JP2001159361A - White smoke exhaust restraining device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the exhaust of white smoke into the atmosphere in the wide operating state range of an engine. SOLUTION: This white smoke exhaust restraining device for an internal combustion engine is provided with an exhaust circulation passage for recirculating exhaust gas exhausted from an engine body, to a combustion chamber, and a cooling means for cooling the exhaust gas flowing in the exhaust circulation passage. Preliminary injection for injecting a small quantity of residual fuel is executed prior to the execution of main injection for injecting the greater part of fuel to be injected into the combustion chamber. An oxidation catalyst is disposed in the exhaust passage. When the temperature of intake air is a first predetermined temperature or higher, exhaust gas is recirculated to the combustion chamber, by-passing the cooling means. When the temperature of intake air is the first predetermined temperature or lower, time between the execution timing of the preliminary injection and the execution timing of the main injection is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for suppressing white smoke emission of an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, particularly in a diesel engine, a technique of recirculating exhaust gas to a combustion chamber is used to suppress generation of nitrogen oxides (NOx). Further, the exhaust gas is cooled and recirculated to the combustion chamber in order to maximize the amount of the exhaust gas recirculated to the combustion chamber. However, when the exhaust gas thus cooled is recirculated to the combustion chamber, the temperature in the combustion chamber becomes relatively low. For this reason, in some cases, the combustion of the fuel in the combustion chamber becomes poor, and white smoke is generated.

[0003] In Japanese Patent Application Laid-Open No. H11-117815, the temperature of the exhaust gas recirculated to the combustion chamber is controlled in accordance with the operating state of the engine. Specifically, the exhaust gas is recirculated to the combustion chamber by bypassing a cooler for cooling the exhaust gas, the temperature in the combustion chamber is maintained relatively high, and the generation of white smoke is suppressed.

[0004]

However, some white smoke is generated even by the method disclosed in the above publication. Even if white smoke is not generated, if the idling operation continues for a relatively long time, the temperature of the engine body becomes extremely low, so simply bypassing the cooler with the exhaust gas keeps the temperature in the combustion chamber relatively high No, white smoke is generated. Of course, in the above publication, the exhaust gas can be heated by a heater, but this increases the manufacturing cost due to the provision of the heater.

As described above, the method disclosed in the above publication cannot completely suppress the emission of white smoke to the atmosphere. Even if it is possible, it is necessary that the operating condition of the engine satisfy certain conditions. If the operation state does not satisfy certain conditions, if it is desired to completely suppress the emission of white smoke to the atmosphere, additional means will be required and the production cost will increase. An object of the present invention is to suppress the emission of white smoke into the atmosphere in a wide range of engine operating conditions.

[0006]

According to a first aspect of the present invention, there is provided an exhaust circulation passage for recirculating exhaust gas discharged from an engine body to a combustion chamber, and the exhaust circulation passage. Cooling means for cooling the exhaust gas flowing therethrough, and a reserve for injecting the remaining small amount of fuel before executing the main injection for injecting most of the fuel to be injected into the combustion chamber. In an internal combustion engine that performs a specific injection, an oxidation catalyst is disposed in an exhaust passage, and when the temperature of intake air is equal to or higher than a predetermined first temperature, the exhaust gas bypasses the cooling means and burns. When the temperature of the intake air is lower than or equal to the predetermined first temperature, the time between the timing of executing the preliminary injection and the timing of executing the main injection is shortened.

According to a second aspect of the present invention, in the first aspect, when the temperature of the intake air is equal to or lower than a second predetermined temperature lower than the first predetermined temperature, the opening timing of the intake valve is set. Delay. According to the third invention, an exhaust gas circulation passage for recirculating exhaust gas discharged from the engine body to the combustion chamber, and a cooling means for cooling exhaust gas flowing in the exhaust gas circulation passage are provided. In the internal combustion engine, an oxidation catalyst is arranged in the exhaust passage, and when the temperature of the intake air is equal to or higher than a predetermined first temperature, the exhaust gas is recirculated to the combustion chamber by bypassing the cooling means, and When the temperature is equal to or lower than the predetermined first temperature, the opening timing of the intake valve is delayed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. First, an internal combustion engine to which the white smoke emission control device of the present invention is applied will be described. The internal combustion engine shown in FIG.
It is a stroke compression ignition type internal combustion engine, that is, a diesel engine. Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, and 9 is Exhaust valves 10 and 10 respectively indicate exhaust ports. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11. Surge tank 1
2 is connected to a supercharger, for example, an outlet of a compressor 16 of an exhaust turbocharger 15 via an intake duct 13 and an intercooler 14. An inlet of the compressor 16 is connected to an air cleaner 18 via an intake pipe 17. A throttle valve 20 driven by a step motor 19 is arranged in the intake pipe 17. A mass flow detector 21 for detecting the mass flow of the intake air is disposed in the intake pipe 17 upstream of the throttle valve 20.

On the other hand, the exhaust port 10 is connected to the exhaust manifold 2.
The exhaust turbine 2 of the exhaust turbocharger 15 via the
3 is connected to the entrance. An outlet of the exhaust turbine 23 is connected via an exhaust pipe 24 to a catalytic converter 26 having a built-in catalyst 25 having an oxidizing function. The catalyst in this embodiment is a three-way catalyst. An air-fuel ratio sensor 27 is disposed in the exhaust manifold 22. Further, a temperature sensor 28 for detecting the temperature of the exhaust gas is disposed in the exhaust pipe 24 downstream of the catalytic converter 26.

The exhaust pipe 22 connected to the outlet of the catalytic converter 26 and the intake pipe 17 downstream of the throttle valve 20 are connected to each other through an exhaust gas recirculation (hereinafter, EGR) passage 29. In the EGR passage 29, an EGR passage 29 is provided.
An intercooler 32 is arranged as cooling means for cooling the EGR gas flowing inside. In this embodiment, the engine cooling water is guided into the intercooler 32, and the engine cooling water cools the EGR gas. Further, an EGR control valve 30 for controlling the amount of exhaust gas recirculated to the intake pipe 17 is disposed in the EGR passage 29. Further, a bypass passage 31 that bypasses the intercooler 32 is connected to the EGR passage 29. According to the bypass passage 31, the exhaust gas is recirculated to the intake pipe 17 without passing through the intercooler 32. Further, a bypass control valve 37 for controlling the amount of exhaust gas to be bypassed is disposed in the bypass passage 31.

The fuel injection valve 6 is connected via a fuel supply pipe 33 to a fuel reservoir, that is, a so-called common rail 34. Fuel is supplied into the common rail 34 from an electrically controlled fuel pump 35 with a variable discharge amount. The fuel supplied into the common rail 34 is supplied to the fuel injection valve 6 via each fuel supply pipe 33. A fuel pressure sensor 36 for detecting the fuel pressure in the common rail 34 is attached to the common rail 34. Based on an output signal of the fuel pressure sensor 36, a fuel pump is provided so that the fuel pressure in the common rail 34 becomes a target fuel pressure. 35 is controlled.

The electronic control unit 40 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a CPU (Microprocessor) 44, an input port 45, An output port 46 is provided. The output signal of the mass flow detector 21 is input to the input port 45 via the corresponding AD converter 47, and the output signals of the air-fuel ratio sensor 27, the temperature sensor 28, and the fuel pressure sensor 36 are also output to the corresponding AD converter 47, respectively. The input is input to the input port 45 via the input port 45. A load sensor 51 that generates an output voltage proportional to the depression amount L of the accelerator pedal 50 is connected to the accelerator pedal 50. The output voltage of the load sensor 51 is input to the input port 45 via the corresponding AD converter 47. The input port 45 is connected to a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, by 30 °. Output port 46
The fuel injection valve 6, throttle valve control step motor 19, EGR control valve 30,
It is connected to a fuel pump 35 and a bypass control valve 37.

Next, a description will be given of a white smoke emission suppressing apparatus according to this embodiment. A main object of the present invention is to suppress the emission of white smoke into the atmosphere. The first solution that can be taken to achieve this purpose is to suppress the generation of white smoke in the combustion chamber itself, and the second solution is to release the white smoke generated in the combustion chamber to the atmosphere Before is to purify this white smoke.

In order to suppress the generation of white smoke itself based on the first solution, the temperature in the combustion chamber may be kept relatively high. This is because if the temperature in the combustion chamber is relatively low, white smoke is likely to be generated. Therefore, in this embodiment, the following three means are selectively adopted according to the engine state as described later, and the temperature in the combustion chamber is kept relatively high. In the first means, the exhaust gas is recirculated into the combustion chamber by bypassing the intercooler. According to this, since the exhaust gas is not cooled by the intercooler, the exhaust gas having a relatively high temperature is recirculated into the combustion chamber. Therefore, the temperature in the combustion chamber is maintained relatively high.

In the second means, a timing for executing a fuel injection for injecting most of the fuel to be injected into the combustion chamber (hereinafter referred to as a main fuel injection), and a remaining small amount of the fuel prior to the main fuel injection. The interval between the timing at which fuel injection for preliminary injection (hereinafter referred to as “preliminary fuel injection”) is performed is reduced. According to this, as soon as the fuel injected by the preliminary fuel injection ignites, the fuel injected by the main fuel injection ignites, so that the combustion temperature increases. Therefore, the temperature in the combustion chamber is maintained relatively high.

In the third means, the timing for opening the intake valve is made later than the normal valve opening timing. According to this, the intake valve is opened when the negative pressure in the combustion chamber becomes relatively large. This large negative pressure causes the intake air to be rapidly sucked into the combustion chamber, thereby increasing the temperature of the intake air. Therefore, the temperature in the combustion chamber is maintained relatively high.

As will be described later, these three means are selectively employed in accordance with the state of the engine to suppress the generation of white smoke in the combustion chamber. Further, in order to purify the white smoke generated in the combustion chamber before being discharged to the atmosphere based on the second solution, a catalyst disposed in an exhaust pipe may be used. As described above, in the present embodiment, the emission of white smoke to the atmosphere is suppressed as a whole by selectively adopting the above three means in accordance with the state of the engine on the assumption that a catalyst is used. Next, a description will be given of which of the above three means is adopted under what conditions.

When deciding which of the above three means to adopt, it is necessary to take into account that each means has advantages and disadvantages. Means for recirculating the first exhaust gas into the combustion chamber by bypassing the intercooler can suppress the generation of white smoke in the combustion chamber when the temperature of the intake air is relatively high (see the solid line BY in FIG. 2). Further, there is an advantage that fuel efficiency is not deteriorated (see the solid line BY in FIG. 3C). However, if the temperature of the intake air is relatively low, there is a disadvantage that the effect of suppressing the generation of white smoke in the combustion chamber is reduced (see the solid line BY in FIG. 2). Also, the means for shortening the interval between the execution of the second preliminary fuel injection and the main fuel injection suppresses the generation of white smoke in the combustion chamber even if the temperature of the intake air is lower than the temperature at which the first means is effective. There is a merit that the fuel consumption is not deteriorated (solid line PI in FIG. 2) and the fuel consumption is not deteriorated (solid line PI in FIG. 3B), but white smoke is generated in the combustion chamber when the temperature of the intake air is relatively low. There is a demerit that the effect of suppressing is reduced (solid line PI in FIG. 2). Further, the means for delaying the opening timing of the third intake valve can suppress the generation of white smoke in the combustion chamber even if the temperature of the intake air is lower than the temperature at which the second means is effective (solid line OT in FIG. 2). However, there is a demerit that the pumping loss of the piston is increased and fuel efficiency is deteriorated (see the solid line OT in FIG. 3A).

Considering each means as described above, when the temperature of the intake air is relatively high, the first means or the second means with less deterioration in fuel efficiency is adopted, and when the temperature of the intake air becomes relatively low, the first means or the second means is adopted. It is concluded that it is preferable to employ three means. Now, which of the first means and the second means should be adopted and under what conditions will be described.
As described above, in this embodiment, the white smoke can be purified using the catalyst before the white smoke is released to the atmosphere. Incidentally, the catalyst can also purify other substances that should not be discharged to the atmosphere, for example, carbon monoxide and nitrogen oxides, and it is preferable to purify these substances. In order to purify white smoke and other substances, it is necessary to maintain the temperature of the catalyst above its activation temperature. One means of maintaining the temperature of the catalyst above its activation temperature is to supply a small amount of unburned hydrocarbon to the catalyst. This is because unburned hydrocarbons supplied to the catalyst are purified by combustion with the catalyst, but at this time, heat of combustion is generated. In view of this, it is preferable to preferentially employ the first means for generating a small amount of white smoke, that is, unburned hydrocarbons in the combustion chamber, in order to satisfactorily purify white smoke and other substances.

As described above, in this embodiment, the first means is employed when the temperature of the intake air is relatively high, and the second means is employed when the temperature of the intake air is low. When this happens, the third means is adopted. Thus, the emission of white smoke to the atmosphere can be suppressed over a wide range of engine operating conditions, and the emission of substances that should not be emitted to the atmosphere can be suppressed.

Next, the specific control of the white smoke emission prevention device of the present embodiment will be described with reference to FIG. In FIG. 4, (A) is the temperature of the intake air, (B) is the open / closed state of the EGR control valve, (C) is the open / closed state of the bypass control valve, and (D)
Indicates the interval between the preliminary fuel injection and the main fuel injection (hereinafter, injection interval), (E) indicates the valve opening timing of the intake valve, and (F) indicates the amount of white smoke generated in the combustion chamber. The temperature of the intake air is estimated from the output of the temperature sensor 28.

When the temperature of the intake air is equal to or higher than the predetermined first temperature T1, the EGR control valve 30 is closed and the bypass control valve 37 is opened. At this time, the injection interval is a normal interval, and the opening timing of the intake valve 7 is also a normal timing. As a result, the amount of white smoke generated in the combustion chamber 5 is kept relatively small. This small amount of white smoke flows into the catalyst 25 arranged downstream of the combustion chamber 5,
The catalyst 25 is purified by combustion and serves to maintain the temperature of the catalyst 25 at or above its activation temperature. According to this, the emission of white smoke to the atmosphere is well suppressed and other substances that should not be emitted to the atmosphere are removed from the catalyst 25.
Can be purified.

As the temperature of the intake air gradually decreases, the amount of white smoke generated in the combustion chamber 5 gradually increases. In this embodiment, when the temperature of the intake air becomes equal to or lower than the first temperature T1, the degree of opening of the bypass control valve 37 is gradually reduced as the temperature of the intake air decreases with the EGR control valve 30 closed. And the injection interval is shortened. The opening timing of the intake valve 7 is normally maintained. As a result, the amount of white smoke generated in the combustion chamber 5 becomes substantially zero. The degree of opening of the EGR control valve 30 may be increased as the temperature of the intake air becomes lower when the temperature of the intake air becomes equal to or lower than the first temperature T1.

When the temperature of the intake air further decreases, white smoke generated in the combustion chamber 5 gradually increases again. In the present embodiment, when the temperature of the intake air becomes equal to or lower than the second predetermined temperature T2 lower than the first temperature T1, the degree of opening of the bypass control valve 37 is changed to the present degree with the EGR control valve 30 closed. The valve opening degree is maintained and the injection interval is also maintained at the current interval. Then, the opening timing of the intake valve 7 is delayed. As a result, the amount of white smoke generated in the combustion chamber 5 becomes substantially zero.

In the above embodiment, whether or not to open the bypass control valve 37 is determined on the basis of the temperature of the intake air. However, since the temperature of the intake air greatly depends on the operating state of the internal combustion engine, FIG. May be determined based on the relationship between the engine speed Ne and the output torque T as to whether or not to open the bypass control valve 37. Note that in FIG.
Is a region where the bypass control valve 37 should be opened, and the region Y
Is a region where the bypass control valve 37 is closed and the EGR control valve 30 is opened, and a region Z is a region where the bypass control valve 37 and the EGR control valve 30 are closed. FIG.
When the map is adopted, the boundary between the region X and the region Y may be changed according to the temperature of the intake air.
Specifically, the boundary is changed such that the higher the temperature of the intake air, the wider the range of the region X.

[0026]

According to the first to third aspects of the present invention, when the temperature of the intake air is higher than the first temperature, the exhaust gas is introduced into the combustion chamber without cooling, so that the temperature in the combustion chamber is relatively high. Will be maintained. Therefore, the amount of white smoke generated in the combustion chamber is extremely small. This small amount of white smoke flows into the catalyst and is purified by the catalyst. Therefore, emission of white smoke to the atmosphere is favorably suppressed. Further, since the temperature of the catalyst is maintained at or above its activation temperature by the white smoke flowing into the catalyst, that is, the unburned hydrocarbon, the purifying action of the catalyst is maintained at a high level.

On the other hand, when the temperature of the intake air falls below the first temperature, the amount of white smoke generated in the combustion chamber increases even if the exhaust gas is introduced into the combustion chamber without cooling. However, at this time, according to the first and second inventions, the interval between the preliminary fuel injection and the main fuel injection is shortened. For this reason, since the temperature in the combustion chamber is maintained relatively high, the amount of white smoke generated in the combustion chamber is extremely small. Therefore, emission of white smoke to the atmosphere is suppressed. Further, according to the third aspect, the opening timing of the intake valve is delayed, so that the amount of white smoke generated in the combustion chamber is extremely small. Therefore, emission of white smoke to the atmosphere is suppressed.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine to which a white smoke emission control device of the present invention is applied.

FIG. 2 is a diagram showing the relationship between the temperature of intake air and the amount of white smoke generated in a combustion chamber.

FIG. 3A shows a relationship between the temperature of the intake air and the fuel efficiency when a process of delaying the opening timing of the intake valve is performed,
(B) shows the relationship between the temperature of the intake air and the fuel efficiency when the processing is performed with the interval between the preliminary fuel injection and the main fuel injection shortened, and (C) shows the processing for bypassing the exhaust gas to the intercooler. FIG. 8 is a diagram showing a relationship between the temperature of the intake air and the fuel efficiency in a case where the temperature is changed.

FIG. 4 is a diagram showing a relationship between intake air temperature, an EGR control valve, a bypass control valve, an interval between preliminary fuel injection and main fuel injection, and control of an intake valve opening timing.

FIG. 5 shows E based on the relationship between the engine speed and the output torque.
It is a figure showing control of a GR control valve and a bypass control valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 5 ... Combustion chamber 6 ... Fuel injection valve 7 ... Intake valve 17 ... Intake pipe 25 ... Catalyst 28 ... Temperature sensor 29 ... EGR passage 30 ... EGR control valve 31 ... Bypass passage 37 ... Bypass control valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 301 F02D 45/00 301F 360 360F F02M 25/07 550 F02M 25/07 550A 570 570J 580 580E F Term (reference) 3G062 AA01 AA05 BA04 BA05 BA09 EA10 ED08 ED09 ED11 GA01 GA04 GA09 GA12 GA17 3G084 AA01 BA08 BA13 BA15 BA20 BA23 BA24 DA10 FA02 FA07 FA10 FA27 FA29 FA38 3G091 AA10 AA11 AA18 AB03 CB03 EA03 CB03 EA02 HB06 3G092 AA02 AA11 AA17 AA18 BB06 BB13 DA01 DC03 DC08 EA04 EA17 EC01 FA15 HA01Z HA04Z HB03X HB03Z HD01Z HD05Z HE03Z HF08Z 3G301 HA02 HA11 HA13 HA19 JA21 LA00 LA03 LA07 MA18 MA23 MA23Z10ZP03 PD03

Claims (3)

[Claims] An exhaust circulation passage for recirculating exhaust gas discharged from an engine body to a combustion chamber, and cooling means for cooling exhaust gas flowing in the exhaust circulation passage, wherein the combustion chamber includes: In an internal combustion engine in which a preliminary injection for injecting the remaining small amount of fuel is executed before executing a main injection for injecting most of the fuel to be injected into the exhaust passage, an oxidation catalyst is provided in the exhaust passage. When the temperature of the intake air is equal to or higher than the predetermined first temperature, the exhaust gas is recirculated to the combustion chamber by bypassing the cooling means, and the temperature of the intake air is set to the predetermined first temperature. An apparatus for suppressing white smoke emission of an internal combustion engine, wherein a time between a time when a preliminary injection is executed and a time when a main injection is executed is shortened when the temperature is equal to or lower than a temperature. 2. The system according to claim 1, wherein when the temperature of the intake air is equal to or lower than a predetermined second temperature lower than the predetermined first temperature, the opening timing of the intake valve is delayed.
The white smoke emission control device for an internal combustion engine according to claim 1. 3. An internal combustion engine comprising: an exhaust circulation passage for recirculating exhaust gas discharged from an engine body to a combustion chamber; and cooling means for cooling exhaust gas flowing in the exhaust circulation passage. , Place an oxidation catalyst in the exhaust passage,
When the temperature of the intake air is equal to or higher than the predetermined first temperature, the exhaust gas is recirculated to the combustion chamber by bypassing the cooling means, and the temperature of the intake air is equal to or lower than the predetermined first temperature. A white smoke emission suppression device for an internal combustion engine that sometimes delays the opening timing of an intake valve.