JPH1182138A - Fuel injection control device for direct injection type spark-ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately set timing of compression stroke injection for stratified combustion at the time of switching from stratified combustion to uniform combustion. SOLUTION: According to changeover-setting to stratified combustion or uniform combustion, one of a stratified injection quantity CTIS and uniform injection quantity CTIH is computed every specified operation cycle, and a stratified injection quantity TISETSn and an uniform injection quantity TISETHn (n is the number of cylinder) of each cylinder are updated and set on the basis of the injection quantities CTIS, CTIH. As to the cylinder (illustrated #.1 cylinder) that cannot be immediately shifted to an intake stroke at the time of switching from stratified combustion to uniform combustion, updating of the stratified injection quantity TISETSn is inhibited to execute compression stroke injection. The stratified injection quantity TISETn of the next injection cylinder is used ad the injection quantity used at the time of determining compression stroke injection timing. Accordingly even after the shift to uniform combustion where the stratified injection quantity CTIS is computed to zero, compression stroke injection can be executed at appropriate timing.

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 spark ignition engine, and more particularly to a technique for setting an injection timing for stratified combustion in a direct injection spark ignition engine that can be switched between homogeneous combustion and stratified combustion. About.

[0002]

2. Description of the Related Art Conventionally, a fuel injection valve for directly injecting fuel into a combustion chamber of an engine is provided. When the engine is under a low load, the fuel is dispersed in a later stage of the compression stroke in order to suppress the dispersion of the fuel and supply the fuel near the spark plug. A direct-injection spark ignition engine that injects fuel and performs homogeneous combustion in the early stage of an intake stroke in order to actively disperse the fuel at a high load while injecting fuel into stratified combustion is known ( JP-A-60-30420
Reference).

[0003]

By the way, in an internal combustion engine having a fuel injection valve in an intake port portion and performing only homogeneous combustion, the latest value of the fuel injection amount calculated every predetermined time (for example, 10 ms) is used. The injection timing is referred to at the time of setting the injection timing, and the injection timing is determined as the crank angle until the start of the injection based on the latest value.

However, in the direct injection type spark ignition engine, when one of the injection amount CTIS for stratified charge combustion and the injection amount CTIH for homogeneous charge combustion is calculated at predetermined time intervals, the stratified charge is homogeneous. At the time of switching to, there is a case where it is necessary to cause the compression stroke injection to be performed before the transition to the homogenization, even though the calculation of the injection amount has been switched to the homogenization. In this case, at the time of determining the injection timing of the compression stroke injection, since the calculation of the injection amount has already been switched from stratified to homogeneous, the injection amount CTI for stratified combustion corresponds to the compression stroke injection.
If the injection timing is determined based on S, C
Injection timing may be set based on TIS = 0, and injection may not be performed.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to always appropriately set the injection timing of the compression stroke injection in a direct injection spark ignition engine that can be switched between homogeneous combustion and stratified combustion. Aim.

[0006]

According to the present invention, a fuel injection valve for directly injecting fuel into a cylinder is provided, while stratified combustion by injection in a compression stroke and homogeneous injection by injection in an intake stroke. In a fuel injection control device for a direct injection spark ignition engine in which the combustion method is switched to either combustion, the fuel injection amount corresponding to the combustion method is set for each cylinder, while the injection timing during stratified combustion is set to the next injection cylinder. Is determined based on the fuel injection amount for stratified combustion set in accordance with the above.

According to this configuration, especially when switching the combustion system, it is necessary to determine the combustion system of each cylinder independently of the request of the combustion system. Therefore, each cylinder corresponds to the combustion system for each cylinder. The fuel injection amount is set separately. Then, the injection timing for stratified combustion is determined based on the fuel injection amount for stratified combustion set in correspondence with the next injection cylinder.

According to the second aspect of the present invention, while the fuel injection valve for directly injecting fuel into the cylinder is provided, combustion is performed in either stratified combustion by injection in the compression stroke or homogeneous combustion by injection in the intake stroke. In the fuel injection control device of the direct injection type spark ignition engine in which the system is switched, while setting the fuel injection amount corresponding to the combustion system for each cylinder, the injection timing at the time of stratified combustion, the injection timing for each cylinder at the time of stratified combustion The configuration is determined based on the maximum value of the fuel injection amount.

With this configuration, the injection amount for stratified combustion is 0 for a cylinder in which stratified combustion is not performed.
At the time of switching from stratified to homogeneous, the injection amount for stratified combustion in a cylinder in which stratified combustion is continuously performed without being in time for the switching request will be set to a value appropriate for the operating conditions. The injection amount of the cylinder in which stratified combustion is performed is selected, and the injection timing is determined.

According to the third aspect of the present invention, the fuel injection valve for directly injecting fuel into the cylinder is provided, and the fuel is combusted into either stratified combustion by injection in the compression stroke or homogeneous combustion by injection in the intake stroke. In a fuel injection control device for a direct injection spark ignition engine in which a system is switched, a fuel injection amount corresponding to a combustion system is calculated at a predetermined calculation cycle, and a combustion system corresponding to each cylinder is determined based on the fuel injection amount. While setting the fuel injection amount, the injection timing at the time of stratified combustion, the fuel injection amount for the stratified combustion set corresponding to the next injection cylinder, and the fuel injection amount for the stratified combustion calculated for each predetermined calculation cycle. The fuel injection amount is determined based on the larger one of the latest values.

According to this configuration, for example, when a request for switching from stratified combustion to homogeneous combustion is generated, 0 is set as the fuel injection amount for stratified combustion calculated every predetermined calculation cycle. In this case, the fuel injection amount for stratification in the cylinder that continues stratified combustion without being able to respond to the switching request becomes larger, and the injection timing is set based on the injection amount for stratification in the cylinder. Will be.

According to the present invention, the injection timing is set as an angle from a reference angle signal output early in the compression stroke to an injection start timing. According to this configuration, a reference angle signal is output at the beginning of the compression stroke (for example, BTDC 110 °) at which the cylinder intake air amount is determined, and the angle from this reference angle signal to the injection start timing is set as the injection timing.

[0013]

According to the first aspect of the present invention, since the injection timing at the time of stratified combustion is determined based on the fuel injection amount set corresponding to the combustion system in each cylinder, the stratified combustion is homogeneous. Even when only the injection amount for homogeneous combustion is calculated as the latest fuel injection amount in response to a request to switch to combustion, the effect that an appropriate injection timing corresponding to stratified combustion can be set can be obtained. is there.

According to the second aspect of the present invention, the injection timing for stratified combustion is set based on the maximum injection amount among the injection amounts for stratified combustion. When the switching request is made, the injection amount of the cylinder in which the stratified combustion is continuously performed without switching in time is selected, and the injection timing for the stratified combustion can be appropriately set without the need to determine the cylinder. This has the effect.

According to the third aspect of the present invention, the stratified combustion injection amount set corresponding to the next injection cylinder and the stratified combustion fuel injection amount calculated every predetermined calculation cycle are calculated. Since the injection timing for stratification is set based on the larger one, even when 0 is set as the latest injection amount for stratification combustion in response to a request for switching from stratification to homogeneous combustion. In addition, there is an effect that an appropriate injection timing corresponding to stratified combustion can be set.

According to the present invention, the injection timing for stratified charge combustion is determined based on the initial stage of the compression stroke, and the injection timing is determined from the injection amount at the timing when the cylinder intake air amount is determined. There is an effect that it becomes possible.

[0017]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a system configuration of an internal combustion engine according to an embodiment.
Is filtered by the throttle valve 3 and is sucked into the cylinder via the intake valve 4.

Each cylinder of the engine 1 is provided with an electromagnetic fuel injection valve 5 for injecting fuel (gasoline) directly into the combustion chamber, and the fuel injected from the fuel injection valve 5 is mixed into the cylinder. Qi is formed. The air-fuel mixture in the cylinder is ignited and burned by spark ignition by the spark plug 6,
The combustion exhaust is discharged through an exhaust valve 7, purified by a catalyst 8, and released to the atmosphere.

The engine 1 according to the present embodiment constitutes a direct-injection spark ignition engine with the above configuration. A control unit 10 containing a microcomputer controls fuel injection by the fuel injection valve 5 and ignition by a spark plug 6 (energization to an ignition coil (not shown)) by arithmetic processing based on detection signals from various sensors.

The various sensors include an intake air flow rate Q
Air flow meter 11, a position sensor 12 for outputting a position signal POS for each 1 ° CA, BTDC
A reference sensor 13 that outputs a reference signal (reference angle signal) REF every 110 °, an air-fuel ratio sensor 15 that detects the air-fuel ratio of the combustion mixture, and an opening degree T of the throttle valve 3.
A throttle sensor 16 for detecting VO, a water temperature sensor 17 for detecting a cooling water temperature Tw, and the like are provided.

The control unit 10 includes a plurality of target equivalence ratio maps in which a target equivalence ratio and a combustion method are set in advance according to operating conditions such as target engine output torque and engine speed. The map is switched and referred to according to conditions such as water temperature, time after starting, vehicle speed, acceleration, and the like, and a target equivalent ratio and a request for a combustion method are determined. Further, a first order delay is given to the target equivalence ratio obtained from the target equivalence ratio map to obtain a target equivalence ratio TFBYA used for the actual fuel injection amount calculation, and the target equivalence ratio TFBYA is a threshold value for determining the switching of the combustion method. When the vehicle crosses, the combustion system is switched (see FIG. 2).
reference).

The combustion system includes a homogeneous combustion system in which fuel is diffused by injecting fuel during an intake stroke to form a homogeneous mixture in a cylinder and perform homogeneous combustion, and an injection system during a compression stroke. Is performed, a stratified supply is performed to form a rich air-fuel mixture around the ignition plug 6, and the stratified combustion method for performing the stratified combustion is switched and set.

In the example shown in FIG. 2, when it is determined to switch from stratified combustion to homogeneous combustion based on a comparison between the target equivalent ratio TFBYA to which the first-order delay is given and the threshold value (point A in FIG. 2). Since the intake stroke injection timing for the homogeneous combustion in the # 1 cylinder has already passed, the stratified combustion is performed by the compression stroke injection for the # 1 cylinder even after the switch to the homogeneous combustion. I have.

Here, based on the determination of switching between stratified combustion and homogeneous combustion based on a comparison between the target equivalent ratio TFBYA to which the first-order lag is given and the threshold, during stratified combustion, the fuel injection amount CTIS for stratified combustion is determined. Is a predetermined calculation cycle (for example, 10
ms), and at the time of homogeneous combustion, the fuel injection amount CTIH for the homogeneous combustion is calculated at the predetermined calculation cycle (for example, 10 ms), and at the time of the homogeneous combustion, the fuel for the stratified combustion is calculated. The injection amount CTIS is set as 0,
During stratified charge combustion, the fuel injection amount CTIH for homogeneous charge combustion
Is set as 0.

The stratified injection amount TISE for each cylinder
TSn and the homogenizing injection amount TISETHn (n indicates a cylinder number) are updated and set every 10 ms based on the fuel injection amounts CTIS and CTIH. Basically, TISETSn = CTIS, TISETH = C
TIH, and if CTIS = 0, the stratification injection amount TI
SETSn = 0 is set, and if CTIH = 0, the homogeneous injection amount TISETHn = 0 is set.

However, at the time point when it is determined to switch from stratified combustion to homogeneous combustion based on a comparison between the target equivalence ratio TFBYA to which the first-order delay is given and the threshold value, either of the intake stroke injection or the compression stroke injection is determined. The compression stroke pulse change permission flag is set to OFF for a cylinder in which no compression is performed (# 1 cylinder shown in FIG. 2) from the time of the switching determination to the ignition timing of the cylinder. Updating (zero reset) of the stratification injection amount TISETSn is prohibited.

As a result, even if a determination is made to switch from stratified to homogeneous and the stratified injection amount CTIS is calculated as 0, the stratified injection amount TISETSn is maintained for the cylinder in which stratified combustion is continued. Is held at the value immediately before switching. The stratified injection amount TISETSn for a cylinder that can immediately transition to homogeneous combustion from the determination to switch to homogeneous is included in the latest stratified injection amount CTI.
When S is set, TISETSn = 0.

By inhibiting the stratification injection amount TISETSn from being updated at the time of switching as described above, the # 1 of FIG.
In a cylinder such as a cylinder that cannot immediately shift to homogeneous combustion in response to the switching determination, it is possible to perform the compression stroke injection based on the stratification injection amount TISETSn held at the value immediately before the switching determination. . In the compression stroke injection based on the stratification injection amount TISETSn, the crank angle up to the injection start timing is measured based on a reference signal REF output immediately before ignition, and the stratification injection amount is measured at the injection start timing. This is performed by outputting an injection pulse signal having a pulse width corresponding to TISETSn to the fuel injection valve 5, and the reference signal R
The injection timing given as the crank angle from the EF is set as shown in the flowchart of FIG.

The routine shown in the flowchart of FIG.
Interruption is executed when the reference signal REF for each BTDC 110 ° is output. First, in step 1 (in the figure, denoted by S1; the same applies hereinafter), the current reference signal REF is output. The stratification injection amount TISETSn, which is set corresponding to the cylinder that will be subjected to the compression stroke injection later, is read.

In step 2, the reference signal R
The engine rotation speed Ne obtained by measuring the generation cycle of the EF or the number of occurrences of the position signal POS within a predetermined time is read. In step 3, a stratified injection amount TISETSn read in step 1 and a stratified injection amount TISETSn read in step 1 are referred to with reference to a map in which the injection timing ANGTMS during the compression stroke during stratified combustion is previously set using the injection amount and the engine speed as parameters. An injection timing ANGTMS corresponding to the read engine speed Ne is searched.

The injection timing ANGTMS is set as a crank angle from the reference signal REF to the start of injection. In step 4, the injection timing ANGTMS is set in a timer. The timer is
The stratification injection amount is configured to be counted down every time the position signal POS is generated. When the timer counts down to 0, that is, when the position is rotated by the injection timing ANGTMS from the reference signal REF, the stratification injection amount is set. An injection pulse signal having a pulse width corresponding to TISETSn is output to the fuel injection valve 5 of the corresponding cylinder to execute the compression stroke injection. If TISETSn = 0 even at the injection timing for stratification, no injection is performed.

In a continuous stratified combustion state, TISE
Since TSn = CTIS, the injection timing AN
The injection amount TISETSn used for GTMS is the same data as the latest stratification injection amount CTIS. The latest stratification injection amount CTIS is a value calculated based on operating conditions at BTDC 110 ° (initial stage of the compression stroke) at which the reference signal REF is output, and the cylinder intake air amount is determined based on the fact that the intake valve is closed. , The reference signal REF substantially corresponding to the closing timing of the intake valve.
If the injection timing is determined based on the latest stratified injection amount CTIS at the time of the output, the injection timing will be set accurately in accordance with the demands of the engine.

On the other hand, as shown in FIG. 2, at the time of switching from stratification to homogeneous combustion, the injection timing of the cylinder (cylinder # 1 in FIG. 2) for which the intake stroke injection has not been made in response to the switching determination is determined. In this case, if the injection timing is determined based on the latest stratified injection amount CTIS, CTIS = 0 and the injection timing will not be set. Corresponding stratification injection quantity TISETS
Since the value of n before the switching to the homogeneous state is held by the action of the compression stroke pulse change permission flag, the injection timing corresponding to the actual injection amount can be set based on the injection amount TISETSn for stratification. (See FIG. 2).

The flowchart of FIG. 4 shows a second embodiment of the setting of the stratification injection timing, which is executed when the reference signal REF is output, similarly to the above. In step 11, the stratified injection amount TI of each cylinder set at the time when the reference signal REF is output.
Find the maximum value of SETSn.

In step 12, the engine speed Ne is read. In step 13, the injection timing map is referred to based on the maximum value of the stratification injection amount TISETSn obtained in step 11 and the engine speed Ne read in step 12, and the stratification injection timing ANGTMS is performed.
Search for. In step 14, the retrieved injection timing ANGTMS is set in a timer, and after the current reference signal REF, the compression stroke injection is performed for the cylinders that are in the latter half of the compression stroke.

As described above, the injection timing for stratification is
If the stratified injection amount TISETSn for each cylinder is set based on the maximum value, all TISETs can be set.
During continuous stratified combustion in which the latest CTIS is set to Sn, the injection timing is determined based on the latest stratified injection amount TISETSn (that is, the injection amount at the time when the intake valve is closed and the cylinder intake air amount is determined). Will be set.

After the switch from stratified to homogeneous is determined, the TISETSn of the cylinder in which stratified combustion is to be continuously performed.
Only the cylinders in which only CTIS is held at the CTIS immediately before switching and the transition to homogeneous combustion immediately after the other switching determination is made, the latest CTIS = 0 will be set to TISETSn. Therefore, in this case, the maximum value of the stratified injection amount TISETSn for each cylinder is TISETSn of the cylinder in which stratified combustion is subsequently performed, and the injection timing is determined based on TISETSn of the cylinder in which stratified combustion is subsequently performed. Will be set.

In the above configuration, the injection amount used to determine the injection timing is consequently the same as in the case of the first embodiment shown in FIG. 3, but according to the second embodiment, It is not necessary to determine the cylinder of the injection amount used for setting the timing, and the calculation process is simplified. However, the condition is that a plurality of compression injection timings corresponding to a plurality of cylinders are not set based on the same reference signal REF.

The flowchart of FIG. 5 shows a third embodiment of the setting of the stratification injection timing, which is executed when the reference signal REF is output in the same manner as described above. First, at step 21, the larger of the stratification injection amount TISETSn and the latest stratification injection amount CTIS selected corresponding to the cylinder in which the compression stroke injection is performed after the current reference signal REF is selected. I do.

In step 22, the engine speed Ne is read. In step 23, a stratified injection timing ANGTMS is searched by referring to an injection timing map based on the injection amount obtained in step 11 and the engine speed Ne read in step 22. In step 24, the retrieved injection timing ANGTMS is set in a timer, and after the current reference signal REF, the compression stroke injection is performed for the cylinders that are in the latter half of the compression stroke.

According to the above configuration, during continuous stratified combustion, since TISETSn = CTIS, the injection timing can be determined based on the latest stratified injection amount at the time when the cylinder intake air amount is determined, while the stratified state is changed to homogeneous. In a cylinder that needs to continuously perform stratified combustion even after the switching of the above, the injection timing can be set based on TISETSn of the cylinder even when CTIS = 0.

The injection timing ANGTMH in the intake stroke injection (homogenous combustion) is based on the latest injection amount CTIS,
What is necessary is just to set it as the structure made to set based on the larger one of CTIH. In this case, during homogeneous combustion, CTIS = 0
Therefore, CTIH> CTIS and the injection timing A based on the latest homogenization injection amount CTIH.
NGTMH will be determined.

On the other hand, the injection timings ANGTMH, AN
If the configuration is such that the injection timings of each GTMS are simultaneously executed, the stratified combustion requires CT
Since IS> CTIH, the homogeneous injection timing ANGTMH is determined based on the stratified injection amount CTIS, and the intake stroke injection timing corresponding to the homogeneous combustion although the injection is not actually performed. Will be measured.

In the stratified combustion state, the injection timing AN
After the GTMH is determined based on the stratification injection amount CTIS, when switching from stratification to homogeneous combustion is performed, CTIS ≒ CTIH holds. This is the same as the setting based on CTIH, and the intake stroke injection can be performed at an appropriate timing immediately after switching from stratification to homogeneous.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an internal combustion engine according to an embodiment.

FIG. 2 is a time chart showing characteristics of injection control in the embodiment.

FIG. 3 is a flowchart showing a state of an injection timing calculation in the first embodiment.

FIG. 4 is a flowchart showing an injection timing calculation according to the second embodiment;

FIG. 5 is a flowchart showing an injection timing calculation in the third embodiment.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 3 throttle valve 4 intake valve 5 fuel injection valve 6 spark plug 7 exhaust valve 10 control unit 11 air flow meter 12 position sensor 13 reference sensor

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/34 F02D 41/34 E (72) Inventor Taku Oba 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Nissan Motor Co., Ltd.

Claims (4)

[Claims] 1. A direct injection type fuel injection valve for directly injecting fuel into a cylinder, wherein the combustion system is switched between stratified combustion by injection in a compression stroke and homogeneous combustion by injection in an intake stroke. In the fuel injection control device of the spark ignition engine, the fuel injection amount corresponding to the combustion method is set for each cylinder, and the injection timing at the time of stratified combustion is set to the fuel injection for stratified combustion set for the next injection cylinder. A fuel injection control device for a direct-injection spark ignition engine, which is determined based on an amount. 2. A direct injection type wherein a fuel injection valve for directly injecting fuel into a cylinder is provided, and a combustion method is switched between stratified combustion by injection in a compression stroke and homogeneous combustion by injection in an intake stroke. In the fuel injection control device of the spark ignition engine, while setting the fuel injection amount corresponding to the combustion method for each cylinder, the injection timing during stratified combustion is set to the maximum value of the fuel injection amount for stratified combustion for each cylinder. A fuel injection control device for a direct injection spark ignition engine, wherein the fuel injection control device is determined based on the following. 3. A direct injection type wherein a fuel injection valve for directly injecting fuel into a cylinder is provided, and a combustion method is switched between stratified combustion by injection in a compression stroke and homogeneous combustion by injection in an intake stroke. In a fuel injection control device for a spark ignition engine, a fuel injection amount corresponding to a combustion method is calculated at a predetermined calculation cycle, and a fuel injection amount corresponding to a combustion method is set for each cylinder based on the fuel injection amount. On the other hand, the injection timing at the time of stratified combustion is the latest value of the fuel injection amount for the stratified combustion set for the next injection cylinder and the fuel injection amount for the stratified combustion calculated at the predetermined calculation cycle. A fuel injection control device for a direct-injection spark ignition engine, which is determined based on the larger one of the following. 4. The apparatus according to claim 1, wherein said injection timing is set as an angle from a reference angle signal output at an early stage of a compression stroke to an injection start timing.
The fuel injection control device for a direct injection spark ignition engine according to any one of the above.