GB2506134A

GB2506134A - Priming engine lubricant pressure before starting the engine

Info

Publication number: GB2506134A
Application number: GB201216819A
Authority: GB
Inventors: Richard Cooper; Thomas Gens; Mark Blackburn; David Milam; Adam Dudley; Stephen Bird; Peter Ladlow
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2012-09-20
Filing date: 2012-09-20
Publication date: 2014-03-26
Anticipated expiration: 2032-09-20
Also published as: GB2506134B; GB201216819D0; GB2506134C; JP2014062546A

Abstract

Components, eg a turbocharger, of an engine may be damaged when the engine is started whilst it is not sufficiently lubricated. The disclosed method and apparatus may facilitate improved protection against such damage to the components of an engine by priming the engine lubrication pressure for a period of time before starting the engine if, when an engine start is demanded by the operator, a measured engine lubricant pressure is below a threshold value. This may result in better lubrication of the engine before it is turned on, and consequently the engine components may have an improved lifespan. Priming the engine lubrication pressure may be performed by cranking the engine with the fuel injectors turned off. The lubricant pressure threshold may be determined by considering at least one of barometric pressure, engine coolant temperature and air inlet temperature. Engine speed may be limited for a period after starting.

Description

Apparatus and method for starting an engine The present disclosure relates to an apparatus and method for starting an engine.

Background

Various moving parts in an internal combustion engine and in devices that are peripheral to the internal combustion engine, such as a turbocharger, may require lubrication in order to reduce friction and heat, thereby prolonging the life of the parts. Whilst the engine is operating, lubricant may be circulated around the engine and its peripheral devices by various means, for example by pumps.

However, whilst the engine is turned off, the means of pumping lubricant may not operate, and the lubricant may gradually flow away from the moving parts that need lubricating and collect in the lubricant sump.

Consequently, upon starting an engine which has been turned of f for a long period of time, the moving parts may not initially be well lubricated. After the engine has turned on, lubricant pressure within the engine system may gradually increase, for example as the lubricant pumps begin to operate. As the lubricant pressure increases, it may reach a level at which the moving parts of the engine and its peripheral devices may be well lubricated.

Before the engine and its peripheral devices are well lubricated, they may be susceptible to damage caused by friction and heat. If, f or example, a rapid acceleration of the engine is demanded by the user soon after start-up and before the engine and its peripheral devices are properly lubricated, permanent damage may be inflicted on the poorly lubricated parts of the engine and peripheral devices.

For example, high-pressure turbochargers may require well lubricated parts, like the bearings, and may be prone to failures caused by poor lubrication. If high loads are applied to the engine, or high speeds demanded of the engine, soon after start up and before the turbocharger is properly lubricated, the turbocharger may be permanently damaged very quickly, for example within about 10 seconds.

US patent application no. 2010/0018805 describes a method of controlling lubrication of an internal combustion engine, wherein battery powered oil pumps may inject lubricating oil into the engine cylinders before the engine is started.

Injection of the oil may pre-emptively commence at various periodic times depending on the engine start-up history and ignition demand timing.

By periodically commencing pre-emptive oil injection, power may gradually be drained from the battery to the extent that if a number of pre-emptive oil injection events take place before an ignition demand, the battery may be entirely drained and starting the engine may no longer be possible.

S uinmary The present disclosure provides: a method of starting an engine, the method comprising the steps of: a) after an engine start is demanded, if an engine lubricant pressure is below a lubricant pressure threshold, priming the engine lubricant pressure for a period of time; and b) after the period of priming the engine lubricant pressure, starting the engine.

The present disclosure also provides: a controller for starting an engine, the controller being arranged: after an engine start is demanded, if an engine lubricant pressure is below a lubricant pressure threshold, to prime the engine lubricant pressure for a period of time; and after the period of priming the engine lubricant pressure, to start the engine.

Figures

Embodiments of the present disclosure shall now be

described, by way of example only, with reference to the following drawings, in which: Figure 1 shows a schematic drawing of an engine unit; Figure 2 shows method steps that may be used when turning on the engine unit of Figure 1; Figure 3 shows method steps that may be used after turning on the engine unit of Figure 1; and Figure 4 shows an example vehicle within which the engine unit shown in Figure 1 may be used.

Detailed description

Figure 1 shows an example of an engine 110, for example an internal combustion engine. The starting of the engine 110 may be controlled by a controller 120. The controller 120 receives an engine start demand signal 161, which might be generated by, for example, an engine operator turning an ignition key, or by any other means by which the start of the engine may be demanded. upon receipt of an engine start demand signal 161, the controller 120 may begin an engine start-up routine.

Engine start-up may be executed by any means well known to the skilled person. For example, an engine start demand may cause a starter motor to begin cranking, or turning over, the engine 110. If the controller 120 turns on the engine fuel injectors 140 using the fuel injector control signal 172, fuel will be injected into the cylinders of the engine 110. Injection of fuel into the cylinders during engine cranking will result in combustion within the cylinders and the engine 110 will turn on. If the controller 120 keeps the engine fuel injectors 140 turned off, combustion in the cylinders will not occur and engine cranking will continue.

The engine 110 may be lubricated with, for example, oil, and the controller 120 may consider the measured engine lubricant pressure 162 when controlling the start-up of the engine 110. The controller 120 may also receive measurements of the barometric pressure 163, the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166, some or all of which may be considered when controlling the start-up of the engine 110. Any type of sensors which would be well known to the skilled person may be used to determine these readings.

In the example shown in Figure 1, a turbocharger 150 is arranged as a peripheral device to the engine 110. Parts of -5-.

the turbocharger 150 may also be lubricated by the same lubrication system used for lubrication of the engine 110.

Consequently, the measured engine lubricant pressure 162 may also be indicative of the lubricant pressure for the turbocharger 150. The turbocharger 150 is intended merely to be an example of a peripheral device requiring lubrication that may be used with the engine 110. The engine 110 may alternatively be a normally aspirated engine without a turbocharger. Additional or alternative peripheral devices requiring lubrication may also be used with the engine 110.

Figure 2 shows an example method of starting the engine 110 in accordance with an embodiment of the present disclosure.

Upon receipt of a demand to start the engine 110, it may be determined in Step 5210 whether or not the measured engine lubricant pressure 162 is less than a lubricant pressure threshold.

If Step 5210 determines that the measured engine lubricant pressure 162 is greater than the lubricant pressure threshold, it may be considered that starting the engine 110 should be safe as the engine 110 and any peripheral devices may be sufficiently lubricated to avoid damage.

Consequently, the control method may proceed to Step S230 and start the engine 110, by, for example, enabling the engine fuel injectors 140 so that cranking of the engine 110 will cause combustion in the engine cylinders.

If Step 5210 determines that the measured engine lubricant pressure 162 is below the lubricant pressure threshold, it may be considered that starting the engine 110 might damage the engine 110 and any peripheral devices due to insufficient lubrication. In this case, the control method may proceed to Step 5220 for lubricant pressure priming.

Lubricant pressure priming might be carried out using a number of different techniques. For example, an electrical lubricant pump(s) in the lubrication system of the engine might be operated by drawing power from an engine battery. Alternatively, the engine 110 might be turned over, or cranked, and mechanical linkages between the crankshaft and a mechanical lubricant pump(s) may drive the mechanical lubricant pump(s) to increase the lubricant pressure. Alternatively, a small electrical priming pump might be used in addition to the mechanical pump(s).

However, use of an electrical pump(s), either on its own or in combination with a mechanical pump(s), may increase costs in comparison to using just a mechanical pump(s) Therefore, it might be preferable to prime the engine lubricant pressure by cranking the engine 110 in order to operate the mechanically driven lubricant pump(s).

Cranking of the engine 110 may be performed by the controller 120 by disabling the engine fuel injectors 140 by setting the fuel injector control signal 172 accordingly so that when the engine 110 is cranked in response to an engine start demand, a full start of the engine 110 is prevented and only engine cranking occurs.

The lubricant pressure threshold may be set to a level below which it is considered that the engine 110, and any lubricated peripheral devices, for example the turbocharger 150, may be damaged upon starting the engine 110 as a consequence of poor lubrication. The lubricant pressure threshold may be fixed at a predetermined value that is considered to be suitable for the size and type of the engine 110 and peripheral devices, for example at a value between 5OkPaG to l5OkPaG (i.e. SOkPa-l5OkPa gauge pressure), such as 8OkPaG.

Alternatively, the lubricant pressure threshold may be determined by considering the operating conditions of the engine 110 at the time at which engine start is demanded.

Those operating conditions might include, but are not limited to, at least one of barometric pressure 163, engine coolant temperature 164, air inlet temperature 165 and air temperature in the air intake manifold 166.

When the barometric pressure is low, for example because the engine 110 is at a high altitude, lubrication of the engine and any peripheral components might be expected to be more difficult, and therefore be of more concern.

Consequently, the lubricant pressure threshold may be set higher for low barometric pressures, in order to improve the probability of good lubrication before the engine 110 is started.

Conversely, at high barometric pressures, lubrication of the engine 110 and any peripheral components might be expected to be relatively straightforward, and so ensuring that a high lubricant pressure is achieved before starting the engine 110 might be of less concern. Therefore, the lubricant pressure threshold may be set lower for high barometric pressures so that the user is less likely to be significantly obstructed by an extended period of lubricant pressure priming.

The lubricant pressure threshold may therefore be set at a S level that is inversely proportional to barometric pressure.

Likewise, at low temperatures, lubrication of the engine 110 and any peripheral components might again be expected to be more difficult, and therefore be of more concern.

Consequently, the lubricant pressure threshold may be set higher for low temperatures, in order to improve the probability of good lubrication before the engine 110 is started. Conversely, the lubricant pressure threshold might be set lower for high temperatures, so that the user is not significantly obstructed by an extended period of lubricant pressure priming when there is less concern about lubrication pressure.

The lubricant pressure threshold may therefore be set at a level that is inversely proportional to temperature.

When considering temperatures, the coldest of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166 may be used to determine the lubricant pressure threshold. This may reduce the probability that the lubricant pressure threshold is set to a dangerously low level by an erroneously high temperature measurement.

The lubricant pressure threshold may also be determined by considering the barometric pressure 163 and the minimum of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166. This may be achieved using, for example, a look-up table or a map with two inputs, the barometric pressure and the temperature, and one output, the lubricant pressure threshold. In this way, a lubricant pressure threshold may be set that most effectively balances the conflicting requirements of improving starting safety for the engine 110 and minimising the interference of lubricant pressure priming for the operator.

The engine lubricant pressure may rise rapidly as a consequence of the operation of the lubricant pump(s) during priming. The measured engine lubricant pressure 162 may be monitored during lubricant pressure priming in Step S222 and once the measured engine lubricant pressure 162 has exceeded the lubricant pressure threshold, the control method may proceed to Step S230 and the engine 110 may be started. The engine 110 may be started by the controller 120 setting the fuel injector control signal 172 to enable the engine fuel injectors 140, which will initiate combustion within the cylinders of the engine 110, or by any other technique that is known to the skilled person.

Alternatively, in Step 5224, the period of time during which lubricant pressure priming has been taking place may be monitored and the engine 110 may be started after lubricant pressure priming has taken place for a predetermined period of time -the lubricant pressure priming time threshold.

This threshold may be a fixed period of time, for example a time period of between 5 to 25 seconds, such as 10 seconds, or it may be set based on the operating conditions of the engine 110 at the time of the engine start demand. Those -10 -operating conditions might include, but are not limited to, at least one of barometric pressure 163, engine coolant temperature 164, air inlet temperature 165 and air temperature in the air intake manifold 166.

When the barometric pressure is low, for example because the engine 110 is at a high altitude, it may take longer for the lubricant to reach a pressure at which the engine 110 may be started without causing damage. Consequently, the lubricant pressure priming time threshold may be set to be longer for low barometric pressures, so that more time is allowed for the engine lubricant pressure to reach a safe level.

Conversely, at high barometric pressures, it may be expected to be relatively straightforward for the lubricant to reach a pressure at which the engine 110 may be started without causing damage. Therefore, priming of the lubricant pressure before starting the engine 110 might be of less concern. Consequently, the lubricant pressure priming time threshold may be set to be a shorter period of time so that the user is not significantly obstructed by an extended period of lubricant pressure priming.

The lubricant pressure priming time threshold may therefore be inversely proportional to barometric pressure.

Likewise, at low temperatures, it may take longer for the engine lubricant pressure to reach a pressure at which the engine 110 may be started without causing damage.

Therefore, the lubricant pressure priming time threshold may be set longer for low temperatures, so that more time is allowed for the engine lubricant pressure to increase to a -11 -safe level. Conversely, the lubricant pressure priming time threshold may be set shorter for high temperatures, so that the user is not significantly obstructed by an extended period of lubricant pressure priming when there is less concern about engine lubricant pressure.

The lubricant pressure priming time threshold may therefore be inversely proportional to temperature.

When considering temperature, the coldest of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166 may be used to determine the lubricant pressure priming time threshold. This may reduce the probability that the lubricant pressure priming time threshold is set to a dangerously short period of time by an erroneously high temperature measurement The lubricant pressure priming time threshold may also be determined by considering the barometric pressure 163 and the minimum of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166. This may be achieved using, for example, a look-up table or a map with two inputs, the barometric pressure and the temperature, and one output, the lubricant pressure priming time threshold.

In this way, a lubricant pressure priming time threshold may be set that most effectively balances the conflicting requirements of improving starting safety for the engine 110 and minimising the interference of lubricant pressure priming for the operator.

-12 -Both of Steps 5222 and 5224 may be implemented as shown in Figure 2 and lubricant pressure priming may continue until the measured engine lubricant pressure 162 exceeds the lubricant pressure threshold, or until lubricant pressure S priming has taken place for a period of time exceeding the lubricant pressure priming time threshold, whichever happens first. In most circumstances, it might be expected that the measured engine lubricant pressure 162 will exceed the lubricant pressure threshold very quickly, for example within about 3 seconds. When the measured engine lubricant pressure 162 stays below the lubricant pressure threshold after lubricant pressure priming has taken place for a period of time exceeding the lubricant pressure priming time threshold, it may usually be expected that the engine lubricant pressure is sufficiently high, but that the measured engine lubricant pressure 162 is erroneous due, for example, to a faulty sensor.

Lubricant pressure priming cannot take place for an unlimited period of time or else the engine battery might become drained by cranking the engine 110, or the operator of the engine 110 might become frustrated. In such cases, it might be preferable to start the engine 110 after exceeding the lubricant pressure priming time threshold in spite of the measured engine lubricant pressure 162 being below the lubricant pressure threshold and trust that the lubricant pressure is in fact sufficiently high to prevent damage to the engine 110 and peripheral devices. A warning indicator for the operator, for example a warning light or sound, may also be turned on to alert the operator that the engine 110 has been turned on even though the measured engine lubricant pressure 162 is low.

-13 -Once it has been determined that the engine 110 should be started, for example if the measured engine lubricant pressure 162 exceeds the lubricant pressure threshold, starting of the engine 110 in Step 5230 may be delayed by a delay period, during which time lubricant pressure priming will continue. The lubricant pressure sensor used to determine the measured engine lubricant pressure 162 may be located close to the lubricant filter of the engine 110. An increase in the measured engine lubricant pressure 162 at the lubricant pressure sensor might take some time to result in proper lubrication throughout the lubrication system, particularly when a number of peripheral devices, such as a turbocharger, are connected to the lubrication system. By introducing a delay time between the lubricant pressure sensor indicating an engine lubricant pressure in excess of the lubricant pressure threshold and the starting of the engine 110 in Step 230, the engine 110 and peripheral devices are more likely to be well lubricated before the engine 110 is started.

The delay time may be a predetermined time period, set on the basis of the size and type of the engine 110 and peripheral devices. The time period may be set, for example, to a period of up to 10 seconds, such as 2 seconds.

Alternatively, it may be determined by considering the operating conditions of the engine 110. Those operating conditions might include, but are not limited to, at least one of barometric pressure 163, engine coolant temperature 164, air inlet temperature 165 and air temperature in the air intake manifold 166.

-14 -The delay time may be set by considering the barometric pressure 163, or the temperature, or both, in the same way in which those engine operating conditions are used to set S the lubricant pressure threshold and the lubricant pressure priming time threshold, as explained above. High barometric pressures and/or high temperatures may result in a shorter delay time being set, and low barometric pressures and/or low temperatures may result in a longer delay time being set.

After the engine 110 has been turned on, at some later time the engine 110 may be turned off by the operator. When the engine 110 is initially turned on, the engine 110 and its peripheral devices may be well lubricated by virtue of lubricant pressure priming. During operation of the engine 110, engine lubricant pressure may also have been kept high by virtue of the lubricant pump(s) and a good level of lubrication consequently maintained. After turning of f the engine 110, the engine lubricant pressure may gradually decrease and the engine 110 and its peripheral devices may become gradually less well lubricated. However, for a period of time after turning off the engine 110, the engine lubricant pressure and the lubrication of the engine 110 may still be sufficient for the engine 110 to be turned back on without any lubricant pressure priming required.

If an engine start demand is received within this period of time after the engine 110 is turned off, it may be arranged that the engine 110 is immediately restarted. By doing so, computation and time may be saved, and it may be ensured that the operator of the engine 110 is not inconvenienced by -15 -an erroneous decision to begin lubricant pressure priming, when it is apparent that it will not actually be required.

The period of time after turning of f the engine 110 during which the engine 110 may be immediately restarted (the turn-off time period) may be a fixed, predetermined time period, for example up to 20 minutes after turning off the engine 110, such as 15 minutes after turning of f the engine 110.

The turn-off time period may be set with consideration to the size and type of the engine 110 and peripheral components. If an engine start demand signal is received after the turn-off time period has elapsed, the start-up method described earlier and shown in Figure 2 may be executed by proceeding to Step 3210.

After the engine has been started in Step 3230, the engine speed may be limited for a period of time in accordance with the steps shown in Figure 3. The speed may, for example, be limited to a low-idle speed, or to a tuneable engine speed threshold if that is lower.

Damage to the engine 110 and peripheral devices, such as the turbocharger 150, caused by poor lubrication is likely to be greater at higher engine speeds. During low speed operation of the engine 110, the engine lubricant pressure may rise quickly from that achieved by lubricant pressure priming, since the lubricant pumps should be driven with a greater amount of power. Therefore, low speed operation for a period of time after starting the engine 110 should result in better lubrication of the engine 110 and any peripheral devices, so that when the engine 110 is allowed to operate freely at higher speeds, damage is less likely.

-16 -Consequently, by imposing an engine speed limit after engine start-up, the engine 110, and any peripheral devices, may be protected from damage that might otherwise be caused at high engine speeds.

After the engine 110 has been started in Step 5230, it may be determined in Step S320 whether or not the measured engine lubricant pressure 162 is less than a second lubricant pressure threshold. If the measured engine lubricant pressure 162 is low after starting the engine 110$ it might be expected that the engine 110 and any peripheral devices will not be sufficiently lubricated to protect against damage caused by high engine speeds. Conversely, if the measured engine lubricant pressure 162 is high after starting the engine 110, it might be expected that the engine 110 and any peripheral devices will be sufficiently lubricated to protect against damage caused by high engine speeds.

If Step 5320 determines that the measured engine lubricant pressure 162 is greater than the second lubricant pressure threshold, it may be considered that allowing the engine to operate normally (potentially at high speeds) should be safe as the engine 110 and any peripheral devices may be sufficiently lubricated to avoid damage. Consequently, the control method may proceed to Step 5340 and allow the engine to operate normally.

If Step S320 determines that the measured engine lubricant pressure 162 is below the second lubricant pressure threshold, it may be considered that if the engine 110 runs at high speeds, the engine 110 and any peripheral devices -17 -might be damaged. In this case, the control method may proceed to Step S330, where the engine speed is limited.

The second lubricant pressure threshold may be set to a level below which it is considered that the engine 110, and any lubricated peripheral devices, for example the turbocharger 150, may be damaged if the engine 110 is allowed to operate at high speeds. The second lubricant threshold level may be fixed at a predetermined value that is considered to be suitable for the size and type of engine and peripheral devices, for example at a value between lOOkPaG -300kPaG (i.e. lOOkPa-300kPa gauge pressure), such as 150 kPaG.

Alternatively, the second lubricant pressure threshold may be determined by considering the operating conditions of the engine 110. Those operating conditions might include, but are not limited to, at least one of barometric pressure 163, engine coolant temperature 164, air inlet temperature 165 and air temperature in the air intake manifold 166.

When the barometric pressure is low, for example because the engine 110 is at a high altitude, lubrication of the engine and any peripheral devices might be expected to be more difficult, and therefore be of more concern. Consequently, the second lubricant pressure threshold may be set higher for low barometric pressures, in order to improve the probability of good lubrication before the engine 110 is allowed to operate at higher speeds.

Conversely, at high barometric pressures, lubrication of the engine 110 and any peripheral devices might be expected to -18 -be relatively straightforward, and so ensuring that a high engine lubricant pressure is achieved might be of less concern. Therefore, the second lubricant pressure threshold may be set lower for high barometric pressures so that the user is less likely to be significantly obstructed by an extended period of engine speed restriction.

The second lubricant pressure threshold may therefore be set at a level that is inversely proportional to barometric pressure.

Consequently, the second lubricant pressure threshold may be set higher for low temperatures, in order to improve the probability of good lubrication before the engine 110 is allowed to operate at higher speeds. Conversely, the second lubricant pressure threshold might be set lower for high temperatures, so that the user is not significantly obstructed by an extended period of engine speed restriction when there is less concern about lubrication pressure.

The second lubricant pressure threshold may therefore be set at a level that is inversely proportional to temperature.

When considering temperatures, the coldest of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166 may be used to determine the second lubricant pressure threshold. This may reduce the probability that the second lubricant pressure threshold is set to a -19 -dangerously low level by an erroneously high temperature measurement.

The second lubricant pressure threshold may also be determined by considering the barometric pressure 163 and the minimum of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166. This may be achieved using, for example, a look-up table or a map with two inputs, the barometric pressure and the temperature, and one output, the second lubricant pressure threshold. In this way, a second lubricant pressure threshold may be set that most effectively balances the conflicting requirements of improving safety for the engine 110 and minimising the interference of engine speed restriction for the operator.

In Step 5330, the maximum engine speed is limited to a low speed, for example a low-idling speed, or to a tuneable engine speed threshold if that is lower. The skilled person will appreciate that speed limitation may be achieved in a number of different ways, for example using a mechanical governor, or by the controller 120.

The maximum engine speed may be limited after start-up until either the measured engine lubricant pressure 162 exceeds the second lubricant pressure threshold (at which time it might be expected that the engine 110 and any peripheral components will be well lubricated), or until the time after starting the engine 110 (i.e. the period of time during which maximum engine speed has been limited) has exceeded an engine speed limitation time threshold, whichever is happens sooner. In most circumstances, it might be expected that -20 -the measured engine lubricant pressure 162 will exceed the second lubricant pressure threshold very quickly after starting the engine 110, for example within about 2 seconds.

When the measured engine lubricant pressure 162 stays below the second lubricant pressure threshold after the engine 110 has been turned on for a period of time exceeding the engine speed limitation time threshold, it may usually be expected that the engine lubricant pressure is sufficiently high, but that the measured engine lubricant pressure 162 is erroneous due, for example, to a faulty sensor.

Limitation of the maximum engine speed cannot take place for an unlimited period of time without significantly interfering with the operation of the engine 110 and causing great inconvenience to the operator. In such cases, it is preferable to allow the engine 110 to operate normally after exceeding the engine speed limitation time threshold, in spite of the measured engine lubricant pressure 162 being below the second lubricant pressure threshold and trust that the engine lubricant pressure is in fact sufficiently high to prevent damage to the engine 110 and peripheral devices.

A warning indicator for the operator, for example a warning light or sound, may also be turned on to alert the operator that the measured engine lubricant pressure 162 is low when the engine is allowed to operate normally.

To this end, as shown in Figure 3, during maximum engine speed limitation, the measured engine lubricant pressure 162 may be compared to the second lubricant pressure threshold in Step 5332. If the measured engine lubricant pressure 162 has exceeded the second lubricant pressure threshold, the control method may progress to Step S340, where the engine -21 -speed limit is removed so that the engine 110 can operate normally.

If it is determined in Step S332 that the measured engine lubricant pressure 162 is below the second lubricant pressure threshold, the control method may progress to Step S334, where it is determined if the engine speed limitation time threshold has been exceeded. If the amount of time since engine start is less than the engine speed limitation time threshold, the control method may return to Step S332.

However, if the amount of time since engine start exceeds the engine speed limitation time threshold, the control method may progress to Step 5340, where the engine speed limit is removed so that the engine 110 can operate normally.

In this way, maximum engine speed may be limited after starting the engine 110 until either the measured engine lubricant pressure 162 exceeds the second lubricant pressure threshold, or until the elapsed time after starting the engine 110 has exceeded the engine speed limitation time threshold, whichever happens sooner.

The engine speed limitation time threshold may be set based on the size and type of the engine 110 and peripheral devices, and might be set to between 5 and 25 seconds, for example 10 seconds. Alternatively, it might be set based on the operating conditions of the engine 110. Those operating conditions might include, but are not limited to, at least one of barometric pressure 163, engine coolant temperature 164, air inlet temperature 165 and air temperature in the air intake manifold 166.

-22 -When the barometric pressure is low, for example because the engine 110 is at a high altitude, it may take longer for the lubricant to reach a pressure at which the engine 110 may operate freely without causing damage. Consequently, the engine speed limitation time threshold may be set longer for low barometric pressures, so that more time is allowed for the engine lubricant pressure to increase.

conversely, at high barometric pressures, it may be expected to be relatively straightforward for the engine lubricant pressure to reach a pressure at which the engine 110 may operate freely without causing damage. Consequently, the engine speed limitation time threshold may be set to be shorter so that the user is not significantly obstructed by an extended period of speed limitation when engine lubrication pressure is of less concern.

The engine speed limitation time threshold may therefore be inversely proportional to barometric pressure.

Likewise, at low temperatures, it may take longer for the engine lubricant pressure to reach a pressure at which the engine 110 may be allowed to operate freely without causing damage. Therefore, the engine speed limitation time threshold may be set longer for low temperatures, so that more time is allowed for the engine lubricant pressure to increase. Conversely, the engine speed limitation time threshold may be set shorter for high temperatures, so that the user is not significantly obstructed by an extended period of speed limitation when the engine lubricant pressure is of less concern.

-23 -The engine speed limitation time threshold may therefore be inversely proportional to temperature.

when considering temperatures, the coldest of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166 may be used to determine the engine speed limitation time threshold. This may reduce the probability that the engine speed limitation time threshold is set to a dangerously short period of time by an erroneously high temperature measurement.

The engine speed limitation time threshold may also be determined by considering the barometric pressure 163 and the minimum of at least two of the engine coolant temperature 164, the air inlet temperature 165 and the air temperature in the air intake manifold 166. This may be achieved using, for example, a look-up table or a map with two inputs, the barometric pressure and the temperature, and one output, the engine speed limitation time threshold. In this way, an engine speed limitation time threshold may be set that most effectively balances the conflicting requirements of improving safety for the engine 110 and minimising the interference of speed limitation for the operator.

In Step 5340, the maximum engine speed limitation may be removed in a number of different ways in order to allow the engine 110 to operate normally.

-24 -For some engine types and machine applications, for example generating sets, it may be desirable to remove the maximum engine speed instantaneously in Step S340. This is because the machine may be effectively inoperable during the period of maximum engine speed limitation, in which case it may be preferable to remove the maximum engine speed limit as quickly as possible in Step S340 so that the machine may be allowed to operate.

For some other engine types and machine applications, for example excavators, the machine may be operable, perhaps with limited function, during the period of maximum engine speed limitation. In this instance, a step change in engine speed caused by an instantaneous removal of the maximum engine speed limitation might cause an unexpected surge in machine power or speed, which could present a risk to the operator or to people or property in the vicinity of the machine.

In order to reduce this risk, in Step S340, the maximum engine speed limit may be removed with a ramping function to restrict the rate of change of engine speed and machine power. Alternatively, the maximum engine speed limit could be held in place until it is determined that the machine will remain at a low speed, idle condition even without the maximum engine speed limit being imposed. At this time, it may be safe to remove the maximum engine speed limitation on the basis that upon removal, the engine 110 will remain at a low speed anyway. The low speed, idle condition may be identified by the controller 120 from the operator reducing the speed demand to a predetermined safe level, or because none of the systems that may cause the engine 110 to operate -25 -at higher speeds or powers are active, for example, the transmission is in neutral, the boom is not being operated etc. Various modifications to the above disclosures will be apparent to those skilled in the art.

For example, if one or more of the various thresholds disclosed above (e.g., the lubricant pressure threshold, the engine speed limitation time threshold, etc) are set by considering the engine operating conditions of the engine 110, such as barometric pressure and/or temperature, the thresholds may not be set to be inversely proportional to the operating conditions. Instead, they may be set to have any form of relationship to the operating conditions, for example they may be proportional to the operating conditions. This may be useful where the barometric pressure and/or temperature is so low that it is expected that the engine 110 will not ever reach high lubrication pressure thresholds during lubricant pressure priming or maximum engine speed restriction. Consequently, the thresholds may be set to be proportionally low so that the operator is not inconvenienced for a prolonged period of time and the engine 110 may be started and/or allowed to operate normally, in the expectation that due to the low barometric pressure and/or temperature, the normal operation of the engine 110 is in any case likely to be very slow for an extended period of time after starting, during which time engine lubricant pressure may gradually rise and improve lubrication before high engine speeds ever occur.

-26 -Furthermore, the method steps shown in Figure 3 may be implemented independently of the method steps shown in Figure 2, such that maximum engine speed limitation may be imposed after starting the engine 110 without lubrication priming even having been considered. To that end, there may be a method of operating an engine, the method comprising the steps of: after starting the engine, if an engine lubricant pressure is below a lubricant pressure threshold, limiting a maximum speed of the engine for a period of time; and after the period of limited maximum engine speed, allowing the engine to operate normally, wherein, the period of limited maximum engine speed lasts until the engine lubricant pressure exceeds the lubricant pressure threshold or until an elapsed time after starting the engine has exceeded an engine speed limitation time threshold, whichever happens sooner.

Likewise, there may be a controller for operating an engine, the controller being arranged: after starting the engine, if an engine lubricant pressure is below a lubricant pressure threshold, to limit a maximum speed of the engine for a period of time; and after the period of limited maximum engine speed, to allow the engine to operate normally, wherein, the period of limited maximum engine speed lasts until the engine lubricant pressure exceeds the lubricant pressure threshold or until an elapsed time after starting the engine has exceeded an engine speed limitation time threshold, whichever happens sooner.

Carrying out the method steps related only to maximum engine speed limitation, without carrying out those related to lubricant pressure priming (which are shown in Figure 2), -27 -may still improve protection of the engine 110 and peripheral components from damage caused by high engine speeds.

Figure 1 shows a controller 120 in accordance with an

embodiment of the present disclosure.

The controller 120 may be configured to carry out the method

steps described in the present disclosure.

The controller 120 may have a number of inputs that may be used in order to determine the engine lubricant pressure and the engine operating conditions. For example, the inputs might include, but are not limited to, an engine lubricant pressure measurement 162 from a lubricant pressure sensor, a barometric pressure reading 163, an engine coolant temperature reading 164, a reading of the air inlet temperature 165 and a reading of the air temperature in the air intake manifold 166. The controller 120 might also have an engine start demand signal 161 input to indicate when the operator wants to start the engine 110.

The controller 120 may also have a number of outputs that may be used in order to control lubricant pressure priming, starting the engine 110 and maximum engine speed limitation.

For example, the outputs might include, but are not limited to, a fuel injector control signal 172.

Figure 1 also shows an engine unit comprising the engine 110 and the controller 120.

-28 -Figure 3 shows a vehicle within which the engine unit shown in Figure 1 could be used.

Industrial applicability

S

The present disclosure finds application in improving the lubrication of an engine before starting the engine, which may lead to an increase in the lifespan of lubricated engine parts.

Claims

-29 -Claims 1. A method of starting an engine, the method comprising the steps of: a) after an engine start is demanded, if an engine lubricant pressure is below a lubricant pressure threshold, priming the engine lubricant pressure for a period of time; and b) after the period of priming the engine lubricant pressure, starting the engine.
2. The method of claim 1, wherein the engine lubricant pressure is primed by cranking the engine with the engine fuel injectors turned off.
3. The method of any preceding claim, wherein the lubricant pressure threshold is determined by considering at least one of a barometric pressure, an engine coolant temperature, an air inlet temperature and an air temperature in an air intake manifold.
4. The method of any preceding claim, wherein the period of priming the engine lubricant pressure lasts until the engine lubricant pressure exceeds the lubricant pressure threshold or until the time spent priming the engine lubricant pressure has exceeded a lubricant pressure priming time threshold, whichever happens sooner.
5. The method of claim 4, wherein the engine lubricant pressure priming time threshold is determined by considering at least one of a barometric pressure, an engine coolant -30 -temperature, an air inlet temperature and an air temperature in an air intake manifold.
6. The method of any preceding claim, wherein step b) further comprises a step of: after the period of priming the engine lubricant pressure, waiting for a delay period before starting the engine.
7. The method of claim 6, wherein the delay period is determined by at least one of a barometric pressure, an engine coolant temperature, an air inlet temperature and an air temperature in an air intake manifold.
8. The method of any preceding claim, further comprising: c) after the engine has been started, limiting a maximum speed of the engine for a period of time.
9. The method of claim 8, wherein the period of limiting the maximum speed of the engine lasts until the engine lubricant pressure exceeds a further lubricant pressure threshold, or until a time after starting the engine has exceeded an engine speed limitation time threshold, whichever happens sooner.
10. The method of claim 9, wherein the further lubricant pressure threshold is determined by considering at least one of a barometric pressure, an engine coolant temperature, an air inlet temperature and an air temperature in an air intake manifold.

-31 -
11. The method of either claim 9 or 101 wherein the engine speed limitation time threshold is determined by considering at least one of a barometric pressure, an engine coolant temperature, an air inlet temperature and an air temperature S in an air intake manifold.
12. A controller for starting an engine, the controller being arranged: after an engine start is demanded, if an engine lubricant pressure is below a lubricant pressure threshold, to prime the engine lubricant pressure for a period of time; and after the period of priming the engine lubricant pressure, to start the engine.
13. An engine unit comprising the controller of claim 12.
14. A vehicle comprising the engine unit of claim 13.