JP3666583B2 - Internal combustion engine with a supercharger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine with a supercharger, and more particularly to a technique for discharging moisture that condenses in an intercooler.
[0002]
[Related background]
In diesel engines mounted on buses, trucks, etc., in order to improve output, it is common practice to compress the intake air with a supercharger and cool it with an intercooler to increase the volumetric efficiency in the combustion chamber. Yes.
Also, exhaust gas recirculation (EGR) is generally performed in which a part of exhaust gas is recirculated to the intake system and recombusted with fresh air mainly for the purpose of reducing NOx in the exhaust gas.
[0003]
By the way, a large amount of water is contained as water vapor in the sucked fresh air and the refluxed EGR gas. When the fresh air and the EGR gas are cooled by an intercooler, condensation occurs, and the condensed water is contained in the combustion chamber. There is a problem that a problem such as corrosion of the member occurs due to entering.
Therefore, an apparatus for connecting the intercooler and the exhaust passage with a drain pipe and discharging condensed water in the intercooler to the exhaust passage is disclosed in Japanese Patent Application Laid-Open No. 11-270341. Thereby, the dew condensation water discharged to the exhaust passage is vaporized by the exhaust heat, and is released into the atmosphere as water vapor.
[0004]
[Problems to be solved by the invention]
However, because the exhaust passage is long in buses, trucks, etc., the exhaust pressure is high, and even if it is attempted to discharge condensed water in the intercooler to the exhaust passage, the exhaust gas will drain the drain pipe when the pressure in the intercooler is low. There may be a problem that the condensed water is not sufficiently discharged due to reverse flow.
[0005]
In addition, when trying to obtain a high output, it is necessary to sufficiently increase the pressure of the intake air with a turbocharger. However, if the condensed water is discharged through the drain pipe, the intake air other than the condensed water is discharged at the same time. (Boost missing), the pressure of the intake air is lowered and a sufficient output cannot be obtained, which may cause a deterioration in performance.
The present invention has been made to solve such problems, and the object of the present invention is to provide a supercharger capable of reliably discharging condensed water in the intercooler without deteriorating the performance of the internal combustion engine and without backflow of exhaust gas. It is to provide an internal combustion engine with a machine.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a supercharger, an intercooler that is interposed downstream of the supercharger in an intake passage and cools intake air, an exhaust passage, and the intake air are provided. An EGR passage that connects a portion of the passage upstream of the intercooler, a condensed water drainage passage that connects a lower portion of the intercooler and the exhaust passage, and an on-off valve interposed in the condensed water drainage passage; An operating state detecting means for detecting the operating state of the internal combustion engine, and an operating state in an extremely low output region where the pressure in the intercooler is lower than the pressure in the exhaust passage based on the detection information of the operating state detecting means. On-off valve control means for closing the on-off valve at a certain time and when operating in a high output range is provided.
[0007]
Therefore, when the pressure in the intercooler is in an extremely low output range operation state where the pressure in the exhaust passage is lower than the pressure in the exhaust passage, the on-off valve is closed, and the exhaust gas flows back to the intake system via the condensed water drainage passage. Is prevented.
Also, since the on-off valve is closed even when the engine is in the high output range, intake air is prevented from being discharged and intake pressure is secured when high output is required, preventing a decrease in the output of the internal combustion engine. The
[0008]
In other words, the on-off valve opens only in the medium and low output ranges that are neither the extremely low output range nor the high output range, and the dew condensation water in the intercooler is exhausted well without deteriorating the performance of the internal combustion engine and without backflow of exhaust gas. It is discharged into the passage and evaporates due to exhaust heat.
According to a second aspect of the present invention, the on-off valve control means has an excess air ratio calculating means for calculating an excess air ratio in a current operating state based on information from the operating state detecting means, and the on-off valve control When the excess air ratio calculated by the excess air ratio calculating means is larger than a first excess air ratio as a threshold value of the operating state in the extremely low output range, and when the operating state in the high output range is When the second excess air ratio is smaller than the threshold value, the on-off valve is closed.
[0009]
Therefore, there is a correlation between the output of the internal combustion engine and the excess air ratio, and the excess air ratio is large when the internal combustion engine is operating in the low output range, and the excess air ratio is small when the internal combustion engine is operating in the high output range. By closing the on-off valve when the rate is greater than the first excess air rate as the threshold value of the operating state in the extremely low output range, the backflow of exhaust gas to the intake system is reliably prevented.
[0010]
Further, by closing the on-off valve when the excess air ratio is smaller than the second excess air ratio as a threshold value for the operating state in the high output range, it is preferable to reduce the output of the internal combustion engine when high output is required. To be prevented.
That is, the on-off valve is opened only when the excess air ratio is between the first excess air ratio and the second excess air ratio, that is, in the middle and low output ranges, and the dew condensation water in the intercooler is Thus, the exhaust gas is reliably discharged into the exhaust passage without deteriorating the performance of the internal combustion engine and without backflow of exhaust gas.
[0011]
In the invention of claim 3, the on-off valve control means is configured such that the excess air ratio calculated by the excess air ratio calculating means is smaller than the first excess air ratio and less than the second excess air ratio. When it is larger, the on-off valve is opened for a predetermined period.
Therefore, the on-off valve opens for a predetermined period when the excess air ratio is between the first excess air ratio and the second excess air ratio, that is, in the middle and low output range, and the dew condensation in the intercooler occurs. Water can be sufficiently discharged into the exhaust passage without deteriorating the performance of the internal combustion engine and without backflow of exhaust gas, and intake air is prevented from being discharged more than necessary even in the middle and low output ranges.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an internal combustion engine with a supercharger according to the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of an internal combustion engine with a supercharger according to the present invention, which will be described below with reference to FIG.
[0013]
Here, an in-line four-cylinder diesel engine (hereinafter simply referred to as an engine) is employed as the engine 1.
An intake pipe 4 is connected to an intake port (not shown) of the engine 1 via an intake manifold 2, while an exhaust pipe 8 is connected to an exhaust port (not shown) via an exhaust manifold 6.
[0014]
The intake pipe 4 and the exhaust pipe 8 are provided with a turbocharger (supercharger) 10 having a compressor 12 on the intake pipe 4 side and a turbine 14 on the exhaust pipe 8 side. . The turbocharger 10 enhances volumetric efficiency in the combustion chamber of the engine 1 by compressing intake air.
An intercooler 16 is interposed between the turbocharger 10 of the intake pipe 4 and the intake manifold 2. The intercooler 16 serves to cool the intake air pumped by the turbocharger 10 and further increase the volumetric efficiency in the combustion chamber of the engine 1.
[0015]
An exhaust brake 20 is interposed in the exhaust pipe 8, and an aftertreatment device 22 and a muffler 24 are interposed.
The exhaust brake 20 is a braking device that applies a brake to the engine 1 by closing the valve to increase the exhaust pressure in the exhaust pipe. For example, an electromagnetic butterfly valve that is opened and closed by an actuator (not shown) is employed. ing.
[0016]
The aftertreatment device 22 is an exhaust gas purification comprising a catalytic converter and a diesel particulate filter (DPF) for purifying harmful components (HC, CO, NOx, etc.) and PM (particulate matter) contained in the exhaust gas. The muffler 24 is a silencer.
An EGR passage 30 is branched from a portion downstream of the aftertreatment device 22 of the exhaust pipe 8 to recirculate a part of the exhaust gas (EGR gas) to the intake system, and the tip of the EGR passage 30 is The intake pipe 4 is connected to a portion upstream of the turbocharger 10.
[0017]
The EGR passage 30 is provided with an electromagnetic EGR valve 32 that controls the opening and closing of the EGR passage 30, and further, an EGR cooler 34 for cooling EGR gas to increase volumetric efficiency. ing.
As a result, the EGR valve 32 is opened by the operation of an actuator (not shown), and when the EGR gas is recirculated from the exhaust pipe 8 through the EGR passage 30 to the intake system, the EGR gas is combined with fresh air in the combustion chamber. It is introduced into the gas and combusts, so that the combustion becomes slow and the generation of NOx is suppressed.
[0018]
By the way, in the intercooler 16, the water | moisture content contained in intake air or EGR gas condenses by cooling, and becomes condensed water. Therefore, a reservoir 17 for collecting the condensed water is provided in the intercooler 16, and a condensed water drainage passage 40 extends from the reservoir 17. The tip of the condensed water drainage passage 40 is connected to a portion of the exhaust pipe 8 downstream of the branch with the EGR passage 30.
[0019]
The condensed water drainage passage 40 is provided with an electromagnetic on-off valve 42 that is actuated by an actuator (not shown) to communicate and block the condensed water drainage passage 40.
The electronic controller (ECU) 50 is a control device for performing overall control of the supercharged internal combustion engine including the engine 1 according to the present invention.
[0020]
To the input side of the ECU 50, various sensors for detecting the engine speed and the like provided in the engine 1 are connected, and an accelerator sensor 54 for detecting the operation amount of the accelerator pedal 52 is connected.
On the other hand, the exhaust brake 20, the EGR valve 32, and the opening / closing valve 42 are connected to the output side of the ECU 50.
[0021]
Thus, when an actuation signal is supplied from the ECU 50 to the actuator of the exhaust brake 20, the butterfly valve as the exhaust brake 20 opens and closes, and when the opening signal is supplied to the actuator of the EGR valve 32, the opening of the EGR valve 32 Is adjusted, and the operation signal is supplied to the actuator of the on-off valve 42, the on-off valve 42 opens and closes.
[0022]
The operation of the supercharged internal combustion engine according to the present invention configured as described above, that is, the condensed water drainage control will be described below.
As described above, in the intercooler 16, moisture contained in the intake air or EGR gas condenses by cooling and accumulates as condensed water. The condensed water is supplied to the exhaust pipe 8 through the condensed water drainage passage 40. When draining, when condensed water is always discharged, the condensed water in the case where the exhaust pressure in the exhaust pipe 8 is higher than the intake pressure in the intercooler 16 as in idle operation, for example. However, even if it is desired to obtain a high output, the intake pressure does not increase due to the boost loss, that is, the volumetric efficiency in the combustion chamber is reduced. There is a problem that the desired output cannot be obtained due to insufficient increase.
[0023]
Therefore, in the present invention, the timing for draining condensed water is limited to the minimum necessary.
Referring to FIG. 2, the relationship between the pressure in the intercooler 16 (solid line) and the pressure in the exhaust pipe 8 (broken line) and the excess air ratio λ is shown. The valve 42 is controlled to open and close (open / close valve control means), which will be described below with reference to FIG.
[0024]
Here, the reason why the excess air ratio λ is used as a parameter for the opening / closing control of the on-off valve 42 is that the correlation between the output of the engine 1 and the excess air ratio λ is high.
The excess air ratio λ is determined based on the fuel injection amount Q, the engine rotational speed Ne, the EGR amount, and the like. Specifically, the accelerator opening information from the accelerator sensor 54, the engine rotational speed information Ne from the engine 1, It is obtained by calculation from the opening degree command value of the EGR valve 32 or the like. Actually, these are mapped in advance, and the excess air ratio λ is read from the map (operating state detection means, excess air ratio calculation means).
[0025]
Here, for example, the value λ1 (first excess air ratio) is set as the threshold value for the operating state in the extremely low output range, and the value λ2 (second excess air ratio) is set as the threshold value for the operating state in the high output range. Is set.
When the excess air ratio λ is larger than the value λ1 (A range), the on-off valve 42 is closed. That is, the open / close valve 42 is closed when the engine 1 is in the extremely low output region and the pressure in the exhaust pipe 8 is higher than the pressure in the intercooler 16 as in idle operation. This reliably prevents the exhaust gas from flowing backward to the intake system side.
[0026]
Also, when the excess air ratio λ is smaller than the value λ2 (C region), the on-off valve 42 is closed. That is, when the engine 1 is in the high output range, the on-off valve 42 is closed. As a result, the loss of boost is prevented, and a decrease in the output of the engine 1 is preferably prevented.
On the other hand, when the excess air ratio λ is between the values λ1 and λ2 (B region), the on-off valve 42 is opened. That is, the on-off valve 42 is opened only when the engine 1 is in the middle / low output range, and condensed water is discharged.
[0027]
Preferably, when the excess air ratio λ is between the values λ1 and λ2, the on-off valve 42 is opened for a predetermined time (several seconds). This prevents the intake air from being discharged more than necessary while sufficiently discharging condensed water.
Therefore, in the internal combustion engine with a supercharger of the present invention, the dew condensation water in the intercooler 16 can be discharged to the exhaust pipe 8 well without deteriorating the performance of the engine 1 and backflow of the exhaust gas to the intake system. Water can be vaporized well by exhaust heat. Thereby, it is possible to prevent the occurrence of corrosion mainly in the piston, cylinder wall, intercooler and the like of the engine 1.
[0028]
Since the EGR gas contains more water than normal fresh air, the on-off valve 42 is periodically opened when EGR is performed as much as possible even in the middle and low output range (B region). Is good. Specifically, since EGR tends to be performed in a low output region (a region closer to the A region in the B region), the on-off valve 42 may be opened when the excess air ratio λ is in the region. Good.
[0029]
【The invention's effect】
As described above in detail, according to the supercharged internal combustion engine of claim 1 of the present invention, when the pressure in the intercooler is in the operating state in the extremely low output range lower than the pressure in the exhaust passage. Since the on-off valve is closed, the exhaust gas can be prevented from flowing back to the intake system via the condensed water drainage passage, and the on-off valve is closed even when operating in the high output range. When this is necessary, the intake air can be prevented from being discharged and the intake pressure can be secured, and the output of the internal combustion engine can be prevented from decreasing.
[0030]
Therefore, the on-off valve can be opened only in the medium to low output range that is neither the extremely low output range nor the high output range, and the dew condensation in the intercooler can be exhausted well without deteriorating the performance of the internal combustion engine and without backflow of exhaust gas. And can be evaporated by exhaust heat.
Further, according to the internal combustion engine with a supercharger according to claim 2, the output of the internal combustion engine and the excess air ratio are correlated, and the excess air ratio is large when the internal combustion engine is operating in a low output range. Since the excess air ratio is small in the operating state of FIG. 5, the on-off valve is closed when the excess air ratio is larger than the first excess air ratio as the threshold value of the operating state in the extremely low output region, thereby Backflow to the system can be reliably prevented, and high output is required by closing the open / close valve when the excess air ratio is smaller than the second excess air ratio as the threshold value of the operating state in the high power range It is possible to suitably prevent a decrease in the output of the internal combustion engine at that time.
[0031]
Therefore, when the excess air ratio is between the first excess air ratio and the second excess air ratio, that is, only in the middle and low output ranges, the on-off valve can be opened, and the dew condensation water in the intercooler is reduced. The exhaust gas can be reliably discharged into the exhaust passage without deteriorating the performance of the internal combustion engine and without backflow of exhaust gas.
Further, according to the internal combustion engine with a supercharger according to claim 3, when the excess air ratio is between the first excess air ratio and the second excess air ratio, that is, in the middle and low output range, it opens and closes for a predetermined period. Since the valve is opened, the dew condensation water in the intercooler can be sufficiently discharged to the exhaust passage without deteriorating the performance of the internal combustion engine and the backflow of the exhaust gas, and the intake air is discharged more than necessary even in the middle and low output ranges. This can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a supercharged internal combustion engine according to the present invention.
FIG. 2 is a diagram illustrating a relationship among an intercooler internal pressure, an exhaust pipe internal pressure, and an excess air ratio λ, and is a diagram for explaining open / close control of an open / close valve.
[Explanation of symbols]
1 Diesel engine 4 Intake pipe 8 Exhaust pipe 10 Turbocharger (supercharger)
16 Intercooler 30 EGR passage 32 EGR valve 40 Condensed water drain passage 42 On-off valve 50 Electronic controller (ECU)
54 Accelerator sensor

Claims (3)

A turbocharger,
An intercooler that is interposed downstream of the supercharger in the intake passage and cools the intake air;
An EGR passage connecting an exhaust passage and a portion of the intake passage upstream of the intercooler;
A condensed water drainage passage connecting the lower portion of the intercooler and the exhaust passage;
An on-off valve interposed in the condensed water drainage passage;
An operating state detecting means for detecting an operating state of the internal combustion engine;
Based on the detection information of the operation state detection means, when the pressure in the intercooler is in an extremely low output region operation state lower than the pressure in the exhaust passage, and when in a high output region operation state, On-off valve control means for closing the on-off valve;
An internal combustion engine equipped with a supercharger. The on-off valve control means has an excess air ratio calculation means for calculating an excess air ratio in the current operation state based on information from the operation state detection means,
The on-off valve control means is configured such that when the excess air ratio calculated by the excess air ratio calculating means is larger than a first excess air ratio as a threshold value of the operating state in the extremely low output range, and the high output range. 2. The supercharged internal combustion engine according to claim 1, wherein the on-off valve is closed when the air excess ratio is smaller than a second excess air ratio as a threshold value of the operating state. The opening / closing valve control means sets the opening / closing valve for a predetermined period when the excess air ratio calculated by the excess air ratio calculating means is smaller than the first excess air ratio and greater than the second excess air ratio. The internal combustion engine with a supercharger according to claim 2, wherein the internal combustion engine is opened over a wide range.

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