JPH06330776A - Intake device for engine with mechanical supercharger - Google Patents

Abstract

PURPOSE:To provide a intake device for engine equipped with a mechanical supercharger capable of increasing engine output and emission performance while preventing generation of knocking over the entire operation range. CONSTITUTION:In an engine VE, intake valves 1a, 1b are closed by a control unit 10 in a low speed range at 60 degrees after the bottom dead point and intake valve delay close operation is carried out while supercharge pressure is set high relatively, whereby knocking is prevented from generating and engine output and emission performance are increased. In the middle speed range where knocking is hard to occur the valves 1a, 1b are closed at 30 degrees after the bottom dead point and intake valve early closing operation is carried out while supercharge pressure is set low relatively and engine output is increased sufficiently. In a high speed range intake valve delay close operation is carried out again and engine output is increased remarkably while knocking is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an engine with a mechanical supercharger, which is equipped with a variable intake valve opening / closing timing.

[0002]

2. Description of the Related Art An engine with a mechanical supercharger has been conventionally known, which is designed to pressurize (supercharge) intake air with a mechanical supercharger to improve intake charging efficiency and output. . However, when supercharging is performed by the mechanical supercharger in this way, low speed
There is a problem that knocking tends to occur when the load is high. For this reason, in such a conventional engine with a mechanical supercharger, there is a countermeasure such as retarding the ignition timing at low speed and high load to prevent knocking from occurring. As a result, there is a problem that the output improvement effect due to supercharging is diminished and the fuel efficiency is deteriorated.

Therefore, in an engine equipped with a mechanical supercharger and an intake valve opening / closing timing varying means capable of changing the closing timing of the intake valve, the boost pressure is increased in the low speed region (low rotation region). While the intake valve closing timing is set at a relatively late time after bottom dead center in terms of crank angle, the intake valve delayed closing operation is performed to prevent the occurrence of knocking. JP-A-6
3-23912). That is, when the intake valve retarded closing operation is performed while the supercharging pressure is increased, the effective compression ratio in the compression stroke becomes smaller than in the normal operation, so the temperature rise due to the compression of the air-fuel mixture in the combustion chamber becomes small, and therefore during ignition. Therefore, the temperature of the air-fuel mixture in the engine is relatively low, and knocking is prevented from occurring. In this case, since the supercharging pressure is increased, the intake charging efficiency is almost the same as that during normal operation. Incidentally, in the conventional engine with a mechanical supercharger that performs the intake valve late closing operation in the low speed region as described above, the intake charging efficiency is improved in the operating region (medium speed region, high speed region) other than the low speed region. In order to ensure this, the closing timing of the intake valve is set in the same manner as the closing timing of a normal engine.

[0004]

However, a conventional engine with a mechanical supercharger, such as disclosed in Japanese Patent Laid-Open No. 63-239312, is designed to perform the intake valve retarded closing operation in a low speed region. In the low speed region, the supercharging pressure is set to be high, so that the air-fuel mixture flowing from the intake port into the combustion chamber flows out to the exhaust port, that is, the so-called air-fuel mixture blows through, and the HC emission amount increases to improve the emission performance. There is a problem of getting worse.

Further, in the high speed range, the engine temperature rises, so that the temperature of the air-fuel mixture in the intake passage or the combustion chamber rises, which lowers the intake charge efficiency and causes knocking.
The present invention has been made in order to solve the above-mentioned conventional problems, and is a mechanical type that can increase engine output while preventing occurrence of knocking in all operating regions, and can improve emission performance. An object of the present invention is to provide an intake device for an engine with a supercharger.

[0006]

In order to achieve the above object, a first aspect of the present invention is to provide a mechanical supercharger, at least an intake valve opening / closing timing varying means capable of changing a closing timing of an intake valve, and at least In the operating region where supercharging is performed by the mechanical supercharger, the intake valve has (expansion ratio / effective compression ratio)>
An intake valve opening / closing timing control in an intake device for a mechanical turbocharged engine, which is provided with an intake valve opening / closing timing control means for controlling the intake valve opening / closing timing varying means so as to be closed after bottom dead center so as to be 1. In the low speed region and the high speed region, the means controls the intake valve opening / closing timing variable means so that the intake valve is closed at a relatively late timing after bottom dead center when viewed from the crank angle, thereby causing the engine to perform the intake valve delayed closing operation. On the other hand, in the medium speed range, the intake valve opening / closing timing varying means is controlled so that the intake valve is closed earlier than in the intake valve late closing operation so that the engine performs the intake valve early closing operation. An intake system for an engine with a mechanical supercharger is provided. Note that the intake valve early closing operation means that the intake valve closing timing is earlier than in the intake valve late closing operation, and is earlier than the intake valve closing timing of a normal engine. It's not the point.

According to a second aspect of the present invention, in the intake system for an engine with a mechanical supercharger according to the first aspect, the intake valve opening / closing timing control means determines the closing timing of the intake valve in the low speed region and the high speed in terms of the crank angle. Provided is an intake device for an engine with a mechanical supercharger, which is set at different times depending on the region.

According to a third aspect of the present invention, in the intake system for an engine with a mechanical supercharger according to the first or second aspect, the valve train of the engine has a valve opening period of the intake valve and an exhaust valve when viewed from the crank angle. An intake device for a mechanical supercharged engine is provided, in which the overlap with the valve opening period of is reduced in a low speed region and increased in a medium speed region.

According to a fourth aspect of the invention, in the intake system for an engine with a mechanical supercharger according to any one of the first to third aspects, the intake valve opening / closing timing control means controls the intake valve delay in a high speed range. An intake device for an engine with a mechanical supercharger, which is characterized in that the intake valve closing timing in the closed operation is set at the time when the intake charging efficiency at the rated rotation is maximized by looking at the crank angle. To do.

In a fifth aspect of the present invention, in the intake system for an engine with a mechanical supercharger according to any one of the first to third aspects, the intake valve opening / closing timing control means controls the intake valve closing in the high speed region. Provided is an intake device for an engine with a mechanical supercharger, wherein the timing is changed linearly with a predetermined characteristic according to the engine speed.

[0011]

EXAMPLES Examples of the present invention will be specifically described below.
As shown in FIGS. 1 and 2, first to sixth cylinders # 1 to # 6
In the 6-cylinder V-type engine VE having the above, the first, third, and fifth cylinders # 1, # 3, and # 5 are arranged on the first bank P side, and the second and fourth cylinders on the second bank Q side. , 6th cylinder # 2, # 4, #
6 are arranged. Here, each cylinder # 1 to # 6 is
Ignition is performed in the order of 1 → # 2 → # 3 → # 4 → # 5 → # 6. Therefore, the intake strokes of the cylinders # 1, # 3, and # 5 on the first bank P side do not overlap with each other, and
The intake strokes of the cylinders # 2, # 4, and # 6 on the bank Q side do not overlap with each other. In the following description, for the sake of convenience, in the vicinity of the engine body, the fifth cylinder # 5 side is referred to as “left” and the first cylinder # 1 side is referred to as “right” when viewed in the longitudinal direction of the engine VE (left and right direction in FIG. 1). I will decide.

In each of the cylinders # 1 to # 6, when the first and second intake valves 1a and 1b are opened, an air-fuel mixture is introduced into the combustion chamber 3 from the first and second intake ports 2a and 2b. The mixture is taken in, compressed by a piston (not shown), ignited and burned by a spark plug (not shown), and an exhaust valve (not shown).
Combustion gas (exhaust gas) is discharged to the exhaust port 4 when is opened. Here, first and second fuel injection valves 5a, 5b are provided facing the first and second intake ports 2a, 2b, respectively, to inject fuel into intake air in the ports to form a mixture. There is. In addition, the third to sixth in FIG.
The cylinders # 3 to # 6 have the same configuration as the first and second cylinders # 1 and # 2, and therefore, the numbering to the individual members is omitted for the sake of space.

In each of the first and second banks P and Q, the first and second intake valves 1a and 1b of the cylinders # 1 to # 6 are also provided.
The first and second intake valve cams 6a and 6b mounted on the intake valve camshaft 7 are opened and closed at predetermined timings as will be described later.
Here, camshaft pulleys 8 are attached to the left end portions of the intake valve camshafts 7 of the first and second banks P and Q, respectively. Although not shown, one timing belt is wound around both camshaft pulleys 8 and 8 and the crankshaft pulley attached to the crankshaft, so that both intake valve camshafts 7 and 7 are The crankshaft is rotationally driven in synchronization with the crankshaft. Here, both intake valve camshafts 7,
7, the rotation phase of each of them is changed, and the first and second rotation phases are changed.
An intake valve opening / closing timing changing means 9 capable of changing the opening / closing timing of the intake valves 1a, 1b is provided, and these intake valve opening / closing timing changing means 9 are controlled by the control unit 10, respectively.
In addition, the intake valve opening / closing timing changing means 9 includes the first and second
Since the opening / closing timing of the intake valves 1a, 1b is only shifted in the advance direction or the retard direction, the valve opening period (seen in crank angle) does not change even when the opening / closing timing is changed.

Although not shown, the exhaust valve is also the intake valve 1.
The mechanism is similar to a and 1b, and is opened and closed at a predetermined timing as described later. However, since the opening / closing timing variable means is not provided for the exhaust valve, the opening / closing timing of the exhaust valve is fixed.

A common intake passage 12 is provided for supplying air for fuel combustion to each of the cylinders # 1 to # 6 of the engine VE. The common intake passage 12 is arranged in this order from the upstream side in the flow direction of the intake air. , An air cleaner 13 for removing dust in intake air, an air flow sensor 14 for detecting the amount of intake air, a throttle valve 15 which is opened and closed in conjunction with an accelerator pedal (not shown), and a crankshaft (not shown) Driven by a mechanical supercharger 16 (supercharger)
And an intercooler 17 that cools the intake air that has been adiabatically compressed by the mechanical supercharger 16 and whose temperature has risen. Here, a bypass intake passage 18 is provided downstream of the throttle valve 15 to connect a portion of the common intake passage 12 upstream of the mechanical supercharger 16 and a portion downstream of the intercooler 17 to each other. A relief valve 20 that is opened and closed by an actuator 19 is provided in the intake passage 18. When the discharge pressure of the mechanical supercharger 16, that is, the supercharging pressure approaches the set value (limit supercharging pressure), the relief valve 20 is opened by the actuator 19 and the intake air downstream of the intercooler returns to the upstream of the supercharger. Thus, the supercharging pressure is maintained below the set value (limit supercharging pressure). In this way, the reason why the supercharging pressure is kept below the limit supercharging pressure is that when the supercharging pressure exceeds the limit supercharging pressure, the mechanical supercharger 16 becomes hot and its reliability deteriorates.

The common intake passage 12 has a first branch intake passage 21 and a second branch intake passage 2 downstream of the intercooler 17.
2, the downstream end of the first branch intake passage 21 is connected to the first surge tank 23 for the first bank P, and the downstream end of the second branch intake passage 22 is the second surge for the second bank Q. It is connected to the tank 24. Here, a first communication passage 25 that connects the left end portion of the first surge tank 23 and the left end portion of the second surge tank 24 is provided.
A communication passage opening / closing valve 26 that opens and closes the valve is provided in this. In addition, a second communication passage 27 that connects the right end of the first surge tank 23 and the right end of the second surge tank 24 is provided, and the second communication passage 27 has two communication passage shutter valves that open and close the second communication passage 27. 28a and 28b are interposed.

The first and second communication passages 25 and 27, the communication passage opening / closing valve 26, and the communication passage shutter valves 28a and 28b effectively utilize the resonance effect or the inertial effect in accordance with the engine speed, and thereby the intake air intake. It is provided to increase the filling efficiency. That is, when the engine speed is low, the communication passage opening / closing valve 26 and the communication passage shutter valves 28a and 28b are closed to close the common intake passage 12
From the first to the second branch intake passages 21 and 22 by using the resonance effect of the pressure wave reversal portion to improve the intake charging efficiency, and open only the communication passage shutter valves 28a and 28b during the middle rotation. 2 The intake filling efficiency is increased by utilizing the resonance effect in which the central portion of the communication passage 27 is used as the pressure wave reversal portion, and the communication passage opening / closing valve 26 and the communication passage shutter valves 28a, 28b are opened at the time of high rotation to utilize the inertial effect. The intake charging efficiency is improved.

The first surge tank 23 has a first,
The upstream ends of three sets of first and second independent intake passages 29a and 29b for the third and fifth cylinders # 1, # 3 and # 5 are connected to each other, and the first and second independent intake passages 29a and 29b are connected. The downstream ends of the cylinders are connected to the first and second intake ports 2a and 2b of the corresponding cylinders. On the other hand, the second surge tank 24 has three sets of first and second independent intake passages 2 for the second, fourth, and sixth cylinders # 2, # 4, and # 6.
The upstream ends of 9a and 29b are connected, and the downstream ends of these first and second independent intake passages 29a and 29b are connected to the first and second intake ports 2a and 2b of the corresponding cylinders, respectively. here,
In the second independent intake passage 29b of each cylinder # 1 to # 6,
An intake passage opening / closing valve 30 is provided which is closed when the load is low and generates swirl in the combustion chamber 3 to enhance the combustibility of the air-fuel mixture. The first intake port 2a is a tangential type or helical type swirl port.

The first and second fuel injection valves 5a and 5b of each cylinder # 1 to # 6 are provided with an assist air supply passage 31 for supplying assist air for promoting vaporization and atomization of fuel. The upstream end of the assist air supply passage 31 opens into the common intake passage 12 on the upstream side of the throttle valve 15. An assist air control valve 32, which is a three-way valve, is provided in the assist air supply passage 31, and the third terminal of the assist air control valve 32 has an upstream end located downstream of the mechanical supercharger 16. An assist air introduction passage 33 opening to the common intake passage 12 is connected. Here, the assist air control valve 32
When supercharging, the pressurized intake air is introduced as assist air through the assist air introduction passage 33, while when not supercharging, intake air at atmospheric pressure is introduced as assist air through the assist air supply passage 31. ing.

The assist air supply passage 31 branches into first and second branch assist air supply passages 31a and 31b on the way, and each fuel injection valve 5a on the first bank P side passes through the first branch assist air passage 31a. While the assist air is supplied to 5b, the assist air is supplied to each fuel injection valve 5a, 5b on the second bank Q side through the second branch assist air supply passage 31b. The first and second
Check valves 34 and 35 are provided in the branch assist air supply passages 31a and 31b, respectively.

The exhaust gas discharged from the combustion chamber 3 of each cylinder # 1 to # 6 to the exhaust port 4 is discharged to the atmosphere through the exhaust passage 36. The exhaust passage 3
A catalytic converter 37 for purifying the exhaust gas is provided at 6.

In order to reduce the amount of NOx produced, or to reduce pumping loss at low load, the exhaust gas in the exhaust passage 36 upstream of the catalytic converter 37 is used as EGR from the intercooler 17 during non-supercharging. A first EGR passage 38 that recirculates to the common intake passage 12 on the downstream side is provided, and the first EGR passage 38 has an EGR passage 38.
A first EGR valve 39 for adjusting the amount is provided. Further, during supercharging, the exhaust gas in the exhaust passage 36 downstream of the catalytic converter 37 is recirculated to the common intake passage 12 upstream of the mechanical supercharger 16 as EGR.
An EGR passage 41 is provided, and a second EGR valve 42 for adjusting the EGR amount is interposed in the second EGR passage 41.

The control unit 10 is a comprehensive control device for the engine VE including the "intake valve opening / closing timing control means" described in the claims, and the intake air amount detected by the air flow sensor 14, 1 intake air temperature detected by intake air temperature sensor 45, throttle opening detected by throttle sensor 46, intake air temperature downstream of supercharger detected by second intake air temperature sensor 47, third and fourth intake air temperature Various types of control of the engine VE are performed using control information such as intake air temperature downstream of the intercooler detected by the sensors 48 and 49, engine speed detected by a speed sensor (not shown), and the like.

However, the control unit 10
The general engine control according to the present invention is performed by a well-known ordinary control method, and since it is not the subject matter of the present invention, the description thereof will be omitted. The following will relate to the subject matter of the present invention with reference to FIG. Only the intake valve opening / closing timing control or the supercharging pressure control will be described. That is, in the engine VE, the control unit 10 controls the opening / closing timing of the intake valves 1a, 1b and the overlap between the opening period of the intake valves 1a, 1b and the opening period of the exhaust valve according to the engine speed. By controlling the period (hereinafter, referred to as valve opening overlap) and the supercharging pressure, engine output and emission performance are improved while preventing knocking in all operating regions.

In FIG. 3, G ₁ shows the characteristic of the HC emission amount (scavenging efficiency) with respect to the engine speed when such control is performed. G ₂ indicates the amount of HC discharged when the intake valve early closing operation is performed, that is, when the valve opening overlap is increased, and G ₃ is when the intake valve late closing operation is performed, that is, the valve opening overlap is decreased. HC in the case
Shows the amount of emissions. G ₄ shows the characteristic of the boost pressure with respect to the engine speed when such control is performed.
Note that G ₅ shows the supercharging pressure when the intake valve late closing operation is performed, and G ₆ shows the supercharging pressure when the intake valve early closing operation is performed. Further, G ₇ indicates the intake valve closing timing (crank angle after bottom dead center) at which the intake charging efficiency ηc becomes the best.

(1) Low Speed Region As shown in FIG. 3, in the low speed region where the engine speed is equal to or lower than the predetermined value N ₁ , the intake valves 1a and 1b are set so that (expansion ratio / effective compression ratio)> 1. Further, when viewed from the crank angle, it is closed at a relatively late timing after the bottom dead center, for example, at 60 ° after the bottom dead center, and the intake valve delayed closing operation is performed, while the supercharging pressure is set relatively high. In this case, the intake valves 1a and 1b are opened at a timing slightly earlier than the top dead center, for example, 5 ° before the top dead center. The supercharging pressure is controlled by adjusting the opening of the relief valve 20 via the actuator 19.

On the other hand, the exhaust valve is opened and closed at the same timing as in a conventional ordinary engine, for example, it is opened at 50 ° before bottom dead center and closed at 15 ° after top dead center. Therefore, in this case, the valve opening overlap becomes relatively small,
The crank angle is 20 ° (5 ° before top dead center to 15 ° after top dead center).

In this way, the intake valve retarded closing operation is performed in the low speed region, and therefore the effective compression ratio of the air-fuel mixture in the combustion chamber 3 becomes small, so that the temperature rise due to the compression of the air-fuel mixture becomes small. Therefore, the temperature of the air-fuel mixture at the time of ignition becomes relatively low, and the knocking resistance is improved. In this way, the occurrence of knocking is effectively prevented even at low speeds and high loads where knocking tends to occur. In this case, it seems that the intake charging efficiency decreases as the effective compression ratio decreases, but since the supercharging pressure is set to a high value as described above, the intake valve does not have a normal timing in the conventional engine. Almost the same intake charging efficiency as when opened and closed is secured, and a sufficient engine output is secured. Further, since the intake valve retarded closing operation reduces pumping loss, fuel efficiency is improved.

As described above, since the valve opening overlap is relatively small (for example, the crank angle is 20 °), the intake ports 2a and 2b are set even though the boost pressure is set high. The air-fuel mixture that has flowed into the combustion chamber 3 from the outflow to the exhaust port 4, that is, the air-fuel mixture does not blow through, and the HC concentration in the exhaust gas is reduced, and the emission performance is enhanced. In this case, since the supercharging pressure is set high, the scavenging inside the combustion chamber 3 is sufficiently performed.

(2) Medium speed region The engine speed exceeds the predetermined value N ₁ and the predetermined value N ₂
In the following middle speed range, the intake valves 1a, 1b are closed earlier than in the case of the intake valve late closing operation in the above low speed area, for example, at 30 ° after bottom dead center, and the intake valve early closing operation is performed. Meanwhile, the boost pressure is set to be relatively low. In this case, the intake valves 1a and 1b are opened at a timing much earlier than the top dead center, for example, 35 ° before the top dead center. The term "intake valve early closing operation" as used herein means that the intake valves 1a, 1
It does not mean that the intake valve is closed at an earlier timing than the conventional ordinary engine. Incidentally, in the present embodiment, the intake valves 1a and 1b are closed after the bottom dead center so that (expansion ratio / effective compression ratio)> 1 even in the medium speed range.

On the other hand, since the opening / closing timing of the exhaust valve is fixed (the valve is opened at 50 ° before bottom dead center and 15 minutes after top dead center).
The valve overlap is relatively large in this case, and the crank angle is 50 ° (35 ° before top dead center ~
It becomes 15 ° after top dead center.

As is clear from FIG. 3 (G ₇ ), the medium speed range
In (N _{1 to} N ₂ ), the intake valve closing timing at which the intake charging efficiency is the best is considerably smaller than 60 °. Therefore, in order to increase the intake charging efficiency in this medium speed range,
The intake valve closing timing may be made earlier than in the case of the intake valve late closing operation in the low speed region, or the boost pressure may be increased. However, the supercharging pressure when the engine speed as is clear from FIG. 3 rises to N ₁ is a limit supercharging pressure P ₁
, It is difficult to significantly increase the intake charging efficiency by increasing the supercharging pressure. Therefore, in the medium speed range, the closing timing of the intake valves 1a and 1b is advanced as compared with the case of the late intake valve closing operation in the low speed range to improve intake charging efficiency and increase engine output.

Since knocking does not occur easily in the medium speed range, knocking does not occur even when the intake valve early closing operation is performed in this way. Also, as mentioned above,
Although the valve opening overlap is relatively large (crank angle is 50 °), the valve opening overlap is relatively short in time (not the crank angle) in such a medium speed range, and the supercharging is high. Since the pressure is set to be relatively low, the mixture does not blow through, the HC concentration in the exhaust gas is reduced, and the emission performance is enhanced. Therefore, engine output and emission performance can be improved while preventing knocking even in the medium speed range. Also,
Since the boost pressure is set low, the shaft power loss of the engine is reduced and the wheel drive torque of the engine VE is increased. In this case, since the valve opening overlap is set relatively large, the scavenging inside the combustion chamber 3 is sufficiently performed.

(3) High speed region In the high speed region where the engine speed exceeds the above predetermined value N ₂ , the intake valve late closing operation is performed in the same manner as the intake valve late closing operation in the low speed region (for example, the intake valve 1a and 1b are closed at 60 ° after bottom dead center). In this case, the supercharging pressure has already reached the limit supercharging pressure P ₁ when the engine speed reaches N _2.
Therefore, the boost pressure is maintained at a constant value P ₁ .

The reason why the intake valve retarded closing operation is performed again in the high speed region is as follows. That is, as described above, the engine temperature rises in the high-speed region, the temperature of the air-fuel mixture at the time of ignition rises accordingly, the intake charge efficiency decreases, and knocking easily occurs. Therefore, the intake valve retarded closing operation is performed to lower the temperature of the air-fuel mixture to improve intake charging efficiency and prevent knocking.

As is clear from FIG. 3 (G ₇ ), in the high speed region (engine speed> N ₂ ), the intake valve closing timing at which the intake charging efficiency is the best is much larger than 30 ° The value is close to 60 °. Therefore, in order to increase the intake charging efficiency in this high speed region, it is necessary to delay the intake valve closing timing at least as compared with the case of the intake valve early closing operation in the medium speed region. Therefore, in this embodiment, in the high speed region, the same timing as in the low speed region,
For example, at 60 ° after bottom dead center, the intake valves 1a and 1b are closed to perform a late closing operation of the intake valves to prevent knocking and improve intake charging efficiency to increase engine output. In this way, since the closing timings of the intake valves 1a and 1b are the same (60 ° after bottom dead center) in the low speed region and the high speed region, the configuration of the intake valve opening / closing timing changing means 9,
Alternatively, the control mechanism is simplified. It is needless to say that the intake valve closing timing in the high speed region may be different from that in the low speed region.

However, as is clear from FIG.
(G ₇ ), the intake valve closing timing at which the intake charging efficiency becomes the best in the high speed region changes linearly according to the engine speed. Therefore, the intake valve closing timing in the high speed region may be linearly changed according to the engine speed in correspondence with G ₇ in FIG. In this case, the valve closing timing of the intake valves 1a and 1b is set so that the intake charging efficiency becomes maximum at the rated rotation, that is, at the maximum rotation.

As described above, according to this embodiment,
It is possible to increase engine output and emission performance while effectively preventing knocking.
In addition, in the low speed range, fuel consumption performance can be improved by reducing pumping loss.

[0039]

According to the first aspect of the invention, the intake valve retarded closing operation is performed in the low speed region, and therefore the effective compression ratio of the air-fuel mixture in the combustion chamber becomes small, so that the temperature rise due to the compression of the air-fuel mixture. Get smaller. Therefore, the temperature of the air-fuel mixture at the time of ignition becomes relatively low, and the knocking resistance is improved. Originally, in the medium speed range where knocking is unlikely to occur, the intake valve early closing operation is performed, so that the intake charging efficiency is increased and the engine output is increased. In the high speed region where knocking is likely to occur again, the intake valve retarded closing operation is performed to improve the knocking resistance and the intake charging efficiency.

According to the second invention, basically, the same operation and effect as those of the first invention can be obtained. Further, since the intake valve closing timing is set individually in the low speed region and the high speed region, it is possible to set the optimum valve closing timing according to the operating state of the engine, and further improve the knocking resistance and the engine output. You can

According to the third invention, basically, the same operation and effect as those of the first or second invention can be obtained. Further, in the low speed range, the overlap between the opening period of the intake valve and the opening period of the exhaust valve (valve opening overlap) is set small, so that blow-through of air-fuel mixture is prevented and emission performance is improved. . Since the valve opening overlap is set to be large in the medium speed range, the scavenging property is enhanced and the intake charge efficiency is further enhanced.

According to the fourth invention, basically, the same operation and effect as any one of the first to third inventions can be obtained. Furthermore, since the intake valve closing timing in the intake valve retarded closing operation in the high speed region is set at the time when the intake charging efficiency at the rated rotation becomes the highest, the engine output in the high speed region is significantly increased.

According to the fifth invention, basically, the same action and effect as any one of the first to third inventions can be obtained. Furthermore, since the intake valve closing timing in the high speed range is changed linearly with a predetermined characteristic according to the engine speed, it is possible to obtain the best intake charging efficiency according to the engine speed, and the engine output is greatly increased. Be raised to.

[Brief description of drawings]

FIG. 1 is a system configuration diagram around an engine body of an engine with a mechanical supercharger including an intake device according to the present invention.

FIG. 2 is a system configuration diagram of an intake system of an engine with a mechanical supercharger including an intake device according to the present invention.

FIG. 3 shows the amount of HC emission in the engine shown in FIG.
It is a figure which shows the characteristic with respect to engine speed of supercharging pressure and the required valve closing timing of an intake valve.

[Explanation of symbols]

 VE ... Engines # 1 to # 6 ... First to sixth cylinders 1a, 1b ... First and second intake valves 9 ... Intake valve opening / closing timing varying means 10 ... Control unit 16 ... Mechanical supercharger

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Uesugi 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (5)

[Claims] 1. A mechanical supercharger, an intake valve opening / closing timing variable means capable of changing the closing timing of an intake valve, and an intake valve at least in an operating region where supercharging is performed by the mechanical supercharger. (Expansion ratio / effective compression ratio)> 1 such that the intake valve opening / closing timing control means for controlling the intake valve opening / closing timing varying means is closed after the bottom dead center. In this intake system, the intake valve opening / closing timing control means controls the intake valve opening / closing timing varying means so that the intake valve is closed at a relatively slow timing after bottom dead center when viewed from the crank angle in the low speed region and the high speed region. While allowing the engine to perform the intake valve late-closing operation, the intake valve opening / closing timing is variable so that the intake valve is closed earlier than in the intake valve late-closing operation in the medium speed range. An intake system for an engine with a mechanical supercharger, characterized in that the control means controls the engine to perform an intake valve early closing operation. 2. The intake device for an engine with a mechanical supercharger according to claim 1, wherein the intake valve opening / closing timing control means determines the closing timing of the intake valve in a low speed region and a high speed region in terms of crank angle. An intake system for a mechanical supercharged engine, which is set at different times. 3. The intake system for an engine with a mechanical supercharger according to claim 1 or claim 2, wherein the engine valve system has an intake valve open period and an exhaust valve open when viewed from the crank angle. An intake system for a mechanical supercharged engine, wherein an overlap with a valve period is formed to be small in a low speed region and large in a medium speed region. 4. The intake device for an engine with a mechanical supercharger according to any one of claims 1 to 3, wherein the intake valve opening / closing timing control means controls the intake valve late closing operation in a high speed region. The intake device of the engine with a mechanical supercharger is characterized in that the intake valve closing timing in the above is set at a time when the intake charging efficiency at the rated rotation becomes the highest when viewed from the crank angle. 5. The intake device for a mechanical supercharged engine according to claim 1, wherein the intake valve opening / closing timing control means sets the intake valve closing timing in a high speed region. An intake device for an engine with a mechanical supercharger, which is configured to change linearly with a predetermined characteristic according to the engine speed.