JP3312514B2 - In-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type internal combustion engine for directly injecting fuel into a cylinder.

[0002]

2. Description of the Related Art In recent years, regulations on the emission of harmful components in exhaust gas have become strict, and it has been desired to reduce harmful components generated in a combustion chamber. Nitrogen oxide, a harmful component, reduces the amount of nitrogen oxides generated by recirculating exhaust gas into the combustion chamber, which reduces the combustion temperature due to the large heat capacity of the inert gas, which is the main component of the exhaust gas. However, there is no practical means for reducing the generation of hydrocarbons and carbon monoxide, and it is necessary to purify the hydrocarbon and the carbon monoxide with an oxidation catalytic converter.

[0003] In order to oxidize almost all hydrocarbons and carbon monoxide contained in exhaust gas by an oxidation catalytic converter, a sufficient amount of oxygen is required. Although it is conceivable to make the fuel leaner than the fuel ratio, it is not practical because combustion deteriorates. Therefore, in general, a secondary air introduction device for introducing secondary air is provided upstream of the oxidation catalytic converter in the exhaust passage to mix secondary air into exhaust gas burned at a stoichiometric air-fuel ratio. It has been proposed.

[0004]

Such a secondary air introducing device is not only very expensive since it has a pump for pumping secondary air to an exhaust passage, but also increases the size of the internal combustion engine. It is. Therefore, the object of the present invention is to
In a cylinder injection type internal combustion engine, it is possible to supply secondary air to an exhaust passage without requiring a general secondary air introduction device having a pump or the like.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, a direct injection internal combustion engine according to the present invention has an exhaust valve in which part of fresh air supplied to a cylinder during an intake stroke is opened.
Discharging means for discharging to an exhaust passage by a piston operation at an early stage of a compression stroke through a valve, and fuel supply means for supplying fuel into a cylinder so as to achieve a desired air-fuel ratio with respect to the remaining fresh air in a subsequent compression stroke , Are provided.

[0006]

In the above-described in-cylinder injection type internal combustion engine, the exhaust means is configured such that the exhaust valve is used to open a part of fresh air which is supplied into the cylinder during the intake stroke and before fuel is supplied by the fuel supply means.
A secondary air introduction device having a pump and the like is not required when supplying secondary air to the exhaust passage as secondary air is discharged to the exhaust passage by the piston operation at the beginning of the compression stroke through the compressor .

[0007]

FIG. 1 is a schematic sectional view showing a first embodiment of a direct injection internal combustion engine according to the present invention. In the figure, 1
Is a cylinder, 2 is a piston, and 3 is a combustion chamber formed on the top surface of the piston 2. Reference numeral 4 denotes an intake passage leading to the cylinder via the intake valve 5, and reference numeral 6 denotes an exhaust passage leading to the cylinder via the exhaust valve 7. The intake passages 4 of the respective cylinders join at a surge tank 4a and communicate with the atmosphere via an air cleaner 8 located at the most upstream portion.

The exhaust passages 6 of the respective cylinders join and are opened to the atmosphere via an oxidation catalytic converter 9. Intake valve 5
Although a general mechanism using a cam 10 that rotates in synchronization with a crankshaft can be used as the valve operating mechanism, the valve operating mechanism 11 of the exhaust valve 6 uses an electromagnetic force or a hydraulic pressure to perform exhaust. The valve 6 can be opened and closed at any time. Since such a valve operating mechanism is already known, its detailed structure is omitted, but for example, it is opposed to a spring which urges in a valve closing direction by supplying a hydraulic pressure to a hydraulic cylinder directly connected to an exhaust valve. A mechanism that opens the exhaust valve and releases the oil pressure to close the exhaust valve by this spring force can be used.

Reference numeral 12 denotes a fuel injection valve for directly injecting fuel into a cylinder, and reference numeral 13 denotes a spark plug. 20 is
This control device is responsible for controlling the fuel injection timing and fuel injection amount of the fuel injection valve 10 and controlling the opening / closing timing of the exhaust valve 7 by the valve operating mechanism 11. Each sensor for determining the engine operating state, for example, the engine A rotation sensor 21 for detecting a rotation speed, an accelerator pedal sensor 22 for detecting a stroke of an accelerator pedal as an engine load, a cooling water temperature sensor 23 for detecting a cooling water temperature, and the like are connected.

FIG. 2 is a time chart showing the opening / closing timing of the intake valve 5 and the opening / closing timing of the exhaust valve 7 controlled by the control device 20. The intake valve 5 is opened from the first crank angle θ1 immediately after the exhaust top dead center TDC1, and the intake bottom dead center B
The cam 10 opens and closes in synchronization with the crankshaft so that the valve is closed at the second crank angle θ2 immediately after DC1. On the other hand, the exhaust valve 7 is opened from the third crank angle θ3 immediately before the expansion bottom dead center BDC2 and becomes the fourth crank angle θ4 immediately after the exhaust top dead center TDC1.
In addition to the fixed first opening / closing that is closed by the valve, the intake bottom dead center BDC is utilized by using the valve mechanism 11 that can freely change the opening / closing timing.
The second opening / closing operation is performed in which the valve is opened from 1 and closed at the fifth crank angle θ during the compression stroke determined by the control device 20.

The fifth crank angle θ is closer to the intake bottom dead center BDC1 as the required intake air amount, which is determined according to the engine operating state based on the output of each sensor described above, increases. The control device 20 is set so as to match the bottom dead center BDC1, that is, not to perform the second opening and closing.
Is determined by

When the intake valve 5 and the exhaust valve 7 are opened and closed in this way, the exhaust valve 7 is opened and the intake valve 5 is closed immediately after the exhaust top dead center TDC1, so that the piston 2
A part of the exhaust gas discharged into the exhaust passage 6 is sucked into the cylinder with the lowering of the exhaust gas, and internal exhaust gas recirculation is performed. Thereafter, before and after the exhaust valve 7 is closed, the intake valve 5 is opened, and fresh air is drawn into the cylinder from the intake passage 4 to the intake bottom dead center BDC1.

Next, the exhaust valve 7 is opened again, and a part of the intake air (fresh air mixed with the exhaust gas at a predetermined ratio) in the cylinder is discharged to the exhaust passage 6 as the piston 2 rises. The exhaust valve 7 is closed and the compression is started when the required amount in the engine operation state is reached. Immediately after the closing of the exhaust valve 7, fuel injection by the fuel injection valve 10 is started, fuel is injected in such an amount as to achieve a stoichiometric air-fuel ratio with respect to the amount of fresh air remaining in the cylinder, and the process ends. In this fuel injection, as the intake air amount is larger, the closing timing of the exhaust valve 7 in the second opening / closing is earlier, so that a larger amount of fuel can be injected.

Thereafter, the ignition by the spark plug is performed immediately before the compression top dead center TDC2, and the combustion in the combustion chamber 3 formed on the top surface of the piston 2 is started, and the exhaust valve 7 is closed immediately before the expansion bottom dead center BDC2. Since the valve is opened from the third crank angle θ3 and closed at the fourth crank angle θ4 immediately after the exhaust top dead center TDC1, the exhaust passage 6 extends from the expansion bottom dead center BDC2 to the exhaust top dead center TDC1 as the piston 2 rises. Exhaust is performed.

This combustion is favorable because it is combustion of a stoichiometric air-fuel mixture, and the exhaust gas is sucked into the cylinder at the beginning of the intake stroke. And the amount of nitric oxide generated is significantly reduced. On the other hand, although carbon monoxide and hydrocarbons are generated as usual, part of the intake air is discharged into the exhaust passage 6 during the compression stroke, and the exhaust gas discharged into the exhaust passage 6 during the exhaust stroke is converted into the oxidation catalytic converter 9.
In order to obtain a state leaner than the stoichiometric air-fuel ratio on the upstream side, almost all of the carbon monoxide and hydrocarbons contained in the exhaust gas are purified by the oxidation catalytic converter 9 using a sufficient amount of oxygen, and the exhaust emission is reduced. Can be considerably improved. Further, since the throttle valve is not used for controlling the fresh air amount according to the engine operating state, no pumping loss occurs and the engine generated torque can be increased accordingly.

In the above-mentioned time chart,
As indicated by a dotted line, the closing timing of the first opening and closing of the exhaust valve 7 is indicated by a fourth crank angle θ4 ′ immediately before the exhaust top dead center TDC1.
It is also possible that, during the exhaust stroke, part of the exhaust gas remains in the cylinder, and in addition to having the same effect of reducing nitrogen oxides as the exhaust gas recirculation, the exhaust gas remaining in the cylinder Since the gas is maintained at a higher temperature than once discharged to the exhaust passage 6, the intake air temperature at the start of fuel injection increases, the vaporized state of the injected fuel improves, and the combustion speed increases. Combustion can be better.

In the above-mentioned time chart, the opening / closing timing of the first opening / closing of the exhaust valve 7 is fixed, so that in each engine operating state, a substantially predetermined ratio of exhaust gas is mixed into the mixture during combustion. It is supposed to be. However, the exhaust gas recirculation is accompanied by some deterioration of combustion, and it is preferable to reduce the mixing ratio of exhaust gas at the time of high engine load requiring high output and at the time of low engine load where combustion is unstable. It is also possible to change the valve closing timing of the first opening / closing of the exhaust valve 7 by using the valve mechanism 11 so as to realize such a mixing ratio of the exhaust gas according to the engine operating state.

FIG. 3 is a schematic sectional view showing a second embodiment of the direct injection internal combustion engine according to the present invention. The difference from the first embodiment shown in FIG. 1 is that the upper part in the cylinder and the upstream side of the oxidation catalyst converter 9 of the exhaust passage 6 are communicated by a communication passage 30, and a control valve 31 is disposed in the communication passage 30. And
The valve mechanism of the exhaust valve 7 does not need to be particularly capable of freely changing the opening / closing timing, and a cam synchronized with a crankshaft set to realize the first opening / closing of the above-described time chart is used. .

The control valve 31 disposed in the communication passage 30 is controlled to be opened and closed by the control device 20 'in the same manner as the second opening and closing of the exhaust valve 7 in the time chart described above. Therefore, according to this embodiment, similarly to the first embodiment, a part of the fresh air sucked in the intake stroke can be discharged to the exhaust passage 6 as the piston 2 rises in the compression stroke, and the pump and the like can be used. The secondary air can be supplied to the exhaust passage without requiring a general secondary air introduction device having the following.

As described above, the present invention is applicable not only to the case where secondary air is supplied to the exhaust passage in all engine operating states, but also to the case where the three-way catalytic converter disposed in the exhaust passage is cold started. In order to achieve early warm-up, even if the secondary air is supplied to the exhaust passage only at this time, all the unburned fuel in the combustion with the rich mixture is burned by the three-way catalytic converter. Exhaust gas recirculation as a means to be available, and thus to reduce the amount of nitric oxide generated, is not a limitation of the present invention.

[0021]

As described above, according to the in-cylinder injection type internal combustion engine of the present invention, the discharge means supplies a part of fresh air to the cylinder during the intake stroke and before the fuel is supplied by the fuel supply means. At the beginning of the compression stroke via the opened exhaust valve.
Because secondary air is discharged into the exhaust passage as secondary air by the piston operation , a secondary air introduction device having a pump and the like is not necessary when supplying secondary air to the exhaust passage, which increases the cost and introduces secondary air. An increase in the size of the internal combustion engine caused by the device can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a direct injection internal combustion engine showing a first embodiment according to the present invention.

FIG. 2 is a time chart showing the opening / closing timing of an intake valve and the opening / closing timing of an exhaust valve controlled by a control device.

FIG. 3 is a schematic sectional view of a direct injection internal combustion engine showing a second embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 ... Piston 3 ... Combustion chamber 4 ... Intake passage 5 ... Intake valve 6 ... Exhaust passage 7 ... Exhaust valve 9 ... Oxidation catalytic converter 11 ... Exhaust valve valve operating mechanism 12 ... Fuel injection valve 20, 20 '... Control device 30 ... Communication passage 31 ... Control valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F01N 3/08-3/36 F01L 9/02 F02D 13/02 F02D 41/02 F02D 41/34

Claims (2)

(57) [Claims] In the intake stroke, a part of fresh air supplied to a cylinder is supplied to a cylinder in an initial stage of a compression stroke through an exhaust valve which is opened.
Discharging means for discharging to the exhaust passage by the stone operation, fuel supply means for supplying fuel into the cylinder so as to achieve a desired air-fuel ratio with respect to the remaining fresh air in a subsequent compression stroke,
A direct injection internal combustion engine, comprising: 2. The exhaust gas used as the exhaust means.
The valve is more likely to require a larger amount of intake air in the current engine operating conditions.
Wherein the valve is closed near the bottom dead center of the intake air.
2. A direct injection internal combustion engine according to claim 1.