JPH08200051A - Cylinder fuel ejection type internal combustion engine - Google Patents

Abstract

PURPOSE: To supply secondary air to an exhaust passage without necessitating popular secondary air pulse induction system having a pump and the like. CONSTITUTION: This device is provided with discharging means 7, 11, 20 for discharging a part of new air supplied into a cylinder in an intake stroke to an exhaust passage 6 by piston operation in the initial period of a compressing stroke, and fuel supplying means 12, 20 for supplying fuel into the cylinder so as to realize a desired air fuel ratio against rest new air in an after compressing stroke.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, emission regulations of harmful components of exhaust gas have become stricter. Therefore, it is desired to reduce harmful components generated in a combustion chamber. Of the harmful components, nitric oxide recirculates the exhaust gas into the combustion chamber, which lowers the combustion temperature due to the large heat capacity of the inert gas that is the main component of the exhaust gas, so the amount generated is reduced well. However, there is no practical means for reducing the generation amount of hydrocarbons and carbon monoxide, and it is necessary to purify them favorably by an oxidation catalytic converter.

In order to oxidize almost all of the hydrocarbons and carbon monoxide contained in the exhaust gas by the oxidation catalytic converter, a sufficient amount of oxygen is required. Therefore, the air-fuel mixture in the combustion chamber is stoichiometrically empty. It may be considered to be leaner than the fuel ratio, but it is not practical because combustion deteriorates. Therefore, generally, a secondary air introducing device for introducing secondary air is provided upstream of the oxidation catalytic converter in the exhaust passage to mix the secondary air with the exhaust gas burned at the stoichiometric air-fuel ratio. Is proposed.

[0004]

Such a secondary air introducing device is not only considerably expensive because it has a pump for pumping the secondary air to the exhaust passage, but also enlarges the internal combustion engine. Is. Therefore, the object of the present invention is to
In a cylinder injection type internal combustion engine, secondary air can be supplied to an exhaust passage without requiring a general secondary air introduction device having a pump or the like.

[0005]

In order to achieve the above-mentioned object, in a cylinder injection type internal combustion engine according to the present invention, a part of the fresh air supplied into the cylinder in the intake stroke is operated by a piston in the early stage of the compression stroke. Discharge means for discharging to the exhaust passage by
Fuel supply means for supplying fuel into the cylinder so as to achieve a desired air-fuel ratio for the remaining fresh air in the subsequent compression stroke.

[0006]

In the cylinder injection type internal combustion engine described above, the discharge means supplies a part of the fresh air before the fuel is supplied by the fuel supply means into the cylinder in the intake stroke by the piston operation in the early stage of the compression stroke. In order to discharge the secondary air to the exhaust passage, the secondary air introducing device having a pump or the like is unnecessary when supplying the secondary air to the exhaust passage.

[0007]

1 is a schematic sectional view showing a first embodiment of a cylinder injection type 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 is an intake passage communicating with the inside of the cylinder via an intake valve 5, and 6 is an exhaust passage communicating with the inside of the cylinder via an exhaust valve 7. The intake passages 4 of the respective cylinders merge at a surge tank 4a and communicate with the atmosphere via an air cleaner 8 located at the most upstream side.

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

Reference numeral 12 is a fuel injection valve for directly injecting fuel into the cylinder, and 13 is a spark plug. 20 is
The control device is in charge of controlling the fuel injection timing and the fuel injection amount in the fuel injection valve 10 and the opening / closing timing control of the exhaust valve 7 by the valve mechanism 11, and each sensor for determining the engine operating state, for example, the engine. A rotation sensor 21 for detecting the number of revolutions, 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, etc. 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 controller 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 is reached.
The cam 10 is opened and closed 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 the fourth crank angle θ4 immediately after the exhaust top dead center TDC1.
In addition to the fixed first opening / closing that is closed at, the valve operating mechanism 11 that can freely change the opening / closing timing is used to make the intake bottom dead center BDC.
The second opening / closing is performed by opening the valve from 1 and closing the valve 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 amount is determined according to the engine operating state based on the output of each sensor described above, and the intake amount is obtained when the maximum intake amount is required. The control device 20 is set so as to match with the bottom dead center BDC1, that is, the second opening / closing is not performed.
It is decided by.

When the intake valve 5 and the exhaust valve 7 are opened and closed in this manner, the exhaust valve 7 is opened and the intake valve 5 is closed immediately after the exhaust top dead center TDC1.
A part of the exhaust gas discharged to the exhaust passage 6 is sucked into the cylinder as a result of the downward movement, and internal exhaust gas recirculation is performed. Thereafter, the intake valve 5 is opened before and after the exhaust valve 7 is closed, and fresh air is sucked into the cylinder from the intake passage 4 up to the intake bottom dead center BDC1.

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

After that, ignition by the spark plug is executed immediately before the compression top dead center TDC2, combustion in the combustion chamber 3 formed on the top surface of the piston 2 is started, and the exhaust valve 7 is moved to the first position just 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 from the expansion bottom dead center BDC2 to the exhaust top dead center TDC1 as the piston 2 rises. Is exhausted to.

This combustion is good because it is the combustion of the stoichiometric air-fuel ratio mixture, and since the exhaust gas is sucked into the cylinder at the beginning of the intake stroke, the combustion temperature is high due to its large heat capacity. And the amount of nitric oxide generated is significantly reduced. On the other hand, although carbon monoxide and hydrocarbons are normally generated, part of the intake air is discharged to the exhaust passage 6 during the compression stroke, and the exhaust gas discharged to the exhaust passage 6 during the exhaust stroke is converted into the oxidation catalytic converter 9
In order to make it leaner than the stoichiometric air-fuel ratio on the upstream side of the exhaust gas, 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 Can be significantly improved. Further, since the throttle valve is not used to control the fresh air amount according to the engine operating state, pumping loss does not occur and the engine generated torque can be increased accordingly.

Further, in the above-mentioned time chart,
As indicated by the dotted line, the closing timing of the first opening / closing of the exhaust valve 7 indicates the fourth crank angle θ4 ′ immediately before the exhaust top dead center TDC1.
It is also possible that a part of the exhaust gas remains in the cylinder in the exhaust stroke, and the exhaust gas recirculation has the same nitrogen oxide reduction effect as described above, and 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 temperature at the time of starting the fuel injection becomes higher, the vaporized state of the injected fuel is improved, and the combustion speed is increased. Combustion can be further improved.

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, the air-fuel mixture at the time of combustion contains almost a predetermined proportion of exhaust gas. It is supposed to be done. However, 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 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 according to the engine operating state by using the valve operating mechanism 11 so as to realize such a mixing ratio of the exhaust gas.

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

The control valve 31 arranged in the communication passage 30 is controlled to be opened / closed by the control device 20 'in the same manner as the second opening / closing of the exhaust valve 7 in the above-mentioned time chart. Therefore, also in the present embodiment, as in the first embodiment, part of the fresh air sucked in the intake stroke can be discharged to the exhaust passage 6 as the piston 2 moves upward in the compression stroke, and the pump etc. The secondary air can be supplied to the exhaust passage without the need for a general secondary air introduction device having

As described above, the present invention is not limited to the case where the secondary air is supplied to the exhaust passage in all engine operating states, but is also applicable to, for example, a cold start of the three-way catalytic converter arranged in the exhaust passage. In order to achieve early warm-up, even when secondary air is supplied to the exhaust passage only at this time so that all unburned fuel in combustion with a rich air-fuel mixture is burned by the three-way catalytic converter. Exhaust gas recirculation as a means for reducing the production of nitric oxide is available, and thus 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, a part of the fresh air before the exhaust means is supplied into the cylinder in the intake stroke and before the fuel is supplied by the fuel supply means. In order to discharge the secondary air to the exhaust passage as secondary air by the piston operation in the early stage of the compression stroke, a general secondary air introduction device having a pump or the like is unnecessary when supplying the secondary air to the exhaust passage, and It is possible to prevent the cost increase and the increase in size of the internal combustion engine caused by the secondary air introduction device.

[Brief description of drawings]

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

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

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

[Explanation 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 mechanism 12 ... Fuel injection valve 20, 20 '... Control device 30 ... Communication passage 31 ... Control valve

Claims (1)

[Claims] 1. A discharge means for discharging a part of fresh air supplied into a cylinder in an intake stroke to an exhaust passage by a piston operation in an early stage of a compression stroke, and a desired empty space for the remaining fresh air in a subsequent compression stroke. An in-cylinder injection internal combustion engine, comprising: a fuel supply unit that supplies fuel into a cylinder so as to achieve a fuel ratio.