JP2004197703A - Emission control apparatus of diesel engine and hybrid vehicle equipped with such engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emission control apparatus of a diesel engine capable of reduce PM and NOx to the SULEV level by efficiently burning and removing PM and efficiently trapping NOx through a NOx trapping catalyst, and a hybrid vehicle equipped with the emission control apparatus. <P>SOLUTION: The emission control apparatus is equipped with an oxidation catalyst 21 installed in the exhaust gas channel of the diesel engine 1 having a high oxidizing capacity of oxidizing NO in the exhaust gas into NO<SB>2</SB>at a first temperature or above; a filter 22 capable of catching PM from the exhaust gas and burning and removing the PM caught by the NO<SB>2</SB>produced through the oxidation catalyst 21; a NOx catalyst 23 capable of reducing and removing NOx in the exhaust gas; and an operation point setting means 30 for setting the operation point of the diesel engine so as to fix the exhaust gas temperature at or above the first temperature and to keep the PM content in the exhaust gas at or below a specified value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention removes harmful substances such as HC (Hydro Carbon), CO (Carbon Monoxide), NOx (Nitrogen Oxide), and PM (Exhaust Particulates: Particulate Matter) in exhaust gas by using SULEV (Super Ultra Low). The present invention relates to a diesel engine exhaust gas purification control device capable of purifying to an emission vehicle level or an atmospheric level, and a hybrid vehicle using the device.
[0002]
[Prior art]
In a hybrid vehicle including a diesel engine and a motor generator, when power is generated to obtain a required amount of power, an engine is operated in a region where the emission amounts of NOx and PM are equal to or less than the emission limit (Patent Document 1) 1).
[0003]
[Patent Document 1]
JP 2001-37008 A
[0004]
[Problems to be solved by the invention]
By the way, although the catalyst described in Patent Document 1 uses a catalyst, the catalyst alone cannot remove NOx and dry soot in PM. In addition, since a large amount of NOx and PM is emitted when the engine load is high, the engine is necessarily restricted to operate in a low load area, and it is difficult to operate at the best point of the engine thermal efficiency. The effect is low and the motor output needs to be relatively large in order to obtain the driving force required for running the vehicle, which increases the load on the motor. Further, under the operating condition with a low load, the emission amount of NOx and PM can be relatively small, but the oxidation temperature of the catalyst is low due to the low exhaust gas temperature, and the emission amount of HC and CO is relatively large.
[0005]
On the other hand, NOx catalysts and DPFs have been proposed to actively purify NOx and PM. That is, the exhaust gas of a diesel engine has a higher oxygen content than the exhaust gas of a gasoline engine operated near the stoichiometric air-fuel ratio, and the known three-way catalyst cannot purify NOx. When NOx is trapped and the air-fuel ratio of the inflowing exhaust gas becomes rich or stoichiometric, the trapped NOx is desorbed and the desorbed NOx is reduced using the reducing agent in the exhaust gas. A NOx catalyst for purification is provided. Further, since PM cannot be removed only by the catalyst, a filter for collecting PM in exhaust gas is provided to collect and remove PM.
[0006]
Therefore, not only HC and CO which are often generated in a low load region but also NOx and PM which are often generated when a high load is applied, these catalysts and NOx are required to have the same level as that required by society in recent years, that is, the atmospheric level. It is conceivable to use a combination of a catalyst and a filter.
[0007]
In this case, unless the operating points are set in consideration of the characteristics of the respective components, all the emission levels of HC, CO, NOx, and PM cannot be made equal to the SULV level or the atmospheric level.
[0008]
Therefore, an object of the present invention is to provide a diesel engine exhaust gas purification control device and a hybrid vehicle that can make all the emission levels of HC, CO, NOx, and PM equal to the SULEV level or the atmospheric level.
[0009]
[Means for Solving the Problems]
The present invention solves the above problem by the following means. Note that, for easy understanding, reference numerals corresponding to the embodiments of the present invention are given, but the present invention is not limited thereto.
[0010]
The present invention is arranged in an exhaust passage of a diesel engine (1), and oxidizes NO in exhaust gas when the temperature is equal to or higher than a first temperature and has high oxidizing NO. _Two Oxidation catalyst (21) capable of generating methane, and trapping PM in exhaust gas, and NO generated by the oxidation catalyst (21). _Two Thereby, the filter (22) capable of burning and removing the trapped PM, the NOx catalyst (23) capable of reducing and purifying NOx in exhaust gas, the temperature of exhaust gas becomes equal to or higher than the first temperature, and Operating point setting means (30) for setting an operating point of the diesel engine so that the PM content of the exhaust gas is equal to or less than a predetermined value.
[0011]
[Action / Effect]
NO to NO by oxidation catalyst _Two The conversion to is performed more actively as the exhaust gas temperature is increased, unless the oxygen concentration in the exhaust gas is extremely reduced. However, the higher the exhaust gas temperature, the more NO _Two Becomes thermodynamically unstable and produces NO _Two Returns to NO again. Therefore, the oxidation catalyst changes from NO to NO. _Two By setting the temperature in a temperature range equal to or higher than the first temperature (for example, in a range of about 250 to 450 ° C.) in which conversion to PM is actively performed, PM collected by the filter can be reduced to NO. _Two Reburns and can be continuously removed without depositing PM on the filter.
[0012]
Also, at this time, the oxidation catalyst has a strong oxidation activity, and oxidizes HC and CO in the exhaust gas to produce harmless H. _Two O, CO _Two To purify.
[0013]
On the other hand, the load at which the PM after passing through the filter is at the SULV level is determined as a predetermined value, and the operating point is determined so that the PM content of the exhaust gas is equal to or lower than the predetermined value. Can be suppressed.
[0014]
In this manner, according to the present invention, by setting the exhaust gas temperature to be equal to or higher than the first temperature and the PM content of the exhaust gas to be equal to or less than a predetermined value, the combination of the oxidation catalyst and the filter enables Since HC and CO in the exhaust gas are made harmless, PM is burned and removed, and NOx is not efficiently trapped and flowed downstream by the NOx catalyst, so that all components of PM, HC, CO, and NOx are removed. The SULEV level can be reached.
[0015]
When the amount of NOx trapped in the NOx catalyst becomes equal to or more than a predetermined value, it is necessary to regenerate the NOx catalyst. For this purpose, the air-fuel ratio may be temporarily made rich.
[0016]
In addition, by applying a diesel engine capable of reaching all the components of PM, HC, CO, and NOx to the SULEV level in a hybrid vehicle as described above, fuel efficiency can be improved and CO2 can be reduced. _Two It is also possible to reduce the amount of emissions.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings and the like.
[0018]
FIG. 1 is a system configuration diagram showing one embodiment of an exhaust gas purification control device for a diesel engine according to the present invention, and is a hybrid vehicle system, in particular, a parallel hybrid electric vehicle (hereinafter, referred to as “P-HEV”). It is a figure showing the case where it applied to.
[0019]
In FIG. 1, the hybrid vehicle runs on two types of power sources: the output of a diesel engine 1 and the output of a motor (also functioning as a generator) 53 that receives power supplied from a battery 50.
[0020]
The output of the diesel engine 1 is transmitted to a generator (which also functions as a motor) 51 for power generation, and drive wheels 55a and 55b from a power transmission mechanism (for example, a CVT with an electromagnetic clutch) 52 for driving the vehicle via a differential gear 54. Is transmitted to.
[0021]
The hybrid control unit 40 controls the distribution of the output of the diesel engine 1 between power generation and vehicle driving. The hybrid control unit 40 also controls the supply of power from the battery 50 to the motor 53 and, conversely, the recovery of regenerative power from the motor 53 to the battery 50 during deceleration. The hybrid control unit 40 includes a signal of an accelerator sensor 41 (L: an output signal proportional to the amount of depression of an accelerator pedal), a signal of a start key 42 (STA: Acc position and This is a signal corresponding to the ON position, and unlike a normal vehicle, there is no Start position), a signal (SFT) of the shift lever position sensor 43, a signal (BR) of the brake operation switch 44, and a signal (Vcar) of the vehicle speed sensor 45. ), The signal (Bcap) of the remaining battery charge sensor 46 and the like are input, and it is determined whether the start of the engine 1 and the output sharing are necessary, and a start command and an output sharing command are issued to the engine control unit 30. In accordance with the command, the engine control unit 30 sets the operating point of the diesel engine 1 and controls start and stop, and output.
[0022]
The diesel engine 1 includes an exhaust gas purification post-processing device 20 that purifies exhaust gas of the engine in the exhaust passage 3. The exhaust gas purification aftertreatment device 20 includes an OXC (oxidation catalyst) 21, a DPF (Diesel Particulate Filter) 22, and a NOx trap catalyst 23 from the upstream.
[0023]
As the OXC 21, for example, an activated alumina base carrying a noble metal such as Pd or Pt, a zeolite ion-exchanged with a noble metal (particularly Pt), or a combination of both materials can be used.
[0024]
The DPF 22 is a filter that traps PM in the exhaust gas. Various types of such filters are conventionally known, for example, a wall flow honeycomb type filter made of a SiC material or a cordierite material, and a cylindrical shape having a bottom having a large number of holes in a cylindrical portion. And the like in which ceramic fibers are wound around the core member in several layers. Further, OXC may be carried on the surface of the DPF, and the OXC and the DPF may be integrally formed. The PM collection efficiency of the DPF is very high. For example, a SiC DPF usually has a PM reduction efficiency of about 95% or more.
[0025]
The NOx trap catalyst 23 is a NOx adsorption catalyst that absorbs NOx when the inflowing exhaust gas has a lean air-fuel ratio, and releases, reduces and purifies NOx when the oxygen concentration of the inflowing exhaust gas decreases. The NOx trap catalyst 23 uses Ba, Mg, Cs or the like as a NOx adsorbent.
[0026]
The OXC 21 is provided with an exhaust temperature sensor 35 for detecting the exhaust gas temperature T1 of the inlet portion of the OXC 21 (the exhaust gas purification post-processing device 20). Further, between the outlet of the DPF 22 and the inlet of the NOx trap catalyst 23, an exhaust temperature sensor 36 for detecting the exhaust gas temperature T2 at the outlet of the DPF 22 (the inlet of the NOx trap catalyst 23), and an oxygen concentration sensor 37 Are provided.
[0027]
A turbocharger turbine 3a is arranged in the exhaust passage 3, and an EGR valve 5 is provided in an EGR passage 4 branched from the upstream of the turbine 3a. The EGR valve 5 is driven by a stepping motor (not shown) and recirculates a part of the exhaust gas to an intake pipe 2 d of the intake passage 2. The intake passage 2 includes an air cleaner 2a, a compressor 2b of a supercharger, an intercooler 2c, an intake throttle valve 7 driven to open and close by an actuator (for example, a stepping motor type) 6, and an intake pipe 2d from upstream. Reference numeral 24 denotes a glow plug for assisting engine start, which is provided facing the combustion chamber of each cylinder.
[0028]
The fuel supply system includes a diesel fuel (light oil) tank 60, a fuel supply passage 16 for supplying the diesel fuel to the engine fuel injection device 10, and a return fuel (spill fuel) from the engine fuel injection device 10 to the diesel fuel. A fuel return passage 19 for returning to the fuel tank 60 is provided.
[0029]
The fuel injection device 10 of the diesel engine 1 is a known common rail type fuel injection device, and includes a supply pump 11, a common rail (accumulation chamber) 14, and a fuel injection valve 15 provided for each cylinder. The fuel pressurized by the supply pump 11 is temporarily stored at a high pressure in the common rail 14 via the fuel supply passage 12 and then distributed to the fuel injection valves 15 for the number of cylinders.
[0030]
The pressure of the common rail 14 is controlled by the pressure control valve 13. That is, the pressure control valve 13 controls the pressure of the common rail 14 by changing the flow area of the overflow passage 17 in accordance with the duty signal from the engine control unit 30 to adjust the amount of fuel discharged to the common rail 14. In order to control the pressure of the common rail 14, a part of the fuel discharged from the supply pump 11 is returned to the fuel supply passage 16 through an overflow passage 17 having a one-way valve 18 in the middle.
[0031]
The fuel injection valve 15 is an electronic injection valve that opens and closes a fuel supply passage to the engine combustion chamber according to an ON-OFF signal from the engine control unit 30. The fuel injection valve 15 injects fuel into the combustion chamber according to the ON signal, and turns off the fuel. The injection is stopped by the signal. The fuel injection amount increases as the ON signal to the fuel injection valve 15 increases, but also changes depending on the fuel pressure of the common rail 14 as described later.
[0032]
The engine control unit 30 detects a signal (Tw) of the water temperature sensor 31, a signal of the crank angle sensor 32 (engine rotation speed and crank angle detection Ne), a signal of the crank angle sensor 33 (cylinder discrimination signal Cyl), and a common rail pressure. Signal (PCR) from the pressure sensor 34, a signal (T1) from the exhaust temperature sensor 35 for detecting the exhaust temperature at the inlet of the OXC 21, and an exhaust temperature sensor for detecting the exhaust temperature at the outlet of the DPF 22 or the inlet of the NOx trap catalyst 23. 36 (T2), the signal (O _Two ). Specific control of the engine control unit 30 will be described later.
[0033]
The exhaust gas purification control device according to the first embodiment of the present invention is controlled by a hybrid control unit 40 and an engine control unit 30, which will be described with reference to flowcharts of FIGS.
[0034]
FIG. 7 is a basic control routine of the hybrid system, and FIGS. 8 to 13 are outputs of the diesel engine 1 performed by the engine control unit 30 when an output sharing command is issued from the hybrid control unit 40 to the diesel engine 1. 2 shows a subroutine relating to control and exhaust gas purification control of the present invention.
[0035]
In the basic control routine of the hybrid system of FIG. 7, the signal (L) of the accelerator sensor 41, the signal (STA) of the start key 42, the signal (SFT) of the shift lever position sensor 43, the signal (BR) of the brake operation switch 44, The signal (Vcar) of the vehicle speed sensor 45 and the signal (Bcap) of the remaining battery charge sensor 46 are read, and the process proceeds to step S200.
[0036]
In step S200, as shown in FIG. 2, the driving force (Prun: abcdc-e in FIG. 2) required for running the vehicle according to the driver's depression amount (L) of the accelerator pedal. (−f line), that is, the driving force required by the driver to operate the vehicle by operating the accelerator is calculated, and the process proceeds to step S300. Basically, in this case, the signal STA of the start key 42 is at the ON position, and the signal SFT of the shift lever position sensor 43 is at the Drive position.
[0037]
In step S300, the operation mode is determined according to the driving force (Prun), the brake operation state (BR), the vehicle speed (Vcar), the remaining battery capacity (Bcap), and the like required for running the vehicle calculated in step S200. .
[0038]
The operation mode is roughly divided into the following patterns, and is determined based on the maximum output of the engine, the fuel consumption rate characteristics, the capacity of the battery, the maximum output of the motor, and the like.
[0039]
<Motor driving mode>
In FIG. 2, the driving force range (1) is based on the fact that the vehicle travels only with the driving force of the motor 53 (line ab). Therefore, the remaining capacity (Bcap) of the battery 50 must always be maintained at a predetermined value (a level at which the rated power of the battery can be supplied stably) or more. As a countermeasure against this, the battery is charged by power generation during the running of the engine described later.
[0040]
<Engine power generation mode when vehicle is stopped>
If the remaining capacity (Bcap) of the battery 50 falls below a predetermined value due to, for example, continuous motor running for a long time, in order to prevent the battery 50 from being over-discharged, 1 point (b point = g) in FIG. (The load is lower than the point.) That is, the engine output is not transmitted to the drive wheels but is used for power generation (charging).
[0041]
<Engine driving mode>
In FIG. 2, the driving force range indicated by {circle around (2)} indicates that the thermal efficiency of the engine 1 is good, as will be described later, and that when the remaining capacity (Bcap) of the battery 50 is equal to or larger than a predetermined value, the engine 1 It runs by power (bcd line).
[0042]
<Engine output split mode>
In the driving force ranges of (1), (2), and (3) in FIG. 2, when the remaining capacity (Bcap) of the battery 50 is equal to or less than a predetermined value, the engine is driven for vehicle running and power generation. . As described above, the abcdcef line in FIG. 2 is a driving force line necessary for running the vehicle, and outputs the output of the engine 1 for running and generating electricity as follows. Divided into
[(1) driving force range]
The difference between the gh line (= bc point operation) and the running ab line is supplied for power generation (charging) of the generator 51.
[(2) driving force range]
The difference between the hi-d line (= cd point operation) and the traveling b-c-d line is supplied for power generation (charging) of the generator 51.
[(3) driving force range]
The difference between the dke line (= k point operation) and the travel deline is supplied for power generation (charging) of the generator 51.
[0043]
<Motor assist mode>
In the driving force range of {circle around (3)}, if the remaining capacity (Bcap) of the battery 50 is a predetermined value or more and a level capable of stably supplying the rated power of the battery, the power of the motor is indicated by the de-e line in FIG. The vehicle runs using both the power of the engine and the power of the engine. That is, the engine is operated at the point d (= j), and the difference from the running de-e line is assisted by the motor 53.
[0044]
<Power assist mode>
The driving force range of (4) is basically the motor assist mode. However, the maximum output of the engine is the e point, and no more power can be supplied from the engine. Accordingly, the engine is operated at point e in FIG. 2 and the difference from point e to point f (Prun max.) Of the maximum driving force of the vehicle is assisted by the motor 53. When the remaining capacity (Bcap) of the battery is equal to or less than a predetermined value, the vehicle driving maximum driving force is limited to the e point because the motor assist cannot be performed to prevent overdischarge.
[0045]
<Deceleration regeneration mode>
The motor 53 functions as a generator during deceleration, recovers kinetic energy during deceleration as electric power, and charges the battery 50.
[0046]
In the above description, when the output of the engine 1 is not used as the driving force for driving the vehicle, that is, in the motor driving mode, the vehicle stop engine power generation mode, and the deceleration regeneration mode, the power interrupting portion (for example, (Electromagnetic clutch) is disconnected.
[0047]
Here, the driving force ranges (1) to (4) in FIG. 2 and their engine operating points a, b (= g), c (= h), d (= i = j), and e (= k). And the relationship with the target of the exhaust gas purification control device of the present invention will be described with reference to a region diagram divided by the engine speed and the engine load in FIG.
[0048]
The area is roughly divided into six areas A to F. Each area except the area F is defined by lines indicated by X, Y, and Z in FIG.
[0049]
<X line>
The X line is a temperature line indicating the relationship between the engine speed and the load when the temperature of the exhaust gas reaches the temperature (first temperature) at which the OXC 21 enters a predetermined oxidizing state. This temperature is desirably set to a temperature substantially equal to the lower limit temperature at which the activity of the NOx trap catalyst 23 becomes strong. In the present embodiment (that is, when Ba is used as the adsorbent of the NOx trap catalyst 23), As described below, about 250 to 300 ° C. is appropriate. If the temperature of the exhaust gas is set to a temperature equal to or higher than this line, the oxidation activity of the OXC 21 is strong, the removal efficiency of HC and CO is increased, and the HC and CO after passing through the OXC 21 can be brought to the SULV level. Conversely, if the temperature of the exhaust gas is below this line, it is difficult to bring HC and CO to the SULEV level. That is, the X line is a lower limit line for setting HC and CO to the atmospheric level.
[0050]
<Y line>
The Y line is set for each engine speed based on the PM collection efficiency of the DPF 22 (95% or more for a wall flow honeycomb type of SiC material) and the PM emission level of the engine, and the PM concentration after passing through the DPF 22 is reduced. This is a load line determined for each engine speed at which the SULEV level is reached. Desirably, it is appropriate to set the load such that the smoke concentration of the exhaust gas flowing into the DPF 22 is 1 BSU at the maximum, and the set load is low at a low rotational speed with low intake air volume efficiency (filling efficiency). Below this load line, the PM after passing through the DPF 22 can be set to the SULV level, and conversely, above this line, it is difficult to set the PM to the SULV level. That is, the Y line is a load upper limit line for bringing PM to the atmospheric level.
[0051]
<Z line>
The Z line is a temperature line indicating the relationship between the engine speed and the load when the temperature of the exhaust gas reaches a temperature at which the adsorption effect of the adsorbent of the NOx trap catalyst 23 does not decrease thermodynamically. As described above, the NOx adsorbent used for the NOx trap catalyst 23 usually uses Ba, Mg, Cs, or the like. However, as shown in FIG. 5 (which shows the NOx reduction characteristics of the NOx trap catalyst 23 using Ba as the adsorbent), when the temperature of the adsorbent increases (about 450 ° C. or higher), the NOx adsorption effect thermodynamically increases. As a result, the NOx adsorption / reduction purification performance of the NOx trap catalyst 23 decreases. Therefore, in order to set the NOx level after passing through the NOx trap catalyst 23 to the SULEV level, the NOx trap catalyst 23 must be at a temperature of about 250 to 300 ° C. at which the activity of the NOx trap catalyst 23 becomes strong, and It is desirable to use in the temperature range of the upper limit temperature (second temperature ≦ 450 ° C.) or lower where the adsorption effect does not decrease thermodynamically. That is, this Z line is the upper limit line for bringing NOx to the atmospheric level. Further, the above-mentioned X line is a lower limit line for bringing NOx to the atmospheric level.
[0052]
The respective areas and operating points defined by the above X line, Y line, and Z line will be described.
[0053]
<Area A>
In the area A, only PM reaches the SULV level, and HC, CO, and NOx do not reach the SULV level. Therefore, no operating point is set in this area. Point a is an idling condition for the engine, but is a condition that exists for a moment when the engine is started.
[0054]
<Area B>
In the region B, all components of PM, HC, CO, and NOx do not reach the SULV level. Therefore, no operating point is set in this region.
[0055]
<Area C>
In the region C, HC, CO, and NOx reach the SULV level, but PM does not reach the SULV level. Therefore, no operating point is set in this region.
[0056]
<Area D>
In the region D, HC and CO reach the SULV level, but NOx and PM do not reach the SULV level. Therefore, no operating point is set in this region.
[0057]
<Area E>
In the region E, all components of PM, HC, CO, and NOx reach the SULV level. Then, in the present invention, in the operation region E, the operation points b (= g), c (= h), d (= i = j), and e (= k) in the driving force range of (1) to (3) are set. ), And the engine load and the rotation speed are set so as to include each of the operation points described above and the l point of the engine power generation mode when the vehicle is stopped (the load and the rotation speed allowed to maintain quietness when the vehicle is stopped). . That is, a vehicle that is obtained by the driver through an accelerator operation (depressing amount of an accelerator pedal: L) at a driving point where all the components of PM, HC, CO, and NOx are set within a region E in which the SULEV level can be reached. The driving force required for traveling and the power generation output when the vehicle is stopped are obtained.
[0058]
<Area F>
The region F is included in the region E, and is a region of the engine load and the rotation speed where the engine efficiency is the best. The operating points c (= h) and d (= i = j) are set in this area.
[0059]
Here, the function of the exhaust gas purification aftertreatment device 20 of the present invention in the region E will be described in more detail.
[0060]
In the exhaust gas purification post-treatment device 20 of the present invention, an OXC 21, a DPF 22, and a NOx trap catalyst 23 are arranged from the upstream. The OXC 21 oxidizes NO (nitrogen monoxide) in the exhaust gas to NO. _Two (Nitrogen dioxide). Then, the DPF 22 collects the PM and converts the collected PM into the highly oxidizing NO generated by the OXC 21. _Two Burn and remove with. As described above, the exhaust gas purification post-processing device 20 has a function of a PM continuously reburning filter (referred to as JP-A-1-318715, hereinafter referred to as “CRF”) configured to regenerate the DPF.
[0061]
The reaction principle of the conventional PM removal of CRF is as described in (1) and (2) above. _Two If the amount is present, the PM collected by the DPF can be continuously removed even when the temperature of the OXC is relatively low, and the PM is not deposited on the DPF. Also, in OXC, from NO to NO _Two The conversion to NO depends on the catalyst temperature, from about 150 ° C to NO _Two Start converting to. In addition, the reactions shown in the above (1) and (2) also depend on the temperature, so that the higher the temperature, the more NO from OXC to NO _Two Is actively being converted to NO _Two Promotes reburning of PM. However, the higher the exhaust gas temperature, the more NO _Two Becomes thermodynamically unstable and produces NO _Two Will return to NO again. As a result, in practice, OXC changes from NO to NO _Two In the exhaust (catalyst) temperature range of about 250 to 450 ° C. in which the conversion to the catalyst is actively performed, the PM collected by the DPF is converted to NO. _Two Reburns and continuously removes and does not deposit PM on the DPF.
[0062]
That is, in the region E, all the components of PM, HC, CO, and NOx can reach the SULEV level, and in addition, the temperature condition is such that the NOx / PM ratio is relatively large and the exhaust temperature can obtain the CRF effect. Since they match, an effect is obtained that PM is continuously reburned and is not deposited on the DPF.
[0063]
This concludes the description of the traveling mode in step S300 and the relationship between the operating region of the engine, the driving force range necessary for vehicle traveling, and the respective operating points of the engine.
[0064]
Returning to FIG. After the driving mode is determined in step S300 as described above, the process proceeds to step S400, and based on the driving mode (Prun) required for traveling of the vehicle and the determined driving mode, the shared output (Pm and Pm) of the motor 53 and the engine 1 is determined. After calculating Pe) (FIG. 2), the process proceeds to step S500.
[0065]
In step S500, it is determined whether the engine 1 needs to be operated. If this determination is No and engine operation is not required (motor drive mode or vehicle stop-time power generation condition), the process proceeds to step S900 to perform stop operation control of engine 1.
[0066]
That is, the hybrid control unit 40 issues a stop command to the engine control unit 30. The engine control unit 30 performs stop control of the engine 1 according to the stop command. As a result, the operation of the EGR valve 5 and the intake throttle valve 7 is stopped, the fuel supply is stopped and held (the pressure control valve 13 and the fuel injection valve 15 of the supply pump 11 are turned off), and the engine 1 is stopped or stopped. .
[0067]
If the determination in step S500 is Yes and the engine 1 needs to be driven (each mode of engine power generation during vehicle stop, engine running, engine output split, motor assist, and power assist), the process proceeds to step S600.
[0068]
In step S600, it is determined whether engine 1 has already been started. If this determination is Yes and the engine 1 has already been operated, that is, an output command has already been transmitted from the hybrid control unit 40 to the engine control unit 30, and the engine control unit 30 If the output control of No. 1 is being performed, the process proceeds to step S700.
[0069]
In step S700, output control of the engine 1 for obtaining the engine-sharing output (Pe) calculated in step S400 is continued or started.
[0070]
On the other hand, if the determination in step S600 is No and the engine 1 has not been started yet, the process proceeds to step S800 to perform engine start operation control (a start command is issued).
[0071]
This start operation is also controlled by the hybrid control unit 40 and the engine control unit 30, and is performed according to a time chart shown in FIG. First, the glow plug 24 is preheated, and motoring of the engine 1 by the motor 51 is started. Next, when the motoring rotational speed of the engine 1 reaches a predetermined stable level (reaches in a very short time), the pressure control valve 13 and the fuel injection valve 15 of the supply pump 11 are driven to supply fuel commensurate with starting. It leads to a complete explosion.
[0072]
After performing the engine output control in step S700, the engine start operation control in step S800, and the engine stop operation control in step S900, the process proceeds to step S1100.
[0073]
In step S1100, hybrid control unit 40 performs power generation control of generator 51 based on the operation mode.
[0074]
Then, in step S1200, the motor driving force (Pm: Prun-Pe) calculated in step S400 based on the traveling mode is output to the motor 53. Alternatively, control is performed to operate the motor 53 as a generator during deceleration, recover kinetic energy during deceleration as electric power, and charge the battery 50.
[0075]
Finally, the process proceeds to step S1300 to perform a speed ratio control and an ON-OFF control of the power transmission mechanism 52 (for example, a CVT with an electromagnetic clutch) based on the traveling mode and the vehicle speed (Vcar).
[0076]
FIG. 8 shows a subroutine for the output control of the diesel engine 1 in the above-described step S700 performed by the engine control unit 30 when an output sharing command is issued from the hybrid control unit 40 to the diesel engine 1. It is a flowchart.
[0077]
In the engine output control routine of FIG. 8, in step S710, the water temperature Tw, the engine rotation speed Ne, the cylinder discrimination signal Cyl, the common rail pressure PCR, the exhaust temperature T1 at the inlet of the OXC21, the outlet of the DPF22 or the inlet of the NOx trap catalyst 23. The exhaust temperature T2 and oxygen concentration O2 of the section are read, and the process proceeds to step S720.
[0078]
In step S720, predetermined table data is searched to determine the engine rotation speed Ne and the fuel injection amount Qmain necessary to obtain the engine sharing output Pe calculated in step S400. The table data is set, for example, with the engine-sharing output Pe as a parameter, and is stored in the ROM of the engine control unit 30 in advance.
[0079]
After obtaining the engine speed Ne and the fuel injection amount Qmain in step S720, common rail pressure control is performed in step S730, and main injection control for engine output control is sequentially performed in step S740.
[0080]
The process proceeds to step S750 to determine whether or not the flag indicating that regeneration control of the NOx trap catalyst 23 is being performed (set 0 or 1 in step S775 / FIG. 13 step S1011 described later) is 1, that is, the NOx trap catalyst 23. Is being reproduced.
[0081]
If Yes in step S750 and the NOx trap catalyst 23 is being regenerated, the flow proceeds to step S1000 to continue or start the regeneration control of the NOx trap catalyst and return.
[0082]
If NO in step S750 and the NOx trap catalyst 23 is not being regenerated, engine combustion control is performed in step S760, and the flow advances to step S770 to integrate the NOx absorption amount of the NOx trap catalyst 23 to regenerate the NOx trap catalyst 23. Is determined, and a return is made.
[0083]
FIG. 9 is a flowchart showing a subroutine for common rail pressure control performed in step S730.
[0084]
In the common rail pressure control routine of FIG. 9, in steps S731 and S732, a predetermined map stored in the ROM of the engine control unit 30 is searched using the engine speed Ne and the fuel injection amount (load) Qmain as parameters. Then, a target reference pressure PCR0 of the common rail 14 and a reference duty ratio (reference control signal) Duty0 of the pressure control valve 13 for obtaining the target reference pressure PCR0 are obtained, and the flow proceeds to step S733.
[0085]
In step S733, the absolute value | PCR0−PCR | of the difference between the target reference pressure PCR0 and the actual common rail pressure PCR is determined, and this is compared with an allowable pressure difference ΔPCR0 set in advance for the target reference pressure PCR0.
[0086]
If | PCR0−PCR | is within the range of the allowable pressure difference ΔPCR0, the process proceeds to step S736 to maintain the same duty ratio by setting the reference duty ratio Duty0 to the valve opening duty ratio Duty, and to maintain the same duty ratio in step S737. The pressure control valve 13 is driven by transmitting a duty signal generated from the duty ratio Duty.
[0087]
On the other hand, if | PCR0−PCR | is not within the range of the allowable pressure difference ΔPCR0, the process advances from step S733 to step S734 to search a ROM table that is set in advance corresponding to PCR0−PCR (= ΔP). Thus, a duty cycle correction coefficient K Duty is obtained. For example, when the pressure difference ΔP is minus (PCR is larger than PCR0), the correction coefficient K Duty is set to a value smaller than 1, and when ΔP is plus (PCR is smaller than PCR0), Set K Duty to a value greater than one. Specifically, table data of the duty ratio correction coefficient K Duty is set according to the characteristics of the pressure control valve 13.
[0088]
Then, in step S735, a value (Duty0 × K Duty) obtained by correcting the reference duty ratio Duty0 by the correction coefficient KDduty is set as the valve opening duty ratio Duty. Then, in step S737, the pressure control valve 13 is controlled by the valve opening duty ratio Duty. Drive.
[0089]
FIG. 10 is a flowchart showing a subroutine of the main injection control performed in step S740 of FIG.
[0090]
In the main injection control routine of FIG. 10, in step S741, a predetermined map previously stored in the ROM of the engine control unit 30 is searched using the main injection amount Q main and the common rail pressure PCR as parameters, and the main injection period M Period is obtained, and the process proceeds to step S742. Here, the main injection period M period is set in m sec, and as shown in FIG. 4, if the main injection amount Q main is the same, the higher the common rail pressure PCR, the shorter the main injection period M period and the same common rail pressure PCR. Then, as the main injection amount Q main increases, the main injection period M period becomes longer.
[0091]
In step S742, using the engine speed Ne and the main injection amount Q main as parameters, a predetermined map stored in advance in the ROM of the engine control unit 30 is searched to determine the main injection start timing M start, and the process proceeds to step S743. .
[0092]
In step S743, the main injection start timing M start is corrected based on the water temperature Tw. For example, when the cooling water temperature is low, M start is advanced and the process proceeds to step S744. This correction is performed because, for example, the lower the water temperature Tw, the lower the temperature of the engine combustion chamber, and the ignition start timing is relatively delayed. Therefore, the emission amounts of HC, CO, PM (especially, SOF) are reduced. This is because, in order not to increase the value, it is desirable that the M start is advanced and the combustion start timing is kept constant.
[0093]
In step S744, based on the signals from the crank angle sensor 32 for detecting the crank angle and the crank angle sensor 33 for determining the cylinder, the fuel injection valve 15 of the cylinder to be main-injected is opened during the period from the injection start timing M start to M period. Drive to supply the main injection amount Q main.
[0094]
FIG. 11 is a flowchart showing a subroutine of engine combustion control performed in step S760 of FIG.
[0095]
In step S761, operation or stop of EGR is determined based on the engine sharing output Pe. That is, if it is equal to or less than the predetermined shared output in step S761, the process proceeds to step S762, and if it is equal to or larger than the predetermined shared output, the process proceeds to step S765.
[0096]
Here, all the operating points of the engine are set in the area E, but among the operating points in the area E, the operating points c (= h), d (= i = j) and the engine with the best engine efficiency are set. The line connecting the operating points e (= k), which are the maximum output points, stops EGR with the priority given to not increasing the smoke, and 1 and b (= with a relatively low load (large air excess ratio). g) At the point, it is desirable to perform EGR that can secure a NOx / PM ratio sufficient to exhibit the CRF function.
[0097]
In step S765, the EGR is stopped or stopped (the operations of the EGR valve 5 and the intake throttle valve 7 are stopped).
[0098]
In step S762, a predetermined map previously stored in the ROM of the control unit 30 is searched using the engine speed Ne and the fuel injection amount (load) Qmain as parameters, and the target EGR data (the EGR valve 5 and the intake throttle valve 7) are searched. Drive signal).
[0099]
After obtaining the target EGR data in step S762, the EGR is corrected based on the water temperature Tw in step S763. For example, when the cooling water temperature is low, the EGR is reduced and the process proceeds to step S764.
[0100]
In step S764, the drive control of the EGR valve 5 and the intake throttle valve 7 is performed based on the corrected drive signals.
[0101]
FIG. 12 is a flowchart showing a subroutine for integrating the NOx absorption amount of the NOx trap catalyst 23 and determining whether or not the regeneration is necessary, which is performed in step S770 in FIG.
[0102]
In the NOx absorption amount accumulation and regeneration necessity determination routine of FIG. 12, in step S771, for example, table data in which the engine shared output Pe is set as a parameter, or the engine rotation speed Ne and the fuel injection amount (load) Qmain are set as parameters. The NOx absorption amount (NOx absorption amount per unit time) of the NOx trap catalyst 23 is obtained by searching from predetermined data or the like set in a map format and stored in advance in the ROM of the control unit 30 in advance.
[0103]
After obtaining the NOx absorption amount in step S771, the process proceeds to step S772, and the NOx absorption amount is corrected based on the water temperature Tw. For example, when the cooling water temperature is low, the NOx absorption amount is corrected to decrease, and the process proceeds to step S773. The reason for performing such correction is as follows. That is, for example, the lower the water temperature, the lower the temperature of the engine combustion chamber, so that the ignition start timing is relatively delayed. Therefore, as described above, in step S743 in FIG. 10 and step S763 in FIG. 11, the main injection start timing M start is advanced and corrected, respectively, so as not to increase the emissions of HC, CO, and PM (especially, SOF). The EGR was reduced and the combustion start timing was kept constant. However, even if the combustion start timing is kept constant, the lower the engine combustion chamber temperature, the longer the combustion period tends to be, the lower the combustion temperature tends to be, and the lower the NOx emissions. Since the NOx absorption amount also tends to decrease as the NOx emission amount decreases, it is desirable to set a coefficient for reducing the NOx absorption amount as the water temperature is lower using the water temperature Tw as a parameter to correct the NOx absorption amount. Thus, the calculation accuracy of the integrated NOx absorption amount can be improved. Therefore, the correction is performed as described above. The correction coefficient for the NOx absorption amount is obtained in advance by an experiment.
[0104]
In step S773, the NOx absorption amount is integrated at predetermined time intervals synchronized with the NOx absorption amount per unit time, and the flow advances to step S774.
[0105]
In step S774, it is determined whether or not the integrated NOx absorption amount exceeds the predetermined absorption limit amount set in the NOx trap catalyst 23, and the regeneration (NOx release / reduction) of the NOx trap catalyst 23 is required. .
[0106]
If No in step S774 and reproduction is unnecessary, the process returns.
[0107]
If the determination in step S774 is Yes, the NOx absorption amount exceeds the absorption limit amount, and it is determined that the regeneration of the NOx trap catalyst 23 is necessary, the catalyst regeneration flag is set to 1 in step S775. A flag is set as a reproduction start signal). Then, the flow advances to step S776 to start counting an index value for ending reproduction, for example, time, and returns. The index value of the end of the regeneration is not limited to the example of the time, and the multiplier of the exhaust temperature T2 at the inlet of the NOx trap catalyst 23 and the time may be integrated.
[0108]
FIG. 13 is a flowchart showing a subroutine for the regeneration control of the NOx trap catalyst 23 performed in step S1000 of FIG.
[0109]
In the regeneration control routine of the NOx trap catalyst 23 in FIG. 13, in step S1001, it is determined whether a predetermined regeneration operation, that is, a predetermined time required to start regeneration and complete regeneration of the NOx trap catalyst 23 has elapsed. I do. Here, the time required to regenerate the NOx trap catalyst 23 by enriching the exhaust air-fuel ratio is approximately 1 to 2% in time ratio, and the time required for one regeneration depends on the catalyst capacity and the regeneration interval. Is also different.
[0110]
If the determination in step S1001 is Yes and the regeneration is completed, the process proceeds to step S1011 to initialize the regeneration control of the NOx trap catalyst 23. That is, the catalyst regeneration flag, the NOx absorption amount integrated value, and the regeneration time count are each reset to 0, and the routine returns.
[0111]
If the determination in step S1001 is No and the regeneration has not been completed, the process proceeds to step S1002, and it is determined whether or not the engine is in the EGR region based on the engine sharing output Pe.
[0112]
If it is determined in step S1002 that the vehicle is in the EGR region, the process proceeds to step S1003. If the vehicle is not in the EGR region, the process proceeds to step S1007.
[0113]
In step S1003, after the post injection is stopped or stopped, the process proceeds to step S1004 to obtain target EGR data for enriching the exhaust air-fuel ratio.
[0114]
Here, the post-injection is an expansion stroke of each cylinder separately from the main injection in order to regenerate the NOx trap catalyst 23 (release and reduce NOx) by enriching the exhaust air-fuel ratio and increasing the exhaust temperature. Alternatively, fuel injection is performed in the exhaust stroke. However, as described above, the region in which EGR is performed is a relatively low load region, and the excess air ratio is relatively large even when EGR is performed (λ = about 2 to 4). In order to enrich the exhaust air-fuel ratio by performing post-injection in such a low-load region, it is necessary to post-inject the fuel in an amount of 2 to 4 times the amount of the main injection fuel, and the injection time is short (time ratio). (About 1% to 2%), the fuel efficiency deterioration rate is large. Therefore, it is not advisable to perform post injection in such an EGR region.
[0115]
Therefore, after the post-injection is stopped (step S1003), in step S1004, a predetermined map stored in the ROM of the control unit 30 is searched using the engine speed Ne and the fuel injection amount (load) Q main as parameters. Thus, target EGR data (drive signals for the EGR valve 5 and the intake throttle valve 7) for enriching the exhaust air-fuel ratio by enhancing the EGR is obtained. By enhancing the EGR (intake throttle) and enriching the exhaust air-fuel ratio in this manner, an increase in exhaust gas temperature due to a decrease in the amount of working gas in the combustion chamber and a decrease in the amount of gas passing through the catalyst (a decrease in the SV ratio) can be achieved. And the NOx release / reduction reaction can be improved.
[0116]
In step S1005, drive control is performed based on the drive signals of the EGR valve 5 and the intake throttle valve 7, and EGR for enriching the exhaust air-fuel ratio is performed.
[0117]
Further, in step S1006, the signal (O _Two ), The EGR feedback control is performed, and the exhaust air-fuel ratio is kept rich to return.
[0118]
If it is determined in step S1002 that the region is the EGR stop region, the process proceeds to step S1007 to stop or hold the EGR (stop the operation of the EGR valve 5 and the intake throttle valve 7).
[0119]
In step S1008, in order to regenerate the NOx trap catalyst 23 (release and reduce NOx), the engine speed Ne and the fuel injection amount (load) Q main are stored in advance in the ROM of the control unit 30 as parameters. A predetermined map is searched to obtain a post injection amount Q post, a post injection period P period, and a post injection timing P start for enriching the exhaust air-fuel ratio and increasing the exhaust gas temperature.
[0120]
The EGR stop region is a relatively high load region, and the excess air ratio is relatively small (λ = about 2 to 1.5). Therefore, the post-injection amount necessary for enriching the exhaust air-fuel ratio by performing post-injection can be dealt with by injecting about 0.5 to at most twice as much fuel as the main injection fuel. The fuel consumption deterioration rate is relatively small.
[0121]
In addition, EGR in this region is inconvenient for DPF self-regeneration by CRF or the like, and the excess air ratio is relatively large. Therefore, when EGR is performed, PM (smoke) increases sharply, and the DPF 22 may be clogged. is there. Therefore, it is preferable to perform the post injection in the EGR stop region to enrich the exhaust air-fuel ratio.
[0122]
In step S1008, after searching for data related to post-injection (injection start timing P start and injection period P period), the process proceeds to step S1009.
[0123]
In step S1009, based on the signals from the crank angle sensor 32 for detecting the crank angle and the crank angle sensor 33 for determining the cylinder, the fuel injection valve 15 of the cylinder to be post-injected is opened during a period from the injection start timing P start to P period. Drive to supply the post injection amount Q post.
[0124]
Then, the process proceeds to step S1010, where the signal (O _Two ), The feedback control of the post injection (Q post) is performed to keep the exhaust air-fuel ratio rich and return.
[0125]
In the present embodiment, first, an OXC having a performance capable of purifying unburned components (HC, CO, etc.) contained in exhaust gas to a SULV level or an atmospheric level is used, and the OXC can sufficiently exhibit performance. The operating point is set to discharge the exhaust gas in such a temperature range to control the diesel engine.
[0126]
In addition, a diesel particulate filter having a performance capable of trapping PM to a SULV level or an atmospheric level is provided, and the amount of PM contained in the exhaust gas is reduced to the SULV level or the atmospheric level by the diesel particulate filter. The operating point is set so that the amount can be reduced as follows, and the diesel engine is controlled.
[0127]
Further, a NOx trap catalyst having a performance capable of purifying NOx to a SULV level or an atmospheric level is used, and an operating point is set such that the NOx trap catalyst emits exhaust gas in a temperature region where the performance can be sufficiently exhibited. Was set to control the diesel engine.
[0128]
With the above configuration, according to the present embodiment, it is possible to purify exhaust emissions such as HC, CO, NOx, and PM of a diesel engine to a SULEV level or a level equivalent to the atmosphere. It was.
[0129]
In the present embodiment, the OXC 21 is used as an activation lower limit temperature that is substantially equal to a lower limit temperature at which the activity of the NOx trap catalyst 23 becomes strong. If the lower-limit temperature of the NOx trap catalyst 23 is different from the lower-limit temperature of the OXC 21, for example, the lower-limit temperature of the OXC 21 is higher than the lower-limit temperature of the NOx trap catalyst 23. Unless the operating point is set in accordance with the activation lower limit temperature of the NOx trap catalyst 23 and the diesel engine is controlled, exhaust emissions of the diesel engine cannot be purified to the SULEV level or the atmospheric level. This means that even if OXC21 activated at a low temperature is used, its performance cannot be exhibited. Generally, OXC which is activated at a low temperature is more expensive in terms of cost, but there is no advantage even if such a cost is applied. Therefore, the use of the OXC 21 having an activation lower limit temperature substantially equal to the lower limit temperature at which the activity of the NOx trap catalyst 23 becomes strong as in this embodiment is the most preferable in terms of performance and cost. It is a well-balanced device.
[0130]
Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is apparent that they are equivalent to the present invention.
[0131]
For example, a case has been described above in which a diesel engine is applied to a P-HEV vehicle in which the range of use of the engine is relatively wide and the degree of difficulty in exhaust gas purification is high.
[0132]
However, the exhaust gas purification control device of the present invention can be suitably used not only for P-HEV, but also for a series hybrid electric vehicle (hereinafter referred to as “S-HEV”).
[0133]
The S-HEV differs from the P-HEV in structural point in that there is no power transmission mechanism 52 in FIG. That is, the S-HEV is based on the fact that the output of the engine is not directly transmitted to the driving wheels as the driving force, and the vehicle travels only with the driving force of the motor 53, and the driver's depression amount of the accelerator pedal ( L) means that all the necessary driving force for running the vehicle is covered by the motor output Pm.
[0134]
That is, all the output of the engine is transmitted to the generator 51 for power generation, and the engine is basically operated at a load and a rotational speed at which the maximum efficiency is obtained. Further, by setting this operating point to an operating point in the region E and at which the DPF self-regeneration effect by the CRF or the like is obtained (for example, the best point among c to d in FIG. 3), PM accumulates in the DPF. I can't.
[0135]
That is, it is possible to improve fuel efficiency and to simplify exhaust gas purification.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing one embodiment of a diesel engine exhaust gas purification control device of the present invention.
FIG. 2 is a characteristic diagram showing a relationship between an accelerator pedal position and a traveling driving force.
FIG. 3 is a characteristic diagram showing a relationship between an operating region and an operating point.
FIG. 4 is a characteristic diagram of a common rail pressure and a fuel injection amount depending on a fuel injection period.
FIG. 5 is a characteristic diagram of a conversion rate of a NOx trap catalyst.
FIG. 6 is a time chart of an operation performed at the time of starting.
FIG. 7 is a flowchart showing a basic control routine of the hybrid system.
FIG. 8 is a flowchart showing a control routine of an engine output.
FIG. 9 is a flowchart showing a common rail pressure control routine.
FIG. 10 is a flowchart showing a main injection control routine.
FIG. 11 is a flowchart showing a combustion control routine of the engine.
FIG. 12 is a flowchart illustrating a NOx absorption amount integration / determination routine;
FIG. 13 is a flowchart showing a NOx trap catalyst regeneration control routine.
[Explanation of symbols]
1 Diesel engine
3 Exhaust passage
10 Fuel injection device
20 Exhaust gas purification after-treatment device
21 OXC (oxidation catalyst)
22 DPF (filter)
23 NOx trap catalyst (NOx catalyst)
30 Control unit for engine (operating point setting means)
40 Control unit for hybrid
50 battery
51 generator
52 power transmission mechanism
53 motor
54 differential gear
55a, 55b drive wheels

Claims (14)

An oxidation catalyst disposed in an exhaust passage of a diesel engine, the oxidation catalyst being capable of oxidizing NO in exhaust gas when the temperature is equal to or higher than a first temperature to generate NO ₂ having a high oxidizing power;
A filter capable of collecting PM in the exhaust gas and burning and removing the collected PM by NO ₂ generated by the oxidation catalyst;
A NOx catalyst capable of reducing and purifying NOx in exhaust gas,
Operating point setting means for setting an operating point of the diesel engine such that the temperature of the exhaust gas is equal to or higher than the first temperature and the PM content of the exhaust gas is equal to or lower than a predetermined value;
An exhaust gas purification control device for a diesel engine, comprising: The operating point setting means is configured to control the exhaust gas temperature of the diesel engine such that the exhaust gas temperature is equal to or higher than the first temperature and the PM content of the exhaust gas is equal to or lower than a predetermined value in the entire rotation range of the diesel engine. Set operating point,
The exhaust gas purification control device for a diesel engine according to claim 1, wherein: The operating point setting means sets an engine load when the first temperature is obtained in advance according to an engine rotation speed, and sets an operating point so as not to fall below the engine load.
The exhaust gas purification control device for a diesel engine according to claim 1, wherein: An oxidation catalyst disposed in an exhaust passage of a diesel engine, the oxidation catalyst being capable of oxidizing NO in exhaust gas when the temperature is equal to or higher than a first temperature to generate NO ₂ having a high oxidizing power;
A filter capable of collecting PM in the exhaust gas and burning and removing the collected PM by NO ₂ generated by the oxidation catalyst;
A NOx catalyst capable of reducing and purifying NOx in exhaust gas at a temperature equal to or lower than a second temperature higher than the first temperature;
An operating point for setting the operating point of the diesel engine such that the temperature of the exhaust gas is equal to or higher than the first temperature and equal to or lower than the second temperature, and the PM content of the exhaust gas is equal to or lower than a predetermined value. Setting means;
An exhaust gas purification control device for a diesel engine, comprising: The operating point setting means determines that the exhaust gas temperature is equal to or higher than the first temperature and equal to or lower than the second temperature, and the PM content of the exhaust gas is equal to or lower than a predetermined value in the entire rotation range of the diesel engine. Setting the operating point of the diesel engine so that
The exhaust gas purification control device for a diesel engine according to claim 4, wherein: The operating point setting means sets an engine load when the first temperature and the second temperature are obtained in advance according to the engine speed, and sets the operating point so as to fall within the range of the engine load. ,
The exhaust gas purification control device for a diesel engine according to claim 4, wherein: The operating point setting means sets an engine load when the PM content of the exhaust gas is equal to or less than a predetermined value in advance according to the engine speed, and sets an operating point so as not to exceed the engine load.
The exhaust gas purification control device for a diesel engine according to any one of claims 1 to 6, characterized in that: The operating point setting means sets an operating point based on an accelerator pedal depression amount,
The exhaust gas purification control device for a diesel engine according to any one of claims 1 to 7, characterized in that: The operating point setting means sets an operating point to include the highest efficiency point of the diesel engine,
The exhaust gas purification control device for a diesel engine according to any one of claims 1 to 8, wherein: The oxidation catalyst is supported on the surface of a filter portion that captures PM,
The exhaust gas purification control device for a diesel engine according to claim 1 or 4, wherein: The NOx catalyst traps NOx in the exhaust when the air-fuel ratio of the exhaust is lean, and releases and traps the trapped NOx when the air-fuel ratio of the exhaust becomes rich or stoichiometric. A NOx trap catalyst for reducing and purifying NOx by using a reducing agent in exhaust gas;
The exhaust gas purification control device for a diesel engine according to claim 1 or 4, wherein: The predetermined value of the PM content of the exhaust gas is an amount that can be reduced to a SULEV level or less after passing through the NOx catalyst.
The exhaust gas purification control device for a diesel engine according to claim 2 or 5, wherein: A parallel-type hybrid vehicle including an electric motor and a diesel engine, which can be independently driven for running the vehicle, and can be operated in combination with each other,
An exhaust purification control device for a diesel engine according to any one of claims 1 to 12.
A hybrid vehicle of a parallel system, characterized in that: A series type hybrid vehicle comprising an electric motor, a diesel engine, and a generator connected to the diesel engine, wherein only the electric motor is operated for vehicle running, and the diesel engine is operated only for generating electric power from the generator. hand,
An exhaust purification control device for a diesel engine according to any one of claims 1 to 12.
A series-type hybrid vehicle characterized by the following.

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