JP3956951B2 - Fuel injection device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a fuel injection device having an in-cylinder fuel injection valve that injects fuel directly into an engine cylinder.

2. Description of the Related Art A fuel injection device that includes a cylinder fuel injection valve that directly injects fuel into a cylinder and performs secondary fuel injection in an expansion stroke or an exhaust stroke of the cylinder in addition to main fuel injection that contributes to normal in-cylinder combustion is known It has been.
An example of this type of apparatus is disclosed in Patent Document 1.

The apparatus of Literature 1 absorbs NO _x in exhaust when the air-fuel ratio of the exhaust flowing into the exhaust passage of the diesel engine is lean, and releases the absorbed NO _x when the oxygen concentration in the flowing exhaust decreases. _the NO _X storage reduction catalyst were placed, usually performs a main fuel injected into the cylinder at the compression top dead center near the engine cylinder, the time to emit NO _X from _the NO _X storage reduction catalyst, in addition to the main fuel injection cylinder Secondary fuel injection is performed during the expansion or exhaust stroke.

The fuel injected into the cylinder during the expansion or exhaust stroke is exposed to the high-temperature burned gas without contributing to the combustion in the cylinder, and therefore the hydrocarbon with a high molecular weight in the fuel has a molecular weight. Decomposes into small hydrocarbons. In addition, since the fuel injected by the secondary fuel injection does not contribute to combustion and is exhausted with the exhaust as it is, even in a diesel engine, a comparison that only makes the exhaust rich air-fuel ratio without increasing the explosion pressure in the cylinder A large amount of fuel can be injected. Therefore, exhaust gas of a rich air-fuel ratio rich in hydrocarbons having a high active low molecular weight becomes to flow to the NO _X occluding and reducing catalyst in the exhaust passage by the secondary fuel injection, NO was absorbed from _the NO _X storage reduction catalyst _X Is released and reduced and purified by hydrocarbons in the exhaust.

JP-A-6-212961

  However, in the engine that performs the secondary fuel injection as in Patent Document 1, the fuel injected by the secondary fuel injection may not be completely discharged during the exhaust stroke but may remain in the cylinder. If a part of the fuel of the secondary fuel injection remains in the cylinder, the remaining fuel burns in addition to the fuel supplied by the main fuel injection in the cylinder the next time the main fuel injection is performed. There is a problem in that the generated torque becomes excessive and the engine output torque fluctuates.

  In view of the above problems, an object of the present invention is to provide a fuel injection device for an internal combustion engine that can prevent engine output torque fluctuations due to residual fuel during secondary fuel injection.

  According to the first aspect of the present invention, the in-cylinder fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine and the in-cylinder fuel injection valve are controlled to inject fuel that contributes to combustion in the cylinder. Fuel injection control means for performing secondary fuel injection that performs main fuel injection and, if necessary, injects fuel that does not contribute to combustion in the cylinder during the expansion stroke or exhaust stroke after the main fuel injection, The fuel injection control means calculates the amount of fuel remaining in the cylinder among the fuel injected by the immediately preceding secondary fuel injection and corrects the injection amount of the main fuel injection according to the residual fuel amount. A fuel injection device for an internal combustion engine is provided.

  That is, in the first aspect of the invention, the fuel injection control means calculates the amount of fuel remaining in the cylinder by the immediately preceding secondary fuel injection, and corrects the main fuel injection amount according to the residual fuel amount. This correction is performed, for example, by reducing the main fuel injection amount by an amount corresponding to the residual fuel amount. As a result, the amount of fuel that contributes to combustion during main fuel injection is maintained at the target amount. For this reason, even when fuel remains in the cylinder due to the secondary fuel injection, the output torque fluctuation of the engine does not occur.

  According to the second aspect of the present invention, the in-cylinder fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine and the in-cylinder fuel injection valve are controlled to inject fuel that contributes to combustion in the cylinder. Fuel injection control means for performing secondary fuel injection that performs main fuel injection and, if necessary, injects fuel that does not contribute to combustion in the cylinder during the expansion stroke or exhaust stroke after the main fuel injection, The fuel injection control means converts the main fuel injection into a first main fuel injection for generating a homogeneous mixture in the cylinder and a second main fuel injection for generating a layer of combustible mixture as necessary. When the secondary fuel injection is executed, the amount of fuel remaining in the cylinder is calculated from the fuel injected by the immediately preceding secondary fuel injection, and the second fuel injection is performed according to the residual fuel amount. Fuel for an internal combustion engine that corrects the injection amount of one main fuel injection Morphism apparatus is provided.

  That is, in the second aspect of the invention, when the main fuel injection is performed twice, the fuel injection control means corrects the amount of the first main fuel injection according to the in-cylinder residual fuel amount by the secondary fuel injection. This correction is performed, for example, by reducing the first main fuel injection amount by an amount corresponding to the residual fuel amount. The first main fuel injection is for generating a homogeneous air-fuel mixture in the cylinder, while the second main fuel injection is for stratifying the air-fuel mixture. On the other hand, the fuel remaining in the cylinder generates a homogeneous air-fuel mixture in the cylinder. For this reason, when the first main fuel injection amount is set as usual, the air-fuel ratio of the generated homogeneous mixture becomes richer than the target value. In the present invention, the air-fuel ratio of the homogeneous mixture generated in the cylinder is maintained at the target value by correcting the first main fuel injection amount in accordance with the residual fuel amount.

  In the invention described in each claim, the amount of fuel remaining in the cylinder at the time of performing the secondary fuel injection is calculated, and the main fuel injection amount is corrected according to the residual fuel amount. Even when the in-cylinder residual fuel is generated, it is possible to prevent the fluctuation of the engine output.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an embodiment in which the fuel injection device of the present invention is applied to an automobile internal combustion engine.
In FIG. 1, reference numeral 1 denotes an automobile internal combustion engine. In the present embodiment, the engine 1 is a four-cylinder gasoline engine having four cylinders # 1 to # 4, and the fuel injection valves 111 to 114 for injecting fuel directly into the cylinders are provided for the # 1 to # 4 cylinders. Is provided. As will be described later, the internal combustion engine 1 of the present embodiment is a lean burn engine that can be operated at an air fuel ratio higher (lean) than the stoichiometric air fuel ratio.

  Further, in the present embodiment, the cylinders # 1 to # 4 are grouped into two cylinder groups including two cylinders whose ignition timings are not continuous with each other. (For example, in the embodiment of FIG. 1, the cylinder firing order is 1-3-4-2, and the cylinders # 1 and # 4 and the cylinders # 2 and # 3 each constitute a cylinder group. In addition, the exhaust port of each cylinder is connected to an exhaust manifold for each cylinder group, and is connected to an exhaust passage for each cylinder group. In FIG. 1, reference numeral 21a denotes an exhaust manifold for connecting the exhaust ports of the cylinder group consisting of # 1 and # 4 cylinders to the individual exhaust passage 2a, and 21b denotes the exhaust port of the cylinder group consisting of # 2 and # 4 cylinders to the individual exhaust passage 2b. Is an exhaust manifold connected to In the present embodiment, start catalysts (hereinafter referred to as “SC”) 5a and 5b made of a three-way catalyst are arranged on the individual exhaust passages 2a and 2b, respectively. Further, the individual exhaust passages 2a and 2b merge with the common exhaust passage 2 on the downstream side of the SC.

On the common exhaust passage 2, a NO _x storage reduction catalyst 7 to be described later is disposed. In FIG. 1, 29 a and 29 b indicate air-fuel ratio sensors arranged upstream of the start catalysts 5 a and 5 b in the individual exhaust passages 2 a and 2 b, and 31 indicates an NO _X storage reduction catalyst 7 in the exhaust passage 2. An air-fuel ratio sensor disposed at the outlet. The air-fuel ratio sensors 29a, 29b, and 31 are so-called linear air-fuel ratio sensors that output a voltage signal corresponding to the exhaust air-fuel ratio in a wide air-fuel ratio range.

  In FIG. 1, the intake ports of cylinders # 1 to # 4 of one engine are connected to a surge tank 10a via an intake manifold 10b, and the surge tanks are connected to a common intake passage 10. Further, in the present embodiment, a throttle valve 15 is provided on the intake passage 10. The throttle valve 15 of the present embodiment is a so-called electronically controlled throttle valve, which is driven by an actuator 15a of an appropriate type such as a stepper motor and has an opening corresponding to a control signal from an ECU 30 described later. 1 is a throttle valve opening sensor for detecting the opening degree of the throttle valve 15.

  In this embodiment, the in-cylinder fuel injection valves 111 to 114 are individually connected to a common rail (pressure accumulation chamber) 110 and inject high-pressure fuel in the common rail 110 into the cylinder. 1 is a fuel pump composed of a high-pressure pump such as a plunger pump. The fuel pump 130 pumps high-pressure fuel to the common rail 110 every time fuel injection of each fuel injection valve (111 to 114) is performed.

  1 is a variable valve timing apparatus that changes the valve timing of the engine 1. In the present embodiment, the variable valve timing device 200 can be of any known type as long as it can change the valve timing of the engine 1 in accordance with a command signal from the ECU 30, which will be described later. Alternatively, any of those that change only the opening / closing timing of the exhaust valve and those that change the valve lift together with the opening / closing timing can be used. The valve timing may be changed continuously or stepwise.

1 is an ECU (engine control unit) that controls the engine 1. The ECU 30 includes a microcomputer having a known configuration in which a RAM, a ROM, and a CPU are connected to each other via a bidirectional bus, and performs basic control such as main fuel injection control and ignition timing control of the engine 1. Further, ECU 30 is switched to make a combustion in the cylinder at the time of reproducing operation of the NO _X occluding and reducing catalyst to be described later to the rich air-fuel ratio in the present embodiment, _the NO _X storage reduction catalyst performs secondary fuel injection in the expansion or exhaust stroke of each cylinder Secondary fuel injection control for switching the exhaust air-fuel ratio flowing into the engine to a rich air-fuel ratio in a short time is performed.

The ECU30 input ports, air-fuel ratio sensor 29a, a signal representative of the exhaust air-fuel ratio SCs 5a, in 5b the entrance from 29 b, and a signal representing the exhaust gas air-fuel ratio in _the NO _X storage reduction catalyst 7 exit from the air-fuel ratio sensor 31, a surge tank A signal corresponding to the intake pressure of the engine is input from the intake pressure sensor 37 provided in 10a, and a signal corresponding to the accelerator pedal depression amount (accelerator opening) of the driver is input from the accelerator opening sensor 33, respectively. A crank rotation angle pulse signal is input at every engine crankshaft rotation angle from a rotation speed sensor 35 arranged in the vicinity of the engine crankshaft (not shown). The ECU 30 calculates the crankshaft rotation angle from the pulse signal, and calculates the engine speed from the frequency of the pulse signal.

  Further, a signal corresponding to the fuel pressure in the common rail 110 is input to the input port of the ECU 30 from the fuel pressure sensor 120 disposed on the common rail 110, and a signal indicating the opening of the throttle valve 15 is input from the throttle valve opening sensor 15b. Yes.

  The output port of the ECU 30 is connected to the fuel injection valves 111 to 114 of each cylinder through a fuel injection circuit (not shown) in order to control the fuel injection amount and fuel injection timing to each cylinder. The opening of the throttle valve 15 is controlled by being connected to the actuator 15b of the valve 15 via a drive circuit (not shown).

  In addition to the above control, the ECU 30 feedback-controls the fuel pumping amount of the fuel pump 130 so that the fuel pressure in the common rail becomes a target value in accordance with the fuel pressure signal in the common rail 110 input from the fuel pressure sensor 120. The fuel is pumped from the fuel pump 130 to the common rail 110 every time fuel is injected from the fuel injection valves 111 to 114.

Further, the output port of the ECU 30 is connected to the variable valve timing device 200 via a drive circuit (not shown), and controls the valve timing of the engine 1 according to the engine load state (accelerator opening degree and engine speed). Yes.
In the present embodiment, the main fuel injection of the engine 1, that is, the fuel injection for combustion in the cylinder, is controlled in the following five modes according to the engine load.

1) Lean air-fuel ratio stratified charge combustion (one compression stroke injection)
2) Lean air-fuel ratio homogeneous mixture / stratified combustion (intake stroke / compression stroke twice injection)
3) Lean air / fuel ratio homogeneous mixture combustion (intake stroke one injection)
4) Theoretical air-fuel ratio homogeneous mixture combustion (intake stroke one injection)
5) Rich air-fuel ratio homogeneous mixture combustion (intake stroke one injection)

  That is, in the light load operation region of the engine 1, the lean air-fuel ratio stratified combustion of 1) is performed. In this state, in-cylinder fuel injection is performed only once in the latter half of the compression stroke of each cylinder, and the injected fuel forms a combustible mixture layer near the cylinder spark plug. Further, the fuel injection amount in this operation state is extremely small, and the air-fuel ratio as a whole in the cylinder is about 25 to 30.

  Further, when the load increases from the state 1) to the low load operation region, the 2) lean air-fuel ratio homogeneous mixture / stratified combustion is performed. As the engine load increases, the amount of fuel injected into the cylinder increases. However, in the stratified combustion of 1), the fuel injection is performed in the latter half of the compression stroke, so the injection time is limited and the amount of fuel that can be stratified is reduced. There are limits. Therefore, in this load region, a target amount of fuel is supplied to the cylinders by injecting in advance into the first half of the intake stroke an amount of fuel that is insufficient only by fuel injection in the latter half of the compression stroke.

  The fuel injected into the cylinder in the first half of the intake stroke generates a very lean homogeneous mixture by the time of ignition. In the latter half of the compression stroke, further fuel is injected into this extremely lean homogeneous mixture to generate a combustible mixture layer that can be ignited in the vicinity of the spark plug. At the time of ignition, the combustible air-fuel mixture layer starts to burn, and the flame propagates to the surrounding lean air-fuel mixture layer, so that stable combustion is performed. In this state, the amount of fuel supplied by the injection in the intake stroke and the compression stroke is increased from 1), but the overall air-fuel ratio becomes slightly low (for example, about 20 to 30 in the air-fuel ratio).

  When the engine load further increases, the engine 1 performs the lean air-fuel ratio homogeneous mixture combustion of 3) above. In this state, fuel injection is executed only once in the first half of the intake stroke, and the fuel injection amount is further increased from 2) above. In this state, the homogeneous air-fuel mixture generated in the cylinder has a lean air-fuel ratio that is relatively close to the stoichiometric air-fuel ratio (for example, about 15 to 25 as the air-fuel ratio).

  When the engine load further increases and the engine high load operation region is reached, the fuel is further increased from the state of 3), and the stoichiometric air-fuel ratio homogeneous mixture operation of 4) is performed. In this state, a homogeneous air-fuel mixture having a stoichiometric air-fuel ratio is generated in the cylinder, and the engine output increases. Further, when the engine load further increases and the engine is fully loaded, the fuel injection amount is further increased from the state 4), and the rich air-fuel ratio homogeneous mixture operation 5) is performed. In this state, the air-fuel ratio of the homogeneous mixture generated in the cylinder becomes rich (for example, about 12 to 14 as the air-fuel ratio).

  In the present embodiment, an optimal operation mode (from 1 to 5) above is set in advance based on experiments and the like according to the accelerator opening (the amount by which the driver depresses the accelerator pedal) and the engine speed, and the ECU 30 Is stored as a map using the accelerator opening and the engine speed. During the engine 1 operation, the ECU 30 determines which one of the above operation modes 1) to 5) should be selected based on the accelerator operation amount detected by the accelerator operation amount sensor 33 and the engine speed. The fuel injection amount, the fuel injection timing, the number of times, and the throttle valve opening are determined accordingly.

  That is, when the mode 1) to 3) (lean air-fuel ratio combustion) is selected, the ECU 30 determines the accelerator opening and the engine based on a map prepared in advance for each mode 1) to 3). The fuel injection amount is determined from the rotational speed. When the modes 4) and 5) (theoretical air-fuel ratio or rich air-fuel ratio homogeneous mixture combustion) are selected, the ECU 30 is based on a map prepared in advance for each of the modes 4) and 5). Thus, the fuel injection amount is set based on the intake pressure detected by the intake pressure sensor 33 and the engine speed.

When mode 4) (theoretical air-fuel ratio homogeneous mixture combustion) is selected, the ECU 30 further calculates the fuel injection amount calculated as described above from the air-fuel ratio sensor 29a so that the engine exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio. , 29b, air-fuel ratio control for feedback correction is performed.
The start catalyst (SC) 5a, 5b uses a carrier such as cordierite formed in a honeycomb shape, and a thin coating of alumina is formed on the surface of the carrier, and platinum Pt, palladium Pd, rhodium Rh, etc. are formed on the alumina layer. It is comprised as a three-way catalyst which supported the noble metal catalyst component. Three-way catalyst for purifying HC at the stoichiometric air-fuel ratio near, CO, three components of the NO _X at a high efficiency. Three-way catalyst, the air-fuel ratio of the inflowing exhaust gas because the reducing capacity of the higher becomes the NO _X than the stoichiometric air-fuel ratio decreases, to sufficiently purify NO _X in the exhaust gas when the engine 1 is a lean air-fuel ratio operation It is not possible.

  In the present embodiment, the SCs 5a and 5b mainly perform exhaust purification during the rich air-fuel ratio operation of the engine 1 immediately after the cold start, and exhaust purification when the engine 1 is operated at the stoichiometric air-fuel ratio during normal operation. For this reason, the SCs 5a and 5b are arranged near the engine 1 in the exhaust passages 2a and 2b so that the catalyst activation temperature can be reached in a short time after the engine is started to reduce the heat capacity. Therefore, it has a relatively small capacity.

Next, the NO _x storage reduction catalyst 7 of this embodiment will be described. The NO _x storage reduction catalyst 7 of the present embodiment uses, for example, alumina as a carrier, and on this carrier, for example, an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, or an alkaline earth such as barium Ba and calcium Ca. And at least one component selected from rare earths such as lanthanum La, cerium Ce, and yttrium Y, and a noble metal such as platinum Pt. When the air-fuel ratio of the exhaust gas _the NO _X storage reduction catalyst is flowing is lean, NO _X in the exhaust gas (nitrogen oxides) nitrate ion NO ₂ ^- was absorbed in the form of inflow exhaust gas is less stoichiometric air-fuel ratio ( performing absorption and release action of the NO _X that releases NO _X absorbed to become rich air-fuel ratio).

  This absorption / release mechanism will be described below using platinum Pt and barium Ba as an example, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.

When the oxygen concentration in the inflowing exhaust gas increases (that is, when the exhaust air-fuel ratio becomes lean), these oxygens adhere to the platinum Pt in the form of O ₂ ⁻ or O ²⁻ , and the NO _x in the exhaust gas on the platinum Pt. Reacts with O ₂ ⁻ or O ²⁻ , thereby producing NO ₂ . Further, the inflow NO ₂ and NO ₂ produced by the above exhaust platinum Pt on the further absorbed into the absorbent while being oxidized barium oxide BaO and bound with nitrate ions NO ₃ ^- in the form of absorbent Spread. For this reason, under a lean atmosphere, NO _x in the exhaust is absorbed in the form of nitrate in the NO _x absorbent.

Further, when the oxygen concentration in the inflowing exhaust gas is greatly reduced (that is, when the exhaust air-fuel ratio becomes smaller (richer) than the stoichiometric air-fuel ratio), the amount of NO ₂ generated on the platinum Pt is reduced, so that the reaction is reversed. The nitrate ions NO ₂ ⁻ in the absorbent are released from the absorbent in the form of NO ₂ . In this case, if a reducing component such as CO or a component such as HC or CO ₂ is present in the exhaust gas, NO ₂ is reduced by these components on platinum Pt.

In the present embodiment, as described above, in normal operation, the engine 1 is operated at a lean air-fuel ratio in most load regions except for high load operation, and the NO _X storage reduction catalyst absorbs NO _X in the inflowing exhaust gas. To do. When the engine 1 is operated at a rich air-fuel ratio, the NO _x storage reduction catalyst 7 releases the absorbed NO _x and reduces and purifies it. Therefore, when the amount of NO _X absorbed in the NO _X occluding and reducing catalyst 7 in a conventional lean air-fuel ratio during operation increases, performs the rich spike operation for switching a short time the engine air-fuel ratio from a lean air-fuel ratio to a rich air-fuel ratio, NO _X Release of NO _X from the storage reduction catalyst and reduction purification (regeneration of the NO _X storage reduction catalyst) are performed.

However, when the rich spike operation of the engine 1 is performed, it has been found that unpurified NO _x is released from the NO _x storage reduction catalyst immediately after switching from the lean air fuel ratio to the rich air fuel ratio. This is presumably because the HC and CO components in the exhaust gas may be insufficient when the engine is switched from lean air-fuel ratio operation to rich air-fuel ratio operation. That is, when switching from lean to rich, the exhaust air-fuel ratio continuously changes, but at this time the rich air-fuel ratio is low, but the richness is low and the HC and CO components in the exhaust gas pass through a relatively small region. In this region, it is considered that HC and CO components in the exhaust gas are insufficient and the total amount of NO _x released from the NO _x storage reduction catalyst cannot be reduced.

Therefore, in the present embodiment, when NO _X should be released from the NO _X storage reduction catalyst, the secondary fuel injection is performed in the expansion or exhaust stroke after the main fuel injection, and the exhaust air-fuel ratio is suddenly made a considerably rich air-fuel ratio. This prevents the release of unpurified NO _x from the NO _x storage reduction catalyst. The fuel injected in the expansion or exhaust stroke after combustion of the fuel supplied into the cylinder by the main fuel injection is not combusted but comes into contact with the high-temperature burned gas and vaporizes and generates low molecular weight HC. Further, since the fuel supplied by the secondary fuel injection does not contribute to the combustion in the cylinder, the engine output torque does not increase even if a relatively large amount of fuel is supplied by the secondary fuel injection.

Therefore, by performing secondary fuel injection when NO _X should be released from the NO _X storage reduction catalyst, the exhaust air-fuel ratio can be rapidly changed to a low value without causing fluctuations in engine output torque. Thus, NO _X in the storage reduction catalyst without passing through the air-fuel ratio of the intermediate, unpurified in the NO _X release at the initial from possible and becomes _the NO _X storage reduction catalyst by supplying a high degree of rich exhaust NO _X Is prevented from being released. Incidentally, the release of the NO _X from _the NO _X storage reduction catalyst can be also be carried out by only the secondary fuel injection, the rich spike early only secondary when performing normal rich spike by increasing the main fuel injection amount Fuel injection may be performed so that the exhaust air-fuel ratio is suddenly switched to the rich air-fuel ratio.

However, when a part of the fuel injected by the secondary fuel injection remains in the cylinder during the secondary fuel injection, the engine output torque may vary. As described above, the ECU 30 calculates the required fuel amount based on the engine load state (accelerator opening degree, rotation speed) and supplies it to the cylinder by main fuel injection. For this reason, when residual fuel is generated by secondary fuel injection, in the next cycle, the residual fuel is burned in the cylinder in addition to the fuel supplied by main fuel injection. There is a problem that engine output torque increases and torque fluctuation occurs.
This problem can be solved by the two methods described below.

(A) The entire amount of fuel injected by the secondary fuel injection is discharged outside the cylinder during the exhaust stroke (when the exhaust valve is open) so that no residual fuel is generated.
(B) When residual fuel is generated, the fuel injection amount at the next main fuel injection is corrected by reducing the residual fuel amount so that the fuel amount contributing to combustion matches the target injection amount of the main fuel injection. .

Hereinafter, an embodiment in which each method is employed will be described.
(1) First Embodiment This embodiment is a reference embodiment not directly related to the invention described in the claims.
In this embodiment, fluctuations in engine output torque due to secondary fuel injection are prevented by discharging the entire amount of fuel injected by secondary fuel injection out of the cylinder during the exhaust stroke.

FIG. 2 is a view showing a longitudinal section of a cylinder of the engine 1. FIG. 2 shows a cross section of the # 1 cylinder, but the configurations of the # 2 to # 4 cylinders are the same as those in FIG.
In FIG. 2, 10 is a cylinder combustion chamber, 11 is a piston, 13 is an intake port, 13a is an intake valve, 15 is an exhaust port, and 15a is an exhaust valve. Reference numeral 111 denotes an in-cylinder fuel injection valve, and reference numeral 17 denotes a spark plug provided at the center of the cylinder head cylinder. In the present embodiment, a concave piston cavity 11 a is provided on the top surface of the piston 11. The cavity 11a plays a role of concentrating fuel injected from the fuel injection valve 111 in the second half of the compression stroke at the time of lean air-fuel ratio operation in the vicinity of the spark plug 17 and generating a mixture layer of combustible air-fuel ratio in the vicinity of the plug 17. .

  That is, in the above-described main fuel injections of 1) lean air-fuel ratio stratified combustion (compression stroke once injection) and 2) lean air-fuel ratio homogeneous mixture / stratified combustion (intake stroke / double compression stroke injection), the compression stroke When the piston reaches a sufficiently raised position in the second half, fuel having a relatively strong penetration force (high injection pressure) is injected from the in-cylinder fuel injection 111 toward the piston cavity 11a.

  At this time, the injected fuel reaches the surface of the piston cavity 11a and flows along the curved surface of the cavity 11a. The side surface 11b of the cavity 11a far from the fuel injection valve 111 is formed with a relatively large curvature (the curvature radius is small) so that the fuel flowing along the surface of the cavity 11a drifts toward the vicinity of the spark plug 17. It has become. As a result, the fuel injected from the fuel injection valve 111 is stratified in the vicinity of the spark plug 17.

  In the present embodiment, the entire amount of fuel injected by the secondary fuel injection is discharged from the exhaust port 15 using the piston cavity 11a. In other words, in the present embodiment, the fuel injection timing is set at the time when the crank angle is delayed by 360 degrees from the fuel injection timing at which the main fuel injection is performed in the latter half of the exhaust stroke. Thus, when the secondary fuel injection is performed, the piston 11 is in the same position as when the main fuel injection (hereinafter referred to as “compression stroke fuel injection”) for stratifying the air-fuel mixture is performed. For this reason, the fuel injected by the secondary fuel injection is deflected by the curved surface 11b as in the main fuel injection, and flows toward the spark plug 17 (that is, the exhaust port 13).

  However, since the exhaust valve 15a is open in the latter half of the exhaust stroke, the secondary injected fuel drifted in the above manner does not stratify around the spark plug 17 as shown by F in FIG. The gas is discharged from the port 13 to the outside of the cylinder. For this reason, it is prevented that the residual fuel in a cylinder by secondary fuel injection arises. In this case, the injected fuel comes into contact with the surface of the piston cavity 11a. However, since the piston is at a high temperature during operation, the fuel that has come into contact with the surface of the cavity 11a is immediately vaporized and adheres to the surface of the cavity 11a. Never do.

  By the way, in order to discharge the entire amount of fuel injected by the secondary fuel injection to the outside of the cylinder as described above, all of the fuel is exhausted from the exhaust port 15 until the intake valve 13a starts to open during the exhaust stroke. It is necessary to finish discharging from. If fuel remains in the cylinder during the period in which the exhaust valve 15a and the intake valve 13a are simultaneously open (valve overlap period), part of the fuel flows back to the intake port and again in the next intake stroke. This is because there is a possibility that a part of the secondary injected fuel will remain in the cylinder. Further, the engine 1 of this embodiment includes a variable valve timing device 200, and the valve timing is changed according to the engine load state. Therefore, in the present embodiment, when the secondary fuel injection is executed, the opening timing of the intake valve is read, and the amount of fuel injected by the secondary fuel injection is changed by changing the secondary fuel injection amount according to the intake valve opening timing. It is prevented from flowing back into the intake port and remaining in the cylinder.

FIG. 3 is a flowchart for explaining the fuel injection control operation in the present embodiment. This operation is performed by a routine executed by the ECU 30 at every constant crankshaft rotation angle.
When the operation starts in FIG. 3, it is determined in step 301 whether secondary fuel injection is requested. In the present embodiment, the amount of NO _x absorbed by the NO _x storage reduction catalyst 7 is estimated based on the engine operating state by a separately executed routine that is not shown, and when the amount of absorbed NO _x reaches a predetermined value. Secondary fuel injection (rich spike) is required.

Instead of estimating the NO _X absorption, when predetermined time has elapsed since the last of the NO _X emission operation execution, or when the engine speed integrated value from the previous NO _X emission operation execution has reached a predetermined value Alternatively, the secondary fuel injection may be requested on the assumption that the amount of absorbed NO _x of the NO _x storage reduction catalyst has reached a predetermined value.

  If secondary fuel injection is not requested in step 301, this operation is immediately terminated without executing steps 303 to 321 and secondary fuel injection is not performed. On the other hand, if secondary fuel injection is requested in step 301, then step 303 is executed to calculate the target value qinjex of the secondary fuel injection amount. In step 303, a secondary fuel injection amount qinjex necessary for obtaining a desired air-fuel ratio is calculated from the air amount Q taken into the cylinder per engine revolution and the main fuel injection amount.

  In the present embodiment, the relationship between the engine speed N, the load (accelerator opening) ACCP, and the cylinder intake air amount Q per engine rotation is obtained in advance by experiments, and the ECU 30 is configured in the form of a numerical map using N and ACCP. Stored in ROM. The main fuel injection amount is also stored in the ROM of the ECU 30 as a numerical map of N and ACCP. Therefore, in step 303, the current load condition (N, ACCP) is used to calculate the intake air amount Q and the main fuel injection amount from these numerical maps, and is required to set the exhaust air / fuel ratio to the target value. A secondary fuel injection amount qinjex is calculated.

After calculating the secondary fuel injection amount qinjex, in step 305, the calculated secondary fuel injection amount qinjex (ml) is used for the fuel injection time (fuel injection) using the fuel pressure in the common rail 110 and the characteristic value of the in-cylinder fuel injection valve. Valve opening time) Converted to tauex (ms).
In step 307, the intake valve opening timing (crank angle) IO currently set by the variable valve timing device 200 is read. In step 309, the currently allowable maximum secondary fuel injection time (guard value) tauexmax is calculated. .

In the present embodiment, as described above, the entire amount of fuel injected by the secondary fuel injection from the fuel injection valve needs to be discharged out of the cylinder before the intake valve is opened. In this embodiment, the timing of secondary fuel injection is fixed (lagging 360 degrees from the compression stroke injection timing). Therefore, it is necessary to limit the maximum value of the fuel injection amount in order to discharge the entire amount of injected fuel outside the cylinder before the intake valve is opened. In step 309, the difference between the intake valve opening crank angle IO read in step 307 and the secondary fuel injection start crank angle ainjc + 360 (ainjc is the compression stroke main fuel injection timing) and the current engine speed N are used. Then, the time t ₁ (ms) from the start of fuel injection to the opening of the intake valve is calculated.

Further, in order for the fuel injected in the final stage of secondary fuel injection to be discharged from the exhaust port, time t ₂ required for the flight from the fuel injection valve to the exhaust port is required. Here, t ₂ is determined by the pressure in the common rail 110. Therefore, in this embodiment, if the fuel injection from the fuel injection valve does not end within the time (t ₁ -t ₂ ) after the start, residual fuel may be generated in the cylinder. Therefore, in step 309, the above-mentioned t ₁ and t ₂ are calculated using the intake valve opening crank angle IO, the engine speed N, and the fuel pressure in the common rail, and the maximum fuel injection time tauexmax is set to tauexmax = t ₁ −t. Calculated as ₂ .

Next, in steps 311 to 317, the target secondary fuel injection time tauex set in step 305 is limited by the maximum value tauexmax and the minimum value taumin, and the value of tauex is set in the range of taumin ≦ tauex ≦ tauexmax. The minimum value tauemin is a controllable minimum valve opening time of the fuel injection valve 111 and is a characteristic value of the fuel injection valve 111.
In step 319, the secondary fuel injection start timing ainjex is set to ainjex = ainjc + 360, and in step 321, ainjex and tauex are set in a fuel injection circuit (not shown). As a result, the secondary fuel injection is started at the crank angle ainjex, and the tauex time injection is performed.

  As described above, in the present embodiment, the fuel injected by the secondary fuel injection using the piston cavity 11a drifts to the exhaust port 13, and the fuel injection amount is controlled according to the engine load state and the valve timing. Thus, the entire amount of fuel injected by the secondary fuel injection can be discharged out of the cylinder during the exhaust stroke.

In the example of FIG. 2, the flow of fuel injected by the secondary fuel injection is drifted toward the exhaust port by the cavity 11a formed on the top surface of the piston. It may be made to drift toward the exhaust port.
For example, the fuel injection valve is configured as an air assist valve that injects pressurized air together with fuel, and the injected fuel is exhausted by assist air by injecting pressurized air toward the exhaust port only during secondary fuel injection. It is also possible to drift to the port side.

In addition, when a single fuel injection valve has a structure in which the injection direction can be switched between main fuel injection and secondary fuel injection, the fuel injection direction is set to the exhaust port or the exhaust port at the time of secondary fuel injection. You may make it switch toward the drift which heads.
Further, in the example of FIG. 2, the main fuel injection and the secondary fuel injection are performed by the same fuel injection valve, but a sub fuel injection valve dedicated for secondary fuel injection is provided separately from the fuel injection valve for main fuel injection. The injection direction of the auxiliary fuel injection valve may be set toward the exhaust port.

Further, instead of the piston cavity, a drift plate that protrudes into the cylinder only at the time of secondary fuel injection is provided, and the flow of fuel injected by the secondary fuel injection collides with the drift plate to direct the fuel to the exhaust port. You may make it flow.
(2) Second Embodiment Next, a second embodiment will be described. This embodiment is a reference embodiment not directly related to the invention described in the claims.
Similar to the first embodiment described above, in this embodiment as well, the entire amount of fuel injected by the secondary fuel injection is discharged outside the cylinder during the exhaust stroke, so that fluctuations in the engine output torque due to the secondary fuel injection are reduced. It is preventing.

FIG. 4 is a view similar to FIG. 2 showing a cylinder cross section of the engine 1. 4, the same reference numerals as those in FIG. 2 denote the same elements as those in FIG.
In this embodiment, the secondary fuel injection is performed at an early stage of the exhaust stroke where the piston is close to bottom dead center, and the injection pressure (common rail pressure) of the secondary fuel injection is lower than the pressure at the time of main fuel injection. Set. Thus, the burnt gas pressure in the cylinder is high at the early stage of the exhaust stroke, and a relatively strong exhaust flow toward the exhaust port is generated in the cylinder as indicated by the arrow in FIG. When secondary fuel injection is performed at a relatively low injection pressure at this time, as shown by F in FIG. 4, the injected fuel penetrates the exhaust flow in the cylinder and does not reach the cylinder wall or the piston. It is transported to the exhaust port by the exhaust stream near the center. For this reason, the injected fuel does not adhere to the cylinder wall, piston, cylinder head, etc., and the entire amount of fuel injected by the secondary fuel injection is discharged outside the cylinder during the exhaust stroke, resulting in residual fuel in the cylinder. Absent.

  In the above-described embodiment, in order to discharge the entire amount of fuel injected by the secondary fuel injection until the intake valve is opened to the outside of the cylinder, the secondary fuel depends on the engine operating state (load state) and the valve timing. Although the injection amount is controlled, the timing of secondary fuel injection is important in this embodiment. In other words, if the fuel injection timing is delayed, part of the injected fuel may flow backward to the intake port, and if the fuel injection timing is too early, the injected fuel will diffuse into the cylinder and the entire amount will ride on the exhaust flow. This is because there is a possibility that it will not be discharged outside the cylinder. Hereinafter, control of the fuel injection timing in the present embodiment will be described.

FIG. 5 is a flowchart for explaining the fuel injection control operation in the present embodiment. This operation is performed by a routine executed by the ECU 30 at every constant crankshaft rotation angle.
When the operation starts in FIG. 5, it is determined in step 501 whether secondary fuel injection is necessary, in step 503 the target value qinjex of the secondary fuel injection amount is calculated, and in step 505 the injection time tauex is calculated from the target injection amount qinjex. Is calculated. The calculation of the target injection amount qinjex in step 503 and the injection time tauex in step 505 are performed by the same method as in steps 303 and 305 in FIG. 3, respectively. Since 110 pressure is controlled to be low, the injection time tauex is longer than that in FIG. 3 even when the target injection amount qinjex is the same as in FIG.

After calculating qinjex and tauex as described above, in this embodiment, the current intake valve opening timing (crank angle) IO and exhaust valve opening timing (crank angle) EO are read in step 507, and in step 509, the fuel injection valve 111 is read. is injected fuel flight time t ₂ until it is discharged from the exhaust port, it is calculated as t ₂ = alpha + beta from. Here, α is a time required for the fuel injected from the fuel injection valve 1112 to reach the center of the cylinder, and is a time proportional to the common rail 110 pressure (fuel injection pressure). Β is the time required for the fuel that has reached the center to be discharged from the exhaust port on the exhaust flow, and is proportional to the engine speed N.

After calculating the flight time t ₂ in step 509, in step 511, the maximum value (guard value) tauexmax of the secondary fuel injection time is calculated as tauexmax = t ₃ −t ₂ .
Here, t ₂ is the time from when the exhaust valve is opened until the intake valve is opened, using the opening timings IO and EO of the intake and exhaust valves and the engine speed N read at step 507. Calculated. That is, tauexmax is the injection time corresponding to the maximum fuel injection amount that can be discharged out of the cylinder without causing backflow of injected fuel in the intake port when secondary fuel injection is performed at the same time as the exhaust valve is opened. It is.

After calculating tauexmax in step 511, in steps 513 to 517, the target injection time tauex calculated in step 505 is limited by the maximum value tauexmax and the minimum value taumin, and in step 521, the intake valve opening timing IO and the engine speed N The secondary fuel injection start timing ainjex is calculated based on tauex after the restriction. That is, the secondary fuel injection start timing is earlier than the intake valve opening timing by (tauex + t ₂ ), that is, the fuel injected at the end of the secondary fuel injection is discharged from the exhaust port immediately before the intake valve opening. Start at the timing. That is, in this embodiment, the secondary fuel injection timing is advanced as the secondary fuel injection amount increases. As a result, all of the fuel injected by the secondary fuel injection reaches the exhaust port before the intake valve opens, and the fuel injected by the secondary fuel injection timing becomes too early. It is prevented from diffusing inside.

  In the second embodiment described above, the fuel injection direction of the in-cylinder fuel injection valve 111 is the same as that of the embodiment of FIG. 2, but for example, as shown in FIG. If the in-cylinder fuel injection valve is provided to inject the fuel toward the center of the cylinder at a low fuel injection pressure during the secondary fuel injection, the residual fuel prevention effect is further enhanced.

(3) Third Embodiment Next, a third embodiment will be described.
The present embodiment is an embodiment corresponding to the invention described in the claims.
In this embodiment, assuming that a part of the fuel injected by the secondary fuel injection remains in the cylinder when the secondary fuel injection is performed, the residual fuel amount is calculated from the engine operating state, and the next main fuel is The fuel injection amount at the time of injection is corrected to decrease by the amount of residual fuel. As a result, the amount of fuel supplied into the cylinder at the time of main fuel injection (contributing to combustion) accurately matches the target injection amount of main fuel injection. This prevents engine output torque fluctuations from occurring even when residual fuel is produced during secondary fuel injection.

First, a method for calculating the residual fuel amount in the secondary fuel injection in the present embodiment will be described.
FIG. 7 is a graph showing the relationship between the engine output torque (vertical axis) and the main fuel injection amount (horizontal axis) when the engine is operated at a predetermined constant rotational speed. In FIG. 7, curve I shows the relationship between the output torque and the main fuel injection amount when only the main fuel injection is not executed, and curve II executes the secondary fuel injection in addition to the main fuel injection. In this case, the relationship between the output torque and the main fuel injection amount is shown. As described above, the secondary fuel injection amount is set to an amount necessary for setting the exhaust air-fuel ratio to the target air-fuel ratio in each case, and is determined from the engine load (main fuel injection) and the rotational speed. Is done. In this case, the secondary fuel injection timing may be set by any of the methods described above, or may be fixed at a certain appropriate crank angle.

As described above, the engine output torque is the same regardless of the presence or absence of the secondary fuel injection unless the residual fuel is originally generated by the secondary fuel injection. However, if residual fuel is generated by secondary fuel injection, the engine output torque at the time of secondary fuel injection increases by an amount corresponding to the amount of residual fuel (curve II in FIG. 7).
That is, it is assumed that the output torque is increased by the amount of main fuel injection at the time of secondary fuel injection as indicated by a in FIG. Further, it is assumed that the output torque increase amount at this time is equal to the case where the main fuel injection amount is increased by the amount indicated by b in FIG. In this case, since the output torque increase amount a is caused by the combustion of the residual fuel in the cylinder by the secondary fuel injection, the residual fuel amount is the main fuel injection amount required to increase the output torque by the same amount, that is, It should be equal to the amount of fuel shown in 7b. Therefore, in this embodiment, when the increase amount of the output torque by the secondary fuel injection is the amount indicated by a in FIG. 7, it is assumed that the amount indicated by b in FIG. 7 is equal to the residual fuel amount in the cylinder. Estimate the amount of residual fuel.

  That is, in the present embodiment, a curve corresponding to FIG. 7 is created in advance for each combination of each engine speed and fuel injection modes 1) to 5), which will be described later, and the residual amount at each main fuel injection amount. The amount of fuel (FIG. 7, b) has been calculated. The value of the residual fuel amount b is created for each fuel injection mode as a numerical map using the engine speed N and the main fuel injection amount (qinj = qinjei + qinjec) as parameters, and is stored in the ROM of the ECU 30. During engine operation, the ECU 30 calculates the residual fuel amount in the cylinder at the time of performing the secondary fuel injection based on the engine speed N and the main fuel injection amount qinj. Here, qinjei is the injection amount in the first main fuel injection during the intake stroke, qinjec is the injection amount in the second main fuel injection in the compression stroke, and qinj is the total amount of both.

Also in this embodiment, the fuel injection modes of the engine 1 are the following five types.
1) Lean air-fuel ratio stratified charge combustion (one compression stroke injection)
2) Lean air-fuel ratio homogeneous mixture / stratified combustion (intake stroke / compression stroke twice injection)
3) Lean air / fuel ratio homogeneous mixture combustion (intake stroke one injection)
4) Theoretical air-fuel ratio homogeneous mixture combustion (intake stroke one injection)
5) Rich air-fuel ratio homogeneous mixture combustion (intake stroke one injection)
In the present embodiment, in the case of mode 3) (intake stroke / double compression stroke injection), the correction is performed by reducing the fuel injection amount in the intake stroke injection by the amount of residual fuel. The residual fuel diffuses into the cylinder and becomes a part of the homogeneous mixture, and the air-fuel ratio of the homogeneous mixture formed in the cylinder is directly affected. In this embodiment, in order to prevent this, the air-fuel ratio of the actually generated homogeneous mixture is maintained at the target value by reducing the amount of intake stroke fuel injection that generates the homogeneous mixture by the amount of residual fuel. It is doing so.

FIG. 8 is a flowchart for explaining the main fuel injection control operation of the present embodiment. This operation is executed at every constant rotation angle of the engine crankshaft.
In FIG. 8, when the operation starts, in step 801, the engine load (accelerator opening) ACCP and the rotational speed N are read. In Steps 803, 811 and 823, it is determined which one of the fuel injection modes 1) to 4) is adopted based on the accelerator opening ACCP and the rotational speed N.

  That is, in step 803, fuel injection mode 3) lean air-fuel ratio homogeneous mixture combustion (intake stroke single injection) or 4) stoichiometric air-fuel ratio homogeneous mixture combustion (intake stroke single injection) or lean air-fuel ratio homogeneous mixture combustion ( It is determined from ACCP and N whether or not the intake stroke injection is to be adopted. If mode 3) or 4) or 5) is to be adopted, the ECU 30 in advance based on ACCP and N in step 805. The intake stroke fuel injection amount qinjei is calculated from the numerical map stored in the ROM. In step 807, the compression stroke fuel injection amount qinjec is set to zero.

  Next, in step 809, the total qinj of qinjei and qinjec is calculated, and the in-cylinder residual fuel amount b when the secondary fuel injection is performed is determined based on the rotational speed N and the main fuel injection amount qinj. ) Or 4) from the relationship of FIG. In step 817, it is determined whether or not there is a request for secondary fuel injection at present. If there is a request, the process proceeds to step 819, and the intake stroke fuel injection amount qinjei is corrected to decrease by the residual fuel amount b. Then, the corrected intake stroke fuel injection amount qinjei and the compression stroke fuel injection amount qinjec (in this case, qinjec = 0) are set in the fuel injection circuit, and the operation is terminated. Thereby, when the secondary fuel injection is performed, the main fuel injection amount is corrected to decrease by the residual fuel amount b, so that the engine output torque fluctuation is prevented from occurring even when the secondary fuel injection is performed.

  On the other hand, if none of the fuel injection modes 3), 4), and 5) is adopted in step 803, the process proceeds to step 811 and fuel injection mode 2) (lean air-fuel ratio homogeneous mixture / stratified combustion (intake) It is determined whether or not the stroke / compression stroke injection)) should be adopted, and if mode 2) is adopted, it is determined from the numerical map previously stored in the ROM of the ECU 30 based on ACCP and N in step 813. An intake stroke fuel injection amount qinjei and a compression stroke fuel injection amount qinjec are calculated. In step 815, the residual fuel amount b at the time of performing the secondary fuel injection is calculated from the relationship of FIG. 7 in mode 2), and the operations after step 817 are performed. That is, also in this case, only the intake stroke fuel injection amount qinjei is corrected to decrease by the residual fuel amount b, and the compression stroke fuel injection amount qinjec is not corrected.

  On the other hand, if none of the fuel injection modes 2) to 5) is adopted in steps 803 and 801, the fuel injection mode 1) (lean air-fuel ratio stratified combustion (compression stroke single injection)) is adopted, In step 823, the compression stroke fuel injection amount qinjec is calculated based on ACC and N, and the intake stroke fuel injection amount qinjei is set to zero. Also in this case, in step 827, the residual fuel amount b at the time of performing the secondary fuel injection is calculated from the relationship of FIG. 7 in mode 1), and in step 829, it is determined whether or not there is a secondary fuel injection request. In this case, if there is a request for secondary fuel injection, the compression stroke fuel injection amount qinjec is corrected to decrease by the residual fuel b in step 831 and step 821 is executed.

  In the present embodiment, as described above, the main fuel injection amount is corrected according to the residual fuel amount by the secondary fuel injection, thereby preventing the engine output torque fluctuation from being caused by the secondary fuel injection. In addition, in the mode 3) (when both the intake stroke and the compression stroke are injected), only the intake stroke fuel injection amount is corrected in the above correction, so that the homogeneous air-fuel ratio mixture is reduced. The air-fuel ratio becomes equal to the target value.

  In this embodiment, the correction is performed for each cycle using the relationship between the main fuel injection amount and the in-cylinder residual fuel amount obtained in advance by experiments. However, the engine output torque actually generated by the in-cylinder residual fuel is corrected. A change (a change indicated by a in FIG. 7) is detected from a change in engine speed, a change in in-cylinder combustion pressure, and the like, and a correction amount b of the main fuel injection amount is calculated from the relationship shown in FIG. You may do it. In this case, the correction of the main fuel injection amount is performed in the cycle following the cycle in which the torque change is detected.

Moreover, although each above-mentioned embodiment has demonstrated the engine which switches fuel-injection mode according to an engine operating state, fuel-injection mode is fixed to intake stroke fuel injection or compression stroke fuel injection, or both (2 times injection). It goes without saying that the present invention can also be applied to the selected engine.
Further, in each of the above embodiments, the case where the NO _x storage reduction catalyst is arranged in the exhaust passage has been described as an example, but the present invention is not limited to this embodiment, and all cases where secondary fuel injection is performed. Needless to say, it is applicable to the above. For example, in the case where a selective reduction catalyst that reduces NO _x by selectively reacting HC (or HC adsorbed on the catalyst) in the exhaust with NO _x in the exhaust passage at a lean air-fuel ratio is disposed. Although it is necessary to supply HC to the selective reduction catalyst, the present invention can also be applied to a case where HC is supplied to the selective reduction catalyst by secondary fuel injection.

It is a figure explaining the schematic structure of embodiment at the time of applying this invention to the gasoline engine for motor vehicles. It is a cylinder longitudinal section explaining a reference embodiment of the present invention. It is a flowchart explaining the secondary fuel injection control operation of the reference embodiment of FIG. It is a cylinder longitudinal section explaining another reference embodiment of the present invention. It is a flowchart explaining the secondary fuel injection control operation of the reference embodiment of FIG. It is a figure similar to FIG. 4 explaining the modification of reference embodiment of FIG. It is a figure explaining the calculation method of the residual fuel amount of embodiment of this invention. It is a flowchart explaining the main fuel injection control operation of embodiment of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine main body 11 ... Piston 11a ... Piston cavity 15 ... Exhaust port 15a ... Exhaust valve 111-114 ... In-cylinder fuel injection valve 200 ... Variable valve timing device 30 ... Engine control unit (ECU)
7 ... NO _X occluding and reducing catalyst F ... injected fuel

Claims (2)

An in-cylinder fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine;
The in-cylinder fuel injection valve is controlled to perform main fuel injection for injecting fuel that contributes to combustion in the cylinder, and if necessary, combustion in the cylinder during the expansion stroke or exhaust stroke after the main fuel injection Fuel injection control means for performing secondary fuel injection for injecting fuel that does not contribute to
The fuel injection control means calculates the amount of fuel remaining in the cylinder among the fuel injected by the immediately preceding secondary fuel injection and corrects the injection amount of the main fuel injection according to the residual fuel amount. A fuel injection device for an internal combustion engine. An in-cylinder fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine;
The in-cylinder fuel injection valve is controlled to perform main fuel injection for injecting fuel that contributes to combustion in the cylinder, and if necessary, combustion in the cylinder during the expansion stroke or exhaust stroke after the main fuel injection Fuel injection control means for performing secondary fuel injection for injecting fuel that does not contribute to
The fuel injection control means converts the main fuel injection into a first main fuel injection for generating a homogeneous mixture in the cylinder and a second main fuel injection for generating a layer of combustible mixture as necessary. When the secondary fuel injection is executed, the amount of fuel remaining in the cylinder is calculated from the fuel injected by the immediately preceding secondary fuel injection, and the second fuel injection is performed according to the residual fuel amount. A fuel injection device for an internal combustion engine that corrects an injection amount of one main fuel injection.

Images