JPH0715242B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a soluble organic component (SOF) in exhaust gas that causes white smoke and a foul odor in an internal combustion engine such as a diesel engine.
The present invention relates to an exhaust purification device that collects and removes.

2. Description of the Related Art In an internal combustion engine such as a diesel engine, a soluble organic component (SOF), which is one of exhaust particulates contained in exhaust gas, causes white smoke and odor. This is because some of the fuel components and the lubricating oil that flowed into the combustion chamber were exhausted without being sufficiently burned, which often occurs when the engine is in a cold state, especially in the low-speed low-load region where combustion is unstable. To do.

The treatment of the SOF component is generally performed by a method of collecting and removing it by a filter-like trap provided in the exhaust passage. FIG. 8 shows a conventional exhaust gas purification device disclosed in Japanese Patent Laid-Open No. 57-159908, in which a trap 32 with a catalyst is provided upstream of a muffler 34 in an exhaust passage 33 of an internal combustion engine 31. Has been done. The catalyst-attached trap 32 is formed into a filter shape using, for example, ceramics, and the surface thereof is coated with a catalyst metal.

That is, in the above-mentioned exhaust gas purification device, the exhaust gas always passes through the catalyst-equipped trap 32, and at that time, the SOF component is collected. Then, when the exhaust temperature becomes high and the catalyst is activated at high speed and high load, the trapped SOF component is self-combusted by its catalytic action, and the trap 32 is naturally regenerated.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional exhaust gas purifying apparatus in which the catalyst-equipped trap 32 is simply provided in the exhaust passage 33 as described above, the internal combustion engine 31 is cooled immediately after the start of the automobile. When the operation is started, the exhaust pressure rises when the exhaust gas temperature and the temperature of the exhaust passage 33 do not rise sufficiently.Therefore, the SOF component collected at the start is catalytically processed before being treated. There is a risk that the trap 32 will come off. The SOF component separated from the catalyst-equipped trap 32 re-condenses because the exhaust passage 33 is cold, causing white smoke and a bad smell.

Furthermore, in a diesel engine, the exhaust gas contains garbon particles, so the exhaust temperature is lower than the catalyst activation temperature (about 400 ° C).
When operated for a long time under a low / medium load condition such that the exhaust gas pressure does not reach a certain level), the trap with catalyst 32 is clogged, and the exhaust pressure rises.

Means for Solving the Problems In order to solve the above problems, an exhaust gas purification apparatus for an internal combustion engine according to the present invention, as shown in FIG.
Of the engine 1, an on-off valve 3 installed in the exhaust passage 2, an exhaust bypass passage 4 formed by bypassing the on-off valve 3, a trap 5 with a catalyst installed in the exhaust bypass passage 4, Engine temperature detecting means 6 for detecting the temperature, load detecting means 7 for detecting the load of the engine 1, rotational speed detecting means 8 for detecting the rotational speed of the engine 1, and these detecting means 6, 7,
An opening / closing valve control means 9 for closing the opening / closing valve 3 at least in a predetermined engine braking state based on the detection signal of 8 is provided.

Action The on-off valve 3 is normally in the open state, and therefore, most of the exhaust gas passes through the on-off valve 3 side without passing through the catalyst-equipped trap 5.

When the internal combustion engine 1 is in a predetermined engine braking state,
For example, at the time of engine braking when the engine temperature is sufficiently high and the engine speed is at an appropriate height, the opening / closing valve 3 is closed and most of the exhaust gas is guided to the trap 5 with catalyst. At this time, the trap 5 with catalyst is sufficiently activated by the exhaust heat, so that the SOF component previously collected is self-combusted.

Embodiment FIG. 2 shows an embodiment of the exhaust emission control device according to the present invention.

In the figure, 11 is an internal combustion engine such as a diesel engine, 13 is an exhaust passage connected to an exhaust manifold 12 of the internal combustion engine 11, and a butterfly valve type on-off valve 14 is provided in the middle of the exhaust passage 13. It is equipped. 15 is the on-off valve 14
This is an exhaust bypass passage formed by bypassing the exhaust gas. The exhaust bypass passage 15 is provided with a trap 16 with a catalyst for collecting and removing SOF components. The catalyst-attached trap 16 is made of, for example, filter-like ceramics, and has a surface coated with a catalyst metal, and is supported by the casing via a cushioning material 17.

The on-off valve 14 has its valve shaft 14a linked to a rod 18a of a negative pressure diaphragm type actuator 18 via a lever 14b, and a negative pressure is introduced into the negative pressure chamber of the actuator 18. It is configured so that it is in a substantially fully closed state as indicated by the solid line, and is in a substantially fully opened state as indicated by the imaginary line when the atmosphere is introduced into the negative pressure chamber. Then, in the negative pressure passage 20 connecting the negative pressure chamber of the actuator 18 and the vacuum pump 19, a three-way solenoid valve 21 having an atmosphere communication hole 21a is provided.
Is installed. The three-way solenoid valve 21 is configured so that the negative pressure chamber communicates with the negative pressure pump 19 side when energized, and the negative pressure chamber communicates with the atmosphere communication hole 21a side when not energized.

Next, reference numeral 22 denotes a control circuit using a digital microcomputer for switching and controlling the three-way solenoid valve 21.
The control circuit 22, the water temperature sensor 23 for detecting the cooling water temperature representative of the temperature of the internal combustion engine 11, a rotation speed sensor 24 for detecting the rotation speed of the internal combustion engine 11, the load of the internal combustion engine 11,
Specifically, the control lever 25a of the fuel injection pump 25
The water temperature signal VTW, the rotation speed signal VREV, and the load signal VL are input from the lever opening sensor 26 that detects the opening.

Next, the operation of the above embodiment will be described based on the flowchart of FIG.

This flowchart shows an outline of the control program executed by the control circuit 22. First, step 1
Then, the cooling water temperature TW, the load L, and the rotation speed REV detected based on the water temperature signal VTW, the load signal VL, and the rotation speed signal VREV are read, and then in step 2, whether the cooling water temperature TW is 60 ° C or lower is determined. To determine.

If the temperature is below 60 ° C, proceed to step 3,
From the load L and the rotation speed REV, it is determined whether the engine operating conditions correspond to the white smoke region. As shown in FIG. 4, this white smoke region is set to a low speed and low load region including idling. If the white smoke region is determined in the determination in step 3, the process proceeds to step 8 and the three-way solenoid valve 21 is turned on. As a result, negative pressure is introduced into the negative pressure chamber of the actuator 18, and the opening / closing valve 14 is brought into a substantially fully closed state. Also, step 3
If it is not in the white smoke area, proceed to step 7 and set the three-way solenoid valve.
Turn OFF 21. This allows the negative pressure actuator 18
Atmosphere is introduced into the negative pressure chamber, and the on-off valve 14 is in a substantially fully opened state.

Therefore, assuming that the low-speed low-load operation including idling is performed in a state where the internal combustion engine 11 is not sufficiently warmed up immediately after starting, most of the exhaust gas passes through the catalyst-equipped trap 16 as the opening / closing valve 14 is closed. Will be exhausted here
SOF components are collected and removed. Therefore, it is possible to prevent the generation of white smoke and odor, which are problems in low-speed low-load operation in the engine cold state.

On the other hand, when the cooling water temperature TW is 60 ° C. or higher in step 2, the process proceeds to step 4 and it is determined whether or not the idling state. This idling determination is made based on the engine load L and the rotational speed REV, as shown in FIG. If it is in the idling state, the process proceeds to step 8 to close the opening / closing valve 14 via the three-way solenoid valve 21. Therefore, if idling, the cooling water temperature TW
Most of the exhaust gas is always trapped with catalyst regardless of the height of the trap 16
You will be guided to the side and the SOF component will be removed. This is because a bad odor or white smoke drifts around in the idling state where the vehicle is not running, so that a relatively small amount of SOF component in the warm state is surely removed.

Next, if it is determined in step 4 that the engine is not in the idling state, the process proceeds to step 5 and it is determined whether the engine is in a braking state (deceleration state). If it is not in the engine braking state, the process proceeds to step 7 and the opening / closing valve 14 is maintained in a substantially fully opened state. Incidentally, when the on-off valve 14 is in a substantially fully opened state as described above, almost no exhaust gas flows to the catalyst-equipped trap 16 side due to the passage resistance.

When it is determined in step 5 that the engine is in the braking state, the process further proceeds to step 6 and it is determined whether the rotation speed REV is within a predetermined range, for example, 2000 to 4000 RPM. Only when the rotation speed REV is within the predetermined range, the routine proceeds to step 8 to close the on-off valve 14, and in other rotation speed regions, the routine proceeds to step 7 to open the on-off valve 14.

That is, most of the exhaust gas is guided to the catalyst-equipped trap 16 side only when the internal combustion engine 11 is warmed up, the deceleration operation is performed, and the rotation speed is 2000 to 4000 RPM. Such deceleration always occurs after acceleration or steady operation, so even if the exhaust temperature drops slightly, the 200% required for re-combustion of the SOF component due to the residual heat of the exhaust system.
A temperature of ℃ or more can be sufficiently obtained, and in this engine braking state, since almost no fuel is supplied to the engine, the exhaust particulates in the exhaust are almost eliminated and the exhaust becomes a very clean exhaust gas. The adhered SOF component is efficiently burned and removed. As a result, the trap with catalyst 16 is regenerated and its clogging is prevented.

It should be noted that when the rotation speed is 2000 RPM or less, the trap with catalyst 16
The reason why the exhaust gas is not allowed to flow through is that the exhaust gas heat necessary for the combustion of the SOF component cannot be secured as described above. Also, 40
Trap with catalyst for exhaust at rotational speeds above 00 RPM 16
Although not guided to the side, it is suitable for re-combustion of the SOF component in terms of temperature, but the exhaust flow rate is very large and the passage resistance of the catalyst-equipped trap 16 becomes relatively large. This is because there is a fear that it will be given to other people.

Therefore, according to the above-described embodiment, for example, when the vehicle is started to run immediately after the internal combustion engine 11 is started in the cold state, the exhaust gas is discharged to the catalyst trap 16 side in a region where white smoke and a bad odor do not matter. I was not guided, so I was collected once
The SOF component will not be removed from the trap with catalyst 16 before re-combustion. Further, even if the operation at medium load where the exhaust temperature is not so high is continued for a long time, the catalyst-attached trap 16 will not be clogged with fine particles such as carbon. Then, the trap with catalyst 16 that has collected the SOF component is naturally regenerated in the predetermined engine braking state while continuing the operation after the completion of warming up.

Next, FIGS. 5 to 7 show different embodiments of the present invention.

This embodiment has a predetermined rotation speed range (for example, 2000 to 4000RP
If the elapsed time from entering the engine braking state of (M) is too long, for example, in an operating state such as going down a long slope, not only the combustion of the SOF component becomes impossible due to the decrease of the exhaust temperature but also the trap 16 with catalyst is On the contrary, since it is cooled, the flow of the exhaust gas to the catalyst-equipped trap 16 is stopped when a predetermined time or more has elapsed.

That is, when it is determined that the engine is in the warm-up state (cooling water temperature TW is 60 ° C or higher) and the engine speed is in the predetermined rotation speed range (2000 to 4000RPM), the process proceeds from step 6 to step 10 and the timer counts. To start. In this step 10, as shown in FIG. 6, the flag indicating that engine braking is continuing is turned on for the first time (step 10b), and the timer is sequentially incremented in step 10c.

Then, in step 11, the value of the timer is set to a predetermined value, for example, 10
It is determined whether or not the time has exceeded the second, and if it is within 10 seconds, the process proceeds to step 8 and the three-way solenoid valve 21 is turned on. Also, if it exceeds 10 seconds, proceed to step 7 and set the three-way solenoid valve 21.
Turn off. Therefore, even if the engine braking state in the predetermined rotation speed region continues for a long time, the exhaust gas is guided to the catalyst-equipped trap 16 side for the first 10 seconds, and thereafter the exhaust gas flow is stopped. Therefore, the temperature decrease of the trap with catalyst 16 due to the decrease of the exhaust temperature is avoided.

If the engine brake state is released or if the rotation speed REV is outside the predetermined range while the engine brake state is being continued, proceed from step 5, step 6 to step 9 and reset the timer here. later,
Proceed to step 7 and turn off the three-way solenoid valve 21. In addition,
In step 9 above, as shown in FIG. 7, the flag indicating continuation of the engine braking state is turned off (step 9
a) and then reset the timer (step 9
b).

Therefore, according to the above-mentioned embodiment, the re-combustion of the SOF component, that is, the regeneration of the catalyst-equipped trap can be performed more reliably, and the clogging due to the poor regeneration of the catalyst-equipped trap 16 can be prevented.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the exhaust gas is guided to the trap side with catalyst only when the SOF component is collected by switching the flow path by the opening / closing valve. Therefore, unlike the conventional structure in which the exhaust gas always flows through the trap with catalyst, the SOF component once collected does not separate before reburning. Therefore,
It is possible to effectively remove white smoke and offensive odors that are a problem in diesel engines, etc., and to prevent the release of SOF components once collected into the atmosphere. Further, in an operating region where white smoke or the like does not pose a problem, exhaust gas does not flow through the catalyst-equipped trap, so that the accumulation of fine particles such as carbon is prevented. Then, because the trap is regenerated using exhaust heat from the engine in a state of engine braking that hardly contains particles that are difficult to reburn such as carbon, the SOF component is effectively reburned and the trap with catalyst is clogged. It can be surely prevented.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims showing the configuration of the present invention, FIG. 2 is a configuration explanatory view showing an embodiment of an exhaust emission control device according to the present invention, and FIG. 3 is a flowchart showing a control program in the above embodiment, FIG. FIG. 4 is a control characteristic diagram of this embodiment,
FIGS. 5, 6, and 7 are flowcharts showing different embodiments of the control program, and FIG. 8 is a configuration explanatory view showing an example of a conventional exhaust emission control device. DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Exhaust passage, 3 ... Open / close valve, 4 ... Exhaust bypass passage, 5 ... Catalyst trap, 6 ... Engine temperature detecting means, 7 ... Load detecting means, 8 ... Rotation speed detecting means, 9 ... Open / close Valve control means.

Claims (1)

[Claims] 1. An on-off valve disposed in an exhaust passage of an internal combustion engine, an exhaust bypass passage formed by bypassing the on-off valve, a trap with a catalyst disposed in the exhaust bypass passage, and an engine Engine temperature detecting means for detecting temperature, load detecting means for detecting load of the engine, rotational speed detecting means for detecting rotational speed of the engine, and at least a predetermined engine braking state based on detection signals of these detecting means. An exhaust gas purifying apparatus for an internal combustion engine, comprising: an opening / closing valve control means for closing the opening / closing valve.