JPH1122499A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain an intake charging efficiency of an engine high in spite of dimensional change by manufacturing tolerance and a secular change of an exhaust pipe. SOLUTION: Exhaust pipes from each cylinder of an engine 1 are collected to two exhaust passages 52 and the like to constitute a dual exhaust system. The engine 1 is provided with a variable valve timing mechanism 10 which varies an intake valve open/close timing of each cylinder. A control circuit 30 controls the variable valve timing mechanism 10 based on an engine intake air amount input from an air flow meter 15 provided to an intake passage 13, and an valve timing of the engine is changed so that the time when a negative pressure wave generated by an exhaust pulse is attained to an exhaust port corresponds to a valve overlap period of an engine intake/exhaust valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a valve timing control device for an internal combustion engine.

[0002]

2. Description of the Related Art There is known a technique for improving the intake charging efficiency of an engine by utilizing a negative pressure wave generated by a pulsation of engine exhaust. For example, an example of this type of engine is disclosed in
There is one described in JP-A-243908. In the engine of the publication, the exhaust valve of each cylinder is closed once at the end of the exhaust stroke, and the exhaust valve is opened again for a predetermined period at the beginning of the intake stroke.

When the cylinder exhaust valve is opened during the exhaust stroke, the positive pressure wave generated at the exhaust port travels in the exhaust passage at the sonic speed. Then, the light travels toward the exhaust port, and the reflection is repeated between the exhaust port and the portion where the passage sectional area is rapidly increased. Since the intake port pressure decreases when the negative pressure wave reaches the exhaust port, if both the intake valve and the exhaust valve are opened at this time, the burned gas in the cylinder is discharged to the exhaust port. Both the inflow of fresh air from the intake port is promoted, and the intake filling efficiency is improved.

The engine disclosed in Japanese Patent Application Laid-Open No. Sho 62-243908 has a disadvantage that when the engine is operated under a predetermined load condition,
The exhaust valve once closed at the end of the exhaust stroke is reopened at the beginning of the intake stroke when the negative pressure wave reflected at the exhaust passage open end reaches the exhaust port, and the intake valve and the exhaust valve are simultaneously opened. (Valve overlap period) is forcibly generated, whereby the suction pressure is improved by using the negative pressure wave.

[0005]

However, in the engine disclosed in Japanese Patent Application Laid-Open No. Sho 62-243908, the timing at which the exhaust valve is closed and the overlap period between the intake valve and the exhaust valve is generated again. Because of the fixation, there is a possibility that a desired improvement in the intake air charging efficiency cannot be obtained. Originally, the position of the opening where the negative pressure wave is reflected in the exhaust pipe, the position of the suddenly enlarged sectional area, etc. is constant and does not change if the exhaust system is determined, so the negative pressure wave is reflected from the exhaust valve opening valve The time until returning to the exhaust port is substantially constant. For this reason, if the valve timing is set in advance according to the engine operating conditions so that the overlap period of the intake and exhaust valves coincides with the exhaust port arrival timing of the negative pressure wave, the negative pressure wave is always effectively used to fill the intake air. It should be able to improve efficiency.

However, in an actual exhaust system, the reflection position of the negative pressure wave may be different from the designed position. For example, when a connection portion is provided in the exhaust passage, a clearance may be generated in the connection portion due to a manufacturing tolerance or the like. If such a clearance occurs, the connection portion functions as an open end depending on the size of the clearance, and a negative pressure wave may be generated and reflected at the connection portion. In this case, the negative pressure wave is generated and reflected at a position closer to the exhaust port than the designed reflection position, so that the timing of the negative pressure wave reaching the exhaust port deviates from the design timing. If the arrival timing of the negative pressure wave deviates from the design timing as described above, the valve overlap period of the intake and exhaust valves does not exactly coincide with the arrival time of the negative pressure wave in the engine of the above publication, and the negative pressure wave is effectively used. You will not be able to do it.

Particularly, in a dual exhaust system in which the exhaust gas of each cylinder is divided into two exhaust passages, a so-called .theta. Pipe system is used in which a partition is provided in one exhaust pipe and the two exhaust passages are used. When a clearance is generated at the joint between the exhaust manifold and the θ pipe, the two exhaust passages communicate with each other through the clearance and easily function as a flow path rapid expansion portion, so that the above-described shift in the negative pressure wave arrival timing tends to occur. . In addition, the clearance of such a connection portion varies depending on the tolerance of each product, and even in the case of the same engine, it changes due to thermal expansion (engine load) during use, aging due to use, and the like. Therefore, the arrival timing of the negative pressure wave may also change depending on the presence or absence of the clearance, its size, and the like, and it is difficult to predict a change in the arrival timing of the negative pressure wave in advance.

The present invention has been made in view of the above-described problems, and it is possible to effectively use a negative pressure wave even when the exhaust port arrival timing of the negative pressure wave deviates from a design value due to variations or aging due to product tolerances of individual exhaust pipes. It is an object of the present invention to provide a valve timing control device for an internal combustion engine that can improve the intake charging efficiency of the engine by utilizing the same.

[0009]

According to the first aspect of the present invention, there is provided a valve timing adjusting means for changing at least one of an intake valve and an exhaust valve timing of an internal combustion engine, and exhaust pulsation in an exhaust passage. A negative pressure wave arrival timing detecting means for detecting a timing at which the negative pressure wave generated by the negative pressure wave reaches the exhaust port, and controlling the valve timing adjusting means so that the negative pressure wave detected by the negative pressure wave reaching timing detecting means reaches the exhaust port timing. And a control means for changing the valve timing in accordance therewith.

That is, according to the first aspect of the present invention, the negative pressure wave arrival timing detecting means directly or indirectly detects the timing at which the negative pressure wave actually reaches the exhaust port. Further, the control means changes the valve timing according to the arrival time of the negative pressure wave. For this reason, even when the negative pressure wave arrival timing deviates from the design value, the valve timing is adjusted according to the actual negative pressure wave arrival timing.

According to the second aspect of the present invention, the control means controls the valve timing adjusting means so that the negative pressure wave reaches the exhaust port within a valve overlap period between the intake valve and the exhaust valve. The valve timing control device according to claim 1, wherein the valve timing is changed by changing the valve timing. That is, according to the second aspect of the invention, the engine valve timing is changed such that the timing at which the negative pressure wave reaches the exhaust port is within the valve overlap period of the intake and exhaust valves. Even when the value deviates from the value, it is possible to improve the engine intake charging efficiency by using the negative pressure wave.

According to the third aspect of the present invention, the negative pressure wave arrival timing detecting means includes an intake air amount detecting means for detecting an engine intake air amount, and is provided when the engine is operated under predetermined conditions. 2. The valve timing control device according to claim 1, wherein the timing at which the negative pressure wave reaches an exhaust port is detected based on an engine intake air amount. That is, in the third aspect of the present invention, the negative pressure wave reaching timing detecting means indirectly detects the negative pressure wave reaching the exhaust port based on the intake air amount under the predetermined operating condition of the engine. The greater the difference between the negative pressure wave arrival time at the exhaust port and the current valve overlap period, the lower the engine intake charging efficiency, and the lower the engine intake air amount. Therefore, by comparing the designed value and the absolute value of the intake air amount under the predetermined operating condition, the timing of the negative pressure wave reaching the exhaust port (ie, the deviation from the design reaching timing) can be calculated.

According to the fourth aspect of the present invention, the negative pressure wave reaching timing detecting means includes a pressure detecting means disposed in an exhaust passage, and the negative pressure wave arrival timing detecting means detects the negative pressure wave based on a change in the exhaust pressure detected by the pressure detecting means. A valve timing control device according to claim 1 for detecting a timing at which a pressure wave reaches an exhaust port. That is, according to the fourth aspect of the present invention, the timing of the negative pressure wave reaching the exhaust port is directly detected by the pressure detecting means disposed in the exhaust passage. Since the timing at which the negative pressure wave passes through the exhaust passage portion where the pressure detecting means is disposed can be detected from the pressure fluctuation detected by the pressure detecting means, the negative pressure wave reaches the exhaust port based on the distance between the pressure detecting means and the exhaust port and the above timing. Timing is calculated.

According to a fifth aspect of the present invention, there is provided a valve timing control apparatus for an internal combustion engine provided with an exhaust passage having a connection portion, wherein at least one of an intake valve and an exhaust valve of the internal combustion engine is controlled. A valve timing adjusting means for changing, a negative pressure wave reaching timing detecting means for detecting that a negative pressure wave caused by exhaust pulsation reaches an exhaust port due to a clearance at the exhaust passage connecting portion, and a negative pressure wave reaching When the timing detecting means detects a change in the timing at which the negative pressure wave arrives at the exhaust port, the valve timing adjusting means is controlled so that the negative pressure wave is exhausted during the valve overlap period between the intake valve and the exhaust valve. A valve timing control device for an internal combustion engine, comprising: a control unit for changing the valve timing so as to reach the valve timing.

In other words, according to the fifth aspect of the present invention, the shift of the timing at which the negative pressure wave arrives at the exhaust port due to the clearance of the exhaust passage connecting portion is detected by the negative pressure wave arrival means, and the control means detects the shift amount of this timing. The engine valve timing is changed such that the negative pressure wave reaches the exhaust port during the valve overlap period. For this reason,
Even in the case where a clearance occurs at the exhaust passage connection portion, the engine intake charging efficiency can be improved by effectively utilizing the negative pressure wave due to the exhaust pulsation.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment in which the valve timing control device of the present invention is applied to a four-cylinder engine for an automobile. In FIG. 1, reference numeral 1 indicates an internal combustion engine for a vehicle. In this embodiment, the engine 1 is a DOHC (double overhead camshaft) type four-cylinder engine having four cylinders # 1 to # 4. In the present embodiment, the exhaust system of the engine 1 is a so-called dual exhaust system in which two cylinders in an ignition order that do not cause exhaust interference with each other are connected to one exhaust passage, respectively. As shown in the figure, the # 1 and # 4 cylinders are connected to the exhaust manifold 51 via the intake branch pipes 41 and 44, and the # 2 and # 3 cylinders are connected to the exhaust manifold via the intake branch pipes 42 and 43, respectively. It is connected to a tube 52. Also, as shown in FIG.
1 and 52 are not actually separate pipes, but one pipe 5
The pipe 10 is provided with a partition wall 511 in the axial direction, and the pipe 510 is provided with flow paths 51 and 52 functioning as individual exhaust collecting pipes.

The exhaust pipe 510 has a similar θ pipe structure having exhaust passages 531 and 532 at a connection portion 520.
30. Further, the exhaust pipe 530 is connected to a normal exhaust pipe 550 at a connection portion 540 on the downstream side, and the two exhaust flow paths 531 and 532 in the exhaust pipe 530 join one exhaust flow path. In FIG. 1, an intake manifold 131 connects the cylinders # 1 to # 4 to a common intake passage 13.
Reference numeral 17 denotes a throttle valve arranged in the intake passage 13.
Further, an air flow meter 15 of, for example, a hot wire type, which can detect an engine intake air amount (weight flow rate), is disposed in the intake passage 13.

Further, a pressure sensor indicated by 70 in FIG. 1 is provided as necessary on one of the exhaust branch pipes of the exhaust system (the exhaust branch pipe 41 in FIG. 1). The pressure sensor 70 is required only when detecting the timing of the arrival of the negative pressure wave at the exhaust port based on the exhaust pressure fluctuation in the exhaust branch pipe, as described later. In this embodiment, the engine 1 is provided with a variable valve timing mechanism 10.

Hereinafter, the configuration of the variable valve timing mechanism shown in FIG. 1 will be briefly described with reference to FIG. In FIG. 3, reference numeral 11 denotes an intake camshaft for driving an intake valve (not shown) of each cylinder of the engine 1 to open and close, and a reference numeral 10 generally designates a variable valve timing mechanism provided at an end of the intake camshaft. .

The variable valve timing mechanism 10 includes a timing pulley 12 having a cylindrical sleeve 13 and a cover 14 for covering the end of the camshaft 1. The camshaft 11 is rotatably mounted around the shaft 11. The cover 14 is fixed to the timing pulley 12 by bolts 15 and pins 1b, and rotates integrally with the pulley 12.

A piston member 17 is provided inside the cover 14. The piston member 17 includes an annular piston portion 19 and a cylindrical portion 21 extending from the piston portion 19. An outer peripheral surface and an inner peripheral surface of the piston portion 19 are formed by an inner peripheral surface of the cover 14 and the inner peripheral surface of the pulley 12. The sleeve 13 is in sliding contact with the outer peripheral surface. An outer helical gear 21a and an inner helical gear 21b having a predetermined twist angle are engraved on the outer peripheral surface and the inner peripheral surface of the cylindrical portion 21 of the piston member 17, respectively. The internal helical gear 22a formed on the surface and the inner helical gear 21b mesh with a ring-shaped external helical gear 22b integrally mounted on the end face of the camshaft 11 with a bolt 1a and a pin 1b.

Variable valve timing mechanism 1 of the present embodiment
At 0, the rotation of the crankshaft (not shown) of the engine is transmitted to the timing pulley 12 via the timing belt 12a. When the pulley 12 rotates, the cover 14 rotates integrally with the pulley 12, and the piston member 17 connected to the cover 14 via the helical gears 22a, 21a rotates integrally with the cover 14. The piston member 17 is simultaneously connected to the camshaft 11 via the helical gears 21b and 22b.
To the camshaft 11
Rotates together with the pulley 12.

That is, in the variable valve timing mechanism 10 of the present embodiment, the rotational driving force of the camshaft 11 is
The power is transmitted from the crankshaft to the timing pulley 12 via the timing belt 12a, and the cover 1
4. Camshaft 11 via helical gears 22a, 21a, piston member 17 and helical gears 21b, 22b
Is transmitted to

Variable valve timing mechanism 1 of the present embodiment
A value of 0 changes the valve timing of the intake valve by moving the piston member 17 in the axial direction of the camshaft 11. That is, the helical gears 22a, 21 having a predetermined torsion angle that mesh with each other
a and 21b, 22b are connected to the cover 14 and the camshaft 11. Therefore, when the piston member 17 moves in the camshaft axial direction, the meshing positions of the helical gears 22a and 21a and 21b, 22b move in the axial direction along the respective tooth traces. However, since the tooth surface of each gear has a twist angle with respect to the camshaft axial direction, when the meshing position moves in the axial direction, the cover 14 and the piston member 17 and the piston member 17 and the camshaft 11 respectively become It relatively moves in the circumferential direction along the tooth trace of the helical gear. For this reason, the cover 14 and the piston member 17 and the piston member 17 and the camshaft 11 relatively rotate with the axial movement of the piston member 17. Therefore, by moving the piston member 17 in the axial direction of the camshaft 11 during operation of the engine, the rotational phase of the timing pulley 12, that is, the rotational phase of the camshaft 11 with respect to the rotational phase of the crankshaft can be advanced (or delayed). Thus, the opening and closing timing of the intake valve driven by the camshaft 11 can be advanced (or retarded).

As described above, since the variable valve timing mechanism 10 of this embodiment changes only the rotational phase of the intake camshaft 11, when the valve timing is changed, the opening timing and closing timing of the intake valve are changed. The timing always changes by the same amount, and the opening period of the intake valve itself is kept constant.
In the present embodiment, during the operation of the engine, the valve timing of the intake valve is changed by moving the piston member 17 using hydraulic pressure. As shown in FIG. 3, two oil passages 2 and 3 are bored in the camshaft 11 along the axial direction. The oil passage 2 is provided at the center of the camshaft 11, and the shaft end side of the oil passage 2 is formed between the inner surface of the cover 14 and the shaft end side end surface of the piston 17 via a port 2a formed in the bolt 1a. The hydraulic chamber 5 communicates with the hydraulic chamber 5.
The other end of the oil passage 2 is connected to a linear solenoid valve 25 to be described later via a port 2b formed in the camshaft 11 in a radial direction. On the other hand, the end of the oil passage 3 on the shaft end side is the ring-shaped external helical gear 2.
2b. The oil passage 3 communicates with the hydraulic chamber 8 formed by the end face of the piston 17 and the timing pulley 12 and the cover 14 through a port 3a formed in a radial direction, and linearly through another port 3b. It communicates with the solenoid valve 25.

The linear solenoid valve 25 is a spool valve having a spool 26, and includes a hydraulic port 26a connected to the port 2b of the oil passage 2 through a pipe,
A hydraulic port 26b connected to a port 3b of the oil passage 3 via a pipe, a port 26c connected to a pressure oil supply source 28 such as an engine lubricating oil pump, and two drain ports 26
d and 26e. The spool 26 of the valve 25 connects one of the ports 26a and 26b to the port 26c.
And operates to connect the other to the drain port.

That is, when the spool 26 moves to the left in FIG. 3, the port 26a communicating with the port 2b of the hydraulic passage 2 is connected to the hydraulic supply 28 via the port 26c, and the drain port 26d is closed. Also,
At this time, the port 26b connected to the port 3b of the hydraulic passage 3 communicates with the drain port 26e at the same time. Therefore, the hydraulic chamber 5 of the variable valve timing mechanism 10 is provided with a hydraulic passage 2 from a hydraulic supply source 28 such as a lubricating oil pump of the engine.
Lubricating oil flows in through the port 2a and pushes the piston 19 rightward in FIG. At this time, the lubricating oil in the hydraulic chamber 8 is discharged from the port 3a through the oil passage 3, the port 3b, the port 26b of the linear solenoid valve 25, and the like, from the drain port 26e. Therefore, the piston member 17 moves rightward in FIG.

When the spool 26 moves rightward in FIG. 3, the port 26b is connected to the port 26c, and the port 26a is connected to the drain port 26d. As a result, the lubricating oil flows into the hydraulic chamber 8 through the oil passage 3 and the lubricating oil is discharged from the hydraulic chamber 5 through the oil passage 2 to the drain port 26d.
7 moves leftward in FIG.

In this embodiment, when the lubricating oil is supplied to the hydraulic chamber 5 and the piston member 17 moves rightward in FIG. 3, the intake valve timing is changed to the advance side, and the lubricating oil is supplied to the hydraulic chamber 8. When the piston member 17 is supplied and moves in the left direction in FIG. 3, the helical gears 21a, 21b and 22a,
The twist angle of 2b is set.

In FIG. 3, reference numeral 25b denotes a linear solenoid actuator for driving the spool 26. The linear solenoid actuator 25b receives a control signal from a control circuit 30, which will be described later, and moves the spool 26 by an amount proportional to the magnitude of the control signal, thereby adjusting the position of the piston member 17, that is, the valve timing of the intake valve. change.

In FIG. 3, reference numeral 30 denotes a control circuit for controlling the operation of the linear solenoid valve 25. In the present embodiment, the control circuit 30 is a read-only memory (ROM)
32, a random access memory (RAM) 33, a microprocessor (CPU) 34, an input port 35, and an output port 36 are connected to each other by a bidirectional bus 31 as a digital computer having a known configuration. Also,
The control circuit 30 includes a backup RAM 37 that is directly connected to a power supply such as a battery and can retain and store data even when the engine is stopped. The control circuit 30 of the present embodiment controls the operation of the linear solenoid valve 25 in accordance with the engine operating conditions, adjusts the valve timing of the intake valve, and controls the valve overlap amount of the intake and exhaust valves. For this control, an input port 35 of the control circuit 30 supplies a voltage signal proportional to the engine intake air amount (weight flow rate) G from an air flow meter 15 (for example, a hot wire air flow meter) provided in the intake passage 13 of the engine. If installed, a voltage signal proportional to the exhaust pressure PE from the pressure sensor 70 of the exhaust branch pipe 41 is input via the AD converter 43, respectively, and a crank provided on the engine crankshaft. A pulse signal indicating a crankshaft rotation angle from the shaft rotation angle sensor 44 and a pulse signal indicating a rotation angle of the camshaft 11 from a cam rotation angle sensor 45 provided on the camshaft are input.

From the engine intake air amount G detected by the air flow meter 15, an intake weight flow rate GN (= G / NE) per one engine revolution is further calculated at regular intervals using the engine speed NE. 30 is stored in the RAM 33. The pulse signal from the crankshaft rotation angle sensor 44 is
It consists of an N1 signal indicating the reference position of the crankshaft generated every 720 degrees of crankshaft rotation, and an NE signal generated every 30 degrees of crankshaft rotation. A CN1 pulse signal indicating that the camshaft has reached the reference position is generated.
The control circuit 30 calculates the engine speed NE from the pulse interval of the NE signal at regular intervals, and calculates the engine speed NE.
Using E, the actual rotation phase (valve timing of the intake valve) VT of the camshaft 11 is calculated from the time interval between the N1 signal and the CN1 signal. This calculation result is stored in the RAM 33. Further, the exhaust pressure PE is AD-converted at regular intervals and stored in the RAM 33 in the same manner. That is, RAM3
3, the values of NE, VT, GN, PE, etc. are updated at regular intervals, and the latest values are always stored in the RAM 33.

As will be described later, the engine speed NE and the engine intake air amount GN are used as parameters representing the load conditions of the engine. On the other hand, the output port 36 of the control circuit 30
The drive circuit 48 is connected to the actuator 25b of the linear solenoid valve 25 to supply a control signal to the actuator 25b.

FIG. 4 is a diagram schematically showing a general opening / closing timing of the intake valve and the exhaust valve. In FIG. 4, TDC indicates the top dead center of the piston stroke, BDC indicates the bottom dead center, and IO, IC
Represents the opening timing and closing timing of the intake valve, respectively, and EO and EC represent the opening timing and closing timing of the exhaust valve, respectively.
As shown in FIG. 4, the intake valve is located at the top dead center (TDC) of the exhaust stroke.
The valve opens from the front and closes after the bottom dead center (BDC) of the intake stroke. The exhaust valve opens before the bottom dead center (BDC) of the explosion stroke, and closes after the top dead center (TDC) of the exhaust stroke. In FIG. 4, since the valve timing is set so that the intake valve opens (IO) before the exhaust valve closes (EC) in the exhaust stroke, both the intake valve and the exhaust valve are open ( FIG. 4 shows OL). In the present embodiment, the length (angle) of the OL is referred to as a valve overlap period. In this embodiment, the valve timing advance from the state where the valve timing of the intake valve is most retarded (FIG. 4, IO ₀ ) is defined as the valve timing VT. As can be seen from FIG. 4, in the present embodiment, the valve closing timing of the exhaust valve is fixed, so that the valve timing VT and the valve overlap amount O
L corresponds one-to-one. That is, the valve overlap period can be changed by changing the valve timing VT.

In this embodiment, the valve timing of the engine 1 is set in accordance with the engine operating conditions so that the timing at which the negative pressure wave generated by the exhaust pulsation reaches the exhaust port under each operating condition is included in the valve overlap period. Is done. FIG. 5 is a diagram schematically showing a change in the pressure of the cylinder exhaust port in each stroke of the solid line cylinder. As shown by the solid line in FIG. 5, when the exhaust stroke is started and the exhaust valve is opened, high-pressure gas in the cylinder flows out to the exhaust port and blowdown occurs, so that the pressure in the exhaust port rises. Positive pressure waves generated by this blow-down are exhausted from the exhaust manifold of each cylinder at the speed of sound.
1 and 52, from inside the exhaust pipe 530 toward the connection 540 with the exhaust pipe 550. However, the connecting portion 54
At 0, the two exhaust passages are exhaust pipes 55 having a large cross-sectional area.
The flow path is rapidly expanding to merge into zero, and the blow-down positive pressure wave is reflected at this flow-path rapidly expanding portion, the phase is reversed and becomes a negative pressure wave at the sound speed in the opposite direction toward the exhaust port. proceed. For this reason, as indicated by I in FIG. 5, immediately after the blowdown, when the reflected negative pressure wave reaches the exhaust port, the pressure in the exhaust port decreases. Further, since this negative pressure wave is repeatedly reflected between the exhaust port and the connection portion 540, the negative pressure wave due to the secondary reflection follows the negative pressure wave of the primary reflection shown by I in FIG. ) Negative pressure wave due to tertiary reflection (same III), positive pressure wave due to tertiary reflection (same IV), negative pressure wave due to tertiary reflection (same V), and reflected waves of each order gradually attenuate and arrive. The pressure at the exhaust port fluctuates alternately between positive pressure and negative pressure.

In this embodiment, as shown by the solid line in FIG.
The valve timing of each operating condition is set so that a valve overlap period (OL in FIG. 5) of the intake and exhaust valves occurs when the negative pressure wave due to the next reflection reaches the exhaust port and the exhaust port pressure decreases. By opening both the intake and exhaust valves when the exhaust port pressure is reduced in this way, in addition to discharging burned gas in the cylinder to the exhaust port, the introduction of fresh air from the intake port is promoted, The intake charging efficiency of the engine is improved.

However, when pressure wave reflection occurs at a portion other than the connection portion 540 of the exhaust pipe, the distance between the reflection portion and the exhaust port changes, so that the arrival timing of the tertiary negative pressure wave at the exhaust port changes. There is. When the θ pipe 530 is used in the exhaust system as in the present embodiment, the connecting portion 54
In addition to 0, for example, such reflection may occur at the connection portion 520 on the upstream side.

FIG. 6 is a sectional view showing an example of the structure of the connection portion 520. As shown in FIG. 6, the connection part 520 connects the exhaust manifold 510 and the exhaust pipe 530 with a gasket 513.
Through the respective flanges 515, 51
7 is fastened with a bolt 518 via a compression spring 519. For this reason, the exhaust manifold 51
A gap (clearance) C may be generated between the end of the partition wall 511 in the exhaust pipe 530 and the end of the partition wall 512 in the exhaust pipe 530. Such a gap C may occur from the time of shipment from the factory due to product tolerances of the exhaust manifold 510 and the exhaust pipe 530. Even if the gap C does not occur at the time of shipment from the factory, for example, the gasket 513 is settled (aging). May occur. If the size of the gap C is large to some extent, the exhaust passages 531 and 532 communicate with each other at this portion, causing a sudden expansion of the flow path, and the pressure wave is reflected at this portion.

When the reflection of the pressure wave occurs at the connection portion 520, the distance between the exhaust port and the reflection portion becomes shorter than the design value (ie, the distance between the connection portion 540 and the exhaust port). As shown by the dotted line, the arrival timing of the reflected waves of each order is advanced, and the arrival cycle of the reflected waves of each order is shortened. As a result, as shown by the dotted line in FIG. 5, the timing at which the third-order negative pressure wave reaches the exhaust port does not coincide with the valve overlap period, and the fourth positive-pressure wave reaches the exhaust port during the valve overlap period. become. In addition, the amplitude of the pressure wave increases as the gap C of the connection portion 520 increases, and the pressure rise of the exhaust port due to the fourth positive pressure wave also increases.

In this case, since the valve overlap occurs in a state where the exhaust port pressure rises due to the arrival of the fourth positive pressure wave, the intake charging efficiency drops below the design value, and the design output under each operating condition is reduced. The problem arises that it cannot be obtained. In the present embodiment, when the arrival timing of the negative pressure wave is shifted as described above and the valve overlap period OL does not coincide with the arrival timing of the third negative pressure wave in the design valve timing, the valve timing VT is retarded. Then, the valve overlap period is changed to the position indicated by OL 'in FIG. That is, the valve timing is changed so that the arrival timing of the fifth-order negative pressure wave instead of the third-order negative pressure wave coincides with the valve overlap period. As a result, even when the arrival timing of the negative pressure wave changes, it is possible to maintain the intake charging efficiency substantially at the design value.

As described above, to change the valve overlap period in accordance with the negative pressure wave arrival timing, three
Detecting that the timing of the next negative pressure wave reaching the exhaust port has changed from the design value and detecting the timing of the fifth negative pressure wave reaching the exhaust port, and furthermore, the valve overlap period so as to coincide with the arrival timing of the fifth negative pressure wave Need to be changed. In the present embodiment, the detection of the negative pressure wave arrival timing and the change of the valve overlap period are performed using one of the two methods described below.

First, a first method of detecting the negative pressure wave arrival timing and changing the valve overlap period will be described. In this method, the detection of the negative pressure wave arrival timing and the change of the valve overlap period are performed based on the engine intake air weight flow rate detected by the air flow meter 15. As previously mentioned,
In a state where the timing of arrival of the tertiary negative pressure wave at the exhaust port changes and does not coincide with the valve overlap period, the intake charging efficiency of the engine decreases, and the intake air mass flow rate of the engine falls below the design value. Further, the greater the change in the arrival timing of the negative pressure wave, the greater the decrease in the intake air amount.
Therefore, in the present embodiment, when the difference between the actual intake air weight flow rate detected by the air flow meter 15 and the design value is equal to or greater than a predetermined value, it is determined that the tertiary negative pressure wave arrival timing has changed, and the intake air The valve timing VT is retarded in accordance with the difference between the design value of the weight flow rate and the actually measured value so that the valve overlap period matches the fifth-order negative pressure wave arrival timing. As a result, the valve overlap period is set as shown in FIG.
OL ′, and the intake charging efficiency substantially equal to the design value can be obtained.

FIG. 7 is a flow chart showing details of the operation of detecting the negative pressure wave arrival timing and changing the valve timing. This operation is performed as a routine executed by the control circuit 30 at regular intervals. In FIG. 7, in step 701, an engine speed NE, an intake air weight flow rate G, and an intake air weight flow rate GN per one rotation of the engine as parameters of the engine load are read. Then, in step 703, it is determined whether the negative pressure wave arrival timing detection condition is satisfied. As described above, in the present embodiment, the negative pressure wave arrival timing is detected based on the engine intake air weight flow rate G.
Is preferably large and stable. Therefore, in step 703, the engine load is
When it is a large value close to OT (full load) and the engine speed is stable, it is determined that the negative pressure wave arrival timing detection condition is satisfied.

[0044] When the detection condition is not satisfied in step 703, then the design value G ₀ of the intake air weight flow rate in terms of the engine speed NE read and load GN at step 705 At step 701 are calculated You. The value of G ₀ is measured by actually operating the engine in advance by changing the conditions of NE and GN, and storing the measurement result in the ROM 32 of the control circuit 30 in the form of a numerical table using NE and GN. Yes,
In step 705 determines the value of G ₀ based on this map.

Next, in step 707, step 70
The actual intake air amount G read in 1 is calculated by the above.
Design intake air volume G₀Has decreased by more than the predetermined value α
Determine whether or not. In step 707, G <G₀−α
The actual intake air amount G is equal to the design value G₀Lower
The arrival timing of the negative pressure wave has changed from the design value.
Valve tie after step 709
Perform the changing operation. Where α is a positive value and the disturbance
Valve timing after step 709 by mistake
Judgment values (design suction
Air volume G₀With the appropriate size of dead zone added to
is there. Therefore, in step 707, G ≧ G ₀−α
In this case, the valve tie of step 709 and step 711
The process proceeds to step 713 while skipping the mining change operation.
Step 709 and step 711 valve timing change
In the re-operation, first, the design intake air amount G₀And the actual intake air
The difference ΔG from the quantity G is calculated (step 709), and then
Of valve timing delay amount ΔVT based on ΔG of
(Step 711). ΔVT is valve overlap
The period is indicated by OL 'in FIG.
The amount of retard required to match
You. FIG. 8 shows the reduction amount ΔG of the intake air amount and the valve timing.
FIG. 6 is a diagram showing a relationship with a retardation amount ΔVT. As mentioned above
If the negative pressure wave arrival timing changes greatly,
Accordingly, the amount of decrease ΔG of the intake air amount also increases. Actual
The relationship between ΔG and ΔVT can be determined by experiments, etc.
Although preferred, in the present embodiment, as shown in FIG.
The value is set so that it varies approximately linearly with ΔG.
ing.

As described above, the valve timing retard amount ΔVT
After the calculation, in step 713, the target value (valve timing design value) tVT of the valve timing VT is determined based on the values of NE and GN read in step 701. FIG. 9 shows the target valve timing tVT and the engine speed N.
FIG. 9 is a diagram showing a relationship between E and a load GN. In the present embodiment, as shown in FIG. 9, the valve timing VT is set to be the largest in the medium load / medium rotation region.

Then, in step 715, step 7
In step 717, the value of the target valve timing tVT determined in step 15 is retarded by the retard amount ΔVT calculated in step 713, and in step 717, the above-described linear solenoid is adjusted so that the actual valve timing VT becomes the corrected target valve timing tVT. The operation amount of the actuator 25 is feedback-controlled. Thus, the valve overlap period coincides with the arrival time of the fifth-order negative pressure wave, thereby preventing a reduction in intake air charging efficiency.

It should be noted that if the above-mentioned detection condition is not satisfied in step 703, and that G ≧ G ₀ −
If it is α, step 715 is executed using the value of the retard amount ΔVT calculated by the previous execution of the routine. In the present embodiment, the initial value of ΔVT is set to 0. As a result, if the negative pressure wave arrival timing has never changed, the value of ΔVT is kept at 0, so that the retard correction is not substantially performed in step 717. In addition, when the negative pressure wave arrival timing changes and the intake charging efficiency recovers due to the retard correction (when G ≧ G ₀ −α again at step 707), the retard amount ΔVT set at step 711 becomes smaller. Since it is used thereafter, the intake filling efficiency is kept high.

Next, a second method of detecting the arrival timing of the negative pressure wave and changing the valve overlap period will be described.
In this method, the pressure sensor 70 provided in the exhaust branch pipe 41 of the first cylinder of the engine 1 detects the exhaust pressure fluctuation in the branch pipe 41, thereby directly detecting the arrival timing of the negative pressure wave, If the timing has changed by a predetermined value or more, the valve timing is changed so that the valve overlap period matches the fifth-order negative pressure wave arrival timing.

FIG. 10 is a timing chart similar to FIG. 5 for explaining the principle of changing the valve timing according to the present method. The solid line in FIG. 10 shows the exhaust pressure fluctuation detected by the pressure sensor 70 in a normal case (a state in which the negative pressure wave arrival timing has not changed). In FIG. 10, point A is 3
The timing when the next negative pressure wave reaches the position of the pressure sensor 70, that is, the moment when the exhaust pipe pressure detected by the sensor 70 changes from the positive pressure to the negative pressure due to the secondary positive pressure wave passing through the pressure sensor 70, Show. In addition, FIG. 10 CA3 ₀
Is the crank angle at this time. As shown in FIG. 10, the negative pressure wave arrival timing CA3 ₀ are expressed in crankshaft rotation angle to the exhaust TDC of # 1 cylinder (the exhaust stroke top dead center).

In this embodiment, when the arrival timing of the negative pressure wave changes from this state, as shown by the dotted line in FIG. 10, the arrival timing of the tertiary negative pressure wave is earlier than the normal state by the crank angle β or more. Perform the valve timing change operation. That is, the phase reversal timing CA3 of the exhaust pressure detected by the pressure sensor, the valve timing change operation is executed when it becomes CA3 ≧ CA3 ₀ + beta. In the valve timing changing operation, the moment the fifth negative pressure wave after the timing change reaches the pressure sensor 70 (FIG. 10, B
3) in the normal state.
The next negative pressure wave arrival timing CA3 _0, the difference between the fifth-order negative pressure wave arrival timing CA5 after the change .DELTA.VT (.DELTA.VT = C
A3 ₀ -CA5) retards the valve timing.
The time from when the negative pressure wave passes through the pressure sensor to when it reaches the exhaust port is determined only by the distance from the pressure sensor 70 to the exhaust port and the speed of sound, and is substantially constant regardless of the presence or absence of a change in valve timing. On the other hand, the valve timing of the normal is set to negative pressure wave of a cubic reaching the pressure sensor valve overlap is started in accordance with the time to reach the exhaust port at the timing of CA3 _0. Therefore, the normal valve timing is set to Δ
If the VT (= CA3 ₀ -CA5) is retarded, the valve overlap starts when the changed fifth-order negative pressure wave reaches the exhaust port, and the valve overlap period is set to the fifth-order. The timing of the arrival of the negative pressure wave at the exhaust port can be matched. Therefore, the valve timing when the negative pressure wave arrival timing changes .DELTA.VT (= CA3 ₀
By retarding by −CA5), the fifth-order negative pressure wave can be effectively used, and the intake charging efficiency can be maintained almost as designed.

FIG. 11 shows the pressure cells of the third and fifth negative pressure waves.
Showing an operation for detecting the arrival timing of the sensor 70.
It is a low chart. This operation is performed by the control circuit 30.
This is performed as a routine executed at regular time intervals. FIG.
In step 1101, the crankshaft rotation angle
The current crankshaft rotation position CA detected by the sensor 44 and
The exhaust pressure PE detected by the pressure sensor 70 is read.
In step 1103, the first cylinder exhaust stroke is started from CA.
Crankshaft rotation angle CA to top dead center₁Is calculated. So
Then, in step 1105, the current exhaust pressure PE becomes negative.
Value or not, and in step 1107, execute the previous routine
Exhaust pressure PE_i-1Is determined to be a positive value. P
E ≦ 0 and PE_i-1If ≧ 0, the previous routine
The exhaust pressure is correct between the time of execution and the time of execution of this routine.
From the negative to the current negative pressure wave is a pressure sensor
Can be determined. Therefore, step 11
In step 09 and step 1113, this negative pressure wave is generated after the exhaust valve is opened.
Whether or not it is the negative pressure wave that has reached the second time (third negative pressure wave), and
Judges whether or not the third pressure wave arrived at the third time (fifth-order negative pressure wave)
If it is a third-order negative pressure wave, then in step 1103
Calculated crankshaft rotation angle CA₁To the third-order negative pressure wave arrival
In case of negative pressure wave of 5th order as iming CA3
Has CA₁As the fifth-order negative pressure wave arrival timing CA5
Each is stored (step 1111, step 111
5). At least one of steps 1105 and 1107
Above, or both steps 1109 and 1113
If not, the current crankshaft rotation angle CA ₁
Is the arrival timing of the third-order negative pressure wave or the fifth-order negative pressure wave
Since there is no data, the routine ends. This allows
Timing C of arrival of the third and fifth negative pressure waves to the pressure sensor 70
A3 and CA5 are detected.

FIG. 12 is a flowchart showing a valve timing changing operation based on the third and fifth negative pressure wave arrival timings CA3 and CA5 detected by the operation of FIG. This operation is also executed by the control circuit 30 at regular intervals. In FIG. 12, in step 1201, the engine speed NE and the engine load GN are read, and in step 1203, FIG.
The arrival timing CA3 of the current tertiary negative pressure wave detected by the operation 1 is normal timing (design timing) CA
3 ₀ than if it is earlier than β, ie, CA3> C
It is determined whether or not A3 ₀ + β. And CA3
If ≦ CA3 ₀ + β, it is determined that the amount of change in the negative pressure wave arrival timing is small, and the process proceeds to step 1207,
The valve timing retard amount ΔVT is set to 0, and the routine proceeds to step 1209. That is, in this case, the retard correction of the valve timing is not performed. Here, β is a value corresponding to the delay of the negative pressure wave arrival timing of such a degree that the reduction of the intake charging efficiency cannot be ignored.

On the other hand, in step 1203, CA3> CA3
If it is ₀ + β, it is determined that it is necessary to use the fifth-order negative pressure wave instead of the third-order negative pressure wave because the delay of the negative pressure wave arrival timing is large. The retardation correction amount ΔVT is given by ΔVT = CA
3 ₀ calculated as -CA5, executes step 1209 or less.

In step 1209, step 1201
The target valve timing tVT is determined from the relationship shown in FIG. 9 based on the read NE and GN. In step 1211, a value obtained by delay-correcting the target valve timing by ΔVT is set as a new target valve timing tVT. In step 1213, the linear solenoid actuator 25 is feedback controlled so that the engine valve timing VT becomes the corrected target valve timing tVT.

When the negative pressure wave arrival timing changes by the operation of FIG. 12, the valve overlap period of the engine is changed in accordance with the arrival time of the fifth negative pressure wave instead of the third negative pressure wave. Therefore, the intake charging efficiency of the engine is maintained at a substantially designed value. In the above-described embodiment, the variable valve timing mechanism 10 is described as an example in which only the opening / closing timing of the intake valve is changed. However, a variable valve timing mechanism in which only the opening / closing timing of the exhaust valve is changed, Alternatively, even when a variable valve timing mechanism that changes the opening and closing timing of both the intake and exhaust valves is used, it is needless to say that the intake charging efficiency can be maintained high irrespective of the negative pressure wave arrival timing change. .

[0057]

As described above, according to the invention described in each claim, the timing at which the negative pressure wave due to exhaust pulsation reaches the exhaust port due to exhaust pulsation is changed from the design value due to variations due to product tolerances of individual exhaust pipes and aging. Even in the case of a change, a common effect is achieved in which the intake pressure efficiency of the engine can be improved by effectively utilizing the negative pressure wave.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment in which the present invention is applied to an internal combustion engine for a vehicle.

FIG. 2 is a sectional view showing a structure of a θ pipe.

FIG. 3 is a diagram illustrating a configuration of a variable valve timing mechanism used in the embodiment of FIG.

FIG. 4 is a diagram illustrating a valve overlap period of the intake and exhaust valves.

FIG. 5 is a timing chart showing pressure fluctuation of an exhaust port during operation of the engine.

FIG. 6 is a cross-sectional view illustrating an example of a configuration of a θ pipe connection unit.

FIG. 7 is a flowchart showing a valve timing changing operation of the embodiment of FIG. 1;

FIG. 8 is a diagram illustrating setting of a valve timing retard amount in FIG. 7;

FIG. 9 is a diagram illustrating setting of a target valve timing in FIG. 7;

FIG. 10 is a timing chart for explaining another embodiment of the valve timing changing operation of the embodiment of FIG. 1;

FIG. 11 is a flowchart illustrating an operation of detecting a negative pressure wave arrival timing.

FIG. 12 is a flowchart showing a valve timing changing operation of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 10 ... Variable valve timing mechanism 15 ... Air flow meter 70 ... Exhaust pressure sensor 510 ... Exhaust manifold 520, 540 ... Connection part 530, 550 ... Exhaust pipe

Claims (5)

[Claims] 1. A valve timing adjusting means for changing at least one of an intake valve and an exhaust valve timing of an internal combustion engine, and a negative valve for detecting a timing at which a negative pressure wave generated by exhaust pulsation in an exhaust passage reaches an exhaust port. Pressure wave arrival time detection means, and control means for controlling the valve timing adjustment means to change the valve timing according to the arrival time of the negative pressure wave detected by the negative pressure wave arrival time detection means at the exhaust port. A valve timing control device for an internal combustion engine. 2. The valve control device according to claim 1, wherein the control unit controls the valve timing adjusting unit such that the negative pressure wave reaches the exhaust port within a valve overlap period between the intake valve and the exhaust valve. 3. The valve timing control device according to claim 1. 3. The negative pressure wave arrival timing detecting means includes an intake air amount detecting means for detecting an engine intake air amount, and based on the engine intake air amount when the engine is operated under predetermined conditions. The valve timing control device according to claim 1, wherein a timing at which the pressure wave reaches an exhaust port is detected. 4. The negative pressure wave reaching timing detecting means includes a pressure detecting means disposed in an exhaust passage, and detects a timing of the negative pressure wave reaching an exhaust port based on a change in exhaust pressure detected by the pressure detecting means. The valve timing control device according to claim 1. 5. A valve timing control device for an internal combustion engine provided with an exhaust passage having a connection portion, wherein the valve timing adjusting means changes at least one of an intake valve and an exhaust valve of the internal combustion engine; The arrival time of the negative pressure wave generated by the pulsation at the exhaust port is
Negative pressure wave arrival time detecting means for detecting that a change has occurred due to the occurrence of a clearance in the exhaust passage connection portion, When a change in the negative pressure wave reaching the exhaust port is detected by the negative pressure wave reaching time detecting means, A valve timing for an internal combustion engine comprising a control means for controlling the valve timing adjusting means to change the valve timing so that the negative pressure wave reaches an exhaust port during a valve overlap period between an intake valve and an exhaust valve. Control device.