JP2001020763A - Internal combustion engine having an electromagnetically driven valve - Google Patents

Abstract

(57) Abstract: The present invention relates to an internal combustion engine in which at least an intake valve is constituted by an electromagnetically driven valve, and aims to prevent a change in intake air amount between cylinders due to a variation in intake pressure. And SOLUTION: A predetermined timing during an intake stroke (crank angle CA
0), the intake pressure PM and the engine speed NE are detected (steps 100 to 104), and the detected PM and NE are detected.
Then, the closing timing of the intake valve is determined such that the target intake air amount can be obtained by referring to the map (step 108). In another embodiment, when the four-cylinder internal combustion engine operates in the six-cycle operation, the intake valve is closed when the immediately preceding intake stroke is stopped compared to when the immediately preceding intake stroke is performed. The valve timing is changed so that the intake air amount increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having an electromagnetically driven valve, and more particularly to an internal combustion engine having an electromagnetically driven valve suitable for suppressing a difference in intake air amount between cylinders due to a variation in intake pressure. About the institution.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 10-1030
As disclosed in Japanese Patent Publication No. 92-92, there is known a control device for an internal combustion engine in which intake and exhaust valves are constituted by electromagnetically driven valves. According to the electromagnetically driven valve, the opening / closing timing of the intake / exhaust valve can be freely set independently of the crank angle. In the above-described conventional control device, the operation cycle is changed to two cycles, four cycles, six cycles, or the like according to the operation state of the internal combustion engine by utilizing the characteristics of the electromagnetically driven valve. When the operation cycle of the internal combustion engine is switched, there is a possibility that a shock due to a sudden torque fluctuation occurs at the time of the switching. Therefore, in the above-described conventional control device, the opening / closing timing of the intake / exhaust valve is adjusted so that the torque fluctuation at the time of switching the operation cycle is reduced.

[0003]

By the way, in a multi-cylinder internal combustion engine, due to variations in dimensions among the cylinders, etc.,
The intake pressure during the intake stroke changes for each cylinder,
The amount of intake air to each cylinder also varies between cylinders. in this case,
When the output torque fluctuates between the cylinders, the vibration of the internal combustion engine increases. Further, if the intake air amount changes between cylinders, the air-fuel ratio changes, which leads to deterioration of exhaust emission. However, in the above conventional control device, no consideration is given to preventing a change in intake air amount between cylinders.

[0004] The present invention has been made in view of the above points, and provides an internal combustion engine having an electromagnetically driven valve that can set the intake air amount of each cylinder to a target value even when the intake pressure changes. The purpose is to provide.

[0005]

The above object is achieved by the present invention.
As described in the above, at least an intake valve is an internal combustion engine having an electromagnetically driven valve constituted by an electromagnetically driven valve, and the intake air for each cylinder is adjusted according to the intake pressure so that the intake air amount of each cylinder becomes a target value. This is achieved by an internal combustion engine having an electromagnetically driven valve including intake valve opening / closing timing determining means for determining the opening / closing timing of the valve.

According to the first aspect of the present invention, the higher the intake pressure in the intake stroke, the larger the intake air amount. On the other hand, the intake air amount in the intake stroke changes according to the opening / closing timing of the intake valve. Therefore, according to the present invention, the intake valve opening / closing timing determining means determines the opening / closing timing of the intake valve for each cylinder in accordance with the intake pressure of each cylinder, thereby setting the intake air amount of each cylinder to the target value. be able to.

Further, as described in claim 2, claim 1
In the internal combustion engine having the electromagnetically driven valve described above, the intake valve opening / closing timing determining means may determine the opening / closing timing of the intake valve according to the intake pressure at a predetermined timing during the intake stroke. According to the second aspect of the present invention, the intake air amount during the intake stroke has a magnitude corresponding to the intake pressure when the intake valve is closed. Further, based on the intake pressure at a predetermined time during the intake stroke, the intake pressure at each time after the intake stroke can be estimated. That is, it is possible to estimate the closing timing of the intake valve such that a desired intake air amount is obtained from the intake pressure at a predetermined timing in the intake stroke. Therefore, the intake valve opening / closing timing determining means can determine the opening / closing timing of the intake valve according to the intake pressure at a predetermined timing during the intake stroke so that the intake air amount becomes the target value. Further, in the present invention,
Since the closing timing of the intake valve in the intake stroke can be determined before the end of the intake stroke, the intake air amount can be immediately adjusted to the target value in response to a change in the intake pressure.

In this case, the change of the intake pressure during the intake stroke is as follows:
It also depends on the engine speed. Therefore, the intake valve opening / closing timing determining means adjusts the opening / closing timing of the intake valve in accordance with the engine speed, thereby more accurately adjusting the intake / intake amount of each cylinder to the target value. can do. Further, the intake pressure may be detected by a pressure sensor provided in an intake pipe or a cylinder.

According to a fifth aspect of the present invention, in the internal combustion engine having the electromagnetically driven valve according to the first aspect, the intake valve opening / closing timing determining means makes the intervals of the intake stroke unequal. This is achieved by an internal combustion engine having an electromagnetically driven valve that estimates an intake pressure based on a past history of an intake stroke in an operating state of the internal combustion engine. In the invention described in claim 5, while any of the cylinders is performing the intake stroke, the intake pressure gradually decreases as air is sucked into the cylinder. On the other hand, in a state where the intake stroke is not performed in any of the cylinders, outside air flows into the intake pipe, so that the intake pressure gradually increases. For this reason, in the operating state of the internal combustion engine in which the intervals between the intake strokes are unequal, the past history of the intake stroke, for example, depending on whether the intake stroke was performed in any one of the cylinders immediately before or after the intake stroke, Changes the intake pressure. Therefore, according to the present invention, the intake valve opening / closing timing determining means can estimate the intake pressure based on the past history of the intake stroke, and determine the opening / closing timing of the intake valve based on the estimated intake pressure. Thus, the intake air amount of each cylinder can be set as the target value.

In this case, in a state where the intake stroke is not performed in any of the cylinders, as the throttle opening increases, a larger amount of air flows into the intake pipe, so that the intake pressure rapidly increases. In addition, as the duration of the state in which the intake stroke is not performed in any of the cylinders is longer, that is, as the engine speed is lower, the intake pressure at the start of the next intake stroke becomes higher.

Therefore, in the internal combustion engine having the electromagnetically driven valve according to the present invention, the intake valve opening / closing timing determining means may control the intake air in accordance with at least one of the engine speed and the throttle opening. By adjusting the opening and closing timing of the valve, the intake air amount of each cylinder can be more accurately adjusted to the target value.

[0012]

FIG. 1 is a block diagram of an internal combustion engine according to one embodiment of the present invention. The internal combustion engine of the present embodiment is controlled by an electronic control unit (hereinafter, referred to as ECU) 10. The internal combustion engine includes a cylinder block 12.
Inside the cylinder block 12, a cylinder 14 and a water jacket 16 are formed. The internal combustion engine of this embodiment is a four-cylinder internal combustion engine having four cylinders 14. FIG. 1 shows one cylinder 14 among a plurality of cylinders.

A piston 18 is provided inside the cylinder 14. The piston 18 can slide inside the cylinder 14 in the vertical direction in FIG. A cylinder head 20 is fixed to an upper portion of the cylinder block 12. In the cylinder head 20, an intake port 22 and an exhaust port 24 are formed for each cylinder. An intake pressure sensor 25 is provided at the intake port 22 of each cylinder. The intake pressure sensor 25 is connected to each intake port 2.
A signal corresponding to the pressure 2 (hereinafter referred to as the intake pressure PM) is expressed as E
Output to CU10. The ECU 10 detects the intake pressure PM of each cylinder based on the output signal of the intake pressure sensor 25. Note that the intake pressure sensor 25 may be provided inside the combustion chamber 26.

The bottom of the cylinder head 20, the piston 18
And a side wall of the cylinder 14 define a combustion chamber 26. The above-described intake port 22 and exhaust port 24 both open to the combustion chamber 26. Intake port 2
2 and the opening end on the combustion chamber 26 side and the exhaust port 24
The valve seats 28 and 30 are formed at the open ends of the combustion chamber 26 side of the fuel cell. In the combustion chamber 26,
The tip of the spark plug 32 is exposed.

Electromagnetic drive valves 38 and 40 are incorporated in the cylinder head 20. The electromagnetically driven valve 38 is an intake valve 4
2 is provided. The intake valve 42 shuts off between the intake port 22 and the combustion chamber 26 by sitting on the valve seat 28, and conducts between the intake port 22 and the combustion chamber 26 by separating from the valve seat 28. Let it. On the other hand, the electromagnetically driven valve 40 has an exhaust valve 44. The exhaust valve 44 shuts off between the exhaust port 24 and the combustion chamber 26 by sitting on the valve seat 30, and conducts between the exhaust port 24 and the combustion chamber 26 by separating from the valve seat 30. Let it.

The electromagnetically driven valves 38 and 40 have the same configuration. Hereinafter, the configuration and operation of the electromagnetically driven valve 38 will be described as a representative example thereof with reference to FIG. FIG. 2 is a cross-sectional view illustrating the entire configuration of the electromagnetically driven valve 38. As shown in FIG. 2, the intake valve 42 includes a valve shaft 45 extending upward. The valve shaft 45 is held so as to be displaceable in the axial direction by a valve guide 46 fixed inside the cylinder head 20. The electromagnetically driven valve 38 also has an armature shaft 48 provided above the valve shaft 45. The armature shaft 48 is a rod-shaped member made of a non-magnetic material. Armature shaft 48
Is in contact with the upper end surface of the valve shaft 45.

A lower retainer 50 is provided at the upper end of the valve shaft 45.
Has been fixed. A lower spring 52 is provided below the lower retainer 50. The lower end of the lower spring 52 is in contact with the cylinder head 20. The lower spring 52 urges the lower retainer 50 and the armature shaft 48 upward in FIG.

An upper retainer 54 is fixed to the upper end of the armature shaft 48. Apparitainer 5
The lower end of the upper spring 56 is in contact with the upper part of the fourth spring 4. A cylindrical upper cap 57 is provided around the upper spring 56 so as to surround the outer periphery thereof. The upper end of the upper spring 56 is in contact with an adjustment bolt 58 screwed to the upper cap 57. The upper spring 56 urges the retainer 54 and the armature shaft 48 downward in FIG.

An armature 60 is joined to the outer periphery of the armature shaft 48. The armature 60 is an annular member made of a soft magnetic material. Armature 60
The upper coil 62 and the upper core 64 are disposed above the upper part. Below the armature 60, a lower coil 66 and a lower core 68 are provided. Both the upper core 64 and the lower core 68 are members made of a magnetic material. The armature shaft 48 is slidably held at the center of the upper core 64 and the lower core 68. Also, the upper coil 62 and the lower coil 66
Is connected to the ECU 10. The ECU 10 supplies an exciting current having a predetermined waveform to the upper coil 62 and the lower coil 66.

An outer cylinder 74 is provided on the outer periphery of the upper core 64 and the lower core 68. The upper core 64 and the lower core 68 are held by an outer cylinder 74 so that a predetermined interval is secured between them. The upper cap 57 is fixed to the upper end surface of the upper core 64. The adjuster bolt 58 is adjusted so that the neutral position of the armature 60 is at the center between the upper core 64 and the lower core 68.

Next, the operation of the electromagnetically driven valve 38 will be described. When the armature 60 is in contact with the upper core 64 in the electromagnetically driven valve 38, the intake valve 42 is seated on the valve seat 28. This state is maintained by supplying a predetermined exciting current to the upper coil 62. Hereinafter, the position where the intake valve 42 is seated on the valve seat 28 is referred to as the fully closed position of the intake valve 42.

When the exciting current supplied to the upper coil 62 is interrupted while the intake valve 42 is maintained at the fully closed position, the electromagnetic force acting on the armature 60 disappears. When the electromagnetic force acting on the armature 60 disappears, it is urged by the upper spring 56,
The armature 60 is displaced downward in FIG.
When a suitable exciting current is supplied to the lower coil 66 at the time when the displacement amount of the armature 60 reaches a predetermined value, the suction force for attracting the armature 60 to the lower core 68 side, that is, the intake valve 42 is moved in FIG. An attraction force displaced downward is generated.

When the above-described suction force acts on the armature 60, the armature 60 is displaced downward in FIG. 2 together with the intake valve 42 against the urging force of the lower spring 52. The displacement of the intake valve 42 continues until the armature 60 contacts the lower core 68. Hereinafter, the position of the intake valve 42 in a state where the armature 60 is in contact with the lower core 68 is referred to as a fully open position. This state is maintained by supplying a predetermined exciting current to the lower coil 66.

When the exciting current supplied to the lower coil 66 is cut off while the intake valve 42 is maintained at the fully open position, the electromagnetic force acting on the armature 60 is extinguished. When the electromagnetic force acting on the armature 60 disappears, the armature 60 is displaced upward in FIG. 2 by being urged by the lower spring 52. When a suitable exciting current is supplied to the upper coil 62 at the time when the displacement amount of the armature 60 reaches a predetermined value, a suction force for attracting the armature 60 to the upper core 64 side, that is, the intake valve 42 in FIG. A suction force that displaces upward is generated.

When the above-mentioned suction force acts on the armature 60, the armature 60 is displaced upward together with the intake valve 42 in FIG. 2 against the urging force of the upper spring 56. The displacement of the intake valve 42 is
Until it comes into contact with the upper core 64, that is, the intake valve 4
Continue until 2 reaches the fully closed position. As described above, according to the electromagnetically driven valve 38, by supplying a predetermined excitation current to the upper coil 62, the intake valve 42 can be displaced toward the fully closed position, and a predetermined excitation current is supplied to the lower coil 66. By doing so, the intake valve 42 can be displaced toward the fully open position. Therefore, according to the electromagnetically driven valve 38, by supplying the exciting current to the upper coil 62 and the lower coil 66 alternately, the intake valve 42 is
The reciprocating motion can be repeated between the fully open position and the fully closed position.

The electromagnetically driven valve 40 having the exhaust valve 44 operates in the same manner as the electromagnetically driven valve 38 described above. Therefore, according to the present embodiment, the ECU 10 alternately supplies excitation currents to the upper coil 62 and the lower coil 66 of the electromagnetically driven valves 38 and 40 at appropriate timing, respectively, so that the intake valve 42 and the exhaust valve 44 can be driven to open and close at any timing.

Referring again to FIG. 1, the internal combustion engine includes an intake manifold 80. The intake manifold 80 includes a plurality of branch pipes that communicate the surge tank 82 and each intake port 22. Each branch pipe is provided with a fuel injection valve 83. The fuel injection valve 83 injects fuel into the branch pipe according to a command signal given from the ECU 10. An intake pipe 84 communicates upstream of the surge tank 82.
A throttle valve 86 is provided in the intake pipe 84. A throttle opening sensor 87 is provided near the throttle valve 86. Throttle opening sensor 8
7 outputs a signal corresponding to the opening of the throttle valve 86 (hereinafter, referred to as a throttle opening TA) to the ECU 10. The ECU 10 detects the throttle opening TA based on the output signal of the throttle opening sensor 87. An air cleaner 88 communicates with the upstream end of the intake pipe 84. The outside air filtered by the air cleaner 88 flows into the intake pipe 84.

On the other hand, an exhaust passage 90 communicates with the exhaust port 24 of the internal combustion engine. The burned gas discharged from the combustion chamber 26 to the exhaust port 24 is discharged outside through a catalytic converter (not shown) provided in the exhaust passage 90 and a muffler. The internal combustion engine is also provided with a crank angle sensor 94. The output signal of the crank angle sensor 94 is supplied to the ECU 10. The ECU 10 determines the crank angle C based on the output signal of the crank angle sensor 94.
A and the engine speed (hereinafter referred to as engine speed NE) of the internal combustion engine.

An accelerator opening sensor 98 provided near the accelerator pedal 96 is connected to the ECU 10. The accelerator opening sensor 98 outputs a signal to the ECU 10 according to the amount of depression of the accelerator pedal 96 (hereinafter, referred to as accelerator opening AC). EC
U10 detects the accelerator opening AC based on the output signal of the accelerator opening sensor 98.

In general, in a multi-cylinder internal combustion engine, the dimensions of each cylinder vary due to manufacturing errors. Because of the variation in the dimensions, the air suction capability of each cylinder differs between the cylinders, so that the intake pressure PM in the intake stroke also differs between the cylinders. The amount of air drawn into the combustion chamber 26 during the intake stroke (the amount of intake air) increases as the intake pressure PM increases. Therefore, when the intake pressure PM differs between the cylinders, the intake air amount also differs between the cylinders.

FIG. 3 shows # 1 cylinder, # 3 cylinder, # 4 cylinder,
And a time change of the intake pressure PM of the # 2 cylinder are shown by a solid line, a broken line, a dashed line, and a two-dot chain line, respectively. FIG.
As shown in the figure, the intake pressure PM in the intake stroke differs between the cylinders, and accordingly, the intake intake air amount also differs between the cylinders. Such a difference in the amount of intake air causes a cylinder difference in the torque generated in each cylinder. As a result, the vibration of the internal combustion engine increases, causing inconvenience such as discomfort to the occupant. Further, when the intake air amount changes, the air-fuel ratio deviates from the ideal air-fuel ratio, so that the purification efficiency of the exhaust gas by the catalytic converter decreases, and the exhaust emission deteriorates.

On the other hand, the system according to the present embodiment determines the closing timing of the intake valve based on the intake pressure PM at a predetermined timing in the intake stroke, thereby setting the intake air amount of each cylinder to the target value. The feature is that it can be adjusted. In general, the higher the engine speed NE, the more rapidly the intake pressure is changed during the intake stroke because intake is performed at a higher speed. That is, the change tendency of the intake pressure in the intake stroke is determined according to the engine speed NE. Therefore, if the intake pressure PM and the engine speed NE at a certain point during the intake stroke are known, the intake pressure PM at any point after the intake stroke will be known.
Can be estimated.

The amount of air sucked into the combustion chamber 26 during the intake stroke is substantially unique depending on the product of the in-cylinder pressure when the intake valve 42 is closed and the cylinder volume at that time. Is determined. Therefore, by closing the intake valve 42 at a timing when the product of the in-cylinder pressure and the cylinder volume becomes a value corresponding to the target intake air amount, the target intake air amount can be realized.

As described above, in this embodiment, since the intake pressure sensor 83 is provided at the intake port 22 of each cylinder near the combustion chamber 26, the intake pressure PM detected by the intake pressure sensor 83 is approximately equal to the cylinder pressure. It can be considered to represent internal pressure. Therefore, the intake pressure P at a predetermined time during the intake stroke P
From M and the engine speed NE, the closing timing of the intake valve 42 for realizing the target intake air amount can be obtained. When the intake pressure sensor 25 is provided in the combustion chamber 26, the in-cylinder pressure can be accurately detected.

In this embodiment, the crank angle CA which is advanced by 90 ° CA from the top dead center at a predetermined time during the intake stroke (for example,
The relationship between the intake pressure PM and the engine speed NE at ₀ ) and the closing timing of the intake valve 42 for realizing a desired intake air amount is stored in advance as a map. FIG. 4 shows an example of such a map. As shown in FIG.
_{1, Q 2, Q 3,} . . . On the other hand, the closing timing of the intake valve 42 for obtaining each intake air amount is determined by the intake pressure PM.
And a map for the engine speed NE. In other words, the closing timing of the intake valve 42 is determined by the intake pressure P
M, the engine speed NE, and the intake air amount are obtained from a three-dimensional map. The above-described map is provided for each cylinder because the variation pattern of the in-cylinder pressure differs among the cylinders due to the above-mentioned dimensional variation of each cylinder.

In this embodiment, the torque to be generated by the internal combustion engine is calculated based on the accelerator opening AC, and the target intake air amount of each cylinder for obtaining this torque is calculated. Then, by referring to the above map, the closing timing of the intake valve 42 for realizing the target intake air amount corresponding to the accelerator opening AC is determined based on the intake pressure PM and the engine speed NE.

FIG. 5 is a flowchart of a routine executed by the ECU 10 in this embodiment to determine the closing timing of the intake valve 42 as described above. The routine shown in FIG. 5 is started at predetermined time intervals for each cylinder. When the routine shown in FIG. 5 is started, first, the process of step 100 is executed. In step 100, it is determined whether or not the cylinder targeted by the routine is in the intake stroke. As a result, if a negative determination is made, the current routine ends. On the other hand, if an affirmative determination is made in step 100, the process of step 102 is executed next.

[0038] In step 102, the crank angle CA is whether equal to a predetermined value CA ₀ or not. As a result, C
If A = CA ₀ is not established, the current routine ends. On the other hand, if CA = CA ₀ is satisfied in step 102, the process of step 104 is executed next. In step 104, the intake pressure PM and the engine speed N
E is detected.

In step 106, the accelerator opening AC is detected, and a target intake air amount is calculated based on the detected value. In step 108, by referring to the map as shown in FIG. 4, the valve closing timing T _{close The} intake valve 42 for realizing the target intake air quantity is obtained based on the intake pressure PM and the engine speed NE. Step 108
When this process is terminated, the current routine is terminated.

As described above, in the present embodiment, the intake pressure PM and the engine speed N at a predetermined time during the intake stroke of each cylinder.
E so that the intake air amount during the intake stroke becomes a target value corresponding to the accelerator opening AC.
Of the closing timing T _close it is determined. Therefore, the intake pressure P
Irrespective of the variation between the M cylinders, it is possible to prevent torque fluctuation between the cylinders and to prevent deterioration of exhaust emission caused by fluctuations in the air-fuel ratio.

As a method of suppressing the difference in the intake air amount between the cylinders, the intake air amount is measured for each cylinder, and the opening / closing timing of the intake valve 42 is adjusted so that the intake air amounts of the cylinders become equal to each other. It is possible. However, the amount of intake air in a certain intake stroke can be measured only when the intake stroke ends. For this reason, in the above-described method of actually measuring the intake air amount, if the intake air amount in a certain intake stroke deviates from a target value, the opening / closing timing of the intake valve 42 is changed in the next and subsequent intake strokes. The intake air amount is adjusted toward the target value. Therefore, it takes a certain time until the intake air amount converges to the target value.

On the other hand, in the present embodiment, at a predetermined point in the intake stroke, the closing timing of the intake valve 42 is determined such that the intake air amount in the current intake stroke reaches the target value.
Therefore, it is possible to immediately match the intake air amount in the current intake stroke with the target value in accordance with the change in the intake pressure PM. Therefore, according to the present embodiment, the torque of each cylinder can be adjusted to the target value with high responsiveness, and deterioration of exhaust emission can be more effectively prevented.

In the above embodiment, the closing timing of the intake valve 42 is determined using the intake pressure PM at a predetermined point in the intake stroke, but the intake pressure P before the start of the intake stroke is determined.
It is also possible to use M. However, in this case, since the value of the intake pressure PM greatly changes due to the pulsation from another cylinder, it is not possible to accurately estimate the intake air amount of that cylinder.

Next, a second embodiment of the present invention will be described. In the present embodiment, in the configuration shown in FIGS. 1 and 2, the internal combustion engine is operated under a predetermined condition, for example, during low load operation.
Operate in cycle operation. FIG. 6A shows changes in the intake, compression, expansion, and exhaust strokes of the # 1 to # 4 cylinders in the six-cycle operation. In FIG. 6A, arrows ↑ and ↓ indicate strokes in which the piston 18 is displaced upward and downward, respectively, without performing intake and combustion. FIG. 6B shows a change in the intake pressure PM when the internal combustion engine operates in six-cycle operation as shown in FIG. 6A. During normal operation of the four-cylinder internal combustion engine, ignition is performed in the order of # 1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder.

For example, as shown in FIG.
Is the period T₁And T_TwoAt intake stroke and pressure respectively
The contraction process is performed, and the subsequent period T_ThreeThe expansion stroke is performed.
Period T_ThreePeriod T following_FourAnd T_FiveThen, for example, intake valve 4
2 is kept closed and the exhaust valve 44 is kept open
With the piston 18 pointing upwards and downwards, respectively.
Displace. That is, the period T_FourAnd T_FiveThen, intake and fuel
Only the piston 18 reciprocates without burning
Yes, cylinder # 1 is shut down. And period T _Fivefollowed by
Period T₆After the exhaust stroke, the intake, compression,
Expansion, pause (piston rise), pause (piston fall),
And each step of exhaust is performed. In other cylinders as well,
Immediately after the expansion process involving burning, the piston 18 died.
During one round trip between the point and the top dead center, for example, the intake valve 42
Is held closed and the exhaust valve 44 is held open.
And intake, compression, expansion, rest (piston rise), rest
(Piston descent) and exhaust strokes are performed.

According to the above-described six-cycle operation, combustion is performed four times during the six strokes (three reciprocations) of the piston 18, so that the frequency of combustion is two-thirds as compared with the four-cycle operation. For this reason, in 6-cycle operation, the torque to be generated in each cylinder to obtain the same output torque as in 4-cycle operation is 3/2 times that in 4-cycle operation.
The intake air amount in the intake stroke also becomes 3/2 times. As a result, the intake pressure PM in the intake stroke increases,
Pumping loss of the internal combustion engine can be reduced.

By the way, as can be seen from FIG.
In the six-cycle operation, the intake stroke of the # 1 cylinder and the intake stroke of the # 3 cylinder, and the intake stroke of the # 2 cylinder and the intake stroke of the # 4 cylinder are performed continuously, respectively.
Between the intake stroke of the cylinder and the intake stroke of the # 2 cylinder, and #
There is an interval of one stroke between the intake stroke of the four cylinders and the intake stroke of the # 1 cylinder. In the intake stroke, the intake pressure is reduced by the intake of air from the intake port 22 into the combustion chamber 26. For this reason, as shown in FIG. 6 (B), during the periods T ₁ , T ₂ , T ₄ , and T ₅ , the intake stroke is performed in any one of the cylinders, and the intake pressure PM decreases with the progress of the intake stroke. . On the other hand, since the intake stroke is not performed in any of the cylinders in the periods T ₃ and T ₆ , the air flows into the intake port 22 through the throttle valve 86 to gradually increase the intake pressure PM. Accordingly, the intake stroke of the # 3 cylinder following the intake stroke of the # 1 cylinder and the intake stroke of the # 4 cylinder following the intake stroke of the # 2 cylinder are determined by the intake pressure PM of the # 1 cylinder and the # 2 cylinder, respectively. While the intake strokes of the # 1 and # 2 cylinders are started in a state where the intake pressure PM is higher than the intake strokes of the # 3 and # 4 cylinders. Become.

As described above, during the six-cycle operation, the intake pressure PM at the start of the intake stroke changes between the cylinders due to the uneven intervals between the intake strokes. Due to the change of the intake pressure PM, the intake air amount also changes between cylinders. In this case, inconveniences such as an increase in vibration due to torque fluctuation and deterioration of exhaust emission are caused as in the case of the first embodiment.

On the other hand, in this embodiment, the intake pressure PM is estimated based on the past history of the intake stroke, and the intake pressure PM is estimated.
The above-mentioned inconvenience is prevented by adjusting the valve closing timing of the intake valve 42 so that the change in the intake air amount accompanying the change in the intake air amount is compensated. FIG. 7 is a flowchart of a routine executed by the ECU 10 to determine the closing timing of the intake valve 42 in the present embodiment. FIG. 8 is a diagram showing the start timing of the routine shown in FIG. As shown in FIG. 8, in the routine shown in FIG. 7, the intake stroke starts at the 180 ° CA interval immediately before the top dead center or the bottom dead center of the piston 18 of each cylinder, that is, in any cylinder during normal operation. It is started at the timing immediately before the start. A period from the start of the current routine to the start of the present routine next is referred to as a target period of the current routine. For example, the target period of the routine started at the time shown in FIG. 7 is from time to time. When the routine shown in FIG. 7 is started, first, the process of step 100 is executed.

In step 150, it is determined whether or not any cylinder performs the intake stroke in the target period of the current routine. As a result, if it is determined that the intake stroke is not performed in any of the cylinders (at the timing shown in FIG. 8), the current routine ends without any processing being performed. On the other hand, when it is determined in step 150 that the intake stroke is performed in any one of the cylinders, the process of step 152 is performed next.

In step 152, it is determined whether or not the intake stroke has been performed during the target period of the previous routine. As a result, when it is determined that the intake stroke has been performed during the target period of the previous routine (at the timing shown in FIG. 8), it is determined that the intake pressure PM is the same as in the normal four-cycle operation. Then, the process of step 154 is executed.

In step 154, the intake valve 42 is set for the cylinder in which the intake stroke is performed in the target period of the current routine.
Of the closing timing T _close is set to the reference closing timing T _base. The reference valve closing timing T _base is 180
゜ When performed at CA intervals, that is, during normal four-cycle operation, this is the closing timing of the intake valve 42 such that a required intake air amount corresponding to the accelerator opening AC is obtained, and is represented by the crank angle CA. You.

As the closing timing of the intake valve 42 becomes earlier than the bottom dead center, the pumping loss decreases because the throttle opening TA for obtaining a constant intake air amount increases. Therefore, in the present embodiment, the reference valve closing timing T
By setting the _base earlier than the bottom dead center, pumping loss is reduced. When the process of step 154 ends, the current routine ends.

On the other hand, if it is determined in step 152 that the intake stroke has not been performed during the target period of the previous routine (the timing shown in FIG. 8 or), the intake period is determined during the target period of the previous routine. It is determined that the intake pressure PM is higher than when the stroke is performed, that is, as compared with the normal four-cycle operation. In this case, it is determined that the amount of intake air should be reduced in order to compensate for the effect of the increase in the intake pressure PM, and then the process of step 156 is performed.

In step 156, a correction value ΔT of the closing timing T _close of the intake valve 42 in the intake stroke is obtained based on the engine speed NE and the throttle opening TA.
As described above, since the valve closing reference time T _base of the intake valve 42 is set earlier than the bottom dead center, the earlier the valve closing time, the smaller the intake air amount. Therefore, the correction value ΔT
Is obtained as a correction value to advance the valve closing timing from the reference timing T _base .

As described above, when the intake stroke is not performed in the target period of the previous routine, the intake pressure PM is determined by the amount of air flowing into the intake port 22 and the amount of air flowing out of the intake port 22. Now, if the throttle opening TA is sufficiently large and a sufficient amount of air can flow into the intake port 22, that is, if the air drawn out by each cylinder can be supplied in the cycle, the intake pressure PM is immediately recovered. In this case, ΔT is 0. Similarly, when the engine speed NE is small and the suction amount of each cylinder is small, the intake pressure PM recovers immediately, and ΔT becomes zero.

On the other hand, when the throttle opening TA is small,
Alternatively, when the engine speed NE is high, the air sucked by each cylinder cannot be immediately supplied to the intake port 22, so that the intake stroke is continuously performed and the previous intake stroke is not performed. There is a large difference in the intake pressure PM between the case where it is not performed. Therefore, the throttle opening TA
Is smaller and the engine speed NE is larger, ΔT
ΔT is determined by referring to a map prepared in advance so that is larger.

In step 158 following step 156, the valve closing timing T _close of the intake valve 42 is set to (T _base -ΔT).
Is set to When the process of step 112 is completed, the current routine ends. As described above, in the present embodiment, during the six-cycle operation of the four-cylinder internal combustion engine, based on whether the intake stroke was performed immediately before the intake stroke of each cylinder, that is, based on the history of the intake stroke, closing timing of the intake valve 42 T _{close the} is corrected. For this reason, according to the present embodiment, it is possible to compensate for the change in the intake air amount PM depending on the history of the intake stroke and to eliminate the difference in the intake air amount among the cylinders. It is possible to prevent the increase and the deterioration of the exhaust emission.

In the second embodiment, the case where the reference valve closing timing T _base of the exhaust valve 42 is set earlier than the bottom dead center in order to reduce the pumping loss has been described. Valve closing reference time T
It is also possible to set _base . FIG. 9 shows that the valve closing reference time T _{base at} which the intake air amount becomes the maximum is set at the engine speed N.
FIG. 9 is a diagram showing a function of E. In the low rotation speed operation region of the internal combustion engine, after the piston 18 has passed the bottom dead center, the piston 18 subsequently rises, so that air is discharged from the cylinder. Therefore, as shown in FIG. 9, in the region where the engine speed NE is equal to or less than the predetermined value N ₀ , the valve closing reference time T _base that maximizes the intake air amount coincides with the bottom dead center. On the other hand, when the engine speed increases, the valve opening time of the intake valve 42 decreases, so that air is sucked into the cylinder even after the piston 18 has passed the bottom dead center. Therefore, as shown in FIG. 9, in the region where the engine rotational speed NE exceeds a predetermined value N _0, N
The valve closing reference time T _base increases as E increases. When the valve closing reference time T _base is set such that the intake air amount is maximized as shown in FIG. 9, the valve closing timing of the intake valve 42 is advanced from the valve closing reference time T _base , or Even if it is delayed, the amount of intake air can be reduced.

As described above, in the low rotation speed region, the intake air amount becomes maximum when the intake valve 42 is closed at the bottom dead center. For this reason, by setting the valve closing reference time T _base after the bottom dead center, the throttle opening TA for obtaining a constant intake air amount is increased, thereby reducing pumping loss in a low rotation speed region. It is also possible. However, in this case, in the low rotation speed region, the intake air amount decreases as the closing timing of the intake valve 42 is delayed, whereas in the high rotation speed region, the intake air amount decreases as the closing timing of the intake valve 42 advances. The amount is smaller. Therefore, in the intermediate region between these two regions, the intake air amount cannot be sufficiently adjusted by the closing timing of the intake valve 42. Further, since the intake valve 42 is driven by the natural vibration of the spring-mass system of the electromagnetically driven valve 38, the time required for the intake valve 42 to be displaced from the fully open position to the fully closed position can be reduced to a certain value or less. Can not. Therefore, in the high rotation speed region, there is a possibility that the closing timing of the intake valve 42 cannot be advanced.

For these reasons, as a method of reducing the pumping loss, the reference time T
It is desirable to set _base before the bottom dead center. By the way, in the second embodiment, the case where the present invention is applied to the four-cylinder internal combustion engine and this internal combustion engine operates in six-cycle operation has been described. However, the present invention is not limited to this. For a multi-cylinder internal combustion engine having an arbitrary number of cylinders, such as a six-cylinder type, an eight-cylinder type, etc. Applicable.

FIGS. 10 and 11 show two cylinders of a six-cylinder internal combustion engine.
An example of one operation mode is shown. In the internal combustion engine whose operation mode is shown in FIGS. 10 and 11, the ignition sequence during normal operation is # 1 cylinder → # 5 cylinder → # 3 cylinder → # 6 cylinder → # 2 cylinder → # 4 cylinder. It is assumed that FIG.
(A) shows the relationship between # 3 cylinder and # in a six-cylinder internal combustion engine.
The change of the stroke of each cylinder in the operation mode in which the four cylinders are always stopped and the other cylinders are operated in four cycles is shown. In addition,
At the top of FIG. 10, the period during which the intake stroke is started in any of the cylinders is indicated by a circle. Further, FIG.
7 shows changes in the intake pressure PM in this operation mode.

During the normal operation of the six-cylinder internal combustion engine, the intake stroke is started sequentially at intervals of 120 ° CA in each cylinder in accordance with the above-described ignition sequence. On the other hand, in the operation mode shown in FIG. 10, since the # 3 cylinder and # 4 cylinder are always stopped, the intake stroke is not performed in these cylinders. Therefore, for example, as shown in FIG. 10B, the intake strokes of the # 5 cylinder and the # 2 cylinder have the intake pressure PM due to the intake strokes of the # 1 cylinder and the # 6 cylinder performed immediately before. In contrast to the start in the lowered state, the intake strokes of the # 6 cylinder and # 1 cylinder are not performed in the immediately preceding # 3 cylinder and # 6 cylinder because the intake stroke is not performed as shown by the timings and. , # 5 and # 2 cylinders are started with a higher intake pressure PM. Thus, FIG.
In the operation mode shown in (1), the intake pressure PM in the intake stroke changes depending on the cylinder. Therefore, as in the second embodiment, by adjusting the closing timing of the intake valve in accordance with whether or not the intake stroke was performed immediately before, the intake air amount due to the change of the intake pressure PM between the cylinders is reduced. Can be compensated, thereby preventing an increase in vibration and deterioration in emission due to torque fluctuation.

FIG. 11A shows that in a six-cylinder internal combustion engine, cylinders # 1, # 3, and # 2 are operated in four cycles in the same manner as in normal operation, and cylinders # 5, # 6, For the # 4 and # 4 cylinders, the change of the stroke of each cylinder in the operation mode of operating in eight cycles is shown. At the top of FIG. 11A, a period during which the intake stroke is started in any of the cylinders is indicated by a circle. FIG. 11B shows a change in the intake pressure PM in this operation mode.

In the operation mode shown in FIG.
The # 3 and # 2 cylinders operate in four cycles of intake, compression, expansion and exhaust, whereas the # 5, # 6 and # 4 cylinders operate after the expansion (combustion) stroke. ,
The piston 18 makes two reciprocations between the bottom dead center and the top dead center without performing intake and combustion. That is, # 5 cylinder, # 6
The cylinder and the # 4 cylinder are stopped for four cycles after the end of the expansion stroke. Therefore, for example, as shown by the timings in FIG. 11B, respectively, the intake stroke of the # 2 cylinder immediately after the deactivation of the # 6 cylinder, the intake stroke of the # 3 cylinder immediately after the deactivation of the # 5 cylinder, and # 4 The intake stroke of the # 1 cylinder immediately after the cylinder is stopped is started in a state where the intake stroke is not performed immediately before the cylinder is stopped. Therefore, these intake strokes are compared with the case where the paused stroke is performed in the immediately preceding cylinder. The process is started in a state where the pressure PM is high. Further, as can be seen from the intake pressure PM at the timings (I) and (II) in FIG.
The intake stroke of the five cylinders is started in a state where the intake pressure PM is higher than that of the intake stroke of the # 3 cylinder that is performed subsequent to the intake stroke of the continuous # 1 cylinder and the # 5 cylinder.

As described above, in the operation mode shown in FIG. 11, when the immediately preceding intake stroke is stopped, when the immediately preceding intake stroke is performed after the suspension of the intake stroke, and
It changes depending on whether the intake stroke is performed two consecutive times immediately before. Therefore, the closing timing T _{clos of the} intake valve 42 according to the past history of such an intake stroke.
By adjusting _e , it is possible to compensate for the difference between the cylinders in the intake air amount due to the change in the intake pressure PM, thereby preventing an increase in vibration and a deterioration in emission due to torque fluctuation. it can.

The second embodiment and FIGS. 10 and 1
In the example of the operation mode shown in FIG.
Although the valve 2 is kept closed and the exhaust valve 44 is kept open, both the intake valve 42 and the exhaust valve 44 may be kept closed. In each of the above embodiments, the intake air amount is adjusted based on the closing timing of the intake valve 42 because the intake air amount is more dependent on the closing timing than the opening timing of the intake valve 42. . However, since the intake air amount also depends to some extent on the opening timing of the intake valve 42, it is necessary to adjust the intake air amount based only on the opening timing of the intake valve 42 or on both the closing timing and the opening timing. It may be.

In the above embodiment, the ECU 10
By executing the routine shown in FIG. 5 or FIG. 7, the intake valve opening / closing timing determining means described in the claims is realized.

[0069]

According to the first aspect of the present invention, the opening / closing timing of the intake valve is determined for each cylinder in accordance with the intake pressure.
Even when the intake pressure differs for each cylinder, the intake air amount of each cylinder can be set as the target value. According to the second aspect of the present invention, by determining the opening / closing timing of the intake valve in accordance with the intake pressure at a predetermined timing during the intake stroke, the intake air amount can be immediately adjusted in response to a change in the intake pressure. Can be adjusted.

According to the third aspect of the invention, by adjusting the opening / closing timing of the intake valve according to the engine speed, the intake air amount of each cylinder can be adjusted more accurately.
According to the fourth aspect of the invention, the intake pressure can be detected by the pressure sensor provided in the intake pipe or the cylinder. According to the fifth aspect of the present invention, in the operating state of the internal combustion engine in which the intervals of the intake strokes are unequal, the intake pressure is estimated based on the past history of the intake strokes, so that in this operating state, The intake air amount of each cylinder can be set as the target value.

According to the sixth aspect of the present invention, the intake air amount of each cylinder can be more accurately adjusted by adjusting the opening / closing timing of the intake valve according to the engine speed and the throttle opening. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an internal combustion engine to which a control device for an electromagnetically driven valve according to an embodiment of the present invention is applied.

FIG. 2 is a cross-sectional view illustrating an entire configuration of an electromagnetically driven valve provided in the internal combustion engine.

FIG. 3 is a diagram showing a difference in intake pressure PM between cylinders.

FIG. 4 is a diagram showing an example of a map for determining a closing timing of an intake valve based on an intake pressure PM and an engine speed NE in the first embodiment of the present invention.

FIG. 5 is a flowchart of a routine executed by an ECU to determine a closing timing of an intake valve in the embodiment.

FIG. 6A is a diagram showing a change in the stroke of each cylinder when the four-cylinder internal combustion engine operates in six-cycle operation. FIG. 6B is a diagram illustrating a change in the intake pressure PM during the six-cycle operation.

FIG. 7 is a flowchart of a routine executed by an ECU to determine a closing timing of an intake valve in a second embodiment of the present invention.

FIG. 8 is a diagram showing a start timing of the routine shown in FIG. 7;

[9] and the engine rotational speed NE, a diagram showing the relationship between the reference closing timing T _{ba se} of the exhaust valve in the case of the maximum intake air quantity.

FIG. 10A is a diagram showing a change in stroke of each cylinder in a first example of an operation mode in which intervals between intake strokes are unequal in a six-cylinder internal combustion engine. FIG. 10 (B)
FIG. 7 is a diagram showing a change in intake pressure PM in the present operation mode.

FIG. 11A is a diagram showing a change in the stroke of each cylinder in a second example of the operation mode in which the intervals between the intake strokes are unequal in a six-cylinder internal combustion engine. . FIG. 11 (B)
FIG. 7 is a diagram showing a change in intake pressure PM in the present operation mode.

[Explanation of symbols]

 10 ECU 38, 40 Electromagnetic drive valve 42 Intake valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02B 75/02 F02B 75/02 Z

Claims (6)

[Claims] 1. An internal combustion engine having an electromagnetically driven valve in which at least an intake valve is constituted by an electromagnetically driven valve, wherein intake air is supplied to each cylinder in accordance with the intake pressure such that the intake air amount of each cylinder becomes a target value. An internal combustion engine having an electromagnetically driven valve, comprising an intake valve opening / closing timing determining means for determining a valve opening / closing timing. 2. The internal combustion engine having an electromagnetically driven valve according to claim 1, wherein the intake valve opening / closing timing determining means determines the opening / closing timing of the intake valve according to the intake pressure at a predetermined timing during an intake stroke. organ. 3. An internal combustion engine having an electromagnetically driven valve according to claim 2, wherein said intake valve opening / closing timing determining means adjusts the opening / closing timing of the intake valve according to the engine speed. 4. The internal combustion engine having an electromagnetically driven valve according to claim 1, wherein the intake pressure is detected by a pressure sensor provided in an intake pipe or a cylinder. . 5. The intake valve opening / closing timing determining means according to claim 1, wherein in an operating state of the internal combustion engine in which intervals between intake strokes are unequal,
2. The internal combustion engine having an electromagnetically driven valve according to claim 1, wherein the intake pressure is estimated based on a past history of the intake stroke. 6. The electromagnetically driven valve according to claim 5, wherein the intake valve opening / closing timing determining means adjusts the opening / closing timing of the intake valve according to at least one of an engine speed and a throttle opening. Internal combustion engine.