JPH0726993A - Intake device of engine provided with mechanical supercharger - Google Patents

Abstract

PURPOSE:To provide the intake device of an engine provided with a mechanical supercharger, thereby the intake device can sufficiently enhance the scavenging performance while preventing the generation of blow-by in the all driving range, and has a simple structure. CONSTITUTION:In an engine VE provided with a mechanical supercharger, the opening overlap period is small in the low rotational range, while it is large in the high rotational range, in the low intake air amount range where a S-valve 30 (intake passage opening/closing valve) is closed. Moreover, in the high intake air amount range where the S-valve 30 is opened, the opening overlap period is small in the low rotational range, while it is large in the high rotational range. Accordingly, the opening overlap amount can be gradually increased by four steps according to the rise of engine speed by a simple structure wherein a VVT 9 (valve timing variable means) is provided to only intake valves 1a, 1b, and the scavenging performance can be enhanced to the approximately maximum while preventing the generation of blow-off in the all driving range.

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.

[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 as described above, there is a problem that knocking easily occurs at high load. Therefore, in a conventional engine with a mechanical supercharger, generally, from the end of the exhaust stroke to the beginning of the intake stroke, the intake port opening period and the exhaust port opening period are overlapped to perform scavenging of the combustion chamber with intake air. , Knocking is suppressed or prevented. here,
Of course, the larger the opening overlap amount, the higher the scavenging property.

In an engine in which each cylinder has two intake ports, a first intake port and a second intake port, an opening / closing valve for opening and closing the second intake port is provided with the first intake port serving as a swirl port to provide a predetermined low intake air. In the air volume region, we also proposed that the on-off valve is closed to supply air to the combustion chamber only from the first intake port to strengthen the swirl, and the swirl enhances the combustibility of the air-fuel mixture to suppress knocking. (See, for example, Japanese Patent Laid-Open No. 62-159728).

However, when the opening period of the intake port and the opening period of the exhaust port are overlapped in this way, if the opening overlap amount is too large, the air-fuel mixture sucked into the combustion chamber is discharged as it is from the exhaust port. Such a phenomenon as so-called blow-through occurs, and there is a problem that emission performance is deteriorated due to an increase in HC emission amount.

The maximum value of the opening overlap amount (hereinafter, referred to as a limit overlap amount) that does not cause such blow-through is not constant, but increases as the engine speed increases. For example, when the engine speed is 1000 rpm, the limit overlap amount is about 10 °.
Although it is CA (crank angle), the limit overlap amount is about 80 ° CA at 6000 rpm. Therefore,
If the amount of opening overlap is fixed, it is difficult to maximize scavenging while preventing blow-through in all operating regions.

By the way, in recent years, there has been proposed an engine with a supercharger, which is provided with a mechanism capable of changing the opening / closing timing of a valve, so-called valve timing varying means (see, for example, JP-A-63-239312). Therefore,
In such an engine, the opening / closing timing of the valve is changed according to the engine speed, and the opening overlap amount is changed by this so that the opening overlap amount is adapted to the engine speed to prevent blow-through and prevent scavenging (anti-knocking). It is conceivable that the method of improving

[0007]

In this case, if the opening overlap amount is changed linearly in accordance with the engine speed, the scavenging property is maximized while preventing blow-through in the entire rotation range. Of course you can. However, in order to linearly change the opening / closing timing of the intake valve or the exhaust valve, the valve timing changing means has to have a very complicated structure, and it is difficult to practically adopt such a method.

Therefore, it is practical to switch the opening overlap amount by using a normal valve timing varying means which switches the opening / closing timing in two steps. In this case, either the intake valve or the exhaust valve is switched. If the valve timing varying means is provided only on one side, the opening overlap amount can be switched only in two steps.
It is difficult to achieve an appropriate opening overlap amount according to the engine speed over the entire operating range.

Therefore, a method is conceivable in which valve timing varying means is provided for both the intake valve and the exhaust valve, and the opening overlap amount is switched in four stages according to the engine speed. However, in this case, since it is necessary to provide two sets of valve timing varying means, there is a problem that the engine becomes large and the cost thereof increases.

The present invention has been made in order to solve the above-mentioned conventional problems, and is inexpensive and simple in that the scavenging property can be sufficiently enhanced while preventing the occurrence of blow-through in the entire operating region. An object of the present invention is to provide an intake device for an engine with a mechanical supercharger having a structure.

[0011]

In order to achieve the above object, a first aspect of the present invention is directed to a first intake port for supplying air to a combustion chamber in the entire operation region, and a predetermined high intake air amount region. In the intake system of the engine with the mechanical supercharger, which is configured with the second intake port that supplies air to the combustion chamber only, by changing the opening / closing timing of either the intake valve or the exhaust valve. In view of the crank angle, a valve timing variable means is provided which can switch the opening overlap period between the intake port and the exhaust port into two steps, large and small. The valve timing variable means reduces the opening overlap period. The sum of the opening overlap amount between the first intake port and the exhaust port and the opening overlap amount between the second intake port and the exhaust port is The first and second intake ports and the exhaust port are set to be larger than the opening overlap amount between the first intake port and the exhaust port in a state where the opening overlap period is made large by the valve timing varying means. The opening and closing timing is set, and at least in the high load region, the opening overlap period becomes small in the region on the low intake air amount side in the operating region where the supply of air from the second intake port is stopped, and the high intake air amount An overlap amount control means for controlling the valve timing varying means is provided so that the opening overlap period becomes large in the region on the side and the opening overlap period becomes small in the operating region where air is also supplied from the second intake port. The present invention provides an intake device for an engine with a mechanical supercharger.

According to a second aspect of the present invention, in the intake system for the engine with a mechanical supercharger according to the first aspect, the overlap amount control means has a low value in an operating region where air is supplied also from the second intake port. The valve timing varying means is controlled so that the opening overlap period is short in the intake air amount side region and the opening overlap period is large in the high intake air amount side region. An intake device for an engine with a supercharger is provided.

In a third aspect of the invention, in the intake system for an engine with a mechanical supercharger according to the first or second aspect, most of the opening overlap between the second intake port and the exhaust port is on the exhaust side. Provided is an intake system for a mechanical supercharged engine, wherein the opening and closing timings of the second intake port and the exhaust port are set so as to occur before the dead center.

A fourth aspect of the present invention is an intake system for an engine with a mechanical supercharger according to any one of the first to third aspects, wherein an opening overlap between the first intake port and the exhaust port is provided. First to occur mostly after exhaust top dead center
Provided is an intake system for an engine with a mechanical supercharger, wherein opening and closing timings of an intake port and an exhaust port are set.

A fifth aspect of the present invention is the intake system for an engine with a mechanical supercharger according to any one of the first to fourth aspects, wherein the opening overlap amount is between the intake port and the exhaust port. During the period in which the opening overlap occurs, it is represented by the integral value of the crank angle of the opening area of the port with the smaller opening area. Provide an intake device.

[0016]

EXAMPLES Examples of the present invention will be specifically described below. <First Embodiment> As shown in FIG. 1 and FIG.
In the 6-cylinder V-type engine VE having the cylinders # 1 to # 6, the first, third and fifth cylinders # 1, # 3,
# 5 is arranged, and the second, fourth, and sixth cylinders # 2, # 4, and # 6 are arranged on the second bank Q side. Where each cylinder # 1
~ # 6 are ignited in the order of # 1 → # 2 → # 3 → # 4 → # 5 → # 6. Therefore, the intake strokes of the cylinders # 1, # 3, # 5 on the first bank P side do not overlap with each other, and the intake strokes of the cylinders # 2, # 4, # 6 on the second bank Q side also do not overlap with each other. Not duplicate. In the following, for convenience,
In the vicinity of the engine body, the longitudinal direction of the engine VE
The fifth cylinder # 5 side is referred to as "left" and the first cylinder # 1 side is referred to as "right" as viewed in the left-right direction in FIG.

In each of the cylinders # 1 to # 6, when the first and second intake valves 1a and 1b are opened, the 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. In the following, for convenience,
The first intake port 2a is abbreviated as P port 2a, and the second intake port 2b is abbreviated as S port 2b. Also,
First and second fuel injection valves 5a and 5b are provided facing the P and S ports 2a and 2b, respectively, for injecting fuel into intake air in the ports to form a mixture. In addition, the third to third in FIG.
For the sixth cylinder # 3 to # 6, the first and second cylinders # 1, #
Since the structure is the same as that of 2, the numbering of each member 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.
A valve timing changing means 9 (hereinafter, abbreviated as VVT 9 for convenience) that can change the opening / closing timing of the intake valves 1a and 1b in two stages is provided.
Each T9 is controlled by the control unit 10. Since the VVT 9 only shifts the opening / closing timing of the first and second intake valves 1a, 1b in two steps in the advance direction or the retard angle direction, even when the open / close timing is changed, the valve opening period (crank Does not change).

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 VVT is not provided for the exhaust valve in the first embodiment, the opening / closing timing of the exhaust valve (exhaust port 4) is fixed in terms of crank angle.

The VVT 9 is on / off controlled by the control unit 10, and the opening and closing timings of the first and second intake valves 1a and 1b are set to the advance side (small crank angle side) and the retard side.
(The side where the crank angle is large) can be set. Specifically, when the VVT 9 is in the off state, the opening / closing timing of the first and second intake valves 1a, 1b is set to the retard side. At this time, the first intake valve 1a (P port 2a) is opened and closed at the timing shown by the curve I ₁ in FIG. 3, and the second intake valve 1b (S port 2b) is opened at the timing shown by the curve I ₂ in FIG. It is opened and closed.

On the other hand, when the VVT 9 is in the ON state, the opening / closing timing of the first and second intake valves 1a, 1b is set to the advance side. At this time, the first intake valve 1a (P port 2a) is opened and closed at the timing shown by the curve I ₁ ′ in FIG. 3, and the second intake valve 1b (S port 2b) is shown by the curve I ₂ ′ in FIG. It opens and closes at the timing. Exhaust valve
The (exhaust port 4) is always opened and closed at the timing shown by the curve E in FIG.

As is apparent from FIG. 3, both intake valves 1a, 1
The opening / closing timing of b is set so that the second intake valve 1b (S port 2b) is opened a predetermined crank angle ahead of the first intake valve 1a (P port 2a). In addition,
Since the VVT 9 only shifts the first and second intake valves 1a and 1b uniformly in the advance direction or the retard direction by the same phase, the first intake valve 1 does not matter whether the VVT 9 is on or off.
It goes without saying that the deviation of the valve opening timing between the a and the second intake valve 1b is constant.

Therefore, when the VVT 9 is in the off state, the opening overlap period (or the opening overlap amount) between the P, S ports 2a, 2b and the exhaust port 4 is reduced in the crank angle, while the VVT 9 is decreased. When in the ON state, the opening overlap period (or opening overlap amount) between the P, S ports 2a, 2b and the exhaust port 4 becomes large.

Here, the opening / closing timings of the P, S ports 2a, 2b and the exhaust port 4 and the opening / closing timing change amount by the VVT 9 are set so as to satisfy the following expression 1.

[Number 1] _{θ 1 + θ 2> θ 3} ............................................................ formula 1 In Expression 1, theta ₁ is when the VVT9 is off The opening overlap amount between the P port 2a and the exhaust port 4, θ ₂ is the opening overlap amount between the S port 2b and the exhaust port 4 when the VVT 9 is in the off state, and θ ₃ is P when VVT9 is on
It is the amount of opening overlap between the port 2a and the exhaust port 4.

Here, the overlap amounts θ _{1 to} θ ₃ are values corresponding to the integrated value of the crank angle of the opening area of the port having the smaller opening area within the period in which the opening overlap occurs. I am trying to represent it. That is, θ ₁ is a value corresponding to the region surrounded by the curve I ₁ , the curve E, and the horizontal axis in the period of the crank angle T _{1 to} T ₃ in FIG. theta ₂ is a value corresponding to the crank angle is surrounded by and the horizontal axis the curve I ₂ and the curve E over a period of T ₂ through T ₃ regions in FIG. Also, θ ₃ is
In FIG. 3, the crank angle is a value corresponding to the region surrounded by the curve I ₁ ′, the curve E and the horizontal axis within the period of T ₁ ′ to T ₃ . The opening overlap amount may be simply represented by the opening overlap period (crank angle).

As is apparent from FIG. 3, the P port 2a,
The opening / closing timing of the S port 2b and the exhaust port 4 is P
Most of the opening overlap between the port 2a and the exhaust port 4 is set to occur after the exhaust top dead center TDC. Therefore, the negative pressure generated by the descending piston suppresses the movement of the air flowing into the combustion chamber 3 from the P port 2a toward the exhaust port 4, and the air is supplied into the combustion chamber 3 only from the P port 2a. The blow-by in the operating region is suppressed. Moreover, most of the opening overlap between the S port 2b and the exhaust port 4 is the exhaust top dead center T.
It is set to occur before DC. Therefore, the air in the combustion chamber 3 is pushed up to the exhaust port 4 side by the rising piston, and the combustion chamber 3 also passes through the S port 2b.
The scavenging property in the operating region where air is supplied is enhanced.

A common intake passage 12 is provided to supply 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, 27, the communication passage opening / closing valve 26, and the communication passage shutter valves 28a, 28b effectively utilize the resonance effect or the inertial effect in accordance with the engine speed, and thereby, 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 inertia effect. The intake charging efficiency is improved.

In the first surge tank 23, the 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 are connected to the P and S ports 2a and 2b of the corresponding cylinders. On the other hand,
The second surge tank 24 has the second, fourth, and sixth cylinders # 2, #
Three sets of first and second independent intake passages 29a, 29b for 4 and # 6
Are connected to the upstream ends thereof, and the downstream ends of the first and second independent intake passages 29a and 29b are connected to the P and S ports 2a and 2b of the corresponding cylinders, respectively. Although not shown in detail, the P port 2a is a tangential type or helical type swirl port and supplies air to the combustion chamber 3 in the entire operation region.

Second independent intake passage 29 of each cylinder # 1 to # 6
Each of the b is provided with an intake passage opening / closing valve 30 (hereinafter, referred to as an S valve 30 for convenience) that opens and closes them. Each S valve 30 is connected to the control unit 10
The on-off valve actuator 40 opens and closes according to the signal from the. Here, when each S valve 30 is closed, P port 2 which is a swirl port
Air (air-fuel mixture) is supplied into the combustion chamber 3 only from a, a strong swirl is generated in the combustion chamber 3, and the ignitability / combustibility of the air-fuel mixture is enhanced. On the other hand, when the S valve 30 is opened, air is supplied into the combustion chamber 3 from both ports 2a and 2b, so that the intake charging efficiency is improved. Note that each S valve 30 is configured to be closed in a predetermined low intake air amount region, as will be described later.
Therefore, the S port 2b supplies air to the combustion chamber 3 only in a predetermined high intake air amount region.

Incidentally, instead of providing such an S valve 30, a valve stop mechanism is provided for the second intake valve 1b, and in a predetermined low intake air amount region, the second intake valve 1b is operated by the valve stop mechanism.
May be always closed to supply air into the combustion chamber 3 only from the P port 2a.

The first and second fuel injection valves 5a and 5b of each of the cylinders # 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.

Then, the assist air supply passage 31 is branched midway into the first and second branch assist air supply passages 31a and 31b, and through the first branch assist air passage 31a, each fuel injection valve 5a on the first bank P side, 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 into the exhaust port 4 is discharged into 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 generated, 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 of the engine VE including the "overlap amount control means" described in the claims, and the intake air amount detected by the air flow sensor 14, the first The intake air temperature detected by the intake air temperature sensor 45, the throttle opening (engine load) detected by the throttle sensor 46, the intake air temperature downstream of the supercharger detected by the second intake air temperature sensor 47, the third and third 4 Intake temperature sensor 48,4
Various control of the engine VE is performed by using the intake air temperature downstream of the intercooler detected by 9 and the engine speed detected by a speed sensor (not shown) as control information.

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 of the present invention, its explanation is omitted. Below, the first and second intake air intakes relating to the subject of the present invention will be described. Open / close timing control of valves 1a and 1b,
1 to 3 as appropriate only for the opening and closing control of the S valve 30.
Will be described with reference to. That is, in the engine VE, the control unit 10 controls the opening / closing timing of the first and second intake valves 1a and 1b, that is, the P and S ports 2a and 2 according to the engine speed and the engine load (throttle opening).
By controlling the opening overlap state between b and the exhaust port 4 and the opening / closing state of the S valve 30, the scavenging property is sufficiently enhanced and the knocking is prevented or suppressed while preventing the occurrence of blow-through in the entire operating region. It is supposed to do.

(1) Low intake air amount region As shown in FIG. 5, on the low load side of the curve G ₁ indicating the full load state, on the low intake air amount side (the low rotation / low load side) of the straight line G _2. ) Region 1 or low intake air amount region, S
The valve 30 is closed, and air (mixture) is supplied into the combustion chamber 3 only from the P port 2a. In this case, a strong swirl is generated in the combustion chamber 3, which enhances the combustibility of the air-fuel mixture and suppresses knocking.

In the low intake air amount region (region 1) where the engine speed is equal to or lower than the predetermined value N ₁ , VVT
9 is turned off, and the opening overlap period is set small. At this time, the opening and closing timings of the P and S ports 2a and 2b are shown in FIG.
It is set like the curves I ₁ and I ₂ inside. In this case, the S-valve 30 is closed, and thus the S-port 2b is substantially closed, so that the opening overlap is the P-port 2a.
Between the exhaust port 4 and the exhaust port 4. Therefore, the opening overlap amount θ ₁ in this case has a value corresponding to the area of the portion (T _{1 to} T ₃ ) surrounded by the curve I ₁ , the curve E, and the horizontal axis in FIG. 3. Therefore, the opening overlap amount θ ₁ becomes considerably small, and therefore blow-through is reliably prevented. On the other hand, the scavenging property is slightly deteriorated, and it seems that the knock resistance is apparently reduced, but in this case, since the strong swirl is generated in the combustion chamber 3 as described above, the combustibility of the air-fuel mixture is enhanced, Thereby, the knock resistance is sufficiently enhanced. Therefore, the occurrence of knocking is prevented or suppressed.

The region where the opening overlap period is small in the region where the engine speed is equal to or lower than N _{1 in} the region ₁ is the region 3 surrounded by the curves G ₁ and G ₃ and the vertical axis (the diagonal line is a shaded area). It is also possible to limit it to the low intake air amount side of the high load region in the low intake air amount region (region 1). That is, in the low load region, the negative pressure in the combustion chamber 3 becomes strong, and blow-through is relatively unlikely to occur,
This is because it is preferable to increase the opening overlap amount to improve the scavenging property in the low load region.

On the other hand, in the region where the engine speed exceeds N ₁ in the low intake air amount region (region 1), the VVT 9 is turned on and the opening overlap period is made large. That is, the opening and closing timings of the P and S ports 2a and 2b are set as shown by the curves I ₁ 'and I ₂ ' in FIG. 3, respectively. Also in this case, since the S port 2b is substantially closed, the opening overlap occurs only between the P port 2a and the exhaust port 4. Therefore, the opening overlap amount θ in this case
₃ is a value corresponding to the area of the portion (T ₁ 'to T ₃ ) surrounded by the curve I ₁ ′, the curve E and the horizontal axis in FIG. 3. Here, since the opening overlap amount θ ₃ is larger than the above θ ₁ , the scavenging property is enhanced and the knock resistance is enhanced. In this case, since the opening overlap amount becomes large, it seems that blow-through occurs. However, as described above, the limit overlap amount increases as the engine speed increases, so the blow-through does not occur. Therefore, while preventing the occurrence of blow-through, the high scavenging property and the strong swirl can enhance the knock resistance and prevent or suppress the occurrence of knocking.

When the area where the opening overlap period is small is limited to the area 3, the VVT 9 is turned on in all areas other than the area 3 in the low intake air amount area (area 1), and the opening overlap period is reduced. Of course, it is big.

(2) High intake air amount region In the low load side of the curve G _{1, the} region ₂ on the high intake air amount side (high rotation / high load side) of the straight line G ₂ , that is, in the high intake air amount region is S The valve 30 is opened, and air (mixture) is supplied into the combustion chamber 3 from both ports 2a and 2b. In this case, the intake charging efficiency is increased and the engine output is sufficiently increased.

In the high intake air amount region (region 2), VV is set in a region where the engine speed is equal to or lower than a predetermined value N _3.
T9 is turned off, and the opening overlap period is set small. That is, the opening / closing timings of the P and S ports 2a and 2b are set as shown by the curves I ₁ and I ₂ in FIG. 3, respectively. At this time, S
Since the valve 30 is open, an opening overlap will occur between both ports 2a, 2b and the exhaust port 4.
Therefore, the opening overlap amount in this case is the portion (T ₁ surrounded by the curves I ₁ and E and the horizontal axis in FIG. 3).
Through T ₃₎ and the opening overlap amount theta ₁ which corresponds to the area of the curve I ₂ and the curve E and the opening overlap amount theta ₂ which corresponds to the area of the horizontal axis and the portion surrounded by (T ₂ ~T ₃₎ Sum of (θ ₁ + θ ₂ )
Becomes

As described above, since θ ₁ + θ ₂ > θ ₃ (see Formula 1), the aperture overlap amount in this case
(θ ₁ + θ ₂ ) becomes larger than the opening overlap amount θ ₃ in the region where the engine speed in region 1 exceeds N ₁ ,
The scavenging property is further enhanced and the knock resistance is enhanced. Since the limit overlap amount increases as the engine speed increases, it goes without saying that blow-through does not occur in this case as well.

In the region 2 where the engine speed is N ₃ or less, the region where the opening overlap period is made small is a region 4 (diagonal line) surrounded by the curve G ₁ , the straight line G ₂ and the curve G _4. (Region marked with), that is, high intake air amount region (region 2)
It may be limited to the region on the low intake air amount side of the high load region. As described above, since blow-through is relatively unlikely to occur in the low load region, it is preferable to increase the opening overlap amount to enhance the scavenging property in the low load region.

On the other hand, in the region where the engine speed exceeds N ₃ in the high intake air amount region (region 2), the VVT 9 is turned on and the opening overlap period is made large. That is, the opening and closing timings of the P and S ports 2a and 2b are set as shown by the curves I ₁ 'and I ₂ ' in FIG. 3, respectively. Also in this case, since the S valve 30 is open, the opening overlap occurs between the ports 2a and 2b and the exhaust port 4. The opening overlap amount in this case is the opening overlap amount θ ₃ corresponding to the area of the portion (T ₁ ′ to T ₃ ) surrounded by the curve I ₁ ′, the curve E and the horizontal axis in FIG. It is the total (θ ₃ + θ ₄ ) of the opening overlap amount θ ₄ corresponding to the area of the portion (T ₂ ′ to T ₃ ) surrounded by the curve I ₂ ′, the curve E and the horizontal axis.

As is clear from FIG. 3, θ ₃ > θ ₁ and θ
_{Since 4} > θ ₂ , the aperture overlap amount (θ ₃
+ Θ ₄ ) becomes larger than the opening overlap amount (θ ₁ + θ ₂ ) in the region where the engine speed in region 2 is N ₃ or less,
The scavenging property is further enhanced and the knock resistance is enhanced. Since the limit overlap increases as the engine speed increases, it goes without saying that blow-through does not occur in this case as well.

When the area in which the opening overlap period is small is limited to the area 4, the VVT 9 is turned on in all areas other than the area 4 in the high intake air amount area (area 2) and the opening overlap period is reduced. Of course, it is big.

That is, according to this first embodiment,
Only by providing the off-type VVT 9 for the intake valves 1a, 1b, the opening overlap amount between the intake ports 2a, 2b and the exhaust port 4 is generally increased as the engine speed increases.
It can be increased in four stages in the order of θ ₁ → θ ₃ → (θ ₁ + θ ₂ ) → (θ ₃ + θ ₄ ). Therefore, it is possible to set the opening overlap amount to a substantially limit overlap amount (maximum overlap amount that does not cause blow-through) in the entire operation region with a simple configuration and therefore at low cost.
It is possible to maximize scavenging performance and significantly improve knock resistance while preventing blow-through. As described above, in the low intake air amount region (region 1), the swirl enhances the combustibility of the air-fuel mixture, which also enhances the knock resistance.

<Second Embodiment> Although not shown in detail, an on / off type VV is used for the exhaust valve instead of the intake valve.
The opening overlap amount may be switched to four stages by providing T and changing the opening / closing timing of the exhaust valve (exhaust port). In this case, as shown in FIG. 4, the opening and closing timings of the first and second intake valves 1a, 1b (P, S ports 2a, 2b) are fixed as indicated by curves I ₁ , I ₂ , respectively.
On the other hand, the opening / closing timing of the exhaust valve (exhaust port 4) is VV
When T is off, it is set like curve E, while VVT
When is on, the curve E'is set.

Therefore, when VVT is off, P, S
The opening overlap period between the ports 2a and 2b and the exhaust port 4 becomes short, while the opening overlap period becomes large when the VVT is on. Therefore, also in the second embodiment, the VVT is turned on / off in accordance with the operating state and the S valve 30 is opened / closed by the same method as in the first embodiment to prevent the occurrence of blow-through in the entire operating region. In addition, the scavenging property can be almost maximized and the knock resistance can be significantly improved.

[0054]

According to the first aspect of the invention, in the region where the supply of air from the second intake port is stopped, that is, in the low intake air amount region (generally low rotation region), the region on the low intake air amount side. (Region on low rotation side) Overlap period
(Crank angle) is considered small. Therefore, in this region, the opening overlap occurs only between the first intake port and the exhaust port, and the opening overlap period is shortened, so that the opening overlap amount becomes small and the occurrence of blow-through is prevented, Emission performance is improved. At this time, since air is supplied into the combustion chamber only from the first intake port, swirl is generated in the combustion chamber, the knock resistance is enhanced by the swirl, and knocking is prevented or suppressed. A region on the high intake air amount side in a region where the supply of air from the second intake port is stopped
The aperture overlap period is large in (a region on the high rotation side). Therefore, since the opening overlap amount is larger than that in the case of the region on the low intake air amount side, the scavenging property is enhanced and the knock resistance is further enhanced. Since the opening overlap amount that causes blow-through increases as the engine speed increases, blow-through does not occur in this case. The opening overlap period is small in a region where air is also supplied from the second intake port, that is, in a high intake air amount region (generally a high rotation region), but in this case, the first and second intake ports and the exhaust port are Since the opening overlap occurs between the two, the opening overlap amount becomes larger than that in the region on the high intake air amount side in the region where the supply of air from the second intake port is stopped. Therefore, the scavenging property can be further enhanced and the knock resistance can be enhanced. Since the engine speed is high in this region, no blow-through occurs even though the opening overlap amount is large. Therefore, with a simple structure in which the valve timing varying means is provided only on either the intake valve or the exhaust valve, that is, at a low cost, the opening overlap amount is gradually increased in three stages according to the increase in the engine speed. Can be increased. Therefore, the scavenging property can be almost maximized while preventing the occurrence of blow-through, and the knock resistance can be significantly improved.

According to the second invention, basically, the same operation and effect as those of the first invention can be obtained. Further, in the region where the air is supplied from the second intake port as well, in the region on the low intake air amount side (the region on the low rotation side), the opening overlap period is short, while on the high intake air amount side. In the region (generally the region on the high rotation side), the aperture overlap period is large. Therefore, in the region where the air is also supplied from the second intake port, the opening overlap amount can be increased stepwise in two stages as the engine speed increases. Therefore, in the entire operation region, the opening overlap amount can be increased stepwise in four stages according to the increase in the engine speed. Therefore, it is possible to further improve the scavenging property while preventing the occurrence of blow-through.

According to the third invention, basically, the same operation and effect as those of the first or second invention can be obtained. Further, since most of the opening overlap between the second intake port and the exhaust port occurs before the exhaust top dead center, the air that has flowed into the combustion chamber is pushed to the exhaust port side by the rising piston. Therefore, the scavenging property in the operating region where the air is supplied from the second intake port to the combustion chamber is further enhanced.

According to the fourth invention, basically the same action and effect as any one of the first to third inventions can be obtained. Further, since most of the opening overlap between the first intake port and the exhaust port occurs after the exhaust top dead center, the negative pressure of the descending piston causes the air flowing from the first intake port into the combustion chamber. Outflow to the exhaust port is hindered, and blow-through is more reliably prevented.

According to the fifth invention, basically the same action and effect as any one of the first to fourth inventions can be obtained. Furthermore, since the opening overlap amount is expressed by the integrated value of the crank angle of the opening area of the port with the smaller opening area during the period when the opening overlap occurs, the opening overlap period (crank angle It is possible to accurately grasp the scavenging characteristic or the blow-through characteristic, as compared with the case where the opening overlap amount is represented.

[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 the engine shown in FIG.

3 is a diagram showing opening / closing timings of an intake port and an exhaust port of the engine shown in FIG.

FIG. 4 is a diagram showing opening / closing timings of an intake port and an exhaust port of an engine according to a second embodiment.

5 is a diagram showing operating characteristics of a valve timing varying means (VVT) and an intake passage opening / closing valve (S valve) of the engine shown in FIG. 1 with respect to engine speed and engine load.

[Explanation of symbols]

 VE ... Engine # 1 to # 6 ... First to sixth cylinders 1a, 1b ... First and second intake valves 2a ... First intake port (P port) 2b ... Second intake port (S port) 3 ... Combustion chamber 4 ... Exhaust port 9 ... Valve timing variable means (VVT) 10 ... Control unit 16 ... Mechanical supercharger 30 ... Intake passage opening / closing valve (S valve)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location F02D 23/00 K 7536-3G F02M 69/00 310 E 9429-3G 360 C 9429-3G G 9429- 3G (72) Inventor Tatsuya Uesugi 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (5)

[Claims] 1. An intake port comprises a first intake port for supplying air to the combustion chamber in the entire operating region and a second intake port for supplying air to the combustion chamber only in a predetermined high intake air amount region. In the intake system for the engine with a mechanical supercharger, the opening overlap between the intake port and the exhaust port in terms of crank angle is changed by changing the opening / closing timing of either the intake valve or the exhaust valve. A valve timing variable means that can switch the period between large and small two stages is provided, and between the first intake port and the exhaust port in the state where the opening overlap period is short by the valve timing variable means. The sum of the opening overlap amount and the opening overlap amount between the second intake port and the exhaust port is determined by the valve timing changing means. The opening and closing timings of the first and second intake ports and the exhaust port are set so that they are larger than the opening overlap amount between the first intake port and the exhaust port in the state where In the load region, the opening overlap period is short in the region on the low intake air amount side in the operating region where the supply of air from the second intake port is stopped, and the opening overlap period is in the region on the high intake air amount side. A machine characterized in that an overlap amount control means for controlling the valve timing varying means is provided so that the opening overlap period becomes small in an operating region where air is supplied from the second intake port as well. Intake device for a supercharged engine. 2. The intake system for an engine with a mechanical supercharger according to claim 1, wherein the overlap amount control means has a low intake air amount in an operating region in which air is also supplied from the second intake port. The valve timing varying means is controlled so that the opening overlap period is small in the region on the side of the valve and the opening overlap period is large in the region on the side of the high intake air amount. Air intake device for engine with engine. 3. The intake system for a mechanical supercharged engine according to claim 1, wherein most of the opening overlap between the second intake port and the exhaust port is exhaust top dead center. An intake device for an engine with a mechanical supercharger, characterized in that the opening and closing timings of the second intake port and the exhaust port are set so as to occur earlier than this. 4. The intake device for a mechanical supercharged engine according to any one of claims 1 to 3, wherein most of the opening overlap between the first intake port and the exhaust port. The intake device for the engine with the mechanical supercharger is characterized in that the opening and closing timings of the first intake port and the exhaust port are set so as to occur after the exhaust top dead center. 5. The intake device for an engine with a mechanical supercharger according to any one of claims 1 to 4, wherein the opening overlap amount is such that the opening overlap is between the intake port and the exhaust port. The intake device for the engine with a mechanical supercharger is characterized by being represented by an integrated value of the crank angle of the opening area of the port having the smaller opening area during the period when the lap occurs. .