JP2010281249A - Internal combustion engine equipped with exhaust supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine equipped with an exhaust supercharger, having improved fuel efficiency while suppressing the occurrence of knocking by recovering exhaust heat by the exhaust supercharger and increasing a geometric compression ratio by a delayed closing timing for an intake valve. <P>SOLUTION: The internal combustion engine includes a variable valve timing device for controlling a closing timing Ic for the intake valve between a maximum advanced closing timing Iac and a maximum delayed closing timing Irc depending on an engine operating condition, and a supercharging pressure control device for controlling the supercharging pressure by the exhaust supercharger. When the engine operating condition is in a high load, the supercharging pressure control device controls the supercharging pressure to be set to supercharging pressure with intake average pressure in an intake stroke higher than exhaust average pressure in an exhaust stroke and the variable valve timing device sets the closing timing Ic for the intake valve to a predetermined closing timing Ipc delayed from the maximum advanced closing timing Iac, or to the maximum delayed closing timing Irc. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine including an exhaust supercharger that performs supercharging using exhaust gas, and a variable valve timing device that can change the closing timing of an intake valve in accordance with an engine operating state.

An internal combustion engine includes an exhaust supercharger (for example, an exhaust turbocharger) and a variable valve timing device capable of changing a closing timing of an intake valve, and is specified based on an engine operation state (for example, an engine rotational speed). It is known that the variable valve timing device increases the charging efficiency by setting the closing timing of the intake valve to the early closing timing or the late closing timing according to the operating state) (for example, Patent Document 1).
The internal combustion engine includes a variable valve timing device that can change the closing timing of the intake valve in accordance with an engine operating state (for example, an operating state specified based on the engine speed and the engine load). However, there is also known one having an intake cam that defines a trapezoidal lift curve (for example, Patent Document 2).

Japanese Patent Laid-Open No. 3-168328 JP 2004-68755 A

In an internal combustion engine equipped with a supercharger, knocking is likely to occur when the engine load is high due to an increase in charging efficiency due to supercharging. Since it is small, knocking is more likely to occur than during high-speed rotation. Therefore, in order to suppress the occurrence of knocking, a compression ratio (hereinafter referred to as “geometric compression ratio”), which is a ratio of the volume of the combustion chamber at the intake bottom dead center and the volume of the combustion chamber at the compression top dead center. A so-called fuel cooling is carried out by setting a small value or increasing the fuel amount to lower the combustion temperature. However, the reduction in the thermal efficiency due to the reduction in the geometric compression ratio and the need for extra fuel for cooling cause the fuel efficiency of an internal combustion engine equipped with a supercharger to deteriorate.
Further, in an internal combustion engine having a large geometric compression ratio, as a countermeasure for suppressing knocking, the combustion chamber volume at the start of closing of the intake valve (at the start of substantial compression of intake) and the combustion chamber at the compression top dead center When the intake valve closing timing is retarded in order to reduce the effective compression ratio, which is the ratio to the volume, the intake valve lift amount is relatively large by using an intake cam having a trapezoidal lift curve. By increasing the valve opening period at, the pump loss due to the throttle of the intake valve can be reduced and the charging efficiency can be increased. On the other hand, in the lift amount increase region where the lift amount increases in the lift curve of the intake cam, a cam follower (for example, a rocker arm) that is interposed between the intake cam and the intake valve and contacts the intake cam is temporarily removed from the intake cam. When a valve jump occurs in which the intake valve opens and the intake valve does not follow the intake cam, the valve in a portion corresponding to the upper base of the trapezoidal lift curve in the intake cam (hereinafter referred to as “cam peak summit”). A valve bounce that rebounds after the cam follower and the intake valve that have stopped following the intake cam due to the jump collide with the cam top. Since this valve bounce affects the lift amount, the lift amount accuracy of the intake valve by the intake cam is lowered.

  The present invention has been made in view of such circumstances, and in an internal combustion engine including an exhaust supercharger, a geometric compression ratio is obtained by collecting exhaust heat by the exhaust supercharger and retarding the closing timing of the intake valve. The purpose of this is to improve fuel efficiency while suppressing the occurrence of knocking. Another object of the present invention is to suppress valve bounce at the intake cam that enables the intake valve to be closed slowly while improving the charging efficiency.

The invention according to claim 1 uses an intake valve (9) and an exhaust valve (10) for opening and closing an intake port (7) and an exhaust port (8) that open to the combustion chamber (6), respectively, and exhaust gas. The engine is operated between an exhaust supercharger (40) for pressurizing intake air and the closing timing (Ic) of the intake valve (9) between a maximum advance closing timing (Iac) and a maximum retard closing timing (Irc). In an internal combustion engine comprising a valve operating device (20) including a variable valve timing device (M) that is controlled according to a state, and a supercharging pressure control device (50) that controls a supercharging pressure according to the engine operating state. When the engine operating state is a high load, the supercharging pressure control device (50) exhausts the supercharging pressure by means of the intake mean pressure (Pi) in the combustion chamber (6) during the intake stroke. It becomes higher than the average pressure (Pe) during exhaust in the combustion chamber (6) during the stroke The variable valve timing device (M) controls to a constant supercharging pressure, and the variable valve timing device (M) delays the closing timing (Ic) from the maximum advance closing timing (Iac) or the closing timing (Ipc) The internal combustion engine has a maximum retarded closing timing (Irc).
According to this, when the internal combustion engine is under a high load, the supercharging pressure control device is in a state in which the average pressure during intake is greater than the average pressure during exhaust (hereinafter referred to as “positive pump work”). Therefore, of the thermal energy generated by the internal combustion engine, the thermal energy of the exhaust gas is recovered by the exhaust supercharger and converted to positive pump work. In addition, the variable valve timing device delays the intake valve closing timing from the maximum advance closing timing to the predetermined closing timing or the maximum retarded closing timing when the internal combustion engine is heavily loaded. Therefore, even if the geometric compression ratio is increased, the occurrence of knocking can be suppressed.
According to a second aspect of the present invention, in the internal combustion engine according to the first aspect, the variable valve timing device (M) sets the closing timing (Ic) to the maximum delay angle when the engine operating state is a low speed rotation high load. The closing time (Irc) is set.
According to this, the variable valve timing device sets the closing timing of the intake valve to the maximum retarded closing timing when the engine speed is low and the engine speed is low compared to when the internal combustion engine is high speed and high load. Since the effective compression ratio can be minimized, the occurrence of knocking can be suppressed even if the geometric compression ratio is greatly increased.
According to a third aspect of the present invention, in the internal combustion engine according to the first or second aspect, the variable valve timing device (M) sets the closing timing (Ic) to the maximum advance when the engine operating state is a low load. When the angle closing time (Iac) is set and the closing time (Ic) is the maximum advance angle closing time (Iac), the lift amount (L) of the intake valve (9) at the intake bottom dead center is the intake air amount. This is one half or more of the maximum lift amount (Lm) of the valve (9).
According to this, since the variable valve timing device sets the closing timing of the intake valve to the maximum advance closing timing when the internal combustion engine is lightly loaded, the return of the intake air through the intake valve in the valve opening state is higher than when the load is high. The filling efficiency is improved. Also, when the intake valve closes at the maximum advance angle, the intake valve lift amount at the intake bottom dead center is ½ or more of the maximum lift amount. Even during the time period, a mirror cycle for the slow closing of the intake valve with a relatively large retardation amount can be realized.
According to a fourth aspect of the present invention, in the internal combustion engine according to any one of the first to third aspects, the variable valve timing device (M) drives the intake valve (9) to open and close and the intake valve (9). ), And the lift curve (C) is a maximum lift point at which the lift amount (L) of the intake valve (9) becomes the maximum lift amount (Lm). With respect to (Cm), the lift amount (L) continuously increases until the lift amount (L) reaches the maximum lift point (Cm) from the valve opening start point (Co), and the lift amount ( L) has a lift amount decrease region (Cb) that continuously decreases from the maximum lift point (Cm) to the valve closing start point (Cc), and the lift amount decrease region (Cb) increases the lift amount. The maximum lift point (Cm) in the region (Ca) and the It has a decrease start side region (Cbs) located on the side where the lift amount (L) is large with respect to a virtual straight line (S) passing through the valve start point (Cc), and the decrease start side region (Cbs) Small boundary region (Cb1) on the maximum lift point (Cm) side and large on the valve closing start point (Cc) side, with the boundary (Cb3) where the distance from the virtual straight line (S) is maximum. The lift amount decrease rate in the small decrease region (Cb1) and the boundary portion (Cb3) is smaller than the lift amount decrease rate in the large decrease region (Cb2). The rotation angle range (A1) of the intake cam (23) across the small decrease region (Cb1) and the boundary portion (Cb3) is the rotation angle range of the intake cam (23) in the large decrease region (Cb2) ( It is larger than A2).
According to this, in the intake cam in which the charging efficiency is increased because the rotation angle range over the small decrease region and the boundary in the lift amount decrease region of the lift curve is larger than the rotation angle range in the large decrease region, When the intake valve valve jump occurs in the lift amount increase area and the intake valve that temporarily stops following the intake cam due to the valve jump returns to the intake cam in the small decrease area of the lift curve, the intake cam Since the lift amount of the valve is reduced, the impact force on the intake valve at the time of return is reduced compared to the case of returning to the intake cam in a state where the lift amount is not reduced.
According to a fifth aspect of the present invention, in the internal combustion engine of the fourth aspect, when the closing timing (Ic) is the maximum advance closing timing (Iac), the timing (Iab) that becomes the boundary portion (Cb3) is When the closing timing (Ic) is the maximum retarded closing timing (Irc), it is closer to the intake bottom dead center than the timing (Irb) at which the boundary portion (Cb3) is reached.
According to this, when the closing timing of the intake valve is the maximum advance closing timing, in the lift amount decrease region where the lift amount of the intake valve decreases, the boundary that defines the end point of the small decrease region where the lift amount decrease rate is small Since the part is at a time relatively close to the intake bottom dead center, it is possible to realize a mirror cycle of the slow closing of the intake valve with a relatively large retardation amount.

According to the first aspect of the present invention, when the internal combustion engine is at a high load, the heat energy (exhaust heat) of the exhaust gas is recovered by the exhaust supercharger and converted into positive pump work, and the intake valve is closed. Since the effective compression ratio can be reduced by retarding the timing from the maximum advance timing, the occurrence of knocking can be suppressed even when the geometric compression ratio is increased. As a result, while suppressing the occurrence of knocking, the thermal efficiency can be improved by increasing the positive pump work and the geometric compression ratio, thereby improving the fuel efficiency.
According to the second aspect of the present invention, the effective compression ratio can be minimized by retarding the closing timing of the intake valve to the maximum at the time of low speed rotation and high load of the internal combustion engine. Therefore, when the geometric compression ratio is increased In addition, the occurrence of knocking can be suppressed. As a result, while suppressing the occurrence of knocking, the geometric compression ratio can be increased to the maximum and the thermal efficiency can be improved, so that the fuel efficiency is improved.
According to the third aspect of the present invention, when the internal combustion engine is at a low load, the closing timing of the intake valve is advanced and advanced to the maximum as compared with a high load, so that the charging efficiency is improved by reducing the blowback. Further, even at low load, the heat efficiency can be improved by the mirror cycle in which the delay amount of the slow closing of the intake valve is large with respect to the intake bottom dead center, so that the fuel efficiency is improved.
According to the fourth aspect of the present invention, in the intake cam in which the rotation angle range over the small decrease region and the boundary portion in the lift amount decrease region is larger than the rotation angle range in the large decrease region, the valve jump occurs in the lift amount increase region. When this occurs, the impact force when the intake valve returns to the intake cam in the small decrease region is reduced and valve bounce is suppressed, so that the lift amount accuracy of the intake valve by the intake cam can be improved.
According to the fifth aspect of the present invention, even when the closing timing of the intake valve is the maximum advance timing, the thermal efficiency is improved by the mirror cycle in which the delay amount of the late closing of the intake valve is large with respect to the intake bottom dead center. Can improve fuel efficiency.

1 is a schematic view of a main part of an internal combustion engine to which the present invention is applied, in which the engine body is shown as a plan view. It is principal part sectional drawing in the general II-II line | wire of FIG. It is a figure which shows the relationship between the lift amount and crank angle of the intake valve and exhaust valve of the internal combustion engine of FIG. It is a figure which shows the lift curve of the intake valve of the internal combustion engine of FIG. It is a figure explaining the engine operating state of the internal combustion engine of FIG. FIG. 2 is a schematic PV diagram for explaining each stroke, an exhaust-side average pressure, and an intake-side average pressure of the internal combustion engine of FIG. 1.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIGS. 1 and 2, an internal combustion engine to which the present invention is applied (hereinafter referred to as “internal combustion engine”) includes one or more cylinders 1a, four cylinders 1a as a plurality in this embodiment, and each cylinder. 1 is a multi-cylinder internal combustion engine including a piston 4 slidably fitted to 1a and a crankshaft 5 connected to each piston 4 via a connecting rod, and is used as a power source for a vehicle to be used. The

The internal combustion engine includes a cylinder block 1 in which four cylinders 1 a are arranged in series, a cylinder head 2 coupled to the upper end portion of the cylinder block 1, and a head cover coupled to the upper end portion of the cylinder head 2. 3 is provided.
A combustion chamber 6 is formed by the cylinder 1a, the piston 4, and the cylinder head 2 between the piston 4 and the cylinder head 2 in the cylinder axial direction for each cylinder 1a.
The cylinder head 2 includes, for each cylinder 1a (or each combustion chamber 6), an intake port 7 having a pair of intake ports 7a opened to the combustion chamber 6 and an exhaust port 8 having a pair of exhaust ports 8a. A pair of intake valves 9 and a pair of exhaust valves 10 for opening and closing the pair of intake ports 7a and the pair of exhaust ports 8a, respectively, and an ignition plug 11 facing the combustion chamber 6 are provided.
In the embodiment, the vertical direction is a direction parallel to the cylinder axis Y (that is, the cylinder axis direction), and the upper direction is the direction in which the combustion chamber 6 is located with respect to the rotation center line of the crankshaft 5 in the vertical direction. Suppose that

The internal combustion engine further includes a valve gear 20 that opens and closes the intake valve 9 and the exhaust valve 10, an air cleaner 12 b that takes in outside air, and an intake passage 12 a that guides the intake air to the combustion chamber 6 through the intake port 7. An intake device 12, a fuel injection valve (not shown) that injects fuel into the intake air to form an air-fuel mixture, and an exhaust port 8 that uses combustion gas generated by combustion of the air-fuel mixture in the combustion chamber 6 as exhaust gas. An exhaust device 13 that forms an exhaust passage 13a that leads to the outside of the internal combustion engine through the exhaust gas, an exhaust turbocharger 40 that serves as an exhaust supercharger that pressurizes intake air from the air cleaner 12b using the energy of the exhaust gas, And a supercharging pressure control device 50 that controls a supercharging pressure that is the pressure of the intake air pressurized by the exhaust turbo supercharger 40.
The geometric compression ratio of an internal combustion engine in which four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke (see FIG. 6) are one cycle is, for example, the geometric compression ratio of a naturally aspirated internal combustion engine having the same displacement Although it is set to the same value, it may be set to a larger value.

The intake device 12 includes a throttle valve 12 c disposed downstream of the compressor 41 of the exhaust turbocharger 40. The throttle valve 12c is driven by an electric motor 12d as a driving means that operates based on an operation amount of an accelerator operation member by a driver, and its opening is in a range from an idle opening as a minimum opening to a fully opened opening. Be controlled. The fuel injection valve injects fuel in the combustion chamber 6 or in the intake passage 12 a or the intake port 7.
The piston 4 is driven by the pressure of the combustion gas in the combustion chamber 6 to reciprocate, and rotationally drives the crankshaft 5 that is rotatably supported at the lower part of the cylinder block 1.

  The valve gear 20 is in contact with an intake cam shaft 21 having an intake cam 23 and an exhaust cam shaft 22 having an exhaust cam 24, and an intake cam as a valve cam while contacting the intake valve 9 and the exhaust valve 10. 23 and an exhaust cam 24, which are respectively driven by an intake cam follower that opens and closes the intake valve 9 and the exhaust valve 10, an exhaust rocker arm 26 as an exhaust cam follower, and the intake valve 9 and the exhaust valve 10 are always closed. The energizing valve spring 27, the rotation drive member 28 for rotating the camshafts 21 and 22 (and thus the cams 23 and 24) in synchronization with the rotation of the crankshaft 5, and the opening timing Io and closing of the intake valve 9 The valve timing control controlled by the operation control device 60 in order to be able to change the opening / closing timing I (see FIG. 3) consisting of the timing Ic. And a member 30.

An intake cam 23 and an exhaust cam 24 provided so as not to move relative to the intake cam shaft 21 and the exhaust cam shaft 22 are cam holders (not shown) that are provided on the cylinder head 2 and rotatably support the cam shafts 21 and 22. The intake valve 9 and the exhaust valve 10 are driven to open and close via the intake rocker arm 25 and the exhaust rocker arm 26 that are swingably supported by a pair of rocker shafts 25a and 26a.
The rotation drive member 28 is constituted by, for example, a winding transmission that transmits the power of the crankshaft 5 to the camshafts 21 and 22, and the camshafts 21 and 22 are rotated at half the rotational speed of the crankshaft 5. Rotating drive.

The valve timing control member 30 is a well-known device that causes relative rotation between the rotation drive member 28 and the intake camshaft 21, and is provided between the rotation drive member 28 and the intake camshaft 21 to be a crankshaft. 5, the phase of the intake cam 23 (synonymous with the intake cam shaft 21 in this embodiment) can be changed.
For example, the valve timing control member 30 is a hydraulic actuator that uses a part of oil discharged from a lubricating oil pump 14 included in the internal combustion engine as hydraulic oil, and a part of the hydraulic timing actuator 30 is shown in FIG. First and second rotating bodies 31 and 32 that are rotatable relative to each other are provided. Then, for the advance angle formed by the first rotating body 31 that is rotated and rotated integrally by the rotation driving member 28 and the second rotating body 32 that rotates integrally with the intake cam shaft 21 (and hence the intake cam 23). Supply / discharge of hydraulic oil to / from the hydraulic chamber 33 and the retarding hydraulic chamber 34 is controlled by the hydraulic control valve 15 (see FIG. 1) controlled by the operation control device 60 according to the engine operating state of the internal combustion engine. The relative rotation of the rotating bodies 31 and 32 changes the phase of the intake cam 23 with respect to the crankshaft 5 (therefore, the opening / closing timing I of the intake valve 9 (see FIG. 3)), and the operation for the hydraulic chambers 33 and 34. The hydraulic oil is confined in the hydraulic chambers 33 and 34 without supplying and discharging the oil, so that the rotating bodies 31 and 32 rotate integrally without relative rotation, and the crankshaft 5 is sucked. Phase of the cam 23 (and therefore, the opening and closing timing of the intake valve 9 I (see FIG. 3)) is held.
On the other hand, the phase of the exhaust cam 24 with respect to the crankshaft 5 (therefore, the opening / closing timing E (see FIG. 3) consisting of the opening timing Eo and the closing timing Ec of the exhaust valve 10) depends on changes in the engine operating state in this embodiment. It remains the same without
The rotation drive member 28, the valve timing control member 30, the intake camshaft 21, and the intake cam 23 are controlled by the operation control device 60, so that the phase of the intake cam 23 with respect to the crankshaft 5 according to the engine operating state. Therefore, a variable valve timing device M that controls the opening / closing timing I of the intake valve 9 to be changeable is configured.

  As shown in FIG. 3, the cam shape of each intake cam 23 and each exhaust cam 24 (see FIG. 2) is the intake angle that is the crank angle of the crankshaft 5 between the opening timing Io and the closing timing Ic of the intake valve 9. The valve opening period Ai is set to be longer than the exhaust valve opening period Ae which is the crank angle between the opening timing Eo and the closing timing Ec of the exhaust valve 10.

Referring to FIG. 4, each intake cam 23 defines a lift curve C that sets a change characteristic of the lift amount L of the intake valve 9 with respect to a crank angle (or a cam angle that is ½ of the crank angle).
A lift curve C, which is a curve similar to a trapezoid, shows a valve opening start point Co () at the opening timing Io with respect to the maximum lift point Cm at which the lift amount L of the intake valve 9 becomes the maximum lift amount Lm at the maximum lift timing Im. The lift amount L is 0 (zero).) From the maximum lift point Cm to the closing timing Ic, the lift amount increase region Ca in which the lift amount L continuously increases as the intake cam 23 rotates until the maximum lift point Cm is reached. A lift amount decrease region Cb in which the lift amount L continuously decreases as the intake cam 23 rotates up to the valve closing start point Cc (the lift amount L is 0 (zero)).

The lift amount decrease region Cb includes a decrease start side region Cbs and a decrease end side region where the lift amount L is divided by a virtual straight line S passing through the maximum lift point Cm and the valve closing start point Cc in the lift amount increase region Ca. Cbf. The decrease start side region Cbs is located on the side where the lift amount L is larger than the virtual straight line S, and the decrease end side region Cbf is located on the side where the lift amount L is small relative to the virtual straight line S.
The decrease start side region Cbs includes a small decrease region Cb1 on the maximum lift point Cm side separated by a boundary Cb3 where the distance from the virtual straight line S in the direction orthogonal to the virtual straight line S is maximum, and the start of valve closing And a large decrease region Cb2 on the point Cc side. In the boundary portion Cb3, the lift amount L of the intake valve 9 becomes the boundary lift amount Lb at the boundary time Ib.

The lift amount decrease rate in the small decrease region Cb1 and the boundary portion Cb3 is smaller than the lift amount decrease rate in the large decrease region Cb2.
In the small decrease region Cb1, when the lift amount L increases in the lift amount increase region Ca, the intake rocker arm 25 is separated from the intake cam 23, and the intake valve 9 and the intake rocker arm 25 (see FIG. 2) do not follow the intake cam 23. When the valve jump occurs, when the intake valve 9 and the intake rocker arm 25, which have temporarily stopped following the intake cam 23, return to the intake cam 23 in this small decrease region Cb1, that is, the intake rocker arm 25 again returns to the intake cam 23. It is a part for suppressing valve bounce that occurs when abutting, and constitutes an impact mitigation region that mitigates the impact when the intake cam 9 and the intake rocker arm 25 and the intake cam 23 abut on the valve jump, The lift amount reduction rate is set based on experiments from the viewpoint of suppressing valve bounce.

The rotation angle range A1 of the intake cam 23 across the small decrease region Cb1 and the boundary Cb3 is larger than the rotation angle range A2 of the intake cam 23 in the large decrease region Cb2 and the rotation angle range A3 of the intake cam 23 in the decrease end region Cbf. Is also big. The boundary lift amount Lb, which is the lift amount L at the boundary portion Cb3, is less than the maximum lift amount Lm and 3/4 or more of the maximum lift amount Lm.
In this embodiment, the small decrease region Cb1 is a curve in which the lift amount decrease rate gradually increases as the intake cam 23 rotates, but as another example, almost the entire small decrease region Cb1 may be a straight line. In the straight line portion, the lift rate reduction rate is constant with respect to the rotation of the intake cam 23.

Referring to FIG. 3, when the opening / closing timing I of the intake valve 9 is changed by the valve timing control member 30 (see FIG. 2) of the variable valve timing device M, the opening / closing timing I is the maximum advanced timing Ia. And the most retarded maximum retard timing Ir, while the intake valve opening period Ai is kept constant. In FIG. 3, the lift curve C at the maximum retard angle Ir is shown by a solid line, and the lift curve C at the maximum advance timing Ia is shown by a broken line.
The intake valve 9 (see FIG. 2) starts to open at the maximum advance angle Ia at the maximum advance angle Ia, and closes at the maximum advance timing Iac delayed from the intake bottom dead center. In addition, at the maximum retard angle Ir, the valve start is started at the maximum retard angle open timing Iro, and the valve is closed at the maximum retard angle close timing Irc that is delayed from the intake bottom dead center and the maximum advance angle close timing Iac. To do.

When the closing timing Ic is at the maximum retardation closing timing Irc, the maximum lift timing Im is on the advance side with respect to the intake bottom dead center, and the maximum retardation that is the boundary timing Ib at the maximum retardation timing Ir. The boundary time Irb is on the retard side with respect to the intake bottom dead center.
When the closing timing Ic is delayed from the maximum advance closing timing Iac and at a predetermined closing timing Ipc that is advanced from the maximum retard closing timing Irc, the boundary timing Ib is In accordance with the timing Ipc, the timing is located between the retard timing that is retarded from the intake bottom dead center and the advance timing that is advanced from the intake bottom dead center. In FIG. 3, as an example of the predetermined closing timing Ipc, a lift curve C when the boundary timing Ib becomes the retard side timing Ipr is indicated by a two-dot chain line.

  When the closing timing Ic is the maximum advance closing timing Iac, the lift amount L at the intake bottom dead center is 3/4 or less of the maximum lift amount Lm and 1/2 or more of the maximum lift amount Lm. Regarding the boundary timing Ib, the maximum advance boundary timing Iab when the closing timing Ic is the maximum advance closing timing Iac is greater than the maximum retard boundary timing Irb when the closing timing Ic is the maximum retard closing timing Irc. Near intake bottom dead center.

  Since the intake cam 23 has the above-described lift curve C, the period during which the intake valve 9 is opened with a large lift amount L can be increased, and the area surrounded by the lift curve C can be increased. Since the flow resistance of the intake air by the intake valve 9 can be reduced, the charging efficiency can be improved.

  Referring to FIG. 1, an exhaust turbocharger 40 driven by exhaust gas is disposed in an intake passage 12a and a compressor 41 as an intake air compression unit that pressurizes intake air, and an exhaust gas is disposed in an exhaust passage 13a. And a turbine 42 as an exhaust driving unit driven by the motor. A turbine 42 that is integrally connected to the compressor 41 via a drive shaft 43 pressurizes intake air by the compressor 41 using exhaust gas having a part of thermal energy generated by the internal combustion engine.

The supercharging pressure control device 50 that controls the supercharging pressure to be changeable according to the engine operating state by being controlled by the operation control device 60 is a supercharging pressure control member that controls the flow of exhaust gas flowing into the turbine 42. And an actuator 52 as a driving member that is provided in the exhaust turbocharger 40 and drives the variable vane 51.
One or more variable vanes 51 provided here in the exhaust turbocharger 40 are swingably disposed in the exhaust gas inlet passage to the turbine 42 in the exhaust passage 13a. The actuator 52 is controlled by the operation control device 60 according to the engine operating state, and by controlling the operating position of the variable vane 51, the passage area of the inlet passage is changed, the flow velocity of the exhaust gas is changed, As a result, the rotational speed of the turbine 42 is controlled, and the supercharging pressure is controlled.

As shown in FIG. 1, the internal combustion engine includes an operation control device 60 that controls its operation state. The operation control device 60 detects the engine state of the internal combustion engine 62, specifies the engine operating state of the internal combustion engine based on the engine state detected by the engine state detecting unit 62, and also determines the engine operating state. And an electronic control unit 61 for controlling the operation of the fuel injection valve, the electric motor 12d for the throttle valve 12c, the variable valve timing device M, and the supercharging pressure control device 50, respectively.
The electronic control unit 61 is composed of a computer including an input / output interface, a central processing unit, a control program, a storage device storing a map, and the like.

The engine state detection means 62 includes an engine rotation speed detection means 63 for detecting the engine rotation speed N of the internal combustion engine, an accelerator operation amount detection means 64 for detecting the operation amount of the accelerator operation member by the driver, and a throttle in the intake passage 12a. A supercharging pressure detection unit 65 that detects a supercharging pressure downstream of the valve 12c and an intake air amount detection unit 66 that detects an intake air amount are provided. In this embodiment, the accelerator operation amount detection means 64 constitutes an engine load detection means for detecting the engine load D of the internal combustion engine.
The electronic control unit 61 controls the hydraulic control valve 15 that controls the hydraulic oil that is sucked into and discharged from the valve timing control member 30 in accordance with the engine state detected by the engine state detection means 62, thereby changing the valve timing device. The supercharging pressure control device 50 is controlled by controlling M and similarly controlling the actuator 52.

With reference to FIGS. 1, 3, 5, and 6, the control of the supercharging pressure by the supercharging pressure control device 50 and the control of the opening / closing timing I of the intake valve 9 by the variable valve timing device M will be described.
As shown in FIG. 5, the engine operating state is higher than the idle rotational speed Ni with respect to the engine rotational speed N between the idle rotational speed Ni and the maximum rotational speed at the boundary rotational speed Nb. The engine load D is divided into a low-speed rotation of Nb or less and a high-speed rotation exceeding the boundary rotation speed Nb. The engine load D is less than the boundary load Db between the idle Di and the maximum load Dm. It is assumed that the load is divided into a low load and a high load exceeding the boundary load Db.
As an example, the boundary rotational speed Nb is the engine rotational speed N that divides the rotational speed range from the idle rotational speed Ni to the maximum rotational speed into substantially equal parts, or the engine speed N on the lower speed side when substantially divided into three parts. The boundary load Db is an engine load D that substantially bisects the load range from the idle Di to the maximum load Dm. However, the boundary rotational speed Nb may be an engine rotational speed N other than the engine rotational speed N when the engine is substantially divided into two or approximately three parts, and the boundary load Db is other than the engine load D that is divided into two parts. Engine load D may be used.

  The supercharging pressure control device 50 is controlled by the operation control device 60 so that when the internal combustion engine is at a low load and a high load except for a transient state from the idle Di, the combustion chamber 6 regardless of the engine speed N. As shown in FIG. 6, the boost pressure is controlled so that the intake average pressure Pi in the intake stroke becomes higher than the exhaust average pressure Pe in the exhaust stroke. . Here, the average pressure is an average value of the pressure in the combustion chamber 6 that fluctuates in the intake stroke or the exhaust stroke.

More specifically, based on experimental data obtained by measuring actual pressure changes in the combustion chamber 6 during the intake stroke and the exhaust stroke, using the engine speed N as a parameter when the exhaust turbocharger 40 is operated. Thus, a supercharging pressure is set at which the intake average pressure Pi is higher than the exhaust average pressure Pe regardless of the engine speed N at low and high loads of the internal combustion engine. Based on the experimental results, the set supercharging pressure at which the intake average pressure Pi becomes higher than the exhaust average pressure Pe with respect to the engine speed N and the engine load D is mapped, and the operation control device 60 is mapped. Is stored as a supercharging pressure map.
The supercharging pressure control device 50 is configured such that the actual supercharging pressure detected by the supercharging pressure detecting means 65 is detected by the engine rotational speed N and the engine load detected by the engine rotational speed detecting means 63 and the accelerator operation amount detecting means 64, respectively. The operating position of the variable vane 51 is controlled so that the set supercharging pressure obtained in the supercharging pressure map corresponding to D is obtained, and the supercharging pressure is feedback-controlled.

  The variable valve timing device M is controlled by the operation control device 60 to control the opening / closing timing I of the intake valve 9 according to the engine speed N and the engine load D. Specifically, it is as follows. In all engine operating states of the internal combustion engine, the effect of improving the thermal efficiency by the mirror cycle is exhibited.

When the engine operating state is a low load regardless of the engine rotational speed N (that is, a low-speed rotational low load or a high-speed rotational low load).
By the supercharging pressure control device 50 controlling the supercharging pressure to the set supercharging pressure, a positive pump work (that is, a state where the average pressure Pi during intake is larger than the average pressure Pe during exhaust) is obtained. , Improve thermal efficiency.
Due to the valve timing control member 30, the opening / closing timing I of the intake valve 9 becomes the maximum advance timing Ia, the effective compression ratio increases, and the intake air blows back to the intake port 7 through the intake valve 9 in the valve open state. As a result, the filling efficiency is improved. Further, since the opening timing Io becomes the maximum advance opening timing Iao, the valve overlap period is maximized, so that the amount of internal EGR that is the amount of exhaust gas remaining in the combustion chamber 6 increases, and the combustion chamber 6 The air-fuel mixture is heated and the combustibility is improved.

When the engine is operating at low speed and high load.
The thermal efficiency is improved by the positive pump work in the supercharging pressure control by the supercharging pressure control device 50.
The valve timing control member 30 causes the opening / closing timing I to become the maximum retardation timing Ir. For this reason, the closing timing Ic becomes the maximum retarded closing timing Irc, and the thermal compression efficiency can be improved by increasing the geometric compression ratio. On the other hand, the effective compression ratio decreases. The occurrence of knocking is suppressed.

When the engine is operating at high speed and high load.
The thermal efficiency is improved by the positive pump work in the supercharging pressure control by the supercharging pressure control device 50.
The valve timing control member 30 causes the closing timing Ic to be a predetermined closing timing Ipc that is retarded from the maximum advance closing timing Iac and advanced from the maximum retard closing timing Irc. For this reason, the closing timing Ic is retarded from the maximum advance closing timing Iac and the effective compression ratio is decreased, so that the occurrence of knocking is suppressed despite the increase in the geometric compression ratio, while the closing timing Ic is Compared with the maximum retarded closing timing Irc, the effective compression ratio is increased and the return of intake air to the intake port 7 is reduced, so that the charging efficiency is improved and the internal EGR amount is increased due to the increase of the valve overlap period. Thus, the air-fuel mixture in the combustion chamber 6 is heated to improve the combustibility.
Here, the predetermined closing timing Ipc can be advanced as the engine load D becomes smaller, or can be advanced within a range in which knocking is not detected by the knocking sensor when a knocking sensor is provided.

Next, operations and effects of the embodiment configured as described above will be described.
When the engine operating state of the internal combustion engine is a low speed rotation high load and a high speed rotation high load, the supercharging pressure control device 50 sets the supercharging pressure so that the intake average pressure Pi is higher than the exhaust average pressure Pe. The variable valve timing device M controls to the supercharging pressure, and the closing timing Ic of the intake valve 9 is set to a predetermined closing timing Ipc that is retarded from the maximum advance closing timing Iac for high speed rotation and high load, so that the low speed rotation is performed. For high loads, the maximum retarded closing timing Irc is used.
With this structure, when the internal combustion engine is under a high load, the supercharging pressure control device 50 controls the supercharging pressure to the set supercharging pressure at which positive pump work is obtained. Then, the heat energy of the exhaust gas is recovered by the exhaust turbocharger 40 and converted into positive pump work. At the same time, since the variable valve timing device M retards the closing timing Ic from the maximum advance closing timing Iac to the predetermined closing timing Ipc or the maximum retarded closing timing Irc, the effective compression ratio can be reduced at high loads. Even if the geometric compression ratio is increased, the occurrence of knocking can be suppressed.
Thus, when the internal combustion engine is under a high load, the heat energy (exhaust heat) of the exhaust gas is recovered by the exhaust supercharger and converted into positive pump work, and the closing timing Ic of the intake valve 9 is advanced to the maximum. Since the effective compression ratio can be reduced by retarding the angle closing timing Iac, the occurrence of knocking can be suppressed even when the geometric compression ratio is increased. As a result, while suppressing the occurrence of knocking, by improving the thermal efficiency by increasing the positive pump work and the geometric compression ratio, and by improving the thermal efficiency by the mirror cycle, fuel cooling for further knocking suppression becomes unnecessary. , Fuel efficiency is improved.

  Then, the variable valve timing device M changes the closing timing Ic of the intake valve 9 to the maximum retarded closing timing Irc when the engine speed N is smaller than that at the time of high speed rotation and high speed and knocking is likely to occur. Since the effective compression ratio can be minimized because the retardation is maximized, the occurrence of knocking can be suppressed even if the geometric compression ratio is greatly increased. As a result, at the time of low speed rotation and high load of the internal combustion engine, while suppressing the occurrence of knocking, the geometric compression ratio can be increased to the maximum and the thermal efficiency can be improved, so the fuel efficiency is improved.

  In addition, when the engine speed is high and the load is high, the effective compression ratio is increased compared to when the closing timing Ic is the maximum retarded closing timing Irc, and the recharging of the intake air to the intake port 7 is reduced, thereby improving the charging efficiency. In addition, the air-fuel mixture in the combustion chamber 6 is heated by the increase in the internal EGR amount due to the increase in the valve overlap period, and the combustibility is improved, thereby improving the fuel efficiency.

The variable valve timing device M sets the closing timing Ic of the intake valve 9 to the maximum advance angle closing timing Iac when the engine operating state is a low load, and when the closing timing Ic is the maximum advance angle closing timing Iac, The lift amount L of the intake valve 9 at the point is ½ or more of the maximum lift amount Lm of the intake valve 9.
With this structure, when the internal combustion engine is under a low load, the variable valve timing device M sets the closing timing Ic to the maximum advance angle closing timing Iac, so that the return of intake air through the intake valve 9 in the opened state is reduced compared to when the load is high. Thus, the filling efficiency is improved. Further, when the intake valve 9 is closed at the maximum advance closing timing Iac, the lift amount L of the intake valve 9 at the intake bottom dead center is equal to or greater than ½ of the maximum lift amount Lm. Even at the advance angle closing time Iac, it is possible to realize the mirror cycle of the late closing of the intake valve 9 with a relatively large amount of retardation.
Because of this effect, when the load is low, the closing timing Ic is advanced to the maximum as compared to when the load is high, so that the charging efficiency is improved by reducing the blow-back, and the intake bottom dead center is also reduced during the low load. On the other hand, the mirror cycle having a large delay amount of the slow closing of the intake valve 9 can improve the thermal efficiency, thereby improving the fuel efficiency.

  Further, even at low load, the supercharging pressure control device 50 controls the supercharging pressure to the set supercharging pressure at which positive pump work can be obtained, so that thermal efficiency is improved and fuel efficiency performance is also improved in this respect. improves. Further, when the load is low, the opening timing Io of the intake valve 9 becomes the maximum advance opening timing Iao, so that the valve overlap period is maximized, so that the internal EGR amount increases and the air-fuel mixture in the combustion chamber 6 increases. As the fuel is heated and the combustibility is improved, the fuel efficiency is improved.

  The lift curve C of the intake cam 23 has a lift amount increase region Ca and a lift amount decrease region Cb that increase, and the decrease start side region Cbs of the lift amount decrease region Cb is a small decrease region with the boundary Cb3 as a boundary. The lift amount decrease rate in the small decrease region Cb1 and the boundary portion Cb3 is smaller than the lift amount decrease rate in the large decrease region Cb2, and is divided into the small decrease region Cb1 and the boundary portion Cb3. The rotation angle range A1 of the intake cam 23 that crosses is larger than the rotation angle range A2 of the intake cam 23 in the large decrease region Cb2. With this structure, in the lift amount reduction region Cb of the lift curve C, the intake angle that increases the charging efficiency because the rotation angle range A1 over the small decrease region Cb1 and the boundary Cb3 is larger than the rotation angle range A2 in the large decrease region Cb2. In the cam 23, a valve jump of the intake rocker arm 25 and the intake valve 9 occurs in the lift amount increasing region Ca, and the intake rocker arm 25 and the intake valve 9 that have temporarily stopped following the intake cam 23 due to the valve jump are small. When returning to the intake cam 23 in the decrease region Cb1 and the intake rocker arm 25 comes into contact with the intake cam 23, the intake cam 23 is in a state of decreasing the lift amount L of the intake valve 9, so the lift amount L is not decreased. As compared with the case of returning to the intake cam 23 in the state, the intake rocker arm 25 and the intake valve 9 at the time of return are restored. Impact force is reduced, the valve bounce is suppressed, which improves the lift amount accuracy of the intake valve 9 by the intake cam 23.

Regarding the boundary portion Cb3 of the lift curve C, the maximum advance boundary time Iab when the closing timing Ic of the intake valve 9 is the maximum advance closing timing Iac is the maximum when the closing timing Ic is the maximum retard closing timing Irc. Due to being closer to the intake bottom dead center than the retard boundary timing Irb, when the closing timing Ic is the maximum advance closing timing Iac, the lift amount decreases in the lift amount decrease region Cb where the lift amount L of the intake valve 9 decreases. Since the boundary Cb3 that defines the end point of the small decrease area Cb1 with a small rate is at a time (or position) relatively close to the intake bottom dead center, the mirror of the late closing of the intake valve 9 with a relatively large retardation amount A cycle can be realized.
As a result, even when the closing timing Ic of the intake valve 9 is the maximum advance closing timing Iac, the thermal efficiency can be improved by the mirror cycle in which the delay amount of the slow closing of the intake valve 9 with respect to the intake bottom dead center is large. Therefore, fuel efficiency is improved.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
When the amount of retardation at the maximum retardation closing timing Irc is large, when the increase amount with respect to the geometric compression ratio of the naturally aspirated internal combustion engine is relatively small, or when a knocking sensor is provided, the internal combustion engine rotates at a low speed. When the load is high, the closing timing Ic of the intake valve 9 may be set to a predetermined closing timing Ipc. Further, the closing timing Ic of the intake valve 9 may be set to the maximum retard closing timing Irc when the internal combustion engine is at high speed and high load.
The variable valve timing device may include an electromagnetically driven valve timing control member instead of hydraulic driving.
The variable valve timing device may be a device capable of changing only the closing timing Ic of the intake valve 9 and not changing the opening timing Io or changing the intake valve opening period Ai. For example, the variable valve timing device may include a plurality of intake cams having different closing timings Ic of the intake valves 9, and the plurality of intake cams may alternatively include a mechanism for driving the intake valves 9. Further, in that case, the internal combustion engine may be provided with one cam shaft provided with an intake cam and an exhaust cam. Further, at least the closing timing Ic in the opening / closing timing I of the intake valve 9 may be changed stepwise.
The lift curve of the intake cam is the range in which the intake valve and intake cam follower do not come into contact again when a valve jump occurs in the lift amount increase region between the lift amount increase region and the lift amount decrease region. You may have the linear maximum lift area | region which continues to an increase area and the maximum lift amount is maintained for a predetermined period.
The intake camshaft may be rotationally driven by an actuator (for example, an electric motor) that operates in association with the rotational position of the crankshaft without being rotationally driven by the crankshaft.
The intake cam may be a rocking cam that reciprocates by rotating within a range of a rotation angle of 360 ° or less. The exhaust supercharger is, for example, a positive displacement compressor in addition to the exhaust turbocharger 40. In other words, any supercharger having a structure in which the exhaust energy is used for supercharging may be used.
The supercharging pressure control member may be a flow rate control valve (for example, an exhaust bypass valve) that controls the flow rate of the exhaust gas flowing into the turbine 42 instead of the variable vane 51.
In addition to the vehicle, the use target of the internal combustion engine may be a ship propulsion device such as an outboard motor having a crankshaft 5 oriented in the vertical direction, or a power generation device.
The internal combustion engine is of the spark ignition type in the above embodiment, but may be of the compression ignition type.

6 ... Combustion chamber 7 ... Intake port 9 ... Intake valve 20 ... Valve operating device 23 ... Intake cam 30 ... Valve timing control member 40 ... Exhaust turbocharger 50 ... Supercharging pressure control device 60 ... Operation control device,
M ... Variable valve timing device I ... Open / close timing Ia ... Maximum advance timing Ir ... Maximum retard timing Io, Iao, Iro ... Open timing Ic, Iac, Irc ... Close timing C ... Lift curve L ... Lift amount Lm ... Maximum lift Amount Lb ... boundary lift amount S ... virtual straight line Ipc ... predetermined closing timing Pi ... intake average pressure Pe ... exhaust average pressure

Claims (5)

An intake valve and an exhaust valve for opening and closing an intake port and an exhaust port that open to the combustion chamber, an exhaust supercharger that pressurizes intake air using exhaust gas, and a closing timing of the intake valve is a maximum advance closing timing A variable valve timing device that controls the engine according to the engine operating state between the engine and the maximum retarded closing timing, and a supercharging pressure control device that controls the supercharging pressure according to the engine operating state In internal combustion engines,
When the engine operating state is a high load, the supercharging pressure control device uses the supercharging pressure as the average pressure during exhaust in the combustion chamber during the exhaust stroke when the average pressure during intake during the intake stroke And the variable valve timing device sets the closing timing to a predetermined closing timing delayed from the maximum advance closing timing or the maximum retard closing timing. An internal combustion engine characterized by the above.   2. The internal combustion engine according to claim 1, wherein the variable valve timing device sets the closing timing to the maximum retarded closing timing when the engine operating state is a low speed rotation and high load. The variable valve timing device sets the closing timing to the maximum advance closing timing when the engine operation state is a low load,
2. The lift amount of the intake valve at the intake bottom dead center when the close timing is the maximum advance angle close timing is ½ or more of the maximum lift amount of the intake valve. Or the internal combustion engine of 2. The variable valve timing device includes an intake cam that opens and closes the intake valve and defines a lift curve of the intake valve,
The lift curve has a lift amount increasing region in which the lift amount continuously increases from a valve opening start point to the maximum lift point with respect to a maximum lift point at which the lift amount of the intake valve becomes a maximum lift amount. A lift amount decrease region in which the lift amount continuously decreases from the maximum lift point to a valve closing start point;
The lift amount decrease region has a decrease start side region located on the side where the lift amount is large with respect to a virtual straight line passing through the maximum lift point and the valve closing start point in the lift amount increase region,
The decrease start side region is divided into a small decrease region on the maximum lift point side and a large decrease region on the valve closing start point side, with a boundary portion where the distance from the virtual straight line is maximized as a boundary,
The lift amount decrease rate at the small decrease region and the boundary portion is smaller than the lift amount decrease rate at the large decrease region, and the rotation angle range of the intake cam across the small decrease region and the boundary portion is The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is larger than a rotation angle range of the intake cam in a large decrease region. The timing when the closing timing is the maximum advance closing timing is closer to the intake bottom dead center than the timing when the closing timing is the maximum retard closing timing than the timing when the closing timing is the maximum retard closing timing 5. The internal combustion engine according to claim 4, wherein

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