduce the lubricant pressure to a leakage prevention pressure which is lower than the predetermined lubricant pressure. According to the method, the turbocharger is supplied with lubricant from an electric lubricant pump. According to the method of the first aspect, during normal operation of the internal combustion engine lubricant may be supplied to the turbocharger at a predetermined lubricant pressure. During the low demand operating mode of the internal combustion engine, the reduction in turbo boost may result in an increased pressure differential between a bearing section of the turbocharger (where the lubricant flows) and the compressor and / or turbine of the turbocharger (which normally operate under pressure). The increased pressure differential may result in leakage of lubricant from the bearing section into the compressor and / or turbine. The introduction of lubricant into the air flow of the turbocharger may damage downstream components such as the aftertreatments system and the like. According to the method of the first aspect, in the low demand operating mode, the lubricant pressure may be reduced to a leakage prevention pressure which is lower than the predetermined lubricant pressure in order to reduce the pressure differential. This in turn reduces or prevents leakage of lubricant into the compressor and / or turbine of the turbocharger. Such control of the lubricant pressure may be possible as the lubricant is pressurised using an electric lubricant pump where the pumping power may be controlled independently of the operation of the internal combustion engine. According to a second aspect of the disclosure, a controller for an internal combustion engine comprising an electric lubricant pump and a turbocharger is provided. The controller is configured to determine whether the internal combustion engine is operating in a normal operating mode where a turbo boost of the turbocharger is above a boost threshold, or a low demand operating mode where the turbo boost of the turbocharger is no greater than the boost threshold. When the controller determines that the internal combustion engine is operating in the normal operating mode, the controller is configured to cause electrical power to be supplied to the electric lubricant pump to cause lubricant to be supplied to the turbocharger at a pressure of at least a predetermined lubricant pressure. When the controller determines that the internal combustion engine is operating in the low demand operating mode, the controller is configured to reduce the electrical power supplied to the electric lubricant pump to reduce the lubricant pressure to a leakage prevention pressure which is lower than the predetermined lubricant pressure. As such, the controller of the second aspect may cause an internal combustion engine having a turbocharger and an electric lubricant to perform the method of the first aspect. According to a third aspect of the disclosure, an internal combustion engine for a machine is provided. The internal combustion engine comprises a controller according to the second aspect, a turbocharger, and an electric lubricant pump configured to supply lubricant to the turbocharger. As such, the internal combustion engine of the third aspect may perform the method of the first aspect. Brief description of the figures Embodiments of the disclosure will now be described with reference to the following figures in which: Fig. 1 is a block diagram of an internal combustion engine and a turbocharger according to an embodiment of the disclosure; Fig. 2 is a schematic diagram of a leakage path for lubricant in a turbocharger; Fig. 3 is a block diagram of a method of controlling an internal combustion engine according to an embodiment of the disclosure; and Fig. 4 is a graph showing a relationship between lubricant pressure and engine speed. Detailed description According to an embodiment of the disclosure, an internal combustion engine 1 is provided. Fig. 1 shows a schematic system diagram of the internal combustion engine 1. As shown in Fig. 1, the internal combustion engine 1 comprises a turbocharger 10. The internal combustion engine 1 may be provided as part of a machine (not shown in Fig. 1). For example, the machine may be a generator or a work vehicle such as an excavator, a wheel loader, a dozer, a telehandler, a tractor, and the like. As shown in Fig. 1, the turbocharger 10 comprises a compressor 20, a bearing section 30, and a turbine 40. As shown in the system diagram of Fig. 1, the compressor 20 of the turbocharger 10 may be configured to receive an intake gas, for example from an air inlet (not shown in Fig. 1). The compressor 20 of the turbocharger 10 may output the compressed intake gas directly to the internal combustion engine 1, or via an aftercooler (not shown in Fig. 1). The turbine 40 of the turbocharger 10 may be configured to receive gas from the internal combustion engine 1 and to output gas to an aftertreatment system (not shown in Fig. 1). The flow of various gasses to and from the internal combustion engine 1 and turbocharger 10 are indicated in Fig. 1 using dashed lines. The bearing section 30 comprises a bearing 32 which connects a turbine blade assembly (not shown) of the turbine 40 to a compressor impeller (not shown) of the compressor 20. To reduce friction and to reduce or prevent wear of the bearing 32 and associated surfaces of the bearing section 30 / turbocharger 10, the bearing section 30 of the turbocharger 10 may be provided with a supply of lubricant. To reduce or prevent wear of the bearing 32, the bearing section 30 may be supplied with lubricant at a lubricant pressure which is at least a predetermined lubricant pressure. If the turbocharger 10 is operated when the lubricant pressure is below the predetermined lubricant pressure, the bearing 32 (or surfaces of the bearing section 30) may not be sufficiently lubricated, resulting in excessive wear of the respective surface. Prolonged operation of the turbocharger 10 when the lubricant pressure is below the predetermined lubricant pressure may reduce the operational lifetime of the turbocharger 10. As shown in the system diagram of Fig. 1, the internal combustion engine 1 may comprise a lubricant reservoir 3 and an electric lubricant pump 4. The electric lubricant pump 4 may be fluidly connected to the lubricant reservoir 3 and the bearing section 30 of the turbocharger 10. The electric lubricant pump 4 may be configured to pump lubricant from the lubricant reservoir 3 to the bearing section 30 in order to lubricate the bearing 32. The bearing section 32 may also be fluidly connected to the lubricant reservoir 3 to provide a return path 6 for lubricant to the lubricant reservoir 3. During normal operation of the internal combustion engine 1 (e.g. when the internal combustion has been operational for at least several minutes), the electric lubricant pump 4 may pump lubricant from the lubricant reservoir 3 to the turbocharger 10. Lubricant may circulate through the bearing section 30 of the turbocharger 10 and may return to the lubricant reservoir 3 via the return path 6 shown schematically in Fig. 1. According to this disclosure, an electric lubricant pump 4 may be understood to be a pump which may be powered by electrical energy in order to pump lubricant. In some embodiments, the electric lubricant pump 4 may comprise an electric motor (not shown), the electric motor being configured to receive electrical energy (e.g. from a battery connected to the motor, for example a battery of the internal combustion engine 1). The electric lubricant pump 4 may be configured to pump lubricant at a pressure, wherein the pressure may be controlled by the electrical energy supplied to the electric lubricant pump 4. A controller 5 of the internal combustion engine 1 may control the electrical energy supplied to the electric lubricant pump 4 in order to control the pressure of the lubricant supplied to the internal combustion engine 1 / turbocharger 10. As such, it will be appreciated that the electric lubricant pump 4 may not be powered directly by mechanical energy generated by the internal combustion engine 1. In particular, the power output of the electric lubricant pump 4 may not be dependent on the engine speed of the internal combustion engine 1. As shown in Fig. 1, the electric lubricant pump 4 may be configured to pump lubricant to the bearing section 30. In normal operation, the electric lubricant pump may be configured to supply lubricant to the bearing section 30 at a predetermined lubricant pressure. The predetermined lubricant pressure may be selected to ensure that lubricant is provided to the bearing section 30 at a sufficient pressure in order to lubricate all relevant surfaces of the bearing section 30 and turbocharger 10. Providing lubricant at a sufficient pressure to reduces or prevents excessive wear of the bearing 32 when the turbocharger is in use. As such, the predetermined lubricant pressure may be greater than or equal to a first lubricant pressure. For example, in some embodiments, the predetermined lubricant pressure may be at least: 200 kPa, 220 kPa, 240 kPa, 260 kPa, 280 kPa or 300 kPa. In some embodiments, it may be desirable to supply lubricant to the turbocharger 10 at a pressure which does not significantly exceed the pressure required for lubrication of the turbocharger 10 in order to operate the internal combustion engine 1 and electric lubricant pump 4 in an efficient manner. In some embodiments, the electric lubricant pump 4 may be configured to supply lubricant to other components associated with the internal combustion engine 1 in addition to the turbocharger 10. In such embodiments, the predetermined lubricant pressure may be selected based on a lubricant pressure which provides sufficient lubrication of said other components and the turbocharger. As such, it will be appreciated that the predetermined lubrication pressure may be a lubricant pressure which is suitable for providing sufficient lubrication of the components which are fluidly connected to the electric lubricant pump 4 during normal operation of the turbocharger 10. It will be appreciated that when the internal combustion engine 1 is at rest (i.e. engine speed is 0 revolutions per minute (rpm)), the lubricant pressure of lubricant in the bearing section 30 (or any other part of the lubrication system of the internal combustion engine 1) may fall below the predetermined lubricant pressure. As such, upon start-up of the internal combustion engine, a period of time (a start-up time) may be required for the lubricant pressure to reach the predetermined lubricant pressure before normal operation of the internal combustion engine 1 commences. During normal operation, the controller 5 controls the pressure of the lubricant supplied to the turbocharger 10 on the assumption that the turbocharger 10 is operational. During operation of the turbocharger 10, the compressor 20 and turbine 40 of the turbocharger 10 are operated under pressure in order to provide turbo boost for the internal combustion engine 1. In short, during normal operation of the turbocharger 10, the lubricant pressure in the bearing section 30 is balanced by the pressures present in the compressor 20 and turbine 40 providing turbo boost during normal operation of the turbocharger 10. Fig. 2 shows a cross-sectional schematic diagram of possible leakage paths for lubricant from the bearing section 30 of the turbocharger 10. As shown in Fig. 2, in normal operation lubricant flows through the bearing section 30 from the bearing section inlet 33 to the bearing section outlet 34. Lubricant may, in some circumstances, flow via leakage paths shown in Fig. 2 from the bearing section 30 to the compressor 20 and / or the turbine 40. In particular, lubricant may flow through a leakage path between the bearing section 30 and the compressor 20 along a leakage path indicated in Fig. 2 when there is a relatively large pressure difference (relative to the pressure difference during normal operation of the turbocharger 10) between the lubricant pressure in the bearing section 30 and the pressure in the compressor 20. Similarly, lubricant may flow through a leakage path between the bearing section 30 and the turbine 40 when there is a relatively large pressure difference between the lubricant pressure in the bearing section 30 and the pressure in the turbine 40. For example, the turbocharger 10 may be prone to lubricant leakage when the lubricant pressure is at the predetermined pressure and the turbocharger 10 is not operational due to a fault with the turbocharger (such that the turbo boost is effectively zero). By contrast, when the turbocharger 10 is operational (providing turbo boost), the pressure difference between the predetermined lubricant pressure and the pressure in the compressor 20 / turbine 40 is relatively low such that lubricant does not flow along the leakage paths. It will be appreciated that the amount of flow of lubricant along the leakage paths indicated in Fig. 2, even under a relatively large pressure difference is significantly smaller than the flow of lubricant from inlet 33 to outlet 34 of the bearing section 30. In the event that lubricant does flow along one or more leakage paths, lubricant may flow downstream of the turbocharger 10 into the internal combustion engine 1 and / or aftertreatment system (not shown). Downstream flow of lubricant is undesirable as it may cause downstream systems (internal combustion engine 1, aftertreatment system) to operate in unintended states, which may be time consuming or costly to rectify. Thus, according to this disclosure, a method 100 of controlling an internal combustion engine 1 is provided which is aims to reduce or prevent the leakage of lubricant into a turbocharger 10. The method 100 may be performed by the controller 5 of the internal combustion engine 1 shown in Fig. 1. A block diagram of the method 100 is shown in Fig. 3. In step 101, the method 100 comprises determining an operation mode of the internal combustion engine 1. For example, the controller 5 may determine whether the internal combustion engine 1 is operating in a normal operating mode where a turbo boost of the turbocharger is above a boost threshold or a low demand operating mode where the turbo boost is no greater than the boost threshold. As such, the boost threshold may be indicative of a state of operation of the turbocharger below which the pressure in the compressor 20 and / or turbine 40 is such that leakage of lubricant may occur. The controller 5 may determine the turbo boost of the turbocharger based on one or more pressure sensors (not shown) connected to the turbocharger. In some embodiments, the boost threshold may be a predetermined (i.e. fixed) value. In some embodiments, the boost threshold. In some embodiments, the boost threshold may be determined from a control map of the controller, as discussed further below. When it is determined that the internal combustion engine is operating in the normal operating mode (step 102), the method comprises supplying electrical power to the electric lubricant pump to cause lubricant to be supplied to the turbocharger at a pressure of at least a predetermined lubricant pressure. As such, in the normal operation mode, the controller 5 controls the electric lubricant pump to supply lubricant to the turbocharger 10 at the predetermined lubricant pressure which may provide suitable lubrication for the turbocharger 10. For example in some embodiments, the predetermined lubricant pressure may be at least 200 kPa. In some embodiments, when operating in the normal operating mode, electrical power is supplied to the electric lubricant pump to cause lubricant to be supplied to the internal combustion engine at a pressure of at least a predetermined lubricant pressure, wherein the predetermined lubricant pressure may be controlled based on an engine speed of the internal combustion engine 1. As such, in some embodiments the controller 5 may adjust the predetermined lubricant pressure based on an engine speed of the internal combustion engine 1, and / or other operational parameters of the internal combustion engine 1. For example, the controller 5 may be configured to increase the predetermined lubricate pressure as the engine speed increases above an idle speed in order to provide additional lubrication at higher engine speeds. For an internal combustion engine comprising a mechanical lubricant pump (i.e. a pump which is powered by the mechanical power generated by the internal combustion engine), an increase in engine speed may conventionally result in an increase in the lubricant pressure. To prevent the lubricant pressure becoming excessive, a mechanical lubricant pump may be connected to a pressure relief valve. The pressure relief valve may provide a return path for lubricant to a lubricant reservoir when a threshold pressure of the pressure relief valve is exceeded. In some embodiments of the disclosure, the electric lubricant pump 4 may be controlled by the controller 5 in the normal operating mode such that the lubricant pressure does not exceed a threshold pressure. Accordingly, the controller 5 may control the electric lubricant pump independent of the engine speed to provide similar functionality to a pressure relief valve. As such, in some embodiments the lubricant system of the internal combustion engine 1 may be provided without a pressure relief in order to simply the system design. In the event that the turbo boost is no greater than the boost threshold, the controller determines that the internal combustion engine 1 is operating in the low demand operating mode (step 102 of Fig. 3). When it is determined that the internal combustion engine 1 is operating in the low demand operating mode (step 103), the turbocharger 10 may be in a state where the pressure difference between the bearing section 30 and the compressor 20 and / or turbine 40 may result in leakage of lubricant. To reduce or prevent lubricant leakage when the internal combustion engine 1 is operating in the low demand mode (step 103), the method comprises reducing the electrical power supplied to the electric lubricant pump 4 to reduce the lubricant pressure to a leakage prevention pressure which is lower than the predetermined lubricant pressure. By reducing the lubricant pressure to the leakage prevention pressure, the method 100 reduces the pressure difference between the bearing section 30 and the compressor 20 and / or turbine 40 in order to reduce or prevent the leakage of lubricant. In some embodiments, when operating in the low demand operating mode, electrical power may be supplied to the electric lubricant pump 4 to cause lubricant to be supplied to the internal combustion engine 1 at the leakage prevention pressure, wherein the leakage prevention pressure is controlled based on the engine speed of the internal combustion engine 1. In some embodiments, the leakage prevention pressure may be no greater than: 90%, 80 %, 70%, 60 %, or 50 % of the predetermined lubricant pressure. In some embodiments, the leakage prevention pressure may be selected based on the design of the turbocharger 10 and / or an operational speed to the turbocharger 10. For example, in some embodiments the controller 5 may determine the leakage prevention pressure based on a control map of the controller 5 based on an operational speed of the turbocharger 10. As shown in Fig. 3, the method 100 may repeatedly determine the operating mode of the internal combustion engine 1 and control the lubricant pressure of the lubricant accordingly. As such, after determining that the turbo boost has fallen below the turbo boost threshold, the method may continue to check if the internal combustion engine has returned to the normal operating mode based on the turbo boost. In some embodiments, the boost threshold may be determined from a control map of the controller. For example the boost threshold may vary depending on the power output of the internal combustion engine 1, or any other suitable parameter of the internal combustion engine 1. In some embodiments, the boost threshold may be determined based on a fuel quantity of the internal combustion engine 1 and an engine speed of the internal combustion engine 1. According to some embodiments of the disclosure, when the controller 5 determines that the internal combustion engine 1 is operating in the low demand operating mode, depending on the cause of the reduction in turbo boost, the controller 5 may decrease the lubricant to different pressures according to the cause of the reduction. As such, the low demand operating mode may comprise one, or a plurality of operating modes (or submodes) which may be selected by the controller 5, as will be described below. In some embodiments, determining whether the internal combustion engine 1 is operating in a low demand operating mode comprises determining whether the turbocharger 10 is operating in a fault mode. The fault mode of the turbocharger 10 may be determined when the turbo boost is below a first boost threshold. If the turbocharger 10 is determined to be operating in a fault mode, the lubricant pressure may be reduced to a fault leakage prevention pressure. The fault mode of the turbocharger 10 may be determined when a fault in the turbocharger 10 has caused the turbocharger 10 to be effectively non-operational. As such, in some embodiments, the first boost threshold may be about zero turbo boost. In some embodiments, the fault mode may be determined when the turbo boost is below a first boost threshold and when a turbo speed of the turbocharger 10 is below an operational speed threshold. For example, when the operational speed of the turbocharger 10 is about zero, such an operational speed may be indicative of a fault with the turbocharger 10. In other embodiments, the fault mode of the turbocharger 10 may also be determined based on one or more parameters associated with the turbocharger 10 which may be received by the controller 5. As will be appreciated by the skilled person, the controller 5 of the internal combustion engine 1 may be configured to monitor a plurality of parameters of the turbocharger 10 during operation of the internal combustion engine 1. For example, the controller 5 may be configured to receive data indicative of one or more of: a boost pressure of the turbocharger 10, a temperature of the turbocharger 10, an error code indicative of the operational state of the turbocharger 10, a pressure of the lubricant supplied to the turbocharger 10, a speed of the turbocharger 10, a vibration signal from the turbocharger 10, and an intake depression for the turbocharger 10. The fault mode of the turbocharger 10 may be determined by comparing one or more of the above parameters to a corresponding threshold value in order to determine a fault in the turbocharger 10 has occurred. By determining the fault mode of the turbocharger 10 based on more than one sensor reading (i.e. based on the turbo boost and another sensor reading), the controller 5 may reduce the risk of incorrectly determining the fault mode resulting from a failure of a sensor associated with the calculation of turbo boost (e.g. a pressure sensor failing). When a fault mode of the turbocharger 10 is determined, the lubricant pressure of the electric lubricant pump 4 may be significantly reduced relative to the predetermined pressure. A significant reduction in lubricant pressure may be possible as the turbocharger 10 is effectively no longer operational. For example, the fault leakage prevention pressure may be no greater than 50 %, 40 %, 30 %, 20 % or 10 % of the predetermined lubricant pressure. In some embodiments, the supply of lubricant to the turbocharger 10 may be shut off entirely in order to prevent leakage of lubricant. For example, when the fault mode is determined, the controller 5 may be configured to close a turbo lubricant valve 8 (as shown in Fig. 1) which may be configured to control the supply of lubricant to the turbocharger 10 in order to prevent the supply of lubricant to the turbocharger 10. As such, the fault mode of the turbocharger 10 may be determined when the controller 5 detects a relatively charge drop in turbo boost (and / or other associated internal combustion engine 1 parameters). The lubricant pressure may be reduced to the fault leakage prevention pressure in such an operating mode in order to prevent or reduce leakage of lubricant into the turbocharger 10 when a fault in the turbocharger 10 is detected. In some embodiments, determining whether the internal combustion engine 1 is operating in a low demand operating mode may comprise determining whether the internal combustion engine 1 is operating in a component fault mode. The component fault mode may be determined based on whether the turbo boost is below a second boost threshold. The second boost threshold may be greater than the first boost threshold (of the fault mode for the turbocharger 10). The component fault mode may be determined when the controller 5 detects that there may be a fault with a component of the internal combustion engine (not including the turbocharger 10). Such a fault with a component of the internal combustion engine 1 may result in the turbo boost dropping below a second boost threshold. The second boost threshold may be greater than the first threshold. That is to say, a component fault may be detected even when the turbocharger 10 is still operational (e.g. the turbo boost is reduced, but still greater than zero). If the internal combustion engine 1 is determined to be operating in the component fault mode, the engine speed of the internal combustion engine 1 may be limited to no greater than a first speed threshold. If the internal combustion engine 1 is determined to be operating in the component fault mode, a power output of the internal combustion engine 1 may be limited to no greater than a first power output threshold. Furthermore, if the internal combustion engine 1 is determined to be operating in the component fault mode, the electrical power supplied to the electrical lubricant pump 4 may be limited such that the lubricant pressure is no greater than the leakage prevention pressure. As such, in the component fault mode, the internal combustion engine 1 may be operated with a reduced speed / power output of the internal combustion engine 1 to allow the internal combustion engine 1 / machine to reach a state / location where further maintenance may be performed on the internal combustion engine 1 / machine. Reduced speed / power operation of the internal combustion engine 1 may be determined by the controller 5 to reduce the risk of further faults resulting from the component fault. While the internal combustion engine 1 is being operated with reduced speed / reduced power output, the lubricant pressure supplied to the turbocharger 10 may also be reduced in order to reduce or prevent leakage of lubricant in the turbocharger 10 due to the reduction in turbo boost. In some embodiments, the component fault mode may be determined based on whether the turbo boost is below a second boost threshold and the controller 5 the internal combustion engine 1 detecting a fault with a component of the internal combustion engine 1. By relying on additional sensor readings, the controller 5 may reduce the occurrence of false positives. As will be appreciated by the skilled person, the controller 5 of the internal combustion engine 1 may be configured to monitor a plurality of parameters of the internal combustion engine 1 during operation of the internal combustion engine. For example, the controller 5 may be configured to receive data indicative of one or more of: a crankcase pressure, a temperature of the internal combustion engine 1, a vibration sensor associated with the internal combustion engine, a sensor associated with an aftertreatments system of the internal combustion engine 1 and the like. Accordingly, a component fault mode may be determined by the controller 5, resulting in the internal combustion engine 1 operating in a reduced power output / reduced engine speed mode. To reflect this operating mode, the controller 5 may also reduce the lubricant pressure to no greater than the leakage prevention pressure in order to reduce or prevent lubricant leakage. In some embodiments where the controller 5 determines whether the internal combustion engine 1 is operating in a low demand operating mode, the controller 5 determines whether the internal combustion engine 1 is operating in an extended low demand operating mode. In the extended low demand operating mode, the turbo boost may be below a third boost threshold for a period of time greater than a time threshold. As such, the extended low demand operating mode may be indicative of operation of the turbocharger 10 with low boost for an extended period of time, such that leakage of lubricant may start to occur. To address this, in the extended low demand operating mode, the controller 5 may be configured to cause the electrical power supplied the electrical lubricant pump 4 to be limited such that the lubricant pressure is no greater than an idle speed pressure which is lower than the predetermined pressure. As such, in the extended low demand operating mode the lubricant pressure may be reduced relative to the predetermined pressure of the normal operating mode. In some embodiments, determining whether the internal combustion engine is operating in the extended low demand operating mode comprises determining whether the turbo boost is below the third boost threshold and that the engine speed of the internal combustion engine 1 is below a low speed threshold for a period of time greater than the time threshold. For example, a low speed threshold for an internal combustion engine 1 may be no greater than about 110 %, or no greater than about 105 % of an idle speed of the internal combustion engine 1. For example, the time threshold may be at least 1 minute, 5 minutes, 10 minutes, 20 minutes, 30 minutes, or 1 hour. As such, if the internal combustion engine 1 is operated at e.g. an idle speed for an extended period of time, the lubricant pressure supplied to the turbocharger 10 may be reduced (relative to the predetermined lubricant pressure of the normal operation mode) to reduce or prevent lubricant leakage. In some embodiments, the controller 5 may determine that the internal combustion engine is operating in the low demand operating mode when the turbo boost is below the third boost threshold. The controller may then distinguish between the extended low demand operating mode, the component fault mode and the fault mode based on the turbo boost. For example, in some embodiments, the third boost threshold may be greater than the second boost threshold, and the second boost threshold may be greater than the first boost threshold. As such, when the turbo boost is between the second and third boost thresholds, the internal combustion engine 1 may be operating in the extended low demand operating mode. When the turbo boost is between the first and second boost thresholds, the internal combustion engine 1 may be operating in the component fault mode. When the turbo boost is below the first boost threshold, the internal combustion engine 1 may be operating in the fault mode. In such an embodiment, the controller 5 may distinguish between the three sub-modes. In other embodiments, the controller 5 may distinguish between only two of the sub-modes, or the low demand operating mode may be based on only one of the sub-modes. Fig. 4 shows a graph of a relationship between lubricant pressure and engine speed of the internal combustion 1 for the normal operating mode and the extended low demand operating mode according to this disclosure. For the internal combustion engine 1 of Fig. 4, an idle speed of the internal combustion engine 1 may be about 1200 rpm. It will be appreciated that below an idle speed of the internal combustion engine 1, the turbocharger 10 may not be operational and so the method according to this disclosure may selectively be not implemented. That is to say, methods according to this disclosure may only be implemented while the internal combustion engine 1 is operating at an engine speed of at least an idle speed. Industrial applicability According to this disclosure, a method of controlling an internal combustion, a controller for an internal combustion engine 1, an internal combustion engine 1 and a machine are provided. The machine may be a generator or a work vehicle such as an excavator, a wheel loader, a dozer, a telehandler, a tractor and the like. The internal combustion engine 1 comprises a turbocharger 10 which is supplied with lubricant from an electric lubricant pump 4. According to embodiments of this disclosure, during normal operation of the internal combustion engine 1, lubricant may be supplied to the turbocharger 10 at a predetermined lubricant pressure. During a low demand operating mode (which may be a fault mode of the turbocharger, a component fault mode, or an extended low demand operating mode) of the internal combustion engine 1, the lubricant pressure may be reduced to a leakage prevention pressure which is lower than the predetermined lubricant pressure in order to reduce or prevent leakage of lubricant into the compressor and / or turbine of the turbocharger. Such control of the lubricant pressure may be possible as the lubricant is pressurised using an electric lubricant pump where the pumping power may be controlled independently of the operation of the internal combustion engine 1.

Claims

1. A method of controlling an internal combustion engine comprising an electric lubricant pump and a turbocharger, comprising:5 determining whether the internal combustion engine is operating in a normaloperating mode where a turbo boost of the turbocharger is above a boost threshold or a low demand operating mode where the turbo boost is no greater than the boost threshold, wherein when it is determined that the internal combustion engine isoperating in the normal operating mode the method comprises supplying electrical10 power to the electric lubricant pump to cause lubricant to be supplied to theturbocharger at a pressure of at least a predetermined lubricant pressure; and wherein when it is determined that the internal combustion engine is operating in the low demand operating mode, the method comprises reducing the electrical power supplied to the electric lubricant pump to reduce the lubricant15 pressure to a leakage prevention pressure which is lower than the predeterminedlubricant pressure.

2. A method according to claim 1, whereinwhen operating in the normal operating mode, electrical power is supplied to the20 electric lubricant pump to cause lubricant to be supplied to the internal combustion engine at a pressure of at least a predetermined lubricant pressure, wherein the predetermined lubricant pressure is controlled based on an engine speed of the internal combustion engine.25 3. A method according to claim 1 or claim 2, whereinwhen operating in the low demand operating mode, electrical power is supplied to the electric lubricant pump to cause lubricant to be supplied to the internal combustion engine at the leakage prevention pressure, wherein the leakage prevention pressure is controlled based on the engine speed of the internal combustion engine.

304. A method according to any of claims 1 to 3, whereindetermining whether the internal combustion engine is operating in a low demand operating mode comprises:determining whether the turbocharger is operating in a fault mode when35 the turbo boost is below a first boost threshold;wherein if the turbocharger is determined to be operating in a fault mode, the method further comprises reducing the lubricant pressure to a fault leakage prevention pressure which is lower than the leakage prevention pressure.5 5. A method according to claim 4, whereindetermining whether the turbocharger is operating in a fault mode comprises determining whether the turbo boost is below a first boost threshold and determining whether a turbo speed of the turbocharger is below an operational speed threshold.10 6. A method according to claim 4 or claim 5, whereinif the turbocharger is determined to be operating in a fault mode, the method further comprises closing a turbo lubricant valve which is configured to control the supply of lubricant to the turbocharger in order to prevent the supply of lubricant to the turbocharger.15 7. A method according to any of claims 1 to 6, whereindetermining whether the internal combustion engine is operating in a low demand operating mode comprises:determining whether the internal combustion engine is operating in a component fault mode based on whether the turbo boost is below a second boost threshold, 20 wherein if the internal combustion engine is determined to be operating in acomponent fault mode, the method further comprises:limiting the engine speed of the internal combustion engine to no greater than a first speed threshold and / or limiting a power output of the internal combustion engine to no greater than a first power output threshold; and25 limiting the electrical power supplied the electrical lubricant pump such that thelubricant pressure is no greater than the leakage prevention pressure.

8. A method according to claim 7, whereindetermining whether the internal combustion engine is operating in the component 30 fault mode comprises determining whether the turbo boost is below a second boost threshold and a controller of the internal combustion engine detects a fault with a component of the internal combustion engine.

9. A method according to any of claims 1 to 8, whereindetermining whether the internal combustion engine is operating in a low demandoperating mode comprises:determining whether the internal combustion engine is operating in an extended low demand operating mode when the turbo boost is below a third boost threshold for a period5 of time greater than a time threshold,wherein if the internal combustion engine is determined to be operating in an extended low demand operating mode, the method further comprises:limiting the electrical power supplied the electrical lubricant pump such that thelubricant pressure is no greater than an idle speed pressure which is lower than the10 predetermined pressure.1510. A method according to claim 9, whereindetermining whether the internal combustion engine is operating in an extended low demand operating mode comprises determining whether the turbo boost is below the third boost threshold and a controller of the internal combustion engine determines that an engine speed of the internal combustion engine is below a low speed threshold for a period of time greater than the time threshold.

11. A method according to claim 9 or 10 when dependent on at least claims 4 and 7,20 whereinthe third boost threshold is greater than the second boost threshold, and the second boost threshold is greater than the first boost threshold.

12. A method according to any of claims 1 to 11, wherein25 the predetermined lubricant pressure is at least 200 kPa.

13. A method according to any of claims 1 to 12, wherein the leakage prevention pressure is no greater than 80 % of the predetermined lubricant pressure.3014. A controller for an internal combustion engine comprising an electric lubricant pump and a turbocharger, the controller configured to:determine whether the internal combustion engine is operating in a normal operating mode where a turbo boost of the turbocharger is above a boost threshold, or alow demand operating mode where the turbo boost of the turbocharger is no greater than the boost threshold;wherein when the controller determines that the internal combustion engine is operating in the normal operating mode, the controller is configured to cause5 electrical power to be supplied to the electric lubricant pump to cause lubricant to besupplied to the turbocharger at a pressure of at least a predetermined lubricant pressure; andwhen the controller determines that the internal combustion engine is operating in the low demand operating mode, the controller is configured to reduce10 the electrical power supplied to the electric lubricant pump to reduce the lubricantpressure to a leakage prevention pressure which is lower than the predetermined lubricant pressure.1515. A controller according to claim 14, whereinwhere the controller is configured to determine whether the internal combustion engine is operating in a low demand operating mode, the controller is configured to:determine whether the turbocharger is operating in a fault mode when the turbo boost is below a first boost threshold;wherein if the controller determines the turbocharger is operating in a fault mode, the controller is configured to reduce the lubricant pressure to a fault leakage prevention pressure which is lower than the leakage prevention pressure.

16. A controller according to claim 15, whereinif the controller determines the turbocharger is operating in the fault mode, the25 controller is configured to cause a turbo lubricant valve of the internal combustion engine to be closed to prevent the supply of lubricant to the turbocharger.

17. A controller according to according to any of claims 14 to 16, wherein where the controller is configured to determine whether the internal combustion30 engine is operating in a low demand operating mode, the controller is configured to: determine whether the internal combustion engine is operating in a component fault mode based on whether the turbo boost is below a second boost threshold,wherein the controller determines the internal combustion engine is operating in the component fault mode, the controller is configured to:cause an engine speed of the internal combustion engine to be limited to no greater than a first speed threshold and / or to cause a power output of the internal combustion engine to be limited to no greater than a first power output threshold; and5 cause the electrical power supplied the electrical lubricant pump to be limited suchthat the lubricant pressure is no greater than the leakage prevention pressure.

18. A controller according to any of claims 14 to 17, whereinwhere the controller is configured to determine whether the internal combustion10 engine is operating in a low demand operating mode, the controller is configured to:determine whether the internal combustion engine is operating in an extended low demand operating mode when the turbo boost is below a third boost threshold for a period of time greater than a time threshold.wherein if the controller determines the internal combustion engine is operating in15 the extended low demand operating mode, the controller is configured to:cause the electrical power supplied the electrical lubricant pump to be limited such that the lubricant pressure is no greater than an idle speed pressure which is lower than the predetermined pressure.20 19. A controller according to claim 18 when dependent on at least claims 15 and 17,whereinthe third boost threshold is greater than the second boost threshold, and the second boost threshold is greater than the first boost threshold.25 20. An internal combustion engine for a machine, the internal combustion enginecomprising:a controller according to any of claims 14 to 19;a turbocharger; andan electric lubricant pump configured to supply lubricant to the turbocharger.30

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