JP2000008912A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excessive heat load from being applied to an engine when the fuel injection quantity of an auxiliary fuel injection valve is insufficient in a device provided with a main fuel injection valve for injecting fuel directly into a combustion chamber of each cylinder, and the auxiliary fuel injection valve provided upstream of a branch part of each cylinder in an intake passage. SOLUTION: When the injection quantity of an auxiliary fuel injection valve is insufficient in the 'ON' area of the auxiliary fuel injection valve (YES in S2, S3), in case of an operating area being in an NG area (high rotation and high load area) where the heat load of an engine becomes excessive due to becoming excessively lean by the insufficiency of the injection quantity (YES in S4), the fuel injection quantity QF of a main fuel injection valve is limited to the threshold value QFL so as not to enter the NG area (S5), and the fuel injection quantity of the auxiliary fuel injection valve is made zero to control fuel injection (S6, S7).

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, and injecting fuel 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. The present invention has been made in view of such a conventional problem, and in the fuel injection control device, when the injection amount of the auxiliary fuel injection valve is insufficient, an excessive heat load is not applied to the engine. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine as described above.

[0006]

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. In the apparatus provided with the switching control means for sharing the fuel injection valve and the auxiliary fuel injection valve, a diagnosis means for diagnosing whether the injection amount of the auxiliary fuel injection valve is insufficient, and a diagnosis that the auxiliary fuel injection valve is insufficient for the injection amount. And operating state limiting means for limiting the operating state so as to suppress the lean state of the air-fuel ratio due to the shortage of the injection amount.

With this configuration, when the diagnosing means diagnoses that the injection amount of the auxiliary fuel injection valve is insufficient, the operating state limiting means controls the operation so as to suppress the lean state of the air-fuel ratio due to the insufficient injection amount. Limit the state. This prevents the air-fuel ratio from becoming excessively lean due to the insufficient injection amount of the auxiliary fuel injection valve and thus giving an excessive heat load to the engine, while reducing the operating state so as to suppress the lean state of the air-fuel ratio. This can be prevented by limiting.

According to a second aspect of the present invention, the operating state limiting means avoids an NG region where an excessive heat load is applied to the engine when the auxiliary fuel injection valve is diagnosed as having an insufficient injection amount. It is characterized in that the operation area is limited. According to this configuration, when the diagnosis unit diagnoses that the injection amount of the auxiliary fuel injection valve is insufficient, the operating state restriction unit determines
The operating range is limited by, for example, regulating the maximum fuel injection amount with respect to the engine speed so as to avoid an NG region set so that the heat load on the engine becomes excessive, for example, a high rotation / high load region. I do.

Thus, the operation in the NG range is avoided, so that an excessive heat load on the engine due to an insufficient injection amount of the auxiliary fuel injection valve can be prevented.
Further, the invention according to claim 3 is characterized in that the operating state limiting means sets the share of fuel supply to the main fuel injection valve to 100% when the auxiliary fuel injection valve is diagnosed as having an insufficient injection amount. I do.

With this configuration, when the diagnosing unit diagnoses that the injection amount of the auxiliary fuel injection valve is insufficient, the operating state limiting unit sets the share of the fuel supply of the main fuel injection valve to 100%, The fuel injection amount is covered only by the fuel injection valve. As a result, the fuel injection amount can be increased to the maximum by the main fuel injection valve, so that the NG region where the heat load on the engine becomes excessive can be minimized.

Further, in the invention according to claim 4, the operating state limiting means is arranged such that, when the auxiliary fuel injection valve has an insufficient injection amount, the thermal load on the engine is excessive in an NG region, and the operation of the main fuel injection valve is limited. The fuel supply is stopped. According to this configuration, when the diagnosis unit diagnoses that the injection amount of the auxiliary fuel injection valve is insufficient, the operating state restriction unit determines
The supply of fuel to the main fuel injection valve is stopped in an NG region where the heat load on the engine is set to be excessive, for example, in a high rotation / high load region.

As a result, operation in the NG range is substantially avoided, so that an excessive heat load on the engine can be prevented. According to a fifth aspect of the present invention, in the NG region where the heat load on the engine becomes excessive when the auxiliary fuel injection valve has an insufficient injection amount, the operating state limiting means may be a throttle installed in the intake system. The opening degree of the valve is reduced.

With this configuration, when the diagnosing means diagnoses that the injection amount of the auxiliary fuel injection valve is insufficient, the operating state limiting means sets the NG range set so that the heat load on the engine becomes excessive. For example, the opening degree of the throttle valve is reduced in a high rotation / high load region. Thereby, the NG
When the engine enters the range, the intake air amount decreases due to the decrease in the throttle valve opening, and the fuel injection amount also decreases. Accordingly, the operation in the NG region is substantially avoided, and the heat load on the engine becomes excessive. Can be prevented.

According to a sixth aspect of the present invention, the operating state limiting means increases the engine rotational speed by increasing the maximum opening of a throttle valve interposed in the intake system when the auxiliary fuel injection valve has an insufficient injection amount. Is reduced in accordance with According to this configuration, when the diagnosing means diagnoses that the injection amount of the auxiliary fuel injection valve is insufficient, the operating state limiting means reduces the maximum opening of the throttle valve in accordance with the increase in the engine speed. Since the fuel injection amount in the high rotation region is limited, the shortage of the fuel injection amount by the auxiliary fuel injection valve can be avoided, and the heat load on the engine can be prevented from becoming excessive.

[0015]

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. Air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle from the intake passage (intake manifold) 3 under the control of the throttle valve 2.

An electromagnetic main fuel injection valve 4 is provided for each cylinder so as to directly inject fuel (gasoline) into the combustion chamber. An electromagnetic auxiliary fuel injection valve 5 is provided commonly to all cylinders so as to inject fuel into a collecting portion (collector) of the intake manifold 3 and distribute the fuel to each cylinder. The auxiliary fuel injection valve 5 is also called a fifth valve in the case of four cylinders.

The main fuel injection valve 4 is energized by a solenoid by an injection pulse signal output from the control unit 6 in the intake stroke or the compression stroke of each cylinder in synchronization with the engine rotation, and is opened to a predetermined high pressure. The fuel whose pressure has been adjusted is injected. The injected fuel diffuses into the combustion chamber in the case of the intake stroke injection 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, for example, every one 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 that sucks and discharges the fuel in the fuel tank 7, a low-pressure regulator 9 that regulates the discharge pressure 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 discharge pressure 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 microcomputer receives input signals from various sensors, performs arithmetic processing based on the signals, and performs processing based on the input signals. The operation of the fuel injection valve 5 and the like is controlled. Although illustration of the various sensors is omitted, 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. An 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 an intake air temperature TA, and the like are provided.

Next, the fuel injection control of each embodiment performed by the control unit 6 will be described with reference to the flowcharts of FIGS. FIG. 3 shows a fuel injection control routine according to the first embodiment, which is executed every predetermined rotation or every predetermined time. 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 condition is set to homogeneous combustion or stratified combustion, and the intake air amount QA and the engine speed NE are set.
, The required fuel injection amount QF is calculated to achieve the target air-fuel ratio (generally stoichiometric for homogeneous combustion, lean for stratified combustion).

In step 2, it is determined whether or not the operating range (ON range) of the auxiliary fuel injection valve 5 is present. Here, the ON region (operating region) of the auxiliary fuel injection valve 5 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 5, the process proceeds to step 3. In step 3, it is determined whether or not the auxiliary fuel injection valve 5, which is executed in another routine, has an insufficient injection amount. This diagnosis is performed, for example, when the value of the air-fuel ratio sensor (oxygen sensor) is lean with respect to the target air-fuel ratio during fuel injection by the auxiliary fuel injection valve 5, the auxiliary fuel injection valve 5 It can be diagnosed as insufficient.

If it is determined in step 3 that the auxiliary fuel injection valve 5 has an insufficient injection amount, the process proceeds to step 4 where NG set in correspondence with the engine speed N and the fuel injection amount QF as shown in the figure. It is determined whether it belongs to the area (high rotation / high load area). Here, the NG region is set to a region in which the air-fuel ratio becomes excessively lean due to an insufficient injection amount of the auxiliary fuel injection valve 5 and an excessive heat load is applied to the engine. As will be described later, when the injection amount of the auxiliary fuel injection valve 5 is insufficient, the share ratio of the main fuel injection valve 4 is set to 100% to secure the maximum fuel injection amount, and a region where the fuel injection amount is still insufficient is an NG region. Thereby, the NG area is set to the minimum size.

In step 4, it is determined that the image belongs to the NG area
If so, the routine proceeds to step 5, where the fuel injection amount QF is
Limit fuel on the boundary of NG range for engine speed N
Injection amount QF_LThen, the process proceeds to step 6.
Also, in step 4, it is determined that the image does not belong to the NG area.
If so, the process proceeds to step 6. In Step 6
The share ratio of the main fuel injection valve 4 is set to 100%, and the auxiliary fuel injection
By setting the sharing ratio P on the valve 5 side to 0, the main fuel injection valve
4 fuel injection amount QF1-4 = QF and auxiliary fuel injection valve 5
Set the fuel injection amount QF5 = 0 and only the main fuel injection valve 4
Inject fuel.

On the other hand, at step 2, the O
Even when it is determined that the fuel injection amount is in the FF range (non-operating range), the share rate of the main fuel injection valve 4 is 100%. And perform fuel injection. In step 7, the calculated fuel injection amount QF1-4 of the main fuel injection valve 4 is converted into an injection pulse width (injection time) in consideration of the fuel pressure (set pressure of the high-pressure regulator) 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.

On the other hand, if it is determined in step 3 that the auxiliary fuel injection valve 5 does not have an insufficient injection amount, the routine proceeds to step 8, where the share ratio between the main fuel injection valve 4 and the auxiliary fuel injection valve 5 (auxiliary fuel injection valve Side sharing ratio) P is set. This sharing ratio P
Should be variable depending on the engine load. In step 9, 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 5 according to the following equation.

The reason why QF5 = 2 × QF × P is doubled is that the auxiliary fuel injector 5 is set to inject once per rotation, that is, to inject two cylinders at a time. In step 10, the calculated fuel injection amount QF5 of the auxiliary fuel injection valve 5 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 auxiliary fuel injection valve 5 is driven by the signal of the injection pulse width, and fuel is injected into the intake manifold.

In step 11, the fuel injection amount QF1-4 of the main fuel injection valve 4 is calculated by multiplying the required fuel injection amount QF by the share ratio (1-P) of the main fuel injection valve 4 by the following equation. . QF1-4 = QF.times. (1-P) Then, the routine proceeds to step 7, where the fuel injection amount QF1-4 is converted into an injection pulse width (injection time) and set in a predetermined register. Then, the main fuel injector is driven by the signal of this injection pulse width, and fuel is injected directly into the combustion chamber.

In this way, the operating range is restricted so as not to enter the NG range, so that an excessive heat load is prevented from being applied to the engine due to excessive leaning due to insufficient injection amount of the auxiliary fuel injection valve 5. it can. Next, a fuel injection control routine according to a second embodiment will be described with reference to FIG.

In step 21, a diagnosis result of whether or not the auxiliary fuel injection valve 5, which is executed in a separate routine as described above, has an insufficient injection amount is determined. When it is determined that the injection amount is insufficient, the process proceeds to step 22, and it is determined whether or not the injection amount belongs to the NG region set as described above. If it is determined that the image does not belong to the NG area, the process proceeds to step 23 to perform the normal control (steps 1, 8 to 11, and 7 in FIG. 3). If so, the routine proceeds to step 24, where QF1-4 = 0 and the fuel supply from the main fuel injection valve 4 is stopped.

In this way, when the engine enters the NG range, the engine output is reduced due to the stoppage of the fuel supply, and the engine is deviated from the NG range. Therefore, the operation is substantially performed in a region other than the NG range. As in the embodiment, it is possible to prevent an excessive heat load from being applied to the engine. The fuel supply to the auxiliary fuel injection valve 5 may be stopped. Next, a fuel injection control routine according to a third embodiment will be described with reference to FIG. This embodiment is applied to a device having an electronically controlled throttle valve.

In step 31, a diagnosis result of whether or not the auxiliary fuel injection valve 5, which is executed in a separate routine as described above, has an insufficient injection amount is determined. Then, when it is determined that the injection amount is insufficient, the process proceeds to step 32, and it is determined whether or not it belongs to the NG region set in the same manner as described above. If it is determined that the image does not belong to the NG area, the process proceeds to step 33 to perform the normal control (steps 1 to 8 and 11 in FIG. 3), and it is determined that the image belongs to the NG area. If so, the routine proceeds to step 34, where the throttle valve is closed (closed to a predetermined opening degree or fully closed).

With this arrangement, when the engine enters the NG region, the throttle valve is closed to reduce the intake air amount and the fuel injection amount accordingly. Therefore, as in the second embodiment, the NG region is reduced. And the engine is operated substantially in a region other than the NG region, so that an excessive heat load can be prevented from being applied to the engine. Next, a fuel injection control routine according to a fourth embodiment will be described with reference to FIG. This embodiment is also applied to the one provided with the electronically controlled throttle valve.

In step 41, a diagnosis result of whether or not the auxiliary fuel injection valve 5, which is executed in a separate routine similarly to the above, has an insufficient injection amount is determined. When it is determined that the injection amount is not insufficient, the routine proceeds to step 42, where normal control (steps 1, 8 to 11, and 7 in FIG. 3) is performed. And when it is determined that the injection amount is insufficient,
Proceeding to step 43, the maximum opening degree or the target rotation opening degree TVOmax of the throttle valve is determined from the map based on the engine speed N. Here, the maximum opening or the target maximum opening TVOmax is set to decrease as the engine speed N increases.

In step 44, the target opening TVO of the normal throttle valve is set based on the engine speed N and the accelerator opening ACC. In step 45, the smaller of the maximum opening or the target maximum opening TVOmax and the target opening TVO is selected. With this configuration, the maximum opening of the throttle valve is limited in a decreasing direction in accordance with the increase in the engine rotation speed N, so that the throttle valve is operated substantially in a region other than the NG region. A large heat load can be prevented.

[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 one embodiment of the present invention.

FIG. 3 is a flowchart of a fuel injection control routine according to the first embodiment.

FIG. 4 is a flowchart of a fuel injection control routine according to a second embodiment.

FIG. 5 is a flowchart of a fuel injection control routine according to a third embodiment.

FIG. 6 is a flowchart of a fuel injection control routine according to a fourth embodiment.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 4 main fuel injection valve 5 auxiliary fuel injection valve 6 control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 43/00 301 F02D 43/00 301G 301K 45/00 312 45/00 312K F02M 63/00 F02M 63/00 P65 / 00 302 65/00 302 F term (reference) 3G066 AA02 AA05 AB02 AD09 BA00 BA16 BA69 CD26 CE22 CE29 DA02 DA04 DA09 DB09 DB13 DC01 DC04 DC05 DC09 DC14 DC24 3G084 AA04 BA05 BA09 BA13 BA15 CA04 CA09 DA27 EB08 EB11 EC02 EC03 FA10 FA13 FA18 FA29 FA33 3G301 HA04 HA16 JA00 JA01 JA32 JB09 KA09 KA25 KA26 LA01 LB04 LB07 MA01 MA12 MA19 MA23 MA24 NC02 ND01 NE06 NE15 NE17 PA01Z PA10Z PA11A PA11Z PA17Z PB03Z PD03A PE01Z PE03Z PE08Z PF03

Claims (6)

[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; Diagnosing means for diagnosing the presence or absence of an insufficient injection quantity of the auxiliary fuel injection valve; A fuel injection control device for an internal combustion engine, comprising: an operating state limiting means for limiting. 2. The operating state limiting means limits an operating range so as to avoid an NG range in which a heat load on the engine becomes excessive when the auxiliary fuel injection valve is diagnosed as having an insufficient injection amount. The fuel injection amount control device for an internal combustion engine according to claim 1, wherein 3. The operating state limiting means sets the share of fuel supply of the main fuel injection valve to 100% when the auxiliary fuel injection valve is diagnosed as having an insufficient injection quantity.
3. The fuel injection control device for an internal combustion engine according to claim 1. 4. The operating state limiting means stops the fuel supply to the main fuel injection valve in an NG region where the heat load on the engine becomes excessive when the auxiliary fuel injection valve is diagnosed as having an insufficient injection amount. The fuel injection control device for an internal combustion engine according to claim 1, wherein: 5. The engine according to claim 1, wherein the operating state limiting means includes a throttle valve provided in the intake system in an NG range where the thermal load on the engine becomes excessive when the auxiliary fuel injection valve is diagnosed as having an insufficient injection amount. The fuel injection control device for an internal combustion engine according to claim 1, wherein the opening degree is reduced. 6. The operating state limiting means decreases the maximum opening of a throttle valve interposed in an intake system in accordance with an increase in engine speed when the auxiliary fuel injection valve is diagnosed as having an insufficient injection amount. The fuel injection control device for an internal combustion engine according to claim 1, wherein: