JP2011149402A - Auxiliary system for starting vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to improve an output power at the start of a vehicle as well as performing a recovery operation of an exhaust gas control system, on the premise that a turbocharger and an exhaust gas control system of which mountings hereafter become essential for a vehicle has been mounted on an engine. <P>SOLUTION: There is provided an auxiliary system for starting a vehicle in which a turbocharger 15 is mounted on an engine 10 and besides an exhaust gas control system 16 needed to be subjected to a recovery operation is arranged on the more downstream side of an exhaust gas flow than the turbocharger 15 in the exhaust passage 11 of the engine 10. In the auxiliary system for starting a vehicle, a preceding-stage oxidation catalyst 27, required to react added fuel and thereby increase an exhaust gas temperature in performing the recovery operation of the exhaust gas control system 16, is arranged on the more upstream side of the exhaust gas flow than the turbocharger 15 of the exhaust passage 11. Then, by supplying the added fuel to the preceding-stage oxidation catalyst 27 at the start of the vehicle to perform the recovery operation of the exhaust gas control system 16, the added fuel is reacted with the preceding-stage oxidation catalyst 27, increasing the exhaust gas temperature introduced into the turbocharger 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle start assist system in which a turbocharger and an exhaust gas purification device are mounted on an engine.

  In order to improve fuel efficiency, a turbocharger called a turbocharger has been added to diesel engines. In addition, downsizing, which is called downsizing, is also progressing. One of the harmful effects associated with the addition of these supercharging devices and the reduction in displacement is the lack of output when the vehicle starts. In order to improve the output shortage at the start of the vehicle, start assistance by an electric motor by hybridization, improvement of output at the start of the vehicle by improvement of a turbocharger, and the like are performed.

  In addition, in diesel engines, addition of exhaust gas purification devices that purify nitrogen oxides (NOx) and particulate matter (PM) in exhaust gas is also progressing (see Patent Document 1). This exhaust gas purification device requires a regenerating operation in order to maintain its role and function.

JP 2008-101535 A

  For the start assistance by the electric motor, which is performed as assistance when starting the vehicle, it is essential that the vehicle is a hybrid vehicle. In addition, since the production process of the hybrid vehicle itself is complicated, it seems that the hybrid vehicle is expensive, has low production efficiency, and cannot be mainstream.

  The output improvement at the start of the vehicle by improving the turbocharger can have a certain effect. However, since it is a transient condition from the idling state where the turbocharger is not good at the time of starting the vehicle, there is a limit to improving the output at the time of starting the vehicle by improving the turbocharger, which may cause exhaust gas deterioration. .

  Therefore, an object of the present invention is to perform regeneration operation of the exhaust gas purification device and output at the time of starting the vehicle on the assumption that the turbocharger and exhaust gas purification device that will be required to be mounted on the vehicle in the future are mounted on the engine. It is to enable improvement.

  In order to achieve the above object, the present invention provides a vehicle in which a turbocharger is mounted on an engine, and an exhaust gas purifying device that requires regeneration operation is disposed downstream of the turbocharger in the exhaust passage of the engine. A starter oxidation catalyst required for reacting additional fuel to raise the temperature of the exhaust gas when the regeneration operation of the exhaust gas purification device is performed. The additional fuel is disposed on the upstream side of the vehicle, and when the vehicle starts, the additional fuel is supplied to the front-stage oxidation catalyst and the exhaust gas purification device is regenerated. The temperature of the exhaust gas introduced into the charger is increased.

  The exhaust gas purification device may include a NOx purification device for purifying nitrogen oxides in the exhaust gas and a PM purification device for purifying particulate matter in the exhaust gas.

  The supply of additional fuel to the pre-stage oxidation catalyst may be performed by injecting fuel from a fuel injection nozzle that injects fuel into the combustion chamber of the engine.

  An exhaust pipe fuel injection injector may be provided in the exhaust passage, and supply of additional fuel to the pre-stage oxidation catalyst may be performed by injecting fuel from the exhaust pipe fuel injection injector.

  According to the present invention, on the assumption that a turbocharger and an exhaust gas purification device that will be required to be mounted on a vehicle in the future are mounted on the engine, the regeneration operation of the exhaust gas purification device is performed, and the output at the start of the vehicle is improved. There is an excellent effect of making it possible.

FIG. 1 is a schematic view of a starting assistance system according to an embodiment of the present invention. FIG. 2 is a schematic view of a starting assistance system according to another embodiment. FIG. 3 is a schematic view of a starting assistance system according to another embodiment. FIG. 4A is a graph showing a change in torque at the start of the vehicle, FIG. 4B is a graph showing a change in smoke emission amount at the start of the vehicle, and FIG. 4C is a turbocharger at the start of the vehicle. It is a graph which shows a rotational speed change.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, in the start assist system according to the present embodiment, a turbine 12 disposed in an exhaust passage 11 of an engine (for example, a diesel engine) 10 and a compressor 14 disposed in an intake passage 13 of the engine 10. The exhaust gas purification device 16 that needs to be regenerated is disposed downstream of the turbocharger 15 (turbine 12) in the exhaust passage 11 from the exhaust gas flow. Further, the exhaust passage 11 and the intake passage 13 communicate with each other through an EGR passage 17 in order to introduce a part of the exhaust gas in the exhaust passage 11 into the intake passage 13 as EGR gas, and an EGR valve 18 is connected to the EGR passage 17. And an EGR cooler (not shown).

  In the present embodiment, the exhaust passage 11 includes an exhaust manifold 19 attached to the engine 10 and an exhaust pipe 20 connected to the exhaust manifold 19. The turbine 12 and the exhaust gas purification device 16 are connected to the exhaust pipe 20. It is arranged. The intake passage 13 includes an intake manifold 21 attached to the engine 10 and an intake pipe 22 connected to the intake manifold 21, and the compressor 14 is disposed in the intake pipe 22. The EGR passage 17 includes an EGR pipe 23 having one end connected to the exhaust manifold 19 and the other end connected to the intake pipe 22.

  The exhaust gas purification device 16 is a NOx purification catalyst that purifies nitrogen oxides (NOx) in the exhaust gas (for example, a NOx storage catalyst such as LNT, NAC, NSC, etc., selective NOx that adds urea or hydrocarbons to reduce NOx. A NOx purification device 24 having a reduction catalyst (SCR) and the like, and a PM purification device 25 having a PM filter (for example, DPF, DPD, C-DPF, CRT, etc.) for purifying particulate matter (PM) in the exhaust gas. It is configured with. In the present embodiment, the NOx purification catalyst is SCR, and the PM filter is DPF.

  In the present embodiment, the PM purification device 25 and the NOx purification device 24 are arranged in the exhaust pipe 20 in order from the upstream side of the exhaust gas flow, but on the contrary, the NOx purification device in order from the upstream side of the exhaust gas flow. 24 and the PM purification device 25 may be disposed in the exhaust pipe 20.

In the present embodiment, a urea injector 26 that injects urea into the exhaust passage 11 is disposed upstream of the NOx purification device 24 (SCR) in the exhaust passage 11 of the engine 10. The urea injection injector 26 is attached to the exhaust pipe 20 between the turbocharger 15 (turbine 12) and the PM purification device 25. In the present embodiment, when the exhaust temperature at the inlet of the NOx purification device 24 (SCR) detected by an exhaust temperature sensor (not shown) reaches the activation temperature of the SCR, it corresponds to the amount of nitrogen oxides in the exhaust gas. An amount of urea is injected from the urea injector 26. The urea injected into the exhaust pipe 20 is hydrolyzed to ammonia (NH ₃ ), and this ammonia is reacted with nitrogen oxides by the NOx purification device 24 (SCR) to reduce the nitrogen oxides. Yes.

  Further, in the present embodiment, when the regeneration operation of the exhaust gas purification device 16 is performed, the pre-stage oxidation catalyst 27 necessary for reacting the additional fuel to raise the temperature of the exhaust gas is provided before and after the exhaust manifold 19 and the inlet of the turbine 12. As before, it is disposed on the exhaust gas flow upstream side of the turbocharger 15 (turbine 12) of the exhaust passage 11 of the engine 10, and on the exhaust gas flow downstream side of the exhaust gas purification device 16 of the exhaust passage 11 of the engine 10. A post-stage oxidation catalyst 28 is provided. The front-stage oxidation catalyst 27 is composed of a first oxidation catalyst 29 mounted for each cylinder at the inlet of the exhaust manifold 19 and a second dioxide catalyst 30 mounted on the exhaust pipe 20 before the inlet of the turbine 12. In this embodiment, the post-stage oxidation catalyst 28 decomposes excess ammonia and is attached to the exhaust pipe 20.

  An EGR valve 18, a urea injector 26, a fuel injection nozzle 31 for injecting fuel into the combustion chamber of the engine 10, and the like are electrically connected to an ECU (engine control unit or electronic control unit) 32 as control means. Thus, the EGR valve 18, the urea injector 26, the fuel injection nozzle 31 and the like are controlled.

  In this embodiment, the regeneration operation of the exhaust gas purification device 16 is performed when starting acceleration in which the accelerator opening and the vehicle speed are increased from when the vehicle is idling (that is, when starting the vehicle). When the regeneration operation of the exhaust gas purification device 16 is performed, the additional fuel is supplied to the pre-stage oxidation catalyst 27 under the condition that the exhaust gas does not deteriorate. In general, the supply of additional fuel to the pre-stage oxidation catalyst 27 is referred to as post-injection, where the engine cycle starts from the combustion stroke to the exhaust stroke, or fuel is injected from the fuel injection nozzle 31 or to the exhaust manifold 19. A method of injecting fuel from the provided exhaust pipe fuel injection injector 33 (see FIG. 2) is employed. In the present embodiment, the supply of additional fuel to the pre-stage oxidation catalyst 27 employs a method of injecting fuel (post injection) from the fuel injection nozzle 31.

  The additional fuel by the regeneration operation of the exhaust gas purification device 16 at the time of starting of the vehicle reacts with the pre-stage oxidation catalyst 27 (first oxidation catalyst 29, second dioxide catalyst 30) to raise the temperature of the exhaust gas. The exhaust gas that has become hot and expanded is introduced into the turbocharger 15 (the turbine 12), and the turbocharger 15 is rapidly increased in rotation speed to quickly increase the supercharging pressure. By increasing the supercharging pressure by increasing the rotational speed of the turbocharger 15, the output at the start of the vehicle quickly increases. Further, since the amount of air supplied to the engine 10 increases, the output itself can be increased. Therefore, it is possible to improve the turbo efficiency without improving the turbocharger 15 even under the condition that the turbocharger 15 is not good at the time of starting the vehicle.

  The change in the exhaust gas properties due to the additional fuel can also be performed by regeneration of the exhaust gas purification device 16 (combustion of particulate matter collected by the PM filter of the PM purification device 25). The frequency of forced regeneration of the purification device 16 can be reduced. That is, the exhaust gas purification device 16 is often regenerated without the driver's intention, and the user burden for maintaining the purification rate of the exhaust gas purification device 16 is reduced.

  Next, the superiority of the starting assistance system according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 4, in the present embodiment, the accelerator opening is assumed to be 0% to a predetermined opening (for example, 60%) between time t1 and time t2 (for example, 2 seconds) assuming start acceleration. After opening, the accelerator opening is made constant at the predetermined opening (60%) after time t2. On the other hand, when the regeneration operation of the exhaust gas purification device 16 is performed at the start of the vehicle, the regeneration operation of the exhaust gas purification device 16 is started at time t1 when the accelerator is turned on, and the regeneration operation is terminated at time t3.

  Further, in the present embodiment, the EGR valve 18 is controlled so that the EGR rate or the EGR amount becomes low during the regeneration operation of the exhaust gas purification device 16 (that is, from the time t1 to the time t3).

  Compared to the case where the regeneration operation of the exhaust gas purification device 16 is performed when the vehicle starts (when the regeneration operation is performed) and the case where the regeneration operation of the exhaust gas purification device 16 is not performed when the vehicle starts (the case where there is no regeneration operation). As shown in FIG. 4 (c), the rotational speed of the turbocharger 15 increases rapidly and the amount of air supplied to the engine 10 also increases, so that the effect of increasing torque is obtained as shown in FIG. 4 (a). As shown in FIG. 4B, the effect of reducing smoke is also obtained.

  In short, according to the start assist system according to the present embodiment, the pre-stage oxidation catalyst 27 necessary for reacting the additional fuel and raising the temperature of the exhaust gas when the regeneration operation of the exhaust gas purification device 16 is performed is performed on the engine 10. The exhaust passage 11 is disposed on the upstream side of the exhaust gas flow with respect to the turbocharger 15, and when the vehicle starts, the additional fuel is supplied to the pre-stage oxidation catalyst 27 to perform the regeneration operation of the exhaust gas purification device 16. Since the temperature of the exhaust gas introduced into the turbocharger 15 is increased by reacting with the front-stage oxidation catalyst 27, the regeneration operation of the exhaust gas purification device 16 can be performed when the vehicle starts, and the output when starting the vehicle can be improved. can do.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

  For example, in the above-described embodiment, the NOx purification catalyst of the NOx purification device 24 is SCR. However, the present invention is not limited to this. For example, as shown in FIGS. 2 and 3, the NOx purification catalyst is LNT. NOx storage catalyst (LNT in the illustrated example) such as NAC, NAC, etc. In addition, in the case of the start assist system shown in FIGS. 2 and 3, the supply of additional fuel to the pre-stage oxidation catalyst 27 is performed by providing an exhaust pipe fuel injection injector 33 in the exhaust manifold 19 as shown in FIG. The fuel may be injected from the injection injector 33, and as shown in FIG. 3, the exhaust pipe fuel injection injector 33 is not provided, and the fuel is injected from the fuel injection nozzle 31 that injects fuel into the combustion chamber of the engine 10 ( Post injection) may be performed.

10 Engine 11 Exhaust passage 13 Intake passage 15 Turbocharger 16 Exhaust gas purification device 24 NOx purification device 25 PM purification device 27 Pre-stage oxidation catalyst 31 Fuel injection nozzle 33 Exhaust pipe fuel injection injector

Claims (4)

A start assist system for a vehicle in which a turbocharger is attached to an engine and an exhaust gas purifying device that requires regeneration operation is disposed on the exhaust gas flow downstream side of the turbocharger in the exhaust passage of the engine,
A pre-stage oxidation catalyst required for reacting additional fuel to raise the temperature of exhaust gas when performing a regeneration operation of the exhaust gas purification device is disposed upstream of the exhaust gas flow in the exhaust passage from the turbocharger,
The temperature of the exhaust gas introduced into the turbocharger by reacting the additional fuel with the front-stage oxidation catalyst by supplying the additional fuel to the front-stage oxidation catalyst at the start of the vehicle and performing the regeneration operation of the exhaust gas purification device. A starting assistance system for a vehicle, characterized in that the vehicle is raised.   2. The vehicle start assist system according to claim 1, wherein the exhaust gas purification device includes a NOx purification device for purifying nitrogen oxides in the exhaust gas and a PM purification device for purifying particulate matter in the exhaust gas. .   The vehicle start assist system according to claim 1 or 2, wherein the supply of the additional fuel to the front-stage oxidation catalyst is performed by injecting fuel from a fuel injection nozzle that injects fuel into a combustion chamber of the engine. An exhaust pipe fuel injection injector is provided in the exhaust passage;
The vehicle start assist system according to claim 1 or 2, wherein the supply of the additional fuel to the front-stage oxidation catalyst is performed by injecting fuel from the exhaust pipe fuel injection injector.

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