JPH11200935A - Control unit of direct-injection internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem as worsening those of drivability and exhaust composition, especially hydrocarbon discharge by installing a compensation means compensating a span of ignition timing in the timing delay direction in time of misfire detection at the stratified combustion, in a device which makes an engine perform the stratified combustion by mainly spraying fuel at the latter half of a compression stroke at the specified driving area. SOLUTION: A control unit 11 is equipped with an air flow meter 12, a crank angle sensor 13, a water temperature sensor 14 or the like, and it controls those of fuel injection quantity, injection timing and fuel pressure on the basis of a signal out of a driving state detecting means. At a low speed, low load area, a stratified combustion is carried out by mainly spraying fuel at the latter half of a compression stroke, and at the driving area other than that, the fuel is mainly sprayed to a suction stroke, through which a harogeneous combustion is carried out. At this time, after those of fuel injection timing and ignition timing at a stratified driving state are determined, a fact of whether there is a complete misfire or not is judged. If the misfire has occurred in this time, the ignition timing is compensated in the timing delay direction. With this, a span of carburetion time for fuel injection is prolonged and an air-fuel ratio of mixture in and around a spark plug is leaned, and thus a problem on any possible misfire is solved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of fuel injection timing and ignition timing of a direct injection spark ignition engine.

[0002]

2. Description of the Related Art A fuel injection valve, which is disposed with a fuel injection nozzle facing a combustion chamber, directly injects fuel into a cylinder during a compression stroke to form a stratified mixture, which is ignited and burned. 2. Description of the Related Art There is generally known a direct injection type internal combustion engine that improves fuel efficiency.

[0003] In such stratified combustion, since the mixture ratio of fuel and air cannot be made rich to a certain degree or more, in an operation region where a high load is required, fuel is injected during the intake stroke to obtain a homogeneous fuel. It is common to have a homogeneous combustion operation mode for forming and burning a mixture.

As described above, in an engine that operates by switching between homogeneous combustion and stratified combustion, stratified combustion is performed by injecting fuel mainly in the latter half of the compression stroke at low speeds and low loads, and at other rotations and loads. There are two operating regions in which fuel is injected mainly during the intake stroke to perform homogeneous combustion. (Refer to, for example, Japanese Patent Application Laid-Open No. Sho 60-30435 for known literature of this type of direct injection internal combustion engine.)

[0005]

In such a direct-injection type internal combustion engine, combustion deposits called deposits are generated in the cylinders over a long period of operation. If this deposit accumulates on the piston crown, etc., part of the injected fuel is temporarily adsorbed on the deposit and desorbed during intake in the next and subsequent cycles, so that the air-fuel ratio becomes too rich and soot is easily generated. . If soot adheres to the electrode of the spark plug, the spark itself will not occur and it will be in a complete misfire state, so drivability, exhaust composition,
In particular, there is a problem that the HC emission is deteriorated.

[0006]

A first aspect of the present invention is a means for detecting an engine operating state, a means for setting a fuel injection timing and an ignition timing according to the engine operating state, Control means for controlling the fuel injection device and the ignition device in accordance with the timing, and in a predetermined predetermined operation region, the fuel is mainly injected in the latter half of the compression stroke to perform stratified charge combustion, and The ignition engine includes a means for detecting misfire and a correction means for correcting the ignition timing in a retard direction when misfire is detected during stratified combustion.

According to a second aspect of the present invention, there is provided a means for detecting an engine operating state, a means for setting a fuel injection timing and an ignition timing in accordance with the engine operating state, and a fuel in accordance with the set injection timing and the ignition timing. A control means for controlling the injection device and the ignition device, and in a predetermined predetermined operating region, in a direct injection type spark ignition engine in which fuel is mainly injected in the latter half of the compression stroke to perform stratified combustion, a misfire occurs. The fuel injection system includes a detecting means and a correcting means for correcting the fuel injection timing in the advance direction when a misfire is detected during stratified combustion.

According to a third aspect of the present invention, there is provided a means for detecting an engine operating state, a means for setting a fuel injection timing and an ignition timing in accordance with the engine operating state, and a fuel in accordance with the set injection timing and the ignition timing. Control means for controlling the injection device and the ignition device, in a predetermined predetermined operating region, in a direct injection type spark ignition engine in which fuel is mainly injected in the latter half of the compression stroke to perform stratified combustion, And a correction unit that corrects the ignition timing in the retard direction and corrects the fuel injection timing in the advance direction when misfire is detected during stratified combustion.

According to a fourth aspect of the present invention, there is provided a means for detecting an engine operating state, a means for setting a fuel injection timing and an ignition timing in accordance with the engine operating state, and a fuel in accordance with the set injection timing and the ignition timing. Control means for controlling the injection device and the ignition device, in a predetermined predetermined operating region, in a direct injection type spark ignition engine in which fuel is mainly injected in the latter half of the compression stroke to perform stratified combustion, A detecting means for correcting the ignition timing in a retard direction when misfiring in stratified combustion is detected, and a correcting means for correcting the fuel injection timing in an advancing direction when the misfire is not eliminated by the ignition timing correction.

According to a fifth aspect of the present invention, the correction means according to the third or fourth aspect of the present invention is configured to end the correction of the fuel injection timing preferentially when the misfire is resolved.

[0011] The invention of claim 6 is the invention of claims 1 to 4.
The correction means according to the invention is configured to continue the correction until the misfire is eliminated.

[0012] The invention of claim 7 is the first to fourth aspects of the present invention.
The correction means according to the invention is configured so that the correction is continued until a predetermined period of time elapses when a misfire is detected.

[0013]

According to the first aspect of the invention, the ignition timing is corrected in the retard direction when misfire is detected during stratified combustion.
As a result, the period until the fuel injected into the cylinder is ignited becomes longer, and the vaporization and diffusion of the fuel progresses accordingly, so that the air-fuel ratio of the air-fuel mixture near the spark plug is diluted, and the over-concentration due to deposit is compensated. You. For this reason, the combustion becomes relatively lean, soot generation is reduced, and the vicinity of the spark plug electrode is cleaned, so that misfire is eliminated.

According to the second aspect of the present invention, when misfire is detected during stratified charge combustion, the fuel injection timing is corrected in the advance direction. As a result, the period until ignition is lengthened, and vaporization and diffusion of fuel are promoted, so that misfire is eliminated in the same manner as in the first aspect of the invention.

According to the third aspect of the present invention, when misfire is detected during stratified charge combustion, both the ignition timing retard correction and the fuel injection timing advance correction are performed, so that the period from the supply of fuel into the cylinder to the ignition is increased. And the misfire can be eliminated more reliably by ensuring the maximum.

According to the fourth aspect of the invention, when a misfire is detected during stratified charge combustion, the ignition timing is first corrected in the retard direction, and when the misfire is not eliminated, the fuel injection timing is advanced next. Depending on the engine, if the injection timing is advanced, the fuel distribution in the combustion chamber may deviate from the expected state and the combustion may become unstable, so in particular, supply the injected fuel to the cavity provided in the piston crown surface. In this case, fuel may be supplied to the outside of the cavity due to advance of the injection timing, and combustion may be deteriorated. On the other hand, in the invention of claim 4, as described above, the ignition timing is first delayed, and the injection timing is advanced only when the misfire still does not disappear, so that the possibility of causing such inconvenience can be reduced. it can.

According to a fifth aspect of the present invention, when both the retardation correction of the ignition timing and the advance correction of the fuel injection timing are performed in the invention of the third or fourth aspect, when the misfire is eliminated, the fuel injection timing is first set. Since the advance angle correction is preferentially canceled, it is possible to minimize the operation time in a state where the combustion may be deteriorated with the advance of the injection timing described above.

According to the sixth aspect of the present invention, since the correction of the ignition timing or the fuel injection timing is continued until the misfire is eliminated in the first to fourth aspects of the present invention, the misfire state is reliably eliminated. As a result, the engine operation performance can be reliably returned to the state before the occurrence of misfire.

According to the present invention, the ignition timing or the fuel injection timing is corrected until a predetermined time elapses.
After the time has elapsed, the correction is released, so that the period during which the driving performance is reduced due to the correction of the ignition timing or the fuel injection timing is suppressed to a necessary limit while securing the misfire eliminating effect to some extent. be able to.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a main body (cylinder block) of a direct injection type internal combustion engine, 2 is a cylinder head, 3 is a piston, 4 is a spark plug, 5 is a fuel injection valve, 6 is an intake passage, 7 is an exhaust passage, Reference numeral 8 denotes a throttle valve, 9 denotes an intake valve, and 10 denotes an exhaust valve. 11 is a CPU, ROM, RAM, I
/ 0 and the like, and controls the fuel injection amount, injection timing, and fuel pressure based on signals from the following operating state detecting means.

The operating state detecting means includes an air flow meter 12, a reference signal (REF) for detecting a predetermined crank angle position of a specific cylinder, and a signal (P) for each crank angle.
OS), the crank angle sensor 13 and the water temperature sensor 1
4, exhaust oxygen sensor 15, throttle opening sensor 16,
A vehicle speed sensor 17 and a fuel pressure sensor 18 are provided. Reference numeral 20 denotes a fuel pressure control device that variably controls the pressure of fuel supplied to the fuel injection valve 5 based on a command from the control device.

FIG. 2 shows an example of setting when switching between stratified combustion and homogeneous combustion depending on the operating state of the engine.
In the low speed / low load region where the engine speed is N1 or less and the engine load T1 or less, the fuel is mainly injected in the latter half of the compression stroke to perform stratified combustion, and in the other operation regions, the fuel is mainly injected in the intake stroke. Perform homogeneous combustion.

The engine load and the number of revolutions are detected by the amount of intake air and the number of crank pulses per unit time, that is, detected by signals from the air flow meter 12 and the crank angle sensor 13. The fuel injection amount and injection timing are basically determined by these loads and rotation speeds.
Correction according to the operating state is performed based on signals from the water temperature sensor 14, the oxygen sensor 15, and the like.

FIG. 3 is a flowchart showing an example of the control operation according to the present invention under the above configuration. The operation will be described below with reference to this flowchart.

First, in step 301, the load (fuel injection amount Tp) and the number of revolutions N are detected. Next, in step 302, based on the detection result, stratified charge combustion is performed based on the operation range setting shown in FIG. It is determined whether it is in the operating range or the operating range in which homogeneous combustion is performed. If the engine is in the homogeneous operation region, the process proceeds to the control routine in the homogeneous operation region from step 304 to perform the fuel control and the ignition timing control in the homogeneous operation state. On the other hand, if it is determined in step 302 that the engine is in the stratified operation region, the process proceeds to step 303 to determine the fuel injection timing IT and the ignition timing ADV suitable for the stratified operation region by a method such as calculation or table search.

After determining the fuel injection timing IT and the ignition timing ADV in the stratified operation state, in the next step 305, it is determined whether or not there is a complete misfire in order to determine whether or not to correct the ignition timing. If a misfire has occurred at this time, the ignition timing A
DV is corrected in the retard direction. Various methods can be applied to the misfire determination as described later.

The fuel injection timing IT determined in this way
In step 309, the ignition timing ADV and the ignition timing ADV are output to the respective drive circuits, and fuel injection or ignition is performed at the corresponding timing. Such control is repeated periodically, and the presence / absence of ignition timing correction is controlled according to the presence / absence of misfire.

By delaying the ignition timing when a misfire is detected during stratified charge combustion, as described above, the vaporization time of the injected fuel becomes longer and the air-fuel ratio of the air-fuel mixture near the spark plug becomes leaner. Irrespective of the fuel vaporization, it is possible to suppress the enrichment of the air-fuel mixture, reduce soot adhering to the ignition plug, and eliminate misfire. When the misfire is eliminated in this way, the control shifts from step 305 to step 308, so that the ignition timing correction is canceled and the control returns to the normal ignition timing control.

FIG. 4 is a flowchart showing a second control example for eliminating a misfire. In this control, step 40
Steps 301 to 304 in FIG.
308, and determines whether the engine is in a stratified operation region or a homogeneous operation region based on the load and the number of revolutions, and determines and outputs a fuel injection timing IT and an ignition timing ADV corresponding to each of them. However, in the stratified operation, when it is determined that misfire has occurred in the misfire determination in step 405, the fuel injection timing IT is corrected in the advance direction in the next step 406, which is different from that in FIG.

By advancing the fuel injection timing in this manner, the period up to ignition is prolonged and vaporization and diffusion of the fuel are promoted, so that misfire is eliminated in the same manner as described above. When the misfire has been eliminated, the flow proceeds to step 407 in the subsequent control loop to cancel the fuel injection timing correction and return to the normal fuel injection timing.

The ignition timing correction and the injection timing correction described above may be used in combination, but in this case, the ignition timing is first corrected as shown in FIG. Is preferably corrected. This is because, as shown in FIG. 6, in the correction from the set point (the ignition timing or the injection timing in the normal state where no misfire has occurred), the advance correction of the injection timing is performed by changing the fuel distribution in the cylinder as described above. This is because there is a tendency to make it inappropriate, and there is less room to exceed the combustion stability limit as compared with the ignition timing retard correction. As shown in FIG. 6, when the ignition timing is advanced from the set point or the injection timing is delayed, the rich mixture is ignited in a state where the fuel and air are not sufficiently mixed, so that the soot Many occur and the misfire rate increases.

In FIG. 5, steps 501 to 504,
Reference numeral 510 corresponds to steps 301 to 304 and 308 in FIG. 3, and determines whether the engine is in a stratified operation region or a homogeneous operation region based on the load and the number of revolutions, and determines a fuel injection timing IT and an ignition timing ADV corresponding to each. And output. However, in the stratified operation, if it is determined that a misfire has occurred in the misfire determination in step 506, the ignition timing ADV is firstly retarded in the next step 507, and it is determined in the next step 508 that misfire still occurs. The fuel injection timing I
T is corrected in the advance direction.

If it is determined in step 506 that no misfire has occurred, neither the ignition timing ADV nor the fuel injection timing IT is corrected (step 51).
1, 512).

Here, prior to the misfire determination in step 506, it is determined in step 505 whether or not the injection timing IT is being retarded. If so, whether or not the fuel injection timing IT is corrected is determined. The routine jumps to the misfire determination routine of step 508 for determining the misfire. As a result, when the misfire is eliminated by the advance correction of the injection timing IT, first, the determination in step 508 determines that step 512
Then, the advance correction of the fuel injection timing IT is released, whereby the steps 505 to 50 are executed in the subsequent control loop.
When the misfire has been resolved in this state, the retard correction of the ignition timing ADV is released.

As described above, the correction of the ignition timing is prioritized over the correction of the fuel injection timing when a misfire occurs in the stratified operation, and the correction of the fuel injection timing is released prior to the correction of the ignition timing when the misfire is eliminated. Accordingly, it is possible to minimize the injection timing correction that may cause the drivability to deteriorate while ensuring the misfire eliminating effect.

In the control of each of the above embodiments, the correction amount of the ignition timing ADV or the fuel injection timing IT may be increased stepwise, or a predetermined correction amount may be given at a time. Good. Further, the cancellation of the correction may be performed on condition that the misfire has been eliminated, or may be canceled after a predetermined time regardless of the presence or absence of the misfire.

Further, the following various methods can be applied to the detection of misfire. The first is a technique for detecting fluctuations in the engine speed. When the detected fluctuation amount is larger than a predetermined reference value, it can be determined that a misfire has occurred. In this case, there is an advantage that misfire can be detected at low cost because the rotation fluctuation can be calculated using the signal of the crank angle sensor 13 (see FIG. 1). The second is a method of detecting an in-cylinder pressure during combustion by providing an in-cylinder pressure sensor. In this case, the misfire can be determined to some extent only by detecting the peak pressure. It is more reliable to determine from the effective pressure. When a misfire occurs, the indicated mean effective pressure becomes a negative value, so that the misfire can be detected accurately. Third is a method of providing an ion current detection sensor in the combustion chamber.
The ionic current is a current generated by the change of a combustion substance into a chemically ionized substance during combustion. Therefore, when a misfire occurs, this current does not occur, so that misfire can be determined. Fourth, there is a method that utilizes insulation resistance between electrodes of the ignition plug. It is generally known that smoldering of an ignition plug occurs when the insulation resistance becomes 10 Mohms or less. Therefore, the occurrence of a misfire can be detected by measuring the insulation resistance.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a mechanism portion and a control system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a stratified combustion operation region and a homogeneous combustion operation region.

FIG. 3 is a flowchart showing an outline of a first embodiment relating to a control operation of the present invention.

FIG. 4 is a flowchart showing an outline of a second embodiment.

FIG. 5 is a flowchart schematically showing a third embodiment.

FIG. 6 is an explanatory diagram showing a relationship between a correction direction of a fuel injection timing IT, an ignition timing ADV, and a stability limit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body (cylinder block) of a direct injection type internal combustion engine 2 Cylinder head 3 Piston 4 Spark plug 5 Fuel injection valve 6 Intake passage 7 Exhaust passage 8 Throttle valve 9 Intake valve 10 Exhaust valve 11 Control device 12 Air flow meter 13 Crank angle sensor 14 Water temperature Sensor 15 Exhaust oxygen sensor 16 Throttle opening sensor 17 Vehicle speed sensor 18 Fuel pressure sensor 20 Fuel pressure control device

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/34 F02D 41/34 F 45/00 345 45/00 345C 368 368Z F02P 5/15 F02P 5/15 B

Claims (7)

[Claims] A means for detecting an engine operating state; a means for setting a fuel injection timing and an ignition timing according to the engine operating state; and a fuel injection device and an ignition device according to the set injection timing and the ignition timing. A direct injection type spark ignition engine that performs stratified combustion by mainly injecting fuel in the latter half of the compression stroke in a predetermined predetermined operation region, and a means for detecting misfire; A control device for a direct injection internal combustion engine, comprising: correction means for correcting ignition timing in a retard direction when misfire is detected during stratified combustion. Means for detecting an engine operating state; means for setting a fuel injection timing and an ignition timing according to the engine operating state; a fuel injection device and an ignition device according to the set injection timing and the ignition timing A direct injection type spark ignition engine that performs stratified combustion by mainly injecting fuel in the latter half of the compression stroke in a predetermined predetermined operating region, and a means for detecting misfire; A control device for a direct-injection internal combustion engine, comprising: correction means for correcting fuel injection timing in an advance direction when misfire is detected during stratified combustion. 3. Means for detecting an engine operating state, means for setting a fuel injection timing and an ignition timing according to the engine operating state, a fuel injection device and an ignition device according to the set injection timing and the ignition timing A direct injection type spark ignition engine that performs stratified combustion by mainly injecting fuel in the latter half of the compression stroke in a predetermined predetermined operating region, and a means for detecting misfire; A control device for a direct injection internal combustion engine, comprising: correction means for correcting ignition timing in a retard direction and correcting fuel injection timing in an advance direction when a misfire is detected during stratified combustion. 4. Means for detecting an engine operating state, means for setting a fuel injection timing and an ignition timing according to the engine operating state, and a fuel injection device and an ignition device according to the set injection timing and the ignition timing A direct injection type spark ignition engine that performs stratified combustion by mainly injecting fuel in the latter half of the compression stroke in a predetermined predetermined operation region, and a means for detecting misfire; When misfire is detected during stratified charge combustion, the ignition timing is corrected in the retard direction, and when the ignition timing is not corrected by the ignition timing correction, the fuel injection timing is corrected in the advance direction. Control device for direct injection type internal combustion engine. 5. A direct injection type fuel injection system according to claim 3, wherein said correction means terminates the correction of the fuel injection timing preferentially when the misfire is eliminated. Control device for internal combustion engine. 6. The control device for a direct injection internal combustion engine according to claim 1, wherein said correction means is configured to continue the correction until the misfire is eliminated. . 7. The apparatus according to claim 1, wherein said correction means is configured to continue the correction until a predetermined time elapses when a misfire is detected. For direct injection type internal combustion engine.