JP2003227369A - Control device for direct injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly change the control state of combustion according to the operation state without causing unstable engine rotation. <P>SOLUTION: A direct ignition engine is constituted so that it changes to a first combustion state which performs one time of combustion between an intake stroke and an exhaust stroke, and to a second combustion state which performs two times of combustion between the intake stroke and the exhaust stroke by switching a combustion cycle according to the operation state of the engine. The combustion control of 8 cycles is performed in the second combustion state. The combustion control of 8 cycles consists of the intake stroke, a first compression stroke, a first expansion stroke accompanied by combustion, a second compression stroke, a second expansion stroke without combustion, a third compression stroke, a third expansion stroke accompanied by combustion and the 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 a control system for a direct injection engine that directly injects fuel into a combustion chamber for combustion.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 2001-33643.
As disclosed in Japanese Patent Publication No. 5, the intake / exhaust system is designed to operate the engine efficiently and improve fuel consumption performance and exhaust gas performance while simplifying the supply / exhaust system structure and engine control to suppress cost increase. In an engine that sequentially executes a stroke, a first compression stroke, a first expansion stroke, a second compression stroke, a second expansion stroke, and an exhaust stroke, the fuel is passed through the intake stroke, the first compression stroke, and the first expansion stroke to obtain a lean air-fuel ratio. And a second combustion process in which the additional fuel is injected into the burnt gas generated in the first combustion process
A 6-cycle combustion control (see FIG. 5 (b)) including a second combustion process in which the additional fuel is burned through a compression stroke and a second expansion stroke is realized, and a general combustion control is performed according to the operating state of the engine. Engines are known that are configured to perform even four-cycle combustion control.

[0003]

As shown in FIG. 5 (a), in the engine that realizes the above-described 6-cycle combustion control, the intake stroke IN, the compression stroke involving the fuel injection F and the ignition S, and the compression stroke are performed. , Expansion stroke with combustion and exhaust stroke EX
The pumping loss can be reduced to 2/3 compared to the general 4-cycle combustion state consisting of
By re-reacting the unburned gas generated in the first combustion process in the second combustion process, there is an advantage that the emission of HC and NOx can be effectively suppressed.

On the other hand, in the four-cycle combustion state shown in FIG. 5 (a), at the time of the intake stroke IN, FIG.
As shown in (1), the second expansion stroke (fifth stroke) accompanied by combustion is executed, so that there is a problem that instability of the engine rotation due to deviation of the explosion interval cannot be avoided. . That is, in a multi-cylinder engine having a plurality of cylinders, the explosion timing of each cylinder is preset with a predetermined phase difference so that the engine rotation is stable,
If the explosion timing changes in accordance with the operating state of the engine, there is a problem that the engine is in a biased rotating state due to continuous explosion of adjacent cylinders.

The present invention has been made in consideration of the conventional problems as described above, and the combustion control state can be properly adjusted according to the operating state without causing the situation that the rotation of the engine becomes unstable. A controller for a direct injection engine that can be changed.

[0006]

The invention according to claim 1 is
By directly injecting fuel into the combustion chamber and switching the combustion cycle according to the operating state of the engine,
It is configured to change into a first combustion state in which one combustion is performed between the intake stroke and the exhaust stroke, and a second combustion state in which two combustions are performed between the intake stroke and the exhaust stroke. In the direct injection engine, in the second combustion state, the intake stroke, the first compression stroke, the first expansion stroke with combustion, and the second
Eight-cycle combustion control including a compression stroke, a second expansion stroke without combustion, a third compression stroke, a third expansion stroke with combustion, and an exhaust stroke is executed.

According to this configuration, for example, in a low load / low speed operation region, by executing the combustion control for 8 cycles as the second combustion state, the pumping loss is reduced and the fuel consumption improving effect is obtained. At the time of shifting to the high load / high speed operation region, the second combustion state is switched to the first combustion state for executing four-cycle combustion control without causing a problem such as a shift in the explosion timing. It will be.

According to a second aspect of the present invention, in the control device for a direct injection engine according to the first aspect, in the second combustion state, the burned gas concentration discharged to the exhaust passage is a combustion state having a substantially stoichiometric air-fuel ratio. The intake air amount and the fuel injection amount are controlled so that the values correspond to the above.

According to the above construction, in the first expansion stroke in the second combustion state in which the combustion control of eight cycles is executed, the combustion is performed with a lean air-fuel ratio, so that the thermal efficiency is increased and the third expansion is performed. In the stroke, a large amount of burned gas is present in the cylinder, and the combustion state is equivalent to that in which a large amount of EGR is performed. Therefore, the generation of NOx is sufficiently suppressed, which is advantageous for improving emission. Becomes

According to a third aspect of the present invention, in the control device for a direct injection engine according to the second aspect, the fuel injection amount injected before the first expansion stroke in the second combustion state is set to the third expansion stroke. It is set to a value smaller than the injection amount of the fuel injected before.

According to the above configuration, in the first expansion stroke in the second combustion state in which the eight-cycle combustion control is executed, combustion is performed with a leaner air-fuel ratio, and a remarkable fuel consumption improving effect is obtained. By performing combustion in the third expansion stroke in a state where an appropriate amount of burned gas and excess air exist in the cylinder, it is possible to effectively suppress the generation of NOx while ensuring combustibility. Become.

According to a fourth aspect of the present invention, in the control device for a direct injection engine according to any one of the first to third aspects, in the high load / high speed operation region, the first combustion state is set, and The intake air amount and the fuel injection amount are controlled so that the air-fuel ratio in the cylinder is λ ≦ 1.

According to the above construction, in the high load / high speed operation region where high output is required, the first combustion state is performed in which only one combustion is performed using the fresh air supplied into the cylinder. As a result, the required engine output is obtained, and the intake air amount and the fuel injection amount are controlled so that the air-fuel ratio in the cylinder is λ ≦ 1, thereby suppressing the generation of NOx. Become.

According to a fifth aspect of the present invention, in the control device for a direct injection engine according to any one of the first to fourth aspects, an electromagnetic valve mechanism for driving an intake valve and an exhaust valve is provided, and this solenoid valve is operated. By changing the output timing of the control signal output to the mechanism, the first combustion state and the second combustion state are switched.

According to the above configuration, the combustion cycle can be switched between the first combustion state in which the 4-cycle combustion control is executed and the second combustion state in which the 8-cycle combustion control is executed with a simple structure. It becomes possible to execute properly.

[0016]

1 and 2 schematically show the structure of an engine according to an embodiment of the present invention. In these figures, the engine body 1 has a plurality of cylinders, and in the illustrated embodiment, has four cylinders 2. A piston 3 is fitted into each cylinder 2 and a combustion chamber 4 is formed above the piston 3. Further, a spark plug 7 is provided at the top of the combustion chamber 4 of each cylinder 2, and the tip end thereof faces the inside of the combustion chamber 4. The spark plug 7 has an ignition circuit 8 capable of electronically controlling the ignition timing.
Are connected.

A fuel injection valve 9 for directly injecting fuel into the combustion chamber 4 is provided at a side portion of the combustion chamber 4. The fuel injection valve 9 has a needle valve and a solenoid (not shown) built therein, and when a pulse signal described later is input, the fuel injection valve 9 is driven for a time corresponding to the pulse width at the input timing of the pulse to open the valve. It is configured to inject an amount of fuel according to the valve opening time. In addition, the fuel injection valve 9 has
A fuel pump (not shown) supplies fuel through a fuel supply passage or the like, and the fuel supply system is configured so that a fuel pressure higher than the pressure in the combustion chamber 4 in the compression stroke can be applied.

A pair of intake ports 11, 11 and an exhaust port 12, respectively, are provided for the combustion chamber 4 of each cylinder 2.
12 open and these ports 11, 11, 12, 12
Is connected to the intake passage 15, the exhaust passage 20, etc., and the ports 11, 11, 12, 12 are connected to the intake valves 31, 3 respectively.
1 and the exhaust valves 32, 32. Then, in the case where each cylinder 2 has a predetermined phase difference, that is, in the case of a 4-cylinder engine, combustion is performed in a predetermined order with a phase difference of 180 ° in crank angle.

Branch exhaust passage 2 in the exhaust passage 20
An O ₂ sensor 23 (exhaust gas concentration detecting means for detecting a theoretical air-fuel ratio) is provided at a collecting portion downstream of 1, and a three-way catalyst 24 for exhaust purification is provided further downstream thereof. The three-way catalyst 24, as is generally known,
This catalyst exhibits high purification performance for HC, CO and NOx when the air-fuel ratio of the exhaust gas is near the stoichiometric air-fuel ratio (that is, the excess air ratio λ is λ = 1). Above O ₂ sensor 2
3 detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas, and is composed of a λO ₂ sensor whose output changes rapidly near the stoichiometric air-fuel ratio.

The intake / exhaust valves 31, 32 are configured to be driven by a valve operating mechanism 33, respectively. As shown in FIG. 3, the valve operating mechanism 33 is provided with a housing 34 made of a non-magnetic material, slidably disposed in the housing 34, and integrally connected to the intake / exhaust valves 31, 32. Armature core 35, and a pair of electromagnets 36 arranged at both upper and lower ends in the housing 34,
37 and return springs 38, 39. Then, the upper electromagnet 36 is energized and the armature core 3 is energized.
5 is sucked upward to open the intake valve 31 and the exhaust valve 32 at predetermined timings, and the lower electromagnet 37 is energized to suck the armature core 35 downward to suck the intake valve 31 and the exhaust valve 32. Exhaust valve 32
Are closed at predetermined timings.

An air flow sensor 19, O is provided in an engine control ECU (control unit) 40 including a microcomputer for controlling the valve operating mechanism 33 and the like.
Signals from the ₂ sensor 23 and the linear O ₂ sensor 25 are input, and further, a rotation speed sensor 45 for detecting the engine speed and an accelerator opening for detecting the accelerator opening (accelerator pedal depression amount) to determine the operating state. Signals from the sensor 46 and the like are also input.

The ECU 40 has an operating condition discriminating means 4
1, a valve opening / closing control unit 42, an intake air amount control unit 43, and a fuel injection control unit 44. The operating state determination means 41 checks the operating state (engine rotational speed and engine load) of the engine based on signals from the rotational speed sensor 45, the accelerator opening sensor 46, etc., and the operating state is low load as shown in FIG. It is configured to determine which one of the low-rotation side operating region A and the high-load side or high-rotation side operating region B.

The valve opening / closing control means 42 operates depending on whether the operating state is in the low load or low rotation side operating range A or in the high load side or high rotation side operating range B. Is configured to control the opening / closing timing of the intake valve 31 and the exhaust valve 32 as follows by changing the output timing of the control signal output to.

In the operating region B on the high load side or the high rotation side, as shown in FIG. 5 (a), an intake stroke IN accompanied by fuel injection (broken line F), a compression stroke accompanied by ignition S in the latter period, and combustion. The first combustion state consisting of the expansion stroke accompanied by the exhaust stroke EX and the exhaust stroke EX, that is, the above-mentioned four-cycle combustion control in which one combustion is performed between the intake stroke IN and the exhaust stroke EX is executed. The opening / closing timing of the intake valve 31 and the exhaust valve 32 is set. In FIG. 5, T is the top dead center of the piston stroke, and B is the bottom dead center.

In the operating region A on the low load side or the low rotation side, as shown in FIG. 5 (c), the intake stroke IN (first stroke) and the first compression stroke accompanied by fuel injection F and ignition S in the latter period. (Second stroke), first expansion stroke with combustion (third stroke), second compression stroke (fourth stroke), second expansion stroke without combustion (fifth stroke), and fuel in the latter period A second combustion state consisting of a third compression stroke (sixth stroke) with injection F and ignition S, a third expansion stroke (seventh stroke) with combustion, and an exhaust stroke EX (eighth stroke), that is, The intake valve 31 and the exhaust valve 3 are arranged so as to perform 8-cycle combustion control in which combustion is performed twice between the intake stroke IN and the exhaust stroke EX.
The opening / closing timing of 2 is set.

The intake air amount control means 43 controls the opening of the throttle valve 17 (throttle opening) by controlling the actuator 18, and a target corresponding to the operating state is set from a preset map or the like. The intake air amount is obtained, and the throttle opening is controlled according to the target intake air amount to control the intake air amount.

That is, the operating region A on the low load / low rotation side
In the second combustion state executed in step S1, the throttle opening is adjusted so that the burnt gas concentration of the exhaust gas discharged into the exhaust passage 20 in the exhaust stroke EX becomes a value corresponding to the combustion state of substantially the theoretical air-fuel ratio. Is adjusted. Further, in the first combustion state executed in the operating region B on the high load / high rotation side, the throttle opening is adjusted so that the air-fuel ratio in the cylinder 2 becomes λ ≦ 1.

The fuel injection control means 44 controls the fuel injection amount and injection timing from the fuel injection valve 9 provided in each cylinder 2 in accordance with the operating condition of the engine. In the operating area A of
It is configured to change the control state of fuel injection depending on whether it is in the operating region B or not.

That is, the operating region A on the low load / low rotation side
In the second combustion state executed in step S1, the air-fuel ratio is stoichiometric so that the first combustion performed in the first expansion stroke (third stroke) becomes the stratified combustion state, as shown in FIG. 5 (c). The fuel injection amount and injection timing of the first compression stroke (second stroke) are set so that the lean air-fuel ratio is larger than the fuel ratio, preferably about twice the stoichiometric air-fuel ratio or more. Further, by supplying the fuel into the burnt gas having the lean air-fuel ratio generated by the first combustion, the second combustion is performed in the third expansion stroke (seventh stroke) under the condition of the stoichiometric air-fuel ratio. In addition to controlling the fuel injection amount, the injection timing is set so that ignition and combustion can be performed in a situation where there is a large amount of burned gas. For example, in order to secure ignitability, the fuel is injected in the third compression stroke (sixth stroke). Is jetted.

The control of the fuel injection amount is performed by feedback control based on the outputs from the air flow sensor 19, the O ₂ sensor 23 and the like.

On the other hand, when the operating state is in the operating region B on the high load side or the high rotation side, the fuel injection amount is controlled so that the air-fuel ratio of each cylinder 2 becomes the stoichiometric air-fuel ratio or less, for example, The stoichiometric air-fuel ratio is set in most of the operating range B, and is richer than the stoichiometric air-fuel ratio in the full-open load and the operating range in the vicinity thereof. And in this case, FIG.
As shown by the broken line in (a), the injection timing is set so that uniform combustion is performed by injecting fuel into each cylinder 2 in the intake stroke IN (first stroke).

As described above, when the operating condition is in the operating region A on the low load side or the low rotating side, the second combustion state is set in which the combustion is performed twice between the intake stroke and the exhaust stroke. By making the first combustion performed in one expansion stroke a stratified combustion state with a lean air-fuel ratio, the thermal efficiency is increased and the pumping loss is reduced, and the fuel efficiency is greatly improved by these synergistic effects. Further, by supplying the fuel into the burnt gas in the air excess state generated by the first combustion to control the stoichiometric air-fuel ratio and performing the second combustion in the third expansion stroke, a normal engine is provided. Although the thermal efficiency is inferior to the one in which the stratified charge combustion is performed with the lean air-fuel ratio as described above, the fuel consumption effect can be obtained by reducing the pumping loss.

Moreover, after the second combustion is performed, the concentration of the burnt gas discharged into the exhaust passage 20 in the discharge stroke becomes a value corresponding to the stoichiometric air-fuel ratio. Lean N like a lean burn engine
It is not necessary to provide an Ox catalyst, and the three-way catalyst 24 alone ensures sufficient exhaust gas purification performance. Lean N like this
Since it is not necessary to provide an Ox catalyst, it is not necessary to release the NOx when the NOx storage amount of the lean NOx catalyst increases, and to temporarily enrich the air-fuel ratio for reduction.
A reduction in fuel consumption can be avoided. Furthermore, lean NOx
There is no problem of sulfur poisoning of the catalyst.

Then, as described above, the first combustion state in which one combustion is performed between the intake stroke and the exhaust stroke, and the second combustion state in which two combustions are performed between the intake stroke and the exhaust stroke. State, the combustion cycle is switched according to the operating state of the engine, and in the second combustion state, the intake stroke, the first compression stroke, the first expansion stroke with combustion, and the second stroke
According to the configuration in which the combustion control of eight cycles including the compression stroke, the second expansion stroke without combustion, the third compression stroke, the third expansion stroke with combustion, and the exhaust stroke is executed, an explosion occurs. The operating state is switched between the second combustion state where the pumping loss is reduced and the fuel consumption improving effect is obtained and the first combustion state where a high output is obtained without causing a problem such as a time shift. be able to.

That is, the second expansion stroke (seventh stroke) accompanying combustion in the first combustion state shown in FIG. 5 (a).
And the third expansion stroke (seventh stroke) accompanied by combustion in the second combustion state shown in FIG. 5 (c) are at the same time, and therefore, as shown in FIG. 5 (b), combustion control of 6 cycles is performed. There is no possibility that the rotation of the engine becomes unstable due to the shift of the explosion timing as in the case of executing the. It is possible to smoothly shift to the combustion control state.

In the above embodiment, in the second combustion state, the concentration of burnt gas discharged into the exhaust passage 20 is
Since the intake air amount and the fuel injection amount are controlled so as to be values corresponding to the combustion state of the substantially stoichiometric air-fuel ratio, in the first expansion stroke in the second combustion state in which the combustion control of 8 cycles is executed, Since the first stratified charge combustion is performed with a lean air-fuel ratio, the thermal efficiency is increased and the fuel consumption improving effect is obtained. Moreover, in the third expansion stroke,
Since the second combustion is performed in the state where a large amount of burned gas is present in the cylinder 2, the same effect as that of a large amount of EGR is obtained, and the generation of NOx is sufficiently suppressed. Emission can be effectively improved.

That is, since the first combustion in the second combustion state is performed with a lean air-fuel ratio that is approximately twice the stoichiometric air-fuel ratio or more, the NOx generation amount is suppressed to a relatively small amount and the second combustion is performed. Occasionally, burned gas is generated at the time of the first combustion, and the state is equivalent to that in which a large amount of EGR is performed, so that the generation of NOx is sufficiently suppressed. From this point as well, it is advantageous for improving emission.

In the second combustion state, the intake air amount and the fuel injection amount are controlled so that the concentration of the burnt gas discharged into the exhaust passage 20 becomes a value corresponding to the combustion state of substantially stoichiometric air-fuel ratio. In addition, it is preferable to set the fuel injection amount injected before the first expansion stroke in the second combustion state to a value smaller than the injection amount of fuel injected before the third expansion stroke. In the case of such a configuration, by performing the first combustion with a leaner air-fuel ratio in the first expansion stroke in the second combustion state in which the combustion control of eight cycles is executed, a remarkable fuel consumption improvement effect is achieved. As well as
Since an appropriate amount of oxygen can be left in the burnt gas generated during the first combustion, the combustion stability during the second combustion can be ensured.

Further, as shown in the above embodiment, in the high load / high speed operation region B, the first combustion state (four-cycle state) is set and the air-fuel ratio in the cylinder 2 becomes λ ≦ 1. When the intake air amount and the fuel injection amount are controlled as described above, the uniform combustion control using the fresh air supplied into the cylinder 2 is executed, so that the high load
It is possible to sufficiently secure the required engine output in the high rotation speed operation range B and to effectively suppress the generation of NOx.

Further, in the above embodiment, the electromagnetic valve mechanism 33 for driving the intake valve 31 and the exhaust valve 32 is provided, and the operating state of the electromagnetic valve mechanism 33 is controlled by the valve opening / closing control means 42.
The first combustion state and the second combustion state are switched by controlling the first combustion state and the second combustion state. Therefore, the first combustion state in which the 4-cycle combustion control is executed and the first combustion state in which the 8-cycle combustion control is executed. It is possible to properly execute the two combustion states with a simple configuration.

That is, instead of the electromagnetic valve mechanism 33, the intake / exhaust valve 31 and the exhaust valve 32 are switched between an operating state and a stopped state by controlling the supply / discharge state of hydraulic oil to / from the hydraulic chamber. A valve stop mechanism is provided between the camshaft and the valve shafts of the intake valve 31 and the exhaust valve 32, and in the second combustion state, the intake valve 3 is operated by the valve stop mechanism.
It is also possible to execute the combustion control for eight cycles by stopping the opening operation of the exhaust valve 32 and the exhaust valve 32 each time and maintaining the closed state. However, as described above, when the supply / discharge state of the hydraulic oil to / from the hydraulic chamber is controlled to stop the opening operation of the intake valve 31 and the exhaust valve 32 each time, the camshaft rotating at a high speed. Since it is necessary to frequently repeat the supply and discharge of the hydraulic oil in accordance with the rotation state of No. 3, there is a problem in the followability.

On the other hand, as shown in the above embodiment,
The electromagnetic valve mechanism 33 allows the intake valve 31 and the exhaust valve 32.
When it is configured to drive the first combustion state and the second combustion state, it is only necessary to change the output timing of the control signal output from the valve opening / closing control means 42 to the electromagnetic valve mechanism 33. There is an advantage that and can be switched easily and properly.

In the above embodiment, as shown in FIG. 5C, the fuel injection timing for performing the second combustion in the second combustion state is set to the third compression stroke (sixth stroke). By doing so, the stratified charge combustion is performed at the stoichiometric air-fuel ratio, but as shown in FIG. 6A, the second expansion stroke (fifth stroke) and the third compression stroke (sixth stroke) are performed. Of 2
The divided injections (F1, F2) may be performed separately. In this way, fuel is prevented from collecting too much near the spark plug, and combustion is performed in a weakly stratified state.

Further, in the case where the ignitability can be ensured even if the fuel for the second time is evenly dispersed because the temperature of the burnt gas generated during the first combustion is sufficiently high, etc., as shown in FIG.
As shown in (b), the fuel may be collectively injected in the second expansion stroke (fifth stroke). In the case of such a configuration, there is an advantage that the fuel injected in the second expansion stroke can be appropriately burned in the state of being sufficiently agitated and mixed with the air in the cylinder 2 in the third compression stroke or the like. is there.

Further, when the temperature in the cylinder 2 is sufficiently increased by the first combustion in the second combustion state and the self-ignition is likely to occur in the third compression stroke (sixth stroke), the above-mentioned first Ignition S in the third compression stroke may be omitted, and the second combustion may be performed by self-ignition.

In addition to the structure shown in the above embodiment, a structure provided with a supercharger may be adopted. For example, as shown in FIG. 7, a turbine 61 provided in the exhaust passage 20,
A turbocharger 60 having a compressor 62 provided in the intake passage 15 is provided, and the compressor 62 is rotated in response to the turbine 61 being rotated by the energy of the exhaust gas flowing in the exhaust passage 20, thereby making the intake air intake May be supercharged. According to this structure, due to the above supercharging action, it is
There is an advantage that the fuel consumption can be further improved as the second combustion state in which the cycle combustion control is executed. In FIG. 7, 63 is an intercooler provided in the intake passage 15 on the downstream side of the compressor 62.

[0047]

As described above, the control device of the present invention switches the combustion cycle in accordance with the operating state of the engine, thereby performing the first combustion state in which one combustion is performed between the intake stroke and the exhaust stroke. And a direct injection engine configured to change to a second combustion state in which combustion is performed twice between the intake stroke and the exhaust stroke, in the second combustion state,
An intake stroke, a first compression stroke, a first expansion stroke with combustion, a second compression stroke, and a second expansion stroke without combustion,
Since the combustion control of eight cycles including the third compression stroke, the third expansion stroke accompanied by combustion, and the exhaust stroke is configured to be performed, pumping loss is reduced without causing a problem such as a shift in the explosion timing. Therefore, there is an advantage that the operating state can be switched between the second combustion state where the fuel consumption improving effect is obtained and the first combustion state where the high output is obtained.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an entire engine equipped with a device according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of an engine body and the like.

FIG. 3 is an explanatory diagram showing operating regions.

FIG. 4 is a block diagram of a control system.

FIG. 5 is an explanatory diagram showing a combustion cycle of a cylinder, a fuel injection timing, and an ignition timing.

FIG. 6 is an explanatory diagram showing another specific example of the combustion cycle.

FIG. 7 is a schematic plan view of the entire engine showing an example including a supercharger.

[Explanation of symbols]

1 engine body Two cylinder 4 Combustion chamber 9 Fuel injection valve 20 exhaust passage 31 intake valve 32 exhaust valve 33 Electromagnetic valve mechanism 40 ECU 41 Operating state determination means 42 Valve opening / closing control means 43 Intake air amount control means 44 Fuel injection control means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/04 310 F02D 41/04 310D 320 320 330 330 330D 43/00 301 43/00 301E 301Z 45/00 312 45/00 312K F Term (Reference) 3G018 AA01 AB09 BA38 CA12 EA03 EA04 EA13 EA14 EA16 EA35 FA07 FA26 GA07 GA09 3G084 AA01 AA04 BA04 BA05 BA07 BA09 BA13 BA15 BA23 CA03 CA04 CA09 DA02 DA10 EB11 FA11 A18 A09 A02 A09 A02 A09 A29 A02 A09 A02 A09 A29 A02 A02 A09 A02 A09 A02 A02 A09 A02 BB06 DG09 EA05 EA06 EA07 EA11 EC01 FA17 FA24 GA05 GA06 GA17 GA18 HA01Z HD05Z HE01Z HF08Z 3G301 HA00 HA02 HA11 HA16 HA19 JA02 JA25 KA08 KA09 KA24 KA25 LA03 LA07 LC01 MA01 MA11 MA19 ND01 NE13 PD03 PE01 PE14 NE15 PA01

Claims (5)

[Claims] 1. A first combustion state in which fuel is directly injected into a combustion chamber and a combustion cycle is switched according to an operating state of an engine to perform one combustion between an intake stroke and an exhaust stroke. , A direct injection engine configured to change to a second combustion state in which combustion is performed twice between the intake stroke and the exhaust stroke, the intake stroke and the first compression state in the second combustion state. First with stroke and combustion
An expansion stroke, a second compression stroke, a second expansion stroke without combustion, a third compression stroke, and a third expansion stroke with combustion,
A control device for a direct injection engine, which performs combustion control of eight cycles including an exhaust stroke. 2. In the second combustion state, the intake air amount and the fuel injection amount are controlled so that the concentration of burnt gas discharged to the exhaust passage becomes a value corresponding to the combustion state of a substantially stoichiometric air-fuel ratio. The control device for a direct injection engine according to claim 1. 3. The fuel injection amount injected before the first expansion stroke in the second combustion state is set to a value smaller than the injection amount of fuel injected before the third expansion stroke. The control device for a direct injection engine according to claim 2. 4. In a high load / high rotation operating range, the intake air amount and the fuel injection amount are controlled such that the first combustion state is achieved and the air-fuel ratio in the cylinder is λ ≦ 1. The control device for a direct injection engine according to any one of claims 1 to 3. 5. An electromagnetic valve mechanism for driving an intake valve and an exhaust valve is provided, and by changing the output timing of a control signal output to this electromagnetic valve mechanism, the first combustion state and the second combustion state can be obtained. The control device for a direct injection engine according to any one of claims 1 to 4, wherein the control device switches between a combustion state and a combustion state.