JPH10184404A - Device and method for controlling intake and exhaust valves for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce incurring of a pump loss without worsening of combustion during partial load, in a four-cycle gasoline engine. SOLUTION: Both an intake valve and an exhaust valve are provided with a variable valve mechanism to continuously vary and control a valve opening and closing timing together with a working angle. During idling (a) and during high speed (c), the central angle of a valve overlap is situated approximately at a top dead center but during low speed partial load (b), the closing timing of the exhaust valve is more delayed than the top dead center and at the opening timing of the intake valve, it is also more delayed tan the top dead center. At the initial stage of a suction stroke, a cylinder pressure is rendered equal to an exhaust pressure and incurring of a pump loss is reduced. Further, since residual gas does not reversely flow to an intake system, combustion is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-cycle spark ignition type internal combustion engine represented by a gasoline engine, and more particularly, to a control of intake and exhaust valves of an internal combustion engine having a variable valve mechanism for both an intake valve and an exhaust valve. The present invention relates to an apparatus and a control method.

[0002]

2. Description of the Related Art Various types of variable valve mechanisms for variably controlling the opening / closing timing of intake and exhaust valves of a four-cycle internal combustion engine have been proposed in the past, and some of them have already been put to practical use. . For example, the camshaft and the crankshaft that drives the camshaft are relatively shifted in phase relationship to change the opening / closing timing of the intake / exhaust valve in the same direction, or two cams having different cam profiles. There are practically used devices in which two rocker arms are provided, and the valve lift characteristics are switched between two types by selectively switching the rocker arm in which the intake / exhaust valve actually interlocks. Also, Japanese Patent Laid-Open No. 6-18 / 1994
No. 5321, applying the principle of a non-constant velocity shaft coupling,
There is disclosed a variable valve mechanism capable of continuously variably controlling a valve lift characteristic by rotating a cylindrical camshaft at an irregular speed.

Attempts have been made to variably control the valve overlap of the intake and exhaust valves by using such a variable valve mechanism, and to reduce the fuel consumption at the time of partial load by effectively using the so-called internal EGR (internal exhaust recirculation). Have been.

The fuel efficiency is improved by the internal EGR due to a reduction in cooling loss and a reduction in pump loss, and the combustion itself tends to be worsened by an increase in residual gas. Therefore, when the internal EGR is performed for the purpose of improving the fuel efficiency, the actual contraction ratio decreases due to the valve timing and the temperature of the residual gas decreases (substantially has the same effect as the compression ratio decreases, and the effect of reducing the pump loss also decreases. )
It is very important to avoid.

In the case of internal EGR due to valve overlap, residual gas flows backward from the openings of the intake valve and the exhaust valve at a speed close to the speed of sound due to the differential pressure between the intake system and the exhaust system.

FIG. 1 shows the backflow characteristics of the residual gas during the valve overlap period. In this figure, the characteristic (solid line) when the valve overlap (O / L) is small (20 °) is compared with the characteristic (dashed line) when the valve overlap (O / L) is large (40 °). . As shown in FIG. 2, the pressure P1 in the exhaust port 2 opened and closed by the exhaust valve 1 is set to the atmospheric pressure (1.033 kg /
a cm ^2), the negative pressure pressure P3 of -500mmHg in the intake port 4 is opened and closed by the intake valve 3 (0.35
3 kg / cm ² ). Note that the illustrated characteristics show a case where the valve overlap is set symmetrically about the exhaust top dead center as an example.

The overlap starts at the time when the intake valve 3 opens in the latter half of the exhaust stroke, and ends when the exhaust valve 1 closes at the beginning of the intake stroke. At the time of opening 3,
The pressure P2 in the combustion chamber 5 is exhaust pressure (close to atmospheric pressure at low speed), and when the intake valve 3 is opened, the pressure on the intake port 4 side of the intake valve 3 is a large negative pressure of about 500 mmHg. The gas flow in the intake valve 3 has a sonic velocity, and has a flow rate proportional to the intake valve lift. Under this condition, the opening degree of the exhaust valve 1 is sufficiently large, so that the pressure P2 in the combustion chamber 5
Keep the level of exhaust pressure. Thereafter, when the opening degree of the intake valve 3 further increases (the opening degree of the exhaust valve 1 decreases conversely), as shown in the figure, the pressure P2 in the combustion chamber 5 rapidly decreases, and the reverse flow of exhaust gas to the intake system occurs. The flow rate also rises sharply and reaches a maximum. Even at this point, the differential pressure between the intake side and the exhaust side is large (250 mm
Therefore, the gas flows backward at a speed close to the speed of sound. When the opening degree of the exhaust valve 1 decreases, the flow of the exhaust valve 1 becomes rate-determining, so that the flow rate of the residual gas flowing backward decreases rapidly, and the reverse flow ends when the exhaust valve 1 closes.

As described above, most of the total gas amount flowing to the intake system during the valve overlap period flows during the period when both the intake valve 3 and the exhaust valve 1 near the overlap center angle are lifted in a well-balanced manner. Therefore, the flow rate increases at an accelerating rate as the valve overlap amount increases.

[0009]

As described above, the internal EGR utilizing the valve overlap has an advantage that the residual gas amount can be increased even with a relatively small overlap (for example, 40 to 50 °). When the flow rate increases, the reverse flow rate increases at an accelerated rate, and therefore, the variation in the residual gas flow rate due to a slight difference in overlap is a problem. Also, since the residual gas flow rate is a function of time, fluctuations in the number of revolutions also have a significant effect. Therefore, unless the valve overlap amount is rapidly reduced, such as during rapid deceleration, there is a danger of causing a so-called engine stall. Therefore, in the case of the internal EGR control by the valve overlap, there is a problem that the control accuracy and the responsiveness of the valve timing are required to be very high. Further, since the gas flows through the minute lift portion of the intake / exhaust valve at a speed close to the speed of sound, the heat transfer coefficient is large, and the temperature of the residual gas tends to decrease.

Further, internal EG due to valve overlap
In the case of R, there is an essential problem that the pressure energy cannot be effectively recovered because the residual gas flows back to the intake side by throttling and expansion.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an internal combustion engine in which a variable valve mechanism capable of controlling the valve opening / closing timing is provided on both an intake valve side and an exhaust valve side. In the engine, when the engine is partially loaded, the closing timing of the exhaust valve is delayed from the intake top dead center, and the opening timing of the intake valve is delayed from the intake top dead center.

That is, in the intake / exhaust valve control device for an internal combustion engine according to the first aspect, the variable valve mechanism capable of continuously controlling the valve opening / closing timing and the operating angle by the control signal includes an intake valve side and an exhaust valve side. In the internal combustion engine provided in both,
When the engine is partially loaded, the closing timing of the exhaust valve is controlled to a position delayed from the intake top dead center, and the opening timing of the intake valve is controlled to a position delayed from the intake top dead center. It is characterized by.

According to the present invention, the change amount of the opening timing of the exhaust valve is set smaller than the change amount of the closing timing.

FIG. 3 is a PV diagram at the time of partial load, and shows the characteristics of the conventional device and the characteristics of the present invention in comparison. The respective valve lift characteristics are also described.

FIG. 3A shows a conventional case of a small overlap which is a standard example (the center of the overlap is the upper dead center of the exhaust gas). , But the backflow from the exhaust valve is small. Looking at the pump loss in such a setting, as a result of the residual gas in the cylinder flowing back to the intake side at the beginning of the suction stroke, a large negative pressure close to the suction negative pressure acts on the piston in most of the suction stroke, The piston will work against this. Further, more than half of the residual gas in the cylinder is throttled and expanded from the intake valve and flows out to the intake port side, and the pressure energy is not effectively utilized. Therefore, as shown by the solid line A in FIG. 3, a large pump loss occurs.

FIG. 3B shows a conventional example in which the valve overlap is enlarged in order to perform internal EGR. In particular, the central angle of the valve overlap is located near the top dead center of the suction. is there. In other words, at partial load,
By increasing the operating angle of the intake and exhaust valves or changing the phase angle, the intake valve opening timing is advanced before top dead center, and the exhaust valve closing timing is delayed after top dead center. In this case, a large amount of residual gas flows back into the intake system during the valve overlap period.
Accordingly, as indicated by the broken line B in FIG. 3, the suction negative pressure decreases as the residual gas amount increases, so that the in-cylinder pressure in the initial stage of the suction stroke decreases and the pump loss decreases. However, since a large amount of residual gas is throttled and expanded from the intake valve and flows out to the intake port side, the pressure energy is not effectively utilized.

On the other hand, in the case of the present invention shown as C,
At the time of partial load, the opening timing of the intake valve is set after the top dead center, and the closing timing of the exhaust valve is also delayed after the top dead center. Note that the change amount of the opening timing of the exhaust valve is set smaller than the change amount of the closing timing, and the operating angle of the exhaust valve is increased. In this case, the exhaust gas is re-inhaled from the exhaust valve into the cylinder at the beginning of the intake stroke.
Valve valve overlap is small, and no large amount of residual gas backflow to the intake system occurs. That is, the exhaust valve is open even after the exhaust top dead center has passed, and the intake valve has not been opened yet, so that the pressure in the cylinder becomes equal to the exhaust pressure at the beginning of the suction stroke. In this state, the piston falls while re-inhaling the high-temperature exhaust gas, so that the pump loss at this stage is small. Eventually, the intake valve opens, and a part of the residual gas in the cylinder flows back to the intake side. As a result, the same negative pressure acts on the cylinder as on the intake side, but since the piston has already descended considerably, the rate at which the negative pressure acts decreases. Further, in this case, the residual gas is only the gas remaining in the cylinder at the time when the intake valve is opened, so that the residual gas amount is significantly reduced as compared with the case B described above. Therefore, as shown by the one-dot chain line C in the figure, when the full-scale suction is started, the suction negative pressure is at a higher level than in the case of B, but since the operation time is short, the whole cycle is not performed. Can be maintained at substantially the same level as in the case of B. As described above, blow-through of the residual gas is prevented, and the temperature is kept high because the cooling of the gas is small, so that the combustion is hardly deteriorated.

According to a third aspect of the present invention, there is provided an intake / exhaust valve control device for an internal combustion engine, wherein a variable valve mechanism capable of continuously controlling a valve opening / closing timing and an operating angle by a control signal is provided on the intake valve side. In an internal combustion engine provided on the exhaust valve side, a second variable valve mechanism capable of continuously controlling the phase of the valve opening / closing timing by a control signal while the angle is kept constant, when the engine is partially loaded, It is characterized in that the valve closing timing is controlled to a position delayed from the suction top dead center, and the opening timing of the intake valve is controlled to a position delayed from the suction top dead center.

That is, the second variable valve mechanism provided on the exhaust valve side changes the valve opening / closing timing by, for example, relatively changing the phase of the camshaft and the crankshaft. In this case, at the time of partial load, both the closing timing and the opening timing of the exhaust valve are delayed while the operating angle is constant. The benefits of effective use of work will be generated, and there will be little adverse effect.

According to the present invention, the amount of change in the central angle of the valve overlap of the intake and exhaust valves is set to be larger than the amount of change in the angle of the valve overlap.

According to the fifth aspect of the invention, when the engine is partially loaded, the closing timing of the intake valve is further advanced so as to approach the compression bottom dead center.

In this way, the actual compression ratio at the time of partial load is improved, and the combustion can be further improved.

In order to realize the above-described variable control of the intake / exhaust valve opening / closing timing, the intake / exhaust valve control device for an internal combustion engine according to claim 6 continuously adjusts the valve opening / closing timing and operating angle. As a controllable variable valve mechanism, a drive shaft that rotates in synchronization with the rotation of the engine, and a cam shaft that is disposed coaxially with the drive shaft and has a cam that drives a suction valve or an exhaust valve on the outer periphery. A flange portion provided at an end of the camshaft and having an engagement groove formed in a radial direction, and a flange portion provided on the drive shaft side so as to face the one flange portion; and The other flange portion having an engaging groove formed along the direction, an annular disk disposed swingably between the two flange portions, and projecting in opposite directions on both sides of the annular disk. And each of the above flanges A pin that engages in the mating groove, and a drive mechanism that swings the annular disk according to the engine operating state, wherein the operating angle of the intake valve or the exhaust valve changes according to the position of the annular disk. Has become.

In this configuration, when the center of rotation of the annular disk is concentric with the center of the drive shaft and the camshaft, the drive shaft and the camshaft rotate at a constant speed, and the annular disk is at an eccentric position. In such a case, the two rotate unequally. Therefore, the valve lift characteristics of the intake and exhaust valves change continuously according to the position of the annular disk, and the opening / closing timing and operating angle of the intake and exhaust valves change.

[0025]

According to the present invention, when the engine is partially loaded,
Internal EGR without excessive backflow of residual gas into the intake system
And pump loss can be reduced while deterioration of combustion is minimized. Therefore, the fuel consumption can be improved by reducing the pump loss and improving the combustion. Also,
A large variation in the residual gas due to a slight difference in valve overlap does not occur, and stable characteristics can always be obtained.

Further, if the intake valve closing timing is advanced at the same time as in claim 5, the actual compression ratio can be increased, and the combustion can be further improved at the partial load.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

In the first embodiment of the present invention, a variable valve mechanism 11 capable of continuously controlling the valve opening / closing timing and the operating angle is provided on both the intake valve side and the exhaust valve side of the internal combustion engine. I have.

This variable valve mechanism 11 is disclosed in
As disclosed in Japanese Patent No. 5321 and U.S. Pat. No. 5,365,896, the cylindrical camshaft of each cylinder is rotated at a non-uniform speed by applying the principle of a non-uniform shaft coupling. The valve lift characteristic can be continuously variably controlled.

Since this mechanism itself is known, the mechanism will be briefly described with reference to FIGS.
Is the timing chain 14 from the unillustrated engine crankshaft.
A drive shaft to which rotational force is transmitted via (see FIG. 4), 22
Is a hollow cylindrical camshaft rotatably fitted on the outer periphery of the drive shaft 21. The camshaft 22 is divided for each cylinder.

The camshaft 22 is rotatably supported by a cam bearing (not shown) at the upper end of a cylinder head. A pair of cams 26 for opening the pair of intake valves 12 of each cylinder are provided on the outer periphery. Is formed. The camshaft 22 is divided into a plurality of pieces as described above, and a first flange portion 27 is provided at one of the divided ends. A sleeve 28 and an annular disk 29 are arranged between the ends of the plurality of divided camshafts 22, respectively. The first flange portion 27 is formed with an elongated engagement groove extending in the radial direction.

The sleeve 28 is fixed to the drive shaft 21. The sleeve 28 has a second flange 32 facing the first flange 27. The second flange portion 32 is also formed with an elongated engagement groove along the radial direction.

The annular disk 29 located between the flange portions 27 and 32 has a substantially donut shape, has an annular gap with the outer peripheral surface of the drive shaft 21, and has an inner peripheral surface of the disk housing 34. It is rotatably held on a surface. Further, a pair of pins 36 and 37 projecting to opposite sides are provided at opposite positions on diameter lines different from each other by 180 °, and the pins 36 and 37 are engaged with the respective engagement grooves.

The disk housing 34 has a substantially triangular shape, the circular disk 29 is held in a circular opening thereof, and the first cam fitting hole 38 and the second cam A fitting hole 39 is formed through.

The circular cam portions 41a and 43a of the first eccentric cam 41 and the second eccentric cam 43 are rotatably fitted in the first cam fitting hole 38 and the second cam fitting hole 39, respectively. I agree.

As shown in FIG. 5, the second eccentric cam 43 is composed of a cylindrical shaft portion 43b and a circular cam portion 43a which are eccentric to each other by a predetermined amount. Have been. The circular cam portion 43a is prevented from coming off by the snap ring 30. Shaft 4
3b is press-fitted and fixed to the partition wall of the frame 33 as shown in FIG.

The first eccentric cam 41 is provided with a control camshaft 42 continuous over a plurality of cylinders in the longitudinal direction of the engine.
And a plurality of circular cam portions 41a fixed to the camshaft 42 corresponding to the respective cylinders, and both are eccentric by a predetermined amount. The circular cam portion 41a of each cylinder is eccentric at a predetermined angular position of the cam shaft 42. The control cam shaft 42 is rotatably held by the frame 33 via a cam bracket 35. At one end of the control camshaft 42 located at one end of the internal combustion engine, a rotary hydraulic actuator 46 is attached as a drive mechanism. At the other end of the control camshaft 42 located at the front of the internal combustion engine, a rotary potentiometer 47 for detecting the rotational position of the control camshaft 42, that is, the phase of the circular cam portion 41a, is attached.

In the variable valve mechanism 11 described above, the first
By variably controlling the eccentric position of the annular disk 29 via the eccentric cam 41, the camshaft 22 rotates at an irregular speed, and a phase difference is generated between the camshaft 22 and the drive shaft 21 according to the amount of eccentricity. For example, as shown in FIG. 5A, when the center Y of the annular disk 29 and the center X of the drive shaft 21 match, the camshaft 22 rotates synchronously with the drive shaft 21 at a constant speed. , A valve lift characteristic along the cam profile is obtained. On the other hand, as shown in FIG. 5B, when the center Y of the annular disk 29 is eccentric to one side, a phase difference corresponding to the amount of eccentricity occurs, and the valve lift characteristic is changed in a form in which the cam profile is deformed. Is obtained. Thereby, as illustrated in FIG. 6, the valve opening / closing timing and the operating angle continuously change. FIG. 6 illustrates a characteristic in which the operating angle is reduced and a characteristic in which the operating angle is increased. However, as shown in FIG. 6, the characteristics do not always have similar shapes.

In the first embodiment, a similar variable valve mechanism is also provided on the exhaust valve side, so that the valve opening / closing timing and the operating angle of the exhaust valve are continuously changed. . In particular, in this embodiment, the exhaust valve shown in FIG.
Each part is set so that the opening timing hardly changes and only the closing timing greatly changes even if the valve operating angle increases or decreases as shown in FIG.

The hydraulic pressure supplied to the hydraulic actuator 46 is controlled via a hydraulic control valve (not shown) based on a control signal from a control unit (not shown). The control unit receives an engine speed signal indicating an engine operating condition, a load signal (for example, an intake air amount signal), a water temperature signal from a water temperature sensor for detecting, for example, a cooling water temperature, as the engine temperature, and the like. The valve lift characteristics of the intake valve 12 and the exhaust valve are variably controlled.

FIG. 7 shows an example of the valve lift characteristic in the first embodiment.
Is a characteristic at a low speed partial load, and c is a characteristic at a high speed. This FIG.
As shown in (1), when idling, the valve overlap becomes very small so as to reduce residual gas and stabilize combustion. The central angle is almost at the top dead center position. Also, at high speeds, the valve overlap increases in order to increase the efficiency of charging fresh air, but the center angle is still almost at the top dead center position.

On the other hand, at the time of low-speed partial load, which is important in terms of fuel consumption characteristics and is frequently used, the operating angle of the intake valve is greatly reduced, and the opening timing of the intake valve is greatly delayed until after the intake top dead center. In the meantime, the operating angle of the exhaust valve is increasing conversely as the exhaust valve is open, and the exhaust valve closing timing is also after the top dead center. Thus, the entire valve overlap period is after the top dead center. Accordingly, the pump loss is reduced, the increase in the amount of residual gas due to blow-by can be prevented, and the temperature is kept high by the small amount of gas cooling, thereby suppressing the deterioration of combustion. As described above, the change in the opening timing of the exhaust valve is small. Further, the closing timing of the intake valve is advanced, and the intake valve is approaching the bottom dead center. By doing so, the actual compression ratio is improved, and the combustion can be further improved.

FIGS. 8 and 9 show examples of control characteristics of the variable valve mechanism executed by the control unit. FIG. 8 shows a valve overlap determined by the exhaust valve closing timing and the intake valve opening timing. Shows the control characteristic of the central angle of
FIG. 9 shows control characteristics of the intake valve closing timing. As is clear from FIG. 8, the valve overlap center angle is set to be the slowest at the low-speed partial load representative point (40 km / h steady running or the like), that is, at the most frequently used operating condition. Further, as is apparent from FIG. 9, the closing timing of the intake valve is advanced by the characteristic along the change of the central angle of the valve overlap, and the actual compression ratio is improved. In this embodiment, the change in the operating angle of the intake valve is substantially symmetrical between the opening timing and the closing timing.

FIG. 10 is a flowchart showing a specific flow of control of the opening and closing timings of the intake valve 12 and the exhaust valve. First, in step 1, a control map of the valve overlap center angle is read. As this control map,
A map for after warm-up, which shows an example of the characteristics in FIG. 8, and a map for cold time, not shown, are set in advance. Next, in step 2, the cooling water temperature tw is compared with a predetermined reference temperature (temperature at which the warm-up is considered completed) t0.
If so, go to step 3. In step 3, the target value of the valve overlap center angle corresponding to the load and the engine speed at that time is determined using the control map for the cold state. In addition, as the characteristic for the cold state, for example, the characteristic may be fixed to approximately the top dead center (TDC). If the warm-up is completed and the cooling water temperature tw is higher than the reference temperature t0, the process proceeds to step 4. Step 4
Then, the target value of the valve overlap center angle corresponding to the load and the engine speed at that time is determined using the post-warm-up control map.

After determining the target value of the valve overlap center angle in this way, the routine proceeds to step 5, where whether or not the oil pressure in the lubrication system of the engine is equal to or higher than the reference oil pressure p0 is determined by a signal from an oil pressure sensor (not shown). Judgment based on The reference oil pressure p0 is set to a level at which the above-described variable valve mechanism can be normally controlled. When the oil pressure is equal to or lower than the reference oil pressure p0, for example, immediately after starting, the oil pressure is sufficiently increased. Wait until. If the hydraulic pressure is greater than the reference hydraulic pressure p0, the process proceeds to step 6, where the hydraulic actuator 46
Is driven along the target value of the valve overlap center angle.
In step 7, the actual rotational position of the control camshaft 42 is detected by the potentiometer 47, and the hydraulic actuator 46 is closed-loop controlled.

Next, a second embodiment of the present invention will be described. In the second embodiment, the above-described variable valve mechanism 11 shown in FIGS. 4 and 5 is used on the intake valve side. A second variable valve mechanism 61 having a constant operating angle is used on the exhaust side.

FIG. 11 is an enlarged sectional view showing a main part of the second variable valve mechanism 61. The second variable valve mechanism 61 includes an inner cylinder 62, an outer cylinder 63, and a piston. 64 and the like.

That is, the inner cylinder 62 is fixed to the front end of the camshaft 65 via the mounting bolt 66.
A cup-shaped outer cylinder 63 is fitted to the outer peripheral side of 2 so as to be relatively rotatable by a certain angle. The outer cylinder 63 is provided with a sprocket portion 63a that meshes with the timing belt.

A ring-shaped piston 64 is provided between the inner cylinder 62 and the outer cylinder 63. The piston 64 is connected to the outer peripheral surface of the inner cylinder 62 and the outer periphery of the outer cylinder 63 through a helical thread. Face and each other.

Further, the piston 64 is constantly urged forward by a return spring 67. To counter this spring force, a hydraulic chamber is provided between the front surface of the piston 64 and the back surface of the lid of the outer cylinder 63. 68 is annularly defined.
The hydraulic chamber 68 is connected to a control hydraulic circuit via an oil passage 69 in the mounting bolt 66 and an oil passage 70 passing through the camshaft 65.

That is, the hydraulic chamber 68 via the oil passage 70 and the like
When the hydraulic pressure is supplied to the inside, the piston 64 moves in the axial direction, and the movement in the axial direction is converted into the relative rotational movement between the inner cylinder 62 and the outer cylinder 63. Therefore, the phase between the camshaft 65 and the crankshaft changes by a predetermined amount. Therefore, as shown in FIG. 12, the phase of the valve lift characteristic can be continuously changed within a predetermined angle range.

FIG. 13 shows an example of a valve lift characteristic in the second embodiment in which the second variable valve mechanism 61 is used on the exhaust side. Is the characteristic at high speed. As shown in FIG. 13, at the time of idling, the exhaust valve opening / closing timing is relatively early, and the valve overlap is very small so as to reduce residual gas and stabilize combustion. The central angle is after the top dead center. At high speeds, the valve overlap increases in order to increase the efficiency of charging fresh air, but the central angle is almost at the top dead center position.

On the other hand, at the time of low-speed partial load, which is important in terms of fuel efficiency, and is frequently used, the operating angle of the intake valve is greatly reduced, and the opening timing of the intake valve is greatly delayed until after the intake top dead center. During this time, the phase of the exhaust valve is controlled to be delayed so that the exhaust valve is open, and the exhaust valve closing timing is also after the top dead center. Thus, the entire valve overlap period is after the top dead center. Therefore,
The pump loss is reduced, the increase in the residual gas amount due to blow-through is prevented, and the temperature is kept high due to less gas cooling, thereby suppressing the deterioration of combustion. Although the opening timing of the exhaust valve is delayed, the adverse effect is small in a low-speed partial load region. Further, as with the first embodiment, the closing timing of the intake valve is advanced, and the intake valve is approaching the bottom dead center.
By doing so, the actual compression ratio is improved, and the combustion can be further improved.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing characteristics of a negative pressure in a combustion chamber and a backflow of exhaust gas to an intake system during a valve overlap period.

FIG. 2 is an explanatory diagram showing a general layout of an intake / exhaust system.

FIG. 3 is a PV diagram showing a comparison between the present invention and the related art.

FIG. 4 is a perspective view showing one embodiment of a variable valve mechanism used in the present invention.

FIGS. 5A and 5B are explanatory views showing the operation of the variable valve mechanism, wherein FIG. 5A is an explanatory view showing a concentric state, and FIG. 5B is an explanatory view showing an eccentric state.

FIG. 6 is a characteristic diagram showing valve lift characteristics obtained by the variable valve mechanism.

FIG. 7 is a characteristic diagram showing valve lift characteristics of the intake and exhaust valves according to the first embodiment of the present invention.

FIG. 8 is a characteristic diagram showing control characteristics of a valve overlap center angle.

FIG. 9 is a characteristic diagram showing control characteristics of intake valve closing timing.

FIG. 10 is a flowchart showing the flow of control according to the present invention.

FIG. 11 is a sectional view showing a second variable valve mechanism used in a second embodiment of the present invention.

FIG. 12 is a characteristic diagram showing valve lift characteristics obtained by the second variable valve mechanism.

FIG. 13 is a characteristic diagram showing valve lift characteristics of an intake / exhaust valve according to a second embodiment of the present invention.

[Explanation of symbols]

 11 Variable valve mechanism 12 Intake valve 61 Second variable valve mechanism

Claims (7)

[Claims] In an internal combustion engine provided with a variable valve mechanism capable of continuously controlling a valve opening / closing timing and an operating angle by a control signal on both an intake valve side and an exhaust valve side, when the engine is partially loaded, Wherein the closing timing of the exhaust valve is controlled to a position delayed from the intake top dead center, and the opening timing of the intake valve is controlled to a position delayed from the intake top dead center. Engine intake and exhaust valve control device. 2. The intake valve control device for an internal combustion engine according to claim 1, wherein a change amount of the opening timing of the exhaust valve is set smaller than a change amount of the closing timing. 3. A variable valve mechanism capable of continuously controlling a valve opening / closing timing and an operating angle by a control signal is provided on an intake valve side, and controls a phase of the valve opening / closing timing while keeping the operating angle constant. In the internal combustion engine in which the second variable valve mechanism that can be continuously controlled by the exhaust valve is provided on the exhaust valve side, when the engine is partially loaded, the position where the closing timing of the exhaust valve is later than the intake top dead center And the opening timing of the intake valve is controlled to a position delayed from the intake top dead center. 4. The valve according to claim 1, wherein the change amount of the central angle of the valve overlap of the intake and exhaust valves is set to be larger than the change amount of the valve overlap angle. Control device for an internal combustion engine. 5. The intake and exhaust of an internal combustion engine according to claim 1, wherein the closing timing of the intake valve is further advanced so as to approach the compression bottom dead center when the engine is partially loaded. Valve control device. 6. The variable valve mechanism capable of continuously controlling the valve opening / closing timing and the operating angle is provided on a drive shaft rotating in synchronization with the rotation of the engine, and coaxially with the drive shaft. A camshaft having a cam for driving an intake valve or an exhaust valve on an outer periphery thereof; one flange provided at an end of the camshaft and having an engagement groove formed in a radial direction; The other flange portion, which is provided on the drive shaft side so as to face the flange portion and has an engagement groove formed in the radial direction, and is annularly disposed between the two flange portions so as to be swingable. A disk, pins protruding from opposite sides of the annular disk in opposite directions to engage in respective engagement grooves of the flange portions, and a drive for swinging the annular disk according to an engine operating state. The annular disk 6. The intake / exhaust valve control device for an internal combustion engine according to claim 1, wherein the operating angle of the intake valve or the exhaust valve changes according to the position of the intake valve. 7. An internal combustion engine having variable valve mechanisms capable of controlling the valve opening / closing timing provided on both an intake valve side and an exhaust valve side. A method for controlling intake and exhaust valves of an internal combustion engine, wherein the method is delayed from top dead center and the opening timing of the intake valve is delayed from intake top dead center.