Patent Description:
The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to a truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles such as cars.

Most trucks today are powered by internal combustion engines having cylinders in which fuel is combusted whereby exhaust gases are generated. The exhaust gases are normally transferred to an exhaust gas aftertreatment system (EATS) where the exhaust gases are treated and at least some of the pollutants in the exhaust gases are converted into harmless substances. The EATS may comprise an oxidation catalyst suitable for converting hydrocarbons and carbon monoxide to carbon dioxide and water, a particulate filter catching soot and ashes, and a reduction catalysts reducing nitrogen oxides to nitrogen, sometimes with the help of a reductant fluid. During cold start or low exhaust temperature it is desirable to heat the EATS to its working temperature, and occasionally it is desirable to heat the EATS to a higher temperature than the normal exhaust temperature. Such events could be to burn off collected soot, poisonous matter, e.g. sulphur, collected on the catalysts, or deposits created by the reductant. These elevated temperatures can be reached by adding fuel to the oxidation catalyst. For instance, the exhaust gas may be enriched by uncombusted or partially combusted fuel, by means of late post injection in the engine. The hydrocarbons of the injected fuel are burnt on the catalyst, thereby increasing the temperature.

In order to maintain a low NOx formation, internal combustion engines may be fluidly connected to exhaust gas recirculation (EGR) conduits for recirculation of some of the exhaust gas. The recirculated exhaust gas dilutes the air/fuel mixture just enough to reduce combustion temperatures to a level that reduces the reaction between nitrogen and oxygen that forms NOx.

While these two methods, i.e. late post injection and EGR, are each advantageous for their particular purpose, combining the two, however, may result in problems. A problem that may arise is that the high concentration of hydrocarbons obtained from the late post injection may negatively affect the EGR. More particularly, an EGR conduit is normally provided with an EGR cooler. The high concentration of hydrocarbons may affect the EGR cooler negatively by condensing on the cold heat exchanger surface, which will reduce the cooling performance of the cooler and as a consequence reduce the efficiency of the engine. Further the high hydrocarbon concentration in the EGR and hence in the intake air will affect the combustion in the cylinders negatively, burning off early in the compression stroke.

<CIT> discloses a method for operating an internal combustion engine having two first cylinders and two second cylinders. EGR gases are only taken from the first cylinders and an EGR valve controls the quantity of the exhaust gas recirculated to the air tract of the internal combustion engine. The temperature of the exhaust gases from the internal combustion engine is increased by post-injecting fuel, the fuel being oxidized by a catalytic converter. Post-injection takes place only in the second cylinders, the exhaust gases of which are not recirculated.

Although the method of <CIT> reduces the risk of the uncombusted hydrocarbons entering the EGR by only recirculating form the first cylinders and only post-injecting in the second cylinders, it would be desirable to provide a more flexible internal combustion engine system, without these limitations.

<CIT> discloses a diesel engine system which includes a diesel engine having a first exhaust segment and a second exhaust segment. A filter filters exhaust gas from the first and second exhaust segments. A flow control valve selectively re-circulates a portion of exhaust from the first exhaust segment into the diesel engine. An injector system injects fuel into exhaust flowing through the second exhaust segment. The fuel is combusted to regenerate the filter.

<CIT> discloses an internal combustion engine having at least one first cylinder and at least one second cylinder. An exhaust gas recirculation duct is connected to the outlet of the first cylinder, and is connected by a first exhaust gas recirculation branch to a first intake duct of the first cylinder and by a second exhaust gas recirculation branch to a second intake duct of the second cylinder. A first valve device is arranged in the first exhaust gas recirculation branch. A second valve device is arranged in the second exhaust gas recirculation branch. A third valve device is arranged in an exhaust gas recirculation connecting pipe. The first, second and third valve devices are independently controllable, so that variable modes of operation of the first and second cylinders are possible.

<CIT> discloses a power system comprising an engine that produces exhaust and includes an exhaust gas recirculation (EGR) system. The EGR system includes an EGR conduit routing an exhaust flow back to the engine, a restriction valve disposed in the EGR conduit, and a control valve disposed in the EGR conduit in series with the restriction valve.

An object of the invention is to provide an internal combustion engine system, which alleviates the above mentioned drawbacks of the prior art.

According to a first aspect, the object is achieved by an internal combustion engine according to claim <NUM>. The internal combustion engine system comprises.

The invention is based on the realization that by providing two EGR valves, in a normal operating mode, exhaust gas from both sets of cylinders may be recirculated, while in a temperature-increasing operating mode, one of the EGR valves may be closed so as to only allow recirculation from one set of cylinders, and late post injecting fuel in the other set of cylinders. This allows increased flexibility and more options for controlling the handling of exhaust gases from the first and second set of cylinders. Furthermore, an advantage of having two EGR valves, i.e. allowing recirculation of exhaust gases from both sets of cylinders in a normal operating mode, is that an equal amount of exhaust gas can be recirculated from both sets of cylinders, thereby avoiding imbalance and achieving higher efficiency.

It should be understood that in this application, a "set" can include any number of items, i.e. it can be a single item or it can be plural items. Accordingly, a set may include one or more cylinders in an internal combustion engine. The term "set" is thus used to distinguish one or more cylinders from one or more other cylinders. This is reflected in claim <NUM> which discloses a first set of one or more cylinders and a second set of one or more cylinders which is separate from the first set. Furthermore, it should be understood that, for simplicity and ease of reading, in this application reference will be made to the "first set of cylinders" and to the "second set of cylinders", instead of the first "set of one or more cylinders" and the "second set of one or more cylinders". Thus, it should be understood that as far as the term a "set of cylinders" is concerned, the number of cylinders in each set may for example be one, two, three, four or more.

It should be understood that in this application "late post injection" of fuel means that fuel is injected after a main injection in such way that the later injected fuel remains uncombusted or at least partly uncombusted when exiting the cylinder. The late post injection may, for instance, occur before (such as right before) an exhaust valve opens so that uncombusted fuel may pass to the EATS.

It should be understood that various types of fuels may be used in connection with the present invention. For instance, the fuel may be diesel (hydrocarbons), alcohols (such as ethanol), methane, ethers (such as dimethyl ether). It should also be understood that any hydrocarbons may be partially oxidized (for instance, because the fuel was provided in such state or because the hydrocarbons have oxidized in the cylinders).

It should also be understood that in this application a "controller" may include any suitable electrical, mechanical, magnetic, pneumatic and/or hydraulic, etc. means for controlling the different components (such as the EGR valves and the fuel injector) of the system, in particular for controlling how, when and/or for how long the components should be activated/inactivated. The controller may include a non-transitory computer-readable storage medium storing one or more programs configured to be executed by one or more processors of the system, the one or more programs comprising instructions for performing the steps defined in the claims.

In the internal combustion engine system, the turbine may suitably be connected to a compressor for compressing intake air. The turbine is driven by the exhaust gas that flows to the EATS. The EATS is suitably located downstream of the turbine. Furthermore, both the first and the second EGR valves may suitably located upstream of the turbine. Thus, exhaust gas from the first and second sets of cylinders may suitably be recirculated upstream of the turbine.

In the internal combustion engine system, there may suitably be provided an EGR cooler in the EGR conduit for cooling recirculated exhaust gas.

According to at least one exemplary embodiment, the controller is configured to determine a desired EGR flow and to control the opening of the first EGR valve so that the desired EGR flow is recirculated from the first set of cylinders to the inlet of the internal combustion engine. This has the advantage that, in a temperature-increasing operating mode, while the second EGR valve is closed for enabling late post injection in the second set of cylinders, the first EGR valve may be opened to a desired degree for recirculating the exhaust gas from the first set of cylinders for reducing NOx formation.

According to at least one exemplary embodiment, the flow of recirculated exhaust gas delivered from the EGR conduit to said inlet continues to flow from said inlet to both the first and second sets of cylinders. This is beneficial since an improved balance in the system is obtained, in relation to what may be the case if exhaust gas is only recirculated to one of the first and second sets of cylinders.

According to at least one exemplary embodiment, the controller is configured to control the first and second EGR valves so that a desired ratio of recirculated flow of exhaust gas to the EGR conduit relative to the amount of air entering the inlet of the internal combustion engine is obtained. This has the advantage that the air-to-fuel ratio, or more specifically the oxygen-to-fuel ratio may be controlled to a desired level to meet performance and emission objectives. In a normal operating mode, both the first and the second EGR valve may be controlled so that a suitable amount of exhaust gas is recirculated and so that a desired oxygen-to-fuel ratio is obtained. In a temperature-increasing operating mode, the opening degree of the first EGR valve may be appropriately controlled to obtain the desired ratio. For instance, if in the normal operating mode both the first and the second EGR valve had a similar opening degree, in the temperature-increasing operating mode, the closing of the second EGR valve may be compensated by increasing the opening degree of the first EGR valve so as to maintain the flow of exhaust gas to the EGR conduit at a desired level.

According to at least one exemplary embodiment, when the second EGR valve is closed all exhaust gas from the second set of cylinders flows to the exhaust gas aftertreatment system. Hereby, even though late post injection is performed in the second set of cylinders, the risk of uncombusted hydrocarbons entering the EGR conduit is avoided.

According to the invention, the second EGR valve is additionally configured to control flow of exhaust gas from the first set of cylinders to the EGR conduit. By this arrangement, other control possibilities are achieved. In particular, in combination with an EGR cooler advantages may be obtained. According to the invention, the internal combustion engine system comprises an EGR cooler provided in the EGR conduit, wherein the first EGR valve is fluidly connected to the EGR conduit downstream of the EGR cooler. This may be advantageous at cold start conditions, since some of the recirculated gas may bypass the EGR cooler. Thereby, it is possible to control the amount of recirculated gases that should not be cooled. The non-cooled gas provides hotter inlet gas to the cylinders, which in turn results in hotter exhaust gas at cold start. Because there is provided a second EGR valve configured to control flow of exhaust gas from both sets of cylinders (as stated above), the exhaust gases passing through the second EGR valve are suitably led through the EGR cooler for appropriate cooling. Thus, the amount of cooled versus non-cooled recirculated gases may be efficiently controlled when late post injection is not performed.

According to at least one exemplary embodiment, the oxidation catalyst is an electrically heated oxidation catalyst. This is advantageous since, by heating the catalyst, a good conversion efficiency may be obtained even though the exhaust gas is not at a temperature that would otherwise be considered a high enough temperature. An electric heater may be provided in front of the catalyst to heat the catalytic substrate, or the catalytic substrate may form part of the electric heater as such.

According to at least one exemplary embodiment, the controller is configured to heat the oxidation catalyst to the light-off temperature for hydrocarbons present in the injected fuel. Due to cracking of the fuel, e.g. diesel, by the late post injection and the electrical heating, the exhaust gas does not need to be at a temperature suitable for fuel vaporisation and light-off.

According to at least one exemplary embodiment, the internal combustion engine system comprises an exhaust throttle, wherein the exhaust throttle is provided downstream of the turbine, or the exhaust throttle is provided in an exhaust conduit downstream of the first and second EGR valves and upstream of the turbine, wherein the controller is configured to control the exhaust throttle for further controlling the flow to the EGR conduit. By the provision of an exhaust throttle, an additional controlling component is available for controlling the flow to the EGR conduit. Furthermore, the obstruction of flow of exhaust gas increases the temperature of the exhaust gas.

According to at least one exemplary embodiment, the internal combustion engine system comprises a compressor or pump fluidly connected to the EGR conduit, wherein the controller is configured to control the compressor or pump for controlling the flow in the EGR conduit. Thus, the flow in the EGR conduit may be boosted by providing an additional flow control component in the form of a compressor or pump which may drive the EGR flow when the pressure at the intake is higher than the pressure at the exhaust manifold to the EGR conduit.

According to a second aspect of the invention, the object is achieved by a vehicle comprising an internal combustion engine system according to the first aspect. The vehicle may, for instance, be a truck, a bus, construction equipment or a car.

According to a third aspect of the invention, the object is achieved by a method of operating an internal combustion engine system which comprises.

It should be understood that the control unit of the system of the first aspect of the invention is configured to perform the steps and include the features of any one of the embodiments of the method according to the third aspect of the invention.

According to at least one exemplary embodiment, the method of the third aspect, comprises the further steps of:.

The step of controlling the opening of the first EGR valve may be performed before, during or after closing the second EGR valve.

The advantages of the various embodiments of the third aspect are largely analogous to the advantages of the corresponding embodiments of the first aspect, and for the sake of brevity, all will not be repeated here. Exemplary embodiments of the method of the third aspect are defined in claims <NUM>-<NUM>.

According to a fourth aspect of the invention, the object is achieved by means of a computer program comprising program code means for performing the steps of the method according to the third aspect and any embodiments thereof, when said program is run on a computer.

According to a fifth aspect of the invention, the object is achieved by a computer readable medium comprising a computer program comprising program code means for performing the steps of the method according to the third aspect and any embodiments thereof, when said program is run on a computer.

According to a sixth aspect of the invention, the object is achieved by a control unit for controlling the exhaust temperature in an internal combustion engine, the control unit being configured to perform the steps of the method according to the third aspect and any embodiments thereof. The control unit may suitably be, or be included in, or comprise, the controller of the system according to the first aspect.

<FIG> is a schematic view illustrating a vehicle <NUM> comprising an internal combustion engine system in accordance with at least one exemplary embodiment of the invention. In this example, the vehicle <NUM> is illustrated in the form of a truck, powered by an internal combustion engine <NUM>. However, the present invention may well be implemented also in other types of vehicles powered by an internal combustion engine, such as busses, construction equipment and passenger cars.

The vehicle <NUM> is illustrated as being provided with an air intake arrangement comprising an air intake <NUM> in which air enters and moves vertically down an air duct <NUM>. The air flows to an air cleaner <NUM> and then to an internal combustion engine system which comprises the internal combustion engine <NUM>. In the depicted embodiment the air cleaner <NUM> is located in a lower region of the vehicle <NUM> and the air intake <NUM> is located in a higher region of the vehicle <NUM>, more specifically the air cleaner <NUM> is located directly behind a vehicle cab <NUM>, whereas the air intake <NUM> is located on top of the cab <NUM>. It should, however, be noted that the locations of the parts detailed above may well be otherwise, as long as air is fed to the internal combustion engine system.

<FIG> is a schematic view illustrating an internal combustion engine system <NUM> in accordance with at least some exemplary embodiments of the invention. The system <NUM> comprises an internal combustion engine <NUM>, which in turn comprises a first set of cylinders <NUM> and a second set of cylinders <NUM>, the second set of cylinders <NUM> being separate from the first set of cylinders <NUM>. In this schematic representation of the internal combustion engine <NUM> each one of the first and second sets has three cylinders. However, it should be understood that the number of cylinders in each one of the first and second sets could be fewer or more. For instance, a set may have one, two, four or more cylinders.

Each cylinder has an outlet connected to a respective exhaust duct. The three exhaust ducts <NUM> from the first set of cylinders <NUM> are joined at a first junction <NUM>, and the three exhaust ducts <NUM> from the second set of cylinders <NUM> are joined at a second junction <NUM>. From the first junction <NUM>, the exhaust gas is allowed to flow either to an exhaust gas recirculation (EGR) conduit <NUM> for recirculating the exhaust gas, or to an exhaust gas aftertreatment system (EATS) <NUM>.

The internal combustion engine system <NUM> comprises a turbine <NUM> connected to a compressor (not illustrated) for compressing intake air. The turbine <NUM> is driven by the exhaust gas that flows to the EATS <NUM>. In the illustrated exemplary embodiment, the turbine <NUM> is located upstream of the EATS <NUM>. In some exemplary embodiments, the exhaust gas from the first set of cylinders <NUM> and the exhaust gas from the second set of cylinders <NUM> may have separate inflows to the turbine <NUM>. In other exemplary embodiments, the exhaust gas from the first and second set of cylinders <NUM>, <NUM>, may, as illustrated in <FIG> have one common inflow to the turbine <NUM>.

A first EGR valve <NUM> is provided for controlling the flow of exhaust gas from the first set of cylinders <NUM> to the EGR conduit <NUM>. Thus, when the first EGR valve <NUM> is closed, all or substantially all the exhaust gas from the first set of cylinders <NUM> will pass to the EATS <NUM> via the turbine <NUM>. By setting the opening degree of the first EGR valve <NUM>, the amount of exhaust gas recirculated via the EGR conduit <NUM> can be regulated. The first EGR valve <NUM> may be an electric EGR valve or a mechanical (e.g. pneumatic or hydraulic) EGR valve. For instance, the first EGR valve <NUM> may comprise a computer-controllable stepper motor to open and close the EGR valve or a computer-controllable solenoid vacuum valve, or the like.

The system <NUM> comprises a controller <NUM> which is configured to determine a desired EGR flow and to control the opening of the first EGR valve <NUM> so that the desired EGR flow is recirculated from the first set of cylinders <NUM> to the inlet <NUM> of the internal combustion engine <NUM>. The controller <NUM> may, for instance, be any suitable type of computer or microcomputer having one or more processors. The controller <NUM> may include a non-transitory computer-readable storage medium storing one or more programs configured to be executed by one or more processors of the system <NUM>, the one or more programs comprising instructions for controlling the opening and closing of the first EGR valve <NUM>.

Similarly, the exhaust gas from the second junction <NUM> may be led to the EATS <NUM> and/or to the EGR conduit <NUM>. Thus, there is provided a second EGR valve <NUM>, which is controllable by the controller <NUM> to either close the second EGR valve <NUM>, in which case substantially all exhaust gas passes to the EATS <NUM> via the turbine <NUM> or to open the second EGR valve <NUM> to bleed off exhaust gas for recirculation to the inlet <NUM> of the internal combustion engine <NUM> via the EGR conduit <NUM>. The second EGR valve <NUM> is suitably of the same type as the first EGR valve <NUM>, although having different valve types are conceivable.

As illustrated in <FIG>, for the exhaust gas flowing from the first as well as the second sets of cylinders <NUM>, <NUM>, both the first and the second EGR valves <NUM>, <NUM> may be located upstream of the turbine.

The controller <NUM> is configured to control the first EGR valve <NUM> and the second EGR valve <NUM> so that a desired ratio of recirculated flow of exhaust gas to the EGR conduit <NUM> relative to the amount of air entering the inlet <NUM> of the internal combustion engine <NUM> is obtained. Thus, in a normal operating mode, a balanced recirculation may be provided by opening both EGR valves <NUM>, <NUM>. The controller controls the EGR valves <NUM>, <NUM> so that the amount of exhaust gas that is recirculated is enough to sufficiently dilute the air/fuel mixture to reduce combustion temperatures to a level that reduces the reaction between nitrogen and oxygen that forms NOx.

It should be noted that as an alternative to, or in addition to, the first and second EGR valves <NUM>, <NUM>, it would be conceivable to (instead of joining the exhaust ducts <NUM>, <NUM> at a junction <NUM>, <NUM>) connect the EGR conduit <NUM> to each one of the exhaust ducts <NUM>, <NUM> and provide an individual EGR valve in each exhaust duct <NUM>, <NUM> (or in one or more exhaust ducts <NUM>, <NUM>).

The system <NUM> further comprises a fuel injector <NUM> for injection of fuel into at least one cylinder of the second set of cylinders <NUM>. Although not illustrated here, any suitable fuel injector may be provided for injecting fuel into the first set of cylinders <NUM>. Furthermore, it should be understood that fuel is injected into each one of the cylinders in the first and second set of cylinders <NUM>, <NUM>, however, not all of them will be for late post injection, which will be discussed in the following. It should also be understood that any suitable number of fuel injectors may be provided for injecting fuel into any one of the cylinders. Furthermore, it should be understood that the fuel injectors may be individually controllable so as to enable different types of injections to each cylinder, if desired.

As explained above, the controller <NUM> may open or close the second EGR valve <NUM>. In accordance with the inventive concept, the controller <NUM> is configured to control the closing of the second EGR valve <NUM>, thereby preventing flow of exhaust gas from the second set of cylinders <NUM> to the EGR conduit <NUM>, and configured to activate the fuel injector <NUM> for late post injection of fuel into at least one cylinder of the second set of cylinders <NUM> when the second EGR valve <NUM> is closed, so that at least a part of the fuel that exits the second set of cylinders <NUM> is uncombusted. Thus, the late post injection takes place at such a stage that the injected fuel remains uncombusted or at least partly uncombusted when exiting the cylinder. The late post injection may, for instance, occur right before an exhaust valve (not shown) opens so that uncombusted fuel, such as including hydrocarbons, may pass to the EATS <NUM>.

It should be understood that the controller <NUM> may control one or more fuel injectors for late post injection of fuel into more than one cylinder of the second set of cylinders <NUM>, for instance into two cylinders or into all cylinders (which in the present example would be into three cylinders). The fuel injector <NUM> may suitably form part of an electronic injection system, which may comprise a small computer or electronic control unit which controls fuel mixture, valve timing, etc. The electronic control unit may collect sensor data such as air pressure, air intake temperature, etc. based on which it operates. Such an electronic control unit may form part of the controller <NUM> or may receive instructions/input signals from the controller <NUM>.

The EATS <NUM> is arranged to receive and treat exhaust gas which is not recirculated in the EGR conduit <NUM>. The EATS <NUM> comprises an oxidation catalyst <NUM> for combustion of the late post injected fuel or derivates thereof. It should be understood that the EATS <NUM> may comprise other components as well, even though not illustrated. In other words, the uncombusted fuel, for example including hydrocarbons, or derivates thereof are burnt on the catalyst <NUM>, thereby increasing the temperature. When the controller <NUM> has closed the second EGR valve <NUM>, all or substantially all exhaust gas from the second set of cylinders <NUM> flows to the EATS <NUM>.

The oxidation catalyst <NUM> may suitably be an electrically heated oxidation catalyst. A separate electric heater may be provided for heating the substrate of the catalyst <NUM>, or the catalytic substrate itself may form part of an electric heater. The electric heater may suitably be powered by any energy storage means, such as a traction battery, an auxiliary battery, an accumulator, etc. The controller <NUM> may be configured to heat the oxidation catalyst <NUM> to the light-off temperature for hydrocarbons present in the injected fuel.

In operation, when the controller <NUM> determines that the temperature of the exhaust gas should be increased, the controller <NUM> starts operating the internal combustion engine system <NUM> in a temperature-increasing operating mode. In the normal operating mode, both the first EGR valve <NUM> and the second EGR valve <NUM> may be opened, however, when switching to the temperature-increasing operating mode, the controller <NUM> will close the second EGR valve <NUM>, and when the second EGR valve <NUM> has been closed, the controller <NUM> will control the fuel injector <NUM> to late post inject fuel into the one or more cylinders of the second set of cylinders <NUM>, such that uncombusted or at least partly uncombusted fuel exits the second set of cylinders <NUM> and is transported to the oxidation catalyst <NUM> where they will burn. By separating the first and second sets of cylinders <NUM>, <NUM> and allowing the first EGR valve <NUM> to remain open, an efficient temperature increase is achieved without negatively affecting the recirculation in the EGR conduit <NUM>. Thus, the invention provides for a flexible switching between a balanced normal operating mode and a temperature-increasing operating mode.

Suitably, the flow of recirculated exhaust gas delivered from the EGR conduit <NUM> to the inlet <NUM> continues to flow from said inlet <NUM> to both the first and second sets of cylinders <NUM>, <NUM>. Thus, although the second EGR valve <NUM> may be closed and late post injection is performed in the second set of cylinders <NUM>, any gas recirculated form the first set of cylinders <NUM> may suitably be guided through the EGR conduit back to all cylinders <NUM>, <NUM> (via the inlet <NUM>).

<FIG> and <FIG> are schematic views illustrating internal combustion engine systems in accordance with at least some other exemplary embodiments of the invention. Components of the internal combustion engine system which correspond to the components already presented in connection with the exemplary embodiment of <FIG> are denoted with the same reference numerals.

The internal combustion engine system <NUM>' in <FIG> and the internal combustion engine system <NUM>" in <FIG> may, in addition to the components presented in <FIG>, further comprise an exhaust throttle <NUM>. In <FIG> and <FIG>, two alternative locations are illustrated for the exhaust throttle <NUM>. In at least some exemplary embodiments, as illustrated in <FIG>, the exhaust throttle <NUM> may be located downstream of the turbine <NUM> (in <FIG> illustrated as located between the turbine <NUM> and the oxidation catalyst <NUM>). In other exemplary embodiments, as illustrated in <FIG>, the exhaust throttle <NUM> may be provided in an exhaust conduit <NUM> downstream of the valves <NUM>, <NUM> and upstream of the turbine <NUM>. In either case, the controller <NUM> may be configured to control the exhaust throttle <NUM> for further controlling the flow to the EGR conduit <NUM>. In the second case (<FIG>), i.e. the exhaust throttle <NUM> being provided downstream of the EGR valves <NUM>, <NUM> and upstream of the turbine <NUM> the controller <NUM> may also be used for controlling the exhaust throttle <NUM> for balancing the flow to the turbine <NUM>. In other exemplary embodiments, it is even conceivable to provide two throttles (not shown) upstream of the turbine <NUM>, one for each EGR valve <NUM>, <NUM>. In such cases, one throttle would be located in a first exhaust branch <NUM> downstream of the first EGR valve <NUM>, and the other throttle would be located in a second exhaust branch <NUM> downstream of the second EGR valve <NUM>.

<FIG> and <FIG> also illustrate that the systems <NUM>' and <NUM>" may comprise a compressor or pump <NUM> fluidly connected to the EGR conduit, wherein the controller <NUM> is configured to control the compressor or pump <NUM> for controlling the EGR conduit. Thus, the flow in the EGR conduit <NUM> may be boosted by providing an additional flow control component in the form of a compressor or pump <NUM> which can drive the EGR flow when the pressure at the intake is higher than the pressure at the exhaust manifold to the EGR conduit <NUM>.

It should be understood that although the drawings illustrate certain combinations of components, these are only exemplary embodiments illustrated for explanatory purposes, and other embodiments are readily conceivable. For instance, the various components (such as pump <NUM>, turbine <NUM>, throttles <NUM> etc.) illustrated in <FIG> and <FIG> can be combined in various ways and it is not necessary to include all features in an embodiment even if they are illustrated in the same drawing. For instance, in some exemplary embodiments, the pump <NUM> may be included, while the throttle <NUM> may be omitted. Conversely, in other embodiments, one or more throttles <NUM> may be included, while the pump <NUM> is omitted. In other embodiments the throttle <NUM> as well as the pump <NUM> may be omitted.

<FIG> is a diagram illustrating a method <NUM> for operating an internal combustion engine system in accordance with at least one exemplary embodiment of the invention. The internal combustion engine system may, for instance, be in accordance with the one illustrated in <FIG>, and/or as described elsewhere in this disclosure.

As illustrated in <FIG>, the method <NUM> comprises:.

<FIG> is a diagram illustrating optional steps S3-S8, which may be implemented in exemplary embodiments of a method <NUM> for operating an internal combustion engine system. It should be understood that in some exemplary embodiments several of the optional steps may be performed in combination (either simultaneously or at different points in time), and that in other exemplary embodiments, only one or a few of the optional steps are performed. Accordingly, it should be understood that, although optional steps S3, S5, S6, S7 and S8 have, for simplicity, been illustrated as parallel steps, these optional steps are not mutually exclusive, as will be exemplified further below.

Thus, in addition to the first step S1 and the second step S2, which are the same as in <FIG>, the following steps may be included in the method <NUM>.

As illustrated in <FIG>, the method <NUM> may comprise:.

It should be noted that although the third step S3 and the fourth step S4 are illustrated as being performed after the second step S2, in other embodiments, the third step S3 and the fourth step S4 may be performed before the first step S1, or between the first step S1 and the second step S2, or simultaneously with either one of steps S1 and S2.

For instance, when in the internal combustion engine is operated in a normal operating mode, both the first EGR valve and the second EGR valve may be opened. When it is determined that the system should be switched to operate in a temperature-increasing operating mode, the first step S1 and the second step S2 may be performed. The third step S3, i.e. determining a desired EGR flow may already have been performed (e.g. by preprograming a control unit, such as the controller <NUM> in <FIG>) before switching. Therefore, when the second EGR valve is closed in the first step S1, the first EGR valve may need to be opened to a larger degree for compensating for the loss of EGR flow from the second set of cylinders. Thus, in that case, the fourth step S4 may for instance be performed simultaneously with or just after the first step S1.

<FIG> also illustrates an optional fifth step S5, in which the oxidation catalyst is electrically heated to the light-off temperature for hydrocarbons present in the injected fuel. Again, although this is illustrated as being performed after steps S1 and S2, it may be performed at any time in the inventive method. In other words, the fifth step S5 of electrically heating the oxidation catalyst may be performed before, or simultaneously with, either one of steps S1-S4. It should also be noted that in some exemplary embodiments the fifth step S5 may be performed in combination with the third and fourth steps S3-S4 (in any order or simultaneously), while in other exemplary embodiments the fifth step S5 is performed, while the third and fourth steps S3-S4 are omitted.

<FIG> also illustrates that the method may comprise, in a sixth step S6, to control the compressor or pump for controlling the flow in the EGR unit. Although this is illustrated as being performed after steps S1 and S2, it may be performed at any time in the inventive method. In other words, the sixth step S6 of electrically heating the oxidation catalyst may be performed before, or simultaneously with, either one of steps S1-S5. Furthermore, it should be noted that in some exemplary embodiments the sixth step S6 may be performed in combination with the third and fourth steps S3-S4 and/or the fifth step S5 (in any order or simultaneously), while in other exemplary embodiments the sixth step S6 is performed, while the third and fourth steps S3-S4 and/or the fifth step S5 is/are omitted.

As discussed in connection with <FIG>, <FIG> and <FIG>, in some exemplary embodiments an exhaust throttle may be provided downstream of the turbine, while in other exemplary embodiments an exhaust throttle may instead be provided in an exhaust conduit downstream of the EGR valves and upstream of the turbine. In either one of the alternative embodiments, as illustrated in <FIG>, the method may comprise, in a seventh step S7, to control the exhaust throttle for further controlling the flow to the EGR conduit.

In the case of the exhaust throttle being provided in an exhaust conduit downstream of the EGR valves and upstream of the turbine, the method may comprise, in an eighth step S8, to control the exhaust throttle for balancing the flow to the turbine.

Although the seventh step S7 and the eighth step S8 are illustrated as being performed after steps S1 and S2, they may be performed at any time in the inventive method. In other words, the seventh step S7 and the eighth step S8 may be performed before, or simultaneously with, either one of steps S1-S6. Furthermore, it should be noted that in some exemplary embodiments seventh step S7 and the eighth step S8 may be performed in combination with the third and fourth steps S3-S4, the fifth step S5 and/or the sixth step S6 (in any order or simultaneously), while in other exemplary embodiments the seventh step S7 and the eighth step S8 may be performed while the third and fourth steps S3-S4, the fifth step S5 and/or the sixth step S6 is/are omitted.

The steps of the method illustrated in <FIG> and <FIG> may be performed by:.

<FIG> is a schematic view illustrating an internal combustion engine system <NUM>‴ in accordance with at least some further exemplary embodiments of the invention. Components of the internal combustion engine system <NUM>‴ of <FIG> which correspond to the components already presented in connection with the exemplary embodiment of <FIG> are denoted with the same reference numerals.

Thus, similarly to the internal combustion engine system <NUM> of <FIG>, in the internal combustion engine system <NUM>‴ of <FIG> the first EGR valve <NUM> is provided for controlling the flow of exhaust gas from the first set of cylinders <NUM> to the EGR conduit.

Similarly to the internal combustion engine system <NUM> of <FIG>, in the internal combustion engine system <NUM>‴ of <FIG>, exhaust gas from the second set of cylinders <NUM> may be led to the EATS <NUM> and/or the EGR conduit <NUM>. A second EGR valve <NUM>', which is controllable by the controller <NUM> to either close the second EGR valve <NUM>', in which case substantially all exhaust gas from the second set of cylinders <NUM> passes through the turbine <NUM> to the EATS <NUM>, or to open the second EGR valve <NUM>' to bleed off exhaust gas for recirculation to the inlet <NUM> of the internal combustion engine <NUM> via the EGR conduit <NUM>. The second EGR valve <NUM>' may suitably be of the same or similar type as the first EGR valve <NUM>, although having different valve types are conceivable.

Unlike the second EGR valve <NUM> in <FIG>, which is only provided for controlling exhaust gas from the second set of cylinders <NUM>, in <FIG> the second EGR valve <NUM>' is provided for controlling the exhaust gases from both the first set of cylinders <NUM> and the second set of cylinders <NUM>. In other words, the controller <NUM> may control the recirculation of exhaust gases from the first set of cylinders <NUM> by controlling the first EGR valve <NUM> and/or the second EGR valve <NUM>'.

It should be understood that although only an oxidation catalyst <NUM> has been shown in the figures, the EATS <NUM> in each figure may suitably include other components as well, such as those disclosed elsewhere in this application. For example, the EATS <NUM> may include a particulate filter catching soot and ashes, and a reduction catalysts reducing nitrogen oxides to nitrogen, such as with the help of a reductant fluid. Furthermore, the internal combustion engine system <NUM>‴ in <FIG> may in at least some exemplary embodiments comprise an exhaust throttle, such as shown in <FIG>.

It should be understood that each one of the discussed and illustrated exemplary embodiments may be provided with an EGR cooler, although not explicitly shown in all the figures. In <FIG>, however, an EGR cooler <NUM> is explicitly illustrated. In the illustrated exemplary embodiment, the exhaust gas which passes through the second EGR valve <NUM>' reaches the EGR conduit <NUM> upstream of the EGR cooler <NUM>. Exhaust gas which passes through the first EGR valve <NUM> is, however, in this exemplary embodiment illustrated as reaching the EGR conduit <NUM> downstream of the EGR cooler <NUM>. Thus, an EGR cooler bypass is configured via the first EGR valve <NUM>, whereby it is possible to control the amount of recirculated gases that should not be cooled. The non-cooled gas provides hotter inlet gas to the cylinders, which in turn results in hotter exhaust gas at cold start.

The controller <NUM> may suitably control each EGR valve <NUM>, <NUM>' individually. For instance, when hotter gases are not needed, the controller may close the first EGR valve <NUM>, and let the exhaust gases from the first and second sets of cylinders <NUM>, <NUM> be recirculated via the second EGR valve <NUM>'. When late post injection is to be performed, then the controller <NUM> closes the second EGR valve <NUM>', and may optionally open the first EGR valve <NUM> depending on the current circumstances.

It should be noted that in other exemplary embodiments the exhaust gas which passes the first EGR valve <NUM> may instead be arranged to reach the EGR conduit <NUM> upstream of the EGR cooler <NUM>.

Claim 1:
An internal combustion engine system (<NUM>, <NUM>', <NUM>", <NUM>‴), comprising
- an internal combustion engine (<NUM>) comprising a first set of one or more cylinders (<NUM>) and a second set of one or more cylinders (<NUM>) which is separate from the first set,
- an exhaust gas recirculation (EGR) conduit (<NUM>) for recirculating exhaust gas from the first and second sets of cylinders (<NUM>, <NUM>) to an inlet (<NUM>) of the internal combustion engine (<NUM>),
- a first EGR valve (<NUM>) for controlling flow of exhaust gas from the first set of cylinders (<NUM>) to the EGR conduit (<NUM>), and
- a fuel injector (<NUM>) for injection of fuel into at least one cylinder of the second set of cylinders (<NUM>),
characterized in that the system further comprises
- a second EGR valve (<NUM>, <NUM>') for controlling flow of exhaust gas from the second set of cylinders (<NUM>) to the EGR conduit (<NUM>),
- a controller (<NUM>) configured to control the closing of the second EGR valve (<NUM>, <NUM>') , thereby preventing flow of exhaust gas from the second set of cylinders (<NUM>) to the EGR conduit (<NUM>), and configured to activate the fuel injector (<NUM>) for late post injection of fuel into at least one cylinder of the second set of cylinders (<NUM>) when the second EGR valve (<NUM>, <NUM>') is closed, so that at least a part of the fuel that exits the second set of cylinders (<NUM>) is uncombusted,
- a turbine (<NUM>) arranged to receive and be driven by exhaust gas which is not recirculated in the EGR conduit (<NUM>), and
- an exhaust gas aftertreatment system (<NUM>) arranged to receive and treat exhaust gas which is not recirculated in the EGR conduit (<NUM>), the exhaust gas aftertreatment system (<NUM>) comprising an oxidation catalyst (<NUM>) for combustion of the late post injected fuel or derivates thereof,
wherein, for the exhaust gas flowing from the second set of cylinders (<NUM>), the second EGR valve (<NUM>, <NUM>') is located upstream of the turbine (<NUM>),
wherein the second EGR valve (<NUM>') is additionally configured to control flow of exhaust gas from the first set of cylinders (<NUM>) to the EGR conduit (<NUM>),
wherein the system further comprises an EGR cooler (<NUM>) provided in the EGR conduit (<NUM>), wherein the first EGR valve (<NUM>) is fluidly connected to the EGR conduit (<NUM>) downstream of the EGR cooler (<NUM>).