JPH10103117A - Fuel injection timing control device for cylinder injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve startability by improving ignitability and combustibility during cranking of an engine, also smoothly performing a rise up of engine speed after cranking and a transfer to an idle condition, in a cylinder injection type engine. SOLUTION: In a cylinder injection type engine such that by injection timing adjusting means 22, a spark plug and an injector 12 are provided to appear relating to a combustion chamber, from the injector 12, fuel is directly injected into the combustion chamber, in intake stroke injection injecting fuel in an intake stroke and compression stroke injection injecting fuel in a compression stroke, injection timing can be changed. By control means 23, when the engine is started, a period from cranking start to rise up of an engine speed is intake stroke injection, thereafter so as to switch injection to the compression stroke injection, the injection timing adjusting means 22 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder injection type engine in which a spark plug and a fuel injection valve are provided in a combustion chamber, and in which a fuel injection timing from the fuel injection valve is controlled. The present invention relates to a fuel injection timing control device.

[0002]

2. Description of the Related Art Conventionally, in a spark ignition type engine (gasoline engine) in which ignition is performed by a spark plug, an injector having a tip facing a combustion chamber is provided so as to directly inject fuel into the combustion chamber, and at least the engine is provided with an injector. In-cylinder injection in which fuel is improved by injecting fuel from the injector in the late stage of the compression stroke in a low speed and low load region to perform stratified combustion (combustion in a state where the air-fuel mixture is unevenly distributed around the spark plug) Type engines are known.

In this type of engine, the fuel injection timing from the injector can be changed between a compression stroke and an intake stroke, so that stratified combustion is performed when the compression stroke injection is performed, and uniform combustion is performed when the intake stroke injection is performed. (Combustion in a state in which the air-fuel mixture is uniformly dispersed in the combustion chamber), and it has been considered that the compression stroke injection and the intake stroke injection can be selectively used according to the operation state.

[0004] In particular, as a control at the time of starting the engine, for example, as shown in Japanese Patent Application Laid-Open No. 60-56146,
A device has been proposed in which compression stroke injection is performed during cranking, and intake stroke injection is performed after cranking. This device attempts to ignite in a rich state around the spark plug by stratification during cranking,
Further, after the cranking, the air-fuel mixture around the spark plug is prevented from becoming excessive, thereby preventing smoldering.

[0005]

However, if the compression stroke injection is performed during cranking as in the conventional apparatus disclosed in the above-mentioned publication, the engine speed is extremely low and unstable during cranking. It is difficult to control the injection timing with high precision, and the deviation of the injection timing causes the injected fuel not to reach around the ignition plug at the ignition timing or to pass through the ignition plug, resulting in poor ignition, There is a problem that the startability is deteriorated and the emission of unburned gas such as HC is increased.

On the other hand, if the intake stroke injection is performed as in the above-described conventional device when the engine speed rises after cranking and then shifts to the idle speed, the amount of fuel attached to the cylinder wall surface increases, The fuel that substantially contributes to the combustion is reduced, and the rise of the engine speed is delayed. In addition, if the amount of fuel is increased after cranking in order to suppress such backlash, there is a disadvantage that the amount of unburned gas such as HC is increased.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention improves ignition and combustibility during cranking of an engine, and enables smooth rise of the engine speed after cranking and transition to an idle state. It is an object of the present invention to provide a fuel injection timing control device for an in-cylinder injection type engine.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides an ignition plug and a fuel injection valve provided in a combustion chamber, from which fuel is directly injected into the combustion chamber. In the cylinder injection type engine, an injection timing adjusting means for changing an injection timing between an intake stroke injection for injecting fuel during an intake stroke, and a compression stroke injection for injecting fuel during a compression stroke, And control means for controlling the injection timing adjusting means so that the period from the start of cranking to the rise of the engine speed is taken as the intake stroke injection, and thereafter switched to the compression stroke injection.

According to this configuration, during the period from the start of cranking to the rise of the engine speed, uniform combustion is performed by the intake stroke injection, so that the engine speed is extremely low and unstable even when the engine speed fluctuates. The ignitability and the combustibility are not deteriorated due to the difference in the injection timing, and the combustion is performed well. Further, after the engine speed rises, stratified combustion is performed by the compression stroke injection, whereby fuel adhesion to the cylinder wall is suppressed, the injected fuel effectively contributes to combustion, and the engine speed rises and idles. The transition to the state is performed smoothly.

In this fuel injection timing control device, the control means controls the switching from the intake stroke injection to the compression stroke injection by controlling the injection timing adjusting means, when the engine speed is equal to or higher than the cranking speed, and What is necessary is just to perform it when exceeding the set rotation speed lower than the rotation speed.

In the idle state after the switching to the compression stroke injection, when the temperature of the catalyst device in the exhaust passage is low and in a low temperature state, the control means controls the injection timing adjusting means to switch to the intake stroke injection again. It is preferable to control.

With this configuration, after the intake stroke injection during the period from the start of cranking to the rise of the engine speed and the compression stroke injection during the period from the rise of the engine speed to the completion of the transition to the idle state,
In the low temperature state, the exhaust stroke temperature is increased by performing the intake stroke injection, and the warm-up of the catalyst device is promoted.

When the fuel injection valve and the spark plug are arranged so that the spark plug is interposed in the spray area from the fuel injection valve, the fuel adhesion to the cylinder wall surface during the compression stroke injection is suppressed. Stratified combustion is performed. And especially in the cylinder injection type engine of such a structure,
During the compression stroke injection, it is necessary to control the fuel injection timing so that the fuel injected from the spark plug passes in the vicinity of the spark plug and the ignition timing. Although it is difficult to perform such control with high precision, in the present invention, the intake stroke injection is performed until the engine speed rises, so that the injection timing is easily controlled.

Further, when the fuel pump for supplying fuel to the fuel injection valve is driven by an engine output shaft,
Since the rise of the engine speed after cranking is smoothed by the above fuel injection timing device, the fuel pressure of the fuel supplied by the fuel pump also rises smoothly.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of an in-cylinder injection type engine to which the fuel injection timing control device of the present invention is applied, and FIG. 2 is a schematic plan view of the engine. In these figures, reference numeral 1 denotes a cylinder head installed on a cylinder block 2, and 3 denotes a piston arranged in a cylinder bore 4 of the cylinder block 2, and a combustion is generated between an upper surface of the piston 3 and a lower surface of the cylinder head 1. A chamber 5 is formed, and a concave portion forming the ceiling of the combustion chamber 5 is provided on the lower surface side of the cylinder head 1 in this portion.

In the cylinder head 1, an intake port and an exhaust port which open to the combustion chamber 5 are formed. In this embodiment, two intake ports 6, 7 and two exhaust ports 8, 9 are provided for each cylinder. Is formed. Each intake port 6, 7 is equipped with an intake valve 10, and each exhaust port 8, 9
Are equipped with exhaust valves 11 respectively.

Further, an injector (fuel injection valve) 12 for directly injecting fuel into the combustion chamber 5 and a spark plug 13 are attached to the cylinder head 1, and the tip of the injector 12 is substantially the same as the combustion chamber 5. Placed on the periphery,
The tip of the spark plug 13 is disposed substantially at the center of the ceiling of the combustion chamber 5.

The injector 12 is attached to the cylinder head 1 below the portion where the intake ports 6 and 7 are provided on one side of the combustion chamber 5, and the direction of injection from the injector 12 is obliquely downward. The fuel is injected in a direction toward the upper surface of the piston 3 near the periphery of the combustion chamber facing the injector arrangement portion. A recess 14 is formed on the upper surface of the piston 3 from a substantially central portion thereof to the vicinity of the periphery of the combustion chamber on the side (exhaust side) facing the injector 12. Further, the ignition plug 13 is disposed so as to be interposed in the spray area from the injector 12.

By arranging the injector 12 and the spark plug 13 in this way, stratified charge combustion is performed while suppressing fuel adhesion to the cylinder wall during the compression stroke injection, which is advantageous for improving combustion efficiency.

The injector 12 is formed of a narrow-angle injector so that the spray angle is at least 30 ° or less when the compression stroke injection is performed. Preferably, the injector 12 has an injection port shape that generates swirl in the spray. And a high-pressure swirl injector.

The injector 12 has a fuel pump 15
The fuel pump 15 is connected to an engine output shaft via a transmission means.

An intake manifold 18 having intake passages 16 and 17 corresponding thereto is connected to the intake ports 6 and 7, and a swirl control valve 19 is provided in the intake passage 17. . On the other hand, the exhaust ports 8 and 9
Is connected to an exhaust manifold (not shown), and a catalyst device (not shown) for purifying exhaust gas is provided in an exhaust passage downstream of the exhaust manifold.

FIG. 3 shows a control system for controlling the timing of fuel injection from the injector 12 and the like. In FIG. 1, the control system includes an engine control unit (ECU) 21 including a microcomputer and the like. The control unit 21 includes an injection timing adjusting unit 22 for adjusting a fuel injection timing, and a control unit 23 for controlling the same. And are included. The injection timing adjusting means 22 can change the fuel injection timing between an intake stroke injection for injecting fuel during the intake stroke and a compression stroke injection for injecting fuel at a later stage of the compression stroke.

The control means 23 responds to signals from a starter switch 25 for detecting the operation of the starter, a speed sensor 26 for detecting the engine speed, and the like. The intake stroke injection is performed during the period before the engine speed exceeds the set rotation speed and rises, and then the injection timing adjusting means 22 is controlled so as to switch to the compression stroke injection. The set rotation speed is set to a value equal to or higher than the cranking rotation speed and lower than the idle rotation speed, for example, 300 rpm.

Further, the control means 23 controls the operation of the catalyst device in the exhaust passage in an idling state after a predetermined time set by the counter 24 has elapsed since the switching from the intake stroke injection to the compression stroke injection at the time of engine start. When the temperature is low and the temperature is low, the operation is switched to the intake stroke injection again.

The control during normal operation after starting and warming-up includes a compression stroke injection in a low and medium speed operation region in order to improve fuel efficiency by stratified combustion in a low and medium load operation region and a high load region. In addition, in the high rotation speed region, the intake stroke injection may be performed to perform uniform combustion.

The control of the fuel injection timing at the start performed by the control unit 21 will be specifically described with reference to the flowchart of FIG.

When the control of this flowchart is started, it is first determined whether or not the starter switch 25 is ON (step S1). While the starter switch 25 is cranking, the initial value of the rising counter C is determined (step S1). Along with step S2), intake stroke injection is performed (step S3). Note that the rising counter C determines the period of the compression stroke injection after the engine speed rises later, and the initial value may be a constant value. It may be set to a large value.

If the determination in step S1 is NO, it is then determined whether or not the engine speed Ne is 300 rpm or more (step S4). If the determination is NO, the same step as when the starter switch is ON is performed. S2
Then, the process proceeds to step S3, where the intake stroke injection is performed.

When the determination in step S1 is NO and the determination in step S4 is YES, that is, when the engine speed Ne rises to 300 rpm or more after the starter operates, it is determined whether or not the rising counter C has become 0. It is determined (step S5), and when the determination is NO, the counter C is decremented (step S6).
At the same time, compression stroke injection is performed (step S7).
Then, the processing of steps S6 and S7 is repeated until the rising counter C becomes 0.

When the determination in step S5 is YES (the rising counter C is 0), that is, when the time set by the counter C has elapsed since the engine speed Ne became 300 rpm or more, the exhaust gas temperature TE Is the set value α
It is determined whether or not it is below (step S8). If the determination in step S8 is YES, step S3
Is switched to the intake stroke injection again.
On the other hand, when the determination in step S8 is NO (the exhaust gas temperature TE
Is higher than the set value α), the routine shifts to injection timing control during normal operation (step S9). For example, if the engine is idling, compression stroke injection is performed.

The operation of the apparatus according to this embodiment as described above will be described below.

At the time of engine startup, during cranking, the engine speed Ne is extremely low at about 250 rpm and fluctuates unstable. Therefore, when the compression stroke injection is performed, the timing at which the injected fuel passes near the spark plug 13 It is difficult to adjust the injection timing so that the ignition timing and the ignition timing correspond properly, and it is difficult to ensure ignitability. For this reason, during the period from the start of cranking until the engine speed starts rising, the fuel is uniformly distributed in the combustion chamber 5 due to the intake stroke injection, and the injection timing is not strictly adjusted. Even so, ignitability is ensured.

When the engine reaches a full explosion state and the engine rotation speed Ne starts to rise and becomes 300 rpm or more, the compression stroke injection is performed.
The transition to the idle state is performed smoothly. In other words, when the engine speed Ne becomes high to some extent, it is possible to easily adjust the fuel injection timing so that ignition is performed even in the compression stroke injection at a time when a large amount of injected fuel exists near the ignition plug 13, and the compression stroke injection is performed. By performing the stratified combustion, the fuel adhesion to the cylinder wall surface is suppressed, and the injected fuel effectively contributes to the combustion, thereby increasing the combustion efficiency. Therefore, the rise of the engine speed and the transition to the idle state are performed smoothly.

The compression stroke injection is performed at least during the time from when the engine speed rises to when the engine speed stabilizes at the idle speed (set time of the counter C). In this case, the lower the engine temperature, the longer the time required for the engine speed to stabilize, and thus the longer the set time of the counter C.

After the elapse of the set time, when the exhaust gas temperature TE is high, the compression stroke injection is continued in an idle state as a normal control, but the exhaust gas temperature TE is lower than the set value α. If the catalyst device in the exhaust passage is not activated, the operation is switched to the intake stroke injection again. As a result, the increase in the exhaust gas temperature TE and the warm-up of the catalyst device due to the increase are promoted. That is, when stratified combustion is performed in the compression stroke injection, the combustion efficiency is increased, but the air is in an excessively lean state.
On the other hand, according to the intake stroke injection, although the combustion efficiency is lower than that of the compression stroke injection, the exhaust gas temperature is more likely to rise, and the warm-up of the catalyst device is promoted.

Therefore, according to the apparatus of this embodiment, FIG.
As shown in the data of (1), the startability and the effect of increasing the exhaust gas temperature during the cold start are enhanced. This data is obtained when the intake stroke injection is performed from cranking to after cranking (FIG. 6), and the compression stroke injection is continued even when the exhaust temperature is low after a set time after switching to the compression stroke injection after cranking. This will be described in comparison with the data (FIG. 7) in the case of performing the operation.

When the intake stroke injection is performed from cranking to after cranking, as shown in FIG. 6, even after the engine speed Ne starts rising, the combustion stability is hindered due to fuel adhesion to the cylinder wall surface. However, the engine rotation speed Ne does not smoothly shift to the idle rotation speed, and a slack occurs. Moreover, this engine speed Ne
While the backlash is occurring, the increase in the fuel pressure Pf provided by the fuel pump 15 driven by the engine output shaft is also backlashed, so that the control of the fuel injection amount is not accurate and the combustion stability is further improved. It is easy to be hindered. In addition, fuel is likely to adhere to the cylinder wall as described above,
Since the combustion efficiency is not good, the amount of HC emission tends to increase.

On the other hand, when the engine is switched to the compression stroke injection from the time when the engine speed Ne starts rising, the fuel adhesion to the cylinder wall surface is prevented and the combustion efficiency is increased. As described above, the rise of the engine speed Ne and the transition to the idle speed are smoothly performed, and the fuel pressure Pf is also smoothly increased to an appropriate pressure, so that the fuel injection amount is well controlled. Further, since the adhesion of fuel to the cylinder wall is suppressed and the fuel burns efficiently, the amount of HC emission is reduced.

Further, when the compression stroke injection is performed from the time when the engine speed Ne starts rising at the time of the cold start, the exhaust gas temperature TE does not easily rise, and the compression stroke injection continues as shown in FIG. The state in which the exhaust gas temperature TE does not rise to the temperature required for activating the catalytic device continues for a long time, which is disadvantageous in terms of exhaust gas purification. In the following cases, the operation is switched to the intake stroke injection, so that the exhaust gas temperature TE rises and the catalyst device is activated as shown in FIG.

In the above embodiment, the set rotation speed for switching from the intake stroke injection to the compression stroke injection is set to 300 rpm. However, the set rotation speed is set to a value equal to or higher than the cranking rotation speed so that the rise of the engine rotation speed can be reliably determined. And a value lower than the idle speed. Further, in the above embodiment, whether the temperature of the catalyst device is lower than the activation temperature is checked based on whether the exhaust gas temperature TE is equal to or less than the set value α. You may make it detect.

[0042]

As described above, according to the present invention, in the cylinder injection type engine, the period from the start of cranking to the rise of the engine speed at the start of the engine is taken as the intake stroke injection, and thereafter switched to the compression stroke injection. Therefore, ignitability is ensured by uniform combustion during the period from the start of cranking until the engine speed rises, and after the engine speed rises, stratified combustion suppresses fuel adhesion to the cylinder wall and improves combustion efficiency. Raise it,
The rise of the engine speed and the transition to the idle state can be smoothly performed, and thus the startability can be greatly improved.

Further, in this device, when the temperature of the catalyst device in the exhaust passage is low and low in the idle state after the switching to the compression stroke injection, the injection timing adjusting means is controlled to switch back to the intake stroke injection again. Then, promotion of warming-up of the catalyst device at the time of cold start can be favorably performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a direct injection engine to which a fuel injection timing control device according to an embodiment of the present invention is applied.

FIG. 2 is a schematic plan view of a combustion chamber and its vicinity.

FIG. 3 is a block diagram of a control system.

FIG. 4 is a flowchart of fuel injection timing control.

FIG. 5 is a diagram showing changes in engine speed, fuel pressure, and exhaust temperature during a transition from engine start to idle state for a case according to an embodiment of the present invention.

FIG. 6 is a diagram showing changes in the engine speed, fuel pressure, and exhaust temperature during transition from engine startup to an idle state in a case where intake stroke injection is performed from cranking to after cranking.

FIG. 7: Changes in engine speed, fuel pressure, and exhaust temperature during the transition from engine start to idle state are switched to compression stroke injection after cranking, and compression stroke injection is continued even when the exhaust temperature is low after a set time. It is a figure showing about the case where it was made to do.

[Explanation of symbols]

 Reference Signs List 5 Combustion chamber 12 Injector 13 Spark plug 15 Fuel pump 21 Control unit 22 Injection timing adjusting means 23 Control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 312 F02D 45/00 312R

Claims (5)

[Claims] An in-cylinder injection type engine in which an ignition plug and a fuel injection valve are provided to a combustion chamber and fuel is directly injected from the fuel injection valve into the combustion chamber, fuel is injected during an intake stroke. Injection timing adjusting means for enabling the injection timing to be changed between an intake stroke injection to be performed and a compression stroke injection to inject fuel during a compression stroke, and a period from the start of cranking to the rise of the engine speed at the start of the engine during the intake stroke. A fuel injection timing control device for a direct injection type engine, comprising: control means for controlling said injection timing adjustment means so as to perform injection and then switch to compression stroke injection. 2. The control means switches the intake stroke injection to the compression stroke injection by controlling the injection timing adjusting means when the engine speed is equal to or greater than the cranking speed.
2. The fuel injection timing control system for a direct injection engine according to claim 1, wherein the control is performed when the engine speed exceeds a set engine speed lower than an idle engine speed. 3. The control means controls the injection timing adjusting means to switch to the intake stroke injection again when the temperature of the catalyst device in the exhaust passage is low and low in the idle state after switching to the compression stroke injection. The fuel injection timing control device according to claim 1, wherein the control is performed. 4. The fuel according to claim 1, wherein the fuel injection valve and the spark plug are arranged such that a spark plug is interposed in a spray area from the fuel injection valve. Injection timing control device. 5. The fuel injection timing control device according to claim 1, wherein the fuel pump that supplies fuel to the fuel injection valve is driven by an engine output shaft.