JP4811205B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  DPF (Diesel Particulate Filter) that collects PM (Particulate Matter), NOx catalyst that stores NOx, or DPNR (Diesel Particulate-NOx-Reduction) that simultaneously reduces PM and NOx to purify exhaust gas from internal combustion engines Exhaust treatment devices such as system) are installed in the exhaust passage. These exhaust treatment devices require a regeneration process periodically. When performing the regeneration treatment, it is necessary to supply exhaust gas containing unburned fuel to the exhaust treatment device. Therefore, a fuel addition valve is installed in the exhaust system, and fuel is injected into the exhaust gas from the fuel addition valve during the regeneration process.

JP 2001-280125 A Japanese Utility Model Publication No. 6-28218 JP 2003-278531 A JP 2006-22788 A JP 2005-16491 A

  In an internal combustion engine equipped with a fuel addition valve, in an operating state where the exhaust gas flow rate is low (such as in a low-medium rotation range), the exhaust gas flow is weaker than the penetration force of the injected fuel. Or the injected fuel is difficult to atomize. If the fuel adheres to the wall surface or the atomization is insufficient, there is a problem that more fuel must be injected from the fuel addition valve, resulting in a deterioration in fuel consumption.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. 2001-280125 discloses an apparatus for injecting fuel from a fuel addition valve during an opening period of an exhaust valve adjacent to the fuel addition valve. . However, even when fuel is injected from the fuel addition valve during the opening period of the adjacent exhaust valve, if the exhaust gas flow rate is small, the fuel wall adhesion and insufficient atomization cannot be solved sufficiently. Is the actual situation.

  In addition, a phenomenon occurs in which a mixture of soot and HC in the exhaust gas accumulates on the nozzle portion of the fuel addition valve exposed to the exhaust gas. If the injection hole of the nozzle portion is blocked by this deposit (hereinafter referred to as “deposit”), there is a problem that fuel cannot be injected from the fuel addition valve.

  In order to solve such a problem, a technique is known in which deposits are prevented by periodically injecting fuel from the fuel addition valve other than at the time of regeneration of the exhaust treatment device, and increasing opportunities for fuel injection. ing. However, in this case, there is a problem that the amount of fuel consumption increases and the fuel consumption deteriorates accordingly.

  Japanese Utility Model Laid-Open No. 6-28218 discloses a technique of installing a device for injecting air around a nozzle portion of a fuel addition valve in order to remove deposits. However, in this case, there is a problem that the manufacturing cost increases because the air injection device is installed.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine that can reduce the amount of fuel injected from the fuel addition valve.

In order to achieve the above object, a first invention is an exhaust purification device for an internal combustion engine,
A fuel addition valve that is installed for at least one cylinder of the internal combustion engine and injects fuel into an exhaust passage downstream of the exhaust valve;
Among the plurality of exhaust valves provided in the addition valve-installed cylinder in which the fuel addition valve is installed, the opening characteristic of the addition valve side exhaust valve that creates an exhaust gas flow that easily hits the nozzle portion of the fuel addition valve, and the fuel addition valve A variable valve mechanism that can make the opening characteristic of the non-addition valve side exhaust valve that makes the exhaust gas flow difficult to hit the nozzle part of
By controlling the variable valve mechanism according to the operating state of the internal combustion engine and / or the state of fuel injection from the fuel addition valve, the strength of the exhaust gas flow hitting the nozzle portion of the fuel addition valve is controlled. Exhaust gas flow control means;
It is characterized by providing.

The second invention is the first invention, wherein
The exhaust gas flow control means is configured so that the amount of exhaust gas passing through the addition valve side exhaust valve is greater than the amount of exhaust gas passing through the non-addition valve side exhaust valve when fuel is injected from the fuel addition valve. It includes a fuel diffusion promoting means for controlling the variable valve mechanism.

The third invention is the second invention, wherein
The fuel diffusion accelerating means is configured to increase the ratio of passing through the addition valve side exhaust valve out of the total exhaust gas discharged from the addition valve installation cylinder as the exhaust gas amount is in an operation state with a small amount. The variable valve mechanism is controlled.

According to a fourth invention, in any one of the first to third inventions,
The exhaust gas flow control means is configured so that the amount of exhaust gas passing through the addition valve side exhaust valve is larger than the amount of exhaust gas passing through the non-addition valve side exhaust valve when the internal combustion engine is decelerated. It includes deposit removing means for controlling the valve mechanism.

According to a fifth invention, in any one of the first to fourth inventions,
The exhaust gas flow control means is configured so that the amount of exhaust gas passing through the addition valve side exhaust valve is smaller than the amount of exhaust gas passing through the non-addition valve side exhaust valve when fuel is not injected from the fuel addition valve. It includes deposit accumulation suppressing means for controlling the variable valve mechanism.

The sixth invention is the fifth invention, wherein
When the engine speed and the engine load are lower than predetermined values, the deposit accumulation suppression means has an exhaust gas amount that passes through the addition valve side exhaust valve that is smaller than an exhaust gas amount that passes through the non-addition valve side exhaust valve. Thus, the variable valve mechanism is controlled.

  According to the first invention, it is easy to hit the nozzle portion of the fuel addition valve among the plurality of exhaust valves provided in the addition valve installation cylinder in which the fuel addition valve for injecting fuel is installed in the exhaust passage on the downstream side of the exhaust valve. The valve opening characteristics of the addition valve side exhaust valve that creates the exhaust gas flow and the valve opening characteristics of the non-addition valve side exhaust valve that creates an exhaust gas flow that does not easily hit the nozzle of the fuel addition valve differ depending on the variable valve mechanism. Can be. Then, by controlling the variable valve mechanism according to the operating state of the internal combustion engine and / or the fuel injection state from the fuel addition valve, the intensity of the exhaust gas flow hitting the nozzle portion of the fuel addition valve is controlled. be able to. For this reason, according to 1st invention, the intensity | strength of the exhaust gas flow which hits the nozzle part of a fuel addition valve can be controlled suitably according to a condition. As a result, it is possible to promote the diffusion of the injected fuel and to prevent the deposit from being deposited, and to save the fuel injected from the fuel addition valve.

  According to the second invention, the amount of exhaust gas passing through the addition valve side exhaust valve can be made larger than the amount of exhaust gas passing through the non-addition valve side exhaust valve during fuel injection from the fuel addition valve. Thereby, the exhaust gas flow which hits the nozzle part of a fuel addition valve at the time of the fuel injection from a fuel addition valve can be strengthened. Therefore, it is possible to prevent the fuel injected from the fuel addition valve from adhering to the wall of the passage even in an operation state such as a low / medium rotation range where the exhaust gas flow rate is small. (Diffusion) can be promoted. For this reason, since the fuel injected from the fuel addition valve can be utilized with high efficiency, the fuel injected from the fuel addition valve can be reduced.

  According to the third invention, during the fuel injection from the fuel addition valve, the smaller the exhaust gas amount is, the more exhaust gas discharged from the addition valve installation cylinder passes through the addition valve side exhaust valve. The ratio can be increased. As a result, the exhaust gas flow that hits the nozzle portion of the fuel addition valve can be more reliably strengthened even in an operating state such as a low-medium rotation region where the amount of exhaust gas is small. Therefore, the fuel injected from the fuel addition valve can be more reliably prevented from adhering to the passage wall surface, and atomization (diffusion) of the injected fuel can be further promoted. Further, according to the third aspect of the invention, the proportion of the exhaust gas that passes through the non-addition valve side exhaust valve can be increased as the exhaust gas amount increases. For this reason, even when the amount of exhaust gas is large, the exhaust gas can be discharged smoothly to the exhaust port, so that exhaust loss can be reduced. Further, even when the amount of exhaust gas is large, it is possible to avoid an excessive increase in internal EGR amount (residual gas amount), and it is possible to reliably prevent an increase in smoke since there is no shortage of intake air amount. Can do.

  According to the fourth invention, when the internal combustion engine is decelerated, the amount of exhaust gas passing through the addition valve side exhaust valve can be made larger than the amount of exhaust gas passing through the non-addition valve side exhaust valve. Accordingly, a strong exhaust gas flow can be applied to the nozzle portion of the fuel addition valve during deceleration, so that the deposited deposit can be blown off. Therefore, the fuel injection performed only for preventing the injection hole of the fuel addition valve from being clogged becomes unnecessary or the frequency thereof can be reduced. For this reason, fuel consumption can be improved. Further, since such control is performed at the time of deceleration, there is no influence on the combustion of the internal combustion engine (for example, increase in the amount of internal EGR), and there is no adverse effect on the operation of the internal combustion engine.

  According to the fifth aspect, the amount of exhaust gas passing through the addition valve side exhaust valve can be made smaller than the amount of exhaust gas passing through the non-addition valve side exhaust valve when fuel is not injected from the fuel addition valve. As a result, the chance of the exhaust gas flow hitting the nozzle portion of the fuel addition valve can be reduced, so that deposits can be effectively suppressed from depositing on the fuel addition valve. As a result, the fuel injection performed only to prevent the injection hole of the fuel addition valve from being clogged with deposits becomes unnecessary or the frequency thereof can be reduced. For this reason, fuel consumption can be improved.

  According to the sixth aspect of the present invention, when the engine speed and the engine load are lower than the predetermined values when fuel is not injected from the fuel addition valve, the amount of exhaust gas passing through the addition valve side exhaust valve is reduced to the non-addition valve side exhaust. The amount of exhaust gas passing through the valve can be reduced. As a result, it is possible to suppress the exhaust gas flow from hitting the nozzle portion of the fuel addition valve in an operating region where deposits are likely to accumulate. Therefore, deposits can be more effectively suppressed from depositing on the fuel addition valve.

Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.
Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a four-cycle diesel engine 10. It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source. Although the diesel engine 10 of the present embodiment is an in-line four-cylinder type, the number of cylinders and the cylinder arrangement of the diesel engine in the present invention are not limited to this.

  Hereinafter, although this embodiment demonstrates the case where this invention is applied to control of a diesel engine (compression ignition internal combustion engine), this invention is not limited to control of a diesel engine, A gasoline engine (spark ignition) Internal combustion engine) It can be applied to control of various other internal combustion engines.

  Each cylinder of the diesel engine 10 is provided with an injector 12 that injects fuel directly into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. In the common rail 14, high-pressure fuel pressurized by the supply pump 16 is stored. Then, fuel is supplied from the common rail 14 to each injector 12.

  The injector 12 may be capable of injecting fuel into the cylinder at an arbitrary timing a plurality of times during one cycle. That is, during one cycle, in addition to the main injection that is the main fuel injection, a pilot injection prior to the main injection may be performed.

  A turbocharger 24 is installed in the diesel engine 10 of the present embodiment. That is, the exhaust gas discharged from the exhaust port 22 of each cylinder of the diesel engine 10 joins at the exhaust manifold 20 and flows into the turbine of the turbocharger 24.

  A catalyst (filter with catalyst) 26 is provided in the exhaust passage 18 downstream of the turbocharger 24 as an exhaust treatment device for purifying exhaust gas. In the present embodiment, the catalyst 26 has both a function as a NOx storage reduction catalyst and a function of collecting PM (Particulate Matter).

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air sucked through the air cleaner 30 is compressed by the compressor of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed to the intake port 35 of each cylinder by the intake manifold 34.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  One end of an external EGR passage 40 is connected to the intake passage 28 in the vicinity of the intake manifold 34. The other end of the external EGR passage 40 is connected to the vicinity of the exhaust manifold 20 of the exhaust passage 18. In this system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the external EGR passage 40, that is, external EGR (Exhaust Gas Recirculation) can be performed.

  In the middle of the external EGR passage 40, an EGR cooler 42 for cooling the external EGR gas is provided. An EGR valve 44 is provided downstream of the EGR cooler 42 in the external EGR passage 40. By changing the opening degree of the EGR valve 44, the amount of exhaust gas passing through the external EGR passage 40, that is, the amount of external EGR can be adjusted.

  In this system, the external EGR amount can be adjusted not only by the opening degree of the EGR valve 44 but also by the opening degree of the intake throttle valve 36. When the opening of the intake throttle valve 36 is reduced to throttle the intake air, the intake pressure decreases, so the differential pressure from the back pressure (exhaust pressure) increases. That is, the differential pressure before and after the external EGR passage 40 increases. For this reason, the amount of external EGR can be increased.

  A fuel addition valve 46 for injecting (adding) fuel into the exhaust gas is installed in the vicinity of the exhaust port 22 of one cylinder (the leftmost cylinder in FIG. 1) of the diesel engine 10. Hereinafter, the cylinder in which the fuel addition valve 46 is installed is referred to as an “addition valve installation cylinder”.

  The system of this embodiment further includes an accelerator opening sensor 48 that detects the amount of depression of the accelerator pedal (accelerator opening) and an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 controls the operating state of the diesel engine 10 by operating each actuator according to a predetermined program based on the output of each sensor.

  FIG. 2 is a schematic plan view of the vicinity of the addition valve installed cylinder of the diesel engine 10. As shown in FIG. 2, the diesel engine 10 is provided with two intake valves 52 and two exhaust valves 56 for each cylinder. Corresponding to each of the two exhaust valves 56, the exhaust port 22 is also formed independently. The fuel addition valve 46 is arranged such that its nozzle portion faces one exhaust port 22 of the addition valve installation cylinder. Hereinafter, when it is necessary to distinguish between the two exhaust valves 56 and the exhaust port 22 of the addition valve installed cylinder, the exhaust valve 56 and the exhaust port 22 on which the fuel addition valve 46 is installed are referred to as “addition valve side”. The “exhaust valve 56a” and the “addition valve side exhaust port 22a” are referred to as “exhaust valve 56a” and “nonaddition valve side exhaust”. It will be referred to as “port 22b”.

  In such an addition valve installed cylinder, the exhaust gas flow exiting the addition valve side exhaust valve 56a passes through the addition valve side exhaust port 22a, and therefore easily hits the nozzle portion of the fuel addition valve 46. On the other hand, the exhaust gas flow exiting the non-addition valve side exhaust valve 56b passes through the non-addition valve side exhaust port 22b, and therefore does not easily hit the nozzle portion of the fuel addition valve 46.

  FIG. 3 is a view showing a cross section of one cylinder of the diesel engine 10 in the system shown in FIG. Hereinafter, the diesel engine 10 will be further described. As shown in FIG. 3, a crank angle sensor 62 that detects the rotation angle of the crankshaft 60 is attached in the vicinity of the crankshaft 60 of the diesel engine 10. The crank angle sensor 62 is connected to the ECU 50. The crank angle sensor 62 can detect the engine speed.

  Further, the diesel engine 10 is provided with an intake variable valve mechanism 54 that varies the valve timing of the intake valve 52 and an exhaust variable valve mechanism 58 that varies the valve timing of the exhaust valve 56. The intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are each connected to the ECU 50.

  The exhaust variable valve mechanism 58 of the present embodiment pauses the dual valve drive state in which the two exhaust valves 56 of the addition valve installed cylinder are driven together, and the non-addition valve side exhaust valve 56b in the closed state, and adds the exhaust valve side exhaust. It is assumed that it is possible to switch to a one-valve drive state in which only the valve 56a is driven. The exhaust variable valve mechanism 58 may be configured to perform such an operation only for the cylinder with the addition valve, or may be configured to be performed in common for all cylinders.

  The specific structure of the variable exhaust valve mechanism 58 is not particularly limited, and the above function may be realized by any mechanism. For example, a mechanism for mechanically switching between the double-valve drive state and the single-valve drive state using hydraulic pressure or the like, and the addition valve side exhaust valve 56a and the non-addition valve side exhaust valve 56b are configured by separate electromagnetically driven valves. It is possible to employ a mechanism for

  The intake variable valve mechanism 54 can change at least one of the valve opening phase, the operating angle, and the lift amount of the intake valve 52. The internal combustion engine in the present invention may be one that does not include the intake variable valve mechanism 54, that is, one that drives the intake valve 52 with a normal intake valve mechanism.

  In this system, as described above, PM in the exhaust gas can be collected by the catalyst 26. When PM accumulates in the catalyst 26, the ventilation resistance of the catalyst 26 increases. For this reason, in this system, PM regeneration control for burning and removing PM collected by the catalyst 26 is periodically performed. In PM regeneration control, fuel is added to the exhaust gas by injecting fuel from the fuel addition valve 46. The fuel added to the exhaust gas reacts (combusts) in the catalyst 26 and raises the temperature of the catalyst 26 to about 600 ° C., for example. Thereby, PM of the catalyst 26 can be burned.

[Features of Embodiment 1]
In general, in an internal combustion engine equipped with a fuel addition valve for adding fuel to exhaust gas, the fuel addition valve is compared with the penetration force of the injected fuel in an operating state such as a low and middle rotation region where the exhaust gas flow rate is small. Since the vicinity of the exhaust gas flow becomes weak, the injected fuel is likely to adhere to the wall surface of the passage, or the injected fuel is difficult to atomize. If the fuel adheres to the wall surface or the atomization is insufficient, there is a problem that more fuel must be injected from the fuel addition valve, resulting in a deterioration in fuel consumption. There is also a problem that the exhaust air-fuel ratio is disturbed by the subsequent evaporation of the fuel adhering to the wall surface.

  Therefore, in this embodiment, when fuel is injected from the fuel addition valve 46, the non-addition valve side exhaust valve 56b is stopped in a closed state, and only the addition valve side exhaust valve 56a is driven. Thus, all of the exhaust gas discharged from the addition valve installed cylinder flows in a concentrated manner to the addition valve side exhaust port 22a, so that the exhaust gas flow that hits the nozzle portion of the fuel addition valve 46 can be strengthened. Therefore, it is possible to prevent the fuel injected from the fuel addition valve 46 from adhering to the wall surface even in an operating state such as a low / medium rotation range where the exhaust gas flow rate is small. (Diffusion) can be promoted.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 4, it is first determined whether or not the degree of clogging of the catalyst 26 has reached the level at which PM regeneration control should be performed (hereinafter simply referred to as “presence / absence of clogging of the catalyst 26”). Step 100). The presence or absence of clogging of the catalyst 26 is determined based on, for example, the differential pressure between the upstream side and the downstream side of the catalyst 26 detected by a differential pressure sensor (not shown), the travel distance after the previous PM regeneration control, and the like. can do.

  If it is determined in step 100 that the catalyst 26 is clogged, it is necessary to perform PM regeneration control. Therefore, in this case, first, the exhaust variable valve mechanism 58 is controlled so that the non-addition valve side exhaust valve 56b is closed in a closed state and a one-valve drive state in which only the addition valve side exhaust valve 56a is driven. (Step 102). As a result, all of the exhaust gas discharged from the addition valve installed cylinder is concentrated in the addition valve side exhaust port 22a. Subsequently, fuel is injected from the fuel addition valve 46, and fuel is added to the exhaust gas (step 104). As a result, the unburned fuel in the exhaust gas reacts with the catalyst 26, the temperature of the catalyst 26 becomes high, and the PM accumulated in the catalyst 26 can be burned and removed.

  As described above, according to the present embodiment, when fuel is injected from the fuel addition valve 46, all exhaust gas discharged from the addition valve installation cylinder is caused to flow in a concentrated manner to the addition valve side exhaust port 22a. The exhaust gas flow hitting the nozzle portion of the fuel addition valve 46 can be strengthened. Therefore, it is possible to prevent the fuel injected from the fuel addition valve 46 from adhering to the wall of the passage even in an operating state such as a low / medium rotation range where the exhaust gas flow rate is small. Atomization (diffusion) can be promoted. For this reason, since the fuel injected from the fuel addition valve 46 can be used for PM regeneration with high efficiency, the fuel injected from the fuel addition valve 46 can be saved. In addition, since it is possible to prevent fuel from adhering to the wall surface of the passage, it is possible to avoid a situation in which the exhaust air-fuel ratio is disturbed by the subsequent evaporation of the fuel adhering to the wall surface.

In the first embodiment described above, the case of PM regeneration control has been described. However, fuel is injected from the fuel addition valve 46 also during rich spike control and S regeneration control. The rich spike control is control for reducing and removing NOx occluded in the catalyst 26 by reducing and purifying it to N ₂ using unburned fuel in the exhaust gas as a reducing agent. The S regeneration control is control for recovering sulfur poisoning caused by SOx (sulfur oxide) adsorbed on the catalyst 26. The present invention can also be applied when executing this rich spike control or S regeneration control.

  Further, in the configuration shown in FIG. 2, the addition valve side exhaust port 22a and the non-addition valve side exhaust port 22b are separated to the vicinity of the end face of the cylinder head via the partition wall 22c, but the partition wall 22c is shorter than this. Even if there is almost nothing, the strength of the exhaust gas flow hitting the nozzle portion of the fuel addition valve 46 can be increased by making the opening characteristics of the addition valve side exhaust valve 56a and the non-addition valve side exhaust valve 56b different. Change. Therefore, the present invention can be applied even when the partition 22c is shorter than the configuration shown in FIG.

  Further, in the first embodiment described above, the exhaust variable valve mechanism 56 corresponds to the “variable valve mechanism” in the first invention. Further, when the ECU 50 executes the processing of the routine shown in FIG. 4, the “exhaust gas flow control means” in the first invention executes the processing of steps 102 and 104 described above. "Fuel diffusion promoting means" has been realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 5. The description will focus on the differences from the above-described embodiment, and the description of the same matters will be simplified or omitted. To do. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later using the hardware configuration shown in FIGS.

  The variable exhaust valve mechanism 58 of the present embodiment has one or both of the lift amount and the operating angle (hereinafter referred to as the non-addition valve side exhaust valve 56b) in addition to the function of stopping the non-addition valve side exhaust valve 56b in the closed state. For the sake of convenience, it is simply expressed as “lift amount”).

[Specific Processing in Second Embodiment]
FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. Hereinafter, in FIG. 5, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 5, first, it is determined whether or not the catalyst 26 is clogged (step 100). If it is determined that the catalyst 26 is clogged, PM regeneration control is performed as follows. The First, it is determined whether the current engine speed is in a low rotation range, a medium rotation range, or a high rotation range, which is divided in advance (step 106).

  If it is determined in step 106 that the engine is in the low rotation range, it can be determined that the amount of exhaust gas is small. In this case, similarly to the first embodiment, the non-addition valve side exhaust valve 56b is closed in a closed state, and the variable exhaust valve is operated so as to be in a one-valve drive state in which only the addition valve side exhaust valve 56a is driven. The mechanism 58 is controlled (step 108).

  On the other hand, if it is determined in step 106 that the engine is in the middle rotation range, it can be determined that the amount of exhaust gas is medium. In this case, even if a part of the exhaust gas discharged from the addition valve installed cylinder flows to the non-addition valve side exhaust port 22b, it can be determined that the exhaust gas flow that hits the nozzle portion of the fuel addition valve 46 is sufficiently strong. Therefore, in this case, the variable exhaust valve operating mechanism is configured such that the non-addition valve side exhaust valve 56b is driven with a low lift while the addition valve side exhaust valve 56a is driven with a normal lift (large lift). 58 is controlled. As a result, a part of the exhaust gas discharged from the addition valve installed cylinder is in a state of flowing to the non-addition valve side exhaust port 22b.

  If it is determined in step 106 that the engine is in the high rotation range, it can be determined that the amount of exhaust gas is large. In this case, the exhaust gas that hits the nozzle portion of the fuel addition valve 46 even if a larger proportion of the exhaust gas discharged from the addition valve installed cylinder than the middle rotation range flows to the non-addition valve side exhaust port 22b. It can be judged that the current is strong enough. Therefore, in this case, the variable exhaust valve mechanism 58 is controlled so that the non-addition valve side exhaust valve 56b is driven with a medium lift while the addition valve side exhaust valve 56a is driven with a normal lift. The As a result, a larger proportion of the exhaust gas discharged from the addition valve-installed cylinder than in the middle rotation region flows into the non-addition valve side exhaust port 22b.

  Following the processing of step 108, 110 or 112 described above, fuel is injected from the fuel addition valve 46, and fuel is added to the exhaust gas (step 104).

  According to the process of the present embodiment described above, the non-addition valve side exhaust port 22b can be operated with a normal lift (large lift) at any of the low, middle and high rotation speeds when fuel is injected from the fuel addition valve 46. Compared with the case of driving, the flow of exhaust gas hitting the nozzle portion of the fuel addition valve 46 can be strengthened. For this reason, as in the first embodiment, the fuel injected from the fuel addition valve 46 can be prevented from adhering to the wall of the passage, and atomization (diffusion) of the injected fuel can be promoted. Can do.

  Furthermore, according to this embodiment, the higher the engine speed, that is, the greater the amount of exhaust gas, the greater the proportion of exhaust gas that passes through the non-addition valve side exhaust valve 56b. For this reason, even when the amount of exhaust gas is large, the exhaust gas can be discharged smoothly to the exhaust port 22, so that exhaust loss can be reduced. Further, even when the amount of exhaust gas is large, it is possible to avoid an excessive increase in internal EGR amount (residual gas amount), and it is possible to reliably prevent an increase in smoke since there is no shortage of intake air amount. Can do.

  In the routine shown in FIG. 5, the lift amount of the non-addition valve side exhaust valve 56b is changed in three stages according to the engine speed, but it may be changed continuously according to the engine speed. Good. In the routine shown in FIG. 5, the lift amount of the non-addition valve side exhaust valve 56b is set to a medium lift in the high rotation range. When the exhaust gas flow in the side exhaust port 22a is sufficiently strong, both the lift amount of the addition valve side exhaust valve 56a and the non-addition valve side exhaust valve 56b may be set to a large lift in the high speed range.

  In the second embodiment described above, the “fuel diffusion promoting means” according to the third aspect of the present invention is realized by the ECU 50 executing the routine shown in FIG.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 6. The description will focus on the differences from the above-described embodiment, and the description of the same matters will be simplified or omitted. To do. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 6 to be described later using the hardware configuration shown in FIGS.

  As in the first embodiment, the variable exhaust valve mechanism 58 of the present embodiment is in a double-valve drive state in which the two exhaust valves 56 of the addition valve installed cylinder are driven together, and the non-addition valve side exhaust valve 56b is in a closed state. , And can be switched to a one-valve drive state in which only the addition valve side exhaust valve 56a is driven.

[Features of Embodiment 3]
In the present embodiment, when the diesel engine 10 is decelerated, that is, when the engine speed is higher than a predetermined value and the accelerator is OFF, the non-addition valve side exhaust valve 56b is closed in a closed state, and the addition valve side exhaust is exhausted. The variable exhaust valve mechanism 58 is controlled so as to be in a one-valve drive state in which only the valve 56a is driven. Thereby, at the time of deceleration, all exhaust gas (air) discharged from the addition valve installed cylinder flows in a concentrated manner to the addition valve side exhaust port 22a, so that a strong exhaust gas flow is applied to the nozzle portion of the fuel addition valve 46. Can do. With this strong exhaust gas flow, deposits adhering to the nozzle portion of the fuel addition valve 46 can be blown off, and clogging of the injection holes due to deposit accumulation can be prevented.

[Specific Processing in Embodiment 3]
FIG. 6 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 6, it is first determined whether or not the diesel engine 10 is in a decelerating state (step 114). Specifically, when the engine speed is higher than a predetermined value and the accelerator is OFF, it is determined that the vehicle is in a deceleration state.

  If it is determined in step 114 that the vehicle is decelerating, the non-addition valve-side exhaust valve 56b is then closed in a closed state, and a one-valve drive state in which only the addition valve-side exhaust valve 56a is driven is set. Then, the exhaust variable valve mechanism 58 is controlled (step 116). As a result, all of the exhaust gas (air) discharged from the addition valve-installed cylinder is concentrated in the addition valve side exhaust port 22a. As a result, a strong exhaust gas flow strikes the nozzle portion of the fuel addition valve 46, so that deposits attached to the nozzle portion of the fuel addition valve 46 can be blown away.

  As described above, according to the present embodiment, the deposit attached to the nozzle portion of the fuel addition valve 46 can be blown off when the diesel engine 10 is decelerated. Therefore, the fuel injection performed only to prevent the injection hole of the fuel addition valve 46 from being clogged becomes unnecessary or the frequency thereof can be reduced. For this reason, fuel consumption can be improved.

  In addition, since the one-valve drive state for blowing off the deposit is performed at the time of deceleration, the non-addition valve-side exhaust valve 56b being in the closed state affects the combustion of the diesel engine 10 (for example, an increase in the amount of internal EGR) ) Does not adversely affect the operation of the diesel engine 10.

  Further, since fuel injection from the injector 12 is normally stopped during deceleration, pure air that does not contain HC and soot that causes deposits is discharged as exhaust gas from the diesel engine 10. According to the present embodiment, the deposit can be blown off by this air flow, and no deposit is deposited during that time, so that a higher deposit removing effect can be obtained.

  In the present embodiment, the non-addition valve side exhaust valve 56b is closed in a closed state during deceleration, but the non-addition valve side exhaust valve 56b is driven with a lift amount smaller than the addition valve side exhaust valve 56a. It may be. That is, the effect of this embodiment can be obtained if the amount of exhaust gas passing through the addition valve side exhaust valve 56a is greater than the amount of exhaust gas passing through the non-addition valve side exhaust valve 56b during deceleration. .

  In the present embodiment, the fuel injection from the injector 12 does not necessarily have to be completely stopped during deceleration.

  In the third embodiment described above, the “deposit removal means” according to the fourth aspect of the present invention is implemented by the ECU 50 executing the routine shown in FIG.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG. 7. The description will focus on the differences from the third embodiment described above, and the same matters will be simplified or described. Omitted. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 7 described later using the hardware configuration shown in FIGS.

  As in the first embodiment, the variable exhaust valve mechanism 58 of the present embodiment is in a double-valve drive state in which the two exhaust valves 56 of the addition valve installed cylinder are driven together, and the non-addition valve side exhaust valve 56b is in a closed state. , And can be switched to a one-valve drive state in which only the addition valve side exhaust valve 56a is driven.

[Features of Embodiment 4]
In this embodiment, when the catalyst 26 is clogged at the time of deceleration, that is, when it is necessary to perform PM regeneration control, fuel is injected from the fuel addition valve 46 after the one-valve drive state is set. PM regeneration control is to be carried out. On the other hand, when the catalyst 26 is not clogged during deceleration, the deposit of the fuel addition valve 46 is blown off by setting the one-valve drive state as in the third embodiment.

[Specific Processing in Embodiment 4]
FIG. 7 is a flowchart of a routine executed by the ECU 50 in the present embodiment. According to the routine shown in FIG. 7, first, it is determined whether or not the catalyst 26 is clogged (step 118). If it is determined that there is no clogging, it is then determined whether or not the vehicle is in a deceleration state (step 120). If it is determined that the vehicle is in a deceleration state, the same as in the third embodiment. Then, the exhaust variable valve mechanism 58 is controlled so that the non-addition valve-side exhaust valve 56b is closed in a closed state and the one-valve drive state in which only the addition valve-side exhaust valve 56a is driven (step 122). As a result, all of the exhaust gas (air) discharged from the addition valve-installed cylinder is concentrated in the addition valve side exhaust port 22a. As a result, a strong exhaust gas flow strikes the nozzle portion of the fuel addition valve 46, so that deposits attached to the nozzle portion of the fuel addition valve 46 can be blown away. That is, the same effect as in the third embodiment can be obtained.

  On the other hand, if it is determined in step 118 that the catalyst 26 is clogged, it is next determined whether or not the vehicle is in a decelerating state (step 124). Then, the exhaust variable valve operating mechanism 58 is controlled so that the non-addition valve side exhaust valve 56b is closed in a closed state and a one-valve drive state in which only the addition valve side exhaust valve 56a is driven (step 126). As a result, all of the exhaust gas (air) discharged from the addition valve-installed cylinder is concentrated in the addition valve side exhaust port 22a. In this state, fuel is injected from the fuel addition valve 46 (step 128), and PM regeneration control is performed. In this way, since the fuel is injected in a state where a strong exhaust gas flow hits the nozzle portion of the fuel addition valve 46, it is possible to prevent the injected fuel from adhering to the wall surface of the passage. Fuel atomization (diffusion) can be promoted. That is, the same effect as in the first embodiment can be obtained.

  In the above-described fourth embodiment, the ECU 50 executes the processes of steps 120 and 122 so that the “deposit removing means” in the fourth invention executes the processes of steps 126 and 128. The “fuel diffusion promoting means” in the second invention is realized.

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIG. 8. The description will focus on the differences from the above-described embodiments, and the description of the same matters will be simplified or omitted. To do. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 8 to be described later using the hardware configuration shown in FIGS. 1 to 3.

  The exhaust variable valve mechanism 58 of the present embodiment is configured so that the two exhaust valves 56 of the addition valve installed cylinders are driven together, the addition valve side exhaust valve 56a is closed, and the non-addition valve side exhaust is stopped. It is assumed that it is possible to switch to a one-valve drive state in which only the valve 56b is driven.

[Features of Embodiment 5]
In general, in the low speed range of the diesel engine 10, the amount of air is small, so HC in the exhaust gas increases. HC acts like an adhesive in depositing. For this reason, deposits are likely to accumulate on the fuel addition valve 46 in the low rotation range. Further, in the low rotation range where the amount of air is small, the exhaust gas flow hitting the fuel addition valve 46 is also weak, so that the deposited deposit is difficult to blow off. Therefore, in general, it can be said that the deposit of the fuel addition valve 46 tends to accumulate particularly in the low rotation range.

  Therefore, in the present embodiment, when the engine is in the low-rotation low-medium load region, the addition valve side exhaust valve 56a is stopped in the closed state, and the exhaust is performed so that the one-valve drive state in which only the non-addition valve side exhaust valve 56b is driven. The variable valve mechanism 58 was controlled. Thereby, in the low-rotation low-medium load region, all of the exhaust gas discharged from the addition valve installation cylinder can flow to the non-addition valve side exhaust port 22b. As a result, the chance of exhaust gas containing a large amount of HC hitting the nozzle portion of the fuel addition valve 46 can be reduced, so that deposits can be prevented from depositing on the fuel addition valve 46.

  Moreover, since the internal EGR amount can be increased by resting the addition valve side exhaust valve 56a in the closed state in the low-rotation low-medium load region, an effect of reducing the emission (NOx emission amount) can also be obtained.

  In addition, in the low rotation high load region, when the addition valve side exhaust valve 56a is stopped in the closed state, soot is easily generated due to the decrease in the air amount accompanying the increase in the internal EGR amount. Therefore, the above control is not performed in the low rotation and high load range.

[Specific Processing in Embodiment 5]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 8, it is first determined whether or not the engine is in the low rotation / low / medium load range (step 130). Specifically, when the engine speed and the engine load are each lower than a predetermined value set in advance, it is determined that the engine is in the low rotation / low / medium load region.

  If it is determined in step 130 that the engine is in the low rotation / low / medium load range, then the addition valve side exhaust valve 56a is closed in a closed state, and only the non-addition valve side exhaust valve 56b is driven. The exhaust variable valve mechanism 58 is controlled so as to be in the state (step 130). As a result, the exhaust gas does not flow to the addition valve side exhaust port 22a, so that deposits can be prevented from being deposited on the nozzle portion of the fuel addition valve 46.

  As described above, according to the routine processing shown in FIG. 8, it is possible to prevent the exhaust gas flow from hitting the fuel addition valve 46 in the low rotation / low / medium load range where deposits are likely to accumulate. Accumulation of deposits on the valve 46 can be effectively suppressed. As a result, fuel injection that is performed only to prevent the injection hole of the fuel addition valve 46 from being clogged with deposits is unnecessary, or the frequency thereof can be reduced. For this reason, fuel consumption can be improved.

  In addition, in Embodiment 5 described above, the stop in the closed state of the addition valve side exhaust valve 56a is executed in the low rotation low and middle load range, but when it can be executed in other operation ranges, May be executed.

  Further, instead of pausing the addition valve side exhaust valve 56a in the closed state, the lift amount of the addition valve side exhaust valve 56a may be made smaller than the lift amount of the non-addition valve side exhaust valve 56b. Even in this case, the amount of exhaust gas hitting the fuel addition valve 46 can be reduced as compared with the case where both the exhaust valves 56 are equally lifted, so that the deposit accumulation suppressing effect can be obtained.

  In the fifth embodiment described above, the “deposit accumulation suppressing means” in the fifth and sixth aspects of the present invention is realized by the ECU 50 executing the routine shown in FIG.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a typical top view near the addition valve installation cylinder of the diesel engine in the embodiment of the present invention. It is a figure which shows the cross section of one cylinder of the diesel engine in embodiment of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 18 Exhaust passage 19 Exhaust temperature sensor 20 Exhaust manifold 22 Exhaust port 22a Addition valve side exhaust port 22b Non-addition valve side exhaust port 22c Partition 24 Turbocharger 26 Catalyst 28 Intake passage 34 Intake manifold 35 Intake Port 36 Inlet throttle valve 38 Air flow meter 40 External EGR passage 44 EGR valve 46 Fuel addition valve 48 Accelerator opening sensor 50 ECU
52 Intake valve 54 Intake variable valve mechanism 56 Exhaust valve 56a Addition valve side exhaust valve 56b Non-addition valve side exhaust valve 58 Exhaust variable valve mechanism 62 Crank angle sensor 64 Piston

Claims (6)

A fuel addition valve that is installed for at least one cylinder of the internal combustion engine and injects fuel into an exhaust passage downstream of the exhaust valve;
Among the plurality of exhaust valves provided in the addition valve installation cylinder in which the fuel addition valve is installed, the valve opening characteristic of the addition valve side exhaust valve that creates an exhaust gas flow corresponding to the nozzle portion of the fuel addition valve, and the addition valve side exhaust A variable valve mechanism capable of making the valve opening characteristic of the non-addition valve side exhaust valve that creates an exhaust gas flow far away from the nozzle portion compared to the exhaust gas flow created by the valve, and a different characteristic;
By controlling the variable valve mechanism according to the operating state of the internal combustion engine and / or the fuel injection state from the fuel addition valve, the amount of exhaust gas passing through the addition valve side exhaust valve and the non-addition valve side Exhaust gas flow control means for controlling the ratio of the amount of exhaust gas passing through the exhaust valve ;
An exhaust emission control device for an internal combustion engine, comprising:
  The exhaust gas flow control means is configured so that the amount of exhaust gas passing through the addition valve side exhaust valve is greater than the amount of exhaust gas passing through the non-addition valve side exhaust valve when fuel is injected from the fuel addition valve. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising fuel diffusion promoting means for controlling the variable valve mechanism.   The fuel diffusion accelerating means is configured to increase the ratio of passing through the addition valve side exhaust valve out of the total exhaust gas discharged from the addition valve installation cylinder as the exhaust gas amount is in an operation state with a small amount. 3. The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein the variable valve mechanism is controlled.   The exhaust gas flow control means is configured so that the amount of exhaust gas passing through the addition valve side exhaust valve is larger than the amount of exhaust gas passing through the non-addition valve side exhaust valve when the internal combustion engine is decelerated. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising deposit removing means for controlling the valve mechanism.   The exhaust gas flow control means is configured so that the amount of exhaust gas passing through the addition valve side exhaust valve is smaller than the amount of exhaust gas passing through the non-addition valve side exhaust valve when fuel is not injected from the fuel addition valve. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising deposit accumulation suppressing means for controlling the variable valve mechanism.   When the engine speed and the engine load are lower than predetermined values, the deposit accumulation suppression means has an exhaust gas amount that passes through the addition valve side exhaust valve that is smaller than an exhaust gas amount that passes through the non-addition valve side exhaust valve. 6. The exhaust gas purification apparatus for an internal combustion engine according to claim 5, wherein the variable valve mechanism is controlled as described above.

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