JP2003193894A - Fuel injection timing control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a fuel injection timing in the point of securing an atomizing time, improving exhaust emission and improving startability when injecting a fuel over a plurality of strokes with a cylinder injection engine having a greater pulse width and a shorter injection possible time. <P>SOLUTION: A cylinder injection type fuel injection valve 18 is provided near an intake valve 12 facing into a combustion chamber 6. When the fuel injection valve 18 injects a fuel at a timing of the lift amount of the intake valve 12 being a preset amount or more, the fuel collides with the intake valve 12 and splashes on a spark plug 16 to cause a misfire. An ECU 50 allows the fuel injection valve 18 to inject the fuel out of the timing of the lift amount of the intake valve 12 being the preset amount or more, or rather the fuel parted before and after the timing, during the intake stroke. In this case, the fuel is injected according to the priority of the first half of the intake stroke, the second half of the intake stroke, a compression stroke and an exhaust stroke. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel injection timing control device. Specifically, in a cylinder injection type engine that directly injects fuel into the combustion chamber, in the technical field of improving fuel injection timing from the viewpoint of ensuring atomization time, improving exhaust emission, improving startability, etc. Belong to

[0002]

2. Description of the Related Art Generally, in an internal combustion engine (such as a reciprocating gasoline engine) that obtains an output by burning a mixture of air and fuel, the fuel injection amount is set based on the operating state of the engine. For example, at the time of starting, the fuel injection amount is set depending on the cooling water temperature of the engine, and after the starting, the fuel injection amount is set depending on the rotation speed, the load state (for example, the intake air amount), and the like. Then, the pulse width (valve opening time) of the drive pulse signal for the fuel injection valve is determined so that the set injection amount is fully injected. In that case, the pulse width changes according to the pressure of the fuel supplied from the fuel supply system including the fuel pump to the fuel injection valve. Obviously, the higher the fuel pressure to the fuel injection valve, the shorter the pulse width will be.

In the case of an in-cylinder injection type (direct injection) engine in which a fuel injection valve is arranged in a combustion chamber and fuel is directly injected from the fuel injection valve, the operating state of the engine (for example, rotation speed or The target fuel pressure is set on the basis of the temperature state of the combustion chamber, etc., and the discharge amount of the fuel pump is feedback-controlled so that the actual fuel pressure for the fuel injection valve converges to the target fuel pressure. As a result, when a drive pulse signal having a predetermined pulse width is output to the fuel injection valve, a predetermined amount of fuel is injected into the combustion chamber, and the optimum air-fuel ratio / optimal combustion state that matches the operating state of the engine is realized.

In a four-cycle engine, fuel is generally injected in the intake stroke. The injected fuel is sufficiently mixed with intake air, and the combustion chamber is filled with a homogeneous mixture rich in ignitability and combustibility. However, in exceptional cases, in a cylinder injection type engine, fuel may be injected in a compression stroke, and a locally rich mixture may be unevenly distributed / stratified around electrodes of a spark plug to perform lean burn operation.

As described above, the fuel injection amount increases or decreases depending on various factors of the operating condition of the engine. For example, at the time of starting, the amount is increased as the water temperature is lower. In addition, when the fuel supply system (for example, the fuel pump) malfunctions at startup and the pressure of the fuel supplied to the fuel injection valve does not reach the specified value, the fuel injection amount is increased and corrected to ensure startability. Is done. On the other hand, after starting, when accelerating (at high load)
As the target air-fuel ratio decreases, the amount is increased. In this way, the pulse width generally becomes longer as the fuel injection amount is increased (assuming the fuel pressure is the same). Furthermore, the lower the fuel pressure, the longer the pulse width (assuming the same fuel injection amount). When the pulse width becomes long in this way, it becomes difficult to completely inject the fuel injection amount set based on the operating state of the engine (or increased correction) only in the intake stroke, and it is divided into other strokes. You have to jet.

Further, as the engine speed increases, the time of the intake stroke becomes shorter and the time during which injection is possible becomes shorter accordingly. Even if the available injection time is shortened in this way, it becomes difficult to completely inject the fuel injection amount set based on the operating state of the engine only in the intake stroke, and the fuel must be divided into other strokes for injection. I won't get it.

Further, in Japanese Patent Laid-Open No. 8-4578,
In a cylinder injection engine, when fuel is injected from the fuel injection valve located near the intake valve in the intake stroke at a time when the lift amount of the intake valve becomes a predetermined amount or more, the injected fuel lifts the intake valve. In the intake stroke, in order to prevent such problems, the lift amount of the intake valve must be increased in order to prevent such troubles by colliding with the back surface of the engine and bouncing back to the ignition plug, causing so-called plug fogging and causing misfire and smoldering. It is disclosed that the fuel is divided and injected before and after the time when the amount becomes equal to or more than a predetermined amount. In this case as well, the injectable time becomes short, and it is difficult to completely inject the predetermined fuel injection amount only in the intake stroke, so that the fuel may be divided into other strokes and injected.

[0008]

As described above, in order to completely inject the fuel injection amount set based on the operating state of the engine, the fuel may be injected in the compression stroke and the exhaust stroke other than the intake stroke. Although it is possible, there is no technical suggestion as to which stroke the fuel injection should be prioritized in that case. At that time, for example, in order to efficiently obtain the explosive combustion energy of the air-fuel mixture, it is basically important to sufficiently vaporize and atomize the injected fuel by the ignition timing. First of all, it is necessary to take into account the fact that unburned components (HC) increase due to lack of air ignitability and combustibility, and exhaust emission decreases.

Further, in the case of an in-cylinder injection type engine, the fuel injected in the exhaust stroke has a higher rate of being carried away into the exhaust gas and flowing out as compared with the port injection type engine, which causes a reduction in exhaust emission. Must also be carefully considered. In addition, smooth starting of the engine is the most important issue at the time of starting. Furthermore, 2 strokes including the intake stroke are not enough, 3 strokes including the intake stroke
It is necessary to prioritize the possibility that fuel may be injected throughout the stroke.

The present invention has been made in view of the above circumstances, and in a cylinder injection type engine, when fuel is injected over a plurality of strokes, the atomization time is secured and the exhaust emission is improved. An object of the present invention is to provide an improved fuel injection timing from the viewpoint of improving startability.

[0011]

That is, the invention according to claim 1 is provided with a fuel injection valve for directly injecting fuel into a combustion chamber, and an injection amount setting for setting a fuel injection amount based on an operating state of an engine. Means, an injection timing setting means for setting the fuel injection timing so that the entire amount of fuel injection set by the setting means is injected, and the above-mentioned means for injecting fuel at the fuel injection timing set by the setting means. A fuel injection timing control device for an engine, comprising: a fuel injection control means for controlling a fuel injection valve, wherein the injection timing setting means sets the fuel injection timing in accordance with the priority order of an intake stroke, a compression stroke, and an exhaust stroke. It is characterized in that it is configured.

According to the present invention, the fuel injection amount set on the basis of the operating condition of the engine is fully injected.
When the fuel is injected over a plurality of strokes, the fuel is injected according to the priority order of the intake stroke, the compression stroke, and the exhaust stroke. First, because the intake stroke, which has a longer time from fuel injection to ignition than the compression stroke, is given the highest priority, the atomization time of fuel is secured, a mixture rich in ignitability and combustibility is obtained, and high output is obtained. Efficiently obtained, unburned components are reduced, and exhaust emission is improved.

On the other hand, if the compression stroke is given the highest priority, the time until ignition is short and the atomization time is short, resulting in problems such as insufficient output, misfire, and a decrease in exhaust emission due to an increase in unburned components. Is likely to occur.

Further, since the priority of the exhaust stroke is set to be the lowest, when the fuel is normally injected in the two strokes (intake and compression), the fuel is not injected in the exhaust stroke and the three strokes (intake and compression. Only when the fuel is injected over the exhaust gas, the minimum amount of fuel remaining until the end is injected in the exhaust stroke. As a result, the reduction of exhaust emission is further suppressed.

The invention described in claim 2 is the same as claim 1
In the invention described in (1), the fuel injection valve is arranged at a position where the fuel collides with the intake valve when the fuel is injected at a time when the lift amount of the intake valve becomes a predetermined amount or more, and the injection timing setting means is During the stroke, the fuel is divided and injected before and after the timing when the lift amount of the intake valve becomes a predetermined amount or more, and the first half of the intake stroke, the second half of the intake stroke, the compression stroke,
The fuel injection timing is set according to the priority of the exhaust stroke.

The present invention addresses the problem of plug fogging peculiar to the above-mentioned cylinder injection type engine (the problem described in Japanese Patent Laid-Open No. 8-4578), so that the lift amount of the intake valve becomes a predetermined amount or more. It shows the priority order between the strokes when the fuel is split and injected before and after the timing. According to this, by comparing the first half of the intake stroke and the second half of the intake stroke, the first half of the intake stroke, which has a longer time until ignition, is prioritized over the latter half of the intake stroke. Therefore,
The effects of ensuring the atomization time of fuel and suppressing the reduction of exhaust emission, which are exhibited by setting the priority to the intake stroke, the compression stroke, and the exhaust stroke, are not impaired.

Next, the invention described in claim 3 is the same as claim 1
Or the fuel supply means for supplying fuel to the fuel injection valve, the abnormality detection means for detecting an abnormality in which the pressure of the fuel supplied by the supply means to the fuel injection valve does not reach a predetermined value, and When the abnormality is detected by the detection means, a correction means for increasing and correcting the fuel injection amount set by the injection amount setting means is provided, and the injection timing setting means, when the abnormality is detected when the engine is started, The fuel injection timing is set according to the priority order of the exhaust stroke, the intake stroke, and the compression stroke.

The present invention shows the priority order among the strokes when the abnormality of the fuel supply means is detected at the time of starting the engine and the fuel injection amount is increased and corrected. According to this, fuel is injected according to the priority order of the exhaust stroke, the intake stroke, and the compression stroke. First, in the state where the fuel supply means is abnormal and the fuel pressure does not rise, the degree of atomization of the fuel spray is reduced, vaporization and atomization is not promoted, and the combustion stability is reduced. Therefore, if priority is given to fuel injection in the compression stroke in which the time until ignition is short and the atomization time is short, the ignitability and combustibility of the air-fuel mixture are further deteriorated, and the engine start becomes unsuccessful.

On the other hand, in the exhaust stroke, compared with other intake strokes and compression strokes, the time until ignition is the longest and the atomization time is sufficiently long. Further, since the intake stroke and the compression stroke are before ignition, while the exhaust stroke is after ignition, when fuel is injected in this exhaust stroke, combustion has already occurred and the temperature is rising. Therefore, even if the atomization degree of the fuel spray is reduced, the vaporization and atomization is accelerated by the high temperature, and the combustion stability is improved.

For the above reasons, the fuel injection in the exhaust stroke is given the highest priority, and the compression stroke is given the lowest priority. As a result, the startability of the engine is ensured even in the situation where the fuel pressure does not rise. As a result, the fuel injection is always performed in the exhaust stroke, but the amount of fuel outflow in the exhaust stroke is compensated by the increase correction.

Next, the invention of claim 4 is the same as that of claim 3
In the invention described in (1), the fuel injection valve is arranged at a position where the fuel collides with the intake valve when the fuel is injected at a time when the lift amount of the intake valve becomes a predetermined amount or more, and the injection timing setting means is During the stroke, the time when the lift amount of the intake valve becomes a predetermined amount or more is removed and the fuel is divided and injected before and after the time, and when an abnormality is detected by the abnormality detecting means at the time of starting the engine, the exhaust stroke, It is characterized in that the fuel injection timing is set according to the priorities of the first half of the intake stroke, the second half of the intake stroke, and the compression stroke.

According to the present invention, similarly to the second aspect of the invention, when the fuel is split and injected before and after the time when the lift amount of the intake valve becomes equal to or more than the predetermined amount, the engine is started and abnormal. This shows the priority order between the processes. According to this, by comparing the first half of the intake stroke and the second half of the intake stroke, the first half of the intake stroke, which has a longer time until ignition, is prioritized over the latter half of the intake stroke. Therefore, similar to the invention described in claim 2, the effect of ensuring the atomization time of fuel and improving exhaust emission, which is achieved by setting the priority of the intake stroke prior to the priority of the compression stroke, is obtained. It is not damaged. Hereinafter, the present invention will be described in more detail through embodiments of the invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall structure of a cylinder injection type four-cycle engine 1 according to an embodiment of the present invention. The engine 1 has a cylinder block 3 in which a plurality of cylinders 2 ... 2 (only one is shown) are arranged in series, and a cylinder head 4 mounted on the cylinder block 3. A piston 5 is vertically reciprocally fitted in each cylinder 2 to define a combustion chamber 6. A crankshaft 7 is rotatably supported by the cylinder block 3, and a piston 5 is attached to the crankshaft 7.
Are connected by a connecting rod 8. An electromagnetic pickup type crank angle sensor 9 for detecting a crank angle is provided on one end side of the crank shaft 7.

Two intake ports 1 are provided on the ceiling of the combustion chamber 6.
0 and 10 and two exhaust ports 11 and 11 (only one is shown for each) are open. An intake valve 12 or an exhaust valve 13 is provided at each opening. The intake ports 10 and 10 linearly extend obliquely upward from the combustion chamber 6 and open independently on the side surface of the engine 1 (right side surface in FIG. 1).
The exhaust ports 11 and 11 extend horizontally immediately from the combustion chamber 6 and merge into one on the way to the other side surface of the engine 1 (see FIG. 1).
(Left side of the). At the top of the combustion chamber 6 above 4
An ignition plug 16 is disposed surrounded by the two intake / exhaust valves 12, 12, 13, 13. The base end of the spark plug 16 is connected to the ignition circuit 17, and the ignition circuit 17 is connected to each cylinder 2
Each spark plug 16 is energized at a predetermined ignition timing.

Intake port 1 at the ceiling of combustion chamber 6
Injector (fuel injection valve) so that it is sandwiched between 0 and 10
18 is arranged so as to face the combustion chamber 6. The injector 18 directly injects fuel into the combustion chamber 6 from a position slightly below the intake ports 10, 10. Each injector 18
The base end of 18 is a fuel distribution pipe 19 common to all cylinders 2
It is connected to the. The fuel distribution pipe 19 distributes the high-pressure fuel supplied from the fuel supply system 20 to the cylinders 2 ...

The high pressure fuel supply system 20 is constructed, for example, as shown in FIG. Fuel distribution pipe 19 and fuel tank 2
1, the low-pressure fuel pump 23, the low-pressure regulator 24, the fuel filter 25, the high-pressure fuel pump 26, and the high-pressure regulator 27 are arranged in this order from the upstream side to the downstream side of the fuel passage 22 communicating with 1.
And are provided. The fuel sucked up from the fuel tank 21 by the low-pressure fuel pump 23 is the low-pressure regulator 2
The pressure is adjusted at 4, filtered by the filter 25, and sent under pressure to the high-pressure fuel pump 26. The high pressure fuel pump 26 and the high pressure regulator 27 are connected to the fuel tank 21 through a return passage 29. The return passage 29 is provided with a low pressure regulator 28 for adjusting the pressure of the fuel returned to the fuel tank 21. A part of the fuel boosted by the high-pressure fuel pump 26 is returned to the fuel tank 21 through the return passage 29 while the flow rate is adjusted by the high-pressure regulator 27.

The high pressure regulator 27 is constructed by using a solenoid valve. That is, the high-pressure regulator 27 is controlled by controlling the energization time and the energization timing for the solenoid valve, and as a result, the pressure state of the fuel supplied to the fuel distribution pipe 19 is set to an appropriate value (for example, 3 to 13 MPa, during stratified charge combustion operation). 4-7 MPa). In the fuel supply system 20 shown in FIG. 2A, the high pressure regulator 27 has the injector 1
The fuel injection pressure by 8 will be adjusted. A fuel pressure sensor 53 that detects the fuel pressure supplied from the fuel supply system 20 to the injector 18 is provided in the fuel distribution pipe 19.

Instead of this, a high-pressure fuel supply system 20 'having a structure as shown in FIG. 2 (b) may be adopted. In this fuel supply system 20 ', an electrically driven high pressure pump 26' capable of changing the discharge amount of fuel as a high pressure fuel pump over a wide range.
Is used. By controlling the electric pump 26 ', the discharge amount of fuel from the pump 26' to the fuel distribution pipe 19 can be adjusted, whereby the fuel distribution pipe 1
It is possible to control the pressure state of the fuel supplied to 9. In this case, the electric high pressure pump 26 ′ adjusts the fuel injection pressure of the injector 18. In the fuel supply system 20 of FIG. 2B, the high pressure regulator 2
7 and the return passage 29 can be omitted.

Returning to FIG. 1, an intake passage 30 is arranged on the side surface (the right side surface in FIG. 1) of the engine 1. Intake passage 30
Communicates with the intake ports 10, 10 of each cylinder 2 and supplies intake air filtered by an air cleaner (not shown) to the combustion chamber 6. In the intake passage 30, a hot wire type air flow sensor 31 for detecting the amount of intake air taken into the engine 1 from the upstream side to the downstream side, an electric throttle valve 32 for adjusting the opening degree of the intake passage 30, and a surge tank. 33 and the like are provided. Although not shown, the throttle valve 32 is not mechanically connected to the accelerator pedal and is driven by an electric drive motor. The intake passage 30 on the downstream side of the surge tank 33 is an independent passage branched for each cylinder 2. The downstream end of each independent passage is further branched into two, and each intake port 1
It communicates with 0 and 10.

An exhaust passage 36 for discharging burnt gas (exhaust gas) from the combustion chamber 6 to the other side surface of the engine 1 (left side surface in FIG. 1).
Is provided. The upstream end of the exhaust passage 36 is located in each cylinder 2
It is an exhaust manifold 37 that branches to communicate with the exhaust port 11. A linear O ₂ sensor 38 for detecting the residual oxygen concentration in the exhaust gas is arranged at the collecting portion of the exhaust manifold 37. The air-fuel ratio of the air-fuel mixture in the combustion chamber 6 is detected based on the detection result of the sensor 38. The sensor 38 produces a linear output with respect to the oxygen concentration in a predetermined air-fuel ratio range including the stoichiometric air-fuel ratio.

An exhaust pipe 39 is provided at the collecting portion of the exhaust manifold 37.
Is connected to the upstream end of the exhaust pipe 39, and a catalyst device 40 for purifying exhaust gas is connected to the downstream end of the exhaust pipe 39. This catalytic device 4
0 absorbs NOx in an atmosphere where the oxygen concentration in the exhaust is high, while NOx absorbed when the oxygen concentration in the exhaust decreases.
It is a NOx absorption reduction type catalytic device that releases and purifies by reduction. The catalyst device 40 exhibits the same high level of exhaust purification performance as the three-way catalyst device in the vicinity of the theoretical air-fuel ratio. However, the NOx absorption reduction catalyst device 40 and the three-way catalyst device may be used together.

An upstream end of the EGR passage 43 opens at an upstream portion of the exhaust pipe 39. The EGR passage 43 recirculates a part of the exhaust gas flowing through the exhaust passage 36 to the intake passage 30. EGR
The downstream end of the passage 43 is connected to the intake passage 30 downstream of the throttle valve 32. An electric EGR valve 44 is disposed near the downstream end of the EGR passage 43, and the EGR valve 44 is used to
The amount of exhaust gas recirculated through the R passage 43 is adjusted.

Engine control unit (ECU)
Reference numeral 50 designates the ignition circuit 17 of the ignition plugs 16 ... 16 of each cylinder 2 ... 2, the injectors 18 ... 18, the high pressure regulator 27 of the fuel supply system 20 (in the case of the configuration of FIG. 2A) or the electric high pressure pump 26. ′ (In the case of the configuration of FIG. 2B), the operation of (the drive motor of) the electric throttle valve 32, the electric EGR valve 44 and the like are controlled.

The ECU 50 includes at least the crank angle sensor 9, the air flow sensor 31, and the linear O ₂ sensor 38.
The output signals from the accelerator opening sensor 51, which detects the opening of the accelerator pedal (accelerator operation amount), and the rotation speed of the engine 1 (the rotation speed of the crankshaft 7) are detected while inputting the respective output signals from the above. The output signal from the rotation speed sensor 52, the output signal from the fuel pressure sensor 53 that detects the fuel pressure supplied to the injector 18 from the fuel supply system 20, and the like are input.

The ECU 50 controls the ignition timing of the ignition plug 16, the fuel injection amount / injection timing / injection pressure of the injector 18, and the intake air adjusted by the throttle valve 32 based on the operating state of the engine 1 indicated by these input signals. The amount, the exhaust gas recirculation ratio adjusted by the EGR valve 44, and the like are controlled. The ECU 50 also configures the high pressure regulator 27 (see FIG. 2A) of the fuel supply system 20 so that the actual fuel pressure supplied to the injector 18 converges to the target fuel pressure set based on the operating state of the engine 1. Case) or an electric high-pressure pump 26 '(in the case of the configuration of FIG. 2B)
Feedback control.

Next, the operation control (fuel injection control) of the injector 18 in the engine 1 will be described. Figure 3
As shown in (a) to (c), in the in-cylinder injection engine 1, the lift amount of the intake valves 12, 12 from the injector 18 arranged near the intake valves 12, 12 in the intake stroke is a predetermined amount. The above time (time t2 in FIG. 3B)
When fuel is injected into the spark plug 1, the injected fuel collides with the lifted intake valves 12, 12 on the back surface (back surface of the umbrella).
There is a possibility that it bounces back to No. 6 and adheres to the electrode of the spark plug 16 (plug fogging), misfiring, smoldering, etc. occur, and combustion becomes unstable. Therefore, in order to prevent such a problem, in the intake stroke, the lift amount of the intake valves 12, 12 is set to a predetermined amount α (see FIGS. 5 and 7) or more, and
Before and after that time, the fuel is divided and injected. However, in this case, the time during which the fuel can be injected in the intake stroke becomes short, and it becomes difficult to completely inject a predetermined amount of fuel only in the intake stroke. Therefore, the remaining amount is injected in other strokes.

FIG. 4 is a flow chart showing a specific example of the post-startup fuel injection control. This program is repeatedly executed at a predetermined control cycle during the operation after the engine 1 is started. First, in step S1, the engine speed, load state (for example, intake air amount), engine cooling water temperature, fuel pressure, etc. are detected as current state quantities. Next, in step S2, as the operating state of the engine 1, the fuel injection amount is set according to the engine rotation speed and the load state. At the same time, the injector 1 is set so that the set fuel injection amount is fully injected.
The pulse width (valve opening time) of the drive pulse signal for 8 is determined. The pulse width depends on the fuel pressure supplied from the fuel supply system 20 to the injector 18. Even if the fuel injection amount is the same, the pulse width becomes longer as the fuel pressure becomes lower.

Next, at step S3, it is judged if the engine water temperature is lower than a predetermined value. If it is higher than the predetermined value, the routine proceeds to step S4, where the injection timing is set as usual. That is, the lift amount of the intake valves 12, 12 is the predetermined amount α
The injection timing is set as usual in accordance with the engine speed, the load state, the engine water temperature, the fuel pressure, the elapsed time after the start, etc., without performing the fuel split injection after the above timing. This is because when the engine water temperature is high to some extent, even if the injected fuel collides with the back surfaces of the intake valves 12 and 12 or bounces off the spark plug 16 (even if plug fogging occurs), the fuel is vaporized and atomized. Is less likely to cause misfire or smolder.
Therefore, in the intake stroke as well, fuel is injected over the entire intake stroke, as usual, regardless of the lift amount of the intake valves 12, 12.

In this case, the injection timing is set in consideration of the fact that the higher the engine speed, the shorter the possible injection time. Further, the injection timing is set in consideration of the fact that the higher the load condition is, the higher the output is required, and the fuel needs to be sufficiently atomized. Further, the injection timing is set in consideration that the lower the cooling water temperature, the longer the time required for atomizing the fuel. Further, the injection timing is set in consideration of the fact that the lower the fuel pressure, the smaller the fuel injection amount even if the same pulse width (valve opening time) is given. Further, the injection timing is set in consideration of the fact that the engine temperature does not rise as the elapsed time after starting is shorter and the time required for atomizing the fuel is longer.

Then, in step S5, injection control is executed. The fuel is injected exclusively in the intake stroke, sufficiently mixed with the intake air, and the combustion chamber 6 is filled with a homogeneous mixture rich in ignitability and combustibility.

On the other hand, when the engine water temperature is lower than the predetermined value in step S3, the process proceeds to step S6 and the intake valve 1
The fuel injection timing is set at times other than when the lift amounts 2 and 12 exceed the predetermined amount α. And as a result,
It becomes difficult to blow out all the fuel only in the intake stroke,
Since the amount left uninjected will be injected in other strokes, the priority at that time is (1) the first half of the intake stroke,
(2) The latter half of the intake stroke, (3) the compression stroke, and (4) the exhaust stroke.

That is, as illustrated in FIG. 5 (a), first, as much as possible is injected in the first half of the intake stroke (reference numeral A). Therefore, if there is a residual jet, then, as much as possible is jetted in the latter half of the intake stroke (reference numeral a). If there is still an unsprayed residue, then, as much as possible is sprayed in the compression stroke (symbol c).

Time t1 is the time when the piston 5 is at the intake top dead center. At this time, as shown in FIG. 3A, the exhaust valve 13 is almost closed and the intake valve 12 is closed. It is opening a little. At time t2, the intake valve 12
It is the time when the lift amount of is maximum. Time t3 is the time when the piston 5 is at the bottom dead center of the intake air.
As shown in (c), the intake valve 12 is almost closed. Time t4 is a time limit (crank angle) at which the injector 18 can inject fuel into the cylinder 2 in the compression stroke. That is, in the compression stroke, after this crank angle, the in-cylinder pressure becomes too high, and no matter how much the fuel pressure is increased, the fuel is directly resisted against the in-cylinder pressure and the cylinder 2
It becomes impossible to inject it.

FIG. 5 (a) shows the total amount of fuel at the time t4.
The following is an example of the case where the spray could be blown up to. On the other hand, as illustrated in FIG. 5B, when the entire amount of fuel cannot be injected by the time t4,
It will enter the exhaust stroke and inject the remaining fuel (reference d).

As described above, first, the fuel is injected with the highest priority in the intake stroke, which is longer than the compression stroke, from the injection of the fuel to the ignition. Therefore, the atomization time of the fuel is secured and the ignitability is improved.・ A mixture with rich combustibility is obtained, high output is obtained efficiently, unburned components are reduced, and exhaust emission is improved.

Since the injected fuel is carried out as it is into the exhaust gas and the fuel is injected in the exhaust stroke where the rate of outflow is the highest, the priority is set to the lowest. Therefore, when the entire amount of fuel can be injected only in the intake stroke and the compression stroke, , It is not necessary to inject fuel in the exhaust stroke, and even if it is necessary to inject fuel up to the exhaust stroke, only the minimum amount of unburned fuel remaining until the end is injected in the exhaust stroke. It suffices to do so (symbol E), which further suppresses the reduction of exhaust emission.

In addition, even when the first half of the intake stroke and the second half of the intake stroke are compared, the first half of the intake stroke, which has a longer time from injection of fuel to ignition, is prioritized over the latter half of the intake stroke. Securing and suppressing the reduction of exhaust emissions,
The effect is not impaired.

In step S6 as well as in step S4, the engine speed, load condition, engine water temperature, fuel pressure, elapsed time after starting, etc. are taken into consideration when setting the injection timing. As a result, for example, since the engine rotation speed is high, it may be more difficult to completely inject the fuel injection amount set in step S2 in the intake stroke. Further, since the load condition is high, it may happen that the fuel must be injected as early as possible before the ignition timing. Further, since the engine water temperature is low, it may happen that the fuel must be injected as early as possible before the ignition timing.
Further, since the fuel pressure is low, the pulse width for injecting the entire amount of fuel injection becomes long, and it may become more difficult to inject the entire amount of fuel injection set in step S2 in the intake stroke. Further, since the elapsed time after starting is short and the engine temperature has not risen so much, it may happen that the fuel must be injected as early as possible before the ignition timing.

In addition, in step S6, the pulse width is also increased / decreased according to the injection timing in consideration of the in-cylinder pressure, the fuel outflow to the exhaust gas, and the like.

Next, FIG. 6 is a flow chart showing a concrete example of the fuel injection control at the time of starting. This program is executed only when the engine 1 is started, and after this program, the program shifts to the above-described post-startup fuel injection control program. First,
In step S11, the engine speed, the load state (for example, the intake air amount), the engine cooling water temperature at startup, the fuel pressure at startup, etc. are detected as the current state quantities. Next, in step S12, as the operating state of the engine 1, the fuel injection amount is set according to the starting water temperature. At the same time, the pulse width (valve opening time) of the drive pulse signal for the injector 18 is determined so that the set fuel injection amount is fully injected. The pulse width is from the fuel supply system 20 to the injector 18
The pulse width becomes longer as the fuel pressure becomes lower, even if the fuel injection amount is the same, depending on the fuel pressure supplied to.

Next, in step S13, it is determined whether or not the starting water temperature is lower than or equal to a predetermined value, and if it is higher than the predetermined value, the process proceeds to step S14, and the injection timing is set normally as in step S4 described above. To do. That is, the intake valve 1
The injection timing is normally adjusted according to the engine rotation speed, the load state, the engine water temperature, the fuel pressure, etc. without performing the split injection of the fuel at the time when the lift amounts of 2 and 12 become the predetermined amount α or more. To set. Also, when the water temperature at startup is high to some extent, the injected fuel is
This is because even if the back surface of the fuel cell 2 or 12 collides with the back surface of the ignition plug 16 or bounces off the spark plug 16 (even if plug fogging occurs), the vaporization and atomization of the fuel is less likely to cause misfire or smolder.

Then, in step S15, injection control is executed to perform cranking. The fuel is injected exclusively in the intake stroke, sufficiently mixed with the intake air, and the combustion chamber 6 is filled with a homogeneous mixture rich in ignitability and combustibility.

On the other hand, when the starting water temperature is below the predetermined value in step S13, it is determined in step S16 whether or not the fuel supply system 20 is abnormal based on the starting fuel pressure. That is, it is determined whether or not the fuel supply system 20 (for example, the fuel pump 26 or 26 ′) has an abnormality / failure at the time of starting, and the fuel pressure for the injector 18 does not rise to a predetermined required pressure. As a result, if NO, the process proceeds to step S17 as it is, and if YES, step S18.
Then, the fuel injection amount is increased and corrected to ensure the startability, and then the process proceeds to step S19.

The steps S17 and S19 have almost the same contents except the priority order. In particular, step S17
Is almost the same as step S6 described above. That is,
The fuel injection timing is set by excluding the timing at which the lift amount of the intake valves 12, 12 becomes a predetermined amount α or more. As a result, it becomes difficult to completely inject the fuel only in the intake stroke, and the amount left uninjected will be injected in the other strokes. Therefore, the priority at that time is (1) the first half of the intake stroke, 2) The latter half of the intake stroke, (3) compression stroke, and (4) exhaust stroke.

As a result, as illustrated in FIGS. 5 (a) and 5 (b) described above, first, as much amount as possible is injected in the first half of the intake stroke (symbol A). Therefore, if there is a residual jet, then, as much as possible is jetted in the latter half of the intake stroke (reference numeral a). If there is still an unsprayed residue, then, as much as possible is sprayed in the compression stroke (symbol c). If there is still an unexhausted jet, then the remaining amount is jetted in the exhaust stroke (reference d).

As described above, first, the fuel is injected with the highest priority in the intake stroke, which is longer than the compression stroke, from the injection of the fuel to the ignition. Therefore, the atomization time of the fuel is secured and the ignitability is improved.・ A mixture rich in flammability is obtained, startability is secured, unburned components are reduced, and exhaust emission is improved.

Since the injected fuel is carried out as it is into the exhaust gas and the fuel is injected in the exhaust stroke in which the rate of outflow is the highest, the priority is set to the lowest. Therefore, when the entire amount of fuel can be injected only in the intake stroke and the compression stroke, , It is not necessary to inject fuel in the exhaust stroke, and even if it is necessary to inject fuel up to the exhaust stroke, only the minimum amount of unburned fuel remaining until the end is injected in the exhaust stroke. It suffices to do so (symbol E), which further suppresses the reduction of exhaust emission.

In addition, even when the first half of the intake stroke and the second half of the intake stroke are compared, the first half of the intake stroke, which has a longer time from fuel injection to ignition, is prioritized over the latter half of the intake stroke. The effects of securing, starting performance, and suppressing exhaust emission reduction are not impaired.

On the other hand, in step S19, the priority is set to (1) exhaust stroke, (2) intake stroke first half, (3) intake stroke latter half, and (4) compression stroke. As a result, FIG.
As illustrated in (a) and (b), first, as much amount as possible is injected in the exhaust stroke (reference numeral C). Therefore, if there is an unexhausted jet, then as much as possible is jetted in the first half of the intake stroke (reference numeral K). If there is still a jet remaining, then, as much as possible is jetted in the latter half of the intake stroke (reference numeral K). However, if there is a residual jet, then the remaining amount is jetted in the compression stroke (reference numeral K).

As described above, in the state where the fuel supply system 20 has an abnormality / fault when the engine is started and the fuel pressure does not rise, the atomization degree of the fuel spray is reduced, the vaporization and atomization is not promoted, and the combustion stability is improved. Is reduced. Therefore, if the fuel injection in the compression stroke in which the time until ignition is short and the atomization time is short is prioritized, the ignitability and combustibility of the air-fuel mixture are further deteriorated, and the engine 1 cannot be started successfully. In contrast,
In the exhaust stroke, the time until ignition is the longest and the atomization time can be sufficiently long as compared with other intake strokes and compression strokes. Further, since the intake stroke and the compression stroke are before ignition, while the exhaust stroke is after ignition, when fuel is injected in this exhaust stroke, combustion has already occurred and the temperature is rising. Therefore, even if the atomization degree of the fuel spray is reduced,
Evaporative atomization is accelerated by the high temperature and combustion stability is improved.

For this reason, when the fuel supply system 20 is abnormal at the start, the fuel injection in the exhaust stroke is given the highest priority and the compression stroke is given the lowest priority. This ensures the startability of the engine 1 even in the situation where the fuel pressure does not rise. As a result, the fuel injection is always performed in the exhaust stroke, but the amount of fuel outflow in the exhaust stroke is compensated by the increase correction.

In addition, even when the first half of the intake stroke and the latter half of the intake stroke are compared, the first half of the intake stroke, which has a longer time from fuel injection to ignition, is prioritized over the latter half of the intake stroke. The effects of securing, starting performance, and suppressing exhaust emission reduction are not impaired.

FIG. 7A illustrates the case where the start time of fuel injection (F) in the exhaust stroke is delayed somewhat. At this time, the end time of the fuel injection (X) in the compression stroke extends to the vicinity of the above-described injection possible limit time t4. In contrast,
FIG. 7B illustrates an example in which the start time of fuel injection (F) in the exhaust stroke is set as the exhaust bottom dead center. At this time, the end time of the fuel injection (X) in the compression stroke is the injection possible time limit t
It's well before 4.

As described above, in the engine 1, the fuel injection control operation is the fuel injection control operation when the engine water temperature is higher than the predetermined water temperature after the engine is started (step S4).
When the engine water temperature is lower than the predetermined water temperature after the engine is started (step S6), when the engine starting water temperature is higher than the predetermined water temperature (warm restart)
Fuel injection control operation (step S14), the engine starting water temperature is lower than the predetermined water temperature, and the fuel supply system 20
Injection control operation when the engine is normal (step S1
7), and the fuel injection control operation (step S19) when the engine starting water temperature is lower than the predetermined water temperature and the fuel supply system 20 is abnormal.

[0065]

As described above, according to the present invention, in a cylinder injection engine, fuel is spread over a plurality of strokes due to, for example, a long pulse width and a short injectable time. When fuel injection is performed, improved fuel injection timing is provided from the viewpoint of ensuring atomization time, improving exhaust emission, improving startability, and the like. INDUSTRIAL APPLICABILITY The present invention can be expected to be widely used in general in-cylinder injection engines in which fuel is directly injected into a combustion chamber.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an engine according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a fuel supply system of the engine.

FIG. 3 is a diagram illustrating a relationship between intake valve lift and fuel injection in an intake stroke of the engine.

FIG. 4 is a specific example 1 of fuel injection control after the engine is started.
It is a flowchart which shows an example.

FIG. 5 is a time chart in that case.

FIG. 6 is a specific example 1 of the fuel injection control at the time of starting the engine.
It is a flowchart which shows an example.

FIG. 7 is a time chart in that case.

[Explanation of symbols]

1 engine (in-cylinder injection type) 2 cylinder 5 piston 6 combustion chamber 10 intake port 12 intake valve 16 spark plug 18 injector (fuel injection valve) 20 fuel supply system (fuel supply means) 50 ECU (injection amount setting means, injection timing) Setting means, fuel injection control means, correction means) 53 Fuel pressure sensor (abnormality detection means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/22 335 F02D 41/22 335A 345 345 45/00 364 45/00 364Q F02M 45/02 F02M 45 / 02 51/00 51/00 A 69/04 69/04 P F02N 11/08 F02N 11/08 X (72) Inventor Hiromi Yoshioka 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Corporation (72) Inventor Kazuya Takagi 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture F-term in Mazda Co., Ltd. (reference) 3G066 AA02 AB02 BA08 BA32 CC31 CE22 DA04 DA06 DA09 DB01 DC05 DC09 DC11 DC18 DC24 3G084 BA15 BA28 CA01 DA09 DA10 EC02 FA07 FA10 FA29 FA38 3G301 HA01 HA04 HA13 JA21 KA01 LB04 MA19 PA01Z PB08Z PD04Z PE03Z PF03Z

Claims (4)

[Claims] 1. A fuel injection valve for directly injecting fuel into a combustion chamber, the injection amount setting means for setting the fuel injection amount based on the operating state of the engine, and the total fuel injection amount set by the setting means. Of an engine having injection timing setting means for setting fuel injection timing so that fuel is injected, and fuel injection control means for controlling the fuel injection valve so as to inject fuel at the fuel injection timing set by the setting means. A fuel injection timing control device, wherein the injection timing setting means is configured to set the fuel injection timing in accordance with the priority order of the intake stroke, compression stroke, and exhaust stroke. Control device. 2. The fuel injection valve is arranged at a position where the fuel collides with the intake valve when the fuel is injected at a time when the lift amount of the intake valve becomes equal to or more than a predetermined amount, and the injection timing setting means includes an intake stroke. The fuel injection timing is set according to the priority order of the first half of the intake stroke, the second half of the intake stroke, the compression stroke, and the exhaust stroke, with the fuel being divided and injected before and after the time when the lift amount of the intake valve exceeds a predetermined amount. 2. The fuel injection timing control device for the engine according to claim 1, wherein the fuel injection timing control device is configured to set. 3. A fuel supply means for supplying fuel to the fuel injection valve, an abnormality detection means for detecting an abnormality in which the pressure of the fuel supplied by the supply means to the fuel injection valve does not reach a predetermined value, and the detection means. When the above abnormality is detected, the fuel injection amount set by the injection amount setting means is increased and the correction means is provided, and the injection timing setting means, when the above abnormality is detected when the engine is started, the exhaust stroke. 3. The fuel injection timing is set according to the priority order of the intake stroke and the compression stroke.
The fuel injection timing control device for the engine according to. 4. The fuel injection valve is arranged at a position where the fuel collides with the intake valve when the fuel is injected at a time when the lift amount of the intake valve becomes equal to or more than a predetermined amount, and the injection timing setting means includes an intake stroke. The fuel is divided and injected before and after the time when the lift amount of the intake valve becomes a predetermined amount or more, and when the abnormality is detected by the abnormality detecting means at the time of starting the engine, the exhaust stroke, the intake 4. The fuel injection timing control device for an engine according to claim 3, wherein the fuel injection timing is set according to the priorities of the first half of the stroke, the second half of the intake stroke, and the compression stroke.