JPH0544436A - Exhaust gas purifying device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent choking of a purifying device by arranging a purifying device and an exhaust gas throttle valve in an exhaust gas passage and providing a detecting device to detect the choking state of the purifying device and a control device to open the exhaust gas throttle valve after the valve is closed during a time for which rotation is effected at the given number of revolutions high enough to allow the increase of an exhaust pressure. CONSTITUTION:When an engine 1 is run, exhaust gas flows through an exhaust gas passage 3 to a catalyst 4 and after it is purified, it is discharged in the open air. A control unit 6 inputs signals from a first pressure sensor 7, a second pressure sensor 8, a number of revolutions detecting device 9, and a load detecting device 10, compares a normal differential pressure given value when it is equivalent to the actual measurement number of revolutions of an engine and a load with an actual measurement differential pressure, and decides chocking of the catalyst 4. When choking occurs, a command is given to an actuator 11, and an exhaust gas throttle valve 5 is closed. When the exhaust gas throttle valve 5 is opened after a lapse of a given time, exhaust gas generates forced blow, and carbon which is about to be stuck to the catalyst 4 or with which the catalyst is about to be choked is removed at once so as to prevent the occurrence of choking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device for a diesel engine among internal combustion engines.

[0002]

2. Description of the Related Art Diesel engines use carbon and SOF as particulates in the exhaust gas.
(Soluble organic substance) Since these substances are included, it is necessary to remove these substances. Therefore, for example, it is proposed to provide a catalyst (such as an open honeycomb catalyst) for oxidizing SOF in the exhaust passage.

[0003]

However, in a diesel engine, when an open honeycomb catalyst is provided in the exhaust passage for exhaust gas purification and a low load operation is carried out for a long time, the catalyst is clogged by particulates and exhausted. There is a problem in that the pressure rises and the output and fuel efficiency deteriorate.

Further, when a high load operation is carried out in such a clogging state, there is a problem that the accumulated particulates are abruptly burned due to the increase in exhaust temperature and the catalyst is burned out.

Therefore, it is conceivable to use a re-combustion type and burn and regenerate the deposited particulates at the time of clogging, but this has a problem that the combustion device is expensive and complicated.

Therefore, the present invention has an object to achieve the above object by providing an exhaust gas purification apparatus for an internal combustion engine which eliminates the clogging of the catalyst without the apparatus becoming expensive and complicated. ..

[0007]

In order to achieve the above object, the present invention provides a purifying device and an exhaust throttle valve in an exhaust passage of a diesel engine, and a detecting device for detecting a clogging state of the purifying device. A control device is provided that opens the exhaust throttle valve after closing the exhaust throttle valve for a predetermined period of time such that exhaust pressure rises or during engine speed, in response to a detection signal from the detection device.

[0008]

When the catalyst is about to be clogged, the detection device detects it and outputs it to the control device. The control device commands the operation to close the exhaust throttle valve once and open it when the exhaust pressure rises. As a result, the exhaust gas increases in exhaust pressure in the upstream side and decreases in the downstream side, and a sudden pressure change causes a vigorous flow, that is, forced exhaust blow, and with that energy flows into the catalyst and adheres to the catalyst. The curate is blown off and removed from the catalyst. Since this device only needs a mechanical throttle valve and its control device, it is inexpensive and simple. It is to be noted that what is released to the atmosphere by the forced blow is a part of carbon in the particulates, and the SOF in the particulates is surely removed, so that the total amount of the particulates discharged can be reduced. ..

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, the structure will be described with reference to FIG. The diesel engine 1 includes an injection pump 2 that injects fuel, and an exhaust passage 3 that includes a catalyst 4. The catalyst 4 has an open honeycomb structure provided with a large number of fine passages like a honeycomb, and collects particulates in exhaust gas, especially SOF, to purify the particulates. It is needless to say that another adhering and collecting type purifying device may be used instead of this catalyst.

An exhaust throttle valve 5 is provided downstream of the catalyst 4 in the exhaust passage 3, and the exhaust throttle valve 5 is opened and closed by a solenoid type actuator 11 to block or release the exhaust flow. You can do it. The control unit 6 outputs a pressure difference across the catalyst 4 (differential pressure Δ
Both signals P ₁ and P ₂ of the first pressure sensor 7 and the second pressure sensor 8 for detecting P) are input, and at the same time, the engine speed signal N of the engine speed detection device 9 and the injection pump 2 The load signal L of the load detection device 10 that detects the load based on the control lever opening or the like is input.

The control unit 6 is provided with a map of the differential pressure ΔP across the catalyst shown in FIG. 2, and when the catalyst 4 is likely to be clogged, this is read and searched on the map and the value and the measured value are compared. Judgment, actuator 1
It is designed to command 1.

In FIG. 2, the horizontal axis represents the engine speed N, and
The load L is plotted on the vertical axis, and the differential pressure ΔP when the catalyst 4 is normal, that is, in a normal state where no adhesion or clogging has occurred.
The map is drawn. a, b, c, d are lines of equal pressure differential lines ΔPa, ΔPb, ΔPc, ΔPd,
It is shown that ΔP becomes higher as the rotation speed becomes larger and the load becomes larger, that is, in the direction of the arrow of the diagonal straight line W. In FIG. 2, four performance curves of ΔP are shown, but they should be created more densely, or an intermediate value between them should be calculated. As described above, the control unit 6, the first pressure sensor 7, the second pressure sensor 8, the engine speed detection device 9, and the load detection device 10 constitute the clogging detection device 13.

Next, the operation of the above embodiment will be described with reference to FIGS.

When the engine 1 is operated, the exhaust gas reaches the catalyst 4 from the exhaust passage 3, is cleaned, and is then discharged to the atmosphere.

The control unit 6 inputs signals from the first pressure sensor 7, the second pressure sensor 8, the engine speed detection device 9 and the load detection device 10, and when they correspond to the measured engine speed N and load L. Normal value of the differential pressure (for example, ΔPb at point B on the map of FIG. 2) and the measured differential pressure ΔP ′
b, that is, (P ₁ -P ₂ ) is constantly compared. If these values are equal, it can be said that the catalyst 4 does not cause clogging and functions in a clean (normal) state.

As a result of long-time low-speed engine operation, the measured differential pressure ΔP'b exceeds the differential pressure predetermined value ΔPb, and the value is 15
Suppose that it has exceeded about 20%. It is judged that the catalyst 4 is starting to be clogged in the state where the exhaust pressure rises to this extent.

The control unit 6 then instructs the actuator 11 to once close the exhaust throttle valve 5. Then, after a predetermined time (0.1 seconds to 1 second) has passed, that is, when the exhaust pressure at the upstream side of the exhaust throttle valve 5 increases.
To open. Then, the exhaust creates a flow (forced blow) due to a sudden pressure change, flows into the catalyst 4, and removes carbon in the particulates that is adhering or clogged in the internal fine passages all at once, and discharges it downstream. Become. Therefore, the clogging of the catalyst 4 is avoided. The above operation is automatically performed. Therefore, the engine 1 does not deteriorate in output and fuel efficiency,
You can continue driving. Further, it is also prevented that the catalyst is clogged and burned out under high load operation.

Even if the particulates due to the forced blow are released to the atmosphere to some extent, the amount of the particulates is small, so there is no emission problem. Further, the clogging removal according to this embodiment has the advantage that the device is simple and inexpensive because it is forced blow of exhaust gas by a mechanical operation of closing and opening the exhaust throttle valve 5.

FIG. 3 shows a flow chart of the above embodiment. To explain this, after the start, step 1
The load, engine speed, pre-catalyst pressure and post-catalyst pressure are read in, the predetermined value of the differential pressure is retrieved from the differential pressure map in step 2, and it is compared in step 3 whether the measured value of the differential pressure is larger than the predetermined value. If it is larger, the exhaust throttle valve is closed in step 4, and is opened and returned after a predetermined time has elapsed.

FIG. 4 shows a second embodiment. In this embodiment, the temperature sensor 12 for detecting the exhaust gas temperature upstream of the catalyst 4 is used instead of the detection device of the first embodiment, and the other points are the same as in the previous embodiment. Then, by inputting the temperature (signal) T of the temperature sensor 12, the control unit 6 determines whether or not an operating state in which the exhaust gas temperature T is below a predetermined value has been performed for a predetermined time (or a predetermined number of times) or more. Judgment is made in the light of the operation history, and if the operation is performed for a predetermined time or more, it is considered that clogging has occurred, and is output to the actuator 11. That is, the temperature sensor T is used to know the engine operating history at low temperature of the engine, and this is used as a guide for the presence or absence of clogging of the catalyst 4, and the temperature sensor 12 and the control unit 6 constitute the clogging detection device 13. Can be said. In the second embodiment as well, as in the previous embodiment, the carbon in the particulates that is about to be clogged by the blow of the exhaust gas can be removed.

Although the exhaust throttle valve 5 is closed for a predetermined time in the first and second embodiments, it may be closed while the engine is rotating for a predetermined number of revolutions. .. In this case, in the low rotation speed operation state where the exhaust gas flow rate is small, the valve is closed for a long time, and even in the low speed rotation state, strong blow can be realized and the clogging can be effectively removed.

Further, even if the exhaust throttle valve is provided upstream of the catalyst, the same effect can be obtained.

[0024]

As described above, according to the present invention, when the exhaust emission control device is about to be clogged in the diesel engine, this can be automatically avoided.
It is possible to prevent the output, the deterioration of fuel consumption, and the situation of catalyst burnout, and moreover, this can be achieved with a cheap and simple device, whereby the exhaust gas of the internal combustion engine can be efficiently purified. The effect that it can be produced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a map of the differential pressure across the catalyst used in the embodiment of FIG.

3 is a flow chart of the embodiment of FIG.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Engine 2 Injection Pump 3 Exhaust Passage 4 Catalyst 5 Exhaust Throttle Valve 6 Control Unit 7 First Pressure Sensor 8 Second Pressure Sensor 9 Engine Speed Detection Device 10 Load Detection Device 11 Actuator 12 Temperature Sensor 13 Clogging Detection Device

Claims (1)

[Claims] 1. A purification device and an exhaust throttle valve are provided in an exhaust passage of a diesel engine, and a detection device for detecting a clogging state of the purification device, and a pressure detection valve for exhausting the exhaust throttle valve by a detection signal of the detection device. An exhaust emission control device for an internal combustion engine, which is provided with a control device that is opened after being closed for a predetermined period of time for raising the engine speed or for the engine speed.