JP4019664B2 - Variable valve control system for engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for controlling an intake / exhaust valve (variable valve) of an engine that can be arbitrarily variably controlled in opening / closing timing, such as an electromagnetic drive type.
[0002]
[Prior art]
As a V-type 8-cylinder engine, there is a crank arrangement called a two-plane crankshaft. In this device, as shown in FIGS. 2A to 2C, four crank pins are arranged with a phase of 90 ° and are located on two orthogonal planes.
[0003]
Second, as shown in FIGS. 2D to 2E, the crank arrangement for each bank is the same as that of the in-line four cylinders, and four crank pins are arranged with a phase of 180 °. Since it is located on one plane, it is a crank arrangement called a single plane crankshaft.
The crank arrangement of the above-described two-plane crankshaft has a good balance of inertial force, so this crank arrangement is exclusively used in passenger cars that place importance on ride comfort.
[0004]
However, in this crank arrangement, the combustion order is not alternated between the left and right banks, and the combustion intervals in the same bank are unequal, so that intake and exhaust pulsations can be effectively used for all cylinders. Have difficulty. Even if the pulsation effect (inertia supercharging) is set to two cylinders at intervals of 180 °, the effect is not obtained for the remaining two cylinders, and the output of the entire engine is sacrificed.
[0005]
In order to effectively use the pulsation, a long and large intake / exhaust manifold layout is required across both banks, which is not practical.
Japanese Patent Application Laid-Open No. 6-229212 discloses that the difference in intake air amount for each bank is detected and the valve timing for each bank is corrected so that the difference in intake air amount is eliminated. When the two-plane crankshaft V-type 8-cylinder engine is used, it is impossible to cope with variations in intake air amount between cylinders in the same bank by correcting the valve timing for each bank.
[0006]
The present invention has been made paying attention to such a conventional problem. When the combustion intervals are unequal and the intake efficiency conditions between the cylinders are not equal, the intake air amount is equalized to eliminate variations in combustibility. It is an object of the present invention to provide a variable valve control apparatus for an engine that can be provided.
[0007]
[Means for Solving the Problems]
For this reason, the invention according to claim 1
An engine in which the valve characteristics of the intake and exhaust valves can be independently controlled for each cylinder, one exhaust pipe is connected to the cylinder group, and the combustion interval between the cylinders in the cylinder group is different.
An intake valve or an exhaust of a cylinder in which the intake efficiency is inferior to that of other cylinders in a group of cylinders having different combustion intervals between the cylinders except in a region where the intake inertia supercharging effect due to intake / exhaust pulsation is small. Change the valve characteristics of at least one of the valves in a direction to increase the suction efficiency,
In the region where the intake inertia supercharging effect due to the intake / exhaust pulsation is small, the same valve characteristic is maintained between cylinders without changing the valve characteristic .
[0008]
According to the invention of claim 1,
Increase the potential of the entire engine by changing the valve characteristics of cylinders with poor intake efficiency in areas other than those where the intake inertia supercharging effect due to intake and exhaust pulsations is small, and increasing the intake efficiency to the same level as other cylinders. Output performance and fuel economy can be improved.
On the other hand, in low load areas such as idle, the original intake amount is small and the influence from other cylinders is small, so the pulsation effect of intake and exhaust is small, and changing the valve characteristics increases the combustion difference due to the difference in residual gas End up. Therefore, in such a region, good performance is ensured by maintaining the same valve characteristics among the cylinders.
[0009]
According to the invention of claim 2,
As described above, the crank arrangement of the two-plane crankshaft eliminates the variation in intake air volume between cylinders, which is a problem with the crank arrangement, while ensuring a good balance of inertial force. it can.
The invention according to claim 3
The valve characteristic is changed between each cylinder having a combustion interval of 180 ° with respect to the immediately preceding combustion cylinder and each other cylinder in at least one cylinder group.
[0010]
According to the invention of claim 3,
In the above 8-cylinder engine, the combustion interval in the same bank is ideally equal, that is, 180 °, and the cylinder having an interval of 180 ° with respect to the previous combustion cylinder is generally affected by exhaust interference or the like. Hateful. On the other hand, other cylinders are affected by exhaust interference and the like, and the suction efficiency decreases. Therefore, the intake efficiency of the entire engine can be increased by changing the valve characteristics in the two groups.
[0011]
The invention according to claim 4
In at least one cylinder group, the valve characteristics are changed between each cylinder having a combustion interval of 180 ° with respect to the immediately preceding combustion cylinder, a cylinder having a combustion interval of 90 °, and a cylinder having a combustion interval of 270 °. It is characterized by.
According to the invention of claim 4,
In the 8-cylinder engine, there are two cylinders with a combustion interval of 180 ° from the immediately preceding combustion cylinder for each bank, and the remaining are a cylinder with a combustion interval of 90 ° and a cylinder with a combustion interval of 270 °. Therefore, the intake efficiency of the entire engine can be increased by changing the valve characteristics.
[0012]
The invention according to claim 5
In at least one cylinder group, the exhaust valve closing timing of a cylinder having inferior intake efficiency is made closer to the top dead center earlier than the exhaust valve closing timing of other cylinders set after the top dead center .
According to the invention of claim 5,
By making the exhaust valve closing timing of a cylinder with poor intake efficiency earlier than other cylinders, the valve overlap amount of the cylinder is reduced, the residual gas amount is decreased, and the fresh air amount is relatively increased. By doing so, inhalation efficiency can be increased.
[0013]
The invention according to claim 6
In at least one cylinder group, the intake valve opening timing of a cylinder having inferior intake efficiency is made to approach the top dead center by delaying the intake valve opening timing of other cylinders set before the top dead center .
According to the invention of claim 6,
By delaying the intake valve opening timing of a cylinder with poor intake efficiency compared to other cylinders, the valve overlap amount of the cylinder is reduced, the residual gas amount is reduced, and the fresh air amount is relatively increased. By doing so, inhalation efficiency can be increased.
[0014]
The invention according to claim 7
In the at least one cylinder group, the intake valve closing timing of a cylinder having inferior intake efficiency is corrected so as to increase the intake air amount.
According to the invention of claim 7,
The intake valve closing timing at which the total amount of intake gas becomes maximum due to the intake inertia is at a position delayed by a predetermined amount after bottom dead center. Therefore, the intake air amount (intake efficiency) can be increased by increasing the intake gas total amount by correcting the intake valve closing timing so as to approach the time when the intake gas total amount becomes maximum.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 illustrates a V-type 8-cylinder engine that employs a two-plane crankshaft and has a combustion order as shown in FIG.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a system configuration diagram of an engine in the embodiment.
In FIG. 1, air is sucked into each cylinder of a V-type 8-cylinder engine 1 mounted on a vehicle via an air cleaner 2, an electric throttle chamber 3, an intake collector 4, an intake manifold 5, and an intake valve 6. As shown in FIGS. 2A to 2C, the V-type 8-cylinder engine 1 is referred to as the above-described two-plane crankshaft in which four crank pins are arranged with a phase of 90 °. Having a crank arrangement.
[0018]
An electromagnetic fuel injection valve 7 for directly injecting fuel (gasoline) is provided in the combustion chamber of each cylinder, and an air-fuel mixture is formed in the combustion chamber by the fuel injected from the fuel injection valve 7 and the intake air. The
The air-fuel mixture formed in the combustion chamber is ignited and combusted by the spark plug 8.
However, the engine 1 is not limited to the direct injection gasoline engine described above, and may be an engine configured to inject fuel into the intake port.
[0019]
Exhaust gas from the engine 1 is released into the atmosphere via an exhaust valve 9, an exhaust manifold 10, a catalyst 11, and a muffler 12. The exhaust manifold 10 has a structure in which one exhaust pipe 10A, 10B is connected to each bank (cylinder group), and these are joined downstream.
The intake valve 6 and the exhaust valve 9 are electronically controlled to be opened and closed by a valve driving device 13, respectively.
[0020]
As sensors for detecting various states of the engine 1, an air flow meter 14 for detecting an intake air amount, a throttle sensor 15 for detecting a throttle opening, a reference signal is output at a reference crank angle of each cylinder, and at each minute crank angle. A crank angle sensor 16 that can output a unit angle signal and detect the engine speed based on the signal, a water temperature sensor 17 that detects the engine coolant temperature, and the like are provided.
[0021]
Detection signals from the various sensors are input to the control unit 18, and the control unit 18 outputs a fuel injection signal to the fuel injection valve 7 based on these detection signals to perform fuel injection control, and the ignition plug An ignition signal is output to 8 to perform ignition control, and further, a valve drive signal is output to the valve drive device 13 to control opening and closing of the intake valve 6 and the exhaust valve 9.
[0022]
Here, the hardware of the electromagnetic valve device comprising the intake valve 6 and the exhaust valve 9 and the valve driving device 13 for driving them will be described with reference to FIG.
In FIG. 3, the exhaust valve 9 is attached to the cylinder head 21 in the same manner as in the prior art. That is, a stem 31 of the exhaust valve 9 is slidably inserted into a valve guide 22 provided in the cylinder head 21, and an upper seat 32 is attached to the upper end portion of the stem 31 via a valve cotter or the like. A valve closing spring 33 that urges the exhaust valve 9 in the valve closing direction (compressed by a predetermined amount from the free length) is disposed between the upper seat 32 and the lower seat on the cylinder head side.
[0023]
When the exhaust valve 9 is in the fully closed state and the armature is adsorbed by the valve closing electromagnet 43 described later, the exhaust valve 9 is separated from the upper end of the stem 31 by a predetermined amount, in other words, has a predetermined valve clearance. Thus, the movable shaft 40 of the valve driving device 13 is arranged coaxially with the stem 31.
The valve driving device 13 includes a housing 41 made of a non-magnetic material, an armature 42 provided integrally with the movable shaft 40 and slidably accommodated in the housing 41, and an armature capable of magnetically attracting the armature 42. The valve closing electromagnet 43 fixedly disposed in the housing 42 at a position facing the upper surface of the 42, and the housing at a position facing the lower surface of the armature 42 so that the armature 42 can be magnetically attracted to hold the exhaust valve 4 open. A valve-opening electromagnet 44 fixedly disposed in the valve 41 and a valve-opening spring 45 that urges the armature 42 toward the valve opening direction of the exhaust valve 4 are configured.
[0024]
As shown in FIG. 4, when both the valve closing electromagnet 43 and the valve opening electromagnet 44 are demagnetized, the exhaust valve 9 is configured to be in a half-open position. When only the valve electromagnet 43 is energized and energized, the armature 42 is magnetically attracted by the valve closing electromagnet 43 in a direction to push and retract the valve opening spring 45, while when only the valve electromagnet 44 is energized and energized from the half-open position, the armature is energized. 42 is magnetically attracted by the valve-opening electromagnet 44 in the direction to open the exhaust valve 9 by pushing and contracting the valve-closing spring 33.
[0025]
Although the opening / closing operation of the exhaust valve 9 has been described above, the intake valve 6 operates in the same manner with the same configuration.
Before starting, after performing initialization to hold the intake valve 6 and the exhaust valve 9 from the half-open position to the valve open (full open) position or the valve close position, the opening / closing set according to the engine operating state Open / close control is performed so as to open and close at the time.
[0026]
By the way, as described above, in the V-type 8-cylinder engine of the two-plane crankshaft in this embodiment, the combustion order is not alternated between the left and right banks, and the combustion intervals in the same bank are unequal ( As shown in FIG. 5, intake inertia supercharging that effectively uses intake and exhaust pulsations cannot be performed, and the explosion pressure of each cylinder varies.
That is, the engine 1 can independently control the valve characteristics of the intake valve 6 and the exhaust valve 9 for each cylinder by the valve driving device 13, and one exhaust pipe 10A, 10B is connected to each cylinder group, and The combustion intervals between the cylinders in the cylinder group are different.
[0027]
Therefore, in the present invention, by changing the valve timing for a cylinder in which the residual gas increases and the combustion deteriorates, the residual gas amount of the cylinder is reduced or the intake fresh air amount is increased, and the combustion characteristics of each cylinder are increased. By equalizing, the combustion efficiency of the whole engine is increased and the potential is improved.
That is, in the cylinder group in which the combustion interval between the cylinders is different, the valve characteristic of at least one of the intake valve and the exhaust valve of the cylinder in which the intake efficiency is inferior compared to the other cylinders is changed in a direction to increase the intake efficiency. As a method of reducing the residual gas amount, there is a method of changing the valve overlap amount of the intake valve 6 and the exhaust valve 9 in a direction of reducing. Specifically, as shown in FIG. 6, at least one of the closing timing (EVC) of the exhaust valve 9 is advanced or the opening timing (IVO) of the intake valve 6 is delayed as shown in FIG. realizable.
[0028]
In addition, as shown in FIG. 8, when the valve overlap center is originally set to an advance side larger than the top dead center, the exhaust valve 9 is closed (EVC) and the intake valve 6 is opened (IVO). Can be reduced while the valve overlap amount is kept the same even if retarded by the same amount.
Further, as a method of increasing the amount of fresh intake air by increasing the total amount of intake gas, it can be realized by changing the closing timing (IVC) of the intake valve 6 in the direction of increasing the total amount of intake gas. As shown in FIG. 9, the intake valve closing timing IVC at which the intake air amount becomes maximum due to the intake inertia is at a position delayed by a predetermined amount after bottom dead center. Therefore, the IVC is corrected in a direction approaching the IVCQmax that maximizes the intake air amount. In a general engine, the IVC itself is set to the position where the air enters most, so there is no possibility, but the intake valve is electromagnetically driven and the intake air amount is controlled by IVC control as in this embodiment. Then it is effective.
[0029]
The influence of the exhaust interference or the like varies depending on engine operating conditions (rotation speed, load, atmospheric pressure, etc.). Therefore, it is desirable that the presence / absence of correction of the variation in the intake air amount and the correction amount be changed according to the engine operating conditions. For example, during idle operation, there is almost no influence of exhaust interference, and conversely, the influence of a change in residual gas amount by changing the valve timing of each cylinder is large. For this reason, it is desirable not to perform correction itself because it may cause a decrease in rotational stability.
[0030]
Hereinafter, each embodiment will be described with reference to the flowcharts shown in FIGS.
In FIG. 10, in step 1, an engine operating region (rotation speed, load, etc.) is detected based on detection signals from various sensors.
In step 2, it is determined whether the detected current engine operating region is a setting region where the variation in intake air amount is large and the variation correction is performed. Specifically, the middle / high load region excluding the low load region such as the idle is set as a setting region for correcting the intake air amount.
[0031]
If it is determined in step 2 that the region is set, the process proceeds to step 3 to determine a cylinder for correcting the intake air amount. Specifically, when the interval (crank angle) from the cylinder that was in the previous combustion stroke in the same bank is 180 °, the exhaust pulsation effect is obtained, so the intake efficiency is high, but when it is 90 °, or When the angle is 270 °, exhaust interference occurs, exhaust pulsation effect cannot be obtained, intake efficiency decreases, and the intake air amount needs to be corrected to increase. Referring to FIG. 5, the seventh and fifth cylinders in the left bank and the eighth and fourth cylinders in the right bank are 180 ° apart from the previous combustion cylinder, so the intake air amount is not corrected. The first and third cylinders in the left bank and the sixth and second cylinders in the right bank are determined to be cylinders that correct the intake air amount because the distance from the front combustion cylinder is 270 ° or 90 °.
[0032]
In step 4, a correction amount for correction for advancing the closing timing EVC of the exhaust valve 9 is calculated based on the engine operating conditions for the cylinder for which the intake air amount is corrected.
In step 5, a correction amount for correcting the opening timing IVO of the intake valve 6 is similarly calculated.
In step 6, a correction amount for correcting the closing timing IVC of the intake valve 6 so as to approach the maximum intake air amount IVCQmax is calculated.
[0033]
Here, the correction amount in Step 4 to Step 6 is set so that the EVC is increased by increasing the IVO so that the reduction amount of the intake air amount with respect to the cylinder whose interval from the previous combustion cylinder is 180 ° can be corrected based on the engine operating conditions. This is calculated as a correction amount for performing a correction to reduce the residual gas amount by delaying the valve overlap amount and to increase the total intake gas amount close to IVCQmax.
[0034]
If it is determined in step 2 that the region is not the setting region for correcting the variation in the intake air amount, the process proceeds to step 7 where the valve timing correction amount is set to 0 and the correction is prohibited.
In step 8, the valve timing signals set by correcting with the respective correction amounts calculated as described above are output, and the valve timings of the intake valve 6 and the exhaust valve 9 are controlled.
[0035]
FIG. 11 shows a flowchart of the second embodiment, in which only EVC and IVO are corrected and IVC is not corrected. In this case, not only the valve overlap amount is decreased by increasing the EVC and delaying the IVO, but as shown in FIG. 8, the EVC and the IVO are retarded by equal amounts while the valve overlap amount remains constant. You may do it.
[0036]
In the flowchart of the third embodiment shown in FIG. 12, only EVC is advanced, and in the flowchart of the fourth embodiment shown in FIG. 13, only IVO is corrected, and the fourth implementation shown in FIG. In the flowchart of the embodiment, only correction for bringing only IVC close to IVCQmax is performed.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an engine in an embodiment.
FIG. 2 is a cross-sectional view showing the configuration of the electromagnetic valve device in the embodiment when the intake and exhaust valves are closed.
FIG. 3 is a sectional view showing the configuration of the electromagnetic valve device when the exhaust valve is open.
FIG. 4 is a diagram showing a schematic configuration and operation of a V-type 8-cylinder engine with a two plane crankshaft in comparison with an operation of a V-type 8-cylinder engine with a single plane crankshaft.
FIG. 5 is a view for explaining the combustion stroke sequence of a V-type 8-cylinder engine with a two-plane crankshaft.
FIG. 6 is a view showing a method of reducing the residual gas amount by advancing the closing timing of the exhaust valve.
FIG. 7 is a view showing a method of reducing the residual gas amount by delaying the opening timing of the intake valve.
FIG. 8 is a view showing a method of reducing the residual gas amount by delaying the closing timing of the exhaust valve and the opening timing of the intake valve.
FIG. 9 is a view showing a method of increasing the intake air amount by correcting the intake valve closing timing in a direction that maximizes the total amount of intake gas.
FIG. 10 is a flowchart showing a control routine of the first embodiment.
FIG. 11 is a flowchart showing a control routine of the second embodiment.
FIG. 12 is a flowchart showing a control routine of a third embodiment.
FIG. 13 is a flowchart showing a control routine of the fourth embodiment.
FIG. 14 is a flowchart showing a control routine of a fifth embodiment.
[Explanation of symbols]
1 V-type 8-cylinder engine 6 Intake valve 9 Exhaust valve 13 Valve drive device 14 Air flow meter 16 Crank angle sensor 18 Control unit

Claims (7)

An engine in which the valve characteristics of the intake and exhaust valves can be independently controlled for each cylinder, one exhaust pipe is connected to the cylinder group, and the combustion interval between the cylinders in the cylinder group is different.
An intake valve or an exhaust of a cylinder in which the intake efficiency is inferior to that of other cylinders in a group of cylinders having different combustion intervals between the cylinders except in a region where the intake inertia supercharging effect due to intake / exhaust pulsation is small. Change the valve characteristics of at least one of the valves in a direction to increase the suction efficiency,
A variable valve control apparatus for an engine characterized by maintaining the same valve characteristic between cylinders without changing the valve characteristic in a region where the intake inertia supercharging effect due to the pulsation of intake and exhaust is small .   The engine is an eight-cylinder engine having a cylinder group of four cylinders in one bank, and four crank pins are arranged with a phase of 90 ° and are located on two orthogonal planes. 2. The variable valve control apparatus for an engine according to claim 1, wherein the crank valve arrangement is a plain crankshaft.   3. The engine according to claim 2, wherein the valve characteristic is changed between each cylinder having a combustion interval of 180 ° with respect to the immediately preceding combustion cylinder and at each other cylinder in at least one cylinder group. Variable valve control device.   In at least one cylinder group, the valve characteristics are changed between each cylinder having a combustion interval of 180 ° with respect to the immediately preceding combustion cylinder, a cylinder having a combustion interval of 90 °, and a cylinder having a combustion interval of 270 °. The variable valve control apparatus for an engine according to claim 2 or claim 3, wherein The exhaust valve closing timing of a cylinder having inferior intake efficiency in at least one cylinder group is made closer to the top dead center earlier than the exhaust valve closing timing of other cylinders set after the top dead center. The variable valve control apparatus for an engine according to any one of claims 1 to 4. The intake valve opening timing of a cylinder with inferior intake efficiency in at least one cylinder group is made to approach the top dead center by delaying the intake valve opening timing of other cylinders set before the top dead center. The variable valve control apparatus for an engine according to any one of claims 1 to 5. The engine according to any one of claims 1 to 6, wherein an intake valve closing timing of a cylinder having inferior intake efficiency is corrected so as to increase an intake air amount in at least one cylinder group. Variable valve controller .

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