JP2656341B2 - Intake system for direct injection diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an intake device for a direct injection diesel engine.

(Prior Art) Conventionally, as described in, for example, JP-A-63-140820, an intake device of a direct injection type diesel engine is known.

In general, in a diesel engine, when the combustibility deteriorates, the amount of HC (smoke) generated increases due to incomplete combustion.
On the other hand, when the combustibility improves and the temperature of the combustion gas increases,
Although the amount of generated HC decreases, the amount of generated NO _X (nitrogen oxide) increases this time. Therefore, recently, the EGR for exhaust gas recirculation is installed separately from the main intake port in the combustion chamber of the above engine.
A sub-intake port connected to the passage is provided. For example, when the engine is running at low speed, the load (intake amount) at that time
Accordingly, a configuration is adopted in which the exhaust gas recirculation amount is increased as the load amount is smaller, and the intake air temperature is increased, thereby contributing to the improvement of ignitability.

(Problems to be Solved by the Invention) However, as in the above configuration, the recirculation amount of the exhaust gas is increased only at the time of low rotation, and the merit of the recirculation of the exhaust gas can be obtained in other operation regions. There is a problem that can not be. In addition, in the case of the same configuration, the NO _X can be reduced by increasing the recirculation amount (EGR amount) of the exhaust gas, which is the inert gas, from the sub-intake port. This involves problems such as deterioration and an increase in the amount of HC generated. Therefore, in the simple EGR control as described above, N
It was only possible to improve low-emission and low-efficiency exhaust emissions in a very restricted range determined by the balance between O _X reduction, fuel efficiency improvement and HC reduction.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems, and has a main intake port for introducing intake air so as to form an intake swirl in an engine combustion chamber;
In a direct injection diesel engine including an exhaust gas recirculation passage for introducing exhaust gas into the engine combustion chamber, in the exhaust gas recirculation region of the engine, hot EGR control is performed in a low load operation state, while high load side operation is performed. In this state, EGR control means for performing cold EGR control is provided.

(Operation) In the configuration of the intake device of the direct injection diesel engine of the present invention, the main intake port forming the intake swirl in the engine combustion chamber and the exhaust gas recirculation passage for introducing exhaust gas into the engine combustion chamber are provided. In the provided direct injection diesel engine, in the exhaust gas recirculation region of the engine, hot EGR control is performed in a low load operation state, and cold EGR control is performed in a high load side operation state.

Therefore, when the engine is in the low load operation range, the in-cylinder temperature is low, the ignitability
In a region where the generation amount of the exhaust gas increases, so-called hot EGR control is performed by the recirculation of the exhaust gas to increase the in-cylinder temperature to improve the ignitability and the combustibility. As a result, HC hardly occurs.

On the other hand, when the engine is in the high-load operation range,
Cold EGR effect is achieved by refluxing a low temperature exhaust gas becomes particularly so effectively reduce of the NO _X is achieved.

(Effects of the Invention) Therefore, according to the intake device for a direct injection diesel engine of the present invention, it is possible to realize appropriate swirl level control and EGR action in accordance with the operating state of the engine, and to improve the driving performance. The improvement of the fuel consumption will improve the fuel efficiency and contribute to the improvement of the exhaust emission.

(Embodiment) FIGS. 2 to 7 show a configuration of an intake device of a direct diesel engine according to a first embodiment of the present invention.

First, in FIG. 2, reference numeral 1 denotes an engine body,
The engine body 1 is constituted by an in-line four-cylinder engine having first to fourth four cylinders 2a to 2d. Each of the cylinders 2a to 2d has an exhaust port 3a to
A basic main intake port 4a to 4d having a 3d and swirl generation function is provided. The branch passages 5a to 5d of the intake manifold 5 are connected to the plurality of main intake ports 4a to 4d.
Are connected to each other, and are connected to the upstream-side intake passage 20 via the intake manifold 5. Also, the above exhaust port 3a
3b are connected to the branch passages 6a to 6d of the exhaust manifold 6, respectively.

The engine body 1 is, for example, as shown in FIG.
A cylinder block 7, a cylinder head 8, and a piston 9 fitted in the cylinder block 7;
A cavity 10 is formed on the top surface of the piston 9. In the cavity 10, for example, a fuel injection valve 11 of a hole nozzle type is arranged in a directional manner, and a direct injection fuel from the injection injection valve 11 spreads in a thin film shape on the peripheral wall surface of the cavity 10 and is burned. Formula (evaporation combustion formula)
Is configured as

Each of the above main intake ports 4a to 4d and exhaust ports 3a to
The main intake ports 4a to 4d are provided by intake valves 12a to 12d, and the exhaust ports 3a to 3d are provided by exhaust valves (not shown).
The openings are opened with well-known timings in synchronization with the rotation of a crankshaft (not shown). And the above main intake port
In the present embodiment, the helical ports 4a to 4d are, for example, helical ports as shown in FIG.
The intake air passing therethrough is supplied to the combustion chamber of each of the cylinders while being swirled in the direction of the arrow to form an intake swirl flow.

On the other hand, reference numerals 13a to 13d denote the main intake ports 4a to 4d, respectively.
Sub intake port for introducing intake in a direction to weaken the absorption swirl flow formed by the sub intake ports 13a to 13a
The upstream side of 3d is respectively connected to the exhaust manifold 6 and the fresh air supply passage 30 via the sub intake passage 17 respectively. A three-way solenoid valve 18 having an ON / OFF function is interposed at a portion of the auxiliary intake passage 17 where the exhaust manifold 6 and the fresh air supply passage 30 meet. A water supply passage 22 to which cooling water from a radiator provided on the side is supplied is communicated with a water injection valve 21 in the middle thereof. Then, fresh air or exhaust gas cooled by the water injected in a mist state by the water injection valve 21 is supplied to the sub intake ports 13a to 13d of the respective cylinders via the auxiliary intake passage 17. ing.

On the other hand, reference numeral 100 designates the three-way solenoid valve 19, the water injection valve 21 and the like according to the operating range of the engine as shown in FIG.
This is an engine control unit that performs swirl control with control contents as shown in the figure. The engine control unit 100 also includes engine speed detection data N _E from an engine speed sensor, accelerator opening detection data θ _ACC from an accelerator opening sensor, cooling water temperature detection data T _W from an engine cooling water temperature sensor, and the like. Are input at a predetermined cycle.

Next, the swirl level control by the engine control unit 100 will be described in detail with reference to the characteristic diagram of FIG. 6 and the flowchart of FIG.

First after performing the initialization of the control factors each unit, the engine speed N _E at step S _1, also each detects accelerator opening theta _ACC in step S _2, the one of FIG. 6 based on them After specifying the operation region, it is determined whether or not the current engine operation region is a control region in which the increased auxiliary intake passage 17 should be used. As a result, when it is determined that YES, further determines whether the hot EGR region proceeds to step S _4.

Consequently, YES (hot EGR region: low load) is as it is determined, evacuatable EGR by a three-way electromagnetic valve 18 of the auxiliary air intake passage 17 downstream end proceeds to step S ₅ to ON (open) after the state, the water injection valve 21 is turned OFF prohibiting the water injection proceeds further to step S _6.

As a result, a large amount of hot exhaust gas is introduced even in a low load region where the combustion temperature is low and there is a large amount of excess air not involved in the combustion. Is improved. As a result, the fuel efficiency is improved as well, NO _X is reduced by the so-called EGR effect (inert gas effect). In addition, the exhaust gas in the hot state is introduced in a direction in which the intake swirl formed by the main intake ports 4a to 4d is weakened, thereby improving the ignitability itself. Therefore, the amount of HC is reduced, the consumption rate of the fuel is also reduced can be from hydrogen, obtaining a combined NO _X reduction effect by the EGR effect (Seventh
See figure).

On the other hand, when the NO determination has been made, if not the auxiliary air intake passage control region in the step S _1, the auxiliary air intake passage the three-way solenoid valve 18 shifts toward the other side step S ₇ as OFF (closed) 17 is closed. As a result, in this case, hot EGR
Normal swirl operation is performed without performing both cold EGR and cold EGR.

Further, when even the auxiliary air intake passage control region not hot EGR region determined as NO in step S _4, the
Furthermore now proceeds to step S ₈ determines whether the cold EGR region (medium and high load region).

As a result, it is determined YES, and the above-described water injection valve in the next step S ₁₀ as to first open the auxiliary air intake passage 17 to the three-way solenoid valve 18 to ON (open) the flow proceeds to step S ₉ O
The so-called cold EGR is performed by lowering the temperature of the recirculated exhaust gas to N.

As a result, in this case, the exhaust gas whose temperature has decreased is introduced so as to obtain the maximum EGR effect in a state where the specific volume is small, and the combustion temperature is lower than that in a low load region such as a medium / high load operation state. It is suitable for effectively operating the EGR function in an operating range where the air flow is high and the amount of surplus air is small. Further, as a result, higher the NO _X reduction effect (see FIG. 8).

On the other hand, if the answer is NO if not cold EGR region determination in step S _8, the further step S
Proceeding to ₁₁ , it is determined whether or not it is in the cold air area.

Consequently, YES if the (cold air region), the three-way solenoid valve 18 a fresh air supply passage 30 proceeds to step S ₁₂
While forming the open to the side, the water injection valve at step S ₁₁ subsequent 21
Is turned on, water is injected into the supplied fresh air to lower the intake air temperature, and the fresh air that has been cooled to reduce the intake air temperature is supplied to the engine combustion chamber from the sub intake ports 13a to 13d.

On the other hand, if NO determination, if not the cold air region at the step S ₁₁ is performed, the opening and to have fresh air advances the three-way solenoid valve 18 to the fresh air supply passage 30 side is toward the step S ₁₄ while allowing the supply, to achieve a normal fresh air supply state of the by OFF the water injection valve 21 in step S _15.

[Brief description of the drawings]

1 is a diagram corresponding to claims of the present invention, FIG. 2 is a schematic diagram showing a system configuration of an intake device of a direct injection diesel engine according to an embodiment of the present invention, FIGS.
The figure is an enlarged sectional view of a main part of the intake device, and FIG.
FIG. 6 is a flow chart showing the braking operation of the device, FIG. 6 is a graph showing a control region in the embodiment, FIG. 7 is a graph showing a hot EGR effect in a low load region in the embodiment, FIG. Means cold EGR in the medium and high load area
It is a graph which shows an effect. 1. Engine body 2a to 2d First to fourth cylinders 3a to 3d Exhaust ports 4a to 4d Main intake port 5 Intake manifold 7 Cylinder block 8 Cylinder head 9 Piston 11 Fuel injectors 13a to 13d Sub intake port 17 EGR passage 18 Three-way solenoid valve 21 Water injection valve 30 Fresh air supply passage 100 Engine control unit

Claims (1)

(57) [Claims] 1. A direct injection diesel engine comprising a main intake port for introducing intake air so as to form an intake swirl in an engine combustion chamber, and an exhaust gas recirculation passage for introducing exhaust gas into the engine combustion chamber. ,
In the exhaust gas recirculation region of the engine, an intake device for a direct injection diesel engine characterized in that EGR control means for performing hot EGR control in a low load operation state and performing cold EGR control in a high load operation state is provided. .