JP2004346802A - Exhaust gas reduction device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas reduction device for an internal combustion engine capable of reducing exhaust of unburned gas while ensuring good starting ability. <P>SOLUTION: An opening/closing means for opening/closing a circulation passage is provided on the circulation passage connecting an exhaust passage and an intake passage which are connected to a combustion chamber of the internal combustion engine. A determining means (S14) for determining whether or not the internal combustion engine is in a cranking state, an operating means (S16) which opens the circulation passage by operating the opening/closing means when the determining means (S14) determines the cranking state, a recirculation amount estimating means (S18) for estimating reflux amount of the unburned gas refluxed to the circulation passage, a fuel amount estimating means (S20) for estimating fuel amount of the unburned gas based on the reflux amount estimated by the reflux amount estimating means (S18), and a control means (S22) for correcting a fuel supply amount based on the fuel amount estimated by the fuel amount estimating means (S20) are provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas reduction device for an internal combustion engine which is applied to an internal combustion engine provided with a circulation passage for recirculating gas from an exhaust passage to an intake passage, and reduces the emission of unburned gas.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been proposed a technique for preventing unburned gas among gas discharged from a combustion chamber of an internal combustion engine from being discharged to the outside. For example, in Patent Document 1, an EGR (exhaust gas recirculation) passage for recirculating a part of exhaust gas from an exhaust passage to an intake passage is provided, and a throttle valve and an ISCV (idle speed control valve) are closed when the engine is started. By opening the EGR valve to shut off the intake passage upstream of the EGR passage, and opening the EGR valve to circulate the exhaust gas containing the injected fuel and the combustion chamber using the EGR device, from the start of cranking. Techniques have been proposed to prevent the emission of unburned gas until the start is completed.
[0003]
[Patent Document 1]
JP-A-11-200907 (Page 2, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, in the related art, when the unburned gas is recirculated at the time of starting, the amount of fuel contained in the unburned gas is added, so that an excessive fuel state (over-rich) may occur and the starting may not be stabilized.
[0005]
Further, at the time of so-called hot restart in which the temperature at the time of starting the engine is equal to or higher than a predetermined temperature, vaporized fuel is generated in the fuel transport line, and an appropriate amount of fuel cannot be injected, which may impair the starting performance. was there.
[0006]
The present invention has been made in view of the above circumstances, and has as its object to provide an exhaust gas reducing device for an internal combustion engine that can reduce emission of unburned gas while ensuring good startability. And
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an invention according to claim 1 of the present invention provides a circulation passage (for connecting an exhaust passage and an intake passage connected to a combustion chamber of an internal combustion engine (for example, the engine 2 in the embodiment)). For example, an opening / closing means (for example, an EGR valve 9 in the embodiment) for opening and closing the circulation passage is provided in the EGR passage 8 in the embodiment, and a determination is made to determine whether the internal combustion engine is in a cranking state. Means (for example, the process of step S14 in the embodiment), and actuation means for opening the circulation passage by activating the opening / closing means when the judgment means judges that the cranking state is established (for example, in the embodiment). And the recirculation amount estimating means for estimating the recirculation amount of the unburned gas flowing back to the circulation passage (for example, step S1 in the embodiment). ), A fuel amount estimating means for estimating the fuel amount in the unburned gas from the recirculation amount estimated by the flow rate estimating means (for example, the processing in step S20 in the embodiment), and a fuel amount estimating means. Control means for correcting the fuel supply amount based on the fuel amount estimated by (for example, the process of step S22 in the embodiment).
[0008]
According to this invention, when the determination means determines that the internal combustion engine is in the cranking state, the opening / closing means is opened by the operating means to allow the gas in the exhaust passage to flow through the circulation passage into the intake passage. The fuel amount is estimated by the fuel amount estimating means in accordance with the recirculation amount of the unburned gas estimated by the flow rate estimating means, and the fuel supply amount is corrected by the control means based on the fuel amount. By doing so, it is possible to supply the unburned gas to the combustion chamber again and to adjust the amount of fuel supplied to the combustion chamber to an appropriate amount.
[0009]
Also, even in the case of a hot restart where it is difficult to start because vaporized fuel is generated in the fuel transport line and the amount of fuel required for the start cannot be secured, the unburned gas is circulated through the circulation passage to make the combustion chamber. , The mixing ratio can be adjusted to an appropriate value, and the starting performance can be improved.
[0010]
According to a second aspect of the present invention, in the first aspect, the circulation path is an exhaust recirculation path including an exhaust recirculation control valve. According to the present invention, the exhaust recirculation passage for circulating exhaust gas during normal operation can be shared even during cranking of the internal combustion engine, so that convenience can be increased and costs can be reduced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing an exhaust gas reduction device for an internal combustion engine according to an embodiment of the present invention. In the engine 2, which is an internal combustion engine shown in FIG. 1, a combustion chamber 2a is formed above a piston 2f provided in a cylinder 2e. An ignition plug 3, an intake valve 2b, and an exhaust valve 2c are provided above the combustion chamber 2a. Further, a valve operating mechanism for opening and closing the intake valve 2b and the exhaust valve 2c is provided.
A crank position sensor 14 is provided below the engine 2, and detects the number of rotations and the rotation angle of the crankshaft 2 d using the crank position sensor 14.
[0012]
An intake passage 4 including an intake manifold, a surge tank, and the like is connected to an upstream side of the intake valve 2b. In the middle of the intake passage 4, a throttle valve 12 for adjusting the amount of intake air taken into the combustion chamber 2a is provided. The throttle opening Th of the throttle valve 12 is detected by a throttle opening sensor 16 and input to the ECU 7.
[0013]
An injector 5 that injects fuel into the combustion chamber 2a is provided downstream of the throttle valve 12 in the intake passage 4. A fuel pump (not shown) is connected to the injector 5, and gasoline as fuel is pressurized by the fuel pump and injected from the injector 5. Thus, the fuel is mixed with fresh air (fresh air) 20 supplied through the throttle valve 12.
[0014]
An exhaust passage 6 composed of an exhaust manifold or the like is connected downstream of the exhaust valve 2c. A three-way catalyst (hereinafter, referred to as “catalyst”) 22 for purifying exhaust gas is provided in the exhaust passage 6. An O2 sensor 21 is mounted at an upstream position of the catalyst 22, and detects the oxygen concentration in the exhaust gas by the sensor 21.
[0015]
One end of the EGR passage 8 is connected to a position upstream of the O2 sensor 21 in the exhaust passage 6, and the other end of the EGR passage 8 is connected between the throttle valve 12 and the injector 5 in the intake passage 4. The EGR passage 8 is provided with an EGR valve 9 as an opening / closing means. By opening and closing the EGR valve 9, the circulation and cutoff of the gas in the exhaust passage 6 to the intake passage 4 are controlled.
[0016]
The exhaust gas reduction device according to the present embodiment includes an ECU 7 that is a control device. The ECU 7 controls the entire exhaust gas reduction device, and is mainly configured by a computer including a CPU, a ROM, and a RAM. Various control routines including a gas flow rate control routine are stored in the ROM.
[0017]
The ECU 7 receives detection signals from the water temperature sensor 11 for detecting the cooling water temperature Tw of the engine 2 and the intake air temperature sensor 15 for detecting the intake air temperature Ta, in addition to the above-described throttle opening sensor 16, crank position sensor 14, and O2 sensor 21. Is entered. The ECU 7 is connected to various devices such as the ignition plug 3, the injector 5, the EGR valve 9, and the like. The various devices are connected to the ECU 7 based on detection signals from the above-described sensors in accordance with a program stored in the ROM in advance. Perform control.
[0018]
The operation of the exhaust gas reduction device having the above configuration will be described.
FIG. 2 is a flowchart showing the control of the exhaust gas reduction device. First, when the ignition is turned on, in step S12, the ECU 7 obtains the data (the engine speed Ne, the water temperature Tw, the intake air temperature Ta, and the throttle opening Th) detected by the sensors 11, 14, 15, and 16 respectively. Perform reading.
Then, in a step S14, it is determined whether or not the engine 2 is in a cranking state. In this determination, if the rotation speed detected by the crank position sensor 14 is equal to or lower than the predetermined rotation speed, it is determined that the engine is in a cranking state by rotation by the starter, and if the rotation speed is higher than the predetermined rotation speed, it is determined that the combustion is in the normal driving state. If the determination result in step S14 is YES, the process proceeds to step S16, and if the determination result is NO, the process proceeds to step S24. In step S24, after performing control according to the normal driving state, a series of processes is terminated, but details thereof will be omitted.
[0019]
If it is determined in step S14 that the engine 2 is in the cranking state, the EGR valve 9 is operated to open the EGR passage 8 in step S16, and the unburned gas 19 in the exhaust passage 4 is taken in through the EGR passage 8. Circulate through passage 4. Then, in step S18, an unfueled gas recirculation amount Qrgas is estimated from the engine speed Ne and the throttle opening Th.
[0020]
FIG. 3 is a graph of the throttle opening Th with respect to the engine speed Ne and the unburned gas flow rate Qrgas. In the present embodiment, the graph shown in FIG. 3 is held as a map, and the uncombusted gas flow rate Qrgas is searched for on the map based on the detected engine speed Ne and the throttle opening Th, so that the uncombusted gas flow Qrgas is searched. The combustion gas flow rate Qrgas can be estimated.
[0021]
Then, in step S20, the fuel amount Grfuel in the unburned recirculated gas is estimated. FIG. 4 is a graph showing the relationship between the temperature index obtained from the water temperature Tw and the intake air temperature Ta and the fuel amount Grfuel in the unburned gas recirculated gas. The graph shown in FIG. 4 is also held as a map similarly to FIG. 3, and the fuel amount Grfuel is estimated based on the fuel amount temperature index obtained from the detected water temperature Tw and the intake air temperature Ta.
As shown in the figure, in the case of a low temperature start according to the temperature index, the fuel amount is estimated based on the temperature characteristics corresponding to each of the intermediate temperature zone and the hot restart. Can be finely controlled.
[0022]
Then, in a step S22, a corrected fuel injection amount to be injected from the injector 5 is calculated. That is, the fuel injection amount injected from the injector 5 is subtracted and corrected based on the estimated fuel amount Grfuel. Then, a series of processing ends.
[0023]
By performing such control, the unburned gas can be supplied to the combustion chamber 2a again, and the amount of fuel supplied into the combustion chamber 2a can be adjusted to be an appropriate amount.
[0024]
Further, even in the case of a hot restart in which vaporized fuel is generated in the fuel transport line when the temperature detected by the water temperature sensor 11 and the intake air temperature sensor 15 is equal to or higher than a predetermined value, an appropriate amount of fuel can be injected. , The starting performance can be improved.
[0025]
FIG. 5 is a graph showing the relationship between the engine speed and time when the control of the exhaust gas reduction device is performed and when it is not performed. As shown in the figure, the start time can be reduced to approximately half when control is performed and when control is not performed, and the start performance can be improved.
[0026]
The contents of the present invention are not limited to the contents of the above-described embodiment. For example, in the embodiment, since the EGR passage is shared even during cranking, the convenience can be increased and the cost can be reduced. However, even when the EGR passage is not provided, the intake passage and the exhaust passage can be used. By providing a circulation passage connecting to the passage and performing the above-described control, it is possible to reduce emission of unburned gas while ensuring good startability. Further, an airflow sensor for detecting the amount of intake air in the intake passage 4 is provided, and the unburned gas recirculation amount is estimated in consideration of the air flow rate detected by the airflow sensor, thereby improving the estimation accuracy. Becomes possible.
[0027]
【The invention's effect】
As described above, according to the first aspect of the invention, the unburned gas can be supplied to the combustion chamber again, and the flow rate of the gas supplied to the combustion chamber can be adjusted to an appropriate amount, so that the normal combustion can be quickly performed. Control can be transferred. In addition, when performing hot restart, even when vaporized fuel is generated in the fuel transport line, the starting performance can be improved.
According to the second aspect of the present invention, it is possible to increase convenience and reduce costs.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an exhaust gas reduction device for an internal combustion engine according to an embodiment of the present invention.
FIG. 2 is a flowchart showing control of the exhaust gas reduction device.
FIG. 3 is a graph of throttle opening with respect to cranking speed and unburned gas flow rate.
FIG. 4 is a graph showing a relationship between a temperature index obtained from a water temperature and an intake air temperature and an unburned gas flow rate.
FIG. 5 is a graph showing the relationship between engine speed and time when control of the exhaust gas reduction device is performed and when control is not performed.
[Explanation of symbols]
2 engine (internal combustion engine)
7 Control unit (ECU)
8 EGR passage 9 EGR valve

Claims (2)

A circulation passage connecting the exhaust passage and the intake passage connected to the combustion chamber of the internal combustion engine is provided with opening and closing means for opening and closing the circulation passage,
Determining means for determining whether the internal combustion engine is in a cranking state,
An actuating means for opening the circulation passage by actuating the opening / closing means when it is determined that the cranking state is established by the determining means;
Recirculation amount estimating means for estimating the recirculation amount of the unburned gas recirculated to the circulation passage
Fuel amount estimating means for estimating the fuel amount in the unburned gas from the recirculation amount estimated by the flow rate estimating means;
Control means for correcting the fuel supply amount based on the fuel amount estimated by the fuel amount estimating means. The exhaust gas reduction device for an internal combustion engine according to claim 1, wherein the circulation passage is an exhaust recirculation passage including an exhaust recirculation control valve.

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