JPH09317520A - Intake valve control device and method for internal combustion engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve anti-knocking characteristic in low speed and high load state, heighten the compression ratio of super charged engines, and enable retarded ignition timing for activating catalysts. SOLUTION: A super charger 11 comprising a screw type compressor is disposed on an intake path 10 and has first and second throttle valves 14 and 15 on the upstream and downstream respectively. The intake valve 3 is controlled to vary opening/closing timing through a variable active valve mechanism. In high loading state, a valve overlap is controlled to be larger, while scavenging action using super charged pressure is carried out, so that nocking due to residual gas can be restrained.

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 an intake valve control of an internal combustion engine with a supercharger equipped with a supercharger and a variable valve mechanism. The present invention relates to a device and a control method.

[0002]

2. Description of the Related Art Unlike a turbocharger driven by exhaust gas, an internal combustion engine equipped with a mechanical supercharger (so-called supercharger) driven by the output of an internal combustion engine has a sufficient supercharging pressure from a low speed. As a result, there is an advantage that a good response can be obtained. In addition, even when a highly efficient catalyst system is installed in the exhaust system due to recent demands for exhaust gas purification performance, the decrease in exhaust temperature at the catalyst inlet is less than that of the turbocharger. It is also advantageous in terms of suppression.

Further, it has been conventionally known to introduce secondary air into the upstream side of the catalytic converter in the exhaust system in order to activate the catalyst during cooling, but a pressure source for introducing the secondary air is known. Also, the use of mechanical superchargers is considered.

On the other hand, various types of variable valve mechanisms for variably controlling the opening / closing timing of intake valves of an internal combustion engine have been proposed in the past, and some of them have already been put to practical use. For example, by changing the phase relationship between a camshaft and a crankshaft that drives the camshaft relatively, the opening / closing timing of the intake valve is changed in the same direction, or two cams having different cam profiles are used. Follow 2
An apparatus has been put into practical use in which two rocker arms are provided, and the valve lift characteristics are switched between two types by selectively switching a rocker arm in which an intake valve is actually linked. In Japanese Patent Application Laid-Open No. 6-185321, the valve lift characteristics can be continuously variably controlled by rotating the cylindrical camshaft at an unequal speed by applying the principle of an unequal speed shaft coupling. A variable valve mechanism is disclosed.

[0005]

By the way, the low-load high-load range is a condition under which knocking is likely to occur, and when supercharging at a higher pressure is performed in this range, a natural air-supply engine not equipped with a supercharger is provided. It is necessary to set the compression ratio to a lower value than that of, which leads to deterioration of fuel efficiency.

Further, when the engine is cold, in order to raise the temperature of the catalyst at an early stage, it is necessary to devise to raise the temperature of the exhaust gas discharged from the engine as much as possible. A typical method is to delay the ignition timing to the limit, which delays the combustion and prolongs the combustion until the end of the expansion stroke, which raises the in-cylinder temperature when the exhaust valve opens and the catalytic converter inlet. There is a great effect in raising the exhaust temperature of the. However, in order to significantly delay the ignition timing in this way, it is essential to improve the combustion quality, and if the combustion quality is not good, misfire easily occurs when the ignition timing is retarded, and a sufficient exhaust gas temperature rise effect Can't get

As described above, in the conventional internal combustion engine with a supercharger, in order to avoid knocking at low speed, the compression ratio is set to be lower by about 1 to 1.5 than that of the natural charge engine. Is common. The deterioration tendency of fuel consumption due to this is offset by the reduction of friction loss due to the fact that the displacement of the internal combustion engine can be set smaller than that of the natural air supply engine, so that the deterioration of fuel consumption of the entire engine can be avoided. However, if the compression ratio decreases, the combustion speed becomes slower, and as described above, when the ignition timing is significantly delayed, misfire is likely to occur, making it impossible to significantly retard. Therefore, there is a disadvantage in reducing HC by increasing the exhaust temperature.

As described above, the anti-knock performance of the internal combustion engine with the supercharger, especially the anti-knock performance in the low speed range is improved,
Setting the compression ratio to a high level is very important not only from the viewpoint of fuel efficiency but also from the viewpoint of reducing HC during cooling.

An object of the present invention is to improve the knock resistance of the internal combustion engine with a supercharger in a low speed range and to set a high compression ratio. Further, it is an object of the present invention to improve combustion by using a supercharger during engine cooling to reduce HC.

[0010]

In order to achieve the above object, an intake valve control apparatus according to claim 1 and a control method according to claim 9 of the present invention have a supercharger in an intake system, In addition, in an internal combustion engine equipped with a variable valve mechanism that can continuously control the opening / closing timing of the intake valve by a control signal, the intake valve opening timing is set so that the valve overlap is small at idle and large at high load. In addition to variably controlling, the closing timing of the intake valve is variably controlled so as to be maintained near the bottom dead center at the time of idling and to be delayed from this at the time of high load.

That is, since the valve overlap becomes small when the engine is idle, deterioration of combustion due to blowback of residual gas is prevented, and the actual compression ratio rises due to the intake valve closing timing approaching bottom dead center. Stabilizes.

On the other hand, when the supercharging pressure is high and the load is high, the valve overlap becomes relatively large, so that the scavenging effect in the combustion chamber can be obtained. That is, before the intake valve opens, fresh air having a pressure level much higher than the exhaust pressure is stored in the intake port due to supercharging. On the other hand, the pressure in the combustion chamber is at the end of the exhaust stroke, and since the exhaust valve is open, the pressure becomes close to the exhaust pressure. This exhaust pressure is low when the supercharger is a mechanical supercharger, and is close to the atmospheric pressure especially in the low speed range. Therefore, when the intake valve begins to open with the exhaust valve open, fresh air flows into the combustion chamber from the intake port at a velocity close to the speed of sound, and the residual gas in the combustion chamber is pushed by this fresh air flow and exhausted. Pushed out of the port. When the exhaust valve is closed, this scavenging action ends and the intake stroke starts.

The residual gas in the combustion chamber has a temperature of 800 ° C. or higher, depending on the operating conditions, and it mixes with the intake air to raise the intake air temperature during compression, which is a major factor causing knocking. Is known to exist. Therefore, by significantly reducing the residual gas concentration in the combustion chamber at low speed and high load as described above, the antiknock performance thereof is significantly improved.

Of course, if the overlap is too large, the scavenging effect will be too large, and a large amount of fresh air will blow through to the exhaust system. Therefore, the overlap has an appropriate value. Further, as the rotation speed of the internal combustion engine becomes higher, the valve overlap time becomes shorter. Therefore, in order to obtain the same scavenging effect, it is preferable to increase the valve overlap (angle) as the rotation speed increases.

Further, since the intake valve closing timing is delayed from the bottom dead center at the time of high load, the stroke is substantially shortened, which contributes to the reduction of pump loss. And by supercharging at such a high pressure, the well-known Miller cycle effect can be obtained.

Since it is necessary to supercharge at a high pressure in order to obtain the Miller cycle effect, it is preferable to use a screw type compressor for internal compression as the supercharger. .

Since this screw type compressor is mechanically difficult to connect and disconnect with a clutch, it is usually
Although it will be driven even at partial load, in the operating characteristics of the intake valve as in the present invention, the balance is maintained by reducing the actual compression ratio on the internal combustion engine side by the amount of compression by the supercharger. If so, the compression work of the supercharger can be effectively used even at the time of partial load.

An intake valve control device according to a second aspect of the present invention has a first throttle valve upstream of the supercharger and a second throttle valve downstream of the supercharger. A secondary air passage from the supercharger to the engine exhaust system is provided, and the opening of the second throttle valve is controlled to be smaller than the opening of the first throttle valve when the engine is cold.

In this structure, the secondary air can be positively introduced into the engine exhaust system by utilizing the supercharging action of the supercharger, and the activation of the catalyst can be promoted. Then, when the engine is cold, the intake air amount of the internal combustion engine is adjusted by the second throttle valve downstream of the supercharger. At this time, the temperature of the intake air is increased by being pressurized by the supercharger, then the pressure is reduced by the expansion of the second throttle valve (the temperature does not decrease), and the intake air is introduced into the combustion chamber. That is, the temperature of the intake air introduced into the combustion chamber during engine cooling rises, which improves combustion.

In order to realize the variable control of the intake valve opening / closing timing as described above, the intake valve control device according to a fourth aspect of the present invention, the variable valve mechanism includes a drive shaft that rotates in synchronization with rotation of the engine. A cam shaft coaxially arranged with the drive shaft and having a cam for driving the intake valve on the outer periphery, and an engagement groove formed at an end of the cam shaft and extending in the radial direction. Between one flange portion, the other flange portion provided on the drive shaft side so as to face the one flange portion, and having an engaging groove formed in the radial direction, and between the both flange portions. The annular disc, which is arranged so as to be swingable, the pins protruding from opposite sides of the annular disc in opposite directions to engage with the engaging grooves of the flanges, and the annular disc Driving that swings according to operating conditions Is provided with a mechanism, the.

In this configuration, when the center of rotation of the annular disk is concentric with the centers 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 characteristic of the intake valve continuously changes according to the position of the annular disk, and the opening / closing timing and operating angle thereof change.

Next, the intake valve control apparatus and method for an internal combustion engine with a supercharger according to claims 5 and 10 are mechanical supercharges that are turned on / off in accordance with engine operating conditions via an electromagnetic clutch. In an internal combustion engine equipped with an engine in the intake system and a variable valve mechanism that can variably control the phase of the camshaft that opens and closes the intake valve with respect to the crankshaft, the valve overlap becomes small at idle and the high load The variable valve mechanism is controlled so that the valve overlap is sometimes large.

As the supercharger, for example, a volume type roots blower without internal compression is used.

In this structure, as in the above-mentioned claim 1, the deterioration of combustion due to blowback of residual gas is prevented by reducing the valve overlap at the time of idling. Also, at high load when the boost pressure becomes high,
By increasing the valve overlap, the above-mentioned scavenging effect in the combustion chamber is obtained in the same manner, and the residual gas concentration in the combustion chamber at low speed is reduced. This suppresses knocking.

Further, in the intake valve control device according to the present invention, the throttle valve is located downstream of the supercharger, and the secondary air passage extending from the throttle valve and the supercharger to the engine exhaust system is formed. Prepare,
When the engine is cold, the ON region of the supercharger is expanded and corrected to the partial load region of the engine.

In this structure, the secondary air is positively introduced into the engine exhaust system by utilizing the boost pressure by the supercharger,
The activation of the catalyst is promoted. Further, during engine cooling, the supercharger operates with the throttle valve throttled, so the temperature of the intake air introduced into the combustion chamber rises, and combustion during engine cooling is improved.

As the internal combustion engine to which the intake valve control apparatus of the present invention is applied, it is preferable that the internal combustion engine is a direct injection type engine that directly injects fuel into the cylinder. In this case, the fuel injection start timing is set during the intake stroke and after the exhaust valve is closed.

According to this structure, when the valve overlap becomes large at the time of high load and the above-mentioned scavenging action is performed, only fresh air containing no fuel flows into the combustion chamber and residual exhaust gas is discharged. To the exhaust port. for that reason,
Even if the overlap is excessively large, only air that does not contain fuel will be blown into the exhaust system, and combustion in the catalytic converter will not occur. Therefore, it is possible to set the valve overlap sufficiently large in order to enhance the scavenging efficiency.

[0029]

As is apparent from the above description, according to the intake valve control device and control method for an internal combustion engine with a supercharger according to the present invention, the supercharging pressure is utilized in the combustion chamber at low speed and high load. Scavenging can be performed, and knocking due to high temperature residual gas can be suppressed. Therefore, the compression ratio can be increased as compared with the conventional internal combustion engine with a supercharger, and for example, the ignition timing can be significantly retarded for early activation of the catalyst when the engine is cold.

According to the second or sixth aspect of the present invention, the catalyst can be activated early by positively introducing the secondary air, and the intake air introduced into the combustion chamber when the engine is cold can be heated. The temperature can be increased, and combustion can be improved when the engine is cold. As a result, the unburned HC itself generated by combustion can be reduced, and the ignition timing can be significantly retarded, so that the catalyst can be activated early.

Further, according to the third aspect, it is possible to form a Miller cycle by supercharging at a high pressure, and it is possible to improve fuel consumption in the partial load range.

Furthermore, by combining with the direct injection type internal combustion engine as claimed in claim 8, the scavenging effect at high load can be further ensured, and the knock resistance in the low speed and high load range can be obtained. It is possible to further improve.

[0033]

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

FIG. 1 shows the structure of an intake / exhaust system of an internal combustion engine with a supercharger according to the present invention. A pair of intake valves 3 and a pair of exhausts are provided for a combustion chamber 2 above each cylinder 1. Valve 5
Are arranged so that the intake valve 3 opens and closes the intake port 4, and the exhaust valve 5 opens and closes the exhaust port 6. Here, the exhaust valve 5
Is opened and closed with a fixed valve timing by an exhaust side camshaft (not shown). On the other hand, the intake valve 3 has a variable valve mechanism, which will be described later,
The opening / closing timing can be variably controlled.

The exhaust port 6 is connected to an exhaust passage 8, and a catalytic converter 7 is interposed in the exhaust passage 8.

The intake passage 10 to which the intake port 4 is connected has a collector 9 and a supercharger 11 upstream of the collector 9. The supercharger 11 is a mechanical type that is driven by an engine output, and for example, as shown in FIG.
A screw type compressor formed by meshing with each other is used. This screw type supercharger 11 is, as is well known,
Since it involves internal compression, high pressure supercharging is possible. Further, in the case of the screw type supercharger 11, since it is difficult to connect and disconnect with the electromagnetic clutch, it is normally driven by the engine output.

A first throttle valve 14 is provided upstream of the supercharger 11 in the intake passage 10, and a second throttle valve 14 is provided downstream of the supercharger 11, that is, between the collector 9 and the collector 9. 15 is interposed. These first and second throttle valves 14 and 15 are
In both cases, the opening degree is controlled by a control unit (not shown) via an actuator such as a pulse motor.
That is, the amount of depression of an accelerator pedal (not shown) is detected by an accelerator opening sensor such as a potentiometer, and based on this accelerator opening, either the first throttle valve 14 or the second throttle valve 15 will be described later. Either one will be narrowed down.

The upstream side and the downstream side of the supercharger 11 are connected to each other by a bypass passage 16 provided so as to bypass the supercharger 11. One end of the bypass passage 16 is connected between the first throttle valve 14 and the supercharger 11, and the other end is connected between the supercharger 11 and the second throttle valve 15, respectively. The bypass passage 16 is provided with a bypass control valve 17 such as a butterfly valve whose opening and closing is controlled by a control unit (not shown).

Further, a secondary air passage 18 is provided so as to introduce secondary air from the intake system of the internal combustion engine to the exhaust system. One end of the secondary air passage 18 is connected between the supercharger 11 of the intake passage 10 and the second throttle valve 15,
The other end of the exhaust passage 8 is connected to the upstream side of the catalytic converter 7. The secondary air passage 18 is provided with a solenoid valve 19 which is opened / closed depending on engine operating conditions, as will be described later.

As the internal combustion engine, an in-cylinder direct injection type internal combustion engine provided with a fuel injection valve 20 so as to directly inject fuel into the combustion chamber 2 is used. Here, the fuel injection start timing is set at the timing of the intake stroke of the engine and after the exhaust valve 5 is closed. As a result, it is possible to prevent fuel from blowing through to the exhaust system due to valve overlap.

FIG. 1 shows an operating state in the partial load region after the warm-up of the internal combustion engine is completed. Under this operating condition, as shown in the figure, the second throttle valve 15 on the downstream side of the supercharger 11 is kept fully open, and the first throttle valve 14 on the upstream side of the supercharger 11 is in accordance with the accelerator opening. It is controlled to open and close, and the amount of intake air is adjusted. The supercharger 11 is driven in synchronization with the rotation of the internal combustion engine.

Next, FIG. 2 shows a control state in full load operation after completion of warming up. In this state, the first throttle valve 14 is in a fully open state in association with the accelerator opening. In this state, the supercharger 11 performs sufficient supercharging. Further, as will be described later, a scavenging action can be obtained by increasing the valve overlap.

Next, FIG. 3 shows the control state in the partial load region when the engine is cold. In particular, the control state is shown when the temperature of the catalytic converter 7 is very low, such as immediately after the start of the internal combustion engine. During such engine cooling, the first throttle valve 14 on the upstream side of the supercharger 11 is kept in a fully open state, and the second throttle valve 15 on the downstream side of the supercharger 11 controls the opening degree according to the accelerator opening degree. To be done. Therefore, since the opening degree of the second throttle valve 15 is small, the temperature of the intake air is increased by being pressurized by the supercharger 11, and then the second intake valve
After passing through the throttle valve 15, it is introduced into the combustion chamber 2 via the collector 9. Here, in the second throttle valve 15, the pressure is reduced by the expansion of the throttle, but the temperature does not drop. Then, the surplus intake air circulates from the downstream side of the supercharger 11 to the upstream side of the supercharger 11 via the bypass passage 16, and the temperature thereof rises due to the repeated compression action. Therefore, the temperature of the intake air introduced into the combustion chamber 2 rises significantly, and combustion during engine cooling is improved. As a result, unburned HC itself generated by combustion is reduced, and it is possible to significantly retard the ignition timing for promoting catalyst activation. In this state, the temperature of the catalytic converter 7 is too low, so that the secondary air is not introduced. This is because, if secondary air is introduced at this stage, the catalytic converter 7 will be cooled conversely.

At the stage where the temperature of the catalytic converter 7 rises to some extent from the state shown in FIG. 3, as shown in FIG.
The solenoid valve 19 is opened, and the secondary air is introduced into the exhaust system via the secondary air passage 18. At this time, the opening degree of the second throttle valve 15 is smaller than the opening degree of the first throttle valve 14, so that the secondary air is sufficiently supplied by the action of the supercharger 11. The supply of the secondary air causes the temperature of the catalytic converter 7 to rise quickly.

FIG. 5 shows the first and second throttle valves 1 as described above.
4 is a flowchart showing the contents of control relating to solenoid valves 4, 15 and solenoid valve 19. That is, in step 1, operating conditions such as engine speed, engine load and catalyst temperature are read. Next, in step 2, it is determined whether or not the engine has been warmed up, that is, whether or not the catalyst temperature tc has reached a sufficiently high temperature t0. Here, if the warm-up is completed, the process proceeds to step 8 and, as described above, the second throttle valve 15
Is fully opened, and the opening degree of the first throttle valve 14 is controlled according to the accelerator opening degree. If it is determined in step 2 that the warm-up has not been completed, the process proceeds to step 3 and the first throttle valve 14
Is fully opened and the second throttle valve 15 is controlled according to the accelerator opening.

Then, in step 4, it is judged whether or not the catalyst temperature has reached the temperature t1 at which the secondary air can be introduced. When the temperature is lower than the catalyst temperature t1, the temperature of the catalytic converter 7 is lowered due to the introduction of the secondary air.
Stand by without introducing secondary air. When reaching t1, the process proceeds to step 5, the solenoid valve 19 is opened, and the introduction of the secondary air is started. At the same time, the air-fuel ratio is corrected to be richer than the theoretical air-fuel ratio, and the temperature rise of the catalytic converter 7 is promoted. Next, at step 6, it is judged whether or not the catalyst temperature has risen to a predetermined activation temperature t2.
When the temperature reaches, the operation proceeds to step 7, the electromagnetic valve 19 is closed and the secondary air introduction is stopped. At the same time, the air-fuel ratio is returned to the stoichiometric air-fuel ratio.

Next, the variable valve mechanism for opening and closing the intake valve 3 and the control contents thereof will be described.

The above-mentioned variable valve mechanism is disclosed in JP-A-6-1853.
No. 21, gazette of US Pat. No. 5,365,896, etc., the cylindrical camshaft 22 of each cylinder is rotated at a non-constant speed by applying the principle of a non-constant-speed shaft coupling. The valve lift characteristic can be continuously and variably controlled.

Since this mechanism itself is known, a brief description will be given with reference to FIGS.
Is the engine crankshaft (not shown) to the timing chain 23
The drive shaft 22 through which the rotational force is transmitted (see FIG. 7).
Is a hollow cylindrical camshaft rotatably fitted on the outer periphery of the drive shaft 21. The cam shaft 22 is divided for each cylinder.

The cam shaft 22 is rotatably supported by a cam bearing at the upper end of the cylinder head 24, and a pair of cams 26 for opening the intake valves 3 of each cylinder are formed on the outer periphery of the cam shaft 22. . Also, the camshaft 22
Is divided into a plurality of pieces as described above, and the first flange portion 27 is provided at one of the divided ends. Further, a sleeve 28 and an annular disk 29 are arranged between the ends of the camshaft 22 divided into a plurality of parts. The first flange portion 27 has an elongated engagement groove formed along the radial direction.

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

The annular disc 29 located between the flange portions 27 and 32 has a substantially donut plate shape and has an annular gap between the outer peripheral surface of the drive shaft 21 and the inner periphery of the disc housing 34. It is rotatably held on the 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 disc housing 34 has a substantially triangular shape, and the circular disc 29 is held in the circular opening of the disc housing 34, and the first cam fitting hole 38 and the second cam are respectively provided at two positions which are the tops of the triangles. The fitting hole 39 is formed so as to penetrate therethrough.

The circular cam portions 41a, 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 am fit.

As shown in FIG. 6, 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, and both are rotatably fitted and integrated. Has been done. The circular cam portion 43a is prevented from coming off by the snap ring 30. Shaft 4
As shown in FIG. 6, 3b is press-fitted and fixed to the partition wall portion of the frame 33.

The first eccentric cam 41 has a control cam shaft 42 which is 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. A rotary hydraulic actuator 46 is attached as a drive mechanism to one end of the control cam shaft 42 located at one end of the internal combustion engine. 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 above variable valve mechanism, the eccentric position of the annular disk 29 is variably controlled via the first eccentric cam 41, whereby the camshaft 22 rotates at a non-constant speed,
A phase difference occurs between the drive shaft 21 and the drive shaft 21 in accordance with the amount of eccentricity. For example, in the state where the center of the annular disk 29 and the center of the drive shaft 21 coincide with each other, the camshaft 22 rotates synchronously with the drive shaft 21 at a constant speed, so that the solid line in FIG. A valve lift characteristic is obtained. On the other hand, when the center of the annular disc 29 is eccentric to one side, a phase difference corresponding to the amount of eccentricity occurs as shown by the chain line in FIG. 8 (B), and with this, one point in FIG. 8 (A). A valve lift characteristic as shown by a chain line is obtained. That is, by controlling the amount of eccentricity, both the opening timing and the closing timing of the intake valve 3 can be continuously variably controlled.

10 and 11 show an example of the control characteristics of the variable valve mechanism described above. FIG. 10 shows the control characteristics of the intake valve opening timing, that is, the valve overlap, and FIG. 11 shows the intake valve. The control characteristic of the closing timing is shown.

As shown in these characteristic diagrams, the valve overlap is controlled to be extremely small when the engine is idle. At the same time, the closing timing of the intake valve 3 approaches the bottom dead center. Therefore, deterioration of combustion due to blowback of the residual gas is prevented, and the actual compression ratio is increased to stabilize combustion.

On the other hand, the valve overlap is largely controlled in the partial load range. As a result, the internal exhaust gas recirculation is positively performed, NOx is reduced, and
Pump loss is reduced and fuel economy is improved. Further, the closing timing of the intake valve 3 is close to the middle of the compression stroke, and the stroke is substantially shortened. This also contributes to the reduction of pump loss.

At the time of low speed and high load, the characteristic is that the intake valve closing timing approaches the middle of the compression stroke with the expansion of the valve overlap, so that the screw type supercharger 1
By supercharging at high pressure using No. 1, the well-known Miller cycle effect can be obtained, and the fuel consumption in the partial load range can be improved.

Next, at the time of high load where the supercharging pressure rises, the valve overlap is kept relatively large, and the scavenging action utilizing the supercharging pressure is obtained.

FIG. 12 is a characteristic diagram for explaining the scavenging action in this high load region. Before the intake valve 3 is opened, the intake port 4 is much higher than the exhaust pressure due to the supercharging action. The pressure level of fresh air is stored. On the other hand, the pressure in the combustion chamber 2 is at the end of the exhaust stroke and the exhaust valve 5 is open, so the exhaust pressure (pressure loss determined by the flow resistance of the catalytic converter 7, the silencer, etc.) In the case of a supercharger, it is low, and it is close to the atmospheric pressure, especially in the low speed range). When the intake valve 3 begins to open with the exhaust valve 5 open in this way,
As indicated by an arrow 3 in FIG. 3, fresh air flows into the combustion chamber 2 from the intake port 4 at a velocity close to the speed of sound, and the residual gas in the combustion chamber 2 is pushed by the flow of the fresh air to the exhaust port 6. Get kicked out. After that, when the exhaust valve 5 is closed, this scavenging action ends, and a substantial intake stroke starts. With such a scavenging action, the residual gas concentration in the combustion chamber 2 is significantly reduced in the high load range, particularly in the low speed and high load range, and knocking due to the intake air temperature is suppressed.

FIG. 14 and FIG. 15 show the scavenging action when the valve overlap is small. Even when the valve overlap is short, the scavenging air flow due to the supercharging pressure is generated. Since the flow rate is small and the period is short, the effect of reducing residual gas by scavenging can hardly be expected.

If the overlap is excessively large, fresh air will blow through to the exhaust system. However, if a direct injection type internal combustion engine for injecting fuel directly into the combustion chamber 2 is used as in this embodiment. , Fuel will not flow out to the exhaust system.

Since the anti-knock performance in the high load range of the internal combustion engine is improved in this way, it is possible to set the compression ratio to a relatively high value and improve the fuel consumption.

The control characteristics described above are in a state in which the engine has been warmed up, and when the engine is cold, the control characteristics shown in FIGS. 16 and 17 are obtained. As is clear from the comparison between FIG. 16 and FIG. 10 described above, when the engine is cold, the valve overlap is controlled to be small in the partial load range.
This reduces internal exhaust gas recirculation and stabilizes combustion. Further, along with this, the closing timing of the intake valve 3 approaches the bottom dead center (see FIG. 17), and the actual compression ratio becomes high.
This also contributes to the stabilization of combustion, as well as the reduction of residual gas by reducing the valve overlap. Therefore, the ignition timing can be significantly retarded as described above, and the catalytic converter 7 can be activated early due to the rise in the exhaust temperature.

FIG. 9 shows a flow chart for switching the above-mentioned control characteristics. In step 11, the engine speed, engine load and cooling water temperature are read. Then, in step 12, the cooling water temperature tw is compared with a predetermined temperature t0 that can be regarded as the completion of warm-up, and if it is lower than this, the process proceeds to step 13 to select the control map for cooling and the predetermined temperature t0. In the above case, the process proceeds to step 14 to select the warm-up control map. Then, in step 15, the actuator 46 is controlled according to the engine operating condition based on one of the control maps.

Next, FIGS. 19 to 31 show the second embodiment of the present invention.
Is shown.

FIG. 19 shows the construction of the intake system and the exhaust system in the second embodiment, and the parts which are not particularly different from those of the above-mentioned embodiment are designated by the same reference numerals.
In this embodiment, the supercharger 51 is provided on the upstream side of the collector 9 in the intake passage 10.
As shown in FIG. 23, a roots blower in which a pair of eyebrows type rotors 53 are housed in a casing 54 is used. As is well known, this type of supercharger 51 is a positive displacement type without internal compression and is not suitable for high pressure. Further, the supercharger 51 is interlocked with the engine crankshaft via an electromagnetic clutch 52 and is configured to stop at a predetermined low load.

In this embodiment, the throttle valve 55 is provided only on the downstream side of the supercharger 51. This throttle valve 55
Is always opened and closed according to the accelerator pedal opening, and therefore may be mechanically connected via a normal accelerator linkage. One end of the secondary air passage 18, that is, the upstream end is connected between the supercharger 51 and the throttle valve 55. Further, similar to the above-described embodiment, the bypass passage 16 that connects the downstream side and the upstream side of the supercharger 51 is provided, and in the passage, a bypass including a butterfly valve or the like whose opening and closing is controlled by the control unit. A control valve 17 is provided.

FIG. 19 shows the control state in the partial load range after the completion of warming up. In this state, the electromagnetic clutch 52 is
Is turned off, and the supercharger 51 is stopped. In this state, intake air is introduced through the bypass passage 16. Further, the secondary air passage 18 and the solenoid valve 19 are closed, so that the secondary air is not introduced.

Next, FIG. 20 shows a control state at the time of full load operation after completion of warming up. In this case, the electromagnetic clutch 52 is ON and the supercharger 51 supercharges. Further, in this state, a large valve overlap is given as will be described later, and the scavenging action utilizing the boost pressure is performed.

Next, FIG. 21 shows the control state in the partial load region when the engine is cold. In particular, this figure shows a state in which the temperature of the catalytic converter 7 is very low immediately after the start. In the case of this engine cooling, unlike after the completion of warming up (see FIG. 19), the electromagnetic clutch 52 is turned on and supercharging is performed even in the partial load region.
Therefore, the temperature of the intake air rises as it passes through the supercharger 51, and flows into the combustion chamber 2 through the throttle valve 55. Also,
Excess intake air on the upstream side of the throttle valve 55 is supplied to the bypass passage 1
Since it returns to the upstream side of the supercharger 51 via 6, the temperature rises due to the repeated pressurizing action. Therefore, the temperature of the intake air introduced into the combustion chamber 2 rises, and combustion at the time of cold engine is improved. At this stage, the electromagnetic valve 19 is closed and secondary air is not introduced in order to avoid the cooling of the catalytic converter 7 by the secondary air.

Then, when the temperature of the catalytic converter 7 rises to some extent, the solenoid valve 19 opens as shown in FIG. 22, and the introduction of secondary air is started. As a result, the temperature rise of the catalytic converter 7 is promoted.

As described above, by improving the combustion during cold,
It is possible to suppress the generation of unburned HC itself and to significantly retard the ignition timing.

FIG. 24 shows the electromagnetic clutch 52 as described above.
3 is a flowchart showing the content of control of the solenoid valve 19.

In step 1, engine operating conditions such as engine speed, engine load and catalyst temperature are read, and in step 2, the opening θT of the throttle valve 55 is compared with a predetermined opening θ0.
Here, in the high load region of θ0 or more, the process proceeds to step 4, the electromagnetic clutch 52 is turned on, and the supercharger 51 is operated.

On the other hand, if the throttle opening is in the partial load region smaller than θ0, the routine proceeds to step 3, where it is judged whether or not the engine warm-up is completed based on the catalyst temperature tc. If the warm-up is completed here, this routine is finished as it is. When the catalyst temperature is lower than t0, the process proceeds to step 4 and the supercharger 51 is operated regardless of the load.

Next, in step 5, the process waits until the temperature of the catalyst reaches a predetermined temperature t1 at which secondary air can be introduced.
When it reaches 1, the operation proceeds to step 6 and the secondary air passage 18
The solenoid valve 19 of is opened. At the same time, the air-fuel ratio is corrected to the rich side. As a result, the catalytic converter 7 quickly rises in temperature.

Then, in step 7, it is confirmed that the catalyst temperature has reached the predetermined activation temperature t2, and in step 8, the solenoid valve 19 is turned off. At the same time, the air-fuel ratio is returned to the stoichiometric air-fuel ratio.

Next, the variable valve operating mechanism of the intake valve 3 used in the second embodiment and its control will be described.

FIG. 25 is an enlarged sectional view showing a main part of the variable valve mechanism 61. The variable valve mechanism 61 is mainly composed of an inner cylinder 62, an outer cylinder 63, a piston 64 and the like. ing.

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.

Further, a ring-shaped piston 64 is provided between the inner cylinder 62 and the outer cylinder 63, and the piston 64 has a helical screw thread on the outer peripheral surface of the inner cylinder 62 and the outer periphery of the outer cylinder 63. It is in mesh with the surface.

Further, the piston 64 is constantly urged forward by a return spring 67, and in order to counteract this spring force, a hydraulic chamber is provided between the front surface of the piston 64 and the rear 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 oil pressure chamber 68 is provided 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. 26, the phase of the valve lift characteristic can be continuously changed within a predetermined angle range.

Here, the control characteristics of the variable valve mechanism are as follows.
It can be switched in two ways depending on the warm-up state of the internal combustion engine. FIG. 27 shows a flowchart for this switching. In step 11, the engine speed, engine load and cooling water temperature are read. And
In step 12, the cooling water temperature tw is compared with a predetermined temperature t0 that can be regarded as warm-up completion. In this case, the process proceeds to step 14 and the control map for warming up is selected. And step 1
In 5, the phase of the camshaft 65 is controlled according to the engine operating condition based on one of the control maps.

28 and 29 show an example of control characteristics during warm-up. FIG. 28 shows valve overlap characteristics and FIG. 29 shows intake valve closing timing characteristics. In this embodiment, as is clear from FIG.
Since the opening timing and the closing timing of the intake valve 3 change at the same time by the same amount, FIGS. 28 and 29 have a one-to-one correspondence with each other. As shown in these characteristic diagrams, when the internal combustion engine is idle, the valve overlap becomes very small as in the above-described embodiment, and deterioration of combustion due to blowback of residual gas is avoided. Further, in this embodiment, the intake valve closing timing at the time of idling is delayed from the bottom dead center,
The pump loss can be reduced by reducing the effective stroke.

Further, in the partial load range, the valve overlap becomes large, and NOx can be reduced by the internal exhaust gas recirculation. In addition, pump loss is reduced and fuel economy is improved.
At the same time, the intake valve closing timing approaches the bottom dead center, the actual compression ratio is improved, and the combustion is stabilized.

Then, at the time of high load where the boost pressure increases,
The valve overlap is kept relatively large, and the scavenging action using the boost pressure is performed as in the above-described embodiment.
Note that this scavenging action is based on the action exactly the same as that shown in FIGS. 12 and 13, and the description thereof will be omitted to avoid duplication.

Also in this embodiment, the in-cylinder direct injection type internal combustion engine is used as the internal combustion engine, and the blow-through of the fuel due to the valve overlap is surely prevented.

Next, FIGS. 30 and 31 show the intake valve control characteristics when the engine is cold. As is clear from the comparison between FIG. 30 and FIG. 28, when the engine is cold, the valve overlap is controlled to be extremely small, especially in the partial load range. This suppresses internal exhaust gas recirculation,
Combustion is stabilized when the engine is cold. As a result, the ignition timing can be significantly retarded as described above, and the catalytic converter 7 can be activated early.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view showing a configuration of an intake system and an exhaust system in a first embodiment of the present invention and showing a control state in a partial load range after completion of warm-up.

FIG. 2 is a configuration explanatory view showing a control state in full load operation after completion of warm-up.

FIG. 3 is a structural explanatory view showing a control state in a partial load region during engine cooling and when the catalyst temperature is low.

FIG. 4 is a structural explanatory view showing a control state of a partial load region during cooling when the catalyst temperature reaches a temperature at which secondary air can be introduced.

FIG. 5 is a flowchart showing control of first and second throttle valves and a solenoid valve.

FIG. 6 is a cross-sectional view showing a variable valve mechanism of this embodiment.

FIG. 7 is a perspective view showing a configuration of a variable valve mechanism similarly.

FIG. 8 is a characteristic diagram showing a characteristic of a rotational phase difference between a drive shaft and a cam shaft and a valve lift characteristic in this variable valve mechanism in comparison.

FIG. 9 is a flowchart showing a control characteristic switching process of the variable valve mechanism.

FIG. 10 is a characteristic diagram showing control characteristics of valve overlap during warm-up.

FIG. 11 is a characteristic diagram showing control characteristics of intake valve closing timing during warm-up.

FIG. 12 is a characteristic diagram showing a relationship between a valve overlap characteristic and a pressure when the load is high.

FIG. 13 is an explanatory diagram showing a scavenging action during a valve overlap period.

FIG. 14 is a characteristic diagram showing changes in pressure and the like when the valve overlap is small.

FIG. 15 is an explanatory diagram showing a scavenging action when the valve overlap is small.

FIG. 16 is a characteristic diagram showing control characteristics of valve overlap during cold cooling.

FIG. 17 is a characteristic diagram showing the control characteristic of the intake valve closing timing when the engine is cold.

FIG. 18 is a perspective view showing a main part of a screw type compressor.

FIG. 19 is a structural explanatory view showing a control state in a partial load region after completion of warming up, showing a second embodiment of the present invention.

FIG. 20 is a structural explanatory view showing a control state in full load operation after completion of warming up.

FIG. 21 is a structural explanatory view showing a control state at the time of partial load operation during cooling and when the catalyst temperature is low.

FIG. 22 is a configuration explanatory diagram showing a control state when the catalyst temperature reaches a temperature at which secondary air can be introduced during partial load operation during cooling.

FIG. 23 is a sectional view showing the structure of a roots blower.

FIG. 24 is a flowchart showing the content of control of the electromagnetic clutch and the electromagnetic valve of this embodiment.

FIG. 25 is a sectional view showing the structure of a variable valve mechanism according to this embodiment.

FIG. 26 is a characteristic diagram showing a valve lift characteristic of this variable valve mechanism.

FIG. 27 is a flowchart showing a control characteristic switching process of the variable valve mechanism.

FIG. 28 is a characteristic diagram showing control characteristics of valve overlap during warm-up.

FIG. 29 is a characteristic diagram showing the control characteristics of the intake valve closing timing during warm-up.

FIG. 30 is a characteristic diagram showing control characteristics of valve overlap during cold cooling.

FIG. 31 is a characteristic diagram showing control characteristics at the time of closing the intake valve when the engine is cold.

[Explanation of symbols]

 2 ... Combustion chamber 3 ... Intake valve 5 ... Exhaust valve 7 ... Catalytic converter 11 ... Supercharger 14 ... First throttle valve 15 ... Second throttle valve 18 ... Secondary air passage 19 ... Electromagnetic valve 20 ... Fuel injection valve 51 ... Supercharger 52 ... Electromagnetic clutch 55 ... Throttle valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02B 23/10 F02B 23/10 D 29/08 29/08 A 33/36 33/36 33/38 33/38 F02D 9/02 305 F02D 9/02 305B 305M 361 361H 13/02 13/02 B H J 23/00 23/00 K

Claims (10)

[Claims] 1. In an internal combustion engine having a supercharger in the intake system and a variable valve mechanism capable of continuously controlling the opening / closing timing of an intake valve by a control signal, the valve overlap becomes small at idle. , The intake valve opening timing is variably controlled so that it becomes large at high load, and the intake valve closing timing is
An intake valve control device for an internal combustion engine with a supercharger, which is variably controlled so as to be kept near a bottom dead center at the time of idling and to be delayed from this at a high load. 2. An engine exhaust system having a first throttle valve upstream of the supercharger and a second throttle valve downstream of the supercharger, and between the second throttle valve and the supercharger. 2. The internal combustion engine with a supercharger according to claim 1, further comprising: a secondary air passage leading to the second throttle valve, the opening of the second throttle valve being controlled to be smaller than the opening of the first throttle valve when the engine is cold. Intake valve control device. 3. The intake valve control apparatus for an internal combustion engine with a supercharger according to claim 1, wherein a screw type compressor is used as the supercharger. 4. The variable valve mechanism comprises: a drive shaft that rotates in synchronization with the rotation of the engine; and a cam shaft that is arranged coaxially with the drive shaft and has a cam that drives an intake valve on the outer circumference. , One flange portion provided at an end portion of the camshaft and having an engagement groove formed in the radial direction,
It is swingably disposed between the other flange portion and the other flange portion provided on the drive shaft side so as to face the one flange portion and having an engaging groove formed in the radial direction. The annular disc, the pins protruding from opposite sides of the annular disc in opposite directions to engage with the engaging grooves of the flanges, respectively, and the annular disc rocks depending on the engine operating condition. 4. A drive mechanism for moving the intake valve, wherein the opening / closing timing and the operating angle of the intake valve are changed according to the position of the annular disk.
An intake valve control device for an internal combustion engine with a supercharger according to any one of the above. 5. An intake system is provided with a mechanical supercharger that is turned on / off according to engine operating conditions via an electromagnetic clutch,
In addition, in an internal combustion engine equipped with a variable valve mechanism that can variably control the phase of the camshaft that opens and closes the intake valve with respect to the crankshaft with a control signal, the valve overlap is small at idle and large at high load. An intake valve control device for an internal combustion engine with a supercharger, which controls the variable valve mechanism as described above. 6. A throttle valve is located downstream of the supercharger, and a secondary air passage is provided between the throttle valve and the supercharger to reach the engine exhaust system. The intake valve control device for an internal combustion engine with a supercharger according to claim 5, wherein the ON region is expanded and corrected to a partial load region of the engine. 7. The intake valve control device for an internal combustion engine with a supercharger according to claim 5, wherein a roots blower is used as the supercharger. 8. An in-cylinder direct injection type engine that directly injects fuel into a cylinder is used as the internal combustion engine, and the fuel injection start timing is set during the intake stroke and after the exhaust valve is closed. An intake valve control device for an internal combustion engine with a supercharger according to any one of claims 1 to 7. 9. An internal combustion engine having a supercharger in the intake system and a variable valve mechanism capable of continuously controlling the opening / closing timing of an intake valve by a control signal in an internal combustion engine having a small valve overlap at idle. , The intake valve opening timing is variably controlled so that it becomes large at high load, and the intake valve closing timing is
An intake valve control method for an internal combustion engine with a supercharger, characterized in that variable control is performed such that it is maintained near a bottom dead center during idling, and delayed at a high load. 10. A mechanical supercharger, which is turned on / off according to engine operating conditions via an electromagnetic clutch, is provided in an intake system, and a phase of a camshaft for opening / closing an intake valve with respect to a crankshaft is changed by a control signal. In an internal combustion engine equipped with a controllable variable valve mechanism, the variable valve mechanism is controlled so that the valve overlap is small at idle and large at high load. An intake valve control method for an internal combustion engine with a feeder.