JP2001248465A - Intake/exhaust valve driving device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently lower a combustion temperature within a combustion chamber by recirculation of exhaust gas. SOLUTION: The combustion chamber 5 of an internal combustion chamber is connected with intake passages 7, 15 and is connected with exhaust passages 9, 24. In the intake passages 7, 15, intake valves 6 are arranged. In the exhaust passages 9, 24, exhaust valves 8 are arranged. In the intake passages 7, 15, EGR valves 53 are arranged. In an intake stroke, the intake valves 6 are opened. In an exhaust stroke, the exhaust valves 8 are opened. The EGR valves 53 are opened in the exhaust stroke and the EGR valves 53 are closed in the intake stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake and exhaust valve driving device for an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, there is known a technique for reducing the amount of nitrogen oxides (hereinafter, NOx) generated in a combustion chamber by suppressing the combustion temperature in the combustion chamber.
For example, as a technique for reducing the amount of generated NOx, a technique for recirculating exhaust gas into a combustion chamber is disclosed in, for example, Japanese Patent Application Laid-Open No.
-88646. In this publication, the exhaust gas is released into the intake passage by opening the intake valve in the exhaust stroke, and then, when the intake valve is opened in the intake stroke, the exhaust gas in the intake passage together with the air is introduced into the combustion chamber. I am trying to introduce it. The exhaust gas contains a gas having a relatively large heat capacity, for example, carbon dioxide. Therefore, the heat of combustion generated in the combustion chamber is absorbed by the carbon dioxide. Thus, the combustion temperature in the combustion chamber can be kept low, and the amount of generated NOx can be reduced.

[0003]

In the structure disclosed in the above publication, the exhaust gas in the intake passage is introduced into the combustion chamber in such a manner as to be pushed back by the air flowing into the intake passage. For this reason, the exhaust gas is introduced into the combustion chamber without being sufficiently mixed with the intake air. Therefore, the exhaust gas does not exist in the entire combustion chamber, and the effect of lowering the combustion temperature by recirculating the exhaust gas into the combustion chamber is reduced. Accordingly, an object of the present invention is to sufficiently reduce the combustion temperature in a combustion chamber by recirculating exhaust gas.

[0004]

According to a first aspect of the present invention, an intake passage is connected to a combustion chamber of an internal combustion engine, an exhaust passage is connected, and an intake valve is disposed in the intake passage. And an exhaust valve is arranged in the exhaust passage,
In an intake / exhaust valve driving device for an internal combustion engine, wherein the intake valve is opened in an intake stroke and the exhaust valve is opened in an exhaust stroke, an opening / closing valve is arranged in the intake passage, and the opening / closing valve is moved in the exhaust stroke. The valve opens and closes during the intake stroke. According to this, since the on-off valve is opened in the exhaust stroke, exhaust gas is discharged to the intake passage, and an intake valve different from the on-off valve is opened in the intake stroke, so that the exhaust gas in the intake passage burns with air. It flows into the room.

According to a second aspect, in the first aspect, the intake passage is divided into a plurality of intake passage portions by partition walls, and the intake valve and the on-off valve are arranged in separate intake passage portions, respectively. According to a third aspect, in the second aspect, the intake passage portion is connected to the volume chamber on the upstream side of the internal combustion engine.

According to a fourth aspect, in the second aspect, the intake passage portion in which the intake valve is disposed opens into the combustion chamber in a direction deviated from a direction toward the center of the combustion chamber. According to a fifth aspect, in the first aspect, the combustion mode in the combustion chamber can be switched between a stratified combustion mode and a homogeneous combustion mode. When the combustion mode is the homogeneous combustion mode, the combustion mode is the stratified combustion mode. The on-off valve is opened earlier than the opening time of the on-off valve.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 is an overall view showing a four-stroke internal combustion engine of the present invention. 1 is an engine main body, 2 is a cylinder block, 3 is a piston reciprocating in the cylinder block 2, 4 is a cylinder head fixed on the cylinder block 2, and 5 is a combustion formed between the piston 3 and the cylinder head 4. Room, 6 is an intake valve, 7 is an intake port, 8
Denotes an exhaust valve, and 9 denotes an exhaust port. An ignition plug 10 is arranged at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is arranged around the inner wall surface of the cylinder head 4. A cavity 3 a is formed on the top surface of the piston 3.

As shown in FIG. 1, the intake port 7 of each cylinder
Are connected to the inside of the surge tank 16 through the respective intake branch pipes 15. The surge tank 16 is connected to an air cleaner 21 via an intake duct 20, and a throttle valve 23 driven by, for example, a step motor 22 is arranged in the intake duct 20. The step motor 22 is controlled based on an output signal of the electronic control unit 30.

On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust manifold 24, and this exhaust manifold 24 is connected via an exhaust pipe 25 to a casing 2 containing a NOx absorbent 26.
7 is connected. Exhaust manifold 24 and surge tank 1
Reference numeral 6 denotes a recirculated exhaust gas (hereinafter referred to as EGR gas) passage 2
The EGR gas passage 28 is provided with an EGR valve 29 for controlling an EGR gas amount. The EGR valve 29 is controlled based on an output signal of the electronic control unit 30. When the EGR valve 29 is closed, only air is supplied into the combustion chamber 5 through the intake port 7, and when the EGR valve 29 is opened, air and EGR gas are supplied through the intake port 7 to the combustion chamber. 5.

The electronic control unit 30 is composed of a digital computer, and is connected to a random access memory (RAM) 32 and a ROM via a bidirectional bus 31.
(Read only memory) 33, CPU (microprocessor) 34, input port 35 and output port 36. A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is adjusted by an AD converter 37.
Through the input port 35. Top dead center sensor 4
2 generates an output pulse when the first cylinder reaches the intake top dead center, for example, and this output pulse is input to the input port 35. The crank angle sensor 43 generates an output pulse every time the crankshaft rotates 30 degrees, for example, and the output pulse is input to the input port 35. In the CPU 34, the output pulse of the top dead center sensor 42 and the crank angle sensor 43
The current crank angle is calculated from the output pulse, and the engine speed is calculated from the output pulse of the crank angle sensor 43. On the other hand, the output port 36 is connected to each fuel injection valve 11 and the step motor 22 via the corresponding drive circuit 38.

Referring now to FIG. 2, there is shown in detail the intake pipe and intake port of the present embodiment. In the following description, the intake branch pipe 15 and the intake port 7 are collectively referred to as an intake passage 50. The intake passage 50 has two partition walls 51a, 51a.
b divides the intake passage into three intake passage portions 50a, 50b, and 50c. The two partition walls 51a and 51b are connected to the intake passage 50.
Extend parallel to each other within. Therefore, the three intake passage portions 50a, 50b, 50c also extend in the intake passage 50 in parallel with each other. Outer two intake passage portions (hereinafter, referred to as outer intake passage portions) 50 of the three intake passage portions.
a, 50c are connected to the combustion chamber 5; These outer intake passage portions 50a and 50c are connected to the combustion chamber 5 in a direction deviated from the direction of the central axis of the combustion chamber 5. Intake valves 6a, 6c are arranged at intake ports 52a, 52c of outer intake passage portions 50a, 50c communicating with the combustion chamber 5, respectively. The central intake passage portion 50 b of the three intake passage portions is also connected to the combustion chamber 5. The central intake passage portion 50b is a passage portion for recirculating the exhaust gas discharged from the combustion chamber 5 into the combustion chamber 5, and is therefore referred to as an exhaust gas recirculation (EGR) passage portion in the following description. Combustion chamber 5
An opening / closing valve 53 is disposed at the intake port 55 of the EGR passage portion 50b that leads to the opening. The on-off valve 53 is a valve provided for introducing exhaust gas discharged from the combustion chamber 5 back into the combustion chamber, and is hereinafter referred to as an exhaust gas recirculation (EGR) valve. Further, the three intake passage portions 50a, 50b, 50c are connected to the surge tank 16. That is, these intake passage portions 50a, 50b, 50c are assembled in the surge tank 16. The internal combustion engine has two exhaust ports 54a and 54b, and the exhaust ports 54a and 54b are connected to the exhaust port portions 9a and 9b of the exhaust port 9, respectively. These exhaust port portions 9a and 9b merge downstream.

Next, the opening / closing control of the intake valve, the EGR valve, and the exhaust valve in this embodiment will be described. In this embodiment, the opening / closing control pattern is changed according to the combustion mode of the internal combustion engine. Here, the “combustion mode” means a combustion mode classified according to a fuel existence mode in the combustion chamber before the fuel is burned in the combustion chamber. In this embodiment, this combustion mode can be switched between a stratified combustion mode and a homogeneous combustion mode. The "stratified combustion mode" means combustion in which fuel is injected from a fuel injection valve so that the fuel exists only near the spark plug and the fuel is burned. The "homogeneous combustion mode" means that combustion is performed in the entire combustion chamber. The fuel is injected from the fuel injection valve so as to be homogeneous over the fuel injection valve, and the fuel is burned. In the stratified combustion mode, the fuel is collected near the spark plug, so that even a relatively small amount of fuel injected from the fuel injection valve can be satisfactorily burned. Therefore, stratified combustion is preferable from the viewpoint of improving fuel efficiency. However, stratified charge combustion cannot be performed when the amount of fuel to be injected from the fuel injector is relatively large, particularly when the required load is relatively large.

Therefore, in this embodiment, as shown in FIG. 3, when the required output calculated based on the required load L and the engine speed Ne required for the internal combustion engine is relatively small, ie, the required output is determined in advance. When the required output is smaller than the first value (region S in FIG. 3), stratified combustion is performed, and when the required output is relatively large, that is, the required output is larger than the first value and smaller than the first value. When the second predetermined value is smaller than the large second predetermined value (region H1 in FIG. 3), the first homogeneous combustion is performed. When the required output is very large, that is, when the required output is larger than the second value. (Area H in FIG. 3)
In 2), the second homogeneous combustion is performed. The difference between the first homogeneous combustion and the second homogeneous combustion will be described later in detail.

The opening / closing control of the intake valve, the EGR valve and the exhaust valve in the stratified combustion, the first homogeneous combustion and the second homogeneous combustion will be described below with reference to FIGS. 4, 6 and 8, (A) shows one intake valve 8a.
(B) shows the lift curve of the other intake valve 8b, (C) shows the lift curve of the EGR valve 53, and (D) shows the lift curve of the exhaust valves 11a and 11b. 4 and 6
8 and FIG. 8, reference symbol Ex denotes an exhaust stroke, In denotes an intake stroke, Co denotes a compression stroke, Po denotes an explosion stroke, BDC denotes a bottom dead center, and TDC denotes a top dead center. "Lift" means that the intake valve, EGR valve and exhaust valve are opened.
The “lift amount” corresponds to the valve opening degree, and is zero when the valve is closed and increases as the valve opening degree increases.

When the combustion mode is the stratified charge combustion S, as shown in FIG.
a, 6c with the EGR valve 53 and the exhaust valves 8a, 8
b in the intake stroke In, with the EGR valve 53 and the exhaust valves 8a, 8b closed in the intake stroke In.
6c is opened. Thus, the intake valves 6a, 6c, EGR
By controlling the opening / closing of the valve 53 and the exhaust valves 8a and 8b, the following operation occurs. That is, as shown in FIG. 5, by opening the EGR valve 53 with both the intake valves 6a and 6c closed in the exhaust stroke Ex, the exhaust gas flows out of the combustion chamber 5 into the EGR passage portion 50b (FIG. 5). Arrow A1). This exhaust gas flows into the surge tank 16 via the EGR passage portion 50b (see the arrow A2 in FIG. 5). Therefore, the exhaust gas is mixed with the air (see the arrow A3 in FIG. 5) supplied from the intake duct 20 in the surge tank 16. In this embodiment, since the exhaust gas is mixed with air in the surge tank 16 having a relatively large volume, the exhaust gas is uniformly mixed with air.
Next, in the intake stroke In, only the intake valves 6a and 6c are opened with the EGR valve 53 closed, so that the mixture of exhaust gas and air (see the arrow A4 in FIG. 5) is discharged to the outer intake passage portions 50a and 50c. Through the combustion chamber 5.

Since the exhaust gas contains a gas having a relatively large heat capacity, such as carbon dioxide, the heat of combustion in the combustion chamber 5 is absorbed by the gas, and as a result, the combustion temperature in the combustion chamber 5 is reduced. Can be kept low. The combustion temperature is greatly related to the generation amount of nitrogen oxides (NOx).
The x generation amount increases as the combustion temperature increases. Therefore, if the exhaust gas is introduced into the combustion chamber 5 as in this embodiment, NOx
The amount of generation can be kept low. Further, as described above, since the exhaust gas is uniformly mixed with the air, the exhaust gas easily absorbs the heat of combustion. Therefore, according to the present embodiment, the amount of NOx generated can be further reduced. In this embodiment, since the exhaust valves 8a and 8b are opened in the exhaust stroke Ex, the exhaust gas also flows out to the exhaust passage.

When the combustion mode is the first homogeneous combustion H1, as shown in FIG. 6, the EGR valve 53 and the exhaust valves 8a, 8b are closed in the exhaust stroke Ex with both intake valves 8a, 8b closed. The valve is opened and EGR is performed in the intake stroke In.
With the valve 53, the exhaust valves 8a and 8b, and the one intake valve 6c closed, the other intake valve 6a is opened. By controlling the opening and closing of the intake valves 6a and 6c and the EGR valve 53 as described above, the following operation is produced. As shown in FIG. 7, by opening the EGR valve 53 in a state where both the intake valves 6a and 6c are closed in the exhaust stroke Ex, the exhaust gas is
Out of the EGR passage portion 50b (arrow A5 in FIG. 7).
reference). This exhaust gas flows into the surge tank 16 via the EGR passage portion 50b (see the arrow A6 in FIG. 7).
Therefore, the exhaust gas is mixed in the surge tank 16 with the air supplied from the intake duct 20 (see the arrow A7 in FIG. 7). In this embodiment, since the exhaust gas is mixed with air in the surge tank 16 having a relatively large volume, the exhaust gas is uniformly mixed with air. Next, in the intake stroke In, one of the intake valve 6c and the EGR valve 5
By opening only the other intake valve 6a with the valve 3 closed, an air-fuel mixture of exhaust gas and air (see arrow A8 in FIG. 7) flows through one outer intake passage portion 50a into the combustion chamber 5a.
Flows into.

In this way, by opening one of the intake valves 6a in the intake stroke In, the intake gas flows into the combustion chamber 5 in the tangential direction of the combustion chamber 5. At this time, a swirling flow (so-called, so-called,
Swirl) is formed. This swirl allows the intake gas and the fuel to be homogeneously mixed. When the combustion mode is the first homogeneous combustion H1, a high engine output is required. Therefore, it is necessary to uniformly mix the intake air and the fuel. Therefore, by forming a swirl in the combustion chamber 5, atomization of the fuel injected from the fuel injection valve 11 is promoted, and the intake gas and the fuel are homogeneously mixed, so that a high engine output can be obtained.

As can be seen by comparing FIGS. 4 and 6, when the combustion mode is the first homogeneous combustion H1, the opening timing of the EGR valve 53 is changed to the EGR when the stratified combustion S is executed.
The opening timing of the valve 53 is set earlier. The reason for changing the opening timing of the EGR valve 53 in this manner is as follows. In homogeneous combustion, combustion occurs over the entire combustion chamber 5 because the injected fuel is present over the entire combustion chamber 5. Therefore, it is preferable that the exhaust gas is uniformly mixed with the air from the viewpoint of suppressing the generation amount of NOx low. So EG
If the valve opening timing of the R valve 53 is advanced, the exhaust passage portions 50a, 50
Since the period of staying in b and 50c becomes longer, the intake air temperature is not necessarily high due to the influence of heat radiation, but the mixing of the exhaust gas and the air becomes good. Therefore, according to the present embodiment, the amount of NOx generated during homogeneous combustion can be kept low.

On the other hand, in the stratified charge combustion, all the injected fuel is concentrated at one place. Therefore, it is difficult for the fuel to vaporize in the stratified combustion. Therefore, it is preferable that the temperature of the intake gas introduced into the combustion chamber 5 be relatively high from the viewpoint of favorably vaporizing the fuel in the stratified combustion. Therefore, if the opening timing of the EGR valve 53 is delayed, the exhaust gas
The intake passage portions 50a, 5a
Since the period during which the gas stays in the chambers 0b and 50c is short, the mixing of the exhaust gas and the air is not necessarily good, but the intake air temperature is relatively high. Therefore, according to the present embodiment, the vaporization of fuel during stratified combustion is promoted, and the combustion of fuel is improved.

Further, when the combustion mode is the second homogeneous combustion H2, only the exhaust valves 8a and 8b are closed with both intake valves 6a and 6c and the EGR valve 53 closed in the exhaust stroke Ex as shown in FIG. Are opened, and both intake valves 6a and 8b are closed in the intake stroke In with the exhaust valves 8a and 8b closed.
a, 6c and the EGR valve 53 are opened. That is, at the time of the second homogeneous combustion, the intake valves 6a, 6c
The exhaust gas does not flow from the combustion chamber 5 to the EGR passage portion 50b because neither the EGR valve nor the EGR valve 53 is opened. Therefore, in the next intake stroke In, both intake valves 6a, 6c and E
When the GR valve 53 is opened, no exhaust gas is introduced into the combustion chamber 5, and only air is introduced into the combustion chamber 5 (see arrow A10 in FIG. 9). The reason for performing such opening / closing control during the second homogeneous combustion is as follows.

When the required output is relatively high, that is, larger than the second value, a relatively large amount of fuel must be injected from the fuel injection valve, and the injected fuel must be sufficiently burned. That is, when the required output is relatively high, a sufficient amount of oxygen is required to burn the fuel sufficiently. Therefore, the combustion mode is set to homogeneous combustion, and no exhaust gas is discharged into the intake passage.
By opening the valve, the fuel can be sufficiently burned in the combustion chamber, and the required output can be obtained. Therefore, according to this embodiment, since a large amount of air is introduced into the combustion chamber, the fuel can be sufficiently burned,
The required output can be obtained.

In the above-described embodiment, none of the intake valves is opened during the exhaust stroke. However, instead of the EGR valve, the intake valve is opened during the exhaust stroke, or is opened together with the EGR valve during the exhaust stroke. You may. Further, in this case, the intake valve opened in the exhaust stroke may be opened again in the intake stroke or may be kept closed.

In the above description, the embodiment in which the present invention is applied to an internal combustion engine of the type in which combustion is directly injected from a fuel injection valve into a combustion chamber has been described, but fuel is injected into an intake port to mix the fuel and air. The present invention can also be applied to an internal combustion engine of a type in which air is introduced into a combustion chamber and this air-fuel mixture is burned. However, in this case, since the fuel mixes with the air in the intake port, the combustion mode cannot be switched. Therefore, the control other than the combustion mode switching control in the opening / closing control of the above embodiment is applied.

[0025]

According to the present invention, since the on-off valve is opened in the exhaust stroke, exhaust gas is discharged into the intake passage, and an intake valve different from the on-off valve is opened in the intake stroke, so that the air in the intake passage is opened. Exhaust gas flows into the combustion chamber together with air. For this reason, according to the present invention, the exhaust gas discharged into the intake passage has a larger airflow in the intake passage than when the exhaust gas in the intake passage is introduced into the combustion chamber from a valve for discharging the exhaust gas into the intake passage. And mixed well. Therefore, since the exhaust gas exists in the entire combustion chamber, the effect of reducing the combustion temperature by the exhaust gas increases.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine provided with an intake / exhaust valve drive device of the present invention.

FIG. 2 is a diagram showing an intake passage in detail.

FIG. 3 is a diagram showing a map of a combustion mode based on an engine speed and a required load.

FIG. 4 is a time chart showing the operation of each valve when stratified charge combustion is performed.

FIG. 5 is a diagram showing flows of exhaust gas and intake gas during stratified charge combustion.

FIG. 6 is a time chart showing the operation of each valve during execution of the first homogeneous combustion.

FIG. 7 is a diagram showing flows of exhaust gas and intake gas during execution of a first homogeneous combustion.

FIG. 8 is a time chart showing the operation of each valve during execution of the second homogeneous combustion.

FIG. 9 is a diagram showing flows of exhaust gas and intake gas during execution of a second homogeneous combustion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 5 ... Combustion chamber 6a, 6c ... Intake valve 8a, 8b ... Exhaust valve 11 ... Fuel injection valve 51a, 51c ... Outer intake passage part 51b ... EGR passage part 53 ... EGR valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02B 31/00 331 F02B 31/00 331A 31/02 31/02 C F02D 21/08 301 F02D 21/08 301A 41/02 301 41/02 301E F02M 25/07 510 F02M 25/07 510B 570 570A 580 580B 35/104 35/10 311E 35/10 102P 311 301T (72) Inventor Takanobu Ueda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kei Nomura 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G016 AA06 AA17 BA03 BA07 DA01 GA09 3G018 AA12 AB16 EA02 EA11 FA07 FA11 FA23 FA25 GA08 GA09 3G062 AA03 AA07 AA10 BA02 BA04 BA05 CA06 EA09 ED02 ED05 ED06 ED12 ED13 ED15 GA 01 GA04 GA06 GA15 3G092 AA01 AA06 AA10 AA11 AA17 BA07 BB05 CB02 DA08 DA11 DC08 DF01 EA03 EA04 EA11 EA28 FA11 FA21 GA03 GA14 GA16 HA06Y HA11Y HB01Y HB02Y HE01Y HE04Y 3G301 HA01 HA04 HA09 PE03 HA03

Claims (5)

[Claims] An intake passage is connected to a combustion chamber of an internal combustion engine, an exhaust passage is connected, an intake valve is arranged in the intake passage, and an exhaust valve is arranged in the exhaust passage. In an intake / exhaust valve driving device for an internal combustion engine, which opens a valve and opens an exhaust valve in an exhaust stroke, an open / close valve is disposed in the intake passage, and the open / close valve is opened in the exhaust stroke. Is an intake / exhaust valve driving device for an internal combustion engine which is adapted to be closed. 2. The intake passage is divided into a plurality of intake passage portions by a partition wall, and the intake valve and the on-off valve are arranged in separate intake passage portions, respectively.
An intake / exhaust valve drive device for an internal combustion engine according to claim 1. 3. The intake / exhaust valve drive device for an internal combustion engine according to claim 2, wherein the intake passage portion is connected to a volume chamber on an upstream side of the internal combustion engine. 4. An intake passage portion in which the intake valve is disposed opens into the combustion chamber in a direction shifted from a direction toward the center of the combustion chamber.
An intake / exhaust valve drive device for an internal combustion engine according to claim 1. 5. The combustion mode in the combustion chamber can be switched between a stratified combustion mode and a homogeneous combustion mode, and when the combustion mode is the homogeneous combustion mode, the on-off valve is opened when the combustion mode is the stratified combustion mode. 2. The intake / exhaust valve driving device for an internal combustion engine according to claim 1, wherein the on-off valve is opened earlier than the timing.