JPH05106449A - Control device of six-cylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the suction efficiency and the engine output along a wide scope of rotation frequency area. CONSTITUTION:The control device of a V-type six-cylinder engine 1 is provided with variable valve timing mechanisms 51 and 52, a rotation frequency sensor 71, an absolute pressure sensor 72, a section area expanding part 44 on the way of an exhaust passage C, an exhaust control valve 46 in a communication pipe 45, and a CPU 74 to control the variable valve timing mechanisms 51 and 52 and the exhaust control valve 46. The CPU 74 opens the exhaust control valve 46 when the engine rotation frequency NE by the rotation frequency sensor 71 is at the preset first rotation frequency alpha or higher, or less than the second rotation frequency beta which is lower than the first rotation frequency alpha, so as to set the length of the propagation path of the pressure wave and the negative pressure wave at a specific length. And when the engine rotation frequency NE is higher than the second rotation frequency beta and lower than the first rotation frequency alpha, the CPU 74 closes the exhaust control valve 46, so as to make the length of the propagation path longer than a specific length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a 6-cylinder internal combustion engine equipped with a variable valve timing mechanism for adjusting the opening / closing operation timing of intake / exhaust valves.

[0002]

2. Description of the Related Art Conventionally, intake and
There is a variable valve timing device that allows the opening / closing timing (valve timing) of an exhaust valve to be advanced or delayed. With this device, low-speed and high-load operating conditions,
The valve timing is switched between the low speed light load operation state including the idling operation and the high speed operation state. That is,
If the operating state of the engine is the former state, the closing timing of the intake valve is advanced to increase the valve overlap to prevent blowback of intake air and obtain high output. If the engine is operating in the latter state, the closing timing of the intake valve is delayed to reduce the valve overlap to obtain stable combustion and high output.

However, since the exhaust valve and the intake valve are both open at the time of valve overlap, when the combustion gas remaining in the cylinder flows back to the intake port, the actual intake air amount during the intake stroke decreases. , Intake efficiency decreases. This phenomenon becomes a problem especially at low speed and high load operation where the valve overlap is enlarged.

Therefore, the present applicant has previously proposed a pressure wave caused by blowdown in a cylinder that explodes this time (a phenomenon in which combustion gas having a high pressure in the combustion chamber is immediately discharged to the exhaust port immediately after the exhaust valve is opened). Has proposed a technology that solves the above-mentioned problems by utilizing (Japanese Patent Application No. 2-23638).
No.).

In this technique, as shown in FIG. 12, exhaust branch pipes 102, 103, 104 and 105 are connected to the cylinders # 1, # 2, # 3 and # 4 of a four-cylinder internal combustion engine 101. The exhaust branch pipe 102 and the exhaust branch pipe 105 merge on the downstream side to form a first merge pipe 106, and the exhaust branch pipe 103 and the exhaust branch pipe 104 merge on the downstream side to form a second merge pipe 107. Has been done. Furthermore, the two confluent pipes 106 and 107 are joined together at a gathering portion 108 to form an exhaust main pipe 109. The cross-sectional area of the collecting portion 108 is larger than the cross-sectional areas of the first merging pipe 106 and the second merging pipe 107,
In this collecting portion 108, the direction of the pressure wave is reversed to form a negative pressure wave toward the exhaust valve.

On the upstream side of the collecting section 108,
The first merging pipe 106 and the second merging pipe 107 include a communication pipe 110.
The exhaust control valve 1 is connected in the communication pipe 110.
11 is provided so that it can be opened and closed. This exhaust control valve 11
When 1 is opened, the first merging pipe 106 communicates with the second merging pipe 107 via the communication pipe 110, so that the cross-sectional area of the first merging pipe 106 sharply increases at the connecting portion with the communication pipe 110. Expanded. Therefore, even when the exhaust control valve 111 is opened, the direction of the pressure wave due to the blowdown is reversed, and the negative pressure wave is directed to the exhaust valve.

The variable valve timing device 112
When the opening / closing timing of the intake valve is advanced by the valve (when the valve overlap is enlarged), the exhaust control valve 111 is controlled to open / close according to the operating state of the engine, and the direction of the pressure wave generated by blowdown Is reversed and the negative pressure wave reaches the exhaust valve (hereinafter,
The length of the propagation path) is switched. That is, by closing the exhaust control valve 111 during low engine speed, the pressure wave due to blowdown in the cylinder that explodes this time is reversed at the collecting portion 108, and the propagation path is lengthened. Also,
By opening the exhaust control valve 111 at the time of middle-high rotation of the engine, the pressure wave due to the blowdown in the cylinder that explodes this time is reversed in the communication pipe 110 portion, and the propagation path is shortened. As a result, a negative pressure wave reaches the exhaust valve during valve overlap, sucks the combustion gas in the combustion chamber from the exhaust port, and increases fresh air flowing into the cylinder from the intake port. As a result, the intake efficiency is improved.

[0008]

However, when the above prior art is applied to a 6-cylinder internal combustion engine, the interval from the ignition timing in the cylinder that explodes this time to the ignition timing in the cylinder that explodes next time is a 4-cylinder internal combustion engine. The crank angle is 180 degrees, but in the 6-cylinder internal combustion engine, the crank angle is 120 degrees. Therefore, the negative pressure wave due to the blowdown in the cylinder that exploded this time and the negative pressure wave due to the blowdown in the cylinder that will explode next time have different effects on the negative pressure wave due to the blowdown in the cylinder that exploded last time. Therefore, it becomes necessary to change the length of the propagation path between the 6-cylinder internal combustion engine and the 4-cylinder internal combustion engine. Therefore, even if the conventional technique is directly applied to the 6-cylinder internal combustion engine, the output of the internal combustion engine cannot be improved to a sufficient level.

That is, in the low speed range of a four-cylinder internal combustion engine, the next cylinder explodes after a crank angle of 180 degrees has elapsed from the explosion of a predetermined cylinder, and the blowdown occurrence time in the next exploding cylinder explodes this time. It exactly overlaps the valve overlap in the cylinder. Therefore, the negative pressure wave due to blowdown in the cylinder that will explode next time will reach after the valve overlap starts in the cylinder that explodes this time. On the other hand, in the low speed range of the 6-cylinder internal combustion engine, at the time of valve overlap of the cylinder that explodes this time, a negative pressure wave due to blowdown in the cylinder that explodes next time can reach the exhaust valve of the cylinder that explodes this time. It is possible. Therefore, in the case of a 6-cylinder internal combustion engine, it is possible to improve the performance such as torque in the low speed range by positively utilizing the negative pressure wave due to the blowdown in the cylinder that will explode next time.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to explode a negative pressure wave due to blowdown in a cylinder that will explode next time at the time of valve overlap of the cylinder that explodes this time. It is an object of the present invention to provide a control device for a 6-cylinder internal combustion engine that can reach the exhaust valve of a cylinder and improve intake efficiency and engine output.

[0011]

In order to achieve the above-mentioned object, the present invention, as shown in FIG.
2) provided in an internal combustion engine M3 having the same internal combustion engine M3
Variable valve timing mechanism for adjusting the valve timing of at least one of an intake valve that opens and closes an intake passage to the combustion chamber and an exhaust valve that opens and closes two exhaust passages M4 and M5 from the combustion chamber M6
And an operating state detection means M7 for detecting the operating state of the internal combustion engine M3, and a target valve overlap of the valve is calculated according to the operating state of the internal combustion engine M3 by the operating state detection means M7, and an actual valve over Timing control means M for controlling the variable valve timing mechanism M6 so that the lap becomes the target valve overlap.
8 and the direction of the pressure wave that is provided in the exhaust passages M4, M5, is generated by the blowdown in the explosion / exhaust stroke in each cylinder (M1, M2), and propagates in the exhaust passages M4, M5. Reverse the cylinder (M1, M2)
Of the cross-sectional area enlarged portion M9 for making a negative pressure wave toward the exhaust valve, and a communication passage M10 that communicates between the exhaust passages M4 and M5 on the upstream side of the cross-sectional area enlarged portion M9. An exhaust control valve M11 for allowing or blocking the reversal of the direction of the pressure wave in the same communication passage M10 by the opening / closing operation, a rotation speed detection means M12 for detecting the engine rotation speed of the internal combustion engine M3, and an explosion at this time. Negative pressure wave due to blowdown in cylinder M1 or cylinder M that will explode next time
In order to make the negative pressure wave based on the blowdown at 2 reach the exhaust valve of the cylinder M1 that explodes this time when the variable valve timing mechanism M6 overlaps the valve, the engine speed by the engine speed detecting means M12 is predetermined. When the rotational speed is equal to or higher than the first rotational speed and is equal to or lower than the second rotational speed lower than the first rotational speed, the exhaust control valve M11 is opened to propagate the pressure wave and the negative pressure wave. Is set to a predetermined length, and the exhaust control valve M11 is closed when the engine speed by the engine speed detection means M12 is higher than the second speed and lower than the first speed. Thus, the opening / closing control means M for making the length of the propagation path longer than the predetermined length.
13 and 13.

[0012]

When the internal combustion engine M3 is operating, its operating state is detected by the operating state detecting means M7 and the engine speed is detected by the rotational speed detecting means M12. The timing control means M8 calculates the target valve timing of the valve according to the operating state of the internal combustion engine M3 by the operating state detecting means M7, and the variable valve timing mechanism M6 is set so that the actual valve timing becomes the target value. Control the valve timing of the valve by.

Such a variable valve timing mechanism M6
When the valve overlaps due to
2) The combustion gas remaining inside may flow backward to the intake passage side. However, in the present invention, each cylinder (M1,
The backflow of the combustion gas to the intake passage side is prevented by using the pressure wave generated by the blowdown in the explosion / exhaust stroke in M2).

That is, the opening / closing control means M13 has a first engine rotation speed determined by the rotation speed detection means M12 which is predetermined.
The exhaust control valve M11 is opened when the rotational speed is equal to or higher than the second rotational speed or equal to or lower than the second rotational speed lower than the first rotational speed. Then, the direction of the pressure wave due to the blowdown is reversed in the communication passage M10 portion, and the pressure wave becomes a negative pressure wave toward the exhaust valve of the cylinder M1 that exploded this time. At this time, the propagation paths of the pressure wave and the negative pressure wave have a predetermined length.

The opening / closing control means M13 closes the exhaust control valve M11 when the engine speed detected by the rotation speed detection means M12 is higher than the second speed and lower than the first speed. Let me speak. Then, the direction of the pressure wave due to the blowdown is reversed at the cross-sectional area enlarged portion M9, and the pressure wave becomes a negative pressure wave toward the exhaust valve of the cylinder M1 that exploded this time. The length of the propagation path at this time is longer than the predetermined length.

Such a variable valve timing mechanism M6
When the on-off control valve M11 is opened and closed and the length of the propagation path is switched in accordance with the engine speed, the negative pressure wave based on the blowdown in the cylinder M1 that explodes this time or the cylinder M2 that explodes next time occurs. It is possible to cause the negative pressure wave based on the blowdown in (1) to reach the exhaust valve of the cylinder M1 that explodes this time.

Then, as described above, the negative pressure wave reaching the exhaust valve at the time of valve overlap attempts to suck out the combustion gas in the cylinder M1 that has exploded this time to the exhaust passage M5 side. Therefore, the combustion gas is prevented from flowing back to the intake passage side. As a result, the reduction of the substantial intake air amount and the reduction of the intake efficiency due to the backflow during the intake stroke are prevented over the entire engine speed range, the residual gas amount in the combustion chamber is reduced, and the intake efficiency is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. FIG. 2 is a schematic view of a V-type 6-cylinder engine 1 as a 6-cylinder internal combustion engine as seen from above.
A crankshaft 3 extending in the front-rear direction (left-right direction in the drawing) is rotatably supported by a cylinder block 2 of the engine 1, and a crank pulley 4 is integrally rotatably attached to a front end of the crankshaft 3. The cylinder block 2 is branched in a V shape around the crankshaft 3, the left side portion (lower side portion of the figure) constitutes a left bank 5, and the right side portion (upper side portion of the figure) constitutes a right bank 6. is doing.

In the right bank 6, the first cylinder # 1, the third cylinder # 3, and the fifth cylinder # 5 are sequentially arranged in parallel. In the right bank 6, above each of the cylinders # 1, # 3, # 5, an intake side camshaft 9 and an exhaust side camshaft 10 that extend in the front-rear direction in close proximity to each other are rotatably supported. There is. Two cams 9a and 10a are formed on each of the camshafts 9 and 10 for each cylinder.

In the left bank 5, the second cylinder # 2, the fourth cylinder # 4 and the sixth cylinder # 6 are arranged in parallel in this order. In the left bank 5, above the respective cylinders # 2, # 4, # 6, an intake side camshaft 7 and an exhaust side camshaft 8 extending in the front-rear direction in a state of being close to each other are rotatably supported. There is. Two cams 7a and 8a are formed for each cylinder on both camshafts 7 and 8.

The following structure is adopted to transmit the rotation of the crankshaft 3 to the camshafts 7 and 8 in the left bank 5 and the camshafts 9 and 10 in the right bank 6. That is, cam pulleys 11 and 12 are integrally rotatably attached to the front ends of the exhaust side cam shafts 8 and 10 in the left and right banks 5 and 6, respectively. A timing belt 13 is wound around the cam pulleys 11 and 12 and the crank pulley 4, and the rotation of the crankshaft 3 is transmitted to the exhaust side camshafts 8 and 10 via the timing belt 13. In addition, the drive gears 14 are provided at the rear end portions of the exhaust side camshafts 8 and 10 in the left and right banks 5 and 6, respectively.
15 is attached so as to be able to rotate integrally, and driven gears 16 and 17 are provided at the rear ends of the intake-side camshafts 7 and 9, respectively. The drive gears 14 and 15 and the driven gears 16 and 17 mesh with each other. Therefore, when the exhaust side camshafts 8 and 10 rotate, the intake side camshafts 7 and 9 rotate in opposite directions.

Next, the intake side camshafts 7 and 9 and the exhaust side camshafts 8 and 10 in the left and right banks 5 and 6, respectively.
The valve operating mechanism and the like driven by will be described. Figure 3
As shown in FIG. 3, in the right bank 6, first to third cylinders # 1, # 3 and # 5 (only the first cylinder # 1 is shown in the drawing) are arranged in parallel in a direction perpendicular to the plane of the drawing. Each cylinder # 1, # 3
A piston 18 that moves up and down as the crankshaft 3 rotates is housed in # 5. Piston 1
A combustion chamber 19 is formed above 8 and an intake passage B and an exhaust passage C communicate with the combustion chamber 19. Combustion chamber 19
The portion communicating with the intake passage B is an intake port 21, and this intake port 21 is opened and closed by an intake valve 23 attached to a cylinder head 22 so as to be vertically movable. Further, a communication portion between the combustion chamber 19 and the exhaust passage C is an exhaust port 24, and the exhaust port 24 is attached to the cylinder head 22 so as to be vertically movable.
It is opened and closed by 5.

Compressed valve springs 26, 27, valve lifters 28, 29 and the like are mounted on the intake valve 23 and the exhaust valve 25. One valve spring 26 urges the intake valve 23 upward so that the valve lifter 28 always presses the cam 9a on the intake side cam shaft 9. The other valve spring 27 urges the exhaust valve 25 upward so that the valve lifter 29 always presses the cam 10a on the exhaust side camshaft 10. Both of these urging directions are directions in which the intake port 21 and the exhaust port 24 are closed.

Therefore, when the rotation of the crankshaft 3 is transmitted to the cam pulley 12 via the timing belt 13 (see FIG. 2), the exhaust side camshaft 10 and the intake side camshaft 9 rotate. Along with this, when the cams 10a and 9a periodically push down the valve lifters 29 and 28 against the urging force of the valve springs 27 and 26, these valve lifters 29 and 28 are exhausted by the exhaust valve 25.
Also, the intake valve 23 is pressed downward to open and close.

In the intake passage B, the intake port 21
A fuel injection valve 31 is attached in the vicinity of. Also,
In the intake passage B upstream of the fuel injection valve 31, a throttle valve 33 that opens and closes in association with the operation of the accelerator pedal 32 is provided. The amount of intake air into the intake passage B is adjusted by opening / closing the throttle valve 33. Further, a surge tank 34 for smoothing the pulsation of intake air is arranged between the fuel injection valve 31 and the throttle valve 33.

A mixture of the fuel injected from the fuel injection valve 31 and the outside air introduced into the intake passage B is introduced into the combustion chamber 19 through the intake port 21 when the intake valve 23 is opened. It A spark plug 35 is attached to the cylinder head 22 in order to ignite the air-fuel mixture introduced into the combustion chamber 19. This spark plug 35
Are driven based on the ignition signal distributed by the distributor 36. The distributor 36 is for distributing the high voltage output from the igniter 37 to the spark plug 35 in synchronization with the crank angle of the engine 1.

The air-fuel mixture introduced into the combustion chamber 19 is exploded and burned by the ignition of the ignition plug 35, and the engine 1 is passed through the piston 18 and the crankshaft 3 and the like.
The driving force of is obtained. In this embodiment, the crank angle is 12
At every 0 degree, the ignition by the spark plug 35 causes the ignition of the first cylinder # 1,
The second cylinder # 2, the third cylinder # 3, the fourth cylinder # 4, the fifth cylinder # 5, and the sixth cylinder # 6 are performed in this order.

Combustion gas is produced by burning the air-fuel mixture in the combustion chamber 19 as described above. This combustion gas is
When the exhaust valve 25 is opened, it is discharged from the exhaust port 24 to the outside through the exhaust passage C. Exhaust pulsation composed of various pressure waves propagates toward the exhaust passage C due to the discharge of the combustion gas. The largest pressure wave among the exhaust pulsations is the pressure wave due to blowdown. In this blowdown, the combustion gas in the combustion chamber 19 whose pressure is higher than that of the exhaust port 24 in the explosion / exhaust stroke is vigorously exhausted to the exhaust port 24 immediately after the opening of the exhaust valve 25, and the exhaust port is exhausted. This is a phenomenon in which the pressure of 24 rapidly rises. Since the engine 1 of this embodiment has 6 cylinders, this blowdown occurs every 120 degrees in crank angle.

Since the internal structure of the left bank 5 is basically the same as that of the right bank 6 described above, its explanation is omitted here. In addition to the basic configuration of the engine 1 as described above,
In this embodiment, the variable valve timing mechanisms 51 and 52 for adjusting the opening / closing timing of the intake valve 23 are
It is mounted on each of the left and right banks 5 and 6. Next, the variable valve timing mechanisms 51 and 52 will be described in detail. However, since the mechanisms 51 and 52 have basically the same configuration, only the variable valve timing mechanism 52 mounted on the right bank 6 side will be described here. To do.

As shown in FIG. 4, the intake side camshaft 9
The driven gear 17 is provided at the rear end (right end in FIG. 4). External teeth 17a are formed on the outer circumference of the driven gear 17, and the external teeth 17a mesh with the drive gear 15 of the exhaust side camshaft 10. A boss 17b is formed on the inner peripheral portion of the driven gear 17, and the driven gear 17 is fitted to the outer periphery of the rear end portion of the intake camshaft 9 at the boss 17b so as to be relatively rotatable.

At the rear end of the intake-side camshaft 9, a casing 53 having an open front is fastened and fixed by a bolt 54, and the casing 53 and the driven gear 17 form an annular space 55. A ring gear 56 having a substantially annular shape is arranged in the annular space 55, and the ring gear 56 connects the boss 17 b of the driven gear 17 and the casing 53. Helical teeth 56a and 56b are formed on the inner and outer circumferences of the ring gear 56,
The ring gear 56 is rotatable relative to the intake camshaft 9 by moving in the axial direction. The helical teeth 56 a and 56 b are the bosses 1 of the driven gear 17.
The helical teeth 17c on the outer circumference of 7b and the helical teeth 53a on the inner circumferential surface of the casing 53 mesh with each other.

Therefore, the rotation of the crankshaft 3 causes the cam pulley 12, the exhaust side camshaft 10 and the drive gear 15 to rotate.
By being transmitted to the driven gear 17 via the gear (see FIG. 2), the driven gear 17 connected by the ring gear 56 and the casing 53 are integrally rotated, and the intake side camshaft 9 is rotationally driven.

In the annular space 55 surrounded by the driven gear 17 and the casing 53, the rear side of the ring gear 56 is a pressure chamber 57. Pressurized oil is supplied to the pressure chamber 57 through oil passages 58 and 59 formed in the intake side camshaft 9, the cylinder head 22, and the like. Similarly, in the annular space 55, the front side of the ring gear 56 is a spring chamber 61.
A balancing compression coil spring 62 that faces the pressurized oil is housed.

A hydraulic control valve 63 is provided between the oil passage 59 and a pressurized oil source such as an oil pump. The hydraulic control valve 63 has three ports, and the port on the inlet side is connected to the pressurized oil source via the oil supply passage 64. Further, one port on the outlet side is connected to the pressure chamber 57 via the oil passages 59 and 58, and the other port is connected to an oil pan via an oil return passage 65.

When the hydraulic control valve 63 is opened during the operation of the engine 1, the oil passages 58 and 59 are communicated with the oil supply passage 64 and the pressurized oil is supplied into the pressure chamber 57. As a result, oil pressure acts on the rear surface of the ring gear 56, and the ring gear 56 moves forward against the biasing force of the compression coil spring 62. Due to this movement, the ring gear 56 is rotationally displaced relative to the driven gear 17 in the rotational direction of the driven gear 17. Further, with the movement, the casing 53 is rotationally displaced relative to the ring gear 56 in the rotational direction of the ring gear 56.

Therefore, when the ring gear 56 moves forward, the intake camshaft 9 relatively rotates in the rotational direction of the driven gear 17 by the sum of the rotational displacement of the ring gear 56 and the rotational displacement of the casing 53. It will be displaced. Therefore, the opening timing and the closing timing of the intake valve 23 are advanced according to the displacement amount of the intake side camshaft 9. In this way, the ring gear 56 moves in the annular space 55.
The opening / closing timing of the intake valve 23 when it is at the front end position is referred to as "early timing" hereinafter.

On the other hand, when the hydraulic control valve 63 is closed, the oil passages 58 and 59 are connected to the oil return passage 65.
Then, the pressurized oil in the pressure chamber 57 is transferred to the oil return passage 6
It is returned to the oil pan via 5. At this time, the pressure chamber 57
Since the oil flows out from the ring gear 56 and the pressure acting on the ring gear 56 decreases, the ring gear 56 moves rearward by the urging force of the compression coil spring 62. Then, by the operation opposite to the above-described operation, the intake camshaft 9 is rotationally displaced relative to the driven gear 17 in the direction opposite to the rotational direction thereof. Therefore, the intake valve 23
The valve opening timing and the valve closing timing are delayed according to the amount of displacement of the intake camshaft. As described above, when the ring gear 56 is at the rear end position of the annular space 55, the intake valve 23 is opened / closed.
The valve closing timing is hereinafter referred to as "normal timing".

When the intake side camshaft 9 is relatively rotationally displaced by opening and closing the hydraulic control valve 63 as described above, backlash is generated in the ring gear 56, and rattling due to the backlash causes viscous coupling 66. By the action of, the generation of abnormal noise is suppressed.
The viscous coupling 66 includes an outer plate 67 press-fitted and fixed to the driven gear 17, and a casing 53.
The inner plate 68 is formed on the outer periphery, and a viscous fluid having a high viscosity is sealed between the two 67, 68.

In order to return the oil leaking from the pressure chamber 57 to the spring chamber 61 to the oil pan, the driven gear 1
A drain passage 69 is formed in the intake camshaft 9 and the cylinder head 22.

5 (a) and 5 (b), the opening / closing timing of the intake valve 23 and the opening / closing of the exhaust valve 25 by the variable valve timing mechanism 52 (51) configured as described above are shown.
Indicates the valve closing timing. Further, FIG. 6 shows the opening / closing timings of the intake valve 23 and the exhaust valve 25 in relation to the valve lift amount. In the "normal timing", the intake valve 23 is opened at the valve opening timing a1 before the exhaust top dead center and closed at the valve closing timing b1 after the intake bottom dead center. Further, the intake valve 23 has the above-mentioned valve opening timing a at “early timing”.
The valve is opened at a valve opening timing a2 that is earlier by a predetermined angle than 1 and is closed at a valve closing timing b2 that is earlier by a predetermined angle than the valve closing timing b1. On the other hand, the opening timing d and the closing timing c of the exhaust valve 25
Is not changed and is always constant at both “normal timing” and “early timing”.

Therefore, the intake valve 23 and the exhaust valve 2
The valve overlap, which is the period in which both 5 are open, is larger in the “early timing” than in the “normal timing”.

As shown in FIGS. 2 and 3, a rotation speed sensor 71 and an absolute pressure sensor 72 are provided to detect the operating state of the engine 1 equipped with the variable valve timing mechanisms 51 and 52. .. The rotation speed sensor 71 is arranged in the vicinity of the crank pulley 4 and detects the engine rotation speed NE from the rotation of the crankshaft 3. The absolute pressure sensor 72 is provided in the surge tank 34 and detects the intake pipe pressure (absolute pressure) P in the intake passage B.

Next, the exhaust passage C will be described.
As shown in FIG. 2, the most upstream side of the exhaust passage C is constituted by the exhaust manifolds 38 and 39 attached to the outer surfaces of the left and right banks 5 and 6. A first exhaust branch pipe 41 and a second exhaust branch pipe 42 are connected to the downstream ends of the respective exhaust manifolds 38, 39. Right exhaust manifold 3
Reference numeral 9 is for collecting the combustion gas discharged from the cylinders # 1, # 3, # 5 and guiding it to the second exhaust branch pipe 42. The exhaust manifold 38 on the left side is for the cylinders # 2, #.
This is for collecting the combustion gases discharged from Nos. 4 and # 6 and guiding them to the first exhaust branch pipe 41.

The two exhaust branch pipes 41 and 42 join together on the downstream side to form an exhaust main pipe 43. This merging portion constitutes a cross-sectional area enlarged portion 44 having a cross-sectional area larger than the cross-sectional area of the first exhaust pipe 41 or the second exhaust branch pipe 42.
Therefore, the pressure wave due to the blowdown in the cylinders # 1, # 3, # 5 in the right bank 6 is generated in the exhaust manifold 39, the second
When it reaches the cross-sectional area enlarging portion 44, it is transmitted through the exhaust branch pipe 42 in order, and is inverted at the same portion to form a negative pressure wave.
Propagate toward # 5. Similarly, the pressure wave due to blowdown in the cylinders # 2, # 4, # 6 in the left bank 5 is
The exhaust manifold 38 and the first exhaust branch pipe 41 are sequentially transmitted,
When it reaches the enlarged cross-sectional area portion 44, it is inverted at the same portion and becomes a negative pressure wave and propagates toward the cylinders # 2, # 4, # 6.

The first exhaust branch pipe 41 and the second exhaust branch pipe 42
And are communicated with each other by a communication pipe 45 at an intermediate portion thereof. The cross-sectional area of the communication passage in the communication pipe 45 is substantially the same as the cross-sectional area of each of the first exhaust branch pipe 41 and the second exhaust branch pipe 42. An exhaust control valve 46 that opens and closes the communication passage is rotatably provided in the communication pipe 45. Exhaust control valve 46
When the valve is opened, the first exhaust branch pipe 41 is also communicated with the second exhaust branch pipe 42 via the communication pipe 45, so that the cross-sectional area of the first exhaust branch pipe 41 is the connecting portion with the communication pipe 45. In this case, the cross-section area is substantially doubled and the cross-sectional area is rapidly enlarged. The same applies to the second exhaust branch pipe 42.

Therefore, when the exhaust control valve 46 is opened,
The connection portion between the first exhaust branch pipe 41 and the communication pipe 45, and the second
At the connecting portion between the exhaust branch pipe 42 and the communication pipe 45, the direction of the pressure wave due to blowdown is reversed and becomes a negative pressure wave. In this case, most of the energy of the exhaust pulsation is reversed in the communication pipe 45, so the negative pressure wave reversed in the cross-sectional area enlarging portion 44 becomes very small and does not have a substantial effect.

In this embodiment, the negative pressure wave based on the blowdown in the cylinder that explodes this time or the negative pressure wave based on the blowdown in the cylinder that will explode the next time is exhausted when the valve 25 overlaps. Cylinder # 1 to cylinder # 1
The length L to each exhaust valve 25 (see FIG. 3) of # 6 and the length L from the connecting portion of the exhaust branch pipes 41 and 42 to the communication pipe 45 to each exhaust valve 25 are calculated based on the following equation. It is set.

T = (180/360) · {1 / (N / 60)} = 2L
/ V where t is the time required from the occurrence of blowdown in a predetermined cylinder to the valve overlap. Also, 360
Is a crank angle required for one revolution of the crankshaft 3, and 180 is a crank angle from the occurrence of blowdown in a predetermined cylinder to the valve overlap. N is the engine speed, 1 / (N / 60) is the crankshaft 3
Is the time required to make one revolution. Further, 2L is the length of the propagation path of the pressure wave and the negative pressure wave due to blowdown, and v is the speed of sound.

In the present embodiment, from the above equation, when the engine speed NE by the speed sensor 71 is equal to or higher than a predetermined first speed α (eg, 4400 rpm), and is lower than the first speed α. The second rotation speed β (for example, 20
00 rpm) or less, the length 2L of the propagation path of the pressure wave and the negative pressure wave is set to a predetermined length (about 1.8 m), and the engine speed NE is higher than the second speed β and When it is lower than the first rotation speed α (200
At 0 rpm <NE <4400 rpm), the length 2L of the propagation path is set longer than the predetermined length (about 4.2 m).

The first exhaust branch pipe 41 and the second exhaust branch pipe 4
In FIG. 2, catalytic converters 47 and 48 are provided near the exhaust manifolds 38 and 39. Further, catalytic converters 49 and 50 are also provided between the communication pipe 45 and the cross-sectional area enlarged portion 44 in both the exhaust branch pipes 41 and 42. These catalytic converters 47 to 50 are for purifying hydrocarbon (HC), carbon monoxide (CO), and nitric oxide (NOx) in the combustion gas by the action of the catalyst.

As shown in FIG. 2, the rotation speed sensor 71
And the absolute pressure sensor 72 is an electronic control unit (hereinafter, simply referred to as “E
(Hereinafter referred to as “CU”) 73. In addition, both the variable valve timing mechanisms 51 and 52
Hydraulic control valve 63 and exhaust control valve 46 in the communication pipe 45
Are electrically connected to the output side of the ECU 73.

The ECU 73 is a central processing unit (hereinafter referred to as CPU) as timing control means and opening / closing control means.
74 and read-only memory (hereinafter referred to as ROM) 75
And a random access memory (hereinafter referred to as RAM) 76
, An input port 77, and an output port 78, which are connected to each other by a bus 79. CPU7
Reference numeral 4 executes various kinds of arithmetic processing according to a preset control program, and the ROM 75 stores in advance a control program and initial data required for the CPU 74 to execute arithmetic processing. Further, the RAM 76 temporarily stores the calculation result of the CPU 74.

The signal from the rotation speed sensor 71 is input to the input port 77. Further, the signal from the absolute pressure sensor 72 is input to the input port 77 via the A / D converter 81. Then, the CPU 74 detects the engine speed NE and the absolute pressure P from these signals. On the other hand, CPU
74 controls opening and closing of the hydraulic control valve 63 via the output port 78 and the drive circuit 82, and the output port 78 and the drive circuit 8
The exhaust control valve 46 is controlled to be opened / closed via the switch 3.

Next, the operation of this embodiment constructed as described above will be described with reference to FIGS. 8 and 7. Figure 8 shows CPU
Of the respective processes executed by 74, the hydraulic control valve 63
9 is a flowchart for controlling the opening and closing of the exhaust control valve 46, which is executed by interruption every predetermined time. Also,
FIG. 7 shows the relationship between the engine speed NE and the absolute pressure P in the normal timing region and the early timing region of the intake valve 23 by the variable valve timing mechanisms 51 and 52, and the opening and closing regions of the exhaust control valve 46. It is a figure which shows and.

When the processing shifts to the processing routine of FIG. 8,
First, in step 101, the CPU 74 reads the absolute pressure P from the absolute pressure sensor 72 and determines whether or not the absolute pressure P is equal to or higher than a predetermined pressure PH. Also, the CPU 74
In step 102, the engine speed NE is read by the engine speed sensor 71, and it is determined whether the engine speed NE is equal to or lower than the third engine speed γ (for example, 6400 rpm). When the absolute pressure P is lower than the pressure PH (P <PH) in step 101, or in step 102, the engine speed NE is higher than the third speed γ (NE>).
In the case of γ), the CPU 74 proceeds to step 103 and outputs a drive signal for closing the hydraulic control valve 63 via the output port 78 and the drive circuit 82. Then, the oil passages 58 and 59 are communicated with the oil return passage 65, and the pressure chamber 5
The pressurized oil in 7 is returned to the oil pan via the oil return passage 65. As a result, the ring gear 56 is positioned at the rear end of the annular space 55 by the biasing force of the compression coil spring 62, and the opening / closing timing of the intake valve 23 becomes "normal timing".

Further, the CPU 74 outputs a drive signal for opening the exhaust control valve 46 via the output port 78 and the drive circuit 83, and once ends this routine. As a result, when the exhaust control valve 46 opens, the pressure waves propagating through the exhaust manifolds 38, 39 and the exhaust branch pipes 41, 42, which are generated by the explosion in each cylinder and the blowdown in the exhaust stroke,
The negative pressure wave is generated by being inverted at the communicating pipe 45 portion. Then, this negative pressure wave reaches the exhaust valve 25 at the time of valve overlap.

In step 101, the absolute pressure P is equal to or higher than the pressure PH (P ≧ PH), and in step 102, the engine speed NE is equal to or lower than the third speed γ (NE ≦.
In the case of γ), the CPU 74 proceeds to step 104.
In step 104, the CPU 74 outputs a drive signal for opening the hydraulic control valve 63 via the output port 78 and the drive circuit 82. Then, the oil passages 58 and 59 are communicated with the oil supply passage 64, and the pressurized oil causes the pressure oil to pass through the pressure chamber 57.
Supplied within. As a result, the ring gear 56 moves forward against the biasing force of the compression coil spring 62, and the opening / closing timing of the intake valve 23 becomes “early timing”.
The valve overlap is wider than in "normal timing".

Next, in step 105, the CPU 74 determines that the engine rotational speed NE is the first rotational speed α (4400 r in this case).
pm), and further step 10
At 6 the engine speed NE is the second speed β (in this case 2
000 rpm). According to both determinations, the engine speed NE at that time is the second speed β
Higher than and lower than the first rotational speed α (β <NE <α)
Then, the CPU 74 outputs a drive signal for closing the exhaust control valve 46 via the output port 78 and the drive circuit 83 in step 107, and ends this routine once. As a result, when the exhaust control valve 46 is closed, the pressure wave propagating in the exhaust manifolds 38, 39 and the exhaust branch pipes 41, 42 due to the explosion in each cylinder and the blowdown in the exhaust stroke is reversed at the communication pipe 45. Instead, the cross-sectional area enlarging portion 44 is reversed. Therefore, the length 2L of the propagation path at this time is about 4.2 m.

On the other hand, step 105 and step 1
When the engine speed NE is equal to or higher than the first speed α (NE ≧ α) according to the determination in 06, and the engine speed N is equal to or higher than the first speed α.
When E is equal to or lower than the second rotation speed β (NE ≦ β), the CPU 7
4 is the output port 78 and the drive circuit 83 in step 108.
A drive signal for opening the exhaust control valve 46 is output via, and this routine is once ended. As a result, when the exhaust control valve 46 is opened, it occurs due to explosion in each cylinder and blowdown in the exhaust stroke, and the exhaust manifolds 38, 3
9, the pressure wave propagating through the exhaust branch pipes 41, 42,
It will be reversed in part 5. Therefore, the length 2L of the propagation path at this time is about 1.8 m.

The negative pressure wave whose direction is reversed by the cross-sectional area enlarging portion 44 or the communication pipe 45 as described above is generated in each cylinder # 1.
At the time of valve overlap in # 6 to # 6, the exhaust gas reaches the exhaust valve 25 and tries to suck out the combustion gas in the combustion chamber 19 of the same cylinder # 1 to # 6 to the exhaust passage C side. Therefore, the amount of fresh air flowing from the intake port 21 into each of the cylinders # 1 to # 6 increases. As a result, the intake efficiency of each of the cylinders # 1 to # 6 is improved, which in turn improves the output of the engine 1 as a whole. Further, since the gas temperature in the combustion chamber 19 is lowered by the scavenging action of the fresh air flowing from the intake port 21 into each of the cylinders # 1 to # 6, the occurrence of knocking can be suppressed.

FIGS. 9 and 10 are graphs showing the results of measuring the relationship between the exhaust pressure at the exhaust port 24 of the fourth cylinder # 4 and the crank angle for each engine speed NE. Of these, FIG. 9 shows the case where the length 2L of the propagation path is constant,
FIG. 10 shows a case where the exhaust control valve 46 is opened or closed according to the engine speed NE to switch the length 2L of the propagation path. In these figures, the scale of the exhaust pressure at the exhaust port 24 is 800 rpm at the engine speed NE.
Is shown, and other engine speeds NE are omitted.

In FIG. 9, looking at the exhaust pressure at the exhaust port 24 when the engine speed NE is, for example, 800 rpm, the pressure wave P due to blowdown in the third cylinder # 3 is seen.
3, pressure wave P4 due to blowdown in the fourth cylinder # 4,
Pressure wave P5 due to blowdown in fifth cylinder # 5, sixth
Pressure wave P6 due to blowdown in cylinder #, first cylinder #
The pressure wave P1 due to blowdown in No. 1 and the pressure wave P2 due to blowdown in the second cylinder # 2 are generated at predetermined intervals. Then, it is understood that the exhaust pressure of the exhaust port 24 of the fourth cylinder # 4 is a positive pressure or almost zero during the valve overlap of the fourth cylinder # 4 over almost the entire engine speed NE. Therefore, when the length 2L of the propagation path is constant (FIG. 9), improvement in intake efficiency due to the negative pressure wave cannot be expected. On the other hand, when the length 2L of the propagation path is switched (FIG. 10) and the engine speed NE is 800 rpm and 1200 rpm, the pressure wave P due to the blowdown in the fifth cylinder # 5 is seen.
It can be seen that the negative pressure wave (the shaded portion in FIG. 10) that seems to have reversed the direction of No. 5 is synchronized with the valve overlap in the fourth cylinder # 4. Further, when the engine speed NE is 2000 rpm, the secondary negative pressure wave due to the blowdown in the fourth cylinder # 4 is synchronized with the valve overlap in the fourth cylinder # 4.

Further, the engine speed NE is 2400 rp
In the case of m, the exhaust control valve 46 is closed and the length 2L of the propagation path becomes as long as about 4.2 m. Therefore, the primary negative pressure wave due to the blowdown in the fourth cylinder # 4 is synchronized with the valve overlap. ing.

Further, the engine speed NE is 4400r.
In the case of pm or more, the exhaust control valve 46 is opened again, and the fourth cylinder # occurs when the length 2L of the propagation path is 1.8 m.
The first negative pressure wave due to the blowdown in 4th cylinder # 4
Synchronize with valve overlap at 4.

FIG. 11 shows the relationship between engine speed and torque. In the figure, the solid line indicates the present embodiment in which the opening / closing timing of the intake valve 23 and the length 2L of the propagation path are variable as described above, and the broken line indicates the opening / closing of the intake valve 23.
A comparative example in which the valve closing timing is constant and the length 2L of the propagation path is constant is shown. From this figure, it is understood that the output torque in this embodiment is higher than that in the comparative example over a wide range of engine speed.

The present invention is not limited to the configuration of the above-described embodiment, and may be arbitrarily modified within the scope not departing from the spirit of the invention, for example, as follows. (1) In the above embodiment, the variable valve timing mechanism 5
As 1, 52, a type that controls switching between two timings of normal timing and early timing is used.
Instead of this, a type that can continuously adjust the opening / closing timing of the intake valve 23 may be used. (2) The control device for a 6-cylinder internal combustion engine of the present invention can be applied to an in-line 6-cylinder engine other than the V-type 6-cylinder engine 1. (3) In the above embodiment, the variable valve timing mechanism 51,
The helical gear 56 on the inner and outer circumferences of the ring gear 56 at 52.
Although a and 56b are formed, only one of them may be a helical tooth. (4) Variable valve timing mechanism 51, 5 of the above embodiment
In 2, the opening / closing timing of only the intake valve 23 is controlled, but the opening / closing timing of only the exhaust valve 25 is controlled, or the opening / closing timing of both the intake valve 23 and the exhaust valve 25 is controlled. May be controlled. (5) In the above embodiment, the communication pipe 45 and the exhaust control valve 46
Although only one is provided for each, a plurality of these may be provided. (6) In the above embodiment, the first exhaust branch pipe 41 and the second exhaust branch pipe 42 are merged, and the merged portion is expanded in cross section area 44.
However, the cross-sectional area enlarging portion 44 may be provided in each of the exhaust branch pipes 41 and 42 without joining them.

[0067]

As described above in detail, according to the present invention, at the time of valve overlap of the cylinder that explodes this time, a negative pressure wave due to blowdown in the cylinder that explodes this time or a negative pressure wave due to blowdown in the cylinder that explodes next time will occur. Since the pressure wave is made to reach the exhaust valve of the cylinder that explodes this time, the excellent effect that it becomes possible to improve the intake efficiency and the engine output over a wide range of rotational speeds is achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing a control device for a 6-cylinder internal combustion engine according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 4 is an enlarged sectional view showing a variable valve timing mechanism.

5A is a diagram showing opening / closing timings of the intake valve and the exhaust valve at a normal timing, and FIG. 5B is a diagram showing opening / closing timings of the intake valve and the exhaust valve at an early timing. It is a figure.

FIG. 6 is a diagram showing a relationship between a crank angle and a valve lift amount.

FIG. 7 is a diagram showing a normal timing region and an early timing region of an intake valve by a variable valve timing mechanism, and an opening region and a closing region of an exhaust control valve in a relationship between an engine speed and an absolute pressure.

FIG. 8 is a flow chart for explaining the operation of the present embodiment.

FIG. 9 is a graph showing the results of measuring the relationship between the crank angle when the exhaust control valve is not used and the exhaust pressure at the exhaust port of the fourth cylinder for each engine speed.

FIG. 10 is a graph showing the results of measuring the relationship between the crank angle when an exhaust control valve is used and the exhaust pressure at the exhaust port of the fourth cylinder for each engine speed.

FIG. 11 is a graph showing the relationship between engine speed and torque.

FIG. 12 is a schematic configuration diagram of a four-cylinder internal combustion engine and an exhaust system showing a conventional technique.

[Explanation of symbols]

1 ... Engine as internal combustion engine, 19 ... Combustion chamber, 23 ...
Intake valve, 25 ... Exhaust valve, 44 ... Enlarged section area,
45 ... a communication pipe forming a communication passage, 46 ... an exhaust control valve, 5
1, 52 ... Variable valve timing mechanism, 71 ... Rotation speed sensor forming part of operating state detecting means and rotating speed detecting means, 72 ... Absolute pressure sensor forming part of operating state detecting means, 74 ... Timing control CPU constituting the means and the opening / closing control means, # 1 ... first cylinder, # 2 ... second cylinder, #
3 ... 3rd cylinder, # 4 ... 4th cylinder, # 5 ... 5th cylinder, # 6
... 6th cylinder, B ... Intake passage, C ... Exhaust passage, L ... Propagation path length, α ... First rotation speed, β ... Second rotation speed

Claims (1)

[Claims] 1. At least one of an intake valve provided in an internal combustion engine having six cylinders and opening and closing an intake passage to a combustion chamber of the internal combustion engine, and an exhaust valve opening and closing two exhaust passages from the combustion chamber. A variable valve timing mechanism for adjusting the valve timing of one of the valves, an operating state detecting means for detecting an operating state of the internal combustion engine, and a valve state of the valve according to the operating state of the internal combustion engine by the operating state detecting means. Timing control means for calculating the target valve overlap and controlling the variable valve timing mechanism so that the actual valve overlap becomes the target valve overlap; and explosion / exhaust in each cylinder provided in the exhaust passage. Reverse the direction of the pressure wave generated by blowdown in the stroke and propagating in the exhaust passage. And a cross-sectional area enlarged portion for creating a negative pressure wave toward the exhaust valve of the cylinder, and a communication passage that communicates between the exhaust passages on the upstream side of the cross-sectional area enlarged portion, which is openable and closable. Exhaust control valve for allowing or blocking the reversal of the direction of the pressure wave in the same communication passage, rotation speed detection means for detecting the engine speed of the internal combustion engine, and blowdown in the cylinder that explodes this time. Based on the negative pressure wave or the negative pressure wave based on the blowdown in the next exploding cylinder,
During the valve overlap by the variable valve timing mechanism, when the engine rotation speed by the rotation speed detection means is equal to or higher than a predetermined first rotation speed so as to reach the exhaust valve of the cylinder that explodes this time, and the first rotation speed. When the rotational speed is equal to or lower than the second rotational speed lower than the rotational speed, the exhaust control valve is opened to set the propagation paths of the pressure wave and the negative pressure wave to a predetermined length, and the engine operated by the rotational speed detecting means. When the rotation speed is higher than the second rotation speed and lower than the first rotation speed, the exhaust control valve is closed to open / close the propagation path longer than the predetermined length. A control device for a 6-cylinder internal combustion engine, comprising: a control means.