JP2018119496A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the worsening of fuel economy when raising the temperatures of exhaust gas and a post-processing member.SOLUTION: An exhaust emission control device for an internal combustion engine 1 having first and second cylinder groups A, B includes a first variable valve system 36A for varying the operation characteristics of intake valves of the first cylinder group, an oxidation catalyst 22 and post-processing members 23, 24 on the downstream side thereof, and a control unit 100 for controlling the operation state of each cylinder group and the first variable valve system. When the operating condition of the internal combustion engine is in a first region, the control unit executes a first control mode to control the first variable valve system so that the intake valves of the first cylinder group have the same operation characteristics as intake valves of the second cylinder group, while allowing all-cylinder operation of the internal combustion engine. When the operating condition of the internal combustion engine is in a second region on the lower-speed and lower-load side, the control unit executes a second control mode to control the first variable valve system so that the packing efficiency of the first cylinder group is smaller than the packing efficiency of the second cylinder group, while allowing the cylinder-cutoff operation of the internal combustion engine with the first cylinder group halted.SELECTED DRAWING: Figure 1

Description

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

  2. Description of the Related Art An exhaust gas purification apparatus for an internal combustion engine, particularly a diesel engine, is known that includes an oxidation catalyst provided in an exhaust passage and a post-processing member provided on the downstream side of the oxidation catalyst in the exhaust passage. The post-processing member includes, for example, a filter for collecting particulate matter (PM) in the exhaust and a NOx catalyst that is provided on the downstream side of the filter and purifies NOx in the exhaust.

  For the purpose of increasing the temperature of the post-processing member, the amount of fuel-derived unburned components such as HC and CO supplied to the oxidation catalyst is intentionally increased. As a result, the oxidation reaction or combustion reaction of the unburned components in the oxidation catalyst becomes more active, and the exhaust gas discharged from the oxidation catalyst is heated. By supplying this heated exhaust gas to the post-processing member, the post-processing member can be heated to increase its activity.

Japanese Patent Laid-Open No. 2006-153621

  In general, the temperature of the exhaust gas and the post-processing member is increased by at least one of a reduction in the opening of the exhaust throttle valve, a reduction in the opening of the intake throttle valve, and post-injection of fuel. However, both of these have the problem of significantly remarkably deteriorating fuel consumption.

  When the opening of the exhaust throttle valve is decreased, the pumping loss is increased and the engine output is decreased. Therefore, the fuel injection amount is increased to compensate for this. As a result, the temperature of the exhaust can be raised, but the fuel consumption increases in exchange for this.

  Even when the opening of the intake throttle valve is decreased, the pumping loss increases and the engine output decreases. Therefore, the fuel injection amount is increased to compensate for this. In addition, the intake of relatively cool fresh air is also suppressed. Although the temperature of the exhaust can be raised by these, the fuel consumption increases in exchange for this.

  In the case of fuel post-injection, the fuel for the post-injection is inevitably additionally injected into the cylinder, which increases the fuel consumption and causes problems such as fuel mixing into the lubricating oil. Become.

  Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine that can suppress deterioration in fuel consumption when the temperature of exhaust gas and a post-processing member is raised.

According to one aspect of the invention,
An exhaust emission control device for an internal combustion engine having a first cylinder group and a second cylinder group formed by dividing a plurality of cylinders,
A first variable valve mechanism for varying the operating characteristics of the intake valves of the first cylinder group;
An oxidation catalyst provided in the exhaust passage;
A post-processing member provided downstream of the oxidation catalyst in the exhaust passage;
A control unit configured to control operating states of the first cylinder group and the second cylinder group and the first variable valve mechanism;
With
The control unit is
When the operating state of the internal combustion engine is in a predetermined first region, the first cylinder group and the second cylinder group are operated to operate all cylinders of the internal combustion engine, and the intake valve of the first cylinder group is Executing a first control mode for controlling the first variable valve mechanism so as to have the same operating characteristics as the intake valves of the second cylinder group;
When the operating state of the internal combustion engine is in a predetermined second region at a lower speed and a lower load side than the first region, the first cylinder group is deactivated and the second cylinder group is operated to operate the internal combustion engine. And the second control mode for controlling the first variable valve mechanism is executed so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. An exhaust emission control device for an internal combustion engine is provided.

Preferably, the exhaust purification device further includes a temperature detection unit for detecting an exhaust temperature at a predetermined position of the exhaust passage,
The control unit, when the operating state of the internal combustion engine is in the second region,
When the exhaust gas temperature detected by the temperature detector is lower than the first temperature threshold and higher than the second temperature threshold lower than the first temperature threshold, the second control mode is executed,
When the exhaust gas temperature detected by the temperature detector is equal to or lower than the second temperature threshold, the first cylinder group is deactivated and the second cylinder group is operated to reduce the internal combustion engine to perform the cylinder reduction operation. Third control for supplying the fuel in such a manner that the cylinder group is not burned in-cylinder and controlling the first variable valve mechanism so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. Configured to run mode.

Preferably, the post-processing member includes a filter for collecting particulate matter in the exhaust, and a NOx catalyst provided on the downstream side of the filter to purify NOx in the exhaust,
The predetermined position is the position of the inlet of the filter or the position of the inlet of the NOx catalyst.

Preferably, the exhaust emission control device further includes a deposition amount detection unit for detecting a deposition amount of particulate matter in the filter,
The control unit is
When the operating state of the internal combustion engine is in the second region and the accumulation amount detected by the accumulation amount detection unit is less than a predetermined accumulation amount threshold, the exhaust temperature detected by the temperature detection unit is the first temperature. The second control mode is executed when the temperature is lower than the temperature threshold and higher than the second temperature threshold, and the third control mode is executed when the exhaust temperature detected by the temperature detector is lower than the second temperature threshold.

Preferably, the control unit is
When the operating state of the internal combustion engine is in the second region and the accumulation amount detected by the accumulation amount detection unit is equal to or greater than the accumulation amount threshold, the exhaust temperature detected by the temperature detection unit is the first temperature. The third control mode is executed when the temperature is below a third temperature threshold value that is higher than the threshold value, and the first control mode is executed when the exhaust gas temperature detected by the temperature detector is higher than the third temperature threshold value.

Preferably, the exhaust purification device further includes a second variable valve mechanism for making the operating characteristic of the intake valve of the second cylinder group variable,
The control unit controls the second variable valve mechanism so that a charging efficiency of the second cylinder group is smaller than that in the execution of the first control mode when the second control mode and the third control mode are executed. To do.

  Preferably, when the third control mode is executed, the control unit supplies a smaller amount of fuel to the first cylinder group than the fuel supplied when the first control mode is executed.

  Preferably, the control unit supplies fuel to the first cylinder group at a timing delayed from a fuel supply timing to the second cylinder group when the third control mode is executed.

Preferably, the internal combustion engine is
A first exhaust manifold and a second exhaust manifold formed independently for the first cylinder group and the second cylinder group;
And an EGR passage connected to the second exhaust manifold.

According to another aspect of the invention,
An exhaust emission control device for an internal combustion engine having a first cylinder group and a second cylinder group formed by dividing a plurality of cylinders,
A first variable valve mechanism for varying the operating characteristics of the intake valves of the first cylinder group;
An oxidation catalyst provided in the exhaust passage;
A post-processing member provided downstream of the oxidation catalyst in the exhaust passage;
A control unit configured to control operating states of the first cylinder group and the second cylinder group and the first variable valve mechanism;
With
The control unit is
When the operating state of the internal combustion engine is in a predetermined first region, the first cylinder group and the second cylinder group are operated to cause the internal combustion engine to operate all cylinders, and the first cylinder group is the second cylinder. Executing a first control mode for controlling the first variable valve mechanism so as to have the same operating characteristics as the group;
When the operating state of the internal combustion engine is in a predetermined second region at a lower speed and a lower load side than the first region, the first cylinder group is deactivated and the second cylinder group is operated to operate the internal combustion engine. And the second control mode for controlling the first variable valve mechanism is executed so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. An exhaust emission control device for an internal combustion engine is provided.

  Hereinafter, preferred embodiments in other embodiments will be described.

Preferably, the control unit is
When the operating state of the internal combustion engine is in a predetermined third region at a lower speed and a lower load side than the second region, the first cylinder group is deactivated and the second cylinder group is operated to operate the internal combustion engine The first cylinder group is operated so as to reduce cylinders, and fuel is supplied in such a manner that the first cylinder group is not burned in-cylinder, so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. The third control mode for controlling the variable valve mechanism is executed.

  Preferably, the post-processing member includes a filter for collecting particulate matter in the exhaust, and a NOx catalyst provided on the downstream side of the filter for purifying NOx in the exhaust.

Preferably, the exhaust emission control device further includes a deposition amount detection unit for detecting a deposition amount of particulate matter in the filter,
The control unit is
When the accumulation amount detected by the accumulation amount detection unit is less than a predetermined accumulation amount threshold,
When the operating state of the internal combustion engine is in the first region, the first control mode is executed. When the operating state of the internal combustion engine is in the second region, the second control mode is executed. When the operating state is in the third region, the third control mode is executed.

Preferably, the control unit is
When the accumulation amount detected by the accumulation amount detection unit is equal to or greater than the accumulation amount threshold,
When the operating state of the internal combustion engine is in the first region, the first control mode is executed, and the operating state of the internal combustion engine is a region at a lower speed and lower load than the first region, and When in a predetermined fourth area different from the second area and the third area, the third control mode is executed.

Preferably, the exhaust purification device further includes a second variable valve mechanism for making the operating characteristic of the intake valve of the second cylinder group variable,
The control unit controls the second variable valve mechanism so that a charging efficiency of the second cylinder group is smaller than that in the execution of the first control mode when the second control mode and the third control mode are executed. To do.

  Preferably, when the third control mode is executed, the control unit supplies a smaller amount of fuel to the first cylinder group than the fuel supplied when the first control mode is executed.

  Preferably, the control unit supplies fuel to the first cylinder group at a timing delayed from a fuel supply timing to the second cylinder group when the third control mode is executed.

Preferably, the internal combustion engine is
A first exhaust manifold and a second exhaust manifold formed independently for the first cylinder group and the second cylinder group;
And an EGR passage connected to the second exhaust manifold.

  According to the present invention, it is possible to suppress deterioration in fuel consumption when the exhaust gas and the post-processing member are heated.

It is the schematic which shows the structure of 1st Embodiment of this invention. It is a valve lift diagram which shows the operating characteristic of the intake valve of a 1st and 2nd cylinder group. It is a timing chart which shows an example of fuel injection timing. It is a figure which shows each map. It is a flowchart of the control routine in 1st Embodiment. It is a figure which shows each map in 2nd Embodiment. It is a flowchart of the control routine in 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments.

[First Embodiment]
FIG. 1 is a schematic diagram showing the configuration of the first embodiment of the present invention. An internal combustion engine (also referred to as an engine) 1 is a multi-cylinder engine mounted on a vehicle (not shown). In the present embodiment, the vehicle is a large vehicle such as a truck, and the engine 1 as a vehicle power source mounted on the vehicle is an in-line four-cylinder diesel engine. However, there are no particular limitations on the types, types, applications, and the like of the vehicle and the internal combustion engine. For example, the vehicle may be a small vehicle such as a passenger car, and the engine 1 may be a gasoline engine.

  The engine 1 includes an engine body 2, an intake passage 3 and an exhaust passage 4 connected to the engine body 2, a turbocharger 14, and a fuel injection device 5. The engine body 2 includes structural parts such as a cylinder head, a cylinder block, and a crankcase, and movable parts such as a piston, a crankshaft, and a valve housed therein.

  The fuel injection device 5 includes a common rail fuel injection device, and includes a fuel injection valve, that is, an injector 7 provided in each cylinder, and a common rail 8 connected to the injector 7. The injector 7 is an in-cylinder injector that directly injects fuel into the cylinder 9, that is, into the combustion chamber. The common rail 8 stores the fuel injected from the injector 7 in a high pressure state.

  The intake passage 3 is mainly defined by an intake manifold 10 connected to the engine body 2 (particularly a cylinder head) and an intake pipe 11 connected to the upstream end of the intake manifold 10. The intake manifold 10 distributes and supplies the intake air sent from the intake pipe 11 to the intake ports of each cylinder. The intake pipe 11 is provided with an air cleaner 12, an air flow meter 13, a compressor 14 </ b> C of the turbocharger 14, an intercooler 15, and an electronically controlled intake throttle valve 16 in order from the upstream side. The air flow meter 13 is a sensor for detecting an intake air amount per unit time of the engine 1, that is, an intake flow rate, and is also referred to as a mass air flow (MAF) sensor or the like.

  The exhaust passage 4 is mainly defined by an exhaust manifold 20 connected to the engine body 2 (particularly a cylinder head) and an exhaust pipe 21 connected to the downstream side of the exhaust manifold 20. The exhaust manifold 20 collects exhaust gas sent from the exhaust port of each cylinder. A turbine 14 </ b> T of the turbocharger 14 is provided between the exhaust pipe 21 or between the exhaust manifold 20 and the exhaust pipe 21. In the exhaust passage 4 on the downstream side of the turbine 14T, an oxidation catalyst 22, a filter 23, a selective reduction type NOx catalyst (SCR) 24, and an ammonia oxidation catalyst 26 are provided in this order from the upstream side. An addition valve 25 for adding urea water as a reducing agent is provided in the exhaust passage 4 between the filter 23 and the NOx catalyst 24.

  The oxidation catalyst 22 and the filter 23 carry a noble metal such as Pt or Pd that forms a catalyst component. The oxidation catalyst 22 oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust, and heats the exhaust gas with the reaction heat at this time. The filter 23 is a so-called continuous regeneration type diesel particulate filter, and collects particulate matter (also referred to as PM) contained in the exhaust gas. The filter 23 is a so-called wall flow type in which the openings at both ends of the honeycomb structure base material are alternately closed in a checkered pattern. On the other hand, both ends of the base material of the oxidation catalyst 22 are opened, and the oxidation catalyst 22 is a so-called flow-through type.

  The NOx catalyst 24 reduces and purifies NOx in the exhaust gas using ammonia derived from the urea water added from the addition valve 25 as a reducing agent. The ammonia oxidation catalyst 26 oxidizes and purifies excess ammonia discharged from the NOx catalyst 24. The NOx catalyst 24 and the ammonia oxidation catalyst 26 also carry precious metals such as Pt and Pd that form catalyst components, which are also of the flow-through type. The NOx catalyst 24 may be a storage reduction type NOx catalyst (LNT).

  Thus, in the present embodiment, the post-processing member that performs the exhaust post-treatment is provided on the exhaust passage 4 downstream of the oxidation catalyst 22. The post-processing member includes a filter 23 as a first post-processing member, a NOx catalyst 24 as a second post-processing member, and further includes an ammonia oxidation catalyst 26 as a third post-processing member. As will be described in detail later, the present embodiment is mainly directed to raising the temperature of the exhaust gas supplied to the filter 23 and the NOx catalyst 24 and raising the temperature of the exhaust gas itself.

  As the temperature of the filter 23 increases, the activity of the filter 23 increases, and the rate of reduction of PM deposited in the filter 23 tends to increase. Therefore, raising the temperature of the filter 23 is beneficial in reducing the amount of accumulated PM. On the other hand, as the temperature of the NOx catalyst 24 increases, the activity of the NOx catalyst 24 increases and the NOx purification rate tends to increase. Therefore, raising the temperature of the NOx catalyst 24 is beneficial for increasing the NOx purification rate.

  The engine 1 also includes an EGR device 30. The EGR device 30 includes an EGR passage 31 for returning a part of exhaust gas (referred to as EGR gas) in the exhaust passage 4 (especially in the exhaust manifold 20) to the intake passage 3 (particularly in the intake manifold 10), and EGR. An EGR cooler 32 that cools the EGR gas flowing in the passage 31 and an EGR valve 33 for adjusting the flow rate of the EGR gas are provided.

  Incidentally, the engine 1 of the present embodiment includes a first cylinder group A and a second cylinder group B formed by dividing all four cylinders into two cylinders. That is, the # 1 to # 4 cylinders of the engine 1 are divided into a first cylinder group A including # 1 and # 2 cylinders and a second cylinder group B including # 3 and # 4 cylinders.

  The intake manifold 10 is common to the first cylinder group A and the second cylinder group B, but the exhaust manifold 20 is formed substantially separately and independently. In the case of the present embodiment, the exhaust manifold 20 is substantially divided into two by a partition 35 inside thereof into a first exhaust manifold 20A for the first cylinder group A and a second exhaust manifold 20B for the second cylinder group B. ing. The partition wall 35 extends to the inlet of the turbine 14T. Therefore, the exhaust manifold 20 is divided into two parts up to the inlet of the turbine 14T.

  The upstream end of the EGR passage 31 is connected to the second exhaust manifold 20 </ b> B so that only the exhaust gas from the second cylinder group B is recirculated to the intake manifold 10. However, the partition 35 may be omitted and the exhaust manifold 20 may not be divided, and the upstream end of the EGR passage 31 may be connected to the position of the exhaust manifold 20 closer to the second cylinder group B than the first cylinder group A. . For example, as shown in the figure, the upstream end of the EGR passage 31 may be connected to the position of the exhaust manifold 20 farthest from the first cylinder group A in the cylinder row direction. Also by doing so, the exhaust gas from the second cylinder group B can be recirculated to the intake manifold 10 more positively and in a larger amount than the exhaust gas from the first cylinder group A, and the same effect can be achieved. . The advantages of doing this will be explained later.

  In addition, the exhaust purification apparatus of the present embodiment is provided in the first cylinder group A, and is a variable valve mechanism for changing the operating characteristics of the intake valves of the first cylinder group A, that is, the first variable valve mechanism 36A. Is provided. Further, the exhaust purification apparatus of the present embodiment is provided with a variable valve mechanism that is provided in the second cylinder group B and makes the operation characteristics of the intake valves of the second cylinder group B variable, that is, a second variable valve mechanism 36B. Also equipped. Here, the “operation characteristic” includes at least one of lift, operation angle (valve opening period), and valve timing (opening and closing timing). These first and second variable valve mechanisms 36A and 36B can be of any structure including a known structure. In this embodiment, as shown in FIG. 2, the lift and operating angle of the intake valve are simultaneously controlled. It is designed to be variable. This operating characteristic will be described in detail later. The first and second variable valve mechanisms 36A and 36B are controlled independently of each other. In FIG. 2, the horizontal axis represents the crank angle θ, and the vertical axis represents the lift L of the intake valve.

  In addition, the exhaust purification device of this embodiment includes an electronically controlled exhaust throttle valve 37 and an exhaust injector 38 provided in the exhaust passage 4. In the present embodiment, these are provided in the exhaust passage 4 between the turbine 14 </ b> T and the oxidation catalyst 22, and an exhaust injector 38 is disposed downstream of the exhaust throttle valve 37. However, these installation positions can be changed. The exhaust injector 38 is an injector for injecting fuel into the exhaust passage 4.

  A control device for controlling the engine 1 is mounted on the vehicle. The control device has an electronic control unit (referred to as ECU) 100 that forms a control unit or a controller. ECU 100 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like. The ECU 100 controls the in-cylinder injector 7, the intake throttle valve 16, the addition valve 25, the EGR valve 33, the first variable valve mechanism 36A, the second variable valve mechanism 36B, the exhaust throttle valve 37, and the exhaust injector 38. Configured and programmed.

  The control device also has the following sensors. Regarding these sensors, in addition to the air flow meter 13 described above, a rotational speed sensor 40 for detecting the rotational speed of the engine, specifically a rotational speed per minute (rpm), and an accelerator opening degree are detected. An accelerator opening sensor 41 is provided. Further, exhaust temperature sensors 42, 43, 44, and 46 are provided for detecting exhaust temperatures (inlet gas temperatures) at the inlets of the oxidation catalyst 22, the filter 23, the NOx catalyst 24, and the ammonia oxidation catalyst 26, respectively. . Further, a differential pressure sensor 45 for detecting a differential pressure between the exhaust pressure at the inlet and the outlet of the filter 23 is provided. Further, a manual regeneration switch 47 that is manually operated by the driver is provided. Output signals from these sensors are sent to the ECU 100.

  As will be understood later, at least one of the exhaust temperature sensors 42, 43, 44, 46 and the ECU 100 constitute a temperature detection unit as defined in the claims. Further, the differential pressure sensor 45 and the ECU 100 constitute a deposit amount detection unit referred to in the claims.

  Next, the control of this embodiment will be described. For simplification, it is assumed that the intake throttle valve 16 and the exhaust throttle valve 37 are controlled to be fully opened.

  In general, the ECU 100 is configured to execute three control modes of a first control mode α, a second control mode β, and a third control mode γ, and to control each part of the engine according to these control modes.

  Here, although common to these three control modes, the ECU 100 is based on the engine speed Ne and the accelerator opening Ac detected by the rotation speed sensor 40 and the accelerator opening sensor 41, respectively, in FIG. According to the fuel injection amount map as shown, the fuel injection amount, in particular, the target fuel injection amount Q as the instruction injection amount to the injector 7 is calculated. The fuel injection amount map is set in advance through a test or the like and stored in the ECU 100. The same applies to the map described later. The target fuel injection amount Q is a parameter representing the engine load. For this parameter, any parameter other than the target fuel injection amount Q such as the accelerator opening can be adopted.

  Next, the ECU 100 determines which region the engine operating state is defined by the engine speed Ne and the target fuel injection amount Q in accordance with a region determination map as shown in FIG. In the present embodiment, the entire operation region of the engine is divided into a first region R1 that is at least one of the high rotation side and the high load side, and a second region R2 that is lower in rotation than the first region R1 and on the low load side. It is divided. If the detected engine speed Ne and the target fuel injection amount Q are in the first region R1 on the region determination map, the ECU 100 determines that the engine operating state is in the first region R1, and these are in the second region R2. If it is, it is determined that the engine operating state is in the second region R2.

  In the present embodiment, a region where the engine speed Ne is equal to or less than a predetermined boundary rotation threshold value N1 and the target fuel injection amount Q is equal to or less than the boundary injection amount threshold value Q1 is defined as the second region R2, and the remaining region is defined as the first region R1. It stipulates. In the present embodiment, the boundary rotation threshold N1 is the engine rotation that defines the boundary between the medium speed range and the high speed range when the entire range of the engine speed Ne is roughly divided into the low speed range, the medium speed range, and the high speed range. It is set equal to the number. The boundary injection amount threshold value Q1 defines the boundary when the entire range of the target fuel injection amount Q is roughly divided into two parts, the low load side (small injection amount side) and the high load side (large injection amount side). The target fuel injection amount is set. Therefore, the second region R2 can be said to be a low / medium speed and low load region of the engine. However, other specific methods for setting the regions R1 and R2 are possible.

  The ECU 100 executes the first control mode α when the engine operating state is in the first region R1. At this time, the ECU 100 operates the first cylinder group A and the second cylinder group B and causes the engine 1 to operate in all cylinders as in a normal engine. Then, an amount of fuel equal to the target fuel injection amount Q obtained from the fuel injection amount map shown in FIG. 4A is injected from the injectors 7 of all cylinders.

  The ECU 100 also controls the first and second variable valve mechanisms 36A, 36B so that the intake valves of the first cylinder group A have the same operating characteristics as the intake valves of the second cylinder group B. Specifically, as shown in FIG. 2, the ECU 100 controls the second variable valve mechanism 36B so that the intake valves of the second cylinder group B operate according to the lift diagram L1 that provides the maximum valve lift and the maximum operating angle. To control. The ECU 100 also controls the first variable valve mechanism 36A so that the intake valves of the first cylinder group A operate according to the same lift diagram L1. As a result, a sufficient intake air amount can be secured in the first region R1, which is a high rotation and / or high load region, and a desired engine output can be achieved.

  Next, when the engine operating state is in the second region R2, the ECU 100 selects and executes one of the first control mode α, the second control mode β, and the third control mode γ. In other words, the second region R2 is a region in which either the second control mode β or the third control mode γ can be executed. The second control mode β is a control mode that is more advantageous for raising the exhaust temperature than the first control mode α, and the third control mode γ is a control mode that is more advantageous for raising the exhaust temperature than the second control mode β.

  Selection or switching of these control modes is performed mainly based on the exhaust temperature at a predetermined position of the exhaust passage 4. Here, the predetermined position can be any of the installation positions of the exhaust temperature sensors 42, 43, 44, 46.

  The main object of the present embodiment is to reduce the amount of PM deposited on the filter 23 while suppressing the fuel consumption as much as possible, that is, to promote filter regeneration. For this reason, the predetermined position is set as the installation position of the exhaust temperature sensor 43 at the inlet of the filter 23, and the control mode is switched based on the exhaust temperature Tb detected by the exhaust temperature sensor 43.

  However, the predetermined position can be arbitrarily changed according to the main purpose of temperature increase. For example, when the main purpose is to raise the temperature of the NOx catalyst 24, the predetermined position is set as the installation position of the exhaust temperature sensor 44 at the inlet of the NOx catalyst 24, and based on the exhaust temperature Tc detected by the exhaust temperature sensor 44. The control mode may be switched.

  Here, filter regeneration will be described. In this embodiment, for convenience, filter regeneration that is performed without supplying additional fuel for increasing the temperature of exhaust gas is referred to as passive regeneration, and filter regeneration that is performed while supplying additional fuel for increasing the temperature of exhaust gas is referred to as active regeneration. The active regeneration is classified into manual regeneration that is forcibly executed when the manual regeneration switch 47 is turned on and automatic regeneration that is automatically performed when the manual regeneration switch 47 is not turned on. Manual regeneration is generally performed while the vehicle is idle.

  Passive regeneration is executed in the first control mode α and the second control mode β. At this time, as will be understood later, since the exhaust gas discharged from the cylinder is relatively hot, supplying the exhaust gas to the filter 23 raises the temperature of the filter 23 and promotes the combustion of the deposited PM. Can do. On the other hand, active regeneration is executed in the third control mode γ. When the additional fuel for raising the temperature of the exhaust gas is supplied, the additional fuel is combusted by the oxidation catalyst 22, and the exhaust gas whose temperature has been raised is discharged from the oxidation catalyst 22. By supplying this exhaust gas to the filter 23, the temperature of the filter 23 can be raised and combustion of the deposited PM can be promoted.

  Note that if the exhaust temperature at the inlet of the filter 23 increases, the exhaust temperature at the inlet of the NOx catalyst 24 inevitably increases. The former and latter exhaust temperatures can be regarded as almost the same or have a correlation with each other. Therefore, the temperature increase of the filter 23 is necessarily accompanied by the temperature increase of the NOx catalyst 24, and the activity of the NOx catalyst 24 is increased.

  When the third control mode γ is executed when the manual regeneration switch 47 is off and the following conditions are satisfied, the filter 23 is automatically regenerated. On the other hand, when the manual regeneration switch 47 is on, the third control mode γ is executed regardless of whether or not each condition described later is satisfied, and the filter 23 is manually regenerated. In the following description, for the sake of easy understanding, only automatic regeneration is basically described, and manual regeneration is not touched.

  Now, when executing the second control mode β, the ECU 100 deactivates the engine 1 by deactivating the first cylinder group A and operating the second cylinder group B. At this time, for the first cylinder group A, the fuel injection from the injector 7 is stopped. For the second cylinder group B, the fuel injection amount from the injector 7 is determined from the fuel injection amount map shown in FIG. 4 (A) so that an output equivalent to that during all cylinder operation can be secured. Than to increase. Specifically, the target fuel increased from the other fuel injection amount map (referred to as the reduced cylinder operating cylinder fuel injection amount map) as shown in FIG. 4C under the same rotation speed and accelerator opening conditions. An injection amount QB is obtained, and an amount of fuel equal to the target fuel injection amount QB is injected from the injector 7 of the second cylinder group B.

  Further, the ECU 100 controls the first and second variable valve mechanisms 36A, 36B so that the charging efficiency of the first cylinder group A is smaller than the charging efficiency of the second cylinder group B. Here, the charging efficiency refers to the ratio of the actual intake air amount to the maximum intake air amount per cylinder. In the present embodiment, as shown in FIG. 2, the ECU 100 performs the second operation so that the intake valves of the second cylinder group B operate according to a lift diagram L2 having a slightly smaller lift and a smaller operating angle than the lift diagram L1. The variable valve mechanism 36B is controlled. Further, the ECU 100 controls the first variable valve mechanism 36A so that the intake valves of the first cylinder group A operate according to a lift diagram L3 having a smaller lift and a smaller operating angle with respect to the lift diagram L2.

  In the present embodiment, the lift diagram L3 is set so that the filling efficiency with respect to the lift diagram L1 is a predetermined ratio or less, for example, 50% or less. The lift diagram L2 is set so that the filling efficiency with respect to the lift diagram L1 is greater than 50% and less than 100%. The lift diagram L3 shown is for the case where the filling efficiency is 50%, but as shown by L3 ′ and L3 ″, this can be changed as appropriate within the range of greater than 0% and less than 50%. In addition, the lift diagram L2 can be appropriately changed within a range of more than 50% and less than 100%, as indicated by L2 ′, for example, and 50% seems to be preferable empirically or experimentally. It is an example of the value, and is not intended to be limited to this value.

  Alternatively, the intake valves of the second cylinder group B may be operated according to the same lift diagram L1 as in the first control mode α. In this case, the second variable valve mechanism 36B can be omitted. However, as in this embodiment, it is preferable to operate according to the lift diagram L2 on the charging efficiency lower side than in the first control mode α. That is, since the second control mode β is executed in the second region R2 on the lower rotation side and the lower load side than in the first control mode α, the operation according to the lift diagram L2 is more suitable for the second region R2. It is because it can optimize so that it may become the filling efficiency. Therefore, the lift diagram L2 of the present embodiment is set to a lift diagram that optimizes the filling efficiency for the second region R2.

  In this way, when the second control mode β is executed, the engine 1 is operated in a reduced cylinder operation, and the intake air flow rate is reduced in the first cylinder group A on the inactive side and the second cylinder group B on the operating side as compared to that in the all cylinder operation. The In the reduced-cylinder operation, the pumping loss is smaller than the opening reductions of the exhaust throttle valve 37 and the intake throttle valve 16. This leads to suppression of fuel consumption deterioration, in other words, it is advantageous in terms of fuel consumption. In addition, a decrease in the exhaust gas temperature is suppressed by reducing the flow rate of the relatively low temperature intake air. As a result, compared with the case of all cylinder operation, high-temperature exhaust gas can be supplied to the oxidation catalyst 22 and thus to the filter 23 and the NOx catalyst 24, and the temperature of the filter 23 and the NOx catalyst 24 can be further increased. For this reason, it is possible to raise the temperature of the exhaust gas and the filter 23 and the NOx catalyst 24 while suppressing deterioration in fuel consumption. Further, passive regeneration of the filter 23 can be promoted, and an increase in the activity of the NOx catalyst 24 can be promoted.

  Alternatively, even when the intake valves of the second cylinder group B are operated according to the same lift diagram L1 as in the first control mode α, the pumping loss is reduced and the intake air flow rate is reduced, although not as in the present embodiment. Can be reduced. Therefore, the same effect as this embodiment can be exhibited.

  Next, the third control mode γ will be described. When executing the third control mode γ, the ECU 100 pauses the first cylinder group A and activates the second cylinder group B to cause the engine 1 to perform a reduced cylinder operation, as in the second control mode β. Further, as in the second control mode β, the ECU 100 controls the first and second variable valve mechanisms 36A and 36B so that the charging efficiency of the first cylinder group A is smaller than the charging efficiency of the second cylinder group B. To do.

  In addition to this, the ECU 100 supplies fuel to the first cylinder group A, which is a deactivated cylinder, in a manner that does not cause in-cylinder combustion. Like the conventional post-injection fuel, this fuel does not contribute to engine output because it does not burn in the cylinder, and is used for raising the temperature of the exhaust gas and the post-processing member.

  Specifically, the ECU 100 causes the injector 7 of the first cylinder group A to inject an amount of fuel smaller than the maximum value of the target fuel injection amount Q in the fuel injection amount map shown in FIG. Specifically, a target fuel injection amount QA is obtained from another fuel injection amount map (referred to as a cylinder reduction fuel injection amount map at the time of reduced cylinders) as shown in FIG. 4D, and is equal to the target fuel injection amount QA. An amount of fuel is injected from the injectors 7 of the first cylinder group A.

  The target fuel injection amount QA of the inactive first cylinder group A obtained from the map of FIG. 4D is smaller than the maximum value of the target fuel injection amount Q shown in the map of FIG. However, it is preferably 75% or less of the maximum value of the target fuel injection amount Q.

  In the present embodiment, the ECU 100 executes retarding (retarding) of the fuel injection timing in addition to the reduction of the fuel injection amount in the first cylinder group A on the stop side, although it is optional.

  FIG. 3A shows an example of the fuel injection timing of the inactive first cylinder group A when the third control mode γ is executed. FIG. 3B shows an example of the fuel injection timing of the operating side second cylinder group B when the third control mode γ is executed. Note that θ is a crank angle, TDC is a compression top dead center, and a hatched region represents a period during which fuel injection is performed, specifically, an energization time of the injector 7.

  As shown in FIG. 3 (B), in the second cylinder group B, the main injection MI is executed immediately after a small amount of pilot injection PI, and the fuel injection timing of the main injection MI (herein, the injection start timing) is compressed. It is set near the top dead center TDC, more specifically, immediately before the compression top dead center TDC. The fuel injection timing of the main injection MI is not limited to the timing shown in the figure, and can be arbitrarily set, for example, within a range of ± 20 ° CA of the compression top dead center TDC.

  On the other hand, as shown in FIG. 3A, in the first cylinder group A, the pilot injection PI is omitted and only the main injection MI is executed. The fuel injection timing of the main injection MI is the second cylinder group. The fuel injection timing of the B main injection MI is delayed by a predetermined crank angle Δθ. However, the fuel injection timing of the main injection MI is set to a timing that is remarkably advanced as compared with the conventional post injection. In the illustrated example, the fuel injection timing of the main injection MI is set immediately before and immediately before the compression top dead center TDC, but it may be set at a timing later than this.

  Fuel injection in such an idle cylinder that does not perform in-cylinder combustion is more advantageous than conventional post-injection. That is, in the case of post injection, the post fuel is injected at a considerably late timing after the combustion of the main fuel, which causes a problem of oil dilution (dilution) with the post fuel. However, in the case of the present embodiment, the temperature rise main fuel can be injected into the cylinder at the same timing (in the vicinity of compression top dead center TDC) as that of normal main injection, so that the problem of dilution can be solved. Further, since the pilot injection PI is omitted, in-cylinder combustion based on pilot fuel ignition can be reliably prevented.

  Further, in the present embodiment, in the first cylinder group A, the charging efficiency is lowered with respect to the second cylinder group B to lower the compression end temperature, and then the fuel injection amount is reduced. Thereby, in-cylinder combustion can be reliably prevented. In addition, in this embodiment, the fuel injection timing is retarded, so that in-cylinder combustion can be prevented more reliably. Therefore, the unburned fuel discharged from the first cylinder group A can be efficiently combusted in the oxidation catalyst 22, and the exhaust gas and the post-processing member can be efficiently heated.

  Further, the third control mode γ of the present embodiment can also suppress the deterioration of the fuel consumption as in the second control mode β. Therefore, it is possible to effectively suppress fuel consumption deterioration when the exhaust gas and the post-processing member are heated.

  In particular, in the third control mode γ, the intake air flow rate and hence the exhaust flow rate are significantly reduced by the reduced cylinder operation, so that the heat capacity of the exhaust gas is greatly reduced. Therefore, the temperature raising fuel discharged from the first cylinder group A can be effectively used for raising the temperature of the post-processing member rather than raising the temperature of the exhaust gas. Therefore, it is possible to significantly reduce the amount of fuel consumption required for raising the temperature as compared with the conventional post injection.

  In the present embodiment, the exhaust manifold 20 is divided, and the upstream end of the EGR passage 31 is connected only to the second exhaust manifold 20B and not connected to the first exhaust manifold 20A. Therefore, it is possible to reliably suppress the unburned fuel discharged from the first cylinder group A from flowing into the EGR passage 31 and fouling the EGR cooler 32 and the like.

  Even if the exhaust manifold 20 is not divided, the upstream end of the EGR passage 31 is connected to the position of the exhaust manifold 20 closer to the second cylinder group B than to the first cylinder group A (for example, the position shown in FIG. 1). Even in this case, it is possible to suppress the unburned fuel discharged from the first cylinder group A from actively flowing into the EGR passage 31 and to suppress the contamination of the EGR cooler 32 and the like.

  Note that the conventional method of reducing the opening degree of the exhaust throttle valve or the intake throttle valve at the time of temperature rise may cause the intake / exhaust pressure difference to fluctuate greatly and increase the difficulty of EGR control. The three control mode γ can also solve such a problem.

  In the third control mode γ of the present embodiment, in addition to the in-cylinder fuel injection in the first cylinder group A described above, fuel injection by the exhaust injector 38, that is, exhaust pipe injection may be performed.

  As described above, when the engine operating state is in the second region R2, the ECU 100 sets the control mode to the first control mode α and the second control mode according to the exhaust temperature Tb detected by the exhaust temperature sensor 43. Switch to either β or the third control mode γ. The switching threshold at this time is shown in FIG.

  ECU 100 stores in advance temperature threshold values T1, T2, T3 (T1 <T2 <T3) as shown in FIG. T1 is set to an arbitrary value within the range of 200 to 250 ° C. (for example, 250 ° C.), T2 is set to an arbitrary value within the range of 250 to 300 ° C. (for example, 300 ° C.), T3 is set to an arbitrary value within the range of 400 to 500 ° C. (for example, 500 ° C.). T2 corresponds to the “first temperature threshold” in the claims, T1 corresponds to the “second temperature threshold” in the claims, and T3 corresponds to the “third temperature threshold” in the claims. Is equivalent to.

  In the present embodiment, T1 is set to be approximately equal to the activation start temperature (minimum temperature at which they are activated) of at least one of the filter 23 (particularly its catalyst component) and the NOx catalyst 24. T2 is set to be approximately equal to the minimum temperature at which the NOx purification rate of the NOx catalyst 24 becomes a practically sufficient level. T3 is set to be approximately equal to the minimum temperature at which the PM deposited on the filter 23 is actively burned and the rate of decrease of the deposited PM is at an acceptable level.

  The ECU 100 separately detects or estimates the PM accumulation amount M in the filter 23 based on the differential pressure detected by the differential pressure sensor 45, and whether the detected PM accumulation amount M is equal to or greater than a predetermined accumulation amount threshold M2. The control mode switching method is changed according to the above. The accumulation amount threshold value M2 is set equal to a value close to the maximum PM accumulation amount (that is, the filter capacity) that can be accumulated in the filter 23, for example, 90% of the maximum PM accumulation amount. The accumulation amount threshold value M2 corresponds to a “deposition amount threshold value” in the claims.

  When the PM accumulation amount M is less than the accumulation amount threshold M2, the ECU 100 executes the first control mode α when the detected exhaust temperature Tb is higher than T2, and performs the second control when the detected exhaust temperature Tb is equal to or lower than T2 and higher than T1. The mode β is executed, and the third control mode γ is executed when the detected exhaust gas temperature Tb is equal to or lower than T1.

  When the PM deposition amount M is less than the deposition amount threshold M2, it is considered that the PM deposition amount M is not so large as to require filter regeneration immediately. Therefore, in this case, supply of additional fuel is suppressed as much as possible, and filter regeneration by passive regeneration is performed as much as possible.

  When the detected exhaust gas temperature Tb is higher than T2, the exhaust gas temperature is sufficiently high. Therefore, the entire engine is operated as usual in the first control mode α, and filter regeneration by passive regeneration is executed. Further, when the detected exhaust gas temperature Tb is equal to or lower than T2 and higher than T1, the exhaust gas temperature is still relatively high. Therefore, the second control mode β is executed, and filter regeneration by passive regeneration is performed.

  When the detected exhaust gas temperature Tb is equal to or lower than T1, there is a possibility that the engine is operated at a low rotation and a low load including idle, and there is a possibility that the filter 23 and the NOx catalyst 24 become inactive. For this reason, it is necessary to raise those temperatures immediately. Therefore, the third control mode γ is executed, the temperature raising fuel is supplied from the first cylinder group A, the hot exhaust gas is supplied to the filter 23 and the NOx catalyst 24, and the filter regeneration by active regeneration, particularly automatic regeneration is performed. Then, the activities of the filter 23 and the NOx catalyst 24 are rapidly increased.

  As described above, the active regeneration is executed only when the detected exhaust gas temperature Tb is equal to or lower than T1, so that the frequency of execution of the active regeneration can be minimized. As a result, the frequency of passive regeneration can be increased, and as a result, the fuel consumption required for filter regeneration can be reduced. And since the frequency of manual regeneration can also be reduced, usability can be improved.

  On the other hand, when the PM accumulation amount M is equal to or greater than the accumulation amount threshold M2, the ECU 100 executes the first control mode α when the detected exhaust temperature Tb is higher than T3, and the third control mode γ when the detected exhaust temperature Tb is equal to or lower than T3. Is configured to run.

  When the PM deposition amount M is equal to or greater than the deposition amount threshold M2, it is considered that the PM deposition amount M is so large that filter regeneration is required immediately. Therefore, when the detected exhaust gas temperature Tb is equal to or lower than T3, the third control mode γ is executed, the additional fuel is actively supplied, and the filter regeneration by active regeneration is performed.

  However, when the detected exhaust gas temperature Tb is higher than T3, the exhaust gas temperature is very high, and it is considered that a PM deposition amount decrease rate of a certain level or more can be obtained without supplying additional fuel. Therefore, the engine is operated as usual in the first control mode α, and filter regeneration by passive regeneration is executed. Thus, filter regeneration can be performed without supplying additional fuel, and fuel consumption associated with filter regeneration can be suppressed.

  When the detected exhaust gas temperature Tb is equal to or lower than T3, the target fuel injection amount of the first cylinder group A is increased by a predetermined amount within the range in which in-cylinder combustion does not occur than the target fuel injection amount QA obtained from the map of FIG. May be. As a result, the PM deposition amount can be reduced more rapidly than in the case of M <M2.

  FIG. 4F shows a map stored in advance in ECU 100 for realizing such control mode switching method change. The horizontal axis of this map is the PM accumulation amount M, and the vertical axis is the exhaust gas temperature T. The ECU 100 switches the control mode based on the PM accumulation amount M and the detected exhaust gas temperature Tb according to the mode switching map.

  In particular, as shown by the thick solid line, when the PM accumulation amount M is equal to or greater than the accumulation amount threshold M2, the temperature threshold T3 is selected, and the first control mode α and the third control mode γ are described above with the temperature threshold T3 as a boundary. Are switched as follows. On the other hand, when the PM accumulation amount M is less than the accumulation amount threshold M2, the temperature threshold T1 is selected, and the second control mode β and the third control mode γ are switched as described above with the temperature threshold T1 as a boundary. Thus, the thick solid line in the map is a line that represents the boundary temperature threshold value for switching between the third control mode γ and another adjacent control mode α or β. Although another accumulation amount threshold value M1 (<M2) is also shown, this is set to a maximum value of a small amount of PM accumulation amount that does not require the regeneration of the filter, for example, the maximum PM accumulation amount of the filter 23 Is set equal to a value of 10%.

  Next, a control routine in the present embodiment will be described with reference to FIG. The illustrated routine is repeatedly executed by the ECU 100 at every predetermined calculation cycle τ (for example, 10 msec).

  First, in step S101, the ECU 100 acquires the engine speed Ne, the accelerator opening Ac, and the differential pressure ΔP detected by the rotation speed sensor 40, the accelerator opening sensor 41, and the differential pressure sensor 45, respectively.

  Next, in step S102, the ECU 100 calculates a target fuel injection amount Q corresponding to the acquired engine speed Ne and accelerator opening degree Ac from the target fuel injection amount map shown in FIG. Further, the ECU 100 calculates or estimates the PM accumulation amount M of the filter 23 corresponding to the acquired differential pressure ΔP from an accumulation map (not shown).

  Next, in step S103, the ECU 100 determines that the current engine operating state is in the second region according to the region determination map shown in FIG. 4B based on the acquired engine speed Ne and the calculated target fuel injection amount Q. It is determined whether it is within R2.

  If the ECU 100 determines that it is not within the second region R2 (ie, if it is determined that it is within the first region R1), the ECU 100 proceeds to step S110 to select and execute the first control mode α.

  On the other hand, if the ECU 100 determines that it is within the second region R2, the ECU 100 proceeds to step S104, and determines whether or not the calculated PM accumulation amount M is equal to or greater than the accumulation amount threshold M2.

  When the ECU 100 determines that the PM accumulation amount M is less than the accumulation amount threshold M2, the ECU 100 proceeds to step S105 and determines whether or not the exhaust temperature Tb detected by the exhaust temperature sensor 43 is equal to or lower than the temperature threshold T2.

  When the ECU 100 determines that the exhaust temperature Tb is equal to or lower than the temperature threshold T2, the ECU 100 proceeds to step S106, and determines whether the exhaust temperature Tb is equal to or lower than the temperature threshold T1.

  When the ECU 100 determines that the exhaust temperature Tb is not equal to or lower than the temperature threshold T1 (higher than the temperature threshold T1), the ECU 100 proceeds to step S107 and selects and executes the second control mode β.

  On the other hand, if the ECU 100 determines that the exhaust temperature Tb is equal to or lower than the temperature threshold T1, the ECU 100 proceeds to step S109, and selects and executes the third control mode γ.

  On the other hand, if the ECU 100 determines in step S105 that the exhaust gas temperature Tb is higher than the temperature threshold value T2, the ECU 100 proceeds to step S110, and selects and executes the first control mode α.

  On the other hand, if the ECU 100 determines in step S104 that the PM accumulation amount M is equal to or greater than the accumulation amount threshold M2, the ECU 100 proceeds to step S108 and determines whether the exhaust temperature Tb detected by the exhaust temperature sensor 43 is equal to or less than the temperature threshold T3.

  When the ECU 100 determines that the exhaust temperature Tb is equal to or lower than the temperature threshold T3, the ECU 100 proceeds to step S109, and selects and executes the third control mode γ.

  On the other hand, if the ECU 100 determines that the exhaust temperature Tb is not equal to or lower than the temperature threshold T3 (higher than the temperature threshold T3), the ECU 100 proceeds to step S110 and selects and executes the first control mode α.

  Thus, according to the present embodiment, when the engine operating state is in the second region R2 (step S103: YES), when the exhaust temperature Tb is low (when M <M2, when Tb ≦ T1, when M ≧ M2) (Sometimes when Tb ≦ T3), the third control mode γ with additional fuel supply is executed. Therefore, the frequency of active regeneration is reduced and the frequency of passive regeneration is increased, while suppressing deterioration of fuel consumption and exhaust gas. In addition, the temperature of the post-processing member can be effectively increased.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected in the figure to the part similar to the said 1st Embodiment, and description is omitted, and the difference from 1st Embodiment is mainly demonstrated below.

  The present embodiment is mainly different from the first embodiment in that the control mode is switched depending on which region the engine operating state belongs to more simply.

  FIG. 6A and FIG. 6B show region determination maps used in the present embodiment. These two area determination maps are stored in the ECU 100 in advance. The first region determination map shown in FIG. 6A is used when the PM accumulation amount M is less than the accumulation amount threshold M2 (M <M2). The second region determination map shown in FIG. 6B is used when the PM accumulation amount M is equal to or greater than the accumulation amount threshold M2 (M ≧ M2).

  In the first region determination map of FIG. 6A, the entire operation region of the engine includes a first region R1 that is at least one of the high rotation side and the high load side, and a lower rotation and lower load side than the first region R1. Are divided into a second region R2 and a third region R3 having a lower rotation and a lower load than the second region R2.

  The ECU 100 executes the first control mode α when the engine operating state defined by the engine speed Ne and the target fuel injection amount Q is in the first region R1, and when the engine operating state is in the second region R2. When the second control mode β is executed and the engine operating state is in the third region R3, the third control mode γ is executed.

  On the other hand, in the second region determination map of FIG. 6B, the entire operation region of the engine is the first region R1 that is at least one of the high rotation side and the high load side, and is lower in rotation and lower than the first region R1. It is divided into a load-side fourth region R4. The fourth region R4 is a region different from the second region R2 and the third region R3.

  The ECU 100 is configured to execute the first control mode α when the engine operating state is in the first region R1, and to execute the third control mode γ when the engine operating state is in the fourth region R4. .

  In the first region determination map of FIG. 6A, the rotation threshold value that defines the boundary between the first region R1 and the second region R2 is N1 as in the map of FIG. 4B, and the injection amount threshold value is Q3. It is. In particular, the injection amount threshold value Q3 is generally set to a target fuel injection amount value such that the exhaust temperature Tb becomes equal to the temperature threshold value T2 during all-cylinder operation. The rotation threshold value that defines the boundary between the second region R2 and the third region R3 is N2 smaller than N1, and the injection amount threshold value is Q2 smaller than Q3. In particular, the injection amount threshold value Q2 is generally set to a target fuel injection amount value such that the exhaust temperature Tb becomes equal to the temperature threshold value T1 during the reduced-cylinder operation. Thus, the injection amount threshold values Q3 and Q2 are values corresponding respectively to the temperature threshold values T2 and T1 of the first embodiment.

  On the other hand, in the second region determination map of FIG. 6B, the rotation threshold value that defines the boundary between the first region R1 and the fourth region R4 is N1 as described above, and the injection amount threshold value is Q4 that is larger than Q3. . In particular, the injection amount threshold value Q4 is generally set to a target fuel injection amount value such that the exhaust temperature Tb becomes equal to the temperature threshold value T3 during all-cylinder operation. Therefore, the injection amount threshold value Q4 is a value corresponding to the temperature threshold value T3 of the first embodiment.

  With reference to FIG. 7, the control routine in this embodiment is demonstrated.

  Steps S201, S202, S206, S208, and S209 of this embodiment are the same as steps S101, S102, S107, S109, and S110 of the first embodiment shown in FIG.

  In step S203, the ECU 100 determines whether the PM accumulation amount M calculated in step S202 is equal to or greater than the accumulation amount threshold M2.

  When the ECU 100 determines that the PM accumulation amount M is less than the accumulation amount threshold M2, the ECU 100 proceeds to step S204, and based on the engine speed Ne and the target fuel injection amount Q, the first region determination map shown in FIG. Accordingly, it is determined whether or not the current engine operating state is in the first region R1.

  If the ECU 100 determines that it is in the first region R1, the ECU 100 proceeds to step S209, and selects and executes the first control mode α.

  On the other hand, if ECU 100 determines that it is not within first region R1, the process proceeds to step S205, and whether the current engine operating state is within second region R2 according to the first region determination map shown in FIG. Judge whether or not.

  If the ECU 100 determines that it is in the second region R2, the process proceeds to step S206, and selects and executes the second control mode β.

  On the other hand, if ECU 100 determines that it is not within second region R2 (ie, if it is determined that it is within third region R3), it proceeds to step S208 to select and execute third control mode γ.

  On the other hand, if the ECU 100 determines in step S203 that the PM accumulation amount M is greater than or equal to the accumulation amount threshold value M2, the ECU 100 proceeds to step S207, and based on the engine speed Ne and the target fuel injection amount Q, the ECU 100 shown in FIG. In accordance with the two-region determination map, it is determined whether or not the current engine operating state is in the first region R1.

  If the ECU 100 determines that it is in the first region R1, the ECU 100 proceeds to step S209, and selects and executes the first control mode α.

  On the other hand, if ECU 100 determines that it is not within first region R1 (ie, if it is determined that it is within fourth region R4), it proceeds to step S208 to select and execute the third control mode γ.

  As described above, according to the present embodiment, the control mode is switched only by which region the engine operating state is in, so that the control can be simplified. It should be noted that other features of the first embodiment not mentioned here can be included in the present embodiment, and thus the present embodiment can exhibit the same operational effects as the first embodiment.

  As mentioned above, although embodiment of this invention was described in detail, this invention can be implemented also by other embodiment.

  (1) For example, a method other than the above-described embodiment can be used for dividing the cylinder group. For example, in a 6-cylinder engine, it is possible to provide first and second cylinder groups divided into three cylinders. It is not always necessary to equally divide all cylinders. For convenience, the “cylinder group” includes a cylinder group including only one cylinder. In other words, one cylinder group includes one or more cylinders.

  (2) An embodiment in which the third control mode γ and its related parts are omitted from the above-described embodiment is also possible. That is, the second control mode β may be executed in the portion where the third control mode γ of the above-described embodiment is executed.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 Internal combustion engine
4 exhaust passage 20A first exhaust manifold 20B second exhaust manifold 22 oxidation catalyst 23 filter 24 NOx catalyst 31 EGR passage 36A first variable valve mechanism 36B second variable valve mechanism 42, 43, 44, 46 exhaust temperature sensor 100 electron Control unit (ECU)
A 1st cylinder group B 2nd cylinder group

Claims (10)

An exhaust emission control device for an internal combustion engine having a first cylinder group and a second cylinder group formed by dividing a plurality of cylinders,
A first variable valve mechanism for varying the operating characteristics of the intake valves of the first cylinder group;
An oxidation catalyst provided in the exhaust passage;
A post-processing member provided downstream of the oxidation catalyst in the exhaust passage;
A control unit configured to control operating states of the first cylinder group and the second cylinder group and the first variable valve mechanism;
With
The control unit is
When the operating state of the internal combustion engine is in a predetermined first region, the first cylinder group and the second cylinder group are operated to operate all cylinders of the internal combustion engine, and the intake valve of the first cylinder group is Executing a first control mode for controlling the first variable valve mechanism so as to have the same operating characteristics as the intake valves of the second cylinder group;
When the operating state of the internal combustion engine is in a predetermined second region at a lower speed and a lower load side than the first region, the first cylinder group is deactivated and the second cylinder group is operated to operate the internal combustion engine. And the second control mode for controlling the first variable valve mechanism is executed so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. An exhaust emission control device for an internal combustion engine, characterized by comprising: The exhaust purification device further includes a temperature detection unit for detecting an exhaust temperature at a predetermined position of the exhaust passage,
The control unit, when the operating state of the internal combustion engine is in the second region,
When the exhaust gas temperature detected by the temperature detector is lower than the first temperature threshold and higher than the second temperature threshold lower than the first temperature threshold, the second control mode is executed,
When the exhaust gas temperature detected by the temperature detector is equal to or lower than the second temperature threshold, the first cylinder group is deactivated and the second cylinder group is operated to reduce the internal combustion engine to perform the cylinder reduction operation. Third control for supplying the fuel in such a manner that the cylinder group is not burned in-cylinder and controlling the first variable valve mechanism so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. The exhaust emission control device for an internal combustion engine according to claim 1, configured to execute a mode. The post-processing member includes a filter for collecting particulate matter in the exhaust gas, and a NOx catalyst provided on the downstream side of the filter to purify NOx in the exhaust gas;
The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein the predetermined position is a position of an inlet portion of the filter or a position of an inlet portion of the NOx catalyst. The exhaust emission control device further includes a deposition amount detection unit for detecting a deposition amount of particulate matter in the filter,
The control unit is
When the operating state of the internal combustion engine is in the second region and the accumulation amount detected by the accumulation amount detection unit is less than a predetermined accumulation amount threshold, the exhaust temperature detected by the temperature detection unit is the first temperature. The second control mode is executed when the temperature is equal to or lower than a temperature threshold and is higher than the second temperature threshold, and the third control mode is executed when the exhaust temperature detected by the temperature detector is equal to or lower than the second temperature threshold. Item 6. An exhaust emission control device for an internal combustion engine according to Item 3. The control unit is
When the operating state of the internal combustion engine is in the second region and the accumulation amount detected by the accumulation amount detection unit is equal to or greater than the accumulation amount threshold, the exhaust temperature detected by the temperature detection unit is the first temperature. The third control mode is executed when the temperature is equal to or lower than a third temperature threshold value higher than the threshold value, and the first control mode is executed when the exhaust gas temperature detected by the temperature detection unit is higher than the third temperature threshold value. An exhaust gas purification apparatus for an internal combustion engine as described. The exhaust emission control device further includes a second variable valve mechanism for making the operation characteristic of the intake valve of the second cylinder group variable,
The control unit controls the second variable valve mechanism so that a charging efficiency of the second cylinder group is smaller than that in the execution of the first control mode when the second control mode and the third control mode are executed. The exhaust emission control device for an internal combustion engine according to any one of claims 2 to 5. The said control unit supplies the fuel of the quantity smaller than the fuel supplied at the time of execution of the said 1st control mode to the said 1st cylinder group at the time of execution of the said 3rd control mode. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1. The control unit supplies fuel to the first cylinder group at a timing delayed from a fuel supply timing to the second cylinder group when the third control mode is executed. The exhaust gas purification apparatus for an internal combustion engine according to the item. The internal combustion engine
A first exhaust manifold and a second exhaust manifold formed independently for the first cylinder group and the second cylinder group;
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 8, further comprising an EGR passage connected to the second exhaust manifold. An exhaust emission control device for an internal combustion engine having a first cylinder group and a second cylinder group formed by dividing a plurality of cylinders,
A first variable valve mechanism for varying the operating characteristics of the intake valves of the first cylinder group;
An oxidation catalyst provided in the exhaust passage;
A post-processing member provided downstream of the oxidation catalyst in the exhaust passage;
A control unit configured to control operating states of the first cylinder group and the second cylinder group and the first variable valve mechanism;
With
The control unit is
When the operating state of the internal combustion engine is in a predetermined first region, the first cylinder group and the second cylinder group are operated to cause the internal combustion engine to operate all cylinders, and the first cylinder group is the second cylinder. Executing a first control mode for controlling the first variable valve mechanism so as to have the same operating characteristics as the group;
When the operating state of the internal combustion engine is in a predetermined second region at a lower speed and a lower load side than the first region, the first cylinder group is deactivated and the second cylinder group is operated to operate the internal combustion engine. And the second control mode for controlling the first variable valve mechanism is executed so that the charging efficiency of the first cylinder group becomes smaller than the charging efficiency of the second cylinder group. An exhaust emission control device for an internal combustion engine, characterized by comprising:

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