JP4092482B2 - Direct-injection spark ignition internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
Conventionally, in a direct-injection spark-ignition internal combustion engine, as shown in Patent Document 1, a fuel is injected from a fuel injection valve disposed at a side portion of a combustion chamber to a combustion chamber center side through two intake valves. Is sprayed.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-294208
[Problems to be solved by the invention]
However, in the stratified operation mode in which fuel injection is performed in the compression stroke, in the homogeneous operation mode in which fuel injection is performed in the intake stroke, since the intake valve is lifted, a part of the injected fuel interferes with the intake valve. By doing so, as a result of inhibiting mixture formation in the cylinder, a large amount of liquid fuel is present in the cylinder.
[0005]
In particular, when the engine is cold, the intake valve temperature and the ambient temperature are low, so liquid fuel adhering to the intake valve or the like is discharged from the exhaust valve without contributing to combustion, and unburned fuel (HC) discharged from the engine. ) Has increased.
[0006]
The present invention has been made in view of such conventional problems, and an object of the present invention is to reduce the amount of unburned fuel by reducing fuel spray that interferes with an intake valve during cold operation.
[0007]
[Means for Solving the Problems]
For this reason, the present invention uses a variable valve system that can stop one intake valve in a closed state, and closes one intake valve in an operation mode in which fuel injection is performed during the intake stroke and when the engine is cold. It is set as the structure which performs the single valve stop stopped in a valve state.
In addition, an air motion device for enhancing in-cylinder flow, particularly tumble flow, is used, and when the one-valve stop is performed, the air motion device is operated to enhance the in-cylinder tumble flow.
[0008]
【The invention's effect】
According to the present invention, since the fuel spray does not interfere with one of the intake valves by stopping the one valve when the engine is cold, the fuel spray interferes with one intake valve and the fuel spray interferes with the intake valve. Therefore, the amount of unburned fuel can be greatly reduced.
In the one-valve stop state, the air motion valve is used to enhance the tumble flow in the cylinder, thereby promoting fuel vaporization and further reducing the amount of unburned fuel discharged.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan layout view of an internal combustion engine showing an embodiment of the present invention, and FIG.
[0010]
In the combustion chamber 1 of the internal combustion engine, a spark plug 2 is disposed at a substantially central portion on the upper surface (cylinder head) side. Then, two intake ports 3A and 3B and two exhaust ports 4A and 4B are opened so as to surround the spark plug 2, and the intake valves 5A and 5B and the exhaust valves 6A and 6B are mounted respectively.
[0011]
The fuel injection valve 7 is disposed obliquely downward (inclined by a predetermined angle θ with respect to a plane perpendicular to the cylinder axis) on the side of the combustion chamber 1 on the side of the intake valves 5A and 5B. Fuel is injected into the center of the combustion chamber 1 through the space between 5A and 5B.
[0012]
Further, as an air motion device for enhancing the in-cylinder flow, as shown in FIG. 2, the intake ports 3A and 3B are divided into upper and lower divided ports by the partition plate 8, and then the upstream side of the lower divided port. In addition, a control valve 9 capable of closing the valve is provided, and when the control valve 9 is closed, the in-cylinder flow, particularly the tumble flow, can be enhanced by sucking only from the upper divided port. Therefore, the control valve 9 is referred to as a tumble control valve (TCV).
[0013]
The operation mode of the internal combustion engine includes a stratified operation mode and a homogeneous operation mode. In the stratified operation mode, fuel injection is performed in the compression stroke, and a stratified mixture is formed around the spark plug 2. As a result, stratified combustion is performed at a very lean air-fuel ratio as a whole. On the other hand, in the homogeneous operation mode, fuel injection is performed in the intake stroke, and a homogeneous air-fuel mixture is formed in the entire combustion chamber 1, thereby performing homogeneous combustion at a stoichiometric or lean air-fuel ratio.
[0014]
Here, in the case of the compression stroke injection, since the intake valves 5A and 5B are closed, the interference between the fuel spray and the intake valves 5A and 5B does not matter, but in the case of the intake stroke injection, the intake valves 5A and 5B. Therefore, the interference between the fuel spray and the intake valves 5A and 5B becomes a problem.
[0015]
In addition, after the warm-up, even if the fuel spray interferes with the intake valves 5A and 5B, the intake valve temperature and the atmospheric temperature are high and the vaporization property is good, so that there is not much trouble in the mixture formation (HC emission) Therefore, interference between the fuel spray and the intake valves 5A and 5B becomes a problem.
[0016]
Therefore, in the present invention, as shown in FIG. 2, in the operation mode (homogeneous operation mode) in which fuel injection is performed in the intake stroke, and when the engine is cold, one intake valve 5A is closed (zero lift or minute). The single valve is stopped by the lift), and the engine is operated by the opening / closing operation of only the other intake valve 5B.
[0017]
Thus, during the intake stroke injection, the fuel spray does not interfere with the intake valve 5A but interferes with only the intake valve 5B, and the spray adheres only to the intake valve 5B (see FIG. 2). Therefore, the fuel spray interference amount (attachment amount) is simply halved, and the amount of unburned fuel (HC) discharged during cold operation can be greatly reduced.
[0018]
However, if the single valve is stopped, the maximum amount of air that can be sucked is restricted, so the single valve is stopped when the required air amount is relatively low and in a low rotation / low load region (see FIG. 3). In the one-valve stop state, it is desirable to use an air motion device (tumble control valve 9) and enhance the in-cylinder flow to promote fuel vaporization and further reduce HC discharged from the engine. In addition, closing the tumble control valve 9 increases the air flow rate passing through the intake valve 5B that interferes with fuel spray, so the fuel adhering to the valve umbrella is blown off on the air flow to form an air-fuel mixture. It can also be used.
[0019]
However, since the maximum air amount is further restricted when the tumble control valve 9 is closed, the operating range (closed region) of the tumble control valve 9 is the lower rotation / low load side region of the single valve stop region. (See FIG. 3).
[0020]
In order to realize the above control, the intake valves 5A and 5B (at least one of the intake valves 5A) can be stopped in a closed state by a variable valve gear (10 in FIG. 4). In this case, as a variable valve operating device, a cam-driven type that can obtain 0 lift (or operation with a minute lift) by switching the cam by hydraulic pressure, an eccentric cam is used to arbitrarily change the lift amount by hydraulic pressure. Can be used, or an electromagnetic drive type capable of obtaining an arbitrary lift characteristic.
[0021]
FIG. 4 is a block diagram of the control system. The engine control unit (ECU) 11 that controls the operation of the variable valve gear 10 together with the ignition plug 2, the fuel injection valve 7, the tumble control valve (TCV) 9, and the like is connected to the engine. Signals of a rotation speed sensor 12 capable of detecting the rotation speed N, a load sensor 13 capable of detecting a load (for example, accelerator opening) L, and a water temperature sensor 14 capable of detecting the engine cooling water temperature Tw are input.
[0022]
FIG. 5 is a control flow executed by the ECU 11 and is executed for the one-valve stop control and the TCV control in the homogeneous operation mode.
In S1, engine speed N, load L, water temperature Tw, etc. are read from various sensors.
[0023]
In S2, the water temperature Tw is compared with a predetermined value to determine whether it is cold (Tw ≦ predetermined value) or after warming up (Tw> predetermined value).
If it is cold (Tw ≦ predetermined value), the process proceeds to S3.
[0024]
In S3, it is determined whether or not the engine speed N is a low rotation / low load region where the engine speed N is equal to or less than a predetermined threshold value N1 and the load L is equal to or less than the predetermined threshold value L1. This region is a region that can be operated within the maximum amount of air that can be sucked in the one-valve stop state (and the tumble control valve is open).
[0025]
In the case of the low rotation / low load region, the process proceeds to S4.
In S4, since the engine is cold (Tw ≦ predetermined value) and is in a low rotation / low load region (region where the required air amount is small), the one-valve stop is performed. This is because the interference between the fuel spray and the intake valve is suppressed to reduce the HC emission amount when the engine is cold.
[0026]
On the other hand, if it is determined in S2 that the engine has been warmed up (Tw> predetermined value), or if it is determined in S3 that it is not in the low rotation / low load region, the process proceeds to S5.
In S5, normal operation (both valve operation) is performed without stopping the single valve. The control of the tumble control valve (TCV) during normal operation is determined according to the engine performance requirements.
[0027]
When the single valve is stopped in S4, the tumble control valve (TCV) corresponding to the single valve stopped state is controlled in S6 and thereafter.
In S6, it is determined whether or not the engine speed N is a predetermined threshold value N2 or less and the load L is an extremely low rotation / extremely low load region where the engine speed N is equal to or less than the predetermined threshold value L2. This region is a region that can be operated within the maximum amount of air that can be sucked when the one-valve is stopped and the tumble control valve is closed. Naturally, N2 <N1 and L2 <L1.
[0028]
In the case of the extremely low rotation / ultra-low load region, the process proceeds to S7.
In S7, it is determined whether or not the tumble control valve (TCV) is closed. If not, the tumble control valve (TCV) is closed in S8. Since the required air amount can be secured even when the tumble control valve is closed, the in-cylinder flow is enhanced by closing the tumble control valve to further reduce HC.
[0029]
If it is not the extremely low rotation / ultra low load region, the process proceeds to S9.
In S9, it is determined whether or not the tumble control valve (TCV) is open. If not, the tumble control valve (TCV) is opened in S8. Since the necessary air amount cannot be secured when the tumble control valve is closed, the tumble control valve is opened to secure the necessary air amount, and HC is reduced only by stopping the one valve.
[0030]
In FIG. 6, as an example of control, one-valve stop control when starting → first idle → cooling / low rotation / low load operation → cold / high rotation / high load operation → after warming up and The state of TCV control is shown. In this example, since it is assumed that a hydraulic variable valve device is used, the one-valve stop is started after the start (after the hydraulic pressure is increased), but if it is an electromagnetic variable valve device, Single valve stop can be started immediately.
[Brief description of the drawings]
FIG. 1 is a plan layout view of an internal combustion engine showing an embodiment of the present invention. FIG. 2 is a cross-sectional view of an essential part of the internal combustion engine and a view taken along arrow A. FIG. Figure [Figure 4] Configuration diagram of the control system [Figure 5] Control flow chart [Figure 6] Control time chart [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Spark plug 3A, 3B Intake port 4A, 4B Exhaust port 5A, 5B Intake valve 6A, 6B Exhaust valve 7 Fuel injection valve 8 Partition plate 9 Tumble control valve (TCV)
10 Variable valve gear 11 Engine control unit (ECU)
12 Rotational speed sensor 13 Load sensor 14 Water temperature sensor

Claims (5)

In a direct-injection spark-ignition internal combustion engine that injects fuel from a fuel injection valve disposed on the side of the combustion chamber to the center of the combustion chamber via two intake valves,
In addition to providing a means for determining the cold state of the engine, a variable valve device capable of stopping one intake valve in a closed state, and in an operation mode in which fuel injection is performed in the intake stroke and when the engine is cold While stopping the intake valve of the valve in a closed state ,
A direct- injection spark comprising an air motion device for enhancing tumble flow in a cylinder in an intake passage, and operating the air motion device to enhance tumble flow in the cylinder when performing the one-valve stop Ignition internal combustion engine.   The direct injection spark ignition type internal combustion engine according to claim 1, wherein the one-valve stop is performed only in a predetermined low rotation / low load region.   3. The direct injection spark ignition internal combustion engine according to claim 2, wherein the region where the one valve is stopped is a region which can be operated within a maximum amount of air which can be sucked in the one valve stopped state. The one valve of the area to be stopped, a more low-rotation and low-load region, straight eruption flowers ignition according to claim 2, characterized in that by operating the air motion device to strengthen the tumble flow within the cylinder Internal combustion engine. The region where the single valve is stopped is a region where the single valve can be operated within the maximum amount of air that can be inhaled when the single valve is stopped and the air motion device is not operated, and the region where the air motion valve is operated is the single valve 5. The direct-injection spark ignition internal combustion engine according to claim 4 , wherein the direct-injection spark-ignition internal combustion engine is in a region that can be operated within a maximum amount of air that can be sucked in a stopped state and an operating state of an air motion device.

Images