JP4114201B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine provided with a variable exhaust valve timing mechanism for changing the valve timing of an exhaust valve.
[0002]
[Prior art]
In recent years, the demand for in-cylinder injection engines that combine the features of low fuel consumption, low exhaust emissions, and high output has increased rapidly. This in-cylinder injection engine directly injects a small amount of fuel into the cylinder during a compression stroke when the load is low, and stratifies combustion of the air-fuel mixture during a high load, and increases the fuel injection amount to increase the amount of fuel injected into the cylinder during the intake stroke. Is directly injected to uniformly burn the mixture.
[0003]
In such an in-cylinder injection engine, for example, as shown in Patent Document 1 (Japanese Patent No. 3147770) and Patent Document 2 (Japanese Patent Laid-Open No. 10-103093), further improvements in fuel consumption, exhaust emission, and output are achieved. Aiming at this, some have a variable valve timing mechanism that changes the valve timing of intake and exhaust valves.
[0004]
By the way, in a cylinder injection engine that directly injects fuel into a cylinder, the time until the injected fuel reaches the exhaust port (hereinafter referred to as “injected fuel arrival time”) is very short. (Accurately, if the fuel injection start timing is earlier than the exhaust valve closing timing by the time when the injected fuel arrives), part of the injected fuel will be exhausted before the exhaust valve is closed. It reaches the port and is discharged to the exhaust pipe, resulting in a problem that exhaust emission deteriorates.
[0005]
As a countermeasure, in Patent Document 2 (Japanese Patent Laid-Open No. 10-103093), when the fuel injection start timing is advanced (becomes earlier) than a predetermined timing (exhaust valve closing timing), the exhaust valve closing is performed. By advancing (advancing) the timing, the exhaust valve is closed before the injected fuel reaches the exhaust port.
[0006]
[Patent Document 1]
Japanese Patent No. 3147770 (first page, etc.)
[Patent Document 2]
JP 10-103093 A (second page, etc.)
[0007]
[Problems to be solved by the invention]
In general, as shown in FIG. 11, the fuel injection start timing can be changed with little response delay according to the change in the target injection start timing. However, in the control of the exhaust valve timing, the fuel injection start timing is changed according to the change in the target exhaust valve timing. Because the time to drive the variable exhaust valve timing mechanism to the position corresponding to the target exhaust valve timing after the change is not negligible, control of the exhaust valve timing is considerably larger than the control of the fuel injection start timing. Occurs. The following problems occur due to the response delay of the exhaust valve timing control.
[0008]
For example, as shown in FIG. 10 (a), from the state where both the exhaust valve timing and the fuel injection start timing are retarded, as shown in FIG. 10 (c), both the exhaust valve timing and the fuel injection start timing are set. In both cases, the relationship between the exhaust valve timing and the fuel injection start timing in the state before the advance angle shown in FIG. 10A and the state after the advance angle shown in FIG. It is desirable to set so that the exhaust valve closes before reaching the exhaust port.
[0009]
In the conventional system, the exhaust valve timing and the fuel injection start timing are advanced from the position shown in FIG. 10A to the position shown in FIG. 10C. However, since the exhaust valve timing changes with a delay in response to the change in the target exhaust valve timing as shown in FIG. 11, the advance operation of the exhaust valve timing is completed. Until this time, as shown in FIG. 10B, the advance operation of the exhaust valve timing is delayed with respect to the advance operation of the fuel injection start timing, and the fuel injection start time and the exhaust valve opening period overlap. During that period, a part of the injected fuel passes through the gap of the exhaust valve before closing, and is discharged to the exhaust pipe. But problems occur that worse.
[0010]
In short, as in Patent Document 2 described above, when the fuel injection start timing is advanced from a predetermined timing (exhaust valve closing timing), control is performed to advance the exhaust valve closing timing, Due to the response delay of the variable exhaust valve timing mechanism, as shown in FIG. 10B, the advance operation of the exhaust valve timing is delayed with respect to the advance operation of the fuel injection start timing. Until completion, the injected fuel slips through and exhaust emission deteriorates.
[0011]
The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is to provide a control device for an internal combustion engine that can surely prevent the injected fuel from slipping through and improve exhaust emission. There is to do.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, claim 1 of the present invention controls the fuel injection timing of the fuel injection valve and the valve timing of the exhaust valve (hereinafter referred to as “exhaust valve timing”) according to the operating state of the internal combustion engine. In the system, When at least one of the exhaust valve timing and the fuel injection timing is advanced, Actual exhaust valve timing detected or estimated by the exhaust valve timing detection means Valve closing time Based on the above, the fuel injection timing is retarded by the injection timing correction means.
[0013]
In this way, in the process of advancing the exhaust valve timing and the fuel injection timing, while detecting that the actual exhaust valve timing is advanced with a response delay, the fuel injection timing is advanced in accordance with the response delay. The angular operation can be delayed, and the advance operation at the fuel injection timing can have a delay equivalent to the response delay of the actual exhaust valve timing. As a result, even during the transition period in which the exhaust valve timing and the fuel injection timing are advanced, the relationship between the exhaust valve timing and the fuel injection timing can be determined so that the closing timing of the exhaust valve is reached before the injected fuel reaches the exhaust port. It can be controlled to maintain, and it is possible to reliably prevent the injected fuel from slipping through and to improve the exhaust emission.
[0014]
Even when only one of the exhaust valve timing and the fuel injection timing is advanced, the relationship between the exhaust valve timing and the fuel injection timing can be determined by referring to the closing timing of the exhaust valve before the injected fuel reaches the exhaust port. The fuel injection timing can be appropriately retarded so as to maintain the greeted state, and injection fuel can be reliably prevented from passing through.
[0015]
As described above, the injected fuel may be discharged from the exhaust port when the fuel injection timing is advanced (earlier) than the exhaust valve closing timing. Therefore, as in claim 2, when the fuel injection timing is advanced from the exhaust valve closing timing detected based on the actual exhaust valve timing (the fuel injection timing overlaps with the exhaust valve opening period). The fuel injection timing may be retarded. In this way, when there is a possibility that the injected fuel may slip through, the fuel injection timing can be reliably retarded.
[0016]
In addition, when setting the retard correction amount of the fuel injection timing, if the minimum retard correction amount necessary to reach the closing timing of the exhaust valve before the injected fuel reaches the exhaust port is set, The effect of preventing the fuel from slipping through can be sufficiently obtained, and even if the retard correction amount of the fuel injection timing is increased further, the effect of preventing the fuel from slipping through has hardly changed, and adversely affects the combustibility. (The fuel injection timing must be set so as to ensure combustibility).
[0017]
Therefore, as in claim 3, the retardation correction amount of the fuel injection timing is set according to the difference between the fuel injection timing and the actual exhaust valve closing timing detected based on the actual exhaust valve timing. Anyway. In this way, it is possible to set the minimum amount of retardation correction required to reach the closing timing of the exhaust valve before the injected fuel reaches the exhaust port, minimizing the effect on combustibility. While suppressing, it is possible to prevent the injected fuel from slipping through, and it is possible to achieve both combustibility and prevention of the injected fuel from slipping through.
[0018]
Further, as described in claim 4, the retard correction amount of the fuel injection timing may be set according to the difference between the actual exhaust valve timing and the target exhaust valve timing. The greater the difference between the actual exhaust valve timing and the target exhaust valve timing, the longer the response delay time until the actual exhaust valve timing reaches the target exhaust valve timing (the period during which the injected fuel may slip through). Therefore, if the delay correction amount of the fuel injection timing is set according to the difference between the actual exhaust valve timing and the target exhaust valve timing, appropriate delay angle correction according to the response delay time of the actual exhaust valve timing The amount can be set, and the injected fuel can be prevented from slipping through while reducing the influence on the combustibility.
[0019]
Further, as in claim 5, when the actual exhaust valve timing is estimated, the actual exhaust valve timing may be estimated based on at least one of the oil temperature, the cooling water temperature, and the engine speed. Generally, in a system equipped with a variable valve timing mechanism, the oil pump is driven by the power of the internal combustion engine and hydraulic oil is supplied to the variable valve timing mechanism to drive the variable valve timing mechanism. The oil pressure changes, and the responsiveness of the variable valve timing mechanism changes. Further, the viscosity (fluidity) of the hydraulic oil changes according to the oil temperature of the hydraulic oil, and the responsiveness of the variable valve timing mechanism changes. Accordingly, since the oil temperature, the cooling water temperature (oil temperature substitute information), and the engine speed are all parameters for evaluating the responsiveness of the variable valve timing mechanism, at least the oil temperature, the cooling water temperature, and the engine speed are selected. If one is used, the response delay time of the actual exhaust valve timing with respect to the target exhaust valve timing can be estimated, and the actual exhaust valve timing can be estimated based on the response delay time and the target exhaust valve timing. In this case, the exhaust valve timing is detected because the actual exhaust valve timing can be estimated by using the output (cooling water temperature, engine speed, etc.) of existing sensors that are generally mounted for injection / ignition control of the internal combustion engine. Therefore, it is not necessary to add new sensors to meet the demand for cost reduction.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the direct injection engine 11 that is an in-cylinder internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. Is provided. A throttle valve 16 driven by a motor 15 such as a DC motor is provided on the downstream side of the air flow meter 14, and an opening degree (throttle opening degree) of the throttle valve 16 is detected by a throttle opening degree sensor 17.
[0021]
A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and the air flow (swirl flow or tumble flow) in the cylinder of the engine 11 is controlled by the intake manifold 20 of each cylinder. An airflow control valve 31 is provided.
[0022]
A fuel injection valve 21 that directly injects fuel into the cylinder is attached to an upper portion of each cylinder of the engine 11. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22. The intake valve 37 of the engine 11 is provided with a variable intake valve timing mechanism 39 that varies the intake valve timing (open / close timing of the intake valve 37), and the exhaust valve 38 has an exhaust valve timing (open / close of the exhaust valve 38). A variable exhaust valve timing mechanism 40 that varies the timing is provided.
[0023]
A knock sensor 32 for detecting knocking and a cooling water temperature sensor 23 for detecting cooling water temperature are attached to the cylinder block of the engine 11. A crank angle sensor 24 that outputs a crank angle signal at every predetermined crank angle is attached to the outer peripheral side of the crankshaft (not shown). Based on the crank angle signal from the crank angle sensor 24, the crank angle and the engine speed are detected. On the other hand, cam angle sensors 41 and 42 for outputting a cam angle signal for each predetermined cam angle are attached to the outer circumferences of the intake cam shaft and the exhaust cam shaft (both not shown).
[0024]
On the other hand, the exhaust pipe 25 of the engine 11 is provided with an upstream catalyst 26 and a downstream catalyst 27 for purifying the exhaust gas, and the air-fuel ratio or rich / lean of the exhaust gas is detected on the upstream side of the upstream catalyst 26. An exhaust gas sensor 28 (air-fuel ratio sensor, oxygen sensor, etc.) is provided. In the present embodiment, a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas near the stoichiometric air-fuel ratio is provided as the upstream side catalyst 26, and a NOx occlusion reduction type catalyst is provided as the downstream side catalyst 27. . This NOx occlusion reduction type catalyst occludes NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is lean, and reduces and purifies the occluded NOx when the air-fuel ratio becomes near the stoichiometric air-fuel ratio or becomes rich. Has characteristics.
[0025]
Further, a part of the exhaust gas is recirculated to the intake side between the downstream side of the upstream catalyst 26 in the exhaust pipe 25 and the surge tank 18 on the downstream side of the throttle valve 16 in the intake pipe 12. An EGR pipe 33 is connected, and an EGR valve 34 for controlling the exhaust gas recirculation amount (EGR amount) is provided in the middle of the EGR pipe 33. Further, the accelerator sensor 36 detects the amount of depression of the accelerator pedal 35 (accelerator opening).
[0026]
Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various control routines stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount and fuel of the fuel injection valve 21 according to the engine operating state. The injection timing, the ignition timing of the spark plug 22 and the like are controlled.
[0027]
The ECU 30 switches between the stratified combustion mode and the homogeneous combustion mode according to the engine operating state (required torque, engine speed, etc.) by executing routines shown in FIGS. In the stratified charge combustion mode, a small amount of fuel is directly injected into the cylinder in the compression stroke, and a stratified mixture is formed in the vicinity of the spark plug 22 for stratified charge combustion, thereby improving fuel efficiency. On the other hand, in the homogeneous combustion mode, the engine output is increased by increasing the fuel injection amount and directly injecting it into the cylinder during the intake stroke to form a homogeneous mixture and performing homogeneous combustion.
[0028]
In the stratified combustion mode, targets for air system control parameters (intake valve timing, exhaust valve timing, etc.), fuel system control parameters (fuel injection amount, fuel injection timing, etc.), and ignition system control parameters (ignition timing) As a value, a target value for the stratified combustion mode corresponding to the engine operating state is calculated using a map for the stratified combustion mode or the like. On the other hand, in the homogeneous combustion mode, the target values for the air system control parameter, the fuel system control parameter, and the ignition system control parameter are respectively used for the homogeneous combustion mode according to the engine operating state using a map for the homogeneous combustion mode. The target value of is calculated.
[0029]
Further, the ECU 30 executes a variable valve timing control routine (not shown) based on the crank angle signal output from the crank angle sensor 24 and the cam angle signal output from the cam angle sensor 42 on the exhaust camshaft side. The actual exhaust valve timing is calculated, and the variable exhaust valve timing mechanism 40 is feedback controlled so that the actual exhaust valve timing matches the target exhaust valve timing. In this case, the function of calculating the actual exhaust valve timing (actual advance amount VTac) based on the output signals of the crank angle sensor 24 and the cam angle sensor 42 plays a role as the exhaust valve timing detection means in the claims. .
[0030]
For example, as shown in FIG. 10 (a), both the exhaust valve timing and the fuel injection start timing are delayed from the state where both the exhaust valve timing and the fuel injection start timing are delayed, as shown in FIG. 10 (c). When both are changed to the advanced state, the relationship between the exhaust valve timing and the fuel injection start timing in the state before the change shown in FIG. 10A and the state after the change shown in FIG. It is desirable to set so that the closing timing of the exhaust valve is reached before the injected fuel reaches the exhaust port. In the conventional system, the exhaust valve timing and the fuel injection start timing are advanced from the position shown in FIG. 10A to the position shown in FIG. 10C. However, since the exhaust valve timing changes with a delay in response to the change in the target exhaust valve timing as shown in FIG. 11, the advance operation of the exhaust valve timing is completed. Until this time, as shown in FIG. 10B, the advance operation of the exhaust valve timing is delayed with respect to the advance operation of the fuel injection start timing, and the fuel injection start time and the exhaust valve opening period overlap. During that period, a part of the injected fuel passes through the gap of the exhaust valve before closing, and is discharged to the exhaust pipe. But problems occur that worse.
[0031]
Therefore, the ECU 30 executes the injection timing correction routine shown in FIG. 8 so that the fuel injection start timing calculated based on the engine operating state is advanced from the exhaust valve closing timing detected based on the actual exhaust valve timing. When it is angular (when the fuel injection start timing overlaps with the opening period of the exhaust valve 38), a part of the injected fuel reaches the exhaust port before the exhaust valve 38 is closed, and the exhaust pipe 25 It is determined that there is a possibility that “injected fuel may be slipped”, and the fuel injection start timing is corrected to be retarded according to the difference between the fuel injection start timing and the exhaust valve closing timing. The exhaust valve 38 is controlled to close before the fuel reaches the exhaust port to prevent the injected fuel from slipping through.
[0032]
Hereinafter, the processing content of each routine shown in FIGS. 2 to 8 executed by the ECU 30 in the present embodiment will be described.
[0033]
[Engine control main routine]
The engine control main routine of FIG. 2 is executed at a predetermined cycle after an ignition switch (not shown) is turned on. When the main routine is started, first, in step 100, the required torque is calculated based on the accelerator opening, the engine speed, and the like. After this, the routine proceeds to step 200, the combustion mode determination routine of FIG. 3 is executed to determine the combustion mode, and then the routine proceeds to step 300, where the combustion mode switching control routine of FIG. For example, the combustion mode switching control is executed, and in the next steps 400 to 600, the air system control routine of FIG. 5, the fuel system control routine of FIG. 6, and the ignition system control routine of FIG. The combustion mode is switched by switching the control parameters of the system and the ignition system to the target value of the switching destination combustion mode at the timing described later.
[0034]
[Combustion mode decision routine]
When the combustion mode determination routine of FIG. 3 is started in step 200 of the engine control main routine of FIG. 2, first, in step 201, the required combustion mode determination map is searched and the current engine operating state (for example, engine speed Depending on the required torque), either the stratified combustion mode or the homogeneous combustion mode is selected as the required combustion mode. In this required combustion mode determination map, the stratified combustion mode is selected in the low rotation and low torque regions with priority on fuel economy, while the homogeneous combustion mode is selected in the high rotation and high torque regions with priority on engine output. Is set to be.
[0035]
Thereafter, the process proceeds to step 202, where it is determined whether the required combustion mode selected according to the current engine operating state is the homogeneous combustion mode. If the required combustion mode is the homogeneous combustion mode, the process proceeds to step 203, It is determined whether or not the current actual combustion mode is the homogeneous combustion mode. If the current actual combustion mode is not the homogeneous combustion mode, it is necessary to switch the combustion mode. Therefore, the routine proceeds to step 204, the combustion mode switching flag is turned on, and the routine proceeds to step 205, where the air system control mode is made homogeneous. Set to combustion mode. On the other hand, if the current actual combustion mode is the homogeneous combustion mode, it is not necessary to switch the combustion mode. Therefore, the process skips step 204 and proceeds to step 205 to maintain the air system control mode in the homogeneous combustion mode.
[0036]
When it is determined in step 202 that the required combustion mode is not the homogeneous combustion mode (stratified combustion mode), the routine proceeds to step 207, where it is determined whether or not the current actual combustion mode is the stratified combustion mode. . If the current actual combustion mode is not the stratified combustion mode, it is necessary to switch the combustion mode. Therefore, the routine proceeds to step 208, the combustion mode switching flag is turned on, and the routine proceeds to step 209, where the air system control mode is made homogeneous. Set to combustion mode. On the other hand, if the current actual combustion mode is the stratified combustion mode, there is no need to switch the combustion mode, so step 208 is skipped and the routine proceeds to step 205 to maintain the air system control mode in the stratified combustion mode.
[0037]
[Combustion mode switching control routine]
When the combustion mode switching control routine of FIG. 4 is started in step 300 of the engine control main routine of FIG. 2, first, in step 301, the combustion mode switching is being performed depending on whether or not the combustion mode switching flag is ON. If it is not during combustion mode switching, this routine is terminated without performing the subsequent processing.
[0038]
On the other hand, if the combustion mode is being switched, the routine proceeds to step 302, where it is determined whether or not the required combustion mode is the stratified combustion mode, and the required combustion mode is not the stratified combustion mode (that is, the required combustion mode is the homogeneous combustion mode). If so, the process proceeds to step 303, where it is determined whether or not the actual air-fuel ratio A / F is in the homogeneous combustion region by determining whether or not the actual air-fuel ratio A / F is richer than the homogeneous combustion region determination value CAF2. . As a result, when it is determined that the actual air-fuel ratio A / F is leaner than the homogeneous combustion region determination value CAF2 (the actual air-fuel ratio A / F is not in the homogeneous combustion region), the subsequent processing is not performed. This routine is terminated.
[0039]
Thereafter, when it is determined that the actual air-fuel ratio A / F becomes richer than the homogeneous combustion region determination value CAF2 and the actual air-fuel ratio A / F has entered a region where homogeneous combustion can be performed, the routine proceeds to step 304, where fuel system control is performed. After the mode is set to the homogeneous combustion mode and the fuel injection mode is switched to the intake stroke injection, the combustion mode switching flag is turned OFF and this routine is terminated.
[0040]
Further, when the combustion mode is being switched and it is determined that the required combustion mode is the stratified combustion mode (when both the determinations in steps 301 and 302 are “Yes”), the routine proceeds to step 306 and the actual air-fuel ratio A Whether or not the actual air-fuel ratio A / F is in the stratified combustion region is determined by whether / F is leaner than the stratified combustion region determination value CAF1. As a result, when it is determined that the actual air-fuel ratio A / F is richer than the stratified combustion region determination value CAF1 (the actual air-fuel ratio A / F does not enter the stratified combustion region), the subsequent processing is performed. This routine is terminated.
[0041]
Thereafter, when it is determined that the actual air-fuel ratio A / F is leaner than the stratified charge combustion region determination value CAF1 and the actual air-fuel ratio A / F has entered a region where stratified combustion is possible, the routine proceeds to step 308, where fuel system control is performed. After the mode is set to the stratified combustion mode and the fuel injection mode is switched to the compression stroke injection, the combustion mode switching flag is turned OFF and this routine is terminated.
[0042]
[Air control routine]
When the air system control routine of FIG. 5 is started in step 400 of the engine control main routine of FIG. 2, first, in step 401, it is determined whether or not the air system control mode is the homogeneous combustion mode. If so, the process proceeds to step 402, where the target values of the air system control parameters (intake valve timing, exhaust valve timing, throttle opening, EGR valve 34 opening, airflow control valve 31 opening) are each homogeneous. A target value for the homogeneous combustion mode corresponding to the engine operating state is calculated using a map for the combustion mode.
[0043]
On the other hand, if it is determined in step 401 that the air system control mode is not the homogeneous combustion mode (the stratified combustion mode), the process proceeds to step 403 where the stratified combustion mode is set as the target value of each control parameter of the air system. A target value for the stratified combustion mode corresponding to the engine operating state is calculated using a map for the purpose.
[0044]
[Fuel system control routine]
When the fuel system control routine of FIG. 6 is started in step 500 of the engine control main routine of FIG. 2, first, in step 501, it is determined whether or not the fuel system control mode is the homogeneous combustion mode, and the homogeneous combustion mode is determined. If so, the process proceeds to step 502, and the target values of the fuel system control parameters (fuel injection amount, fuel injection start timing) are respectively used for the homogeneous combustion mode according to the engine operating state using the map for the homogeneous combustion mode. Target values (fuel injection time, base fuel injection start timing INJBS) are calculated.
[0045]
If it is determined in step 501 that the fuel system control mode is not the homogeneous combustion mode (stratified combustion mode), the process proceeds to step 503, and the target values (fuel injection amount, fuel injection) of the fuel system control parameters are advanced. As the start time), a target value (fuel injection time, base fuel injection start time INJBS) for the stratified combustion mode corresponding to the engine operating state is calculated using a map for the stratified combustion mode.
[0046]
[Ignition system control routine]
When the ignition system control routine of FIG. 7 is started in step 600 of the engine control main routine of FIG. 2, first, in step 601, it is determined whether or not the ignition system control mode (= fuel system control mode) is the homogeneous combustion mode. If it is the homogeneous combustion mode, the process proceeds to step 602, and the target value of the ignition system control parameter (ignition timing) is used for the homogeneous combustion mode according to the engine operating state using a map for the homogeneous combustion mode or the like. The target value of is calculated.
[0047]
If it is determined in step 601 that the ignition system control mode is not the homogeneous combustion mode (stratified combustion mode), the process proceeds to step 603, where the target value of the ignition system control parameter is set for the stratified combustion mode. A target value for the stratified combustion mode corresponding to the engine operating state is calculated using a map or the like.
[0048]
[Injection timing correction routine]
The injection timing correction routine shown in FIG. 8 is executed in a predetermined cycle after an ignition switch (not shown) is turned on, and serves as an injection timing correction means in the claims. When this routine is started, first, in step 701, the actual exhaust valve calculated based on the target exhaust valve timing VTtg calculated in the air system control routine of FIG. 5 and the output signals of the crank angle sensor 24 and the cam angle sensor 42 are obtained. After reading the timing VTac, the routine proceeds to step 702, where it is determined whether or not the difference between the actual exhaust valve timing VTac and the target exhaust valve timing VTtg is larger than a predetermined value D1.
[0049]
As a result, when it is determined that the difference between the actual exhaust valve timing VTac and the target exhaust valve timing VTtg is equal to or less than the predetermined value D1, the actual exhaust valve timing VTac almost converges to the target exhaust valve timing VTtg. Then, the process proceeds to step 707, where the retardation correction amount VTCMP is set to “0”. In this case, the delay correction of the fuel injection start timing is not performed.
[0050]
On the other hand, when it is determined in step 702 that the difference between the actual exhaust valve timing VTac and the target exhaust valve timing VTtg is larger than the predetermined value D1, the actual exhaust valve timing VTac is compared with the target exhaust valve timing VTtg. When it is determined that there is a delay in the advance angle operation, the routine proceeds to step 703 where the base fuel injection start timing INJBS calculated based on the engine operating state by the fuel system control routine of FIG. 6 is read and the exhaust valve 38 is operated. The angle VT1 and the exhaust valve timing set position VT0 are read. The exhaust valve timing setting position VT0 is a position for setting an exhaust valve timing command value, and corresponds to the most advanced position (actual exhaust valve timing VTac = 0).
[0051]
Therefore, as shown in FIG. 9, the position obtained by subtracting the actual exhaust valve timing VTac from the exhaust valve timing set position VT0 becomes the exhaust valve opening timing (VT0-VTac), and this exhaust valve opening timing (VT0-VTac). The position obtained by subtracting the operating angle VT1 of the exhaust valve 38 from this is the exhaust valve closing timing (VT0-VTac-VT1).
[0052]
Thereafter, the process proceeds to step 704, where a difference DANG between the base fuel injection start timing INJBS and the exhaust valve closing timing (VT0−VTac−VT1) is obtained.
DANG = INJBS- (VT0-VTac-VT1)
[0053]
Then, in the next step 705, it is determined whether or not the difference DANG between the base fuel injection start timing INJBS and the exhaust valve closing timing (VT0−VTac−VT1) is larger than a predetermined value D2. Here, the predetermined value D2 is set to a value corresponding to a time until the fuel injected from the fuel injection valve 21 reaches the exhaust port (hereinafter referred to as “injected fuel arrival time”). This predetermined value D2 may be a fixed value set in advance, or may be a variable value set by a map or the like according to the engine rotation speed Ne. The predetermined value D2 may be set in consideration of the response delay time of the fuel injection valve 21 and other error factors in addition to the injection fuel arrival time. The predetermined value D2 may be set to 0.
[0054]
If it is determined in step 705 that the difference DANG between the base fuel injection start timing INJBS and the exhaust valve closing timing (VT0−VTac−VT1) is equal to or smaller than a predetermined value D2 (injected fuel arrival time), that is, the base The fuel injection start timing INJBS is later (retarded) than the exhaust valve closing timing (VT0-VTac-VT1), or the base fuel injection start timing INJBS is higher than the exhaust valve closing timing (VT0-VTac-VT1). If the time difference is less than or equal to the predetermined value D2 (injection fuel arrival time) at the earliest (advance), it is determined that the exhaust valve 38 is closed before the injected fuel reaches the exhaust port. In step 707, the retardation correction amount VTCMP is set to “0”. In this case, the retard correction of the fuel injection start timing is not performed.
[0055]
On the other hand, if it is determined in step 705 that the difference DANG between the base fuel injection start timing INJBS and the exhaust valve closing timing (VT0−VTac−VT1) is larger than the predetermined value D2, that is, the base fuel injection start timing. When INJBS is advanced by a predetermined value D2 (injected fuel arrival time) or more than the exhaust valve closing timing (VT0-VTac-VT1), the injected fuel reaches the exhaust port before the exhaust valve 38 is closed. In step 706, it is determined that there is a possibility that “injection of injected fuel” discharged to the exhaust pipe 25 may occur, and the base fuel injection start timing INJBS and the exhaust gas are exhausted using the map of the retard correction amount VTCMP. A retardation correction amount VTCMP is calculated in accordance with the difference DANG from the valve closing timing (VT0−VTac−VT1) and the engine rotational speed Ne.
[0056]
Thereafter, the process proceeds to step 708, where the base fuel injection start timing INJBS is delayed by the delay correction amount VTCMP to obtain the final fuel injection start timing INJ.
INJ = INJBS-VTCMP
[0057]
According to the present embodiment described above, as shown in FIG. 9, the base fuel injection start timing INJBS calculated based on the engine operating state is a predetermined value D2 (exceeding the exhaust valve closing timing (VT0-VTac-VT1)). If the advance angle is greater than the injection fuel arrival time), there is a possibility that “injected fuel slipping” occurs in which the injected fuel reaches the exhaust port before the exhaust valve 38 is closed and is discharged to the exhaust pipe 25. Therefore, the retard correction amount VTCMP is calculated according to the difference DANG between the base fuel injection start timing INJBS and the exhaust valve closing timing (VT0−VTac−VT1), and this retard correction amount VTCMP is used. The final fuel injection start timing INJ is set by correcting the delay of the base fuel injection start timing INJBS.
[0058]
Thus, for example, as shown in FIG. 10 (a), the exhaust valve timing and the fuel injection start timing are both retarded, and as shown in FIG. 10 (c), the exhaust valve timing and the fuel injection start are started. Even if there is a situation where a response delay occurs in the advance operation of the actual exhaust valve timing VTac in the process of changing both timings to the advanced state, the response of the actual exhaust valve timing VTac as shown in FIG. The advance operation at the fuel injection start timing can be delayed in accordance with the delay, and the advance operation at the fuel injection start timing can have a delay equivalent to the response delay of the actual exhaust valve timing. As a result, even during the transitional period in which the exhaust valve timing and the fuel injection start timing are advanced, the relationship between the exhaust valve timing and the fuel injection start timing can be determined by using the valve closing timing of the exhaust valve 38 before the injected fuel reaches the exhaust port. Control can be performed to maintain the greeted state, and it is possible to reliably prevent the injected fuel from slipping through and to improve exhaust emission.
[0059]
Even when only one of the exhaust valve timing and the fuel injection start timing is advanced, the relationship between the exhaust valve timing and the fuel injection start timing can be determined by closing the exhaust valve 38 before the injected fuel reaches the exhaust port. The fuel injection start timing can be appropriately retarded so as to maintain the valve timing, and injection fuel can be reliably prevented from passing through.
[0060]
In this embodiment, the fuel injection start timing is retarded when the base fuel injection start timing INJBS is advanced by a predetermined value D2 (injected fuel arrival time) or more than the exhaust valve closing timing (VT0-VTac-VT1). Although the correction is made, when the base fuel injection start timing INJBS is advanced from the exhaust valve closing timing (VT0-VTac-VT1), the fuel injection start timing may be retarded. Even in this case, it is possible to reliably prevent the injected fuel from slipping through.
[0061]
By the way, when setting the retard correction amount VTCMP for the fuel injection start timing, set the minimum retard correction amount necessary to reach the closing timing of the exhaust valve 38 before the injected fuel reaches the exhaust port. Thus, it is possible to sufficiently obtain the effect of preventing the injected fuel from slipping through, and even if the retard correction amount VTCMP at the fuel injection start timing is increased, the effect of preventing the injected fuel from slipping through is hardly changed. It only has an adverse effect on the combustibility (the fuel injection start timing needs to be set so as to ensure combustibility).
[0062]
In this respect, in the present embodiment, the retard correction amount VTCMP is obtained in accordance with the difference between the base fuel injection start timing INJBS and the exhaust valve closing timing, so that the exhaust valve before the injected fuel reaches the exhaust port. The minimum retardation correction amount VTCMP necessary for reaching the valve closing timing of 38 can be set, and the injected fuel can be prevented from slipping through while minimizing the influence on the combustibility. It is possible to achieve both ensuring and prevention of injected fuel slip-through.
[0063]
In the above embodiment, the retard correction amount VTCMP is set according to the difference between the base fuel injection start timing INJBS and the exhaust valve closing timing. However, the actual exhaust valve timing VTac and the target exhaust valve timing VTtg The retard correction amount VTCMP may be set according to the difference between the two. The greater the difference between the actual exhaust valve timing VTac and the target exhaust valve timing VTtg, the longer the response delay time until the actual exhaust valve timing VTac reaches the target exhaust valve timing VTtg (a period during which the injected fuel may slip through). ) Becomes longer, so if the delay correction amount of the fuel injection timing is set according to the difference between the actual exhaust valve timing VTac and the target exhaust valve timing VTtg, the response delay time of the actual exhaust valve timing VTac can be obtained. Accordingly, an appropriate retardation correction amount VTCMP can be set, and it is possible to prevent the injected fuel from slipping through while reducing the influence on the combustibility.
[0064]
In the above embodiment, the actual exhaust valve timing VTac is calculated based on the output signals of the crank angle sensor 24 and the cam angle sensor 42. However, based on at least one of the oil temperature, the coolant temperature, and the engine speed. The actual exhaust valve timing VTac may be estimated. In general, in a system equipped with the variable exhaust valve timing mechanism 40, the oil pump is driven by the power of the engine 11 to supply hydraulic oil to the variable exhaust valve timing mechanism 40 to drive the variable exhaust valve timing mechanism 40. The hydraulic pressure of the hydraulic oil changes according to the rotation speed, and the responsiveness of the variable exhaust valve timing mechanism 40 changes. Further, the viscosity (fluidity) of the hydraulic oil changes according to the temperature of the hydraulic oil, and the responsiveness of the variable exhaust valve timing mechanism 40 changes. Therefore, the oil temperature, the coolant temperature (oil temperature substitute information), and the engine speed are parameters for evaluating the response of the variable exhaust valve timing mechanism 40, that is, the response delay of the actual exhaust valve timing VTac with respect to the target exhaust valve timing VTtg. Therefore, if at least one of the oil temperature, the cooling water temperature, and the engine speed is used, the response delay time of the actual exhaust valve timing VTac with respect to the target exhaust valve timing VTtg is estimated, and this response delay time and the target exhaust time are estimated. The actual exhaust valve timing VTac can be estimated based on the valve timing VTtg.
[0065]
The drive source that varies the exhaust valve timing is not limited to hydraulic pressure, and the present invention can also be applied to an internal combustion engine that varies the exhaust valve timing by an electromagnetic actuator or the like.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of processing of an engine control main routine.
FIG. 3 is a flowchart showing the flow of processing of a combustion mode determination routine.
FIG. 4 is a flowchart showing a process flow of a combustion mode switching control routine.
FIG. 5 is a flowchart showing a flow of processing of an air system control routine.
FIG. 6 is a flowchart showing a flow of processing of a fuel system control routine.
FIG. 7 is a flowchart showing a flow of processing of an ignition system control routine.
FIG. 8 is a flowchart showing a flow of processing of an injection timing correction routine.
FIG. 9 is a view for explaining a method for correcting the delay angle of the fuel injection start timing.
10A is a diagram showing a state where the exhaust valve timing and the fuel injection start timing are retarded, FIG. 10B is a diagram illustrating a response delay of the advance operation of the exhaust valve timing, and FIG. The figure which shows the state where the exhaust valve timing and the fuel injection start timing are advanced
FIG. 11 is a time chart showing the behavior of fuel injection start timing and exhaust valve timing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 24 ... Crank angle sensor, 25 ... Exhaust pipe, 30 ... ECU (Exhaust valve timing detection means, Injection timing correction means), 37... Intake valve, 38... Exhaust valve, 39... Variable intake valve timing mechanism, 40.

Claims (5)

A fuel injection valve that directly injects fuel into the cylinder; and a variable exhaust valve timing mechanism that changes a valve timing of the exhaust valve (hereinafter referred to as “exhaust valve timing”). In a control device for an internal combustion engine that controls the fuel injection timing of the valve and the exhaust valve timing,
Exhaust valve timing detection means for detecting or estimating the exhaust valve timing;
An injection that retards the fuel injection timing based on the closing timing of the actual exhaust valve timing detected or estimated by the exhaust valve timing detection means when at least one of the exhaust valve timing and the fuel injection timing is advanced. A control device for an internal combustion engine, comprising: timing correction means.   The injection timing correction means corrects the delay of the fuel injection timing when the fuel injection timing is advanced from an actual exhaust valve closing timing detected based on the actual exhaust valve timing. The control device for an internal combustion engine according to claim 1.   The injection timing correction means sets a delay correction amount of the fuel injection timing according to a difference between the fuel injection timing and an actual exhaust valve closing timing detected based on the actual exhaust valve timing. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   The said injection timing correction | amendment means sets the amount of retardation corrections of the said fuel injection timing according to the difference of the said actual exhaust valve timing and a target exhaust valve timing. Control device for internal combustion engine.   5. The internal combustion engine according to claim 1, wherein the exhaust valve timing detection unit estimates an actual exhaust valve timing based on at least one of an oil temperature, a cooling water temperature, and an engine rotation speed. Engine control device.

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