Patent Description:
Three-way catalytic convertors are known to be used to receive exhaust gases from an internal combustion engine and convert toxic gases and pollutants into less-toxic products. The catalytic converters combine oxygen with carbon monoxide and unburned hydrocarbons to produce carbon dioxide and water, and, in addition, reduce oxides of nitrogen. Such catalytic converters operate most efficiently within a particular temperature range and when the composition of gas passing through the catalytic converter is such that the ratio of constituent gases of the composition is within a particular range.

A problem with a three way catalytic converter is that its efficiency may be adversely affected by stopping the engine or reducing the combustion torque output of the engine (i.e. the torque output of the engine resulting from the combustion of air and fuel) to zero.

When a request to stop the engine is received by a controller, for example as a result of a driver's request or an 'eco stop' function requesting shut down of the engine, the controller outputs a signal to stop fuel injection (otherwise known as a fuel cut signal). Due to the inertia of the engine, the engine will continue to rotate after fuel supply to the engine has been stopped or cut, but typically the intake and exhaust valves will continue to open and close. As a result, air is exhausted from the engine in place of combustion products. Similarly, when the engine is restarted, air which was trapped in one or more cylinders that were stopped in the compression or exhaust stroke is exhausted before the next intake stroke of those cylinders.

This causes a problem with the catalyst becoming over oxygenated such that it cannot efficiently convert pollutants exhausted by the engine. In addition, it may contribute to the temperature of the catalyst being reduced to below its light-off temperature (the temperature below which it cannot effectively convert pollutants). The following engine start and drive-away can cause excessive NOx (nitrogen monoxide and nitrogen dioxide) production and catalyst breakthrough (i.e. pollutants passing through the catalyst without being converted). This problem is particularly prevalent in vehicles in which the engine is frequently stopped and restarted, for example vehicles equipped with stop-on-the-move capabilities and PHEVs (plug-in hybrid electric vehicles) capable of operating for extended periods of time in electric only drive.

To counteract this problem there are known control functions invoked to inject additional fuel for a period of time, or a number of intake valve events, following reinstatement of fuelling (either at engine restart or following receipt of a positive torque request during overrun) until one or more models or exhaust sensor measurements indicate that the catalyst has become re-neutralised and is above its light-off temperature. Although fuel is saved during the fuel cut phase, the fuel enriched neutralisation process counteracts some of the fuel saving and produces more emissions than maintaining air-fuel ratio control throughout.

In <CIT>, a control system for controlling intake vacuum required for braking is described. An intake pipe is associated to an intake valve and terminated in a combustion chamber. An exhaust pipe is associated to an exhaust valve. The valve is disconnected such that a head of the valve is in an intake pipe closing position during operation cycles of an internal combustion engine and an electronic injection control system ensures cut-off of injection of fuel into the combustion chamber.

Aspects and embodiments of the invention provide a controller, a control system, an internal combustion engine, a vehicle, a method and a non-transitory computer readable medium as claimed in the appended claims.

According to an implementation there is provided a controller for controlling operation of a direct injection internal combustion engine, the controller being configured to: receive a first request signal indicative of a request to stop fuel being supplied to the engine; cause an intake valve of a cylinder of the internal combustion engine to remain closed during the current revolution of the internal combustion engine and revolutions of the internal combustion engine immediately following the current revolution of the internal combustion engine in dependence on the intake valve being closed at the time of receiving the first request signal; and cause injection of fuel into the cylinder and subsequently cause the intake valve to remain closed during revolutions of the internal combustion engine immediately following a next closing of the intake valve, in dependence on at least one of: the intake valve being open at the time of receiving the first request signal; and a next opening of the intake valve having already been scheduled at the time of receiving the first request signal and said next opening of the intake valve is to be performed.

This provides the advantage that the fuel injection to the cylinder is stopped as soon as possible after the request signal is received, but prevents unreacted oxygen from being exhausted from the engine and thereby is able to prevent oxidation of a catalytic converter receiving the gases exhausted from the cylinder. Consequently the efficiency of the catalytic converter during restarting of the engine is improved and the proportion of toxic pollutants passing through the catalytic converter without being converted is reduced.

The first request signal indicative of a request to stop fuel being supplied to the engine may be indicative of a request to reduce a torque output of the internal combustion engine to zero. For example, the controller may be used within a hybrid vehicle that is arranged to cut fuel supply to the internal combustion engine when the vehicle is stopped, being slowed down, or when an electric motor of the vehicle is usable for driving the vehicle. In a further example, the request to reduce a torque output of the internal combustion engine to zero may be received following a driver of a vehicle releasing an accelerator pedal of the vehicle when the vehicle is in motion, such that the internal combustion engine enters an overrun state. In yet a further example, the first request signal may be indicative of a user request to switch off the internal combustion engine.

The intake valve of the cylinder may be caused to be closed and/or kept closed by providing an output signal to a valve actuation means, such as a solenoid arranged to deactivate a hydraulic system that would otherwise cause opening of the valve on an intake stroke of the engine. Alternatively, the intake valve of the cylinder may be arranged to be closed by default and opened by the valve actuation means in response to a received signal. For example, the actuation means may comprise a solenoid arranged to open the intake valve in dependence on receiving a signal and the controller may therefore cause the intake valve to remain closed by not providing a signal to the solenoid valve.

Optionally, the controller is configured to cause the intake valve to remain closed for the current revolution of the internal combustion engine and revolutions immediately following the current revolution of the internal combustion engine in dependence on a next opening of the intake valve having not been scheduled.

Optionally, the controller is configured to cause ignition of fuel in the cylinder following said next closing of the intake valve, to enable combustion of the fuel in the cylinder during a next power stroke following the next closing of the intake valve.

Optionally, the controller is configured to cause said ignition only after a piston in the cylinder has reached top dead center. This provides the advantage that less of the energy generated by the combustion is used to turn the engine and therefore the engine is able to stop more quickly. In addition, a larger proportion of combustible gases may be exhausted to a catalytic converter, so that more combustion takes place within the catalytic converter, and consequently its temperature is given a boost before fuel supplied to the engine is stopped. This enables the temperature of the catalytic converter to remain above its operating temperature for a longer period after the engine is stopped, and there is a higher probability of it being above its operating temperature when the engine is restarted.

Optionally, the controller is configured to: receive a second request signal indicative of a request to increase a combustion torque output of the internal combustion engine from zero; cause opening of the intake valve of each cylinder of the internal combustion engine; cause injection of fuel into each said cylinder; and cause combustion of fuel during each power stroke of each said cylinder that next follows each intake stroke of that cylinder in which the intake valve was open. Causing such combustion provides the advantage that only air that has been used in a combustion process is exhausted, and this limits the amount of oxygen that may exhausted to a catalytic converter in an exhaust system of the engine. Consequently unwanted oxidation of the catalytic converter during start-up of the engine is prevented. This may allow a stoichiometric mixture of fuel and air, rather than a fuel rich mixture, to be used immediately after start-up of the engine. This may therefore reduce emission of air pollutants from the exhaust system.

The controller is configured to: receive a start request signal indicative of a request to increase a rotational speed of an output of the internal combustion engine from zero; and maintain in a closed position an intake valve of at least one cylinder of the internal combustion engine during at least a first intake stroke of the at least one cylinder. This provides the advantage that the start-up of the engine may be made more smoothly and therefore noise, vibration and harshness may be reduced.

Optionally, the controller is configured to cause a secondary torque source to rotate the internal combustion engine while the intake valve of the at least one cylinder is maintained in the closed position.

Optionally, the controller is configured to prevent opening of any intake valve of the internal combustion engine until: an intake stroke of a cylinder of the internal combustion engine that is expected to have its next power stroke after the internal combustion engine has reached a required speed of rotation; or the internal combustion engine (<NUM>) has been rotated through a predefined angle. This provides the advantage that the start-up of the engine may be made more smoothly and therefore noise, vibration and harshness may be reduced.

Optionally, the controller is configured to cause a first opening of the intake valve of the at least one cylinder following receipt of the second request signal or the start request signal, and cause injection of fuel into the at least one cylinder for combustion during a first combustion stroke following the first opening. This provides the advantage that the proportion of toxic pollutants passing through the catalyst without being converted may be further reduced.

Optionally, the injection of fuel into the at least one cylinder for combustion during the first combustion stroke following the first opening produces a stoichiometric mixture of air and fuel.

According to another implementation there is provided a control system for controlling operation of an internal combustion engine comprising a controller according to any one of the previous paragraphs and a valve actuation means configured to cause opening of the intake valve of each cylinder of the internal combustion engine in dependence on a received signal and allow the intake valve of each said cylinder to remain closed during an intake stroke of each said cylinder.

Optionally, the valve actuation means comprises a variable valve lift system. This provides the advantage of a valve lift system that may be controlled to maintain the intake valves in a closed position during an intake stroke.

Optionally, the variable valve lift system comprises a continuous variable valve lift system.

Optionally, the variable valve lift system comprises a hydraulic system.

According to a further implementation there is provided an internal combustion engine comprising the controller of any one of the previous paragraphs or the control system of any one of the previous paragraphs, wherein the engine comprises exhaust valves mechanically actuated by cams fixed to a camshaft.

Optionally, the internal combustion engine is arranged to inject fuel directly into the cylinders.

According to yet another implementation there is provided a vehicle comprising the controller, the control system or the internal combustion engine according to any one of the previous paragraphs.

According to a yet further implementation there is provided a method of controlling an internal combustion engine comprising: receiving a first request signal indicative of a request to stop fuel being supplied to the engine; in dependence on an intake valve of a cylinder being closed at the time of receiving the first request, causing the intake valve to remain closed during the current revolution of the internal combustion engine and revolutions immediately following the current revolution of the internal combustion engine; and in dependence on the intake valve of the cylinder being open or in dependence on a next opening of the intake valve having already been scheduled and said next opening of the intake valve is to be performed, causing injection of fuel into the cylinder and subsequently causing the intake valve to remain closed for revolutions immediately following the next closing of the intake valve.

Optionally, the method comprises causing ignition of said fuel in the cylinder only after a piston in the cylinder has reached top dead center. This provides the advantage that a larger proportion of the gases exhausted to a catalytic converter contain combustible gases, and therefore combustion of those gases in the catalytic converter enables it to remain at a high temperature for longer.

Optionally, the method comprises: receiving a second request signal indicative of a request to increase torque output of the internal combustion engine from zero; causing opening of the intake valve of each cylinder of the internal combustion engine; causing injection of fuel into each said cylinder; and causing combustion of fuel during each power stroke that next follows an intake stroke in which the intake valve was open.

The method comprises: receiving a start request signal indicative of a request to increase rotational speed of an output of the internal combustion engine from zero; and maintaining in a closed position an intake valve of at least one cylinder of the internal combustion engine during at least a first intake stroke of the at least one cylinder.

Optionally, the method comprises: causing a first opening of the intake valve following receipt of the second request signal or the start request signal; and causing injection of fuel into the cylinder for combustion during a first combustion stroke following the first opening. Optionally, said causing injection of fuel into the cylinder comprises causing injection of fuel into the cylinder to produce a stoichiometric mixture of air and fuel.

According to a yet further implementation there is provided a non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, cause performance of a method according to any one of the previous paragraphs.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination that falls within the scope of the appended claims. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination that falls within the scope of the appended claims, unless such features are incompatible.

A vehicle <NUM>, a control system <NUM>, a controller <NUM>, a method <NUM> and a non-transitory computer readable medium <NUM> in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures.

With reference to <FIG>, the vehicle <NUM> is a road vehicle in the form of a car. The vehicle <NUM> comprises an internal combustion engine <NUM> (referred to below as the engine <NUM>) and a secondary torque source <NUM> for turning the engine <NUM> over to start it. The secondary torque source <NUM>, in the present embodiment, is in the form of a belt integrated starter generator <NUM> configured to rapidly increase the rotational speed of the output of the engine <NUM> from zero when it is to be restarted.

In the present embodiment the engine <NUM> is a four stroke petrol (i.e. gasoline) engine comprising four cylinders <NUM>, but it will be appreciated that other embodiments may comprise less than or more than four cylinders.

The vehicle <NUM> comprises an accelerator pedal <NUM>, including an accelerator pedal sensor <NUM>, and a brake pedal <NUM> to enable a user to control the speed of the vehicle <NUM>.

The vehicle <NUM> also comprises a controller <NUM> in the form of an engine control unit (ECU) configured to control operation of the engine <NUM>. Amongst other things, the controller <NUM> is arranged to control fuel injection into the cylinders <NUM> of the engine <NUM> in response to signals received from various components of the vehicle <NUM> including the accelerator pedal sensor <NUM> and a vehicle starting system <NUM> that is configured to receive user inputs indicative of user requests to switch on the vehicle <NUM> or switch off the vehicle <NUM>. The starting system <NUM> may comprise a user operable switch and a smart key detection means, or an ignition key switch, or other means of enabling a user to provide indications that the engine <NUM> is to be started or stopped.

The controller <NUM> forms a part of a control system <NUM>, shown schematically in <FIG>, which is arranged to control operation of the engine <NUM>. As well as receiving input signals from the starting system <NUM> and the accelerator pedal sensor <NUM>, the controller <NUM> is also arranged to receive input signals from a brake system <NUM> of the vehicle <NUM> indicative of user request that are input at the brake pedal <NUM> (shown in <FIG>). It also receives input signals from a sensing device <NUM> arranged to sense the position of the crankshaft (not shown) of the engine <NUM>. In the present embodiment the sensing device <NUM> comprises a pair of Hall Effect sensors that are positioned to detect the orientation of the flywheel (not shown) of the engine <NUM>.

In response to received input signals, the controller <NUM> is configured to provide output signals to various components of the control system <NUM> that control operation of the engine <NUM>, including: fuel injectors <NUM> for controlling the mass of fuel injected into the cylinders <NUM> of the engine <NUM>; an ignition system <NUM> for igniting a fuel and air mixture within the cylinders <NUM>; and a valve actuation means <NUM> for actuating intake valves (<NUM> shown in <FIG>) of the cylinders <NUM> of the engine <NUM>. In the present embodiment the valve actuation means <NUM> is a continuous variable valve lift (CVVL) system <NUM>, but in alternative embodiments the valve actuation means <NUM> may comprise a discrete variable valve lift system. However, in either case, in dependence on signals received from the controller <NUM>, the valve actuation means <NUM> is capable of opening intake valves of the cylinders <NUM> during respective intake strokes but also capable of continuously maintaining the intake valves of the cylinders <NUM> in a closed position while the engine <NUM> is rotated through two or more revolutions.

During its operation, exhaust gases are emitted from the engine <NUM> via an exhaust system <NUM> comprising an exhaust manifold <NUM> and a three-way catalytic converter <NUM>.

During normal operation of the engine <NUM>, when it is producing combustion torque, the controller <NUM> is configured to provide output signals to the fuel injectors <NUM>, the ignition system <NUM> and the valve actuation means <NUM> to cause intake of air into the cylinders <NUM>, injection of fuel into the cylinders <NUM> and ignition of the fuel at specific times within the four stroke combustion cycle of the cylinders <NUM>. The engine <NUM> is a direct injection internal combustion engine <NUM> and therefore, typically, for each cylinder <NUM>, the intake valve (or the intake valves, in embodiments where there are several) are opened and closed during an intake stroke, and fuel is injected into the cylinder <NUM> during the intake stroke so that the injected fuel is mixed with air drawn in past the open intake valves. The ignition system <NUM> then ignites the fuel and air mixture towards the end of a compression stroke so that the mixture burns during the following power stroke. The combustion products are then exhausted from the engine <NUM> in the following exhaust stroke before the cycle begins again with a further intake stroke. The timing of the fuel injection, ignition and intake valve opening and closing are scheduled by the controller <NUM> in dependence on timing signals received from the sensing device <NUM>.

If the engine <NUM> is not running and a signal is received indicating that the engine <NUM> is required to produce combustion torque, the controller <NUM> may provide an output signal to the secondary torque means <NUM> to cause it to turn the engine <NUM> over and provide signals to the valve actuation means <NUM>, the fuel injectors <NUM> and ignition system <NUM> to cause the engine to be started.

If the engine <NUM> is running, and a fuel cut signal is received indicating that fuel provided to the engine <NUM> is to be stopped, the controller <NUM> co-ordinates stopping of fuel supply to the engine <NUM> and stopping of ignition of the air-fuel mixture so that the engine <NUM> stops producing combustion torque. In addition, as will be described in further detail below, the controller <NUM> also co-ordinates closing of the intake valves of the engine <NUM> to prevent oxygen reaching the three-way catalytic converter and causing oxidation of the catalyst.

In the present embodiment, the controller <NUM> is configured to stop and start the engine <NUM> in accordance with requirements for torque to be produced by the engine. Thus, a fuel cut signal received at the controller <NUM> could be received from the starting system <NUM> which has received a user input indicating that the engine <NUM> is to be switched off, but alternatively, the fuel cut signal may be received from the accelerator pedal sensor <NUM> indicating that the user has released the accelerator pedal <NUM> and no torque is required to be produced by the engine <NUM>, or alternatively the fuel cut signal may be received by the controller <NUM> from the brake system <NUM>, which has received a user input at the brake pedal <NUM> requesting that the vehicle <NUM> is to slow down or to stop accelerating when travelling down a hill.

Similarly, when the engine <NUM> is not producing torque, the controller <NUM> is configured to cause reinstatement of fuel supply to the engine <NUM> in dependence on receiving a request signal indicating that positive engine torque is required. For example, the request signal may be generated by the accelerator pedal sensor <NUM>, following a period in which the engine <NUM> has not been running at all, or at a time when the engine is still turning over due to momentum after it has previously been run.

In the present embodiment, the controller <NUM> comprises a memory device <NUM>, which stores instructions <NUM>, and a processor <NUM> configured to access the memory device <NUM> and execute the stored instructions <NUM> so that the processor <NUM> is operable to control the secondary torque source <NUM>, the valve actuation means <NUM>, the ignition system <NUM> and the fuel injectors <NUM>. The controller <NUM> also comprises an input/output means <NUM> of the controller <NUM> to receive input signals from, and provide output signals to, other components of the vehicle <NUM>. The input/output means <NUM> may include a transceiver for providing data communication over a data bus, such as a CAN (controller area network) bus.

Further details of the valve actuation means <NUM> of the system <NUM> is illustrated in <FIG>, which shows one of the cylinders <NUM> of the engine <NUM> containing a piston <NUM>. <FIG> also shows the mechanisms by which an intake valve <NUM> and an exhaust valve <NUM> of the cylinder <NUM> are actuated. It should be understood that although only one cylinder <NUM> with one intake valve <NUM> is illustrated in <FIG>, the intake valves <NUM> of the other cylinders <NUM> may be actuated in a similar manner. Also, in other embodiments, each cylinder <NUM> may have more than one intake valve <NUM> and where the present specification refers to the operation of the intake valve of a cylinder, it also applies to the operation of all of the intake valves of a cylinder that has multiple intake valves. i.e. A reference to an intake valve <NUM> of a cylinder <NUM> being open, opening, being closed or closing, should be understood to be a reference to all of the intake valves <NUM> of a cylinder <NUM> being open, opening, being closed or closing in respect of an embodiment with multiple intake valves <NUM> for each cylinder <NUM>.

In the present embodiment, the valve actuation means <NUM> comprises a hydraulic system of a known type which is arranged to actuate only the intake valves <NUM> of the engine <NUM>. The exhaust valves <NUM> are actuated by direct mechanical interaction with a cam <NUM> on a camshaft <NUM>, but in an alternative embodiment, the exhaust valves <NUM> may also be actuated by a continuous variable valve lift (CVVL) system in a similar manner to the intake valves <NUM>.

The valve actuation means <NUM> comprises a cam follower <NUM> which is arranged to be actuated by a cam <NUM> located on a camshaft <NUM> of the engine <NUM>. When actuated, the cam follower <NUM> actuates a piston <NUM> in a master cylinder <NUM> of the hydraulic system. The master cylinder <NUM> is hydraulically connectable via a solenoid valve <NUM> to a reservoir means <NUM> and a slave cylinder <NUM>, which contains a piston <NUM>. In the present embodiment, the solenoid valve <NUM> is biased so that connection is normally provided between the master cylinder <NUM> and the slave cylinder <NUM>, while the reservoir means <NUM> is isolated from the master cylinder <NUM>, and when the solenoid valve <NUM> is actuated, in response to a signal from the controller <NUM>, the master cylinder <NUM> is connected to the reservoir means <NUM> and isolated from the slave cylinder <NUM>.

The piston <NUM> of the slave cylinder <NUM> is arranged to actuate the intake valve <NUM>. When the intake valve <NUM> is actuated, as illustrated in <FIG>, the intake valve <NUM> is displaced from an intake port <NUM> of the cylinder <NUM> to allow air to be drawn into the cylinder <NUM>.

During normal operation of the engine <NUM>, the solenoid valve <NUM> provides connection between the master cylinder <NUM> and the slave cylinder <NUM>, at least for a part of the period in which the cam <NUM> actuates the piston <NUM> of the master cylinder <NUM>, during the intake stroke of the piston <NUM>. Consequently, the piston <NUM> of the slave cylinder <NUM> is hydraulically actuated and pushes the intake valve <NUM> to an open position, as shown in <FIG>. As the cam <NUM> is further rotated, it releases its pressure applied to the piston <NUM>, allowing hydraulic fluid to return to the master cylinder <NUM>, and the intake valve <NUM> to return to a closed position in which it closes the intake port <NUM>.

However, in response to a signal from the controller <NUM>, the solenoid valve <NUM> may be moved to connect the master cylinder <NUM> to the reservoir means <NUM> during the whole of the intake stroke of the piston <NUM>, so that actuation of the piston <NUM> in the master cylinder <NUM> cannot cause actuation of the piston <NUM> in the slave cylinder <NUM>. Consequently the intake valve <NUM> remains in the closed position, so that no air is able to enter the cylinder <NUM> through the intake port <NUM> during the whole of the intake stroke.

As illustrated in <FIG>, a fuel injector <NUM> is positioned to provide an injection of fuel directly into the cylinder <NUM>, and an ignition device <NUM>, such as a spark plug, is provided to ignite fuel and air mixtures present within the cylinder <NUM>.

In alternative embodiments, the valve actuation means <NUM> may comprise another type of variable valve lift system, such as an electrical system comprising solenoids or electric motors that are arranged to actuate the intake valves <NUM> of the engine <NUM> directly.

A flowchart illustrating a method <NUM> of controlling an internal combustion engine <NUM> performable by the controller <NUM> is shown in <FIG>. At block <NUM> a first request signal is received that is indicative of a request to cut fuel to the internal combustion engine <NUM>. For example, the request signal may be received by the controller <NUM> from the starting system <NUM>, which has generated the signal in response to receiving a user input indicating that the engine should be stopped, or the signal may be received from the brake system <NUM> indicating that the user of the vehicle <NUM> has applied pressure to the brake pedal <NUM> indicating that positive engine torque is not currently required.

At block <NUM> of the method <NUM>, an intake valve <NUM> of a cylinder <NUM> of the internal combustion engine <NUM> is caused to remain closed for the current revolution of the internal combustion engine and revolutions of the internal combustion engine immediately following the current revolution of the internal combustion engine in dependence on the intake valve being closed at the time of receiving the first request signal. In the embodiment of <FIG>, unless it is activated, the solenoid valve <NUM> is configured to provide hydraulic connection between the master cylinder <NUM> and the slave cylinder <NUM>. Consequently, the process of block <NUM> may be achieved by providing a signal to the solenoid valve <NUM> to cause it to isolate the slave cylinder <NUM> from the master cylinder <NUM> and provide a hydraulic connection between the master cylinder <NUM> and the reservoir means <NUM>.

In an alternative embodiment, in which the solenoid valve <NUM> is configured to provide connection between the master cylinder <NUM> and the reservoir means <NUM> unless the solenoid valve <NUM> is activated, the process of block <NUM> may be achieved by the controller <NUM> not providing a signal to the solenoid valve <NUM> that would cause it to connect the master cylinder <NUM> to the slave cylinder <NUM> during the intake stroke of the piston <NUM>.

An example of the process at block <NUM> is illustrated by the graphs of <FIG>, which show intake valve position, fuel injection, ignition, exhaust valve position and engine speed during revolutions of the engine <NUM> just before and after a fuel cut signal is received by the controller <NUM>. The four strokes are illustrated by the letters "I" for intake stroke, "C" for compression stroke, "P" for power stroke and "E" for exhaust stroke.

In this example, the fuel cut request is received while the intake valve <NUM> is in a closed position, and before the next opening of the intake valve has been scheduled by the controller <NUM>. Consequently, for all revolutions of the engine <NUM> following the fuel cut request, the intake valve is kept closed and no fuel injections are performed. The exhaust valve <NUM> continues to open during exhaust strokes but since no air is received into the cylinder <NUM> during the intake strokes, no oxygen is exhausted to the catalytic converter <NUM>.

At block <NUM> of the method <NUM>, illustrated in <FIG>, fuel is caused to be injected into the cylinder <NUM> and subsequently the intake valve <NUM> is caused to remain closed during revolutions of the internal combustion engine <NUM> immediately following a next closing of the intake valve <NUM>, in dependence on at least one of: the intake valve <NUM> being open at the time of receiving the first request signal; and a next opening of the intake valve <NUM> having already been scheduled at the time of receiving the first request signal and said next opening of the intake valve is to be performed.

An example of the process at block <NUM> is illustrated by the graphs of <FIG>, which show intake valve position, fuel injection, ignition, exhaust valve position and engine speed during revolutions of the engine <NUM> just before and after a fuel cut signal is received by the controller <NUM>. In this example, the fuel cut request is received after the intake valve <NUM> has started to be opened, letting air (containing oxygen) into the cylinder, but before fuel is injected into the cylinder. However, because the intake valve <NUM> is open when the fuel cut request is received, a final fuel injection <NUM> is allowed to be performed, following the fuel cut request. In the present embodiment, the final fuel injection <NUM> is performed during the intake stroke as it would be during normal operation of the engine <NUM>. The intake valve <NUM> is then closed and kept closed for subsequent revolutions of the engine <NUM> until the engine comes to rest.

In the compression stroke immediately following the final fuel injection <NUM>, the injected fuel is ignited and combustion takes place primarily in the following power stroke. Consequently exhaust gases resulting from the combustion are exhausted to the catalytic converter <NUM> in the following exhaust stroke. Thus, because the final fuel injection <NUM> is allowed to take place, oxygen is prevented from reaching the catalytic converter <NUM> and causing oxidation of the catalyst. The final fuel injection <NUM> also prevents the relatively rapid cooling of the catalytic converter <NUM> that would otherwise take place if air received by the cylinder <NUM> during the intake stroke were simply pumped into the catalytic converter <NUM> at the exhaust stroke without the final fuel injection <NUM> taking place.

A flowchart illustrating a method <NUM> of controlling an internal combustion engine <NUM> is shown in <FIG>, which provides an example of the method <NUM> of <FIG>.

At block <NUM> of the method <NUM>, a first request signal indicative of a request to cut fuel to the engine <NUM> is received. The process at block <NUM> is therefore the same as the process at block <NUM> of <FIG>.

At block <NUM> it is determined whether the intake valve <NUM> is closed. If it is not closed, then the processes at blocks <NUM> to <NUM> are performed. At block <NUM>, fuel is caused to be injected into the cylinder <NUM>, provided that fuel injection has not already been caused to be performed during the current intake stroke. For example, if the controller <NUM> has already provided an output signal to cause injection of fuel during the current intake stroke, then further fuel is not caused to be injected at block <NUM>.

At block <NUM> the intake valve <NUM> is caused to close and subsequently remain closed for revolutions of the engine <NUM> immediately following closing of the intake valve <NUM>. The fuel in the cylinder <NUM> is then caused to ignite at block <NUM> before the process at block <NUM> is performed.

Alternatively, if it is determined at block <NUM> that the intake valve <NUM> is currently closed, it is determined at block <NUM> whether the next opening of the intake valve is already scheduled and the next opening of the intake valve will be performed, for example because it is not possible to prevent the next scheduled opening. If it is determined that the next opening is scheduled and will be performed, then the processes at blocks <NUM> to <NUM> are performed as described above. Alternatively, if it is determined that the next opening is not yet scheduled or is scheduled but may nevertheless be stopped, the process at block <NUM> is performed. At block <NUM> the intake valve of the cylinder <NUM> is caused to remain closed for the current revolution of the engine <NUM> and revolutions of the engine that immediately follow the current revolution. The process at block <NUM> is then performed, in which a second request signal indicative of a request to increase torque output of the engine <NUM> is awaited. For example, the second request signal may be a signal from the accelerator pedal sensor <NUM> indicating that the user has depressed the accelerator pedal <NUM> to request engine torque.

It may be noted that, following the processes at blocks <NUM> or <NUM>, while the second request signal is awaited at block <NUM>, the intake valve <NUM> is not moved from its closed position. the intake valve <NUM> remains closed at least until a second request is received that is indicative of a request to increase a combustion torque output of the engine <NUM> from zero.

Although the methods <NUM> and <NUM> have been described above in respect of one cylinder of the internal combustion engine <NUM>, it should be understood that the methods are also applied to all cylinders of an engine <NUM> having several cylinders. An example of the control of an engine <NUM> is illustrated in the graphs of <FIG>, which includes graphs of the rotational speed of the engine in revolutions per minute (RPM), intake valve (I. ) position, fuel injection (INJ. ) and ignition (IG. ) for each of its four cylinders (#<NUM>, #<NUM>, #<NUM> and #<NUM>), during a period in which a fuel cut request is received. Although not illustrated in <FIG>, it should be understood that the one or more exhaust valves <NUM> of each cylinder <NUM> are open for a finite period during each exhaust stroke.

Before the fuel cut request is received, the intake valve <NUM> of each cylinder <NUM> is opened and closed during intake strokes of the cylinder <NUM>, and while the intake valve <NUM> of a cylinder <NUM> is open, fuel is injected into the respective cylinder. Towards the end of each compression stroke of each cylinder <NUM>, the fuel in that cylinder <NUM> is ignited.

In the example of <FIG>, when the fuel cut request signal is received, the intake valve <NUM> of cylinder #<NUM> is open and therefore fuel is injected <NUM> into the cylinder <NUM> and subsequently ignited <NUM> towards the end of the compression stroke to produce a final burn. The intake valve <NUM> of cylinder #<NUM> is then kept closed for subsequent revolutions of the engine <NUM>. The intake valve <NUM> of the other cylinders <NUM> (#<NUM>, #<NUM> and #<NUM>) is closed at the time that the fuel cut request signal is received, and consequently the intake valves of those cylinders (#<NUM>, #<NUM> and #<NUM>) are kept closed for the current and subsequent revolutions of the engine <NUM>. In the case of cylinder #<NUM>, the piston <NUM> is currently on its compression stroke, the cylinder having just received fuel and air during its previous intake stroke. Consequently, ignition is allowed to occur during the current compression stroke of cylinder #<NUM>, so that combustion products are exhausted to the catalytic converter <NUM> during the subsequent exhaust stroke.

A second example of the control of an engine <NUM> is illustrated in the graphs of <FIG>, which includes graphs of the rotational speed of the engine in revolutions per minute (RPM), intake valve (I. ) position, fuel injection (INJ. ) and ignition (IG. ) for each of its four cylinders <NUM>, during a period in which a fuel cut request is received. The graphs of <FIG> are like those of <FIG>, but in this example, the fuel cut request is received towards the end of the intake stroke of cylinder #<NUM>, the exhaust stroke of cylinder #<NUM>, the power stroke of cylinder #<NUM> and the compression stroke of cylinder #<NUM>. In this example, the next opening of intake valves of cylinder #<NUM> and cylinder #<NUM> have already been scheduled, and consequently those intake valves are opened after the fuel cut request signal is received. However, fuel is injected in cylinder #<NUM> and cylinder #<NUM> during the periods in which the respective intake valves are open, and in this example, a final ignition <NUM> and <NUM> is performed in each of those two cylinders #<NUM> and #<NUM>, so that combustion products are exhausted to the catalytic convertor <NUM>.

After the intake valves of the cylinders #<NUM> and #<NUM> are closed, they are then kept closed during subsequent revolutions of the engine, until the rotational speed of the engine is zero.

As will be described below with regard to <FIG> and <FIG>, the final ignition <NUM> and/or the final ignition <NUM> may be delayed until the respective piston <NUM> has reached top dead centre (shown as the angle "<NUM>" on the graphs), so that a larger proportion of combustible gases reach the catalytic converter <NUM>. In addition, or alternatively, the final ignition <NUM> and/or final ignition <NUM> may be omitted, so that a fuel and air mixture reaches the catalytic converter <NUM>. However, in each case, the air-fuel ratio may be maintained at lambda = <NUM>, so that a stoichiometric mixture reaches the catalytic converter.

In an example of the method <NUM> of <FIG>, the process at block <NUM> comprises causing ignition of the fuel in the cylinder <NUM> following closing of the intake valve <NUM>. In one example illustrated in <FIG> the process at block 707a includes causing ignition of the fuel in the cylinder following closing of the intake valve only after the piston <NUM> in the cylinder <NUM> has reached top dead centre. A flowchart illustrating this process is shown in <FIG>, and an example of the control of an engine <NUM> is illustrated in <FIG>, which include graphs of intake valve (I. ) position, fuel injection (INJ. ) and ignition (IG. ) for each of its four cylinders <NUM>, during a period in which a fuel cut request is received. It should be understood that the exhaust valve(s) <NUM> of each cylinder <NUM> are open for a finite period during each of their exhaust strokes.

The graphs of <FIG> are like those of <FIG>, but after the receipt of the fuel cut request signal, the ignition <NUM> and <NUM> that takes place in cylinder #<NUM> and cylinder #<NUM> is delayed until after the respective piston <NUM> has reached top dead centre (shown as the angle "<NUM>" on the graphs). Consequently, combustion is delayed and the gases exhausted from cylinders #<NUM> and #<NUM> comprise a larger proportion of combustible gases than there would be if the ignitions <NUM> and <NUM> were performed before top dead centre was reached by the respective pistons <NUM>. Consequently a relatively large quantity of combustible gases is combusted in the catalytic converter <NUM>, so that the temperature of the catalytic converter <NUM> is boosted. As a result, the temperature of the catalytic converter <NUM> remains above its operating temperature for a longer period after the engine <NUM> is stopped, and there is a higher probability of it being above its operating temperature when the engine is restarted.

In an alternative method, the processes are the same as those of the method <NUM>, illustrated by the flowchart of <FIG> but the process at block <NUM> is omitted. Thus, in this alternative method fuel is injected at block <NUM> and during a subsequent exhaust stroke a mixture of unburnt fuel and air is exhausted to the catalytic converter <NUM> where it is more slowly converted into combustion products. In an example of this alternative method, fuel is caused to be injected during intake strokes of cylinder(s) <NUM> for which the intake valve(s) <NUM> are open at the time of receiving a fuel cut request signal, and subsequently those intake valve(s) <NUM> are caused to remain closed during revolutions of the internal combustion engine <NUM> immediately following the next closing of the intake valve(s), as illustrated in the example of <FIG>. However, in the alternative method, the final ignition <NUM> in cylinder #<NUM> is not performed and the final ignition <NUM> in cylinder #<NUM> may not be performed.

A flowchart illustrating a further method <NUM> of controlling an internal combustion engine <NUM> performable by the controller <NUM> is shown in <FIG>. This method <NUM> relates to increasing the combustion torque produced by the engine <NUM> from zero and therefore may follow on from the method <NUM> of <FIG> or the method <NUM> of <FIG> in which the combustion torque produced by the engine was reduced to zero by cutting the supplied fuel. The method <NUM> of <FIG> may be performed when the engine speed is zero, for example, when the vehicle <NUM> is first started. Alternatively the method <NUM> may be performed following an eco-stop (in which fuel supply to the engine <NUM> was cut, for example due to the user depressing the brake pedal <NUM>) and the engine <NUM> is still turning when the user depresses the accelerator pedal <NUM> causing the generation of a request for positive engine torque.

At block <NUM> of the method <NUM> a second request signal is received indicative of a request to increase torque output from the internal combustion engine <NUM> from zero. At block <NUM> of the method <NUM>, opening of the intake valves <NUM> of each cylinder <NUM> of the engine <NUM> is caused to be scheduled. The scheduling of opening of the intake valves <NUM> may be dependent on the current speed of the engine <NUM> and dependent on the position of each of the respective cylinders <NUM> within their four-stroke cycles. The position of each of the cylinders <NUM> may be determined from the signals received from the position sensing device <NUM> (shown in <FIG>) described above.

At block <NUM>, injection of fuel is caused to be scheduled for each cylinder <NUM> for which the intake valve <NUM> is scheduled to be opened during its next intake stroke. In the present embodiment, the quantities of fuel scheduled to be injected provide a stoichiometric mixture of fuel and air in the cylinders <NUM>. This is possible because, as described above, the catalytic converter <NUM> was not oxidized during revolutions of the engine <NUM> following the fuel cut to the engine <NUM>, and therefore a rich mixture is not required in order to reduce oxidized components of the catalyst when the engine <NUM> is restarted.

At block <NUM> of the method <NUM>, fuel is caused to be combusted during each power stroke that next follows each intake stroke during which the corresponding intake valve <NUM> was open. For each of the cylinders <NUM>, if an intake valve <NUM> is opened during start-up of the engine <NUM>, fuel is also injected and combustion is caused to take place during the next following power stroke. As previously described, during shut down of the engine <NUM>, the last time an intake valve <NUM> of each cylinder <NUM> is opened, fuel is injected and no further opening of the intake valve <NUM> is allowed while the combustion torque of the engine <NUM> is reduced to zero. Thus, for a cylinder <NUM> that starts with a power stroke at engine start-up, no combustion may be possible during that first power stroke. However, it may be noted that for that cylinder <NUM> the intake valve <NUM> was not open during its most recent intake stroke, having been kept closed since the final power stroke during engine shut-down.

An example of the method <NUM> is illustrated by the graphs of <FIG>, which show intake valve position, fuel injection, ignition and engine speed during revolutions of the engine <NUM> just after a start request signal indicative of a request for positive engine torque is received by the controller <NUM>. It should be understood that the exhaust valve(s) <NUM> of each cylinder <NUM> are open for a finite period during each exhaust stroke.

In the example of <FIG>, the engine <NUM> is initially at rest (i.e. its speed of rotation is zero). On receipt of the start request signal, the controller <NUM> immediately schedules opening of the intake valves <NUM> and fuel injection (to occur during intake strokes of each cylinder <NUM>) and schedules ignition to occur towards the end of the following compression strokes. It may be noted that there is no additional injection of fuel and no ignition during the first compression stroke of cylinder #<NUM>. Due to the method <NUM> or method <NUM> described above, the cylinders <NUM> contain combustion products when the start request signal is received rather than air (which they would contain if the intake valves <NUM> were not held closed after the final combustions), and therefore an additional injection of fuel during the first compression stroke of cylinder #<NUM> is not required.

A flowchart illustrating a method <NUM> of controlling an internal combustion engine <NUM> is shown in <FIG>, which provides an example of the method <NUM> of <FIG>. At block <NUM> of the method <NUM>, a start request signal is received indicative of a request to increase speed of the internal combustion engine from zero. At block <NUM> an intake valve <NUM> of at least one cylinder <NUM> of the engine <NUM> is maintained in a closed position during at least a first intake stroke of the at least one cylinder <NUM>. This results in a smooth start-up of the engine without oxidation of the catalytic converter, as described below with reference to <FIG>.

The remainder of the method <NUM>, illustrated in <FIG>, further comprises the processes at blocks <NUM>, <NUM> and <NUM> as described above in respect of <FIG>. Thus, after the intake valve <NUM> of at least one cylinder <NUM> is kept closed at block <NUM>, the intake valves <NUM> are opened in accordance with scheduling performed at block <NUM>, fuel is caused to be injected into each cylinder at block <NUM>, and at block <NUM> fuel is caused to combust during each power stroke of a cylinder that next follows each intake stroke in which the intake valve was open.

An example of the method <NUM> is illustrated by the graphs of <FIG>, which show engine speed as it increases from zero, along with intake valve (I. V) position, fuel injection (INJ. ) timing, and ignition (IG. ) timing for the four cylinders <NUM> of the engine <NUM> during its first revolutions after receipt of a start request signal. Initially, the engine <NUM> is rotated by the secondary torque source <NUM>. The rate at which the speed of the output of the engine increases from zero up to idle speed (e.g. <NUM> revolutions per minute) under the action of the secondary torque source <NUM> is known, for example from prior measurements, and therefore the angle through which the engine <NUM> must be rotated before a first ignition is required is also known. If the secondary torque source <NUM> is a belt integrated starter generator then the engine speed may reach the idle speed before valve motion is enabled. If the secondary torque source <NUM> is a traditional 'pinion starter' then the engine speed may be significantly lower than idle speed (e.g. <NUM> revolutions per minute) when valve motion is enabled. In any case the valve motion may be inhibited during the engine speed increase and commence operation <NUM> revolution prior to intended combustion.

In the present example, the first power stroke is required to occur when the engine <NUM> has approximately reached its idle speed, and therefore the first ignition is required after the engine has turned through about <NUM> degrees. In this instance the cylinder that has its first power stroke when this speed has been achieved is cylinder #<NUM>. In preparation to cause combustion during this power stroke of cylinder #<NUM>, its intake valve <NUM> is the first to be opened after about <NUM> degrees and fuel is injected.

As shown in <FIG>, by the time that the first intake valve <NUM> is opened, the engine <NUM> has already reached a speed of more than about <NUM>% of idle speed.

In this example, during starting by the secondary torque source <NUM>, the first cylinders to perform intake strokes are cylinders #<NUM> and #<NUM>, but it may be predicted that the engine <NUM> will not be rotating sufficiently quickly at the time of their first power strokes. Therefore, during the first intake stroke of cylinder #<NUM> and cylinder #<NUM>, the intake valves <NUM> of those cylinders are maintained in a closed position and no fuel is injected. Consequently, there is no combustion during the first power strokes of cylinder #<NUM> and cylinder #<NUM>.

By preventing combustion during the first power strokes of the cylinders #<NUM> and #<NUM> in the example of <FIG>, the engine <NUM> may be accelerated from zero speed in a smooth manner by a secondary torque source, and therefore noise vibration and harshness may be minimised. Also, because the intake valve(s) of cylinders #<NUM> and #<NUM> are kept closed during the first intake stroke, air is prevented from being drawn into those cylinders and exhausted to the catalytic converter in the next exhaust stroke. Consequently unwanted oxidation of the catalytic converter is prevented.

For purposes of this disclosure, it is to be understood that the controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

The blocks illustrated in the <FIG>, <FIG>, <FIG> and <FIG> may represent steps in a method and/or sections of code in the computer program <NUM>. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

Claim 1:
A controller (<NUM>) for controlling operation of a direct injection internal combustion engine (<NUM>), the controller being configured to:
receive a first request signal indicative of a request to stop fuel being supplied to the engine;
cause an intake valve (<NUM>) of a cylinder (<NUM>) of the internal combustion engine to remain closed during the current revolution of the internal combustion engine and revolutions of the internal combustion engine immediately following the current revolution of the internal combustion engine in dependence on the intake valve being closed at the time of receiving the first request signal; and
cause injection of fuel into the cylinder and subsequently cause the intake valve to remain closed during revolutions of the internal combustion engine immediately following a next closing of the intake valve, in dependence on at least one of: the intake valve being open at the time of receiving the first request signal; and a next opening of the intake valve having already been scheduled at the time of receiving the first request signal and said next opening of the intake valve is to be performed;
wherein the controller is configured to:
receive a start request signal indicative of a request to increase a rotational speed of an output of the internal combustion engine from zero; and
maintain in a closed position an intake valve of at least one cylinder of the internal combustion engine during at least a first intake stroke of the at least one cylinder.