JP2004124824A - Secondary air supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary air supply device capable of preventing cooling of an exhaust port of an internal combustion engine with the secondary air by starting the supply of the secondary air after completion of warming-up the exhaust port. <P>SOLUTION: When the supply of the secondary air is started after the completion of the warming-up of the exhaust port, the warming-up of the exhaust port based on surface or the like of the exhaust port is determined. The secondary air supply device comprises a secondary air supply path for supplying the secondary air to the upstream side of an exhaust emission control device arranged in an exhaust system of the internal combustion engine, and an opening/closing means for opening and closing the secondary air supply path. A means for presuming the temperature of the exhaust port which supplies the secondary air is provided. The temperature of the exhaust port inhibits the secondary air from being supplied until the predetermined temperature or more is reached, and the exhaust port controls cooling by the secondary air. The supply of the secondary air is started after completion of the warming-up of the exhaust port, thus effectively promoting afterburning by the secondary air supply. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a secondary air supply device for supplying secondary air upstream of an exhaust gas purification device provided in an exhaust system of an internal combustion engine.
[0002]
[Prior art]
After combusting the air-fuel mixture, the internal combustion engine discharges the exhaust gas from the cylinder to an exhaust port and an exhaust muffler side. An exhaust gas purification device is disposed in an exhaust path, so that carbon monoxide (CO) in the exhaust gas, Harmful components such as hydrocarbons (HC) and nitrogen oxides (NOx) are purified. Such an exhaust gas purifying device usually exhibits its purifying ability in a predetermined temperature range.
[0003]
Therefore, when the temperature of the exhaust gas purification device is low, fresh air is introduced into the exhaust port side to re-burn CO and HC contained in the exhaust gas to promote the activation of the exhaust gas purification device, and to reduce CO, HC and BACKGROUND ART A secondary air supply device for reducing a NOx emission level is known.
Therefore, fresh air is introduced into the exhaust port only when the internal combustion engine temperature is lower than the predetermined temperature, and when the internal combustion engine is higher than the predetermined temperature and is in a warm-up operation state, the exhaust port is connected to the exhaust port. There is one that blocks the introduction of fresh air (for example, see Patent Document 1)
As described above, conventionally, immediately after the start of the internal combustion engine, the secondary air is supplied to the exhaust port by the secondary air supply device, and the fuel injection amount is made richer than the stoichiometric air-fuel ratio. It was warming up.
[0004]
[Patent Document 1]
JP-A-11-62564
[Problems to be solved by the invention]
However, depending on the condition of the internal combustion engine, if the secondary air is supplied immediately after the start of the internal combustion engine, the afterburning reaction of CO and HC in the exhaust gas, that is, the reburning is not performed because the temperature of the secondary air is low. On the contrary, the exhaust port is cooled by the low-temperature secondary air, and the low-temperature air and exhaust gas are sent to the exhaust gas purification device, so that the warm-up of the exhaust gas purification device is delayed and unburned fuel is discharged to the atmosphere. May occur.
[0006]
Such a situation occurs because the temperature of the exhaust port to which the secondary air is supplied is not sufficiently increased immediately after the start of the internal combustion engine, and is still low enough to cause the afterburning reaction as described above. Due to the state. That is, the inventor of the present invention focused on the fact that it is necessary to warm up the exhaust port and the like and to warm up the surrounding air to some extent in order to efficiently exert the secondary air supply from the start. Is completed.
[0007]
The present invention provides a secondary air supply device capable of suppressing the cooling of the exhaust port with the secondary air by starting the supply of the secondary air after the warm-up of the exhaust port of the internal combustion engine is completed. It is a technical task to provide
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention starts the supply of the secondary air after completing the warm-up of the exhaust port, and at that time, makes a warm-up determination of the exhaust port based on the surface area of the exhaust port and the like. And has the following configuration.
[0009]
That is, a secondary air supply including a secondary air supply passage for supplying secondary air upstream of an exhaust gas purification device installed in an exhaust system of an internal combustion engine, and opening / closing means for opening and closing the secondary air supply passage In the device,
A means for estimating the temperature of the exhaust port to which the secondary air is supplied is provided, and the supply of the secondary air is prohibited until the temperature of the exhaust port exceeds a predetermined temperature, and the exhaust port is cooled by the secondary air. It is characterized in that it is suppressed.
[0010]
The means for estimating the temperature of the exhaust port is at least one of an integrated intake air amount from the start of the internal combustion engine, an integrated injection amount of the fuel injection amount from the start of the internal combustion engine, and an engine water temperature. In consideration of the above and the surface area of the exhaust port, the warm-up state of the exhaust port can be estimated, and the supply timing of the secondary air can be determined.
[0011]
Specifically, when it is determined that the value obtained by dividing the integrated intake air amount from the start of the internal combustion engine by the surface area of the exhaust port is larger than a predetermined reference value, the supply of the secondary air is started. You may make it.
[0012]
Further, when it is determined that the value obtained by dividing the integrated fuel injection amount from the start of the internal combustion engine by the surface area of the exhaust port is larger than a predetermined reference value, the supply of the secondary air is started. Can be.
[0013]
As described above, when the integrated air amount and / or the integrated fuel injection amount from the start of the internal combustion engine reaches a predetermined amount, it is considered that the temperature of the exhaust port has risen to the predetermined temperature, and this is considered as the exhaust port temperature. By dividing by the surface area, a value indicating the warm-up state is obtained. If this value is larger than a predetermined reference value, it is possible to determine that the exhaust port has been warmed up and start supplying the secondary air.
[0014]
According to the present invention, since the supply of the secondary air is started after the exhaust port has been warmed up, the afterburning due to the secondary air supply is effectively promoted, and the desired catalyst warming-up effect is reliably exhibited. can do.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the secondary air supply device of the present invention will be described in more detail with reference to the embodiments shown in FIGS. 1 to 5.
[0016]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and a secondary air supply device thereof according to the present embodiment.
[0017]
The internal combustion engine 1 is a four-cycle gasoline engine having four cylinders 30. Above the piston of each cylinder 30, a combustion chamber surrounded by the top surface of the piston and the wall surface of the cylinder head 1a is formed. I have. Further, an intake system 40, an exhaust system 50, and a secondary air supply system 60 are provided.
[0018]
In the intake system 40, a throttle valve 42 is provided in an intake pipe 41 connected to each intake branch pipe 26, and the intake pipe 41 is connected to an air filter 43. An air flow meter 44 for measuring an intake air amount is provided between the air filter 43 and the throttle valve 42.
[0019]
The exhaust system 50 is provided with an exhaust pipe 54 which is a passage for exhaust gas discharged from each combustion chamber. From an upstream to a downstream of the exhaust pipe 54, an exhaust valve 51, an exhaust port 53, an exhaust branch pipe 52, and an exhaust pipe 54 are formed. They are connected sequentially.
[0020]
The exhaust pipe 54 is provided with an exhaust gas purification device 5, and its casing has a function of purifying hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. A three-way catalyst is provided.
[0021]
The secondary air supply system 60 is configured to supply air taken in from outside the internal combustion engine 1 to each exhaust branch pipe 52 as secondary air.
[0022]
On the secondary air supply passage 61, an air pump 13, a switching valve 62, and a reed valve 63 as a check valve are arranged from the upstream side. Further, a pressure sensor 64 is provided between the air pump 13 and the air switching valve 62. A pipe 65 extending from the intake pipe 41 downstream of the throttle valve 42 is connected to the air switching valve 62. The pipe 65 is provided with an electromagnetic valve 66.
[0023]
The air pump 13 is driven by an electric motor. The air pump 13 includes a motor unit that is driven to rotate based on an external instruction, and a pump unit that is driven to rotate by the motor unit and pressurizes sucked air. . Then, air is sucked from the middle of the intake pipe 41 (upstream of the throttle valve and downstream of the air cleaner) through the air introduction passage 14. Air pumped from the air pump 13 is supplied to the exhaust branch pipe 52 through the secondary passage supply pipe 61 and the distribution pipe 67 branched from the supply pipe 61.
[0024]
Such a secondary air supply device mainly opens the solenoid valve 66 in a state where the fuel concentration is high, the air-fuel ratio is low, and the exhaust gas purification device has not reached the activation temperature, for example, during a cold start. Then, the negative pressure in the intake pipe 41 is guided to the air switching valve 62, the air switching valve 62 is opened, and the air pump 13 is driven, so that a part of the intake air that has passed through the air filter 43 is removed from the secondary air supply pipe 61. And, it can be guided into the exhaust pipe 54 via the distribution pipe 67.
[0025]
Further, the internal combustion engine 1 detects a temperature of cooling water flowing through a cooling water passage formed inside the internal combustion engine 1 and a crank position sensor 47 including a timing rotor and an electromagnetic pickup attached to an end of the crankshaft. And a water temperature sensor 46 attached to the cylinder block for the purpose.
[0026]
FIG. 2 shows the details of the structure of the exhaust port 53 and the exhaust branch pipe 52. Each cylinder 30 is provided with two intake valves 31 and two exhaust valves 51.
[0027]
An exhaust branch pipe 52 connected to each exhaust port 53 is formed downstream of the exhaust port 53 provided with the exhaust valve 51, and the plurality of exhaust branch pipes 52 are integrated downstream to form an exhaust pipe 54. It has become.
[0028]
The secondary air supply port 4 connected to the distribution pipe 67 is provided downstream of the exhaust valve 51.
[0029]
The thus configured internal combustion engine 1 is provided with an electronic control unit (Electronic Control Unit: ECU, hereinafter referred to as ECU) 20 for controlling the operation state of the internal combustion engine 1.
[0030]
Various sensors such as an air flow meter 44, a throttle position sensor 45, a water temperature sensor 46, a crank position sensor 47, and the like are connected to the ECU 20 via electric wiring. Based on this, it is possible to calculate the fuel injection timing and the ignition timing. In addition, it performs various controls related to the operation state of the internal combustion engine 1, and particularly controls the supply of secondary air to each exhaust port 53 through the driving of the air pump 13 and the opening and closing of the switching valve 62.
[0031]
Here, the secondary air supply control will be described.
[0032]
In the internal combustion engine 1, when the internal combustion engine 1 is operated under a low temperature condition (cold state), such as at the time of starting, the amount of fuel supplied to the combustion chamber through the fuel injection valve is increased to stabilize engine combustion. It is common to promote warming and warming up. However, if the mixture is enriched by increasing the fuel amount, unburned fuel (HC, CO, etc.) in the exhaust gas will increase. In addition, when the engine is cold, the temperature of the exhaust gas purification device is low, and the catalyst is not sufficiently activated.
[0033]
Therefore, when the air-fuel mixture is enriched when the catalyst temperature has not reached the activation temperature, such as during a cold start, the secondary air supply control is performed, and the exhaust gas immediately after being discharged from each combustion chamber is Mixing air promotes an oxidation reaction of unburned fuel components contained in exhaust gas. In this way, the purification of the unburned fuel components is promoted upstream of the exhaust purification device, and the activation of the catalyst of the exhaust purification device is accelerated by the reaction heat.
[0034]
Next, the secondary air supply control in the present invention will be specifically described.
(Embodiment 1)
In the present control, the internal combustion engine 1 is first started. Whether the internal combustion engine 1 is started or not is confirmed by the signal generated by the crank position sensor 47. A rotation speed NE is calculated from the signal, and the rotation speed NE is, for example, 400 rotations / min. If it has reached, it is determined that it has started. FIG. 4 is a time chart showing changes in the engine speed, the air-fuel ratio, the exhaust port temperature, the catalyst bed temperature, the amount of unburned HC, and the like before and after the secondary air supply after the start of the internal combustion engine 1.
[0035]
As shown in FIGS. 4A and 4B, the fuel injection amount is increased and the rotational speed NE of the internal combustion engine 1 is also increased immediately after the start because the engine is warmed up. However, the fuel injection amount temporarily decreases until the secondary air supply is started. The one shown by the broken line is a case where the secondary air is supplied immediately after the start (the same applies to the broken line hereinafter).
[0036]
Further, as shown in FIG. 4 (e), the primary A / F (air-fuel ratio of the air-fuel mixture in the cylinder) after starting is in a rich state, and thereafter becomes the stoichiometric air-fuel ratio.
[0037]
On the other hand, the secondary air-fuel ratio (the air-fuel ratio of the exhaust gas at the exhaust port) becomes a stoichiometric air-fuel ratio through a rich state after the start, as shown in (f).
[0038]
Next, the temperature of the internal combustion engine 1, that is, at least the temperature of the downstream portion of the exhaust valve 53, that is, the warm-up state of the exhaust port 53 is determined. First, an integrated intake air amount (air amount passing through the exhaust port 53) since the start of the internal combustion engine 1 is obtained. This is calculated by the ECU 20 based on the signal measured by the air flow meter 44. The air flow meter 44 measures the amount of air taken in for one second, for example, and obtains the total amount of air taken into the internal combustion engine 1 by integrating the measured values.
[0039]
The value α obtained by dividing the integrated air amount by the area of the exhaust port 53 is compared with a predetermined reference value β stored in the ROM (see FIG. 4C). The reference value β is a predetermined value determined by an experiment or the like, and is a predetermined value that can determine that the exhaust port has warmed up. Such a determination is made because whether or not the effect of the reburning by the secondary air supply can be obtained depends on the surface area of the exhaust port.
[0040]
If the value α is larger than the reference value β, it is determined that the exhaust port 53 has been warmed up, and the supply of the secondary air is started (FIG. 4C).
[0041]
As shown in FIGS. 4D and 4E, after the start of the supply of the secondary air, the primary air-fuel ratio becomes rich and the secondary air-fuel ratio becomes lean. This indicates that the air-fuel mixture containing a large amount of HC components is generated and discharged in the cylinder, but oxygen is supplied by the supply of the secondary air to change to a lean state, enabling re-combustion. The broken line indicates a change in the air-fuel ratio set when the secondary air is supplied immediately after the start.
[0042]
FIG. 4 (g) shows a change in the temperature of the exhaust port. According to the present invention, the speed of the temperature rise of the exhaust port is high as shown by the solid line. This is because, immediately after the start, the low-temperature secondary air is supplied to prevent the temperature of the exhaust port from rising.
[0043]
In FIG. 4 (h), the change in the catalyst bed temperature is shown, the solid line shows the case according to the present invention, and the broken line shows the case where secondary air is supplied immediately after starting (the same applies hereinafter). According to the present invention, since the effect of the reburning by the secondary air supply is efficiently exhibited, the catalyst bed temperature rises quickly. Accordingly, as shown in FIG. 4 (i), the amount of unburned HC present in the exhaust gas without being purified by the catalyst decreases.
[0044]
In this way, by starting the supply of the secondary air after the exhaust port 53 is warmed up, the catalyst bed temperature rises quickly, and the emission of unburned HC is greatly increased by improving the purification rate. It can be seen that it decreases.
[0045]
The control according to the present embodiment will be described with reference to the flowchart shown in FIG.
[0046]
A routine for executing a flowchart for calculation for determining use of the secondary air supply (AI) is stored in the ROM in advance, and is executed by the CPU at predetermined time intervals (for example, every time the crank position sensor 33 outputs a pulse signal). ) Is a routine that is repeatedly executed.
[0047]
In step 101, the internal combustion engine 1 is started. After the start, the routine proceeds to step 102, where it is determined whether or not the exhaust port is warmed up. Here, the ECU 20 compares the value α1 obtained by dividing the integrated air amount from the start of the internal combustion engine by the area of the exhaust port 53 with the reference value β1. If the value α1 is smaller than the reference value β1, the secondary air is not supplied and this routine ends.
[0048]
If the value α1 is larger than the reference value β1, the routine proceeds to step 103, in which the air pump 13 is operated. Next, the routine proceeds to step 104, in which the switching valve 62 is opened to start the supply of the secondary air. finish.
(Embodiment 2)
In this embodiment, only portions different from the first embodiment will be described.
[0049]
First, the internal combustion engine 1 is started. FIG. 5 shows the engine speed, the air-fuel ratio, the exhaust port temperature, the catalyst bed temperature, the unburned HC emission amount before and after the secondary air supply after the internal combustion engine 1 is started. Is shown as a time chart. This time chart is the same as that shown in FIG. 3. However, in order to determine whether the exhaust port 53 is warmed up, the integrated air amount is used in the first embodiment, but the integrated fuel injection amount is used in the second embodiment. In that it is calculated based on That is, the integrated fuel injection amount from the start of the internal combustion engine 1 is used to determine the warm-up state of the exhaust port 53. This is obtained by the ECU 20 calculating the total fuel injected from each fuel injection valve.
[0050]
A value α2 obtained by dividing the integrated fuel injection amount by the area of the exhaust port 53 is compared with a predetermined reference value β2 stored in the ROM (see FIG. 5C). The reference value β2 is a predetermined value obtained by an experiment or the like and is a predetermined value that can determine that the exhaust port has warmed up. If the value α2 is larger than the reference value β2, it is determined that the exhaust port 53 has been warmed up, and the supply of the secondary air is started (FIG. 5C).
[0051]
The calculation for secondary air supply (AI) determination according to the present embodiment will be described with reference to the flowchart shown in FIG.
[0052]
The routine for executing this flowchart is stored in the ROM in advance, and is a routine that is repeatedly executed by the CPU every predetermined time (for example, every time the crank position sensor 33 outputs a pulse signal).
[0053]
In step 201, the internal combustion engine 1 is started. After the start, the routine proceeds to step 202, where it is determined whether or not the exhaust port 53 has been warmed up. Here, the ECU 20 compares the value α2 obtained by dividing the integrated fuel injection amount from the start of the internal combustion engine by the area of the exhaust port 53 with the reference value β2. If the value α2 is smaller than the reference value β2, the secondary air supply is not started and this routine ends.
[0054]
Conversely, if the value α2 is larger than the reference value β2, the process proceeds to step 203, where the air pump 13 is operated, and then the process proceeds to step 204, where the switching valve 62 is opened to start the supply of the secondary air, This routine ends.
[0055]
In the above-described embodiment, a three-way catalyst has been exemplified as a purifying device for purifying exhaust gas discharged from the internal combustion engine 1. However, a purifying device for purifying other exhaust components may be used instead. Is also good.
[0056]
Further, in each of the above embodiments, an example in which the present invention is applied to a gasoline engine has been described. However, the present invention is not limited to this, and the present invention may be applied to a diesel engine.
[0057]
【The invention's effect】
According to the present invention, since the supply of the secondary air is started after the warm-up of the exhaust port of the internal combustion engine is completed, the cooling of the exhaust port with the secondary air is suppressed, and the exhaust gas is purified. An early rise of the catalyst bed temperature of the device is realized, and the exhaust emission is improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an internal combustion engine including a secondary air supply device according to an embodiment of the present invention.
FIG. 2 is a view showing a structure of a cylinder portion.
FIG. 3 is a flowchart illustrating a flow of a calculation for a secondary air use determination according to the first embodiment of the present invention.
FIG. 4 is a time chart of a secondary air supply control in the first embodiment of the present invention.
FIG. 5 is a flowchart showing a flow of a calculation for a secondary air use determination in Embodiment 2 of the present invention.
FIG. 6 is a time chart of secondary air supply control in the first embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Secondary air supply port 5 Exhaust purification device 13 Air pump 20 ECU
51 exhaust valve 52 exhaust branch pipe 54 exhaust pipe 62 switching valve

Claims (4)

A secondary air supply device comprising: a secondary air supply passage that supplies secondary air upstream of an exhaust gas purification device installed in an exhaust system of an internal combustion engine; and opening / closing means that opens and closes the secondary air supply passage. ,
A means for estimating the temperature of the exhaust port to which the secondary air is supplied is provided.The supply of the secondary air is prohibited until the temperature of the exhaust port becomes equal to or higher than a predetermined temperature, and the exhaust port is cooled by the secondary air. A secondary air supply device, characterized in that the air supply is suppressed. Considering at least one of the integrated intake air amount from the start of the internal combustion engine, the integrated injection amount of the fuel injection amount from the start of the internal combustion engine, and the engine water temperature and the surface area of the exhaust port. The secondary air supply device according to claim 1, wherein a warm-up state of the exhaust port is estimated, and a supply time of the secondary air is determined. When the value obtained by dividing the integrated intake air amount from the start of the internal combustion engine by the surface area of the exhaust port is determined to be larger than a predetermined reference value, secondary air supply is started. The secondary air supply device according to claim 1, wherein When it is determined that the value obtained by dividing the integrated fuel injection amount from the start of the internal combustion engine by the surface area of the exhaust port is larger than a predetermined reference value, secondary air supply is started. The secondary air supply device according to claim 1, wherein

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