Patent Application
20130125542
The present invention relates to an exhaust heating apparatus that increases a temperature of exhaust in order to activate an exhaust emission purifier and keep the exhaust emission purifier in an activated state in an internal combustion engine that is provided with the exhaust emission purifier.
A turbocharger that comparatively easily achieves an improvement in output from an internal combustion engine also has a tendency at the same time to bring about a drop in fuel efficiency. In recent years, in order to meet the strong demand for an improvement in the fuel efficiency of internal combustion engines in which this kind of turbocharger is incorporated, internal combustion engines in which two turbochargers having different characteristics are incorporated are proposed in Patent Literature 1 and Patent Literature 2. In either case, there are provided a first turbocharger that mainly functions in a low rotational speed range of the internal combustion engine, and a second turbocharger that mainly functions in rotational speed ranges other than that; and these turbochargers are arranged in series or parallel in the intake and exhaust passages.
Meanwhile, coping with strict emission standards set on internal combustion engines has lead to a necessity for facilitating the activation of an exhaust gas purifying device at the start of its internal combustion engine, maintaining its active state during the operation of the internal combustion engine, and so on. In this respect, Patent Literature 1 and the like have proposed internal combustion engines in which an exhaust gas heating device is installed upstream of an exhaust gas purifying device in an exhaust passage. This exhaust gas heating device generates heating gas within exhaust gas and supplies this generated heating gas into the exhaust gas purifying device given at the downstream side to thereby facilitate the activation of the exhaust gas purifying device and maintain its active state. To do so, the exhaust gas heating device generally includes a fuel supply valve which adds fuel into the exhaust passage, and an igniter such as a glow plug which heats and ignites the fuel to generate heating gas. Furthermore, there is also known an exhaust heating apparatus in which a compact oxidation catalyst is arranged in the exhaust passage further on the downstream side than the igniter in order to increase the temperature of the heated gas. This oxidation catalyst has a heat generation function of its own, and has a function for reforming fuel to a low-carbon component, however, has different structure than the oxidation catalyst that is used as part of the exhaust emission purifier.
[Patent literature 1] Japanese Patent Laid-Open No. 2008-255902
[Patent literature 2] Japanese Patent Laid-Open No. 2009-270470
[Patent literature 3] Japanese Patent Laid-Open No. 2006-112401
It is evident that in the future, an internal combustion engine that is able to achieve both good output characteristics and fuel efficiency and clean exhaust will be important technology, and from this aspect, it has been considered that an exhaust heating apparatus is further incorporated in an internal combustion engine in which two-stage exhaust turbochargers as described above is incorporated.
In an exhaust heating apparatus disclosed in Patent Literature 3, in the case of an operating state where an intake flow related to an internal combustion engine is large, a flow rate of exhaust that flows through an exhaust passage also relatively increases. Therefore, it is not possible for fuel that is supplied to the exhaust passage from a fuel supply valve of the exhaust heating apparatus to remain around the igniter, and even when ignited, the flame is blown out by the flow of the exhaust, so there is a possibility that fuel that has not been combusted will flow toward the exhaust emission purifier side.
On the other hand, in the internal combustion engine in which the 2-stage exhaust turbochargers are incorporated, there is basically a tendency for an exhaust flow to become large. Moreover, the exhaust passes through exhaust turbines of the two turbochargers, respectively, so a temperature of the exhaust greatly drops due to the release of the heat to the outside and a heat capacity of the exhaust turbines themselves. As a result, the troubles described above become even more prominent, and it may only be possible to actuate the exhaust heating apparatus when there is a small amount of exhaust flow, such as when a vehicle decelerates.
An object of the present invention is to provide an exhaust heating apparatus that is capable of stably and continuously igniting fuel in an internal combustion engine in which 2-stage exhaust turbochargers are incorporated.
A first aspect of the present invention is an exhaust heating apparatus for heating exhaust being led to an exhaust emission purifier from an internal combustion engine in which a first exhaust turbocharger and a second exhaust turbocharger are incorporated, the second turbocharger being mainly used in a lower rotational speed range of the engine than the first turbocharger, wherein the exhaust heating apparatus is arranged in a first exhaust passage that is located further upstream than a confluent portion of the first exhaust passage, which passes through an exhaust turbine of the first turbocharger and continues to the exhaust emission purifier, and a second exhaust passage, which goes around the exhaust turbine of the first turbocharger and passes through an exhaust turbine of the second turbocharger and continues to the exhaust emission purifier, and further downstream than the exhaust turbine of the first turbocharger.
In the present invention, the exhaust heating apparatus is operated in the case of an operating state where it is not necessary to lead exhaust gas to the first exhaust passage, for example, in the case where the internal combustion engine is in the low rotational speed range. The resulting heated gas is merged with the exhaust flowing in the second exhaust passage at a confluent portion of the first exhaust passage and second exhaust passage, and flows into the exhaust emission purifier.
In the exhaust heating apparatus for the internal combustion engine according to the present invention, the exhaust heating apparatus may include a fuel supply valve for supplying fuel to the first exhaust passage, and ignition means for igniting and burning fuel that was supplied from the fuel supply valve to the first exhaust passage. Also, an oxidation catalyst is advantageously arranged in the exhaust passage between the ignition means and the exhaust emission purifier.
The first exhaust passage and the second exhaust passage may be arranged in parallel between the engine and the exhaust emission purifier. In this case, a valve capable of adjusting a flow of exhaust that flows in the first exhaust passage may be arranged in the first exhaust passage further on the upstream side than the exhaust turbine of the first turbocharger. Furthermore, when fuel is supplied to the first exhaust passage from the fuel supply valve, an opening of the valve may be adjusted so that the flow of exhaust flowing in the first exhaust passage becomes less than a flow of exhaust that flows in the second exhaust passage.
Alternatively, the second exhaust passage may be a bypass that is arranged in parallel with respect to the first exhaust passage. In this case, a valve capable of adjusting a flow of exhaust that flows in the bypass may be arranged in the bypass. Also, when fuel is supplied to the first exhaust passage from the fuel supply valve, the opening of the valve may be adjusted so that the flow of exhaust that flows in the first exhaust passage becomes less than the flow of exhaust that flows in the bypass.
A second aspect of the present invention is a control method for the exhaust heating apparatus according to the first aspect of the present invention that the first exhaust passage and the second exhaust passage are arranged in parallel between the engine and the exhaust emission purifier and that a valve capable of adjusting a flow of exhaust that flows in the first exhaust passage is arranged in the first exhaust passage further on the upstream side than the exhaust turbine of the first turbocharger, or the exhaust heating apparatus according to the first aspect of the present invention that the second exhaust passage is a bypass that is arranged in parallel with respect to the first exhaust passage and that a valve capable of adjusting a flow of exhaust that flows in the bypass is arranged in the bypass, comprising the steps of detecting a rotational speed of the internal combustion engine, and flowing a predetermined amount of exhaust in the first exhaust passage and actuating the exhaust heating apparatus when the detected rotational speed of the engine is equal to or less than a predetermined rotational speed, or when in an operating state where the first exhaust passage can be closed.
In the present invention, when the internal combustion engine is in the low rotational speed range, or when it is in the operating state where the first exhaust passage could be closed, the exhaust heating apparatus is operated while a valve opening is adjusted to flow a predetermined flow of exhaust into the first exhaust passage. The resulting heated gas is merged with the exhaust flowing in the second exhaust passage at the confluent portion of the first exhaust passage and second exhaust passage, and flows into the exhaust emission purifier.
With the present invention, even in an internal combustion engine in which 2-stage exhaust turbochargers are incorporated, it is possible to stably actuate the exhaust heating apparatus not only at the time of decelerating but even at the time of accelerating or traveling at constant speed when the internal combustion engine is in the low rotational speed range. This is the same even when in the operating state where the first exhaust passage can be closed. The heated gas can be efficiently mixed with the exhaust gas flowing in the second exhaust passage at the confluent portion with the second exhaust passage.
When an oxidation catalyst is arranged in the exhaust passage between ignition means and the exhaust emission purifier, it is possible to further efficiently increase the temperature of the heated gas.
When a valve that is capable of adjusting a flow of exhaust that flows in the first exhaust passage is arranged in the first exhaust passage further on the upstream side than an exhaust turbine of a first exhaust turbine type turbocharger, as long as the internal combustion engine is in the low rotational speed range, it is possible to reliably actuate the exhaust heating apparatus. Particularly, when an opening of the valve is adjusted so that the flow of exhaust that flows in the first exhaust passage is less than a flow of exhaust that flows in the second exhaust passage, it is possible to more reliably generate stable heated gas.
Similarly, when a valve that is capable of adjusting a flow of exhaust that flows in a bypass is arranged in the bypass, as long as the internal combustion engine is in the low rotational speed range, it is possible to reliably actuate the exhaust heating apparatus. Particularly, when the opening of the valve is adjusted so that the flow of exhaust that flows in the first exhaust passage is less than the flow of exhaust that flows in the bypass, it is possible to more reliably generate stable heated gas. Moreover, it is possible to use existing components that are incorporated in the 2-stage exhaust turbochargers as a bypass and valve.
An embodiment in which the present invention is applied to a compression ignition type internal combustion engine in which parallel-type 2-stage exhaust turbochargers are incorporated will be explained in detail with reference to FIGS. 1 to 4. The present invention is not, however, limited to the embodiment, and the construction thereof may be freely modified corresponding to required characteristics. The present invention is effectively applied to a spark ignition type internal combustion engine in which gasoline, alcohol, LNG (Liquefied Natural Gas) or the like is used as fuel to be ignited by a spark plug, for example.
Main components of an engine system of the embodiment are illustrated schematically in
An intake pipe 17 that is connected to an engine 10 by way of an intake manifold 16, together with the intake manifold 16, defines an intake passage 18, and on the upstream side and downstream side of the intake pipe 17, has a branched portion 19d and a confluent portion 19c with respect to a branched intake pipe 19. In other words, both ends of the branched intake pipe 19 are connected to the intake pipe 17 by way of the branched portion 19d on the upstream side and the confluent portion 19c on the downstream side of the intake passage 18. That is to say, a portion of the intake pipe 17 that is located between the branched portion 19d on the upstream side and the confluent portion 19c on the downstream side of the intake passage 18, and the branched intake pipe 19 are arranged in parallel. In the embodiment, a portion that is defined by the branched intake pipe 19 is conveniently called a first intake passage 18f, and a portion that is defined by the intake pipe 17 that is located between the branched portion 19d on the upstream side and the confluent portion 19c on the downstream side of the intake passage 18 is called a second intake passage 18s.
An airflow meter 20 and an intake temperature sensor 21 are attached to the intake pipe 17 further on the upstream side than the branched portion 19d on the upstream side of the intake passage 18, and information related to the intake flow and intake temperature that were detected by these is outputted to the ECU 14. The ECU 14 performs correction of the amount of fuel injection from the fuel injection valve 11 based on the information detected from the airflow meter 20 and the intake temperature sensor 21.
An intercooler 22 that cools the intake in order to increase a filled density of the intake that flows through the intake passage 18, and a throttle valve 23 for adjusting an opening of the intake passage 18 are provided in the intake pipe 17 further on the downstream side than the confluent portion 19c on the downstream side of the intake passage 18. The throttle valve 23 in the embodiment is mechanically linked to the position of the accelerator pedal 13 that is adjusted by the amount that the driver presses the accelerator pedal 13, however, it is of course possible to employ a throttle valve that can electrically correct the opening according to the operating state of the vehicle.
An exhaust pipe 25 that is connected to the engine 10 by way of an exhaust manifold 24, together with the exhaust manifold 24, defines an exhaust passage 26, and has a branched portion 27d and confluent portion 27c related to a branched exhaust pipe 27 on the upstream side and downstream side. In other words, both ends of the branched exhaust pipe 27 are connected to the exhaust pipe 25 at the branched portion 27d on the upstream side and the confluent portion 27c on the downstream side of the exhaust passage 26. That is to say, a portion of the exhaust pipe 25 that is located between the branched portion 27d on the upstream side and the confluent portion 27c on the downstream side of the exhaust passage 26, and the branched exhaust pipe 27 are arranged in a parallel state. In the embodiment, a portion that is defined by the branched exhaust pipe 27 corresponds to a first exhaust passage 26f of the present invention. Moreover, a portion that is defined by the exhaust pipe 25 that is located between the branched portion 27d on the upstream side and the confluent portion 27c on the downstream side of the exhaust passage 26 corresponds to a second exhaust passage 26s in the present invention.
A first exhaust turbine type turbocharger (hereinafter, referred to as simply a turbocharger) 28 is arranged so as to span between the first intake passage 18f and first exhaust passage 26f, and the compressor 28a thereof being located in the first intake passage 18f, the exhaust turbine 28b is located in the first exhaust passage 26f. Moreover, a second turbocharger 29 that is mainly used in the low rpm range of the engine 10 more than the first turbocharger 28 is arranged so as to span between the second intake passage 18s and the second exhaust passage 26s. Together with a compressor 29a of the second turbocharger 29 being located in the second intake passage 18s, an exhaust turbine 29b thereof is located in the second exhaust passage 26s. Therefore, the second exhaust passage 26s that is branched off from the branched portion 27d on the upstream side goes around the exhaust turbine 28b of the first turbocharger 28, passes through the exhaust turbine 29b of the second turbocharger 29, and merges with the first exhaust passage 26f at the confluent portion 27c on the downstream side. An exhaust emission purifier 30 is connected to the exhaust pipe 25 that is located further downstream than the confluent portion 27c on the downstream side of the exhaust passage 26.
An intake on-off valve 31 for opening or closing the first intake passage 18f is arranged in the first intake passage 18f further on the downstream side than the compressor 28a of the first turbocharger 28. An on-off valve driving motor 32 is connected to the intake on-off valve 31, and the ECU 14 controls the actuation of the on-off valve driving motor 32 according to the operating state of the vehicle, and switches the opening and closing operation of the intake on-off valve 31. Basically, when the engine speed, or in other words, the number of revolutions Nn per unit time of the engine is equal to or greater than the number of revolutions NR (hereinafter, this will be referred to as fuel supply judgment speed) when the first turbocharger begins to exert a supercharging ability, the intake on-off valve 31 becomes completely open. On the other hand, when less than the fuel supply judgment speed NR, the intake on-off valve 31 is controlled so as to become completely closed. In order for this, a crank angle phase of the engine 10 is detected by a crank angle sensor 33, and that detection information is outputted to the ECU 14, after which the ECU 14 calculates the engine speed Nn based on the information from this crank angle sensor 33.
A flow regulating valve 34 that can adjust the flow of exhaust that flows in the first exhaust passage 26f is arranged in the first exhaust passage 26f further on the upstream side than the exhaust turbine 28b of the first turbocharger 28. Moreover, a valve position sensor 35 for detecting the opening is connected to the flow regulating valve 34, and the detection information is outputted to the ECU 14. An regulating valve driving motor 36, whose actuation is controlled by the ECU 14, is also connected to the flow regulating valve 34, and the valve opening is adjusted based on the operating state of the vehicle and the detection information from the valve position sensor 35. When fuel from a fuel supply valve 38 of an exhaust heating apparatus 37 that will be described later is supplied to the first exhaust passage 26f, the flow regulating valve 34 is controlled so that the amount of exhaust flowing in the first exhaust passage 26f becomes less than the amount of exhaust flowing in the second exhaust passage 26s. More specifically, the ECU 14, by way of the regulating valve driving motor 36, sets the opening of the flow regulating valve 34 so that exhaust flows in the first exhaust passage 26 at just a flow rate that the flame that is caused to occur inside the first exhaust passage 26f by the exhaust heating apparatus 37 does not go out. As a result, it is possible for a predetermined flow of exhaust by which the flame does not go out to flow in the first exhaust passage 26f, and it is possible to lead the heating gas that is obtained by the exhaust heating apparatus 37 to the exhaust emission purifier 30.
The characteristics of the first and second turbochargers 28, 29 in the embodiment are illustrated in
The exhaust heating apparatus 37 is arranged in the first exhaust passage 26f located further upstream than the confluent portion 27c of the first exhaust passage 26f and second exhaust passage 26s, and further downstream than the exhaust turbine 28b of the first turbocharger 28. This exhaust heating apparatus 37 is an apparatus for generating heated gas and supplying that heated gas to the exhaust emission purifier 30 located on the downstream side, and for activating and maintaining the activated state of that exhaust emission purifier 30. The exhaust heating apparatus 37 in the embodiment is provided in order from the upstream side with the fuel supply valve 38, and a glow plug 39 that is used for ignition means in the present invention. In the embodiment, the first exhaust passage 26f and an auxiliary oxidation catalyst 40 are provided in that order from the upstream side between the glow plug 39 and confluent portion 27c.
The fuel supply valve 38 is for supplying fuel into the first exhaust passage 26f, and the ECU 14 controls a supply timing and a supply amount based on the whether or not the exhaust emission purifier 30 is in the activated state and on the operating state of the vehicle.
The glow plug 39 is for igniting the fuel that is supplied from the fuel supply valve 38 into the first exhaust passage 26f. A direct-current power supply and a booster circuit (not illustrated in the figure) are connected to the glow plug 39 in order to supply power thereto, and a surface temperature of the glow plug 39 is controlled by the ECU 14. Instead of a glow plug 39, it is also possible to use a ceramic heater or the like as a method of ignition of the present invention.
The operation of supplying fuel from the fuel supply valve 38 into the first exhaust passage 26f, and heating of the glow plug 39 are basically only performed when the engine speed Nn are equal to or less than the fuel supply judgment speed NR, and when the exhaust emission purifier 30 is in the non-activated state. However, as long as the operating state is such that it is not necessary to lead exhaust to the first exhaust passage 26f, or in other words, when it is not necessary to make the first turbocharger 28 to function, it is possible to actuate the exhaust heating apparatus 37 with no problem. Moreover, when the exhaust emission purifier 30 and the auxiliary oxidation catalyst 40 are activated, it is possible to actuate the exhaust heating apparatus 37 as necessary even when the engine speed Nn are equal to or greater than the fuel supply judgment speed NR, or even when the operating state is such that exhaust is led to the first exhaust passage 26f and the first turbocharger 28 is made to function.
The auxiliary oxidation catalyst is arranged in the exhaust passage 26 between the glow plug 39 and the exhaust emission purifier 30. In the embodiment, this auxiliary oxidation catalyst 40 is arranged in the exhaust passage 26f further on the upstream side than the confluent portion 27c, however, it also could be arranged in the exhaust passage 26 further on the downstream side than the confluent portion 27c. The auxiliary oxidation catalyst 40 has a cross-sectional area that is less than a cross-sectional area of the first exhaust passage 26f, so part of the exhaust can pass without passing through the auxiliary oxidation catalyst 40. In other words, a flow rate of the exhaust that passes through the auxiliary oxidation catalyst 40 is lower than a flow rate of the exhaust that does not pass through it, so it is possible to further raise a temperature of the exhaust that passes through the auxiliary oxidation catalyst 40. When a temperature of the auxiliary oxidation catalyst 40 is sufficiently high, or in other words, in the activated state, power to the glow plug 39 is cut, so it is also possible to directly burn the fuel-air mixture inside the auxiliary oxidation catalyst 40. However, when the auxiliary oxidation catalyst 40 is not activated, such as at the time of the cold start of the engine 10, it is necessary to supply power to the glow plug 39. When the temperature of the auxiliary oxidation catalyst 40 becomes high, hydrocarbons having a large carbon number in the unburned mixture are broken down and reformed into hydrocarbons having a small carbon number and high reactivity. That is to say, the auxiliary oxidation catalyst 40 on one hand functions itself as a rapid heating element that heats at high speed, and on the other hand, also functions as a fuel reforming catalyst that generates reformed fuel.
In this way, heated gas is generated in the first exhaust passage 26f, and the high-temperature exhaust is then passed through the auxiliary oxidation catalyst 40 and the temperature is further raised, and the unburned gas is either burned by the auxiliary oxidation catalyst 40, or is reformed to highly active hydrocarbon. Then, at the confluent portion 27c, these are mixed with the exhaust that is flowing in the second exhaust passage 26s and supplied to the exhaust emission purifier 30. As a result, it is possible to quickly activate and maintain the activated state of the exhaust emission purifier 30. Particularly, this exhaust heating apparatus 37 is extremely useful for improving the so-called cold emission state immediately after the cold start of the engine 10.
In order to increase the ignitability of the fuel that is injected from the fuel supply valve 38 into the first exhaust passage 26f, providing a plate shaped vaporization promotion member that faces the fuel supply valve 38 and glow plug 39 is effective. This vaporization promotion member has a function of scattering and atomizing fuel, or in other words promoting vaporization of fuel by colliding with fuel that is injected from the fuel supply valve 38.
The exhaust emission purifier 30 is for detoxifying the toxic material that is generated by burning the fuel-air mixture inside the combustion chamber 12. The exhaust emission purifier 30 in the embodiment is provided in order from the upstream side of the exhaust passage 26 with an oxidation catalyst 41, a three-way catalyst and a NOx catalyst, however, for convenience, only the oxidation catalyst 41 that is arranged on the most upstream end side is illustrated. In this oxidation catalyst 41, incorporated is a catalyst temperature sensor 42 that detects a burner temperature and outputs that to the ECU 14.
The ECU 14 controls the flow regulating valve 34 and the exhaust heating apparatus 37, or in other words, controls the actuation of the fuel supply valve 38 and glow plug 39 according to a preset program and based on the operating state of the vehicle and a detection signal from the catalyst temperature sensor 42. In the embodiment, when, based on the detection signal from the catalyst temperature sensor 42, a catalyst element temperature Tn is equal to or less than a TR as an activation index, it is determined that the exhaust emission purifier is not activated. When the engine speed Nn are less than the fuel supply judgment speed NR at which the first turbocharger 28 does not exert supercharging ability, the flow regulating valve 34 is maintained in a state of being open a little, and part of the exhaust is also led to the first exhaust passage 26f. Electric power is then supplied to the glow plug 39 and fuel is supplied from the fuel supply valve 38, and the temperature of the exhaust that passes the exhaust turbine 28b of the first turbocharger 28 is raised. However, when the catalyst element temperature Tn exceeds the activation judgment temperature TR, it is determined that the exhaust emission purifier 30 is activated, so the supply of fuel from the fuel supply valve 38 is stopped, and the power to the glow plug 39 is cut. Moreover, when the engine speed Nn are equal to or greater than the fuel supply judgment speed NR, at which the first turbocharger 28 exerts a supercharging ability, the intake on-off valve 31 and the flow regulating valve 34 are maintained in the completely open state to allow the first turbocharger 28 to exert a supercharging effect. In this case, even when fuel is supplied from the fuel supply valve 38 into the first exhaust passage 26f and ignited by the glow plug 39, the flow rate of the exhaust that is flowing in the first exhaust passage 26f is high, so there is a high possibility that the flame will go out. Therefore, in this case, the exhaust heating apparatus 37 is not allowed to be actuated.
Such a control procedure of the exhaust heating apparatus 37 is illustrated in a flow chart in
Next, in step S18, it is determined whether or not the temperature Tn of the oxidation catalyst 41 is greater than the activation judgment reference temperature TR. Here, when it is determined that the temperature Tn of the oxidation catalyst 41 is greater than the activation judgment reference temperature TR, or in other words, when it is determined that the oxidation catalyst is activated, processing moves to step S19 and together with stopping the supply of fuel from the fuel supply valve 38, stops opening control of the flow adjustment value 34. Then, depending on the engine speed Nn, the flow regulating valve 34 is switched to the completely closed state or completely open state. Furthermore, after the power to the glow plug 39 is stopped, processing moves to step S20, resets the flag, and ends this series of control.
In step S18, when it is determined that the temperature Tn of the oxidation catalyst 41 is equal to or less than the activation judgment reference temperature TR, or in other words, when it is determined that the oxidation catalyst 41 is not yet activated, processing returns to step S12. Then it is determined whether or not the engine speed Nn are equal to or less than fuel supply judgment speed NR, and only when the engine speed Nn are equal to or less than the fuel supply judgment speed NR, fuel is continuously supplied to the first exhaust passage 26f, and the oxidation catalyst 41 is activated. In step S13, the flat is set, or in other words, when it is determined that this is the second time or later that fuel is supplied from the fuel supply valve 38, processing moves to step S17 and the supply of fuel continues.
In step S12, when the number of engine speed exceeds the fuel supply judgment speed NR, or in other words, when the first turbocharger 28 is determined to be in a supercharging state, processing moves to step S21 and determines whether or not the flag is set. Here, the flag is set, or in other words, when it is determined that this is the second time or later that fuel has been supplied from the fuel supply valve 38, processing moves to step S19 and stops the supply of fuel from the fuel supply valve 38. Furthermore, opening control of the flow adjustment value 34 is stopped, and the flow regulating valve 34 is switched to the completely open state. When the engine speed Nn exceed the fuel supply judgment speed NR, the intake opening and closing value 31 is also switched to the completely open state.
In step S21, when it is determined that the flag is not set, or in other words, when it is determined that fuel is not being supplied from the fuel supply valve 38, the control flow ends without doing anything. Moreover, in step S11, the same occurs when the temperature Tn of the oxidation catalyst 41 exceeds the activation judgment reference temperature TR, or in other words, when it is determined that the oxidation catalyst 41 is activated.
In the embodiment described above, when the engine speed Nn are equal to or less than the fuel supply judgment speed NR, fuel is supplied to the first exhaust passage 26f. However, in the case of the operating state where the flow regulating valve 34 is closed so that exhaust cannot flow through the first exhaust passage 26f, it is also possible to perform control so that fuel is supplied to the first exhaust passage 26f. In this case, preferably, the flow regulating valve 34 is open a little and exhaust is led to the first exhaust passage 26f.
The present invention can also be applied to an engine system wherein the first and second turbochargers 28, 29 described above are arranged in series with respect to the exhaust passage 26. Another embodiment of the present invention is schematically illustrated in
In the middle of the intake bypass pipe 43, an intake bypass valve 44 for opening and closing the intake bypass pipe 43 is attached, and that opening and closing operation is controlled by the ECU 14 by way of an intake bypass driving motor (not illustrated in the figure) according to the operating state of the vehicle.
The exhaust pipe 25 that defines the intake passage 18 has a branched portion 45d and a confluent portion 45c related to a first exhaust bypass pipe 45 on the upstream side and the downstream side of the exhaust pipe 25. In other words, both ends of the first exhaust bypass pipe 45 are connected to the exhaust pipe 25 by the branched portion 45d on the upstream side and the confluent portion 45c on the downstream side of the exhaust passage 26. That is to say, a portion of the exhaust pipe 25 that is located between the branched portion 45d on the upstream side and the confluent portion 45c on the downstream side of the exhaust passage 26, and the first exhaust bypass pipe 45 are arranged in a parallel state. The exhaust emission purifier 30 is connected to the exhaust pipe 25 that is located further on the downstream side than the first exhaust bypass pipe 45. The exhaust pipe 25 that is located even further on the upstream side than the first exhaust bypass pipe 45 further has a branched portion 46d and a confluent portion 46c related to a second exhaust bypass pipe 46 on the upstream side and the downstream side of the exhaust pipe 25. In other words, both ends of the second exhaust bypass pipe 46 are connected to the exhaust pipe 25 at the branched portion 46d on the upstream side and the confluent portion 46c on the downstream side of the exhaust passage 26. That is to say, a portion of the exhaust pipe 25 that is located between the branched portion 46d on the upstream side and the confluent portion 46c on the downstream side of the exhaust passage 26, and the second exhaust bypass pipe 46 are arranged in a parallel state. In the embodiment, a portion that is defined by the exhaust pipe 25 that is located between the branched portion 45d on the upstream side and the confluent portion 45c on the downstream side related to the first exhaust bypass pipe 45 corresponds to the first exhaust passage 26f in the present invention. Moreover, a portion of the exhaust pipe 25 from the branched portion 46d related to the second exhaust bypass pipe 46 to the branched portion 45d related to the first exhaust bypass pipe 45 corresponds to the second exhaust passage 26s in the present invention.
The first turbocharger 28 is arranged so as to span between the first intake passage 18f and the first exhaust passage 26f, together with the compressor 28a thereof being located in the first intake passage 18f and the exhaust turbine 28b being located in the first exhaust passage 26f. Moreover, the second turbocharger 29 that is mainly used in a lower rotational speed range of the engine 10 than the first turbocharger 28 is arranged so as to span between the second intake passage 18s and the second exhaust passage 26s. The compressor 29a of this second turbocharger 29 is located in the second intake passage 18s, and the exhaust turbine 29b thereof is located in the second exhaust passage 26s between the branched portion 46d and the confluent portion 46c related to the second bypass pipe 46. Therefore, the exhaust passage 26s that passes through the exhaust turbine 29b of the second turbocharger 29 goes around the exhaust turbine 28b of the first turbocharger 28 by way of the first exhaust bypass pipe 45, and merges with the first exhaust passage 26f at the confluent portion 45c on the downstream side.
The exhaust heating apparatus 37 is incorporated in the second exhaust passage 26s further on the downstream side than the exhaust turbine 28b of the first turbocharger 28 and further on the upstream side than the confluent portion 45c that merges with the first exhaust bypass pipe 45. Moreover, the exhaust emission purifier 30 is arranged in the exhaust passage 26 further on the downstream side than the confluent portion 45c that merges with the first exhaust bypass pipe 45.
A first exhaust bypass valve 47 and a second exhaust bypass valve 48 are incorporated in the first exhaust bypass pipe 45 and the second exhaust bypass pipe 46, and make it possible to open and close these pipes. The opening and closing operation of these valves is controlled by the ECU 14 by way of a first exhaust bypass valve driving motor and a second exhaust bypass valve driving motor (not illustrated in the figure). In the embodiment, an opening of the first exhaust bypass valve 47 can be controlled so that part of the exhaust flows inside the second exhaust passage 26s, and in order for this, a valve position sensor 35 is attached to the first exhaust bypass valve 47. In other words, the first exhaust bypass valve 47 corresponds to the flow regulating valve 34 in the previous embodiment.
Therefore, when fuel is supplied from the fuel supply valve 38 to the first exhaust passage 26f, the opening of the first exhaust bypass valve 47 is controlled so that the flow of exhaust that flows through the first exhaust passage 26f is less than the flow of exhaust that flows through the second exhaust passage 26s. More specifically, the opening of the first exhaust bypass valve 47 is controlled by the ECU 14 by way of the first exhaust bypass valve driving motor so that exhaust flows through the first exhaust passage 26f at just enough of a flow rate so that the flame that is caused to occur in the first exhaust passage 26f by the exhaust heating apparatus 37 does not go out.
The characteristics of the first and second turbochargers 28, 29 of the embodiment are illustrated in
When it is necessary to supply fuel from the fuel supply valve 38 into the first exhaust passage 26f, the first exhaust bypass valve 47 is closed a little from the completely open state, and part of the exhaust is led to the first exhaust passage 26f. However, this operation is executed only when the first exhaust bypass valve 47 in the range where the engine speed Nn are equal to or less than the fuel supply judgment speed NR is in the completely open state. As a result, fuel that is injected into the first exhaust passage 26f from the fuel supply valve 38 is ignited by the glow plug 39, and without the flame going out, becomes heated gas and at the confluent portion 45c that merges with the first exhaust bypass pipe 45, is mixed with the exhaust that flows from the second exhaust passage 26s. This promotes activation of the exhaust emission purifier 30.
As described above, when there is no problem even though the fuel injected from the fuel supply valve 38 may go out inside the first exhaust passage 26f, care must be taken in that the exhaust heating apparatus 37 can be actuated in an arbitrary operating state.
It is to be noted that the present invention shall be construed solely from the matters described in the claims thereof, and the foregoing embodiment includes not only the matters described above but any changes and corrections encompassed by the concept of the present invention. In other words, all the matters in the foregoing embodiment are not to limit the present invention, but include any configurations which may not be directly related to the present invention and can be changed optionally depending upon the application, purpose, and the like.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/002791 | 4/16/2010 | WO | 00 | 2/4/2013 |
