JP5701009B2 - Apparatus and method for controlling torque fluctuation suppression of diesel engine - Google Patents

Description

  The present invention relates to a control device for suppressing fluctuations in torque generated during regeneration of a DPF disposed in an exhaust system of a diesel engine equipped with an internal EGR.

The exhaust system of a diesel engine (hereinafter referred to as “engine”) includes a diesel particulate filter (hereinafter referred to as “PM (Particulate Matter)”) contained in exhaust gas discharged from the engine. Hereinafter, “DPF (Diesel Particulate Filter)” is provided.
When PM accumulates in the DPF due to engine operation, the exhaust gas flow resistance in the exhaust system increases and affects the engine output.
Therefore, after the engine has been operating for a certain time, it is necessary to burn and remove the PM accumulated in the DPF.

As a means of burning and removing the accumulated PM, fuel is injected into the cylinder during the expansion stroke of the engine. During the exhaust stroke, the injected fuel flows along with the exhaust gas from the exhaust port to the exhaust system, and the fuel is discharged to the DOC. A so-called late post-injection fuel injection method is used in which the PM accumulated in the DPF is combusted by increasing the exhaust gas temperature by combustion.
In FIG. 9, the horizontal axis represents the crankshaft angle, the vertical axis represents the lift amount of the valve, the late post injection timing, the exhaust valve, the intake resumption (the intake valve is opened for internal EGR) timing, The timing diagram with a valve is shown.
In an engine equipped with an internal EGR, while the combustion gas pressure in the cylinder during the expansion stroke is high, the intake valve is opened to ensure the amount of EGR gas necessary for NOx reduction.
As a result, as shown in FIG. 9, late post injection is performed at a stage before the BDC (piston bottom dead center) before the intake resumption timing, that is, at a timing approaching the end of the expansion stroke (immediately before the exhaust valve is opened). Is done.
In this case, since the pressure in the combustion chamber is still relatively high at that time, the penetration force of the late post-injection fuel in the combustion chamber is weak, and the fuel exists in a dense state in the upper portion of the combustion chamber.
As a result, if the resumption of intake is performed before the exhaust valve is fully opened, the late post-injected fuel enters the intake port, recirculates into the cylinder during the next cycle, and burns, resulting in shaft torque. This contributes to the fluctuation of the torque of the vehicle, resulting in a problem that drivability is reduced.

Japanese Unexamined Patent Application Publication No. 2009-243360 (Patent Document 1) is disclosed as a prior art that controls the opening and closing timing of the intake valve and the exhaust valve.
According to Patent Document 1, when the engine is cold-started, the opening period of the intake valve and the opening period of the exhaust valve are increased by the valve timing control means by the valve timing control means, and the exhaust gas discharged into the exhaust passage is increased. It is disclosed that the part is recirculated into the combustion chamber (cylinder).
This is a technique for the purpose of increasing the air in the combustion chamber by the heat of the exhaust gas, and does not purify the exhaust gas arranged in the exhaust gas system by late post injection.
Furthermore, in JP 2007-16611 (Patent Document 2), in order to remove PM when the accumulated amount of PM exceeds an allowable amount, an oxidation catalyst is provided on the upstream side of the DPF, and an expansion stroke or A method of forcibly removing PM by injecting unburnt fuel (hydrocarbon HC) with an oxidation catalyst and forcibly removing PM by using the oxidation reaction heat generated by the oxidation by performing late post injection in the exhaust stroke. Disclosure is made.
However, since the engine is not equipped with an internal EGR, when the burned gas is recirculated into the combustion chamber, it is not affected by engine torque fluctuations caused by re-inhalation of the late post-injected fuel.

Japanese Patent Laid-Open No. 2010-138898 (Patent Document 3) discloses an intake valve opening / closing timing control.
As shown in FIG. 8, in an engine 01 having a DOHC type valve mechanism, timing pulleys 04 and 05 are connected to the front ends of the intake camshaft 02 and the exhaust camshaft 03, respectively. It is connected to the crankshaft 07 via a timing belt 06. The intake camshaft 02 and the exhaust camshaft 03 are rotationally driven together with the timing pulleys 04 and 05 with the rotation of the crankshaft 07. The cam provided on the intake camshaft 02 causes the intake valve 08 to move to the exhaust camshaft 03. The exhaust valve 09 is driven by the provided cam.
A variable valve operating device 012 is employed as a valve operating mechanism for driving the intake valve 08. The variable valve operating apparatus is provided with a cam shaft phase variable mechanism (variable valve timing mechanism) 011 and a variable valve lift mechanism 012.

JP 2009-243360 A JP 2007-16611 A JP 2010-138898 A

However, in any of these Patent Documents 1 to 3, even if these disclosed technologies are combined in an engine equipped with an internal EGR, fuel is prevented from returning again from the intake valve into the cylinder by late post injection. There is no technical disclosure.
Therefore, the present invention has been made to solve such a problem, and the fuel by late post-injection performed at the time of DPF regeneration performs internal EGR by the intake valve that temporarily lifts the intake valve during the exhaust stroke. An object of the present invention is to provide a torque fluctuation suppression control device for a diesel engine that achieves both good drivability and efficient DPF regeneration by suppressing the torque fluctuation of the engine without returning to the combustion chamber again by the device. And

The present invention achieves such an object. In order to regenerate a DPF device that captures diesel exhaust particulates in exhaust gas, a late post-injection performed at the time of DPF regeneration is performed, and an internal EGR is provided by an intake valve that is temporarily lifted during an exhaust stroke. In the torque fluctuation suppression control method for a diesel engine equipped with an internal EGR device for performing
The late post-injection is performed at an early stage during the exhaust valve opening period of the diesel engine, and the opening timing of the small lift of the intake valve that performs the internal EGR is opened in the vicinity of the lift apex of the exhaust valve. The closing timing is set in the middle of the closing, and the late post injection end timing and the intake valve opening period of the internal EGR device do not overlap.

With such a configuration, the late post injection end timing and the intake valve opening timing of the internal EGR do not overlap, so that the fuel of the late post injection does not easily flow from the intake valve to the intake port side. It is possible to prevent the fuel of the late post-injection from recirculating, and to suppress engine torque fluctuations.
In addition, since the late post injection is set to be performed at the initial stage of the exhaust valve opening period (immediately before the end of the expansion stroke), the pressure in the cylinder is relatively high, and the fuel of the late post injection in the cylinder The penetration force is weak, the diffusion into the cylinder is suppressed, and the gas is efficiently supplied from the exhaust port to the DPF side.

  In the present invention, preferably, the late post-injection timing is performed when the torque fluctuation rate during the exhaust stroke of the engine is the lowest.

  With such a configuration, the torque fluctuation of the engine can be suppressed because the position where the torque fluctuation is lowest (near the end of the expansion stroke; the piston is near the bottom dead center) is less affected by the torque fluctuation due to the late post injection.

  In the present invention, preferably, the operation of the intake valve of the internal EGR has at least one of an operation of extending the opening period, increasing the lift amount, or changing the opening timing.

  With such a configuration, since the late post injection end period and the intake valve opening period of the internal EGR device do not overlap, the intake valve opening timing of the internal EGR device is delayed in timing, and the pressure in the cylinder is reduced. Since it becomes low, it has an effect which supplements that it becomes difficult to ensure the amount of EGR gas required for NOx reduction.

The present invention also provides an internal EGR device that performs late post-injection performed during DPF regeneration in order to regenerate a DPF device that captures diesel exhaust particulates in exhaust gas, and performs internal EGR by an intake valve that is temporarily lifted during an exhaust stroke. In a diesel engine torque fluctuation suppression control device equipped with
The late post injection amount determining means having a map for calculating the late post injection amount from the rotational speed of the diesel engine and the fuel injection amount, and the late post injection timing from the rotational speed of the diesel engine and the fuel injection amount. Late post injection timing determining means, late post injection amount determining means, late post injection end timing calculating means for calculating late post injection end timing based on the calculated values of the late post injection timing determining means, and the late post Intake resumption timing determining means for calculating a resumption timing at which the intake valve of the internal EGR device does not overlap with the late post injection end time based on the calculation result of the injection end time calculation means, and the exhaust valve is opened to the late post injection During the initial period of the period, The small lift of the intake valve for the EGR opening lift near the vertex of the exhaust valve, as the timing of closing in the middle to close from the exhaust valve begins to close, the intake valve of the late post-injection end timing and the internal EGR device It is characterized by not overlapping with the opening period .

With such a configuration, the late post injection end timing and the intake valve opening timing of the internal EGR do not overlap, so that the fuel of the late post injection does not easily flow from the intake valve to the intake port side. It is possible to prevent the fuel of the late post-injection from recirculating, and to suppress engine torque fluctuations.
In addition, since late post injection is the initial stage during the exhaust valve opening period (immediately before the end of the expansion stroke), the pressure in the cylinder is high, the fuel of late post injection has a weak penetration force in the cylinder, and diffusion into the cylinder is suppressed. Therefore, the fuel of late post injection is efficiently supplied from the exhaust port to the DPF device side.

  Preferably, in the present invention, the intake resumption timing determining means, an intake resumption period determining means for calculating an intake resumption period from the rotational speed and fuel injection amount of the diesel engine, and the rotational speed and fuel injection amount of the diesel engine. The intake resumption valve lift amount determining means for calculating the valve lift amount of the intake resumption valve from the intake resumption valve based on the calculated values of the intake resumption timing determination means, the intake resumption period determination means and the intake resumption valve lift amount determination means. The valve drive control content may be calculated, and variable valve timing means for driving the intake resumption valve based on the drive control content may be provided to secure the internal EGR gas amount.

  With such a configuration, at the time of DPF regeneration, there is an effect that NOx can be reduced by securing the internal EGR gas amount while suppressing torque fluctuation due to late post injection.

  Preferably, in the present invention, a DPF temperature detecting means for detecting the temperature of the DPF device, and a late post injection for correcting the late post injection amount so that the detected temperature detected by the DPF temperature detecting means becomes a target temperature. It is good to provide a quantity correction means.

  With such a configuration, even when the late post injection amount and the injection timing change, while suppressing the torque fluctuation of the engine, ensuring an appropriate amount of internal EGR gas, reducing NOx, and regenerating the DPF device. It has an effect that can be done reliably.

  The internal EGR device that performs internal EGR by the intake valve that temporarily lifts the intake valve during the exhaust stroke does not return to the combustion chamber again by the late post-injection fuel that is performed during DPF regeneration, thereby suppressing fluctuations in engine torque. Thus, both good drivability and efficient DPF regeneration can be achieved.

1 shows a schematic configuration diagram according to a first embodiment of the present invention. FIG. FIG. 3 is a diagram showing the relationship between the intake resumption timing of the intake valve and the late post injection according to the first embodiment of the present invention. (A) according to the second embodiment of the present invention shows a crank angle on the horizontal axis, an exhaust valve on the vertical axis, and a timing chart for resuming intake, and (B) shows the crank angle on the horizontal axis and the torque fluctuation rate on the vertical axis. The relationship diagram of is shown. The control flowchart regarding the late post injection which concerns on 2nd Embodiment of this invention is shown. The control flowchart regarding the late post injection which concerns on 3rd Embodiment of this invention is shown. The relationship diagram of the intake restart timing of the intake valve and the late post injection according to the fourth embodiment of the present invention is shown. The control flowchart regarding the late post injection which concerns on 4th Embodiment of this invention is shown. 1 shows a schematic diagram of a variable valve timing mechanism according to the prior art. The relationship figure of the late post-injection timing with respect to the crank angle by a prior art, and the timing of an exhaust valve and intake resumption is shown.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(First embodiment)
A description will be given with reference to FIG.
FIG. 1 shows a schematic configuration of an engine torque fluctuation suppression control device of the present embodiment. Reference numeral 1 denotes a diesel engine (hereinafter referred to as an “engine”) that is an internal combustion engine provided with a common rail type fuel spray device 2. A turbocharger 7 having an exhaust turbine 72 driven by exhaust gas from the engine 1 is disposed in the exhaust pipe 12 on the downstream side of the exhaust system of the engine 1. The turbocharger 7 is disposed coaxially with the exhaust turbine 72 and is provided with a compressor 71 that pressurizes intake air by the driving force of the exhaust turbine 72.

On the downstream side of the exhaust pipe 12 of the exhaust turbine 72, oxygen in the exhaust gas is used to oxidize unburned substances (soluble organic component: SOF) mainly composed of hydrocarbons (HC) in the exhaust gas to produce water (H ₂₀ ) and an oxidation catalyst (DOC) 5 that changes to carbon dioxide (CO ₂ ), and the oxidation catalyst (DOC) 5 are arranged with a slight gap to collect particulate matter (PM) in the exhaust gas. A particulate filter (DPF) 6 (hereinafter referred to as “DPF”) is integrally provided.

On the exhaust gas inlet side of the oxidation catalyst (DOC) 5, a first temperature sensor 61 that measures the temperature of the exhaust gas from the engine 1 is connected to the DPF 6 between the oxidation catalyst (DOC) 5 and the particulate filter (DPF) 6. A second temperature sensor 62 for measuring the temperature of the entering exhaust gas is provided, and a third temperature sensor 63 for detecting the temperature of the exhaust gas discharged is disposed on the exhaust gas outlet side of the DPF 6.
The temperature of the particulate filter (DPF) 6 is calculated from the detection values detected by the second temperature sensor 62 and the third temperature sensor 63.

On the other hand, in the case of the engine 1 that also uses the external EGR, the air supply pipe 13 that connects the compressor 71 of the turbocharger 7 and the engine 1 is connected to the intercooler 17 that cools the supply air in order from the upstream side of the supply system, A throttle valve 8 for adjusting the amount is provided.
Further, an EGR pipe 14 that branches from an intermediate portion between the engine 1 of the exhaust pipe 12 and the exhaust turbine 72 and is connected to the downstream side of the throttle valve 8 of the air supply pipe 13 is disposed.
An EGR cooler 15 that cools the exhaust gas and an EGR valve 16 that adjusts the EGR amount to the engine 1 are disposed in order from the exhaust system upstream side of the EGR pipe 14.

  Reference numeral 18 denotes a control device. The control device 18 includes an engine speed sensor 11 that detects the speed of the engine 1, an engine load sensor 10 that detects a fuel injection amount from the fuel injection device 2 as an engine load, and an oxidation catalyst (DOC). ) A first temperature sensor 61 for detecting the temperature of the exhaust gas at the exhaust gas inlet side 5, and a second temperature sensor 62 for detecting the temperature of the exhaust gas entering the DPF 6 between the oxidation catalyst (DOC) 5 and the particulate filter (DPF) 6. Data is input to the exhaust gas outlet side of the DPF 6 from each of the third temperature sensors that detect the temperature of the exhaust gas discharged.

FIG. 2 shows the valve timing when the fixed cam mechanism is provided, with the abscissa indicating the crank angle, the ordinate indicating the exhaust valve lift amount, and the timing diagram for restarting the intake air.
Note that the resumption of intake air is performed in order to introduce exhaust gas into the combustion chamber by opening the valve of the engine equipped with an internal EGR, and the valve lift cam for resuming intake air is the camshaft (not shown) of the above-described fixed cam mechanism. ).
The rough hatched portion in FIG. 2 indicates the proper zone Z for late post injection, the proper zone Z indicates the range from degATDC 170 to degATDC 200, and the precise hatched portion Y indicates the late post injection timing and injection period. .
In addition, the intake resumption timing may be started with a certain interval β (deg) (for example, about 8 to 15 deg) on the crank angle from the end of the appropriate zone.
This interval is controlled to a constant interval β [deg] even if the late post injection timing is advanced or retarded.
This is to expect that the fuel that has been late post-injected efficiently flows to the exhaust port side by providing a constant interval β [deg] (interval) after the late post-injection until the resumption of intake.
The intake resumption timing is opened near the top of the lift of the exhaust valve, and closes when the exhaust valve starts to close.
Further, by changing the lift amount change of the intake resumption valve and the resumption period of the intake resumption valve by changing the cam profile, the collection of the exhaust gas amount necessary for EGR can be adjusted.

As shown in FIG. 3B, the torque fluctuation is reduced in the range from degATDC170 to degATDC200, and the increase in torque can be suppressed by performing late post injection at this time.
This is because the exhaust gas flow in the combustion chamber becomes stronger around the range of degATDC170 to degATDC200, and this exhaust gas flow also affects the flow toward the exhaust port near the injector, so that the diffusion of late post-injected fuel does not progress much. It is estimated that the gas is discharged from the exhaust port as it is.
As a result, it is possible to prevent the late post-injected fuel from recirculating into the combustion chamber in the next intake stroke, or to suppress the recirculation amount to the extent that the torque fluctuation is not affected.
In the case of an engine using both external EGR and internal EGR, the EGR valve 16 and the intake valve of the internal EGR are adjusted so that the sum of the external EGR amount and the internal EGR amount becomes an appropriate EGR amount (target EGR amount). What is necessary is just to adjust the lift amount, the lift period, etc.

(Second Embodiment)
3A shows a timing diagram of the crank angle on the horizontal axis, the exhaust valve and the resumption of intake air on the vertical axis, and FIG. 3B shows the crank angle on the horizontal axis and the vertical axis with the variable valve timing mechanism. The relationship figure of a torque fluctuation rate is shown.
Since the configuration related to the engine torque fluctuation suppression control device in the second embodiment is substantially the same as in the first embodiment, the same actions are denoted by the same reference numerals, and the description thereof is omitted.
Since the variable valve timing mechanism is a known technique as described in the prior art, description of the structure is omitted.
In FIG. 3A, the rough hatched portion indicates the appropriate zone Z for late post injection, and this appropriate zone Z is obtained from the experimental results in the range from degATDC170 to degATDC200.
A dense shaded portion Y indicates the late post injection timing and period.
The intake resumption timing is started at a constant interval β (deg) (for example, about 8 to 15 deg) on the crank angle from the late post injection end timing.
This interval is controlled to a constant interval β [deg] even if the late post injection timing is advanced or retarded α [deg] (see FIG. 6).
Accordingly, the late post injection timing is advanced or retarded α [deg] (see FIG. 6) depending on the engine speed and the fuel injection amount in the late post injection appropriate zone Z, but at a constant interval β [deg]. Is held, and the intake resumption timing changes accordingly. (See Figure 6)
The intake resumption timing is opened near the top of the lift of the exhaust valve, and closes when the exhaust valve starts to close.

As shown in FIG. 3B, the torque fluctuation is reduced in the range from degATDC170 to degATDC200, and the increase in torque can be suppressed by performing late post injection at this time.
This is because the exhaust gas flow in the combustion chamber becomes stronger around the range of degATDC170 to degATDC200, and this exhaust gas flow also affects the flow toward the exhaust port near the injector, so that the diffusion of late post-injected fuel does not progress much. It is estimated that the gas is discharged from the exhaust port as it is.
As a result, it is possible to prevent the late post-injected fuel from recirculating into the combustion chamber in the next intake stroke, or to suppress the recirculation amount to the extent that the torque fluctuation is not affected.

FIG. 4 is a control flowchart regarding late post injection at the start of DPF regeneration in the second embodiment.
When PM accumulates on the DPF, the ECU 19 determines the start of DPF regeneration in step S1.
Based on the engine speed sensor 11 and the value detected by the engine load sensor 10 in step S2, the late post injection amount is calculated from the late post injection amount map.
Based on the value detected by the engine load sensor 10 and the engine speed sensor 11 in step S3, the late post injection timing is calculated by the late post injection timing map.
In step S4, the late post injection end timing is calculated from the late post injection timing and the late post injection amount, and in step S5, a constant interval β (deg) (constant interval; relative to the late post injection end timing calculated in step S4. (Interval on crank angle) is provided to calculate the intake resumption timing. In step S6, the ECU 18 sets the late post fuel injection amount, the late post injection timing, and the intake resumption timing, and performs intake resumption timing control.
The intake resumption timing is implemented by a known variable valve timing mechanism (not shown).

With this configuration, the flow of combustion gas in the cylinder at the beginning of the exhaust stroke is strong, the combustion chamber is at a relatively high pressure, and the late post-injected fuel has low penetrability and fuel at the top of the cylinder. It is discharged from the exhaust port in a dark state.
In addition, since a constant interval β (deg) (crank angle) is provided from the end timing of the late post fuel injection, the late post injected fuel is prevented from returning to the intake port side or slightly (influence on torque fluctuation). To a certain degree of reflux).
Accordingly, the late post-injected fuel is efficiently supplied from the exhaust port to the exhaust aftertreatment device, and the DPF regeneration can be performed efficiently and the fuel recirculated to the intake port side can be suppressed, so that torque fluctuation can be reliably prevented. .

(Third embodiment)
FIG. 5 is a control flow diagram regarding late post injection at the start of DPF regeneration in the third embodiment.
When PM accumulates on the DPF, the ECU 20 determines the start of DPF regeneration in step S1.
Based on the values detected by the engine load sensor 10 and the engine load sensor 10 in step S2, the corrected intake restart timing is calculated by the intake restart timing correction map.
Based on the value detected by the engine load sensor 10 and the engine speed sensor 11 in step S3, the corrected intake resumption period is calculated by the intake resumption period correction map.
Based on the value detected by the engine load sensor 10 and the engine speed sensor 11 in step S4, the corrected intake restart valve lift amount is calculated from the intake restart valve lift correction map.
In step S5, the ECU 19 executes a program for changing the intake resumption timing and changing the intake resumption valve lift amount, and in step S6, implements late post injection.
Note that the change of the intake resumption timing and the change of the intake resumption valve lift amount are performed by a known variable valve timing mechanism (not shown).

  According to the present embodiment, during DPF regeneration, a constant interval β (deg) is taken in the crank angle from the end of the late post injection to the start of the intake resumption valve lift, and the late post is at a time when there is little torque fluctuation in the range from degATDC170 to degATDC200. Since the injection is performed, it is possible to suppress the late post-injection fuel from returning to the combustion chamber during the intake stroke, thereby effectively preventing torque fluctuation.

(Fourth embodiment)
Since the configuration related to the engine torque fluctuation suppression control device in the third embodiment is substantially the same as in the first embodiment, the same actions are denoted by the same reference numerals, and description thereof is omitted.

FIG. 6 shows the relationship between the late post injection timing and the exhaust valve and intake resumption timing when the variable valve timing mechanism is provided, the abscissa indicates the crank angle, and the ordinate indicates the lift amount of the exhaust valve and intake resumption timing. .
A rough hatched portion indicates an appropriate zone Z for late post injection, and this appropriate zone Z indicates a range from degATDC170 to degATDC200, which has been described in the second embodiment, and is omitted.
In this embodiment, the intake post restart period and the lift amount are made variable in addition to the late post injection period and the intake restart timing variable.
It shows that the late post-injection period increased by α (deg) X (spotted portion) by the engine speed and the fuel injection amount.
Accordingly, it is shown that the intake air resumption timing is also retarded by α (deg).
Further, although there is no change in the late post injection period Y (the dense hatched portion), similarly, when the late post injection timing is delayed by α (deg), the intake resumption timing is also delayed by α (deg). .

The control method will be described along the flowchart of FIG.
In the control of the intake resumption valve, when PM accumulates in the DPF, the ECU 21 determines in step S1 that the DPF regeneration is started.
Based on the values detected by the engine load sensor 10 and the engine load sensor 10 in step S2, the corrected intake restart timing is calculated by the intake restart timing correction map.
Based on the value detected by the engine load sensor 10 and the engine speed sensor 11 in step S3, the corrected intake resumption period is calculated by the intake resumption period correction map.
Based on the value detected by the engine load sensor 10 and the engine speed sensor 11 in step S4, the corrected intake restart valve lift amount is calculated from the intake restart valve lift correction map.
In step S5, the ECU 20 executes a program for changing the intake resumption timing, changing the intake resumption engine, and changing the intake resumption valve lift amount.

On the other hand, in the control of the late post injection, the late post injection timing is calculated by the late post injection timing map based on the value detected by the engine speed sensor 11 and the engine load sensor 10 in step S7. Based on the value detected by the engine load sensor 10 and the engine speed sensor 11 in step S8, the late post injection is calculated by the late post injection amount map in step S6. The control content and late post injection control are merged, and late post injection is performed in step S10.
In step S11, the late post injection end timing is calculated, and in step S12, the intake resumption timing is changed so that the intake resumption timing is secured at a constant interval β (deg) (crank angle) from the late post injection end timing. This is to secure the amount of internal EGR gas necessary for NOx reduction.
In step S13, the intake resumption period and the intake resumption valve lift amount are changed. This is also to secure the amount of internal EGR gas necessary for NOx reduction.

Step S14 calculates the temperature of the DPF 6 from the temperature detected by the second temperature sensor 62 of the exhaust gas entering the DPF 6 in Step S15 and the temperature detected by the third temperature sensor 63 on the exhaust gas outlet side of the DPF 6. The target DPF temperature for DPF regeneration is compared.
In the case of No, the process returns to step S9, and the late post injection amount is corrected. When the temperature of the DPF 6 is lower than the target temperature, the late post injection amount X (the spotted portion in FIG. 6) is increased, and when it is higher, the late post injection amount is decreased.
However, since the interval β (deg) between the late post end timing and the resumption of intake air is maintained constant, the resumption of intake air is delayed.

Again, in step S6, the control content of the intake resumption valve and the late post injection control are merged, and late post injection is performed in step S10.
After steps S11, 12, and 13, it is determined in step S14 whether the temperature of the DPF 6 is the target temperature. When the temperature of the DPF 6 is not equal to the target temperature, the late post injection amount adjustment control is repeatedly performed.
If the temperature of the DPF 6 has reached the target temperature in step S14, the process proceeds to step S16 as Yes, and the temperature control of the DPF 6 ends.

In this way, even when the late post injection amount and the injection timing change depending on the operating state of the engine, the valve lift amount for resuming the intake air is changed while suppressing the torque fluctuation, so the exhaust amount of the internal EGR is required. The amount can be secured and NOx can be reduced.
As an example, an engine equipped with an internal EGR device has been described. However, as shown in FIG. 1, it can be used together with an external EGR.

  It is suitable for reducing NOx emissions in exhaust gas from a diesel engine equipped with an internal EGR device and for use in a DPF regeneration device by late post injection.

DESCRIPTION OF SYMBOLS 1 Engine 2 Fuel-injection apparatus 5 Oxidation catalyst 6 Particulate filter (DPF)
7 Turbocharger 18, 19, 20 ECU (control device)
DESCRIPTION OF SYMBOLS 11 Engine rotation sensor 12 Exhaust pipe 61 1st temperature sensor 62 2nd temperature sensor 63 3rd temperature sensor

Claims (6)

A diesel engine equipped with an internal EGR device that performs late post-injection performed during DPF regeneration to regenerate a DPF device that captures diesel exhaust particulates in exhaust gas and performs internal EGR by an intake valve that is temporarily lifted during the exhaust stroke In the torque fluctuation suppression control method,
The late post-injection is performed at an early stage during the exhaust valve opening period of the diesel engine, and a small lift of the intake valve that performs the internal EGR is opened near the lift apex of the exhaust valve, and the exhaust valve starts to close. A method for controlling torque fluctuation suppression of a diesel engine, characterized in that the closing timing is midway until closing, and the late post injection end timing does not overlap with the intake valve opening period of the internal EGR device.   2. The method for controlling torque fluctuation suppression of a diesel engine according to claim 1, wherein the late post-injection timing is performed when the torque fluctuation rate during the exhaust stroke of the engine is lowest.   2. The torque fluctuation of the diesel engine according to claim 1, wherein the operation of the intake valve of the internal EGR has at least one of an expansion of an opening period, an increase of a lift amount, or a change of an opening timing. Suppression control method. A diesel engine equipped with an internal EGR device that performs late post-injection performed during DPF regeneration to regenerate a DPF device that captures diesel exhaust particulates in exhaust gas and performs internal EGR by an intake valve that is temporarily lifted during the exhaust stroke In the torque fluctuation suppression control device,
The late post injection amount determining means having a map for calculating the late post injection amount from the rotational speed of the diesel engine and the fuel injection amount, and the late post injection timing from the rotational speed of the diesel engine and the fuel injection amount. Late post injection timing determining means, late post injection amount determining means, late post injection end timing calculating means for calculating late post injection end timing based on the calculated values of the late post injection timing determining means, and the late post Intake resumption timing determining means for calculating a resumption timing at which the intake valve of the internal EGR device does not overlap with the late post injection end time based on the calculation result of the injection end time calculation means, and the exhaust valve is opened to the late post injection During the initial period of the period, The small lift of the intake valve for the EGR opening lift near the vertex of the exhaust valve, as the timing of closing in the middle to close from the exhaust valve begins to close, the intake valve of the late post-injection end timing and the internal EGR device A torque fluctuation suppression control device for a diesel engine, characterized in that the opening period does not overlap.   The intake resumption timing determining means, the intake resumption period determining means for calculating the intake resumption period from the rotational speed and fuel injection amount of the diesel engine, and the valve lift amount of the intake resumption valve from the rotational speed and fuel injection amount of the diesel engine Based on the calculated values of the intake resumption valve lift amount determining means, the intake resumption timing determining means, the intake resumption period determining means, and the intake resumption valve lift amount determining means. 5. The torque fluctuation suppression of a diesel engine according to claim 4, further comprising variable valve timing means for driving the intake resumption valve based on the drive control content, and ensuring the internal EGR gas amount. Control device.   DPF temperature detection means for detecting the temperature of the DPF device, and late post injection amount correction means for correcting the late post injection amount so that the detected temperature detected by the DPF temperature detection means becomes a target temperature. The torque fluctuation suppression control device for a diesel engine according to claim 5.

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