JP2016223360A - Control device for engine - Google Patents

Abstract

The present invention relates to an engine control device that suppresses torque reduction immediately after the engine operating state is switched from normal combustion to purge processing. An engine includes an injection valve that injects fuel into a cylinder, and a catalyst that absorbs a predetermined component in exhaust gas in an oxidizing atmosphere and releases and reduces it in a reducing atmosphere. The control device 1 determines whether or not a purge process for releasing and reducing a predetermined component from the catalyst 32A is necessary, and in the purge process, after the main injection amount Qm in the main injection and the main injection are completed. A setting unit 4 that sets an injection ratio with the post injection amount Qp in post injection that can contribute to the torque, and each fuel of the main injection amount Qm and the post injection amount Qp according to the injection ratio is supplied from the injection valve 12 to a predetermined amount. And a control unit 7 that performs the purge process by injecting each at the injection timing. The setting unit 4 sets the injection ratio based on the amount of deviation between the target injection pressure PpTGT of the injection valve 12 and the actual injection pressure PACT in the purge process. [Selection] Figure 1

Description

  The present invention relates to an engine control apparatus having a catalyst in an exhaust passage, and performs a purge process for releasing and reducing predetermined components in exhaust stored by the catalyst.

Conventionally, as one of catalysts applied to engine exhaust purification systems, NOx trap catalysts (storage reduction catalysts) for purifying nitrogen oxides (hereinafter referred to as NOx) contained in exhaust gas have been widely used. . The NOx trap catalyst stores NOx in exhaust under a lean atmosphere (oxidizing atmosphere), releases the stored NOx under a rich atmosphere (reducing atmosphere), and reacts NOx with hydrocarbon components to react with nitrogen ( N ₂ ).

  In an engine equipped with a NOx trap catalyst, a purge process for releasing and reducing NOx from the NOx trap catalyst is appropriately performed according to the amount of stored NOx. The purge process is a process of releasing and reducing NOx stored in the NOx trap catalyst by switching the exhaust air-fuel ratio from lean to rich, and is also called NOx purge. As a method for switching the air-fuel ratio from lean to rich, for example, a method of injecting fuel at a predetermined injection timing after the main injection in addition to the main injection, a method of reducing the intake air, and the like can be cited (see Patent Document 1). ).

Japanese Patent No. 5115869

  By the way, in the purge process described above, the target value of the fuel injection pressure is set higher than that during normal combustion so that a predetermined amount of fuel is injected in a short time and the fuel is easily burned. However, since the actual injection pressure (actual injection pressure) gradually increases toward the target value, the actual injection pressure is smaller than the target value immediately after switching from the normal combustion to the purge process. As a result, immediately after switching to the purge process, it is difficult to spray a predetermined amount of fuel, and torque may be reduced because the fuel is difficult to burn.

  Note that the NOx trap catalyst has a property of storing sulfur components in the exhaust gas, and the stored sulfur components are released and removed from the NOx trap catalyst by performing a purge process called S purge. In this S purge, although the catalyst temperature is higher than that in the NOx purge, the exhaust air-fuel ratio is switched from lean to rich as in the NOx purge. For this reason, even immediately after the operating state of the engine is switched from the normal combustion to the S purge, there is a possibility that the torque down may occur as described above.

  The present case has been devised in view of such problems, and an object of the engine control device is to suppress a torque reduction immediately after switching the engine operating state from the normal combustion to the purge process. The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) An engine control device disclosed herein includes an injection valve that injects fuel into a cylinder, and a catalyst that occludes a predetermined component in exhaust gas under an oxidizing atmosphere and reduces it under a reducing atmosphere. It is a control device. The control device includes a determination unit that determines whether or not a purge process for reducing the predetermined component from the catalyst is necessary, and in the purge process, the main injection amount in the main injection, the torque after the completion of the main injection, A setting unit that sets an injection ratio with a post injection amount in post injection that can contribute to the post injection. In addition, a control unit is provided that performs the purge process by injecting each fuel of the main injection amount and the post injection amount according to the injection ratio from the injection valve at a predetermined injection timing. The setting unit sets the injection ratio based on a deviation amount between a target injection pressure of the injection valve and an actual injection pressure in the purge process.

  The deviation amount is a parameter that represents a deviation between the target injection pressure and the actual injection pressure. For example, the difference between the target injection pressure and the actual injection pressure, the target injection pressure, and the actual injection pressure This includes this ratio. The ratio includes the ratio of the actual injection pressure to the target injection pressure, the ratio of the change amount of the actual injection pressure to the change amount of the target injection pressure before and after the purge process, and the ratio before and after the purge process. A ratio of a difference between the target injection pressure and the actual injection pressure with respect to a change amount of the target injection pressure is included.

(2) It is preferable that the setting unit fixes the injection ratio to a preset predetermined injection ratio when the actual injection pressure converges to the target injection pressure.
For example, it is preferable that the setting unit fixes the injection ratio after the actual injection pressure has caught up to the target injection pressure.
(3) It is preferable that the setting unit changes the injection ratio such that the main injection amount increases as the deviation amount increases.
For example, it is preferable that the setting unit increases the ratio of the main injection amount as the deviation amount increases.

(4) The control device includes: an acquisition unit that acquires the temperature in the cylinder at the start of the purge process; and a correction unit that increases the main injection amount as the temperature acquired by the acquisition unit is lower. It is preferable to provide.
(5) It is preferable that the acquisition unit estimates and acquires the temperature based on a duration of low-load operation of the engine.

(6) It is preferable that the engine has a fuel cut function for cutting off fuel supply from the injection valve when a predetermined condition is satisfied. In this case, it is preferable that the acquisition unit estimates and acquires the temperature based on a time when the fuel supply is cut off.
(7) It is preferable that the said acquisition part estimates and acquires the said temperature based on the cooling water temperature of the said engine.
(8) It is preferable that the correction unit increases the main injection amount and decreases the post injection amount as the temperature acquired by the acquisition unit is lower.

  According to the disclosed engine control device, it is possible to suppress a torque decrease immediately after the engine operating state is switched from the normal combustion to the purge process.

It is a mimetic diagram showing composition of an engine to which a control device of an embodiment is applied. It is an example of a flowchart which shows the control procedure of NOx purge. 3 is a sub-flowchart of FIG. (A) is a graph which shows the change of the injection pressure when the operation state of an engine is switched from normal combustion to NOx purge, (b), (c) is the injection set based on the deviation | shift amount of injection pressure It is a figure for demonstrating a ratio and the injection quantity.

  An engine control apparatus as an embodiment will be described with reference to the drawings. The embodiment described below is merely an example, and there is no intention of excluding various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit of the present embodiment, and can be selected or combined as necessary.

[1. Device configuration]
The control device 1 of the present embodiment is applied to a diesel engine 10 (hereinafter referred to as the engine 10) mounted on a vehicle. FIG. 1 shows one of a plurality of cylinders 11 provided in a multi-cylinder engine 10. A piston is slidably housed in the cylinder 11, and the reciprocating motion of the piston is converted into the rotational motion of the crankshaft via the connecting rod.

  An in-cylinder injection valve 12 that directly injects fuel into the cylinder 11 is provided as an injector for supplying fuel to each cylinder 11. The amount of fuel injected from the in-cylinder injection valve 12, its injection timing (injection start time), and its injection period are controlled by the control device 1. For example, a control pulse signal is transmitted from the control device 1 to the in-cylinder injection valve 12, and the injection hole of the in-cylinder injection valve 12 is opened only during a period (injection period) corresponding to the magnitude of the control pulse signal. As a result, the fuel injection amount and the injection period correspond to the magnitude (drive pulse width) of the control pulse signal, and the injection timing corresponds to the time when the control pulse signal is transmitted.

  The in-cylinder injection valve 12 is connected to a variable flow rate fuel pump 14 through a fuel supply path 13 including a common rail 13A. The fuel pump 14 operates by receiving a driving force from the engine 10 or an electric motor, and discharges the fuel in the fuel tank to the fuel supply path 13. As a result, the fuel pressurized by the fuel pump 14 is supplied from the fuel supply path 13 to the common rail 13A and stored, and supplied to each cylinder 11 at the timing when the injection hole of the in-cylinder injection valve 12 is opened. . The amount of fuel discharged from the fuel pump 14 and the pressure in the common rail 13A (the injection pressure of the in-cylinder injection valve 12) are controlled by the control device 1.

  The engine 10 of the present embodiment has a fuel cut function that shuts off the fuel supply from the in-cylinder injection valve 12 when a predetermined condition is satisfied. This predetermined condition is, for example, that the vehicle speed is relatively high, the accelerator pedal is not depressed, and the engine brake is operating. On the other hand, when the accelerator pedal is depressed during the fuel cut, or when the engine rotation speed is lowered to a relatively low rotation range, the fuel cut ends. At this time, the fuel supply to the engine 10 is resumed, and the torque (engine output) corresponding to the idle rotation speed and the accelerator operation amount is ensured.

  An intake port 15 and an exhaust port 16 are provided on the top surface of each cylinder 11, and an intake valve 17 and an exhaust valve 18 are provided at the respective port openings. An intake manifold 20 (hereinafter referred to as intake manifold 20) is provided on the upstream side of the intake port 15, and the intake manifold 20 is provided with a surge tank 21 for temporarily storing air flowing to the intake port 15 side. A throttle body (not shown) incorporating an electronically controlled throttle valve 22 is connected to the upstream end of the intake manifold 20, and the amount of intake air flowing toward the intake manifold 20 according to the opening (throttle opening) of the throttle valve 22. Is adjusted. The throttle opening is controlled by the control device 1. An intake passage 23 is connected to the upstream side of the throttle body. An air filter 24 is provided at the uppermost stream of the intake passage 23.

On the other hand, an exhaust manifold 30 (hereinafter referred to as an exhaust manifold 30) is provided on the downstream side of the exhaust port 16, and an exhaust passage 31 is connected to the downstream end of the exhaust manifold 30.
Further, the engine 10 is provided with a turbocharger 25 that is interposed over both the intake passage 23 and the exhaust passage 31 and supercharges intake air using exhaust pressure. Further, an intercooler 26 is provided in the intake passage 23 on the downstream side of the compressor of the turbocharger 25 to cool the compressed intake air.

  The engine 10 according to the present embodiment is provided with an EGR passage 27 that recirculates exhaust gas flowing through the exhaust passage 31 to the intake passage 23. The EGR passage 27 communicates the exhaust passage 31 upstream of the turbine of the turbocharger 25 and the intake passage 23 downstream of the compressor. On the EGR passage 27, an EGR cooler 28 for cooling the EGR gas flowing through the EGR passage 27 and an EGR valve 29 for adjusting the flow rate of the EGR gas are provided.

An exhaust gas purification device 32 that purifies the exhaust gas is interposed downstream of the turbine in the exhaust passage 31. The exhaust purification device 32 includes a catalyst 32A and a filter 32B. The catalyst 32A occludes NOx (predetermined component) in the exhaust as nitrate on the support in an oxidizing atmosphere (the air-fuel ratio of the exhaust is leaner than the stoichiometric air-fuel ratio), and in a reducing atmosphere (the air-fuel ratio of the exhaust is theoretical). This is a NOx trap catalyst that releases NOx stored in a state richer than the air-fuel ratio) and reduces the NOx to N ₂ by reacting NOx with a hydrocarbon component. The filter 32B is a porous filter that collects particulate matter in the exhaust.

  The amount of NOx that can be occluded (maximum amount) is determined in the catalyst 32A, and when the amount of occluded NOx (hereinafter referred to as NOx occlusion amount As) approaches the maximum amount (saturated state), the occlusion ability decreases. Therefore, when the NOx occlusion amount As approaches the maximum amount, a purge process (NOx purge) for releasing and reducing NOx from the catalyst 32A is performed. The catalyst 32A has a property of storing a sulfur component (predetermined component) in the exhaust gas. If a large amount of this sulfur component is occluded in the catalyst 32A, the NOx occlusion capacity of the catalyst 32A will decrease, so a purge process (S purge) for releasing and removing the sulfur component from the catalyst 32A is appropriately performed. These purge processes are performed by the control device 1.

  A rotation speed sensor 33 that detects the rotation speed of the engine 10 is provided in the vicinity of the crankshaft. A cooling water temperature sensor 34 that detects the cooling water temperature (water temperature WT) of the engine 10 is provided at an arbitrary position on the cooling water circulation path of the engine 10. Furthermore, an upstream side of the catalyst 32A in the exhaust passage 31 is provided with an air-fuel ratio sensor 35 for detecting the air-fuel ratio of the exhaust and an exhaust temperature sensor 36 for detecting the exhaust temperature.

The common rail 13A is provided with an injection pressure sensor 37 that detects a common rail pressure (also simply referred to as an actual injection pressure _PACT ) corresponding to the pressure of the fuel injected from the in-cylinder injection valve 12. Further, an air flow sensor 38 for detecting the intake air amount is provided downstream of the air filter 24 in the intake passage 23. Various information detected by the various sensors 33 to 38 is transmitted to the control device 1. In addition to these sensors 33 to 38, the engine 10 includes an accelerator position sensor that detects the amount of depression of the accelerator pedal, an intake pressure and temperature, and an intake air pressure that detects the air-fuel ratio downstream of the catalyst 32A. An atmospheric pressure sensor, an intake air temperature sensor, a downstream air-fuel ratio sensor, and the like are provided.

  A vehicle equipped with the above-described engine 10 is provided with a control device 1 that comprehensively controls a wide range of systems such as an ignition system, a fuel system, and an intake / exhaust system related to the engine 10. The control device 1 is configured as, for example, an LSI device or an embedded electronic device in which a microprocessor, ROM, RAM, and the like are integrated, and is connected to a communication line of an in-vehicle network network provided in the vehicle. The control device 1 controls the amount of air supplied to each cylinder 11 of the engine 10, the fuel injection amount, the supercharging pressure, and the like.

  The various sensors 33 to 38 described above are connected to the input port of the control device 1. Specific control objects of the control device 1 include the fuel injection amount and the injection timing and injection period injected from the in-cylinder injection valve 12, the operating state of the turbocharger 25, the throttle opening, the opening of the EGR valve 29, and the like. Is mentioned. In the present embodiment, the NOx purge for releasing and reducing NOx in the purge process for the catalyst 32A will be described in detail.

[2. Control configuration]
In the NOx purge, the intake air is throttled and fuel as a reducing agent is supplied to the catalyst 32A by post injection from the in-cylinder injection valve 12. That is, in the NOx purge, the throttle opening is made smaller than that in normal combustion, the fuel injection amount in the post injection (hereinafter referred to as the post injection amount Qp) is increased, and the fuel injection amount in the main injection (hereinafter referred to as the fuel injection amount). The main injection amount Qm) is reduced. As a result, the atmosphere around the catalyst 32A is reduced to a reducing atmosphere (rich atmosphere), and the temperature of the catalyst 32A is raised to remove NOx.

  Post injection here is one of the fuel injection modes for carrying out and promoting the purge process of the catalyst 32A, and is also called after injection or early post injection. The post-injection fuel is injected at a timing later than the main injection (with a predetermined interval from the completion of the main injection). Therefore, the injected fuel does not burn completely in the cylinder 11, and only a part contributes to the torque. The fuel that has not burned in the cylinder 11 raises the exhaust temperature by a combustion reaction in the exhaust manifold 30 or the exhaust passage 31, or is supplied to the exhaust purification device 32 to form a reducing atmosphere.

  The magnitude of the torque generated by the post injection varies depending on the in-cylinder temperature and the fuel injection timing. For example, when the in-cylinder temperature is low, such as immediately after the start of the purge process, the torque generation amount is relatively small, and the torque generation amount increases as the in-cylinder temperature rises. Further, the later the injection timing of post-injection, the “afterburning tendency” becomes stronger, the amount of fuel contributing to torque decreases, and the amount of torque generated decreases. On the contrary, as the injection timing is earlier, the proportion of the torque contribution in the total injection amount of the post injection increases, and the torque generation amount increases. The post injection period in the present embodiment is set after the completion of the main injection and within a period up to about 120 ° after compression top dead center (ATDC). Hereinafter, the period during which the post injection is performed is referred to as a post injection period kp.

  On the other hand, the main injection is an injection method in which the injected fuel basically burns completely and contributes to the torque. A fuel injection method in which fuel is injected only near the compression top dead center, or before the compression top dead center This includes a method of injecting fuel into multiple times depending on the timing and the vicinity of the compression top dead center. The execution period of the main injection in this embodiment is set in advance at a predetermined timing. Hereinafter, a period during which the main injection is performed is referred to as a main injection period km.

After a predetermined specified time has elapsed since switching from normal combustion to NOx purge, the throttle valve 22 is controlled to a preset throttle opening to throttle the intake air. Thereafter, the target injection pressure P _TGT of the in-cylinder injection valve 12 is changed from the target injection pressure Pn _TGT during normal combustion to the target injection pressure Pp _TGT during NOx purge. Further, the target value (target air-fuel ratio) of the exhaust air-fuel ratio is gradually changed so as to become a target air-fuel ratio (for example, 14) in a preset NOx purge from the value during normal combustion. The target injection pressure Pp _TGT for the NOx purge is higher than the target injection pressure Pn _{TGT for} normal combustion. As described above, by increasing the target injection pressure Pp _TGT in the NOx purge, the fuel can be burned more easily and a predetermined amount of fuel can be injected in a short time. The target injection pressure P _TGT is switched in steps from the target injection pressure Pn _TGT during normal combustion to the target injection pressure Pp _TGT during NOx purge.

Immediately after switching from normal combustion to NOx purge, the target injection pressure P _TGT is increased stepwise, but the actual injection pressure P _ACT gradually increases, so the target injection pressure Pp _TGT and the actual injection pressure P Deviation occurs from _ACT . In the state (state the actual injection pressure P _ACT is not converged to the target injection pressure Pp _TGT), since that as possible Spray a predetermined amount of fuel in a short time difficult, insufficient contributes fuel amount to the torque, the torque Down might occur. Further, in a state where the injection pressure is deviated, the atomization of the post-injected fuel is poor and the post-injected fuel is difficult to burn, which may cause a torque reduction.

Further, in the NOx purge, the temperature in the cylinder 11 (hereinafter referred to as the in-cylinder temperature Tc) is set higher than that in the normal combustion so that the post-injected fuel is easily combusted. However, immediately after switching to the NOx purge, since the in-cylinder temperature Tc has not been raised to a temperature suitable for the NOx purge, the post-injected fuel is difficult to burn, and this may cause a torque reduction.
In view of these problems in the NOx purge, the control device 1 of the present embodiment controls the injection ratio of main injection and post injection in order to suppress the occurrence of torque reduction immediately after switching from normal combustion.

  As shown in FIG. 1, the control device 1 includes an estimation unit 2, a determination unit 3, a setting unit 4, an acquisition unit 5, a correction unit 6, and a control unit 7. Each of these elements may be realized by an electronic circuit (hardware), may be programmed as software, or some of these functions are provided as hardware, and the other part is software. It may be a thing.

  The estimation unit 2 estimates the NOx occlusion amount As of the catalyst 32A. Various known techniques can be applied to the method for estimating the NOx occlusion amount As. For example, it can be estimated based on the operating state of the engine 10, the exhaust temperature, the air-fuel ratio, the flow rate, and the like. The estimation unit 2 always estimates the NOx occlusion amount As and transmits the result to the determination unit 3 when the main power supply of the vehicle is on.

  The determination unit 3 performs three determinations: determination as to whether or not NOx purge is necessary, determination as to whether or not the engine 10 is in an operating state in which NOx purge can be performed, and determination as to completion of NOx purge. The determination unit 3 first compares the NOx occlusion amount As transmitted from the estimation unit 2 with a predetermined first threshold value A1, and determines that NOx purge is necessary if As ≧ A1, and if As <A1, If NOx purge, it is determined that no NOx purge is required. The first threshold value A1 is a threshold value for determining whether or not the NOx occluded in the catalyst 32A needs to be removed (saturated state of the catalyst 32A). The capacity of the catalyst 32A, the operating state of the engine 10, etc. Is set in advance based on

  When the determination unit 3 determines that the NOx purge is necessary, the determination unit 3 determines whether the engine 10 is in an operation state in which the NOx purge can be performed based on the load, rotation speed, exhaust temperature, and the like of the engine 10. . When it is determined that the engine 10 is in an operation state in which NOx purge can be performed, the determination result is transmitted to the setting unit 4 and the control unit 7. On the other hand, when it is determined that the engine 10 is not in an operation state in which the NOx purge can be performed, this determination is repeated.

  The determination unit 3 compares the NOx occlusion amount As transmitted from the estimation unit 2 with a predetermined second threshold A2 when NOx purge is started by the control unit 7 described later. The determination unit 3 determines that the NOx purge has been completed if As <A2, transmits the determination result to the control unit 7, and again determines necessity. On the other hand, if As ≧ A2, it is determined that the NOx purge is not completed, and this determination is repeated. The second threshold A2 is a threshold for determining whether or not NOx occluded in the catalyst 32A has been removed, and is set in advance to a value smaller than the first threshold A1.

  The setting unit 4 sets the main injection amount Qm and the post injection amount Qp in the NOx purge. When the determination result that the engine 10 is in an operation state in which the NOx purge can be performed is transmitted from the determination unit 3 to the setting unit 4 of the present embodiment, the total injection that is the total fuel injection amount in one combustion cycle. The amount Qt is calculated, and the injection ratio between the main injection amount Qm and the post injection amount Qp is set. Then, the main injection amount Qm and the post injection amount Qp are set from the total injection amount Qt and the injection ratio, and the set main injection amount Qm and post injection amount Qp are transmitted to the correction unit 6.

Specifically, the setting unit 4 calculates the total injection amount Qt based on the fuel amount Qn immediately before switching to the NOx purge, the target air-fuel ratio during the NOx purge, and the intake air amount detected by the air flow sensor 38. The setting unit 4 also sets the injection ratio based on the amount of deviation between the target injection pressure Pp _TGT during the NOx purge and the actual injection pressure detected by the injection pressure sensor 37 (hereinafter referred to as the actual injection pressure _PACT ). In addition, when the actual injection pressure P _ACT converges to the target injection pressure Pp _TGT , the injection ratio is fixed to a predetermined injection ratio set in advance.

This deviation amount is a parameter that represents the deviation between the target injection pressure Pp _TGT and the actual injection pressure P _ACT immediately after the switching described above. For example, the difference ΔP (= Pp _TGT between the target injection pressure Pp _TGT and the actual injection pressure P _ACT -P _ACT ) and the ratio between the target injection pressure Pp _TGT and the actual injection pressure P _ACT . This ratio includes the ratio of the actual injection pressure P _ACT to the target injection pressure Pp _TGT (P _ACT / Pp _TGT ) and the change in the actual injection pressure P _ACT relative to the amount of change in the target injection pressure P _TGT before and after the NOx purge. The ratio [ΔP _ACT / (Pp _TGT -Pn _TGT )] or the ratio of the difference between the target injection pressure Pp _TGT and the actual injection pressure P _ACT to the amount of change in the target injection pressure P _TGT before and after the NOx purge [( Pp _TGT -P _ACT ) / (Pp _TGT -Pn _TGT )]. In the present embodiment, as the deviation amount, using a difference ΔP between the target injection pressure Pp _TGT and the actual injection pressure P _ACT.

Examples of the method for setting the injection ratio between the main injection amount Qm and the post injection amount Qp include the following two methods.
(A) The ratio R (= Qp / Qm) of the post injection amount Qp to the main injection amount Qm is set.
(B) Ratio Rm (= Qm / Qt) of main injection quantity Qm to total injection quantity Qt, relative to total injection quantity Qt
The ratio Rp (= Qp / Qt) of the post injection quantity Qp is set (where Rm + Rp = 1).

In the case of (A), the setting unit 4 increases the ratio R so that the ratio R becomes lower than the predetermined ratio Ro as the difference ΔP increases (the ratio R increases within the range of the predetermined ratio Ro or less as the difference ΔP decreases). Set to get closer to the predetermined ratio Ro). Then, set the ratio R to a predetermined ratio Ro at the actual injection pressure P _ACT has converged to the target injection pressure Pp _TGT (difference ΔP becomes substantially zero) point, then fixed to a predetermined ratio Ro. The predetermined ratio Ro is the ratio when the actual injection pressure P _ACT has converged to the target injection pressure Pp _TGT, is set in advance based on the target air-fuel ratio in the NOx purge, the throttle opening, the cylinder temperature Tc, etc. . That is, when the difference ΔP is substantially zero, the setting unit 4 fixes the ratio R at the predetermined ratio Ro, and changes the ratio R so that the main injection amount Qm increases as the difference ΔP increases.

The setting unit 4 calculates and sets the main injection amount Qm from the total injection amount Qt and the ratio R as shown in Equation 1 below. Further, as shown in Expression 2, the post injection amount Qp is calculated and set by subtracting the main injection amount Qm from the total injection amount Qt.
Main injection quantity Qm = Qt / (1 + R) ... Equation 1
Post injection amount Qp = Qt−Qm (2)

  In the case of (B), the setting unit 4 sets the ratio Rm of the main injection amount Qm to be higher as the difference ΔP is larger, and when the difference ΔP becomes substantially zero, the ratios Rm and Rp are set. Each is set to a predetermined ratio set in advance. That is, also in this case, the setting unit 4 changes the ratio Rm from a predetermined ratio set when the difference ΔP is substantially zero so that the main injection amount Qm increases as the difference ΔP increases. The main injection amount Qm in this case is calculated as a value obtained by multiplying the total injection amount Qt by the ratio Rm (Qm = Qt × Rm). Note that the post injection amount Qp may be calculated as a value obtained by multiplying the total injection amount Qt by the ratio Rp, or the above equation 2 may be used.

Incidentally, the NOx purging, while the post injection amount Qp is increased as described above, at the time although the main injection amount Qm is reduced, the main injection amount Qm are the actual injection pressure P _ACT has converged to the target injection pressure Pp _TGT It is set to the minimum value Qmo. The minimum value Qmo is a value larger than zero, and is set in advance as a fixed value, for example. In the present embodiment, it is assumed that post injection is not performed in normal combustion immediately before switching to NOx purge.

That is, since the main injection amount Qm always includes the minimum value Qmo, the remaining injection amount obtained by subtracting the minimum value Qmo from the total injection amount Qt (hereinafter referred to as the allocation amount Qr. Qr = Qt-Qmo) The injection ratio allocated to the main injection and the post injection may be set.
As a method for setting the injection ratio in consideration of the minimum value Qmo, for example, there are the following two methods. Here, a value obtained by subtracting the minimum value Qmo from the main injection amount Qm is referred to as “variable main injection amount Qmx” (Qmx = Qm−Qmo).
(C) Set the ratio Rx (= Qp / Qmx) of the post injection quantity Qp to the variable main injection quantity Qmx
To do.
(D) The ratio Rmx (= Qmx / Qr) of the variable main injection amount Qmx to the allocation amount Qr, the allocation amount Qr
Set the ratio Rpx (Qp / Qr) of the post-injection amount Qp to each
(However, Rmx + Rpx = 1).

  In the case of (C), the allocation amount Qr is allocated to the variable main injection amount Qmx and the post injection amount Qp based on the ratio Rx. The setting unit 4 sets the ratio Rx to be lower as the difference ΔP is larger, and to increase the ratio Rx as the difference ΔP approaches zero, and sets the ratio Rx to a predetermined ratio set in advance when the difference ΔP becomes substantially zero. . That is, also in this case, the setting unit 4 changes the ratio Rx from the ratio set when the difference ΔP is substantially zero so that the main injection amount Qm (the variable main injection amount Qmx) increases as the difference ΔP increases. To do.

The setting unit 4 calculates the variable main injection amount Qmx from the allocation amount Qr and the ratio Rx, and sets the main injection amount Qm by adding the minimum value Qmo thereto as shown in the following expression 3. Further, the post injection amount Qp is set using the above equation 2.
Main injection quantity Qm = [Qr / (1 + Rx)] + Qmo

  In the case of (D), the setting unit 4 decreases the ratio Rmx from 100% to 0% as the difference ΔP decreases, and increases the ratio Rpx from 0% to 100%. That is, as the difference ΔP is larger, the ratio Rmx is set higher. When the difference ΔP becomes substantially zero, the ratio Rmx is set to 0% and the ratio Rpx is set to 100%. The main injection amount Qm in this case is calculated by adding the minimum value Qmo to the value obtained by multiplying the allocation amount Qr by the ratio Rmx (Qm = Qr × Rmx + Qmo). The post-injection amount Qp may be calculated as a value obtained by multiplying the allocation amount Qr by the ratio Rpx, or the above equation 2 may be used.

  The acquisition unit 5 acquires the in-cylinder temperature (hereinafter referred to as the start in-cylinder temperature Tcp) at the start point of the NOx purge (that is, immediately after switching to the NOx purge). When the starting in-cylinder temperature Tcp is low, the post-injected fuel becomes more difficult to burn and the temperature difference with respect to the temperature suitable for NOx purge becomes large. In this case, the in-cylinder temperature Tc tends to increase. In addition, the correction unit 6 described later corrects the main injection amount Qm and the post injection amount Qp set by the setting unit 4. Prior to this correction, the acquisition unit 5 acquires the starting in-cylinder temperature Tcp and transmits the acquired starting in-cylinder temperature Tcp to the correction unit 6.

As an acquisition method, there is a method of providing a sensor that directly detects the in-cylinder temperature Tc and detecting the start in-cylinder temperature Tcp. Further, there is a method for estimating the starting in-cylinder temperature Tcp using a parameter that can be related to the in-cylinder temperature Tc. The acquisition unit 5 of the present embodiment estimates and acquires the starting in-cylinder temperature Tcp based on at least one of the following three parameters.
(1) The duration LE of the low load operation of the engine 10
(2) Fuel cut time FC
(3) Water temperature WT detected by the cooling water temperature sensor 34

  The duration LE is a time during which low load operation such as idle operation is continued, and is counted by the control device 1. Since the in-cylinder temperature Tc decreases as the duration LE increases, the start in-cylinder temperature Tcp is estimated based on the duration LE by acquiring in advance the relationship between the duration LE and the amount or rate of decrease in temperature. Is possible. In this embodiment, at least when the end point of the duration LE is within the predetermined first period L1 before switching from normal combustion to NOx purge, the in-cylinder temperature Tcp is estimated. To do.

  That is, when the low load operation continues for a predetermined time and is switched from the low load operation to the NOx purge after carrying out the medium load or high load operation, at least a part of the low load operation duration LE goes to the NOx purge. If it is within the first period L1 before switching, the in-cylinder temperature Tcp is estimated based on the duration LE. On the other hand, if the duration LE is before the first period L1, the medium load or high load operation has been continued for the first period L1 or more, so the temperature drop due to the low load operation can be ignored. Thus, the in-cylinder temperature Tcp is not estimated based on the duration LE.

  The fuel cut time FC is a time when the fuel cut described above is performed (a time when the fuel supply is cut off), and is counted by the control device 1. Since the in-cylinder temperature Tc decreases as the fuel cut time FC becomes longer, the start in-cylinder temperature is determined based on the fuel cut time FC by acquiring in advance the relationship between the fuel cut time FC and the temperature decrease amount or rate of decrease. Tcp can be estimated. In the present embodiment, the start in-cylinder temperature Tcp is estimated when at least the end point of the fuel cut time FC is within the predetermined second period L2 before switching from normal combustion to NOx purge. And

  That is, if the fuel cut is continued for a predetermined time and then the fuel supply is resumed and then switched to the NOx purge, at least a part of the fuel cut time FC must be within the second period L2 before the switch to the NOx purge. For example, the in-cylinder temperature Tcp is estimated based on the fuel cut time FC. On the other hand, if the fuel cut time FC is earlier than the second period L2, it is considered that the temperature drop due to the fuel cut can be ignored because the fuel supply has been resumed and the second period L2 has passed. The start in-cylinder temperature Tcp is not estimated based on the fuel cut time FC. The first period L1 and the second period L2 are set in advance in consideration of the effects of the low load operation duration LE and the fuel cut time FC on the decrease in the in-cylinder temperature Tc.

  The water temperature WT is a parameter that has a positive correlation with the in-cylinder temperature Tc. By acquiring the relationship between the water temperature WT and the in-cylinder temperature Tc in advance, the start in-cylinder temperature Tcp can be estimated based on the water temperature WT. is there. The estimation of the in-cylinder temperature Tcp based on the water temperature WT can be performed regardless of time unlike the other parameters.

  The correction unit 6 performs correction so as to increase the main injection amount Qm set by the setting unit 4 and reduce the post injection amount Qp as the starting in-cylinder temperature Tcp acquired by the acquisition unit 5 is lower. As a result, the amount of fuel in the main injection that is more easily combusted increases, so the temperature in the cylinder 11 is likely to rise. On the other hand, by increasing the main injection amount Qm, the post-injection amount Qp is decreased to keep the total injection amount Qt constant, thereby suppressing fuel consumption deterioration. The correction unit 6 sets the corrected main injection amount Qm and post injection amount Qp as the main injection amount Qm ′ and post injection amount Qp ′, respectively, and transmits the values to the control unit 7.

As a correction method by the correction unit 6, for example, the relationship between the start in-cylinder temperature Tcp and the correction amount and correction ratio of the main injection amount Qm is set in advance as a map, and the start in-cylinder temperature Tcp transmitted from the acquisition unit 5 is set. A method for obtaining the correction amount and the correction ratio by applying to the map. The correction by the correction unit 6, the actual injection pressure P _ACT is only until it converges to the target injection pressure Pp _TGT (when there is a deviation only) may be carried out, the actual injection pressure P _ACT is the target The process may be continued even after the injection pressure Pp _TGT has converged. That is, the correction by the correction unit 6 can be performed independently from the control of the injection ratio of the main injection and the post injection. Further, even if the actual injection pressure P _ACT is not converged to the target injection pressure Pp _TGT, if the start cylinder temperature Tcp is lower than a predetermined temperature, may be carried out correction by the correction unit 6. That is, the fact that the NOx purge is performed is only a necessary condition for performing the correction by the correction unit 6. When the correction is not performed, the correction unit 6 sets the correction amount to zero and sets the values transmitted from the setting unit 4 as the main injection amount Qm ′ and the post injection amount Qp ′ as they are (Qm ′ = Qm). , Qp ′ = Qp).

The control unit 7 switches the operation state of the engine 10 from normal combustion to NOx purge when the determination result that the engine 10 is in an operation state in which the NOx purge can be performed is transmitted from the determination unit 3, and performs NOx purge. To implement. The controller 7 reduces the intake air amount by restricting the throttle valve 22 to a predetermined throttle opening after a specified time when switching to the NOx purge. Next, the target injection pressure P _TGT of the in-cylinder injection valve 12 is switched from the target injection pressure Pn _TGT during normal combustion to the target injection pressure Pp _TGT during NOx purge.

  Then, the control unit 7 uses the main injection amount Qm ′ and the post injection amount Qp ′ set by the correction unit 6 to inject fuel from the in-cylinder injection valve 12 at a predetermined injection timing, and within a predetermined injection period. Blow out the fuel. Specifically, in one combustion cycle, the fuel of the main injection amount Qm ′ is injected within the main injection period km, and the fuel of the post injection amount Qp ′ is injected within the post injection period kp. As a result, the temperature of the catalyst 32A is raised while reducing the atmosphere around the catalyst 32A, and NOx is released and reduced.

When the determination result that the NOx purge is completed is transmitted from the determination unit 3 during the execution of the NOx purge, the control unit 7 switches the operation state of the engine 10 from the NOx purge to the normal combustion, and ends the NOx purge. To do. When switching to normal combustion, the control unit 7 switches the target injection pressure P _TGT of the in-cylinder injection valve 12 from the target injection pressure Pp _TGT for NOx purge to the target injection pressure Pn _TGT for normal combustion. Then, normal engine control based on the output requested by the driver is performed.

[3. flowchart]
FIG. 2 is a flowchart for explaining the above-described control procedure of the NOx purge, and FIG. 3 is a sub-flowchart of FIG. The flow in FIG. 2 is started, for example, when the main power supply of the vehicle is switched from off to on, and is repeatedly executed in the control device 1 at a predetermined calculation cycle while the power is on. It is assumed that the operating state of the engine 10 is normal combustion and the flag Fp is set to Fp = 0 at the start of the flow of FIG. Further, it is assumed that the estimation unit 2 estimates the NOx occlusion amount As while the power is on.

  As shown in FIG. 2, in the control device 1, information (sensor values) detected by the sensors 33 to 38 is acquired (step S1), and when the flag Fp is Fp = 0 (step S2), the estimation unit The NOx occlusion amount As estimated in 2 is read (step S3). Here, the flag Fp is for determining whether or not the NOx purge is necessary. Fp = 1 corresponds to the state where the NOx purge is necessary, and Fp = 0 is the state where the NOx purge is not necessary. Correspond.

  When the NOx occlusion amount As is equal to or greater than the first threshold value A1 (As ≧ A1) (step S4), the flag Fp is set to Fp = 1 (step S5). On the other hand, if the NOx occlusion amount As is less than the first threshold A1, this flow is returned. That is, when the amount of NOx stored in the catalyst 32A is equal to or greater than the first threshold A1, it is determined that the NOx purge is necessary, and the process proceeds to the next determination. Next, when the engine 10 is in an operating state in which the NOx purge can be performed (step S6), the NOx purge of FIG. 3 described later is performed (step S7). Then, the NOx occlusion amount As estimated by the estimation unit 2 is read again (step S8).

  When the NOx occlusion amount As is not less than the second threshold value A2 (step S9), the process returns, the sensor value is acquired again (step S1), and flag determination is performed (step S2). In this case, since the flag Fp is set to Fp = 1, it is determined whether NOx purge can be performed (step S6). If practicable, the NOx purge is continued (step S7), and when As <A2 (step S9), the operating state of the engine 10 is switched from the NOx purge to the normal combustion (step S10), and the flag Fp is reset to Fp = 0 (step S11).

  On the other hand, when the engine 10 is in an operation state in which NOx purge cannot be performed (step S6), if NOx purge is being performed (step S12), the NOx purge is interrupted and the operation state of the engine 10 is switched to normal combustion. (Step S13), this flow is returned. In this case, since the flag Fp is set to Fp = 1, the NOx purge is returned when the engine 10 enters an operation state in which the NOx purge can be performed. If NOx purge is not being performed, this flow is returned as normal combustion.

When the routine proceeds to step S7, as shown in FIG. 3, the throttle valve 22 is controlled to the throttle opening in the NOx purge to throttle the intake air (step S20), and after the lapse of the specified time (step S21), The target injection pressure P _TGT of the in-cylinder injection valve 12 is set to the target injection pressure Pp _TGT during the NOx purge (step S22). Then, the actual injection pressure _PACT is acquired from the injection pressure sensor 37 (step S23).

Immediately after switching from normal combustion to NOx purge, a difference ΔP occurs between the target injection pressure Pp _TGT and the actual injection pressure P _ACT , so in a state where the actual injection pressure P _ACT has not converged to the target injection pressure Pp _TGT ( In step S24), the injection ratio is set based on the difference ΔP (step S26). On the other hand, when the actual injection pressure P _ACT has converged to the target injection pressure Pp _TGT (step S24), and the predetermined injection ratio injection ratio between the main injection amount Qm and the post injection amount Qp is set in advance (for example, a predetermined ratio Ro ) Is set (step S25).

  Then, the total injection amount Qt is calculated, and the main injection amount Qm and the post injection amount Qp are calculated and set using the set injection ratio (step S27). Next, the starting in-cylinder temperature Tcp is acquired by the acquisition unit 5 (step S28), the main injection amount Qm and the post injection amount Qp are corrected by the correction unit 6, and the main injection amount Qm 'and the post injection amount Qp' are set. (Step S29). Then, the fuel of the main injection amount Qm ′ is injected within the main injection period km, and the fuel of the post injection amount Qp ′ is injected within the post injection period kp (step S30).

[4. Action]
FIG. 4A is a graph showing a change in injection pressure when the operating state of the engine 10 is switched from normal combustion to NOx purge. FIGS. 4B and 4C show the deviation of the injection pressure. It is a figure for demonstrating the injection ratio and injection amount which are set based on quantity. In FIG. 4B, the ratio R of the post injection amount Qp to the main injection amount Qm described above is given as an injection ratio, and three graphs are illustrated.

As described above, when the operating state of the engine 10 is switched from normal combustion to NOx purge, the throttle valve 22 is controlled to throttle the intake air. As shown in FIG. 4 (a), when the intake air amount and the time t ₀ to the time below a predetermined value, at this time t _0, the target injection pressure Pn at the target injection pressure P _TGT is normal combustion shown by the one-dot chain line _{The TGT} is switched to the target injection pressure Pp _TGT during the NOx purge stepwise. The actual injection pressure P _ACT indicated by a solid line, begins to rise at time t ₁ with a slight delay from time t _0, and converges to the target injection pressure Pp _TGT to time t _2, the then target injection pressure Pp _TGT substantially coincides It will be in the state.

As shown in FIG. 4C, in the normal combustion immediately before switching to the NOx purge, the fuel amount Qn is main-injected and not post-injected. the ratio R up to time t ₁ is set to zero. The ratio R is in the time t ₁ and later increased as the difference ΔT between the target injection pressure Pp _TGT and the actual injection pressure P _ACT is reduced, is set to a predetermined ratio Ro at time t ₂ when the difference ΔP becomes substantially zero, Thereafter, the predetermined ratio Ro is fixed. The ratio R may be set so as to change in a curve as shown by a thin solid line or a one-dot chain line in FIG.

By allowing the ratio R is set in this manner, the main injection amount Qm and the post injection amount Qp is gradually changed from time t ₁ to time t _2, at the time t ₂ after being set to a constant value. Specifically, the main injection amount Qm shown by thin solid line is gradually reduced from the fuel quantity Qn, is set to the minimum value Qmo at time t _2. On the other hand, the post-injection amount Qp indicated by a thick solid line, gradually increased from zero, is set at time t ₂ from the total injection quantity Qt to a value obtained by subtracting the minimum value QMO. Setting the main injection amount Qm and the post injection amount Qp in this way prevents torque reduction immediately after the operating state of the engine 10 is switched to NOx purge. The total injection amount Qt indicated by the one-dot chain line is gradually increased from time t ₁ so that the air-fuel ratio becomes the target air-fuel ratio in the NOx purge at time t ₂ .

Incidentally, if at time t ₀ or time t _1, the main injection amount Qm is switched stepwise in minimum Qmo the fuel quantity Qn, post injection amount Qp from zero and is switched in steps to a predetermined amount. In this case, since the actual injection pressure P _ACT has not reached the target injection pressure Pp _TGT, it is difficult to as possible Spray a predetermined post injection amount Qp during the post-injection period kp, post injection amount Qp contributes to torque Run short. Further, since the main injection amount Qm is set to the minimum value Qmo, the main injection amount Qm contributing to the torque is also reduced. As described above, since the amount of fuel that contributes to the torque is small, there is a risk that a drop in torque may occur. In contrast, in the above-mentioned NOx purging, the target injection pressure Pp _TGT and the actual injection pressure to set the ratio R based on the difference ΔP between P _ACT, the main injection amount Qm and post set using the ratio R Since the fuel of the injection amount Qp is injected during the predetermined injection period km, kp, the occurrence of torque reduction is effectively suppressed.

[5. effect]
(1) the control device 1 described above, based on the amount of deviation between the target injection pressure Pp _TGT and the actual injection pressure P _ACT (e.g. the difference [Delta] P), the injection ratio (for example, the ratio of the main injection amount Qm and the post injection amount Qp R) is set, so that the injection ratio is set so that the fuel amount Qm in the main injection, where the fuel is easy to burn, increases in the fuel pressure transient state where the actual injection pressure P _ACT is changing to the target injection pressure Pp _TGT be able to. Accordingly, even when the actual injection pressure P _ACT has not reached the target injection pressure Pp _TGT, it is possible to suppress the torque-down immediately after switching from the normal combustion NOx purge.

  The fuel injection ratio can be controlled independently of the total injection amount Qt, which is the sum of the main injection amount Qm and the post injection amount Qp, and therefore depends on the size of the total injection amount Qt. Torque drop can be avoided. For example, even when the intake air amount fluctuates immediately after switching to NOx purge, the main injection amount Qm and the post injection amount Qp are simultaneously increased or decreased while keeping the actual air-fuel ratio following the target air-fuel ratio. Can do. Therefore, the operating state can be stabilized while the torque reduction of the engine 10 is suppressed.

(2) the control device 1 described above, when the actual injection pressure P _ACT has converged to the target injection pressure Pp _TGT, since injection ratio is fixed to a predetermined injection ratio that is set in advance, to simplify the control configuration be able to. Further, in the process of the actual injection pressure P _ACT converges to the target injection pressure Pp _TGT, since the injection ratio is controlled so as to approach the predetermined injection ratio, torque fluctuations and combustion before and after the time t ₂ in the FIG. 4 There is no risk of sudden changes in the state, and the operating state of the engine 10 can be further stabilized.

(3) Further, in the control device 1 described above, the injection ratio is set so that the main injection amount Qm increases as the deviation amount of the injection pressure increases (the ratio of the main injection amount Qm increases as the deviation amount increases). Be changed. In other words, the larger the deviation amount, the more fuel is injected by the main injection, where the fuel is more likely to burn, so even if there is a deviation between the target injection pressure Pp _TGT and the actual injection pressure P _ACT , normal combustion Torque reduction immediately after switching from NOx purge to NOx can be effectively suppressed.

  (4) In the control device 1 described above, the correction is made such that the main injection amount Qm is increased as the starting in-cylinder temperature Tcp acquired by the acquisition unit 5 is lower. It is possible to shorten the time until the in-cylinder temperature Tc is suitable for the case. Thereby, NOx occluded in the catalyst 32A is released and reduced at an early stage, and it is possible to suppress an increase in the purge processing time. Further, by increasing the inflammable main injection amount Qm and increasing the in-cylinder temperature Tc, the post-injected fuel is easily combusted, so that torque reduction can be suppressed more effectively.

  (5) Further, in the control device 1 described above, the main injection amount Qm is increased and the post injection amount Qp is decreased as the starting in-cylinder temperature Tcp is lower. That is, as the main injection amount Qm increases, the post injection amount Qp is reduced and the total injection amount Qt is kept constant, so that deterioration in fuel consumption can be suppressed.

  (6) In the control device 1 described above, the starting in-cylinder temperature Tcp is estimated from at least one of the three parameters of the low load operation duration LE, the fuel cut time FC, and the water temperature WT of the engine 10. For this reason, the main injection amount Qm can be corrected without a sensor that directly detects the in-cylinder temperature Tc, and the cost can be reduced. Further, the estimation accuracy can be improved by combining these parameters to estimate and acquire the starting in-cylinder temperature Tcp.

[6. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
In the above-described embodiment, the case where the difference ΔP is used as the deviation amount between the target injection pressure Pp _TGT and the actual injection pressure P _ACT is illustrated, but the deviation amount is not limited to this, and the actual injection pressure with respect to the target injection pressure Pp _TGT . it may amount deviation ratio of P _ACT. Alternatively, the ratio of the change amount of the actual injection pressure P _{ACT to} the change amount (Pp _TGT −Pn _TGT ) of the target injection pressure P _TGT before and after the purge process may be used as a deviation amount, or the target injection pressure before and after the purge process The ratio of the difference between the target injection pressure Pp _TGT and the actual injection pressure P _ACT with respect to the change amount of P _TGT (Pp _TGT −Pn _TGT ) may be used as the deviation amount.

  Further, the correction unit 6 may correct the main injection amount Qm so as to decrease as the starting in-cylinder temperature Tcp decreases, while keeping the post injection amount Qp constant (the correction amount is set to zero). In this case, since the total injection amount Qt increases, the exhaust air-fuel ratio can be converged to the target air-fuel ratio (for example, 14) in the NOx purge earlier. Note that the correction unit 6 described above is not essential and can be omitted. In other words, the control unit 7 may inject each fuel of the main injection amount Qm and the post injection amount Qp according to the injection ratio set by the setting unit 4 in the main injection period km and the post injection period kp, respectively. . In this case, the acquisition unit 5 can also be omitted, and the control configuration can be simplified.

  In the above-described embodiment, post-injection is not performed in normal combustion immediately before switching to NOx purge. However, the injection mode during normal combustion is not particularly limited, and post-injection may be performed. In this case, in setting the injection ratio when switching from normal combustion to NOx purge, the post injection amount during normal combustion may be taken into consideration. In the above-described embodiment, the case where the minimum value Qmo of the main injection amount Qm is set as a fixed value is exemplified, but the minimum value Qmo is not limited to this. For example, the ratio of the minimum value Qmo to the total injection amount Qt may be set in advance, and the minimum value Qmo may be calculated when the total injection amount Qt is calculated. That is, the minimum value Qmo may be given as a variable corresponding to the total injection amount Qt.

In the above-described embodiment, the NOx purge is exemplified as the purge process. However, the control related to the NOx purge described above may be applied to the S purge for releasing and removing the sulfur component from the catalyst 32A.
The engine 10 is not limited to the diesel engine having the above-described configuration, and may be a diesel engine having another configuration or a gasoline engine.

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Estimation part 3 Judgment part 4 Setting part 5 Acquisition part 6 Correction part 7 Control part 10 Engine 12 In-cylinder injection valve 32A Catalyst
FC fuel cut time
LE Low load operation duration
P _ACT Actual injection pressure
P _TGT target injection pressure
Target injection pressure during normal combustion of Pn _TGT
Pp _TGT Target injection pressure for NOx purge
Qm Main injection amount
Qp Post injection amount
Tc In-cylinder temperature
Tcp start cylinder temperature
WT Water temperature (cooling water temperature)
ΔP difference (deviation amount)

Claims (8)

An engine control device comprising: an injection valve that injects fuel into a cylinder; and a catalyst that occludes a predetermined component in exhaust gas under an oxidizing atmosphere and reduces it under a reducing atmosphere,
A determination unit that determines whether or not a purge process for reducing the predetermined component from the catalyst is necessary;
In the purge process, a setting unit that sets an injection ratio between a main injection amount in main injection and a post injection amount in post injection that can contribute to torque after completion of the main injection;
A controller that performs the purge process by injecting each fuel of the main injection amount and the post injection amount according to the injection ratio from the injection valve at a predetermined injection timing,
The engine control apparatus, wherein the setting unit sets the injection ratio based on a deviation amount between a target injection pressure of the injection valve and an actual injection pressure in the purge process. The engine control according to claim 1, wherein the setting unit fixes the injection ratio to a predetermined injection ratio set in advance when the actual injection pressure converges to the target injection pressure. apparatus. The engine control device according to claim 1, wherein the setting unit changes the injection ratio so that the main injection amount increases as the deviation amount increases. An acquisition unit for acquiring the temperature in the cylinder at the start of the purge process;
The engine control apparatus according to claim 1, further comprising: a correction unit that increases the main injection amount as the temperature acquired by the acquisition unit decreases. The engine control device according to claim 4, wherein the acquisition unit estimates and acquires the temperature based on a duration of low-load operation of the engine. The engine has a fuel cut function for cutting off fuel supply from the injection valve when a predetermined condition is satisfied,
The engine control apparatus according to claim 4 or 5, wherein the acquisition unit estimates and acquires the temperature based on a time when the fuel supply is cut off. The engine control apparatus according to any one of claims 4 to 6, wherein the acquisition unit estimates and acquires the temperature based on a coolant temperature of the engine. The engine according to claim 4, wherein the correction unit increases the main injection amount and decreases the post injection amount as the temperature acquired by the acquisition unit is lower. Control device.

Images