JP2000274296A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

[PROBLEMS] To provide auxiliary fuel injection in a fuel injection valve having a main fuel injection valve directly injecting fuel into a combustion chamber of each cylinder and an auxiliary fuel injection valve upstream of a branch portion of each cylinder in an intake passage. Diagnose insufficient valve injection. When the operating range of an auxiliary fuel injection valve is (S)
11) The output of the oxygen sensor is read (S12), and rich / lean determination is performed (S13) When rich is determined, the auxiliary fuel injection valve is normal (S14). When lean is determined, It is diagnosed that the auxiliary fuel injection valve is abnormal (insufficient injection amount) (S15).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection spark ignition type internal combustion engine having a main fuel injection valve for directly injecting fuel into a combustion chamber, wherein fuel is injected into an intake passage separately from the main fuel injection valve. A fuel injection control device for providing a possible auxiliary fuel injection valve, operating the auxiliary fuel injection valve under predetermined operating conditions, and sharing fuel supply to the engine between the main fuel injection valve and the auxiliary fuel injection valve .

[0002]

2. Description of the Related Art In recent years, a direct injection spark ignition type internal combustion engine has attracted attention. In this type, a combustion system is switched according to engine operating conditions, that is, by injecting fuel in an intake stroke. Homogeneous combustion, in which fuel is diffused into the combustion chamber to form a homogeneous mixture, and stratified combustion, in which fuel is injected in the compression stroke to form a layered mixture intensively around the spark plug, (See JP-A-59-37236).

[0003]

In such a direct injection spark ignition type internal combustion engine, an auxiliary fuel capable of injecting fuel into an intake passage is provided separately from a main fuel injection valve which injects fuel directly into a combustion chamber. It is conceivable that an injection valve is provided and the auxiliary fuel injection valve is operated under predetermined operating conditions (at least during homogeneous combustion) so that fuel supply to the engine is shared between the main fuel injection valve and the auxiliary fuel injection valve. I have.

[0004] This aims at the following effects. (1) Elimination of the region of insufficient fuel injection represented by high rotation and high load (2) Improvement of combustion by homogeneous intake (in the high rotation and high load region, the time from in-cylinder injection to ignition (evaporation time) (3) Improve the volumetric efficiency by cooling the intake air (takes latent heat of vaporization in the intake passage because the fuel is shortened, so that the fuel homogenized (homogenized mixture and vaporized) in the intake passage is supplied in advance to homogenize the cylinder) , Improve inhalation efficiency).

By the way, in the fuel injection control device having the main fuel injection valve and the auxiliary fuel injection valve as described above, the injection amount of the auxiliary fuel injection valve in a high rotation and high load region where fuel is injected also from the auxiliary fuel injection valve. Is insufficient (including the injection amount 0), there is a possibility that the air-fuel ratio becomes excessively lean and an excessive heat load is applied to the engine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to diagnose an abnormality of an insufficient injection amount of an auxiliary fuel injection valve.

[0007]

Accordingly, the invention according to claim 1 is a direct injection spark ignition type internal combustion engine having a main fuel injection valve for directly injecting fuel into a combustion chamber as shown in FIG. In addition to the main fuel injection valve, an auxiliary fuel injection valve capable of injecting fuel is provided in the intake passage, and the auxiliary fuel injection valve is operated under predetermined operating conditions to supply fuel to the engine mainly. An air-fuel ratio detecting means for detecting an air-fuel ratio under the predetermined operating condition; and an air-fuel ratio detecting means detecting an air-fuel ratio under the predetermined operating condition. An auxiliary fuel injection valve diagnosing means for diagnosing the abnormality of the auxiliary fuel injection valve based on the abnormality is provided.

According to the first aspect of the present invention, when the auxiliary fuel injector runs short of fuel injection amount under the predetermined operating condition, the air-fuel ratio changes to the lean side with respect to the set air-fuel ratio. By detecting this by the air-fuel ratio detecting means, the auxiliary fuel injector diagnosing means can diagnose that the auxiliary fuel injector has an abnormality.

Further, the invention according to claim 2 is characterized in that the air-fuel ratio when fuel is injected only from the main fuel injection valve under the predetermined operating condition is leaner than the stoichiometric air-fuel ratio, and the main fuel injection valve and the auxiliary fuel injection valve are The share ratio of the fuel injection amount from each fuel injection valve is set so that the air-fuel ratio when fuel is normally injected from the stoichiometric air-fuel ratio is set. When the air-fuel ratio is detected to be lean, it is diagnosed that the auxiliary fuel injection valve is abnormal.

According to the second aspect of the present invention, by setting the share ratio of the fuel injection amount between the main fuel injection valve and the auxiliary fuel injection valve as described above, the air-fuel ratio becomes normal when the auxiliary fuel injection valve is normal. Since the air-fuel ratio becomes lean when the fuel injection amount is rich or insufficient, it is possible to easily diagnose the abnormality of the auxiliary fuel injection valve.

Further, the invention according to claim 3 is characterized in that the air-fuel ratio detecting means is an oxygen sensor for determining whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.

As described above, when diagnosing the presence or absence of an abnormality in the auxiliary fuel injection valve based on the rich / lean air-fuel ratio, an inexpensive air-fuel ratio detecting means for determining whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio. An oxygen sensor can be used.

[0013]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of an internal combustion engine showing one embodiment. First, this will be described.

Under the control of the throttle valve 2, air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle from an intake passage (intake manifold) 3. An electromagnetic main fuel injection valve 4 is provided for each cylinder so as to directly inject fuel (gasoline) into the combustion chamber.

The intake manifold 3 is common to all cylinders.
An electromagnetic auxiliary fuel injection valve 5 is provided so as to inject fuel into the collecting portion (collector) and distribute the fuel to each cylinder. The auxiliary fuel injection valve 5 has a fifth cylinder in the case of a four-cylinder engine.
Also called a valve.

The main fuel injection valve 4 is energized by a solenoid in response to an injection pulse signal output in the intake stroke or the compression stroke of each cylinder from the control unit 6 in synchronization with the engine rotation, and is opened to a predetermined high pressure. The fuel whose pressure has been adjusted is injected. In the case of the intake stroke injection, the injected fuel diffuses into the combustion chamber to form a homogeneous mixture, and in the case of the compression stroke injection, forms a layered mixture intensively around the spark plug, It is ignited by the spark plug and burns (homogeneous combustion or stratified combustion).

The auxiliary fuel injection valve 5 is controlled by the control unit 6 in synchronism with the engine rotation in a specific region during homogeneous combustion, or during homogeneous combustion in synchronization with switching between stratified combustion and homogeneous combustion. The solenoid is energized by the output injection pulse signal to open the valve and to inject fuel adjusted to a predetermined low pressure. The injected fuel is homogenized to some extent in the intake manifold 3 and distributed to each cylinder.

The main fuel injection valve 4 and the auxiliary fuel injection valve 5
A low-pressure fuel pump 8 for sucking and discharging the fuel in the fuel tank 7, a low-pressure regulator 9 for regulating the pressure on the discharge side of the low-pressure fuel pump 8, and further pressurizes the fuel from the low-pressure fuel pump 8. A high-pressure fuel pump 10 and a high-pressure regulator 11 for regulating the pressure on the discharge side of the high-pressure fuel pump
And supplies the high-pressure fuel regulated by the high-pressure regulator 11 to the main fuel injection valve 4 through the fuel gallery 12, and supplies the low-pressure fuel regulated by the low-pressure regulator 9 to the auxiliary fuel injection valve 5. Supply.

The control unit 6 includes a CPU, an RO,
A microcomputer including an M, a RAM, an A / D converter, an input / output interface, and the like is provided. The operation of the fuel injection valve 5 and the like is controlled.

In the exhaust passage of the engine 1, an oxygen sensor 13 is mounted as air-fuel ratio detecting means for detecting whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio. Although other sensors are not shown, the crankshaft or camshaft rotation of the engine 1 is detected, whereby a crank angle sensor capable of detecting the engine speed NE, and the intake air amount QA upstream of the throttle valve 2 are detected. Air flow meter, a throttle sensor for detecting the opening TVO of the throttle valve 2,
A water temperature sensor for detecting a cooling water temperature TW of the engine 1;
An intake air temperature sensor for detecting A is provided.

Next, the fuel injection control performed by the control unit 6 will be described with reference to the flowcharts of FIGS. FIG. 3 shows a fuel injection control routine which is executed at every predetermined rotation or every predetermined time. This routine corresponds to the switching control means.

In step 1 (referred to as S1 in the figure, the same applies hereinafter), a fuel injection amount QF per cylinder (one combustion) required by the engine is calculated based on the engine operating conditions.
Specifically, the engine operation conditions are set to homogeneous combustion or stratified combustion, and the target air-fuel ratio (generally stoichiometric for homogeneous combustion, lean for stratified combustion) based on the intake air amount QA and the engine speed NE. Required fuel injection amount Q such that
Calculate F.

In step 2, it is determined whether or not it is within the operating range (ON range) of the auxiliary fuel injection valve. Here, the ON region of the auxiliary fuel injection valve is defined as a specific region (high rotation / high load region) during homogeneous combustion.

If it is in the ON range of the auxiliary fuel injection valve, the routine proceeds to step 3. In step 3, the sharing ratio P between the main fuel injection valve and the auxiliary fuel injection valve (the sharing ratio on the auxiliary fuel injection valve side) is set. This sharing ratio P may be variable depending on the engine load. However, when the auxiliary fuel injection valve does not operate and fuel is injected only from the main fuel injection valve, the air-fuel ratio becomes lean, and the auxiliary fuel injection valve operates normally. The air-fuel ratio is set to be rich when fuel is normally injected from the main fuel injection valve and the auxiliary fuel injection valve.

In step 4, the required fuel injection amount QF is multiplied by the sharing ratio P to calculate the fuel injection amount QF5 of the auxiliary fuel injection valve according to the following equation. QF5 = 2 * QF * P is doubled because the auxiliary fuel injection valve is set to inject once per revolution, that is, to inject two cylinders at a time.

In step 5, the calculated fuel injection amount QF5 of the auxiliary fuel injection valve is converted into an injection pulse width (injection time) in consideration of the fuel pressure (set pressure of the low pressure regulator) and set in a predetermined register. . Thus, at a predetermined injection timing, the signal of this injection pulse width drives the auxiliary fuel injection valve, and fuel is injected into the intake manifold.

In step 6, the required fuel injection amount QF is multiplied by the share ratio (1-P) of the main fuel injection valve by the following equation to calculate the fuel injection amount QF1-4 of the main fuel injection valve. QF1-4 = QF × (1-P) Then, the process proceeds to step 7.

In step 7, the calculated fuel injection amount QF1-4 of the main fuel injection valve is converted into an injection pulse width (injection time) in consideration of the fuel pressure (set pressure of the high-pressure regulator) and stored in a predetermined register. set. Accordingly, at a predetermined injection timing, the main fuel injection valve is driven by the signal of this injection pulse width, and fuel is injected directly into the combustion chamber.

If the auxiliary fuel injection valve is in the OFF range, the routine proceeds to step 8. In this case, fuel injection is performed only by the main fuel injection valve. QF1-4 = QF, QF5 = 0 Then, the process proceeds to step 7.

In step 7, as described above, the calculated fuel injection amount QF1-4 of the main fuel injection valve is converted into an injection pulse width in consideration of the fuel pressure and set in a predetermined register. Accordingly, at a predetermined injection timing, the main fuel injection valve is driven by the signal of this injection pulse width, and fuel is injected directly into the combustion chamber.

Next, a routine for diagnosing the abnormality (insufficient injection amount) of the auxiliary fuel injection valve according to the present invention will be described. This routine corresponds to auxiliary fuel injection valve diagnosis means. In step 11, the operating range of the auxiliary fuel injection valve (ON
Area).

If it is determined that it is in the operating range, step 12
Then, the output of the oxygen sensor 13 is read. In step 13, it is determined based on the output of the oxygen sensor 13 whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.

When it is determined that the air-fuel ratio is rich, the routine proceeds to step 14, where the auxiliary fuel injection valve is diagnosed as normal, but when it is determined that the air-fuel ratio is lean, step 1 is performed.
Proceed to 5 and diagnose that the auxiliary fuel injection valve is abnormal (insufficient injection amount).

In this way, in the operating range of the auxiliary fuel injection valve, it is possible to easily diagnose whether or not the auxiliary fuel injection valve is abnormal based on the output of the oxygen sensor. Safe processing (for example, performing fuel injection only with the main fuel injection valve) can be performed.

The diagnosis may be made when the vehicle enters the operating range of the auxiliary fuel injection valve without setting any special diagnosis conditions.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.

FIG. 3 is a flowchart of a fuel injection control routine.

FIG. 4 is a flowchart of an auxiliary fuel injection valve diagnosis routine;

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 2 throttle valve 3 intake manifold 4 main fuel injection valve 5 auxiliary fuel injection valve 6 control unit 13 oxygen sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/04 330 F02D 41/04 330D 340 340 41/34 41/34 C 45/00 364 45/00 364Q F term (reference) 3G084 BA13 BA15 CA04 CA09 DA27 EA11 EB12 EB22 FA29 3G301 HA01 HA04 HA16 JA29 JA32 JB00 JB02 KA09 KA25 LB03 LB04 LB05 LB06 LB07 LB13 MA01 MA12 NB14 ND01 NE13 NE15 PA01Z PA10Z PA03 PZZZ10

Claims (3)

[Claims] 1. A direct injection spark ignition type internal combustion engine having a main fuel injection valve for directly injecting fuel into a combustion chamber, wherein an auxiliary fuel capable of injecting fuel into an intake passage separately from the main fuel injection valve. A fuel injection valve provided with switching control means for operating the auxiliary fuel injection valve under predetermined operating conditions to share fuel supply to the engine with the main fuel injection valve and the auxiliary fuel injection valve; Air-fuel ratio detection means for detecting an air-fuel ratio under a predetermined operating condition; and auxiliary fuel injection valve diagnosing means for diagnosing an abnormality of the auxiliary fuel injection valve based on the air-fuel ratio detected under the predetermined operation condition. A fuel injection control device for an internal combustion engine, comprising: 2. The air-fuel ratio when the fuel is injected only from the main fuel injection valve under the predetermined operating conditions is lean, and the air-fuel ratio when the fuel is normally injected from the main fuel injection valve and the auxiliary fuel injection valve is The share ratio of the fuel injection amount from each fuel injection valve is set so as to be rich, and the auxiliary fuel injection valve diagnosis means sets the auxiliary fuel injection valve when the air-fuel ratio is detected as lean under the predetermined operating conditions. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection control device diagnoses the fuel injection as abnormal. 3. The fuel injection control device for an internal combustion engine according to claim 2, wherein said air-fuel ratio detecting means is an oxygen sensor for determining whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.