JPS637251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a particulate purification device for removing particulates contained in the exhaust gas of an internal combustion engine and preventing the particulates from being released into the atmosphere, and is particularly applicable to diesel engines. The present invention provides an effective particulate purification device.

Diesel engines have come to be widely used as vehicle engines because of their good thermal efficiency.
However, on the other hand, diesel engines emit a larger amount of particulates, so-called smoke, than gasoline engines. The main component of these fine particles is unburned carbon particles, which adsorb and hold compounds harmful to the human body such as unburned hydrocarbons, sulfur oxides, and nitrogen oxides on their surfaces, and the particle size is small. Because they are extremely small (less than a few microns), if they are released into the atmosphere, they remain suspended in the air for a long time and are easily inhaled deep into the lungs. Therefore, as the number of vehicles equipped with diesel engines increases, concerns are beginning to be raised about the harmful effects of exhaust particulates on the human body. Additionally, some countries are trying to regulate particulate emissions from vehicles equipped with diesel engines to below a certain level. Under these circumstances, there is a strong desire to develop a particulate purification device.

Conventionally, as this type of device, a device has been devised in which a heat-resistant filter member, such as a porous ceramic or metal fiber, is installed in the exhaust system of an engine, and fine particles are attached to and collected on the filter member. However, in these devices, as particles accumulate on the filter surface, the ventilation resistance of the filter increases and particles start to fall off the filter surface, so it is necessary to heat the collected particles at appropriate intervals. Measures have been taken to regenerate the filter by incinerating it. A burner such as a gas burner is used as a heating means for filter regeneration. When heating with this burner, if exhaust gas having a temperature lower than the heating temperature flows during heating, the heating efficiency is poor and a large amount of heat is required.
Therefore, in order to reduce the amount of heat, two sets of filters are installed, and a flow path switching valve is installed on the upstream or downstream side of the filters. During filter regeneration, exhaust gas is prevented from flowing into the heating filter, and the exhaust gas is transferred to the other filters. Means were devised to allow the exhaust gas to flow in and to do this alternately. However, this method uses two filters.
The disadvantage is that the entire device becomes very large because it is installed in sets. In particular, internal combustion engines equipped with exhaust gas recirculation devices that recirculate part of the exhaust gas back into the intake system to reduce nitrogen oxides ( _NO It is known that the amount of fine particles in the exhaust gas increases to about twice the normal amount. accordingly
An engine equipped with an EGR device requires a large filter capacity, and if two sets of filters are provided, the device becomes larger.

Therefore, it is an object of the present invention to provide a device that is compact, easy to install in a vehicle, and can reduce particulate emissions in an internal combustion engine equipped with an EGR device. The installed filter, a bypass flow path that discharges exhaust gas without passing through the filter, a switching valve that selectively switches the flow of exhaust gas to the filter and bypass flow path, and the particulates collected by the filter are combusted. It is equipped with a control mechanism that controls the burner, switching valve, burner, and control valve (EGR valve) that adjusts the amount of EGR.When regenerating the filter, the exhaust gas is circulated to the bypass flow path and the burner is activated. By heating the filter to incinerate and remove particulates on the filter, and lowering the EGR amount than normal.
This reduces particulate emissions while hardly increasing _NOx emissions.

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a configuration diagram showing one embodiment of the present invention.
is a diesel engine body of a vehicle, in which air is taken in through an air cleaner 2, an intake pipe 3, and an intake manifold 4, and fuel is injected from a fuel injection pump 5. Exhaust gas passes through an exhaust manifold 6 and is discharged from an exhaust pipe 7.

The exhaust pipe 7 includes a first exhaust pipe 7a and a second exhaust pipe 7.
A filter member 8 for collecting particulates in the exhaust gas is installed in the first exhaust pipe 7a. The filter member 8 is made of, for example, porous ceramics, metal fiber, or the like. An exhaust gas flow path switching valve 9 is provided at the branch portion of the first and second exhaust pipes 7a, 7b. Further, a burner 10 is provided upstream of and close to the filter member 8. In this burner 10, fuel and air are supplied from a fuel supply device and an air supply device (neither of which are shown), and a mixture is prepared and combusted.

A pipe line 11 for exhaust gas recirculation (hereinafter referred to as
One end (referred to as an EGR pipe) is connected to the EGR pipe, and the other end is connected to the intake pipe 3. A valve 12 (hereinafter referred to as an EGR valve) is provided in the middle of the EGR pipe 11 to adjust the flow rate of exhaust gas returned to the intake pipe 3.

13 is a control device, which includes an actuator 14 that drives the switching valve 9, an EGR valve 12,
It acts to control the burner 10 etc. A vacuum pump 15 is installed in the intake manifold 4 and generates negative pressure to operate the EGR valve 12. The fuel injection pump 5 has an injection amount adjustment rack (not shown), and an electric signal indicating the position of the rack is sent to the control device 13 via a transmission line 16. The main body 1 includes a device 17 for detecting the rotation speed of the engine.
is provided, and the rotational speed is sent to the control device 13 by an electrical signal. The above vacuum pump 15 and EGR
The pulp 18 communicating with the valve 12 is provided with an electromagnetic valve 19 that adjusts the negative pressure supplied from the vacuum pump 15 to the EGR valve 12, and this electromagnetic valve 19 is opened and closed by a pulse signal sent from the control device 13. be done. The pipe 18 is provided with a throttle channel 20 whose one end communicates with the atmosphere,
It functions to gradually release the negative pressure in the negative pressure chamber 12a of the EGR valve 12.

Next, to explain the operation of this embodiment, normally, the switching valve 9 opens the first exhaust pipe 7a, the entire amount of exhaust gas flows through the filter member 8, and particulates in the exhaust gas are captured. collected. Furthermore, a portion of the exhaust gas is metered by the EGR valve 12 from the EGR pipe 11 and recirculated to the intake pipe 3, thereby reducing _NOx emissions.

When the travel distance or fuel consumption of the vehicle reaches a predetermined value, the switching valve 9 is rotated in response to a signal from the control device 13, and the second exhaust pipe 7b forming a bypass flow path is opened, allowing exhaust gas to flow in. At the same time, the burner 10 starts combustion, and the filter member 8
is heated, and the collected particles are incinerated and removed.

By the way, during filter regeneration by incinerating and removing particulates, the particulates in the exhaust gas are not removed and are discharged from the second exhaust pipe 7b together with the exhaust gas. In particular, diesel internal combustion engines equipped with an EGR device emit about twice as much particulate matter as those without. Therefore, control for reducing the amount of exhaust gas recirculation (hereinafter referred to as EGR amount) in order to suppress the amount of particulate emissions during filter regeneration will be explained.

Map type control is usually used as an EGR amount control means for diesel internal combustion engines. Map-type control uses two parameters: the engine speed and the load, i.e., the easy position of the injection pump, to predetermine the opening degree of the EGR valve for all combinations of these parameters, and stores this electrically in the control device. During actual driving, the engine speed and rack position are constantly detected, and the EGR valve is controlled to open and close to the degree of opening determined by these factors.

In the above embodiment of the present invention, the EGR valve opening degree is controlled by adjusting the pulse width of the electric pulse periodically sent from the control device 13 to the electromagnetic valve 19. That is, as the pulse width becomes longer, the negative pressure in the EGR valve negative pressure chamber 12a becomes higher, the lift amount of the valve increases, and the EGR amount increases. Therefore, by electrically storing the electric pulse width corresponding to the engine speed and the rack position in advance, it becomes possible to control the EGR amount appropriately. In the following explanation, the relationship between the engine state and the electrical pulse width will be referred to as a map.

To reduce the EGR amount during filter regeneration,
Map A that determines the amount of EGR in normal conditions and EGR
By preparing map B that reduces the amount and controlling with map B during filter regeneration,
Appropriately lower the EGR amount. If necessary, EGR may not be performed during filter regeneration. Note that if the EGR amount is reduced during filter regeneration, the amount of particulate emissions will decrease, but the amount of _NOx emissions will increase. The specific degree to which the amount of EGR is reduced is determined by the characteristics of each individual engine.

FIG. 2 is a time chart showing the operation of the device, in which the flow of exhaust gas is switched from the first exhaust pipe 7a provided with the filter member 8 to the second exhaust pipe 7b of the bypass passage, and at the same time the burner 10 The combustion action is performed, and the EGR amount control is switched from control by MAP A to control by MAP B.
Then, the burner 10 stops its operation after supplying the amount of heat necessary to burn and remove the particulates collected by the filter member 8, and when the time required for the amount of heat to burn and remove the particulates has elapsed, the exhaust gas flow is changed. As the path is switched to the filter member 8 side,
EGR amount control is switched from map B to map A.

Figure 3 shows the relationship between the EGR amount, _NOx emission amount, and particulate emission amount, and shows the relationship between the EGR amount, NOx emission amount, and particulate emission amount. If bypassed, a large amount of fine particles will be emitted as black smoke, but if the map B is used to control the filter during filter regeneration, especially switching to the area C shown in the diagram, _NOx emissions will not increase significantly. ,
The amount of particulate emissions can be reduced. here,
The overall increase in _NOx emissions can be estimated using the following estimate.

The particulate purification device according to the present invention can be used for approximately 200Km to 300Km.
The filter is regenerated every time the vehicle travels for Km, for example every 3 to 5 hours at 60 Km/hour, and the regeneration time is approximately 3 to 4 minutes. And when playing the filter
Even if we assume that the amount _{of NO}
It is approximately 2.2%, and the influence of filter regeneration operation on the environment can be suppressed to an almost negligible level. In addition, the amount of _NOx emissions under normal conditions
If the EGR amount is reduced by about 2% by adjusting the EGR amount, the increase in _NOx emissions during filter regeneration can be almost completely eliminated as a total amount of emissions.

As described above, in the present invention, exhaust gas is discharged without passing through the filter member during filter regeneration. For this reason, it is preferable that the filter regeneration time be as short as possible in order to reduce the amount of fine particles discharged. Therefore, the present invention provides a means that enables filter regeneration in even shorter time.

Since most of the particles collected by the filter member are carbon particles, they can be incinerated and removed by heating at about 600°C. On the other hand, the combustion gas temperature of the burner is about 1400°C at the burner outlet and about 1000°C at the filter inlet, which is considerably higher than the necessary heating temperature. In addition, the flow rate of burner combustion gas is the calorific value per hour.
In the case of 3000 kilocalories, it is approximately 65 per minute at room temperature.
, for 10000 kcal per hour, similarly per minute
It is about 220. Thus, the burner combustion gas is higher than the required filter heating temperature and the flow rate is low. As a result, it takes a considerable amount of time to heat up the downstream side of the filter member, and the filter temperature decreases.
The temperature is higher than necessary, reaching 800℃ to 1000℃.

Therefore, the present invention mixes an appropriate amount of exhaust gas into the burner combustion gas to lower the temperature of the burner combustion gas flowing to the filter member and increase the flow rate, thereby preventing the filter member from being heated more than necessary. Moreover, the filter member can be regenerated quickly.

An embodiment of this exhaust gas mixing means is shown in FIGS. 4 and 5. In the embodiment shown in FIG. 4, a switching valve 9 that switches the gas flow path to the first and second exhaust pipes 7a and 7b is provided with a large number of small diameter holes 9a, and these holes are used during filter regeneration. supply of exhaust gas. The hole diameter may be approximately 0.5 mm to 3.0 mm. In the embodiment shown in FIG. 5, a gap 21 is provided between the switching valve 9 and the switching valve housing forming part of the exhaust pipe 7. In the embodiment shown in FIG. However, the hole 9 above
An appropriate amount of exhaust gas is replenished into the burner combustion gas through a or the gap 21 during filter regeneration, the amount of combustion gas increases, the entire filter member can be quickly heated to 600°C or more, and the filter regeneration time can be shortened. .

Next, an embodiment in which the particulate purification device of the present invention is incorporated into an exhaust manifold of an internal combustion engine will be described.

In the embodiments shown in FIGS. 6 and 7, exhaust gas inlets 22a, 22b, 22c, and 22d are formed in the upper part of the storage container 22, corresponding to each cylinder of the engine. The inside of the container is partitioned into upper and lower parts by a partition wall 23, and the upper chamber forms an exhaust collection part. A communication hole 24 is provided in the partition wall 23 to communicate the upper and lower chambers. Filter members 8a and 8b are arranged side by side in the lower chamber, a space 25 is formed between the filter member 8a and the inner wall of the container, and a space 25 is formed between the filter member 8b and the container wall to communicate with the communication hole 24. A space 26 forming a gas flow path switching section is formed, and the space 25 communicates with the gas flow path switching section 26 through an opening 27 via a flow path (not shown). Further, a burner 10 is installed at the bottom of the gas flow path switching section 26, and an exhaust pipe 7 is connected to the side wall. The exhaust pipe 7 is connected to an EGR pipe (not shown) at a branch 28. A switching valve 9 is installed in the gas flow switching section 26 and operates to selectively communicate the communicating hole 24 to either the filter members 8a, 8b side or the exhaust pipe 7 side.

Figure 6 shows the normal state in which exhaust gas flows through the filter member, and the exhaust gas passes through the filter members 8a and 8b from the communication hole 24 as shown by the white arrow, and particulates are collected by the member. The exhaust gas passes through a flow path and an opening 27 (not shown) to the exhaust pipe 7.
more excreted. A part of it is also circulated to the EGR quantity device.

Figure 7 shows the state during filter playback.
The switching valve 9 is switched and the exhaust gas is transferred to the communication hole 2.
4, flows through the flow path switching section 26 to the exhaust pipe 7. At this time, the burner 10 is activated to supply combustion gas to heat the filter members 8a, 8b, thereby burning and removing the particulates collected by the filter members 8a, 8b. Note that during this filter regeneration, the EGR amount control is switched to map B.

Next, FIG. 8 shows another embodiment, and in the embodiment shown in FIGS. 6 and 7, the exhaust gas outlet 28 to the EGR pipe connects the exhaust gas with the filter members 8a and 8b. In this embodiment, the EGR pipe 11 is provided at the part where the heated burner combustion gas joins, whereas in this embodiment, the EGR pipe 11 is provided in the space 25 which is the outlet of the burner combustion gas that heated the filter members 8a and 8b.
is connected. The other structure is substantially the same as the above embodiment.

In other words, in this embodiment, EGR during filter regeneration is
The gas can be mostly burner combustion gas. Burner combustion gas has a higher concentration of carbon dioxide than engine exhaust gas, and when used as EGR gas, _NOx can be effectively reduced with a small amount. At the same time, since only a small amount of EGR gas is required, the increase in particulate emissions can also be reduced.

As explained above, in the present invention, the increase in the amount of particulate emissions during filter regeneration is avoided by controlling the EGR amount to be smaller than normal during filter regeneration to burn and remove particulates collected on the filter member. Can be walled. Furthermore, by replenishing the burner combustion gas with an appropriate amount of exhaust gas during filter regeneration, filter regeneration control can be shortened. Furthermore, by using burner combustion gas as the EGR gas, a significant increase in particulate emissions and _NOx emissions can be avoided.

Therefore, the present invention provides extremely effective and practical means for preventing black smoke emissions in internal combustion engines, particularly diesel internal combustion engines.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an internal combustion engine using the particulate purification device according to the present invention, Fig. 2 is a diagram showing a time chart of the device operation, and Fig. 3 is the relationship between EGR amount, particulate emissions, and NO _x emissions. Figure 4 showing
5 and 5 are views showing an embodiment of the gas flow path switching valve of the device of the present invention, and FIGS. 6 to 8 respectively.
Each of the figures is a sectional view showing a main part of an embodiment of the device of the present invention. 1... Internal combustion engine main body, 6... Exhaust manifold, 7... Exhaust pipe, 7b... Bypass flow path, 8,
8a, 8b...Filter member, 9...Gas flow path switching valve, 10...Burner, 11...Exhaust gas recirculation pipe, 13...Device operation control device.

Claims (1)

[Claims] 1. An exhaust gas recirculation device that recirculates part of the exhaust gas to the intake system is provided, and the exhaust pipe is equipped with a particulate collection filter that collects particulates whose main component is carbon in the exhaust gas. In a carbon particulate purification device for an internal combustion engine equipped with a burner that heats and burns off the particulates collected by the filter and regenerates the filter, a bypass flow is provided in which exhaust gas is discharged into the exhaust pipe without passing through the filter. In addition to providing a passage, a passage switching valve is provided either upstream or downstream of the filter to switch the route of the exhaust gas, and under normal conditions, the exhaust gas flows through the filter and the amount of particulates collected by the filter is set to a predetermined value. A control mechanism is provided that operates a switching valve to switch the exhaust gas flow path to the bypass flow path and operates the burner, and controls the amount of exhaust gas recirculation to a smaller amount than normal. A Kabon particulate purification device for internal combustion engines, which is characterized by: 2. The carbon particulate purification device for an internal combustion engine according to claim 1, wherein the flow path switching valve is provided with a gap through which a minute amount of exhaust gas flows.