JP3991888B2 - 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. As a result, the mixture formation in the cylinder is inhibited. As a result, a large amount of liquid fuel is present in the cylinder regardless of whether the engine is cold or warm. The unburned fuel (HC) discharged from the engine ) Has increased.
[0005]
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 the intake valve during intake stroke injection.
[0006]
[Means for Solving the Problems]
For this reason, the present invention uses a variable valve system that can stop one intake valve in the closed state, and stops one intake valve in the closed state in the operation mode in which fuel injection is performed in the intake stroke. It is set as the structure which performs single valve stop.
[0007]
In addition, an air motion valve that controls the in-cylinder flow by opening and closing a part of the passage cross-sectional area in the intake passage is used, and when the engine is cold, the air motion valve is closed when the one-valve stop is performed. After warming up, the air motion valve is opened when the one-valve stop is performed.
[0008]
Further, when the one-valve stop cannot be executed under the condition of stopping the one-valve, the one-valve stop is prohibited and the air motion valve is forced regardless of whether the engine is cold or warm. It is set as the structure which closes automatically.
[0009]
【The invention's effect】
According to the present invention, during the intake stroke injection, regardless of whether the engine is cold or warm, the one-valve stop is performed so that the fuel spray does not interfere with one of the intake valves. Since there is only one valve and the fuel spray that interferes with the intake valve can be halved, the amount of unburned fuel discharged can be greatly reduced.
[0010]
Also, when the engine is cold, when the single valve is stopped, the air motion valve is closed to strengthen the gas flow that flows into the cylinder from the intake valve during the valve opening operation, thereby stopping the fuel spray from one valve By deflecting toward the intake valve side, interference between the fuel spray and the intake valve during the valve opening operation can be prevented, and the discharge amount of unburned fuel can be further greatly reduced.
[0011]
On the other hand, after the engine is warmed up, the intake valve temperature is high and vaporization is good, so even if fuel spray adheres to the intake valve during valve opening operation, it can be vaporized to some extent. When stopping, the air motion valve is opened to weaken the gas flow flowing into the cylinder from the intake valve during the valve opening operation, thereby suppressing the deflection of the fuel spray, and at the expense of the deflection of the fuel spray. In order to improve mixing, we will reduce unburned fuel emissions by improving combustion performance.
[0012]
Furthermore, when fail-safe is not possible under the condition of single valve stop, the in-cylinder flow is secured by forcibly closing the air motion valve regardless of whether the engine is cold or warm. Minimize combustion and reduce unburned fuel emissions.
[0013]
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.
[0014]
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.
[0015]
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.
[0016]
In addition, the intake ports 3A and 3B are divided into upper and lower divided ports by a partition plate 8, and can be closed upstream of the lower divided port, and air motion that can enhance in-cylinder flow when closed A valve 9 is provided. In this embodiment, since the tumble flow is particularly strengthened, the air motion valve 9 is referred to as a tumble control valve (TCV) 9.
[0017]
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.
[0018]
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. However, 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.
[0019]
Therefore, in the present invention, during the operation mode (homogeneous operation mode) in which fuel injection is performed in the intake stroke, as shown in FIG. 2, one intake valve 5A is stopped in a closed state (0 lift or minute lift). The single valve is stopped, and the engine is operated by the opening / closing operation of only the other intake valve 5B.
[0020]
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, only by this, the amount of fuel spray interference (attachment amount) is simply halved, and the amount of unburned fuel (HC) discharged can be greatly reduced.
[0021]
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).
Further, when only one valve is stopped, the spray adheres to the intake valve 5B that is opened, but when the one valve is stopped, the tumble control valve 9 is closed, as shown in FIG. The gas flow flowing into the cylinder from the intake valve 5B can be strengthened, and this gas flow deflects the fuel spray from the fuel injection valve 7 toward the intake valve 5A when the one-valve is stopped. As a result, although mixing of the fuel is somewhat sacrificed, it is possible to prevent the fuel spray interference (attachment) to both the intake valves 5A and 5B and to further greatly reduce the amount of unburned fuel (HC) discharged. it can.
[0022]
However, when the engine is cold and after warming up, the intake valve temperature is high and the vaporization is good after warming up. Therefore, the fuel spray from the fuel injection valve 7 opens the intake valve 5B. Since the gas can be vaporized to some extent even after adhering to the gas, the gas that flows into the cylinder from the intake valve 5B during the valve opening operation by opening the tumble control valve 9 when the one-valve stop is performed after warming up. By weakening the flow, the fuel spray from the fuel injection valve 7 is prevented from being deflected. In other words, after warming up, the amount of fuel spray interference (attachment amount) is suppressed by stopping only one valve, the mixing sacrificed by the deflection of fuel spray is improved, and a more homogeneous mixture is formed. This is to reduce the amount of unburned fuel (HC) emitted by improving the combustion performance.
[0023]
Further, when the tumble control valve 9 is opened after warming up, an air flow can be blown over the entire valve head portion of the intake valve 5B that opens, and fuel can be prevented from remaining in a portion where the air flow does not hit. Can also be obtained.
[0024]
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 operating apparatus (10 in FIG. 5). As the variable valve device in this case, a cam-driven type that can obtain 0 lift (or minute lift) by switching the cam by hydraulic pressure, or using an eccentric cam to arbitrarily change the lift amount by hydraulic pressure. What can be used, or what can obtain arbitrary lift characteristics with an electromagnetic drive type can be used.
[0025]
FIG. 5 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 spark 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.
[0026]
Here, in the case of fail-safe when the one-valve stop cannot be executed because the control hydraulic pressure to the variable valve operating apparatus 10 cannot be obtained, the one-valve stop is prohibited and the two-valve operation is performed. In this case, however, the in-cylinder flow is ensured by closing the tumble control valve 9 regardless of whether the engine is cold or warm. Not only can the interference between the fuel spray and the intake valve be prevented, but also the in-cylinder flow becomes too weak because the one-valve cannot be stopped. Therefore, by closing the tumble control valve 9 and ensuring the in-cylinder flow, This is to improve and reduce unburned HC.
[0027]
FIG. 6 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.
[0028]
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).
When the engine is cold (Tw ≦ predetermined value), the process proceeds to S3, and the engine speed and load threshold values Ns and Ls for determining the one-valve stop region are set to the reference values N1 and L1. The regions N1 or less and L1 or less determined here are (part of) a region that can be operated within the maximum amount of air that can be sucked in the one-valve stop state.
[0029]
After warm-up (Tw> predetermined value), the process proceeds to S4, and the engine speed and load threshold values Ns and Ls for determining the one-valve stop region are set to N2 and L2 larger than the reference values N1 and L1. Set. Naturally, N2> N1 and L2> L1. This is because after the warm-up, the one-valve stop region is expanded to a region on the higher rotation / high load side than during the cool-down. The region of N2 or less and L2 or less determined here is a region that includes substantially all the region that can be operated within the maximum amount of air that can be sucked in the one-valve stop state.
[0030]
In S5, 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 the threshold value Ns and the load L is equal to or less than the threshold value Ls.
If it is not the low rotation / low load region, the process proceeds to S6.
[0031]
In S6, the single operation is not stopped and the normal operation (both valve operation) is performed. The control of the tumble control valve (TCV) during normal operation is determined according to the engine performance requirements.
In the case of the low rotation / low load region, the process proceeds to S7.
[0032]
In S7, a flag at the fail-safe determination unit indicates whether or not the one-valve stop is not possible, that is, because the control hydraulic pressure to the variable valve operating device cannot be obtained or the fail-safe time cannot be executed. The determination is made based on the value of.
[0033]
If the one-valve stop is not possible, the process proceeds to S8.
In S8, the one-valve stop condition is satisfied and the one-valve stop is possible, so the one-valve stop is performed. This is to reduce the HC emission amount by suppressing the interference between the fuel spray and the intake valve.
[0034]
When the single valve is stopped in S8, the tumble control valve (TCV) corresponding to the single valve stopped state is controlled in S9 and thereafter.
In S9, as in S2, it is determined whether the engine is cold (Tw ≦ predetermined value) or after warming up (Tw> predetermined value). Of course, the determination result at S2 may be stored and retained.
[0035]
If it is cold, proceed to S10 and close the tumble control valve (TCV). Specifically, it is determined whether or not the tumble control valve is closed. If the tumble control valve is not closed, the tumble control valve is closed. When cold, attach great importance to preventing fuel spray from adhering, strengthening the gas flow that flows into the cylinder from the intake valve during valve opening, and deflecting the fuel spray toward the intake valve when one valve is stopped. This is to prevent interference between the fuel spray and the intake valve during the valve opening operation.
[0036]
If the engine has been warmed up, the process proceeds to S11 and the tumble control valve (TCV) is opened. Specifically, it is determined whether or not the tumble control valve is open. If the tumble control valve is not open, the tumble control valve is opened. After warming up, the importance of improving mixing is to weaken the flow of gas flowing into the cylinder from the intake valve during the valve opening operation, and to suppress the deflection of fuel spray. This is also for blowing an air flow over the entire valve head portion of the valve.
[0037]
If it is determined in S7 that the one-valve cannot be stopped because the one-valve cannot be stopped, that is, the control hydraulic pressure to the variable valve operating device cannot be obtained, the process proceeds to S12. Prohibit valve stop and perform double valve operation. At this time, the process further proceeds to S13, and the in-cylinder flow is strengthened by closing the tumble control valve (TCV) regardless of whether the engine is cold or warm. This is because interference between the fuel spray and the intake valve cannot be prevented, so that in-cylinder flow is enhanced to improve combustion and reduce unburned HC. Further, by strengthening the gas flow flowing into the cylinder, the flow velocity of the air that collides with the valve head portion of the intake valve can be increased, and the adhered spray can be blown off and used for the mixture formation.
[0038]
In this embodiment, after warming up the engine, the area where the single valve is stopped is expanded to the area on the higher rotation / high load side than when the engine is cold. Compared to the above, the mixing is good, so the area for reducing the interference (adhesion) between the fuel spray and the intake valve is expanded, in other words, it can be operated within the maximum amount of air that can be inhaled when the single valve is stopped. This is for reducing the HC by setting the entire operation region as the one-valve stop region.
[0039]
In FIG. 7, as a control example, start → first idle → cooling / low rotation / low load operation → cold / high rotation / high load operation → after warming up / low rotation / low load operation → after warming up / The state of single valve stop control and TCV control when high rotation / high load operation has elapsed 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.
[0040]
The dotted line in FIG. 7 shows a case where the single valve cannot be stopped due to a decrease in hydraulic pressure, and both valves are operated while the tumble control valve (TCV) is forcibly closed to ensure in-cylinder flow. Shows when to do.
[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] Explanation of fuel spray deflection [Figure 5] Configuration diagram of control system [Figure 6] Control flow chart [Figure 7] 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 (4)

In a direct-injection spark-ignition internal combustion engine that injects fuel from a fuel injection valve arranged on the side of the combustion chamber to the center of the combustion chamber via two intake valves,
While equipped with a variable valve system that can stop one intake valve in the closed state, and in the operation mode in which fuel injection is performed in the intake stroke, while performing one valve stop to stop one intake valve in the closed state,
Means for determining whether the engine is cold or warm, and an air motion valve that controls the in-cylinder flow by opening and closing a part of the cross-sectional area of the passage in the intake passage. When the engine is warmed up, after the engine is warmed up, when the one-valve stop is performed, the air motion valve is opened,
In the case of fail-safe when the one-valve stop cannot be executed under the condition for performing the one-valve stop, the one-valve stop is prohibited and the air motion valve is forcibly set regardless of whether the engine is cold or warm. A direct-injection spark-ignition internal combustion engine characterized by closing. 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. 4. The direct-injection spark ignition according to claim 2, wherein after the engine is warmed up, the region where the one-valve stop is performed is expanded to a region on the higher rotation / high load side when the engine is cold. Internal combustion engine.

Images