JP2006220080A - Sulfurous odor prevention device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize the occurrence and feeling of sulfurous odor after an engine is warmed up. <P>SOLUTION: When an engine is under sulfurous odor emitting conditions in which at least the temperature of a catalyst is high (S2) in an idle operation or a low vehicle speed operation after warm-up operation (S1), a secondary air is supplied to the upstream side of the catalyst in an exhaust passage (S3). Since exhaust gases are brought into an oxidizing atmosphere and H2S is oxidized to SO2, the sulfurous odor can be prevented from occurring. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for preventing sulfur odor of exhaust gas from an internal combustion engine for automobiles.

In Patent Document 1, when releasing sulfur poisoning of the NOx storage catalyst, H2S (hydrogen sulfide) is released from the tail pipe into the atmosphere to prevent the generation of sulfur odor. It is disclosed that H2S is oxidized by supplying secondary air.
JP 2002-309929 A

In Patent Document 1, only a countermeasure against the sulfur odor at the time of releasing the sulfur poisoning of the NOx storage catalyst is taken, but the present inventors have examined a scene where the sulfur odor becomes more problematic and have obtained a certain conclusion.
That is, although the generation mechanism of the sulfur odor itself has not been elucidated, the study by the present inventors has revealed that the sulfur odor is generated even when the catalyst temperature is high even in a three-way catalyst or the like, and this occurs during idle operation or low vehicle speed operation. It was found that you can feel strongly.

  In view of the above, an object of the present invention is to make it possible to prevent the feeling of sulfur odor as much as possible.

  Therefore, in the present invention, the secondary air is supplied to the upstream side of the catalyst in the exhaust passage at the time of idle operation or low vehicle speed operation after engine warm-up and at least when the catalyst temperature is a sulfur odor generating condition. And

  According to the present invention, H2S, which is the source of sulfur odor, is provided by supplying secondary air and making the exhaust atmosphere an oxidizing atmosphere in consideration of conditions where sulfur odor is likely to occur and conditions where this is easy to experience. Can be oxidized to SO2 or the like to prevent the odor of sulfur as much as possible.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an engine system diagram showing an embodiment of the present invention.
In the intake passage 2 of the engine 1, an electrically controlled throttle valve 4 that is positioned on the inlet side of the intake manifold 3 and controls the amount of intake air is installed. The opening degree of the electric throttle valve 4 is controlled by a step motor or the like that is operated by a signal from an engine control unit (hereinafter referred to as ECU) 20. However, a mechanical throttle valve connected to the accelerator pedal by a wire or the like may be used.

A fuel injection valve 6 for injecting fuel into the intake port 5 of each cylinder is attached to the branch portion on the outlet side of the intake manifold 3. The fuel injection valve 6 is opened by energizing the solenoid for a time determined by the pulse width based on the injection pulse signal output from the ECU 20 in synchronization with the engine rotation, and injects the fuel adjusted to a predetermined pressure. .
The air controlled by the electric throttle valve 4 and the fuel injected from the fuel injection valve 6 are sucked into the combustion chamber 8 of the engine 1 when the intake valve 7 is opened.

  The air and fuel sucked into the combustion chamber 8 form an air-fuel mixture, and are ignited and burned by the spark plug 9 at the ignition timing controlled by the ECU 20. The exhaust gas after combustion is discharged to the exhaust passage 11 (exhaust port 12) through the exhaust valve 10. The exhaust passage 11 includes an exhaust port 12 formed for each cylinder in the cylinder head, an exhaust manifold 13 connected to the outlet side thereof, and the like. An exhaust purification catalyst 14 is provided.

  Here, an electric air pump 15 is provided as a secondary air supply device in order to supply secondary air to the exhaust port 12 of each cylinder in the cylinder head, which is a high temperature part of the exhaust gas, upstream of the catalyst 14 in the exhaust passage 11. The discharge side is connected to a secondary air supply passage 18 that opens to an exhaust port 12 for each cylinder via a shutoff valve 16 and a distribution pipe (gallery) 17. Here, the secondary air is supplied to the exhaust port 12 as long as it is upstream of the catalyst 14 in the exhaust passage 11, and may be any cylinder, cylinder group, or common to all cylinders.

  The ECU 20 detects the accelerator opening APO detected by the accelerator pedal sensor 21 (including an idle switch signal that is turned on when the accelerator is fully closed), the engine speed Ne detected by the crank angle sensor 22, and the air flow meter 23. The intake air amount Qa, the engine cooling water temperature Tw detected by the water temperature sensor 24, the exhaust air / fuel ratio detected by the air / fuel ratio sensor 25, the catalyst temperature Tc detected by the catalyst temperature sensor 26, and the vehicle speed sensor 27. A vehicle speed VSP or the like is input as necessary.

  The ECU 20 controls the opening degree of the electric throttle valve 4, the fuel injection timing and fuel injection amount of the fuel injection valve 6, the ignition timing of the spark plug 9, and the like based on the engine operating conditions detected from these input signals. . Further, the operation of the air pump 15 and the shutoff valve 16 is controlled. The shutoff valve 16 is opened when the air pump 15 is turned on and closed when the air pump 15 is turned off, and can be omitted when the air pump 15 itself has a shutoff function when turned off.

  Here, when there is a catalyst temperature increase request immediately after startup, for example, when the catalyst temperature Tc detected by the catalyst temperature sensor 26 is lower than a predetermined activation temperature, the engine-side air-fuel ratio is set to be rich, In a state where a large amount of unburned fuel is discharged to the exhaust port 12, the air pump 15 is turned on and the shutoff valve 16 is opened to supply secondary air to the exhaust port 12. That is, a large amount of unburned fuel is discharged to the exhaust port 12 and is reburned by supplying secondary air, whereby the exhaust temperature is raised and the catalyst 14 is activated early.

On the other hand, in the present invention, as a countermeasure against sulfur odor after engine warm-up, a secondary air supply device is used to perform sulfur odor prevention control.
FIG. 2 is a flowchart of a first embodiment of sulfur odor prevention control performed after engine warm-up.
In S1, it is determined whether or not the engine is in idle operation (idle switch ON) based on a signal from the idle switch in order to determine whether or not it is a condition that makes it easy to experience the sulfur odor. Alternatively, based on a signal from the vehicle speed sensor, it is determined whether or not the vehicle is operating at an extremely low vehicle speed (the vehicle speed VSP is a predetermined value or less). In addition, whether or not the vehicle is stopped in an idle operation state (idle switch ON) (when vehicle speed VSP = 0), or at an extremely low vehicle speed in an idle operation state (idle switch ON) (vehicle speed VSP ≦ predetermined value). It may be determined whether or not.

If the result of determination in S1 is YES, the process proceeds to S2, and if NO, the process returns to S1.
In S2, the catalyst temperature Tc detected by the catalyst temperature sensor is read to determine whether or not the sulfur odor generating condition is satisfied, and it is determined whether or not the catalyst temperature Tc is equal to or higher than a predetermined value TH set as the sulfur odor generating condition.
If the result of determination in S2 is YES, the process proceeds to S3, and if NO, the process returns to S1.

In S3, in order to prevent the generation of sulfur odor, the supply of secondary air to the exhaust passage (exhaust port) is started as the air pump is turned on and the shut-off valve is opened. As a result, the exhaust gas becomes an oxidizing atmosphere, and H2S, which is a source of sulfur odor, is oxidized to SO2 and the like, and the odor can be prevented.
After the supply of secondary air is started, the determinations of S4 and S5 are repeated.
In S4, as in S1, it is determined whether or not the vehicle is in idling or extremely low vehicle speed operation. If NO, the process proceeds to S6 to turn off the air pump and close the shutoff valve to the exhaust passage (exhaust port). Stop the supply of secondary air.

  In S5, the catalyst temperature Tc detected by the catalyst temperature sensor is read, and it is determined whether or not the catalyst temperature Tc is equal to or less than a predetermined value TL determined with hysteresis with respect to the predetermined value TH determined as the sulfur odor generating condition. Judgment (TL <TH). If YES (Tc ≦ TL) as a result of the determination, the process proceeds to S6, and the supply of secondary air to the exhaust passage (exhaust port) is stopped by turning off the air pump and closing the shut-off valve.

As described above, considering the conditions where sulfur odor is likely to be generated and conditions where this is easy to experience, by supplying secondary air and setting the exhaust to an oxidizing atmosphere, H2S which is the source of sulfur odor is reduced. Oxidation to SO2 or the like can prevent the odor of sulfur as much as possible.
Further, by supplying the secondary air to the upstream side of the catalyst, the exhaust temperature is higher than when supplying the downstream side of the catalyst, so that the oxidation reaction from H2S to SO2 or the like can be promoted.

In addition, the secondary air supply device that has been used only immediately after the low temperature start for effective activation of the catalyst can be effectively used.
In particular, according to the present embodiment, the sulfur odor generation condition can be accurately grasped by detecting the catalyst temperature directly or indirectly and judging whether or not the catalyst temperature is equal to or higher than a predetermined value. The catalyst temperature may be indirectly detected from the exhaust gas temperature downstream of the catalyst.

In particular, according to the present embodiment, after the start of the supply of secondary air, after detecting a decrease in the level of the sulfur odor generating condition, the supply time of the secondary air is excessively insufficient by stopping the supply of the secondary air. It can be appropriate without.
FIG. 3 is a flowchart of a second embodiment of sulfur odor prevention control performed after engine warm-up. The difference from the first embodiment (FIG. 2) is the portions S2 ′ and S5 ′, and only this will be described.

  In S2 ′, in order to determine whether or not the sulfur odor generation condition is satisfied, the catalyst temperature detected by the catalyst temperature sensor and the air-fuel ratio detected by the air-fuel ratio sensor are read, and the catalyst temperature and air-fuel ratio are calculated from FIG. Referring to the map, the sulfur odor generation index value Sa is calculated, and it is determined whether or not the sulfur odor generation index value Sa is equal to or greater than a predetermined value SH defined as the sulfur odor generation condition. If the result of determination is YES, the process proceeds to S3 to start supplying secondary air.

Here, as shown in FIG. 4, the sulfur odor generation index value Sa is set so as to increase as the catalyst temperature increases and the air-fuel ratio increases.
In S5 ′, the catalyst temperature detected by the catalyst temperature sensor and the air-fuel ratio detected by the air-fuel ratio sensor are read, and the sulfur odor generation index value Sa is determined from the catalyst temperature and the air-fuel ratio with reference to the map of FIG. Is calculated, and it is determined whether or not the sulfur odor generation index value Sa is equal to or less than a predetermined value SL determined with hysteresis with respect to the predetermined value SH determined as the sulfur odor generation condition (SL <SH). . If the determination result is YES (Sa ≦ SL), the process proceeds to S6 and the supply of secondary air is stopped.

In particular, according to the present embodiment, the sulfur odor generation condition can be accurately dealt with by the generation of the sulfur odor in the high rich state by judging from the catalyst temperature and the air-fuel ratio.
FIG. 5 is a flowchart of a third embodiment of sulfur odor prevention control performed after engine warm-up. The difference from the first embodiment (FIG. 2) is the portions S2 ″ and S5 ″, and only this will be described.

  In S2 ″, in order to determine whether or not the sulfur odor generating condition is satisfied, it is determined whether or not the sulfur odor generating condition is satisfied based on the operation history immediately before the transition to the idle operation (or extremely low vehicle speed operation). Is whether or not the vehicle has been driven at a high vehicle speed for a long time, more specifically, whether or not the driving time at the immediately preceding high vehicle speed is a predetermined time or more, or whether the average vehicle speed within the immediately preceding predetermined time is a predetermined value or more. If the result of determination is YES, the process proceeds to S3 to start supplying secondary air.

In S5 ″, it is determined whether or not a predetermined time has elapsed after the secondary air supply is started. If the result of determination is YES, the process proceeds to S6, and the supply of secondary air is stopped.
In particular, according to the present embodiment, the sulfur odor generation condition is determined from the driving history immediately before shifting to the idling operation or the low vehicle speed operation, so that it can be implemented even when the catalyst temperature sensor is not provided.
In particular, according to the present embodiment, the control can be simplified by stopping the supply of the secondary air after a predetermined time has elapsed since the start of the supply of the secondary air. Such time control can also be applied to the first embodiment (FIG. 2) and the second embodiment (FIG. 3).

1 is a system diagram of an internal combustion engine showing an embodiment of the present invention. Flow chart of the first embodiment of sulfur odor prevention control Flow chart of second embodiment of sulfur odor prevention control The figure which shows the map for sulfur odor generation index value calculation used in 2nd Example Flow chart of third embodiment of sulfur odor prevention control

Explanation of symbols

1 engine
2 Intake passage
3 Intake manifold
4 Electric throttle valve
5 Intake port
6 Fuel injection valve
7 Intake valve
8 Combustion chamber
9 Spark plug
10 Exhaust valve
11 Exhaust passage
12 Exhaust port
13 Exhaust manifold
14 Exhaust gas purification catalyst
17 Electric air pump
16 Shut-off valve
17 Piping (Gallery)
18 Secondary air supply passage
20 ECU
21 Accelerator pedal sensor (idle switch)
22 Crank angle sensor
23 Air Flow Meter
24 Water temperature sensor
25 Air-fuel ratio sensor
26 Catalyst temperature sensor
27 Vehicle speed sensor

Claims (6)

In an internal combustion engine for an automobile provided with an exhaust purification catalyst in an exhaust passage,
2. The secondary air is supplied upstream of the catalyst in the exhaust passage at the time of idle operation after engine warm-up or low vehicle speed operation, and at least when the catalyst temperature is at a high sulfur temperature generation condition. The sulfur odor prevention apparatus of the internal combustion engine of description.   2. The sulfur odor prevention apparatus for an internal combustion engine according to claim 1, wherein the sulfur odor generation condition is determined by directly or indirectly detecting a catalyst temperature and determining whether or not the temperature is equal to or higher than a predetermined value.   2. The sulfur odor prevention apparatus for an internal combustion engine according to claim 1, wherein the sulfur odor generation condition is determined from a catalyst temperature and an air-fuel ratio.   2. The sulfur odor prevention apparatus for an internal combustion engine according to claim 1, wherein the sulfur odor generation condition is determined from an operation history immediately before shifting to idle operation or low vehicle speed operation.   The internal combustion engine according to any one of claims 1 to 3, wherein the supply of the secondary air is stopped after detecting a decrease in the level of the sulfur odor generation condition after the supply of the secondary air is started. Sulfur odor prevention device.   The sulfur odor prevention apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the supply of the secondary air is stopped after a lapse of a predetermined time from the start of the supply of the secondary air.

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