CN103590912B - The method of engine system and control engine system - Google Patents

Abstract

The present invention relates to an engine system and a method of controlling an engine system. An engine system is described comprising a multi-cylinder engine 5 with at least one deactivatable cylinder, a turbocharger 10 , an electric supercharger 20 and an electronic controller 40 . The electronic controller 40 is operable to activate the electric supercharger 20 when the deactivatable cylinders of the engine 5 are deactivated, thereby increasing the operating efficiency of the engine 5 . In a particularly advantageous embodiment of the invention, the engine system forms part of the hybrid vehicle 1 so that recaptured electrical energy can be reused for powering the electric supercharger 20 .

Description

Engine system and method of controlling the engine system

technical field

The present invention relates to engine systems having turbocharged multi-cylinder engines, and in particular to a method of controlling the engine system when one or more cylinders of the engine are deactivated.

Background of the invention

It is known to provide mechanisms for deactivating one or more cylinders of a multi-cylinder internal combustion engine of a motor vehicle to reduce fuel consumption and/or emission production. This cylinder deactivation increases the load on each cylinder, causing the engine to operate near its maximum efficiency when engine load is relatively low.

It is further known to provide boosted air intake to an internal combustion engine by using a turbocharger which utilizes exhaust gas exhausted from the engine to drive a compressor thereby increasing the mass flow rate and pressure of the air entering the engine.

When combining cylinder deactivation and turbocharging there is a problem that the effective operating area available to the engine is very limited. While low speed cruising of a motor vehicle is generally possible when cylinder deactivation occurs, acceleration is not possible because acceleration would cause engine operation to occur outside the efficient operating region. This is primarily due to the inability of turbochargers to operate effectively with the reduction in mass flow rate due to cylinder deactivation. In the case of variable geometry turbochargers, the intake area is usually reduced at such low loads to increase the flow rate of gas through the turbine side of the turbocharger, but this has the drawback of increased engine back pressure. Since the boost pressure that can be delivered at such low mass flow rates is also limited, the combination of low inlet pressure and higher back pressure will generally result in a high pressure differential between the intake and outlet sides of the engine and high pumping losses.

Contents of the invention

It is an object of the present invention to provide an improved engine system and method of controlling such an engine system so as to minimize such problems and disadvantages.

According to a first aspect of the present invention there is provided an engine system comprising a multi-cylinder engine having at least one deactivatable cylinder; a turbocharger having a compressor and a turbine operatively connected to the engine; an electric booster ), which is connected to the compressor of the turbocharger, thereby selectively supplying air to the compressor of the turbocharger under increased pressure; and an electronic controller, which controls the activation of the electric supercharger, wherein the electronic control The booster is operable to activate the electric booster when at least one cylinder of the engine is deactivated and at least one electric booster operating condition is met.

The electric supercharger operating condition may be an engine speed range, and the electronic controller is operable to only activate the electric supercharger if the engine is operating within the speed range defined by the lower speed limit and the upper speed limit.

Advantageously, when it is activated, the electric supercharger is controlled by an electronic controller to meet the torque demand of the engine.

A further operating condition of the electric supercharger may be that the torque demand of the engine is not greater than the maximum engine torque limit of the current engine speed.

A further electric supercharger operating condition may be that the torque demand of the engine is greater than the minimum engine torque limit for the current engine speed.

The system may further include a low pressure exhaust gas recirculation circuit having a low pressure exhaust gas recirculation control valve controlled by the electronic controller, and when the electric supercharger is enabled and the low pressure exhaust gas recirculation control valve is open, the electric supercharger may Increases flow through the low-pressure exhaust gas recirculation loop.

The engine system may include at least one exhaust aftertreatment device connected downstream of a turbine of the turbocharger, and the low pressure exhaust gas recirculation loop may include a low pressure exhaust gas flow passage extending from a location downstream of the at least one aftertreatment device to The location upstream of the electric booster.

An electric booster may include a compressor driven by an electric motor.

According to a second aspect of the invention there is provided a motor vehicle having an engine system constructed according to said first aspect of the invention.

The motor vehicle may be a motor vehicle having an energy recycling system to capture electrical energy during vehicle use and store it in an electrical energy storage device, and the electrical energy stored in the electrical energy storage device may be used to power an electric supercharger.

According to a third aspect of the present invention there is provided a method of controlling an engine system comprising a multi-cylinder engine having at least one deactivatable cylinder, a turbocharger and an electric supercharger, wherein the method comprises at least The electric supercharger is activated when one cylinder is deactivated and at least one electric supercharger operating condition is met.

The at least one electric booster operating condition may be an engine speed range, and the method may further include only activating the electric booster if the engine is operating within the speed range defined by the lower speed limit and the upper speed limit.

Advantageously, when activated, the electric supercharger can be controlled to meet the torque demand of the engine.

The operating condition of the electric supercharger may be that the torque demand of the engine is not greater than the maximum engine torque limit of the current engine speed.

The electric supercharger operating condition may be that the torque demand of the engine is greater than the minimum engine torque limit for the current engine speed.

Description of drawings

The invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a motor vehicle according to a second aspect of the invention having a first embodiment of an engine system according to the first aspect of the invention;

Figure 2 is a schematic diagram similar to Figure 1 but showing a second embodiment of an engine system according to the first aspect of the invention;

Figure 3 is a flow chart showing a method according to a third aspect of the present invention;

Figure 4 is a graph of torque versus engine speed showing different operating regions of the engine; and

FIG. 5 is a block diagram showing further features of the motor vehicle shown in FIGS. 1 and 2 .

Detailed ways

Referring specifically to FIG. 1 , a motor vehicle 1 is shown having an engine system powering the motor vehicle 1 through a transmission system (not shown).

The engine system comprises a multi-cylinder engine in the form of a four-cylinder diesel engine 5, a turbocharger 10 operatively connected to the engine 5, an electric supercharger 20, an air filter 4, a high pressure exhaust gas recirculation valve 8, Intercooler 14 , torque demand input in the form of accelerator pedal 15 and accelerator pedal position sensor 16 , aftertreatment device 30 and electronic controller 40 .

The turbocharger 10 comprises a compressor 11 and a turbine 12 connected by a shaft such that the turbine 11 drives the compressor 11 when exhaust gas flows from the engine through the exhaust manifold 7 . The compressor 11 is connected to the intake manifold 6 of the engine 5 so as to supply air to the engine 5 .

The engine 5 has a plurality of fuel injectors (not shown) that provide fuel to the engine 5, as is known in the art.

The electric booster 20 includes an electric motor 21 drivably connected to a compressor 22 via a shaft.

As shown in FIG. 5 , the electric supercharger 20 or more precisely the electric motor 21 is controlled by an electronic controller 40 via a power controller 41 . The electric booster 20 has an active state, in which the electric motor 21 drives the compressor 22 , and an inactive state, in which electric power is not supplied to the electric motor 21 . When the electric supercharger 20 is active, the electronic controller 40 varies the speed of the electric motor 21 , thereby controlling the electric supercharger 20 to meet the torque demand of the engine 5 .

When the engine 5 is running, the air enters the intake flow path as indicated by the arrow "IN", flows through the air filter 4, reaches the intake side of the compressor 22, and reaches the inlet of the compressor 11 of the turbocharger 10 through the compressor 22. The air side then flows through the intake manifold 6 to the engine. Accordingly, the compressors 11, 22 of the turbocharger and the electric supercharger, respectively, are operatively connected in a series arrangement.

In an alternative arrangement (not shown), bypass channels are arranged around the electric booster 20 . Under the control of the electronic controller 40, the flow through the bypass channel is controlled by the electronic control valve. When the electric supercharger 20 is not operating and/or when the engine 5 is operating under high load, the electronically controlled valve opening allows intake air to bypass the electric supercharger 20 . This prevents unnecessary restriction of intake air flow by the electric supercharger 20 when the electric supercharger 20 is not in use.

Exhaust gas flows from the engine 5 through the exhaust manifold 7 to the intake side of the turbine 12 of the turbocharger 10 , through the turbine 12 to the outlet side of the turbine 12 , and on to the aftertreatment device 30 . Exhaust gas then flows from aftertreatment device 30 to atmosphere as indicated by arrow "EX". It is understood that one or more noise reduction devices or mufflers are typically located between aftertreatment device 30 and the location where the exhaust gas is returned to atmosphere.

The high-pressure exhaust gas recirculation circuit is also shown in Figure 1, which has a high-pressure exhaust gas recirculation valve 8 which is controlled by an electronic controller 40 so that a certain amount of exhaust gas from the engine 5 is exhausted when required. The gas is recirculated back to the intake side of the engine 5, as is known in the art.

Referring now to FIG. 4, the relationship between the torque of the engine 5 and the engine speed under different conditions is shown.

The maximum torque curve _{Tmax (max)} shows the relationship between torque and engine speed at wide open throttle, that is, when the accelerator pedal 15 is fully depressed and all cylinders are activated.

The exact shape and magnitude of the _maximum torque curve Tmax will depend on a number of factors including, but not limited to, engine displacement, maximum allowable cylinder pressure, maximum allowable boost pressure, maximum available boost pressure, maximum allowable exhaust temperature, and transmission torque capacity.

Curve T _{Turbocharger Limit (LimTurbo)} shows the maximum torque available from the engine 5 when all deactivatable cylinders of the engine 5 are in their deactivated state and only the turbocharger 10 is used to increase the mass flow rate or intake pressure . The operating region defined by the quadrilaterals c, e, f, d is an effective operating region of the engine 5 using only the turbocharger 10 .

Curve T _{e-booster limit (LimEbooster)} shows that can be obtained from engine 5 when the deactivatable cylinders of engine 5 are in their deactivated state and the mass flow rate or intake pressure is increased with turbocharger 10 and e-charger 20 maximum torque. The operating area defined by quadrilateral a, b, e, f is the effective operating area of the engine 5 utilizing turbocharger 10 and electric supercharger 20, and the operating area defined by quadrilateral a, b, c, d is when the engine 5 An additional efficient operating region is provided through the use of the electric supercharger 20 when operating with its cylinders deactivated.

It will be appreciated that the electric supercharger 20 can be applied all the time when the cylinders are deactivated, or only when the torque demanded exceeds the torque defined by _{the turbocharger limit} of curve T, but additional pressure or mass is required when the cylinders are deactivated Anytime the flow rate is high, it is generally more efficient to apply the electric booster 20.

Line _Nmin represents the lowest engine speed at which cylinder deactivation is effected. This limit is typically determined based on NVH considerations of the engine 5 .

Line _Nmax represents the highest engine speed possible with cylinder deactivation. This limit is usually determined based on the maximum speed at which cylinder deactivation can be removed without causing damage to the engine 5 . That is, this limit is based on the mechanical properties of the mechanism used to achieve deactivation.

During normal operation of the engine 5, fuel will be supplied to the engine 5 in response to torque demand from the operator as indicated by the position of the accelerator pedal 15 . The electronic controller 40 varies the matching air flow that is fueled to enter the engine 5 based on a number of factors, including engine speed, either directly or through a separate engine control unit (not shown), thereby providing a predetermined air/fuel ratio and controlling the turbo The supercharger 10 is used to generate the required boost to achieve the required demand.

If the torque demand on the engine 5 is relatively low, the electronic controller 40 will decide whether to deactivate the deactivatable cylinders of the engine 5 . This determination is based on a variety of factors including, but not limited to, the current engine speed compared to the _upper and lower engine speed limits Nmax and _Nmin respectively, the expected engine efficiency for the deactivated and non-deactivated states, the Expected emissions, expected exhaust gas temperature for deactivated and non-deactivated conditions, and cylinder temperature for deactivated and non-deactivated conditions.

If the deactivation conditions are met, the electronic controller 40 proceeds and deactivates the deactivatable cylinders of the engine 5 - cylinders 2 and 3 in this example, while the electric supercharger 20 will be activated.

As previously stated, if the torque demand of the engine 5 is below the torque output shown as the T _{turbocharger limit} in FIG. Applicable as it will lead to improved engine efficiency. This is because the application of electric boosting allows the inlet to the turbocharger 10 to remain in a more open position, thereby reducing back pressure on the engine 5 and thus reducing the pressure differential across the engine 5 . This is possible because as most of the boost pressure is provided by the electric supercharger 20, there is no need for the turbine 12 to drive the compressor 11 to generate the required boost pressure.

If the torque demand of the engine 5 is above the torque output indicated by T _{turbocharger limit} in FIG. 4 , additional boosting by means of the electric supercharger 20 is typically required. As before, the use of the electric supercharger 20 allows the inlet to the turbocharger 10 to remain in a more open position, thereby reducing back pressure to the engine 5 and thus reducing the pressure differential across the engine 5 since the turbine 12 is not required to drive compression engine 11 to generate the required boost pressure.

The torque demand of the engine 5 is mainly satisfied by controlling the electric supercharger 20 so that if the user of the engine 5 desires a torque increase, as is the case when acceleration of the motor vehicle is required, the electronic controller 40 increases the speed of the electric motor 21, thereby increasing the speed of the electric motor 21 from The compressor 22 provides greater boost pressure and greater torque from the engine 5 and increases the amount of fuel supplied to the engine 5 . It will be appreciated that the maximum torque that can be produced is limited by the maximum allowable torque limit T _{e-supercharger limit} for the current engine operating speed. If the torque demand decreases, the electronic controller 40 will reduce the speed of the electric motor 21 thereby reducing the boost provided by the electric supercharger 20 .

Once activated, the electric supercharger 20 is controlled by the electronic controller 40 to meet the current torque demand in the most efficient manner, which can mean that most of the required boost is provided by it or by the turbocharger 10 and The electric supercharger 20 is common. If a torque demand exceeding the maximum torque limit Te- _{BoostLimit is received during the time that the Electric-Booster} 20 is active, the Electric-Booster 20 is controlled so as not to exceed the maximum torque limit TE- _BoostLimit , and if demand For more than a very short time, the electronic controller 40 switches the engine 5 out of inactive mode to better meet the required torque demand. It is to be understood that the maximum torque limit T _{e-supercharger limit} applies only if the cylinders are deactivated, otherwise it is limited by the _limit Tmax.

The maximum torque limit T _{electric supercharger limit} represents an operating condition of the electric supercharger that must be met. That is, if the torque demand of the engine is not greater than the maximum torque limit T of the current engine speed, the electric _supercharger 20 can be used and the operating condition can be met, otherwise it cannot be used.

In some embodiments, a further e-charger operating condition is that the torque demand of the engine is greater than the minimum engine torque limit _{Tturbocharger limit} for the current engine speed. That is, in some embodiments, the electric supercharger 20 is only applied when the turbocharger 10 is unable to effectively provide the required boost.

It is also understood that the electric supercharger 20 can also be used to supplement the turbocharger 10 when all cylinders of the engine 5 are active, but in this case different operating limits will be defined. That is, when all cylinders of the engine 5 are operating, the limits Te _{-supercharger limit} , _Tmax and _Tmin do not apply.

A particularly advantageous application of the invention relates to hybrid vehicles. FIG. 5 shows in block diagram form a motor vehicle configured as a hybrid motor vehicle 1 with an engine 5 and, in addition, a second power source in the form of a traction motor 50 . The traction motor 50 is drivably connected to at least one wheel 2 of the motor vehicle 1 such that it drives the wheel 2 or is driven by the wheel 2 . In practice, a coupling such as a clutch may be placed between the traction motor and the wheels 2 to enable disconnection of the drive therebetween. The traction motor 50 is electrically connected to an electrical energy storage device 51 which may be in the form of a battery or an ultracapacitor. As indicated by the double-headed arrow, electrical energy (current) may flow from the electrical energy storage device (EESD) 51 to the traction motor 50 or from the traction motor 50 to the EESD 51 . That is, traction motor 50 is a motor/generator. The flow of electrical energy will depend on the current operating state of the motor vehicle 1 and the electronic controller 40 controls the electrical energy flow between the traction motor 50 and the EESD 51 via the power controller 42 based on predetermined operating parameters.

Electric energy is also supplied from the EESD 51 to the electric supercharger 20 , or more specifically, the electric motor 21 of the electric supercharger 20 , through the power controller 41 .

Therefore, the electrical energy of the electric booster 20 comes from the EESD 51 . The traction motor 50 and the EESD 51 form part of an energy recycling system capable of capturing energy during the use of the motor vehicle 1 and storing it for future use.

For example, traction motor 50 may operate as a generator, storing electrical energy in EESD 51 for later use by traction motor 50 or electric supercharger 20 if the vehicle is required to reduce speed.

One advantage of using the electricity stored in the EESD 51 to power the electric supercharger 20 is that no fuel is wasted by using the engine 5 to generate electricity to drive the generator. A second advantage is that it provides an opportunity to use stored electrical energy at times when electric drive traction motor 50 does not require current.

Furthermore, if the traction motor 50 and the engine 5 are used simultaneously with the deactivatable cylinders of the engine 5 deactivated, the stored electric power not only provides direct drive of the motor vehicle 1 through the traction motor 50, but also improves the performance of the engine 5, thereby increasing the The total efficiency of EMU 1.

A second particularly beneficial application of the invention relates to motor vehicles that can recover energy during deceleration and store the recovered energy for future use. Under this arrangement, the conserved electrical energy can be used to power the electric supercharger 20, thus providing the electrical energy required to generate any engine boost by the electric supercharger 20 at no additional cost to fuel. For example, an engine configured with a drive accessory in front of the engine that drives a generator can be used to recapture electrical energy by generating electricity from the generator when the engine is in an overrun condition. Such a motor vehicle can be said to have an energy recycling system which captures electrical energy during use of the motor vehicle and stores it in an electrical energy storage device.

Referring now to FIG. 2 , there is shown a second embodiment of an engine system, which in most respects is consistent with that described above with reference to FIGS. 1 and 4 , and will not be described in detail again. Components that are the same in FIG. 2 as in FIG. 1 are given the same reference numbers.

The second embodiment differs from the first embodiment in that the engine system has two aftertreatment devices in the form of a diesel oxidation catalyst 31 and a diesel particulate filter 32 instead of a single aftertreatment device; and the engine system of the second embodiment also includes a low pressure Exhaust gas recirculation circuit - together with the high pressure exhaust gas recirculation circuit already described with respect to FIG. 1 .

The low-pressure exhaust gas recirculation loop has a low-pressure exhaust gas recirculation control valve 9 controlled by an electronic controller 40 and includes a low-pressure bank extending from a location downstream of the diesel particulate filter 32 to a location upstream of the compressor 22 of the electric supercharger 20 . air flow channel. The location where the low pressure exhaust gas recirculation circuit engages the intake passage to the engine 5 is between the air filter 4 and the compressor 22 of the electric supercharger 20 .

The connection of the low pressure exhaust gas recirculation circuit to the intake flow path upstream of the electric supercharger 20 has the advantage that when the electric supercharger 20 is activated and the low pressure exhaust gas recirculation control valve 9 is open, the electric supercharger 20 will increase the low pressure The flow of exhaust gas through the low-pressure exhaust gas recirculation circuit. That is, the electric supercharger 20 acts as a pump that draws recirculated exhaust gas from the exhaust gas through the low pressure exhaust gas recirculation loop into the intake air flow path.

Typically, flowing low pressure exhaust gas through a low pressure exhaust gas recirculation circuit at low engine speeds is problematic due to its inherent low pressure. In some prior art systems, a restrictor valve is placed in the exhaust pipe downstream of where exhaust gas enters the low-pressure exhaust gas flow passage, thereby encouraging the flow of low-pressure exhaust gas through the low-pressure exhaust gas recirculation loop. That is, the restrictor valve is located between the juncture (of the low-pressure exhaust gas flow path and the exhaust pipe) and the position "EX" at which the exhaust gas enters the atmosphere. Under this arrangement, when low pressure exhaust gas flow is required, the low pressure exhaust gas recirculation control valve 9 is opened and the restrictor valve is adjusted to increase the pressure in the exhaust pipe, thereby providing the end of the exhaust pipe for the low pressure exhaust gas recirculation circuit and the pressure difference between the intake side of the low-pressure exhaust gas recirculation circuit. However, increasing the pressure in the exhaust pipe is disadvantageous because it reduces the flow through the two exhaust aftertreatment devices 31, 32 and through the turbine 12, thereby further weakening the turbocharger when the deactivatable cylinders of the engine 5 are deactivated. Compressor 10 provides pressurization capability.

The application of low pressure exhaust gas recirculation is also problematic at low engine loads due to the low cylinder temperatures resulting from low load operation. This can be improved by deactivating the deactivated cylinders, at which point the load on each cylinder increases, increasing the cylinder temperature in the cylinders that are still running.

Therefore, it is often difficult to combine low pressure exhaust gas recirculation and cylinder deactivation.

The ability to operate the engine 5 with cylinder deactivation under low pressure exhaust gas recirculation is significantly enhanced by using the electric supercharger 20 proposed by the present invention, since the electric supercharger 20 assists the flow of low pressure exhaust gas.

It is also to be understood that if the pressure entering the cylinder is greater than the pressure in the exhaust manifold 7, the use of the electric booster 20 can produce a positive pumping effect rather than the usual pumping losses.

Referring to FIG. 3 , a method 100 of controlling an engine system in accordance with the present invention is shown.

The method starts at block 110 , which in the case of a motor vehicle such as motor vehicle 1 may be a switch-on event. The method then advances to box 115 where it is determined whether cylinder deactivation is required for efficient operation of the engine 5 . This determination may be made by electronic controller 40 or another controller such as an engine control unit. As is known in the art, a number of factors need to be considered when deciding whether to deactivate any of the deactivatable cylinders of the engine 5 . However, in the case of the example, the first test is whether the current engine speed (N) is within a predetermined operating range. That is, _Nmin < N <_Nmax; where N is the current engine speed, Nmin is _{the lowest} engine speed at which cylinder deactivation is implemented, which is usually determined based on NVH considerations of the engine 5, and _Nmax is the cylinder deactivation implemented The maximum engine speed is generally determined based on the maximum speed at which cylinder deactivation can be deactivated without causing damage to the engine 5 .

The second test is whether the desired torque ( _TDemand ) is below the torque limit TE _{-BoostLimit ,} which in this case is expected to be deactivated at the deactivable cylinders of Engine 5 Maximum torque is generated under conditions in which the exhaust gas temperature in the enabled cylinder does not exceed a predetermined limit. It is to be understood, however, that other factors may be applied in addition to or instead of cylinder temperature limits such as turbine 12 exhaust temperature limits or cylinder high pressure limits. Temperature and/or pressure can be modeled, or sensors can be provided to measure it.

Therefore, in this case, if in fact _Nmin <N< _Nmax , and _Tdemand is less than _{Telectric booster limit} , deactivation will occur and the method proceeds to block 120, if either condition is not satisfied If so, the method goes back to block 115.

If the above conditions are met, the method advances to box 120 whereupon the deactivatable cylinders of the engine 5 are deactivated. Those skilled in the art will appreciate that the number of cylinder deactivations may depend on desired load and engine configuration. For example, in the case of an eight cylinder engine, four cylinders may be deactivated for very low engine load operation, but only two cylinders may be deactivated for medium engine load operation. Such engines are sometimes called variable displacement engines.

The method then proceeds to block 130 where it is determined whether the electric booster 20 is enabled. In the case of the example, the electric booster 20 is activated if the deactivatable cylinders have been deactivated. But understand that for this to happen, _Nmin <N< _{Nmax must actually be Nmin<N<Nmax} , and _TDemand must be less than TE _{-Boost Limit} , so these are the cylinders or cylinders that are activated and deactivatable for the E-Boost 20 A practical requirement for deactivation. It is also to be understood that in this case the torque limit T _{e-supercharger limit} is based on the relationship between the engine speed and the expected exhaust gas temperature in the non-deactivated cylinders.

While in the described preferred embodiment the test for determining whether a deactivatable cylinder should be deactivated is the same as the test for determining whether the electric booster 20 should be activated, this need not be the case. For example, deactivatable cylinders may be deactivated when the engine speed is less _{than Nmin} , such as when the engine is idling and substantially no torque is required beyond that required to keep the engine 5 running at idle speed. In this case, the use of the electric booster 20 is not required, so cylinder deactivation and the activation of the electric booster 20 will have different conditions.

In this case, the electric booster 20 is only activated when the deactivatable cylinders are deactivated, practically _Nmin <N< _Nmax and _Tdemand is less than _{Tebocharger limit} .

If these requirements are not met, the method loops back to box 115 . Note that if the cylinder deactivation condition is the same as the electric supercharger 20 enabling condition, the electric supercharger 20 enabling test becomes "is the deactivatable cylinder deactivated?" If "Yes", then enable the electric supercharger; if "No", the electric supercharger 20 is not activated.

Note that if the cylinders are not deactivated, there may be a further test to see if the use of the electric booster 20 would be beneficial with all cylinders activated.

If the electric booster 20 has been activated, the method proceeds to box 140 where the electric booster 20 is controlled by the electronic controller 40 to provide the currently required torque in the most efficient manner. For example, assuming that the desired torque requires a boost pressure of 0.4 Bar (0.4×10 ⁵ N/m ² ), this can be provided by various combinations of boost provided by the turbocharger 10 and boost provided by the electric supercharger 20 . In general, it is preferred to provide as much boost as possible with the electric supercharger 20 as this allows the turbocharger 10 to operate with minimal exhaust back pressure on the engine 5 . For example, the ratio could be 0.3 Bar (0.3×10 ⁵ N/m ² ) boost from the electric supercharger 20 and 0.1 Bar (0.1×10 ⁵ N/m ² ) from the turbocharger 10 . It will be appreciated that the turbocharger 10 will always produce a small amount of boost since it will continue to spin during cylinder deactivation.

After block 140, test in block 150 to know whether the switch disconnection event has occurred, if "no", then the method advances to frame 155, but if the switch disconnection event has occurred, then method 100 in Block 190 ends.

In block 155, check whether the electric booster activation is still valid, that is to say whether all the conditions required for the electric booster 20 activation are still met, if "yes", then the method returns to block 140, but if "no ", then the method returns to block 115.

It will be appreciated that if the cylinder deactivation conditions and the electric booster 20 activation conditions are the same as in the preferred embodiment, then box 130 can be eliminated since the same check is performed in box 115 .

Although the invention has been described by way of example with reference to a four-cylinder diesel engine, it is to be understood that it is not limited to this application and may be applied with beneficial effect to any multi-cylinder engine having at least one deactivatable cylinder.

It is also to be understood that while electronic controller 40 is shown as a single unit, it may be composed of several electronic controllers and/or electronic processors connected to carry out the described functions.

Those skilled in the art will appreciate that while the invention has been described by way of example with reference to one or more implementations, it is not limited to the disclosed implementations and that alternative implementations may be constructed without departing from the scope of the appended claims scope of the invention.

Claims (13)

1. An engine system comprising a multi-cylinder engine having at least one deactivatable cylinder; a turbocharger having a compressor and a turbine operatively connected to said engine; an electric supercharger connected to the compressor of the turbocharger to selectively supply air to the compressor of the turbocharger at increased pressure; and an electronic controller for controlling activation of the electric supercharger, wherein the electronic controller is operable when at least one cylinder of the engine is deactivated and at least one electric supercharger operating condition is met to activate the electric supercharger, wherein, when activated, the electric supercharger is controlled by the electronic controller to meet the engine's torque demand up to when the engine's the maximum torque available from the engine while the deactivatable cylinders are in their deactivated state and utilizing the turbocharger and the electric supercharger to increase mass flow rate or intake pressure, and if the demand Above the maximum torque limit for more than a period of time, the electronic controller switches the engine out of the deactivated mode. 2. The system of claim 1, wherein the electric supercharger operating condition is an engine speed range, and the electronic controller is operable to operate the engine within a speed range defined by a lower speed limit and an upper speed limit Only the electric booster is enabled in the case of 3. The system of claim 1, wherein the electric supercharger operating condition is that the engine torque demand is not greater than a maximum engine torque limit for the current engine speed. 4. The system of claim 1 wherein the electric supercharger operating condition is that the engine torque demand is greater than a minimum engine torque limit for the current engine speed. 5. The system of claim 1, wherein said system further comprises a low pressure exhaust gas recirculation loop having a low pressure exhaust gas recirculation control valve controlled by said electronic controller and when The electric supercharger increases flow through the low pressure exhaust gas recirculation circuit when the electric supercharger is activated and the low pressure exhaust gas recirculation control valve is open. 6. The system of claim 5, wherein said engine system includes at least one exhaust aftertreatment device connected downstream of said turbine of said turbocharger, and said A low pressure exhaust gas recirculation loop includes a low pressure exhaust gas flow passage extending from a location downstream of the at least one aftertreatment device to a location upstream of the electric supercharger. 7. The system of claim 1, wherein the electric booster comprises an electric motor driven compressor. 8. A motor vehicle having an engine system as claimed in any one of claims 1 to 7. 9. The motor vehicle of claim 8, wherein the motor vehicle is a motor vehicle having an energy recycling system for capturing electrical energy during use of the motor vehicle and storing it in an electrical energy In the storage device, the electric energy stored in the electric energy storage device is used to provide power for the electric supercharger. 10. A method of controlling an engine system comprising a multi-cylinder engine having at least one deactivatable cylinder, a turbocharger and an electric supercharger, wherein said method comprises when deactivating at least one cylinder of said engine and when at least one electric supercharger operating condition is met, the electric supercharger is activated, wherein, when activated, the electric supercharger is controlled by an electronic controller to meet the torque demand of the engine, the engine torque demand up to that available from the engine when the deactivatable cylinders of the engine are in their deactivated state and using the turbocharger and the electric supercharger to increase mass flow rate or intake pressure a maximum torque limit, and the electronic controller switches the engine out of the deactivated mode if the demand is above the maximum torque limit for an extended period of time. 11. The method of claim 10, wherein the at least one electric supercharger operating condition is an engine speed range, and the method further comprises operating the engine within a speed range defined by a lower speed limit and an upper speed limit. In this case only the electric booster is enabled. 12. The method of claim 10, wherein the electric supercharger operating condition is that the torque demand of the engine is not greater than a maximum engine torque limit for the current engine speed. 13. The method of claim 10, wherein the electric supercharger operating condition is that the engine torque demand is greater than a minimum engine torque limit for the current engine speed.