JP2003227376A - Fuel injection control device for direct injection type engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a deterioration in fuel consumption or exhaust composition by enabling supply of fuel for raising temperature by one-time fuel injection, stabilizing fuel injection, and prompting a catalyst to activate in an early stage. <P>SOLUTION: The device is equipped with a fuel injection valve 3 injecting a fuel to an engine 1 and a catalyst 6 installed in an exhaust passage 5. When an activated state of the catalyst 6 is judged for example based on the catalyst temperature and the catalyst 6 is in non-activated state, one-time fuel injection is performed so that a fuel injection period covers the exhaust stroke and the intake stroke and a part of injection fuel is burned in the exhaust stroke. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for a direct injection engine.

[0002]

2. Description of the Related Art A catalyst is used to purify exhaust gas discharged from an engine, but the catalyst is not activated when the temperature is low such as immediately after the engine is started, and exhaust purification efficiency is reduced.

As disclosed in Japanese Unexamined Patent Publication No. 2000-73820, in order to raise the exhaust temperature and activate the catalyst early, the fuel injection is performed in the compression stroke and the expansion stroke separately from the injection during the normal operation. There is a method of injecting fuel and burning it in an exhaust stroke or an exhaust pipe.

[0004]

By the way, when the maximum injection amount of the engine is large, the orifice for limiting the fuel injection amount also becomes large. However, if the orifice is large, a small amount of fuel injection for raising the exhaust gas temperature mentioned above is performed. At times, it is necessary to shorten the injection period accordingly.

The fuel injection valve has a minimum injection period during which stable injection is possible. If the injection period becomes shorter than that, the amount of fuel injected tends to fluctuate, and if the injection amount is larger than the target value, exhaust gas is exhausted. If the amount is too small, the effect of increasing the temperature will be impaired.

Focusing on such a problem, the present invention makes it possible to supply the fuel for raising the temperature with a single fuel injection, thereby stabilizing the fuel injection and promoting the early activation of the catalyst, while improving the fuel consumption. The purpose is to prevent deterioration of the exhaust gas composition.

[0007]

SUMMARY OF THE INVENTION A first aspect of the present invention is a direct injection type engine having a fuel injection valve for injecting fuel into the engine and an exhaust purification catalyst installed in an exhaust system. And a fuel injection control means for performing one fuel injection such that the fuel injection period extends from the exhaust stroke to the intake stroke when the catalyst is in the inactive state. .

A second aspect of the present invention is a direct injection engine equipped with a fuel injection valve for injecting fuel into the engine and an exhaust purification catalyst installed in the exhaust system, and means for determining the activation state of the catalyst, When the catalyst is in the inactive state, the fuel injection is performed in two times, that is, the fuel injection timing during normal operation and the fuel injection timing later than this, or the fuel injection period is set to extend from the exhaust stroke to the intake stroke. And a fuel injection control unit that selects and executes one time of fuel injection according to operating conditions.

In a third aspect based on the first or second aspect, the one fuel injection period begins before the exhaust valve is closed and before the intake valve is opened, and the intake valve is opened and the exhaust valve is closed. Will end later.

In a fourth aspect based on the second aspect, the one-time fuel injection is selected when the fuel injection pulse width determined by the operating conditions of the two-time fuel injection is smaller than an allowable minimum pulse width. .

A fifth aspect of the invention is the fuel cell system according to the first or second aspect of the invention, in which fuel injection after the two fuel injections is performed in a compression stroke or an expansion stroke.

According to a sixth aspect of the present invention, in the first to fifth aspects, a valve timing variable device for changing the opening / closing timing of the intake valve and the exhaust valve of the engine is further provided, and the fuel injection control means is the exhaust valve closing timing. The injection timing of the one-time fuel injection is corrected according to at least one of the intake valve opening timings.

In a seventh aspect based on the sixth aspect, when the closing timing of the exhaust valve changes to the advance side, the injection timing of the single fuel injection is changed to the advance side.

In an eighth aspect based on the sixth aspect, when the opening timing of the intake valve changes to the retard side, the injection timing of the single fuel injection is changed to the retard side.

[0015]

According to the present invention, when the catalyst is not in the activated state, the fuel is injected so that the fuel injection period extends from the exhaust stroke to the intake stroke, and a part of the fuel remains in the exhaust stroke. Alternatively, the fuel is burned in the exhaust pipe, thereby raising the exhaust temperature and activating the catalyst early, while the remaining fuel remains in the cylinder and performs normal combustion to generate the engine output. For fuel, one for normal combustion and one for catalyst temperature increase
Since the injection is performed once, the injection period is long, the fuel injection characteristics are stable, and as a result, while promptly activating the catalyst,
It can prevent deterioration of fuel consumption and exhaust composition.

Further, as in the second and third inventions, when the fuel injection amount for heating the catalyst is larger than the allowable minimum injection amount,
By switching the fuel injection to two times, it becomes possible to perform more accurate fuel injection for temperature rise and normal combustion.

In the fifth aspect of the invention, the effect of increasing the exhaust gas temperature can be enhanced by using the fuel injection for heating the catalyst as the expansion stroke.

According to the sixth to eighth aspects, when the opening / closing timings of the intake valve and the exhaust valve are variable depending on the operating conditions, the injection timing of one fuel injection is set to the opening / closing timings of these intake / exhaust valves. By correspondingly delaying or advancing it, a part of the injected fuel can always be reliably burned in the exhaust stroke or the exhaust pipe, and even in such a case, activation of the catalyst can be promoted.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a direct injection type gasoline engine, which is provided with a fuel injection valve 3 for directly injecting fuel into a combustion chamber 2. Reference numeral 4 is an intake passage, 5 is an exhaust passage, and an exhaust purification catalyst 6 is installed in the exhaust passage 5.
The catalyst 6 is a three-way catalyst that purifies NOx, CO, and HC, or NOx that absorbs NOx under a lean air-fuel ratio.
A catalyst etc. is installed.

The intake valve 7 is provided with a valve timing varying device 8 capable of variably controlling the opening / closing timing, and the exhaust valve 9 also has a valve timing varying device 10 having the same structure.
Is provided. The combustion chamber 2 is provided with an ignition plug 11 for igniting an air-fuel mixture near the compression top dead center, and further provided with an exhaust gas recirculation control valve 13 for controlling the amount of exhaust gas recirculation by the exhaust gas recirculation passage 12. A controller 15 is provided for controlling the operations of the timing varying devices 8, 10, the spark plug 11, and the exhaust gas recirculation control valve 13 and controlling the fuel injection amount from the fuel injection valve 3.

The controller 15 is composed of a microprocessor, etc., and has a throttle opening sensor 21 for detecting the opening of the throttle valve 16 in the intake passage 4 and an accelerator opening sensor for detecting the accelerator opening as signals representative of the operating state. 22, an air flow sensor 23 for detecting the engine intake air amount, a crank angle sensor 24 for detecting the engine speed, and a cooling water temperature sensor 2 for detecting the engine cooling water temperature.
5. Signals are input from the intake air temperature sensor 26 that detects the intake air temperature, the air-fuel ratio sensor 27 that detects the air-fuel ratio in the exhaust gas, the catalyst temperature sensor 28 that detects the temperature of the catalyst 6, etc. Based on this, the above control is performed according to the operating state.

Here, the fuel injection valve 3 is mainly operated when the catalyst 6 is in an inactive state, such as immediately after the engine is started.
The control performed by the controller 15 in order to raise the exhaust gas temperature and activate the catalyst 6 early by adjusting the fuel injection amount and injection timing from will be described with reference to the flowchart of FIG.

The control operation according to this flowchart is repeatedly executed every predetermined unit time.

First, in step S01, the cooling water temperature sensor 2
5. The failure diagnosis of the catalyst temperature sensor 28 and the like is performed, and when these are normal, it is determined that the catalyst activation control condition is satisfied, and the process proceeds to step S02. If not, the process proceeds to step S17, Fuel injection (control 3) is performed.
In this normal injection, the fuel injection pulse width and the injection timing are calculated from a preset map based on the engine speed and the intake air amount at that time, and the fuel injection is performed.

When the above control conditions are satisfied, the catalyst temperature detected by the catalyst temperature sensor 28 is read as TCAT in step S02.

Then, in step S03, the catalyst temperature TCAT is set to the reference temperature TCATMA corresponding to the catalyst temperature that requires early activation.
Compare with X to determine if early activation is required. This judgment reference temperature takes different values depending on the composition of the noble metal contained in the catalyst 6. If the catalyst temperature is lower than the reference temperature, the process proceeds to step S04, but if it is higher than the reference temperature, it is determined that the catalyst has been sufficiently activated, the process proceeds to step S18, and the same as in step 17, the normal fuel is used. Inject.

In step S04, as temperature increase control for activating the catalyst 6 early, the fuel injection is divided into normal fuel injection and separate temperature increase fuel injection with a delayed injection timing ( For the control 1), based on the engine speed and the intake air amount at that time, the normal fuel injection pulse width CT11 and the temperature rising fuel injection pulse width CT12, which are set for double injection, are set in advance. Calculate according to the set map.

At step S05, the minimum pulse width CTIMIN peculiar to the fuel injection valve capable of stable fuel injection is compared with the calculated pulse widths CTII and CT12, respectively, and when any of the calculated fuel injection pulse widths is small, The process proceeds to step S06, but if not, the process proceeds to step S19 to inject fuel twice based on the calculated fuel injection pulse widths CTII and CT12 (control 1).

Since both the normal fuel injection and the temperature-increasing fuel injection are performed twice with a minimum fuel injection pulse width and stable and accurate injection amount control is possible, the temperature-increasing fuel with a delayed injection timing is used. Accurately raise exhaust temperature based on injection,
The early activation of the catalyst 6 can be promoted.

On the other hand, the fuel injection pulse width CTII and
When either CTI2 is smaller than the minimum pulse width which is the limit of stable fuel injection, after step S06, the fuel for normal injection and the fuel injection for temperature increase is injected once as the catalyst early activation control. By performing the fuel injection and performing the fuel injection timing from the exhaust stroke to the intake stroke, a part of the injected fuel is burned in the exhaust stroke or the exhaust pipe to raise the exhaust temperature (control 2).

Therefore, first, the intake air amount is read in step S06, the engine speed is read in step S07, the intake valve opening timing is read in step S08, and the exhaust valve closing timing is read in step S09.

Then, in step S10, the fuel injection pulse width CT13 is calculated from the engine speed and the intake air amount according to a preset map. In step S11, a pulse width correction coefficient correlated with the catalyst temperature is set,
The correction coefficient KCT1 is calculated from the table as shown in FIG. 3 based on the catalyst temperature at that time. The correction coefficient is a value that increases as the catalyst temperature decreases.

In step S12, the injection pulse width CT13 is corrected based on this correction coefficient KCT1 to calculate the final fuel injection pulse width CT14 as CT14 = CT13 × KCT1. Therefore, the corrected injection pulse width is larger as the catalyst temperature is lower, and the effect of increasing the exhaust gas temperature is enhanced.

In step S13, the basic fuel injection timing TITM is calculated from the fuel injection timing map which is set in advance based on the engine speed and the intake air amount.

In step S14, the injection timing correction value CTITM is calculated according to the map shown in FIG. 4, in which the injection timing correction value based on the intake valve opening timing and the exhaust valve closing timing is set. The injection timing correction value CTITM is set to a value that increases as the exhaust valve closing timing and the intake valve opening timing both delay.

Then, in step S15, the fuel injection timing TITM
Is corrected by the correction value CTITM, and the final fuel injection timing TIT
Calculate M2 as TITM2 = TITM + CTITM. As shown in FIG. 5, when the opening timing of the intake valve 7 is delayed by the valve timing variable device 8, the final fuel injection timing TITM2 is relatively delayed (the crank angle is retarded). ), And as shown in FIG. 6, when the valve timing varying device 10 accelerates the closing timing of the exhaust valve 9, the injection timing TITM2 is relatively advanced (crank angle is advanced).

As described above, even when the valve timings of the intake valve 7 and the exhaust valve 9 are changed to the optimum state according to the operating state of the engine, the fuel injection timing is adjusted to follow the change, so that the fuel is always raised. Appropriate distribution for warm combustion and normal combustion.

Then, in step S16, fuel injection is executed by the fuel injection pulse width CT14 and the injection timing TITM2 thus set, and a part of the fuel injection period is always in the exhaust stroke by these, and the exhaust stroke or Part of the fuel burns in the exhaust pipe to raise the temperature of the exhaust gas, while the remaining fuel in the intake stroke remains in the combustion chamber 2 to generate engine output by normal combustion.

Here, the fuel injection control for activating the catalyst 6 will be collectively described with reference to FIG.

When the temperature of the catalyst 6 is low and the catalyst 6 is not activated, such as immediately after instruction of the engine, fuel injection for temperature increase is performed to raise the catalyst temperature.

This is achieved by dividing into two fuel injections, the normal fuel injection and the relatively small amount of fuel injection for raising the temperature by delaying the fuel injection timing. In this case, , Especially when the fuel injection pulse width for temperature rise becomes less than the allowable minimum injection pulse width required for stable fuel injection, in the region including the valve overlap period from the exhaust stroke to the intake stroke, The fuel injection is performed once for a long period.

In FIG. 7, the above-mentioned two-time injection varies depending on the operating state at that time. For example, in the case of a, the normal injection is performed in the intake stroke of the engine to realize the homogeneous mixture combustion. After that, fuel injection for temperature rise is performed at the end of the compression stroke. In the case of b, the normal injection is the same as a, but
By performing the fuel injection for raising the temperature in the expansion stroke, the effect of further raising the exhaust temperature is further enhanced. Further, in the case of c, the normal injection is performed in the compression stroke, thereby enabling stratified combustion of the lean mixture, while the fuel injection for temperature increase is performed in the expansion stroke.

Any of these is selected according to the operating state at that time, and either the compression stroke or the expansion stroke can be selected for the fuel injection for temperature rise, and the latter is the amount by which the start of fuel combustion is delayed. The effect of increasing the exhaust gas temperature, that is, the effect of increasing the catalyst temperature is high.

On the other hand, the injection pulse width for performing the fuel injection twice is smaller than the allowable minimum injection pulse width,
When stable fuel injection cannot be performed, it is switched to single injection, as indicated by d.

As shown in FIGS. 5 and 6, this one-time fuel injection is in a range including the top dead center from the exhaust stroke to the intake stroke, that is, the valve in which both the intake valve 7 and the exhaust valve 9 are open. It is set to the range including the overlap period. More specifically, fuel injection starts before the exhaust valve 9 is closed and before the intake valve 7 is opened, and fuel injection is ended after the intake valve 7 is opened and the exhaust valve 9 is closed. Most of the injected fuel in the initial stage flows to the exhaust pipe as it is and burns in the exhaust pipe. Therefore, the exhaust temperature is raised and the temperature raising effect of the catalyst 6 is enhanced. On the other hand, the remaining fuel injected during the intake stroke remains in the cylinder during the intake stroke after the exhaust valve 9 is closed, is compressed and ignited, and performs normal homogeneous mixture combustion to generate engine output.

In this case, the fuel required for both the normal combustion and the temperature-raising combustion is performed by one-time fuel injection, so that the fuel injection period is long and the injection pulse width is large. The target fuel injection amount is stable and accurately controlled. Even if the fuel injection amount for temperature increase is small, accurate fuel injection can be realized because it is injected once, and combustion for temperature increase can be reliably performed, without deteriorating fuel consumption or exhaust composition. This makes it possible to activate the catalyst 6 early.

It is obvious that the present invention is not limited to the above-mentioned embodiments and various modifications can be made within the scope of the technical idea thereof.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the control contents of the same.

FIG. 3 is a characteristic diagram of a fuel injection pulse width correction coefficient.

FIG. 4 is a characteristic diagram of a fuel injection timing correction value.

FIG. 5 is an explanatory diagram showing a relationship between an opening / closing timing of an intake / exhaust valve and a fuel injection period.

FIG. 6 is an explanatory diagram showing a relationship between an opening / closing timing of an intake / exhaust valve and a fuel injection period.

FIG. 7 is an explanatory diagram showing fuel injection characteristics.

[Explanation of symbols]

1 engine 3 Fuel injection valve 4 Intake passage 5 exhaust passage 6 catalyst 7 intake valve 8 Valve timing variable device 9 Exhaust valve 10 Valve timing variable device 15 Controller 21 Throttle opening sensor 23 Air flow sensor 24 crank angle sensor 25 Cooling water temperature sensor 27 Air-fuel ratio sensor 28 Catalyst temperature sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/34 F02D 41/34 F 43/00 301 43/00 301J 301Z F term (reference) 3G084 BA09 BA13 BA15 BA23 CA01 CA02 CA03 DA00 DA10 DA28 EB11 FA02 FA07 FA10 FA20 FA29 FA33 FA38 3G091 AA11 AA17 AA24 AB05 BA02 BA03 BA11 BA32 CB00 CB02 CB03 DC01 EA01 EA05 EA07 EA16 EA18 EA33 FA01 FA12 FA13 FB02 FB10 FC07 HA08 HA36 HA38 HB00 3G092 AA01 AA06 AA11 AA17 BA01 BB01 BB06 BB13 DA08 DE03S EA03 EA04 EA09 EC01 FA00 FA15 GA01 GA04 HA01Z HA04Z HA06Z HA13Z HD02Z HD05X HD05Z HD09Z HE01Z HE08Z HF08Z 3G301 HA04 HA13 HA19 JA00 JA21 JA25 JA26 KA01 KA02 KA05 KA08 LA03 LB04 MA01 MA11 MA19 MA23 NA08 ND01 NE11 NE12 NE15 PA01Z PA10Z PA11Z PD02A PD02Z PD12Z PE01Z PE03Z PE08Z PF03Z

Claims (8)

[Claims] 1. A direct injection engine comprising a fuel injection valve for injecting fuel into an engine and an exhaust purification catalyst installed in an exhaust system, means for determining an activation state of the catalyst, and the catalyst being inactive. A fuel injection control device for a direct injection type engine, comprising: a fuel injection control means for performing one fuel injection so that the fuel injection period extends from the exhaust stroke to the intake stroke when in the state. 2. A direct injection engine comprising a fuel injection valve for injecting fuel into the engine and an exhaust gas purification catalyst installed in an exhaust system, and means for determining an activation state of the catalyst and inactivating the catalyst. In the state, the fuel injection is performed in two times, that is, the fuel injection timing during the normal operation and the fuel injection timing that is later than this, or the fuel injection period is set once so that it extends from the exhaust stroke to the intake stroke. And a fuel injection control unit that selects and executes the fuel injection according to operating conditions. 3. The direct injection type according to claim 1, wherein the one fuel injection period starts before the intake valve opens before the exhaust valve closes and ends after the intake valve opens and the exhaust valve closes. Engine fuel injection control device. 4. The direct injection engine according to claim 2, wherein the one fuel injection is selected when the fuel injection pulse width determined by the operating conditions of the two fuel injections is smaller than the allowable minimum pulse width. Fuel injection control device. 5. The fuel injection after the two fuel injections is performed in a compression stroke or an expansion stroke.
13. A fuel injection control device for a direct injection type engine according to. 6. A valve timing varying device for changing the opening / closing timing of an intake valve and an exhaust valve of an engine, wherein the fuel injection control means is responsive to at least one of an exhaust valve closing timing and an intake valve opening timing. The fuel injection control device for a direct injection engine according to any one of claims 1 to 5, wherein the injection timing of one fuel injection is corrected. 7. The fuel injection control of a direct injection engine according to claim 6, wherein when the closing timing of the exhaust valve changes to the advance side, the injection timing of the one-time fuel injection is changed to the advance side. apparatus. 8. The fuel injection control for a direct injection engine according to claim 6, wherein when the opening timing of the intake valve changes to the retard side, the injection timing of the one-time fuel injection is changed to the retard side. apparatus.