JPH03194113A - Exhaust gas purifying device of engine - Google Patents

Abstract

PURPOSE:To prevent emission of harmful substances to outside till the temperature of a catalyst reaches the activation temperature by providing a communication passage with an adsorption placed in the middle so that it bypasses the catalyst provided in the middle of an exhaust passage and by switching and controlling the catalyst so that an exhaust gas passes the communicating passage when the catalyst is at a low temperature. CONSTITUTION:A catalyst 3 for purifying an exhaust gas is provided in the middle of an exhaust passage 4 connected to an exhaust manifold of an engine 1, and a rotary flow passage 5 provided with a chamber 6 filled with an adsorption 61 in the middle is connected to this exhaust passage 4 so that is bypasses the catalyst 3. A switch valve 8 is provided on this rotary flow passage 5 at the diverging position on the lower stream side than the catalyst at the exhaust passage 4, and a one-way valve 51 is provided on the rotary flow passage 5 on the lower stream side than the chamber 6. And when the temperature of the catalyst 3 does not reach the activation temperature and harmful substances in the exhaust gas is not fully purified, the switch valve 8 is switched so that the exhaust gas flows to the rotary flow passage 5 and purified by adsorbed to the absorption 61.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine exhaust purification device that uses a catalyst to reduce harmful substances discharged from an engine.

[Prior art and its problems] Conventionally, carbon monoxide (Co), hydrocarbons (HC), and nitrogen oxides (NO
Various measures have been taken to prevent the release of harmful substances such as x) into the atmosphere.

Generally, emissions are reduced by changing engine settings or controlling ignition timing and air-fuel ratio, and the exhaust is rendered harmless by a catalyst installed in the exhaust passage. 8 However, in recent years, there has been a desire for even cleaner exhaust gas, and there are concerns about improving catalyst activity and lowering the activity temperature.

Improvements in catalyst activity have been achieved by creating a highly active atmosphere by improving catalyst components and controlling the air-fuel ratio using an 02 sensor, but no effective measures have been taken regarding low-temperature activation. do not have.

In other words, the catalyst includes an oxidation catalyst that oxidizes CO and HC to render it harmless, and a catalyst that oxidizes CO and HC and simultaneously generates NOx.
Is there a three-way catalyst that reduces N2 to N2?The activity of all of them is highly temperature-dependent, and they are activated and purifying by being heated to a predetermined temperature by exhaust gas, so it is difficult to activate the catalyst. During a cold start when the temperature has not been reached, the purification (oxidation/reduction) action is not performed effectively, and therefore,
This has the problem that harmful substances are discharged as they are until the catalyst is heated to the activation temperature by the exhaust gas. In particular, HC, which is the main cause of generation whether it is an unburned component of gasoline or is emitted as is, is generated in large quantities during deceleration or cold start, or the oxidation catalyst has not reached the activation temperature. During a cold start, the anti-oxidizing effect is not carried out effectively and a large amount of HC is discharged.

In order to solve this problem, we have taken measures such as dividing the catalyst into multiple parts to reduce the mass of each one to make it easier to raise the temperature, and placing it closer to the engine to accelerate the temperature rise. However, it is still impossible to purify the catalyst until it reaches its activation temperature, and it must be said that it is still insufficient.

[Object of the Invention] In view of the above-mentioned circumstances, it is an object of the present invention to provide an engine exhaust purification device that can prevent the emission of harmful substances even before the catalyst reaches its activation temperature. do.

[Structure of the Invention] Therefore, the engine exhaust purification device according to the present invention uses an adsorbent or an intervening material between the upstream side and the downstream side of the exhaust passage in which the catalyst is interposed. A switching valve is provided at a branch position of the exhaust passage to the communication passage on the downstream side of the catalyst, and when the catalyst is at a low temperature,
The system is equipped with a control means for switching the switching valve to the communication path side, and the control means switches the switching valve to the communication path side to cause harmful substances in the exhaust gas to be adsorbed to the adsorbent, and to remove the harmful substances from the high-temperature exhaust gas. This system allows the adsorbed harmful substances to be desorbed from the adsorbent and refluxed to the catalyst side by flowing the adsorbent into the communication path.With this, when the catalyst is at a low temperature below the activation temperature, the switching valve is switched to the communication path. By switching to the side, harmful substances that are not purified by the catalyst are adsorbed by the adsorbent and are prevented from being discharged.

In addition, by flowing high-temperature exhaust gas into the communication passage after the catalyst reaches its activation temperature, harmful substances adsorbed by the adsorbent are desorbed and refluxed to the catalyst side, where they are purified by the catalyst and discharged. It is possible.

[Embodiments of the invention] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a conceptual diagram of an engine exhaust purification device according to the present invention.

The engine 1 is equipped with an exhaust manifold 2 (not shown) that collects and integrates exhaust pipes for each exhaust boat of each cylinder, and is connected to an exhaust passage 4 through the exhaust manifold 2.

A catalyst 3 is interposed in the exhaust passage 4 in the middle of the passage, and the exhaust gas from the engine 1 flowing through the exhaust passage 4 is purified by the catalyst 3 and further discharged to the outside via a silencer (not shown). It looks like this.

The upstream and downstream sides of the exhaust passage 4 with the catalyst 3 in between are connected by a reflux passage 5, and a switching valve 8 is provided at a branch position with the reflux passage 5 on the downstream side of the catalyst. .

A chamber halo filled with an adsorbent 61 is interposed in the middle of the reflux passage 5, and a one-way valve 51 is interposed on the upstream side of the exhaust passage 4 from the chamber 6. The adsorbent 61 has the property of adsorbing harmful substances in the exhaust gas and desorbing the adsorbed gas by being heated to a predetermined temperature. Secession is something that will take place. Further, the one-way valve 51 is provided to allow the flow to the upstream side of the exhaust passage 4 in the recirculation passage 5 and to block the flow in the opposite direction.

An introduction pipe 9 for introducing air (secondary air) from the outside into the chamber 6 is connected to the chamber 6, and an opening/closing valve 91 is provided in the introduction pipe 9. The opening/closing valve 91 is operated and driven by an actuator (not shown) which is controlled and operated by the control device 7 as a control means.

The switching valve 8, as shown in an enlarged perspective view in FIG.
It has a sector-like cross-sectional shape obtained by counting a cylinder of a predetermined height with a central angle of 120°, and its center is located at the branch point of the exhaust passage 4 and the recirculation passage 5, which are formed in a rectangular cross-sectional shape and have the same height as the switching valve 8. It is installed so as to be rotatable around the center of rotation, and rotates 120 degrees counterclockwise in the figure from the state shown in FIG. Then, the reflux passage 5 shown in FIG. 3(B)
is completely closed and the exhaust passage 4 is opened (θ=
120°).

The switching valve 8 is rotatably driven by an actuator (not shown), and the actuator is controlled and operated by the control device 7. Therefore, the switching valve 8 is controlled and driven by the control device 7. It is something.

The control device 7 includes a catalyst temperature sensor 7 provided in the catalyst 3.
1. Information is input from an adsorbent temperature sensor 72 and an ignition switch 73 provided in the chamber.

Based on the input information from the catalyst temperature sensor 71, the adsorbent temperature sensor 72 provided in the chamber, and the ignition switch 73, and the elapsed time after starting, the control device 7 performs the following operation as shown in FIG. As shown in the flowchart of A), the opening degree (θ) of the switching valve 8 and the opening/closing valve 91 provided in the introduction pipe 9 are controlled and driven, and if the catalyst 3 does not reach the activation temperature (approximately 500°C) and is being exhausted. When the harmful substances are not sufficiently purified, the exhaust gas is flowed into the recirculation passage 5 and the harmful substances are adsorbed and purified by the adsorbent 61.
After the catalyst 3 has reached its activation temperature and the exhaust gas has been sufficiently purified, the high-temperature exhaust gas is passed through the recirculation passage 5 to desorb the harmful substances adsorbed by the adsorbent 61, and the catalyst 3 The purpose is to purify and discharge the waste.

That is, at the time of starting (when the ignition is ON), the switching valve 8 is set to <o=o6 as shown in FIG.
2). As a result, the exhaust gas flows to the reflux passage 5 side, and the catalyst 3
Harmful substances that have not been purified are adsorbed by the adsorbent 61 in the chamber.

Then, until the convenient time after startup: t (=40 seconds) has elapsed, as shown in the following equation, the switching valve opening degree: θ calculated based on the elapsed time after startup: t, and the catalyst temperature sensor 71 The switching valve opening degree θ2 calculated based on the temperature of the catalyst 3 measured +TcaL is compared, and the larger one is set as the opening degree of the switching valve 8: θ. (33 to S7) In other words, equation (1) is based on the elapsed time after startup, t, which is 0-0 at startup, and θ = 120° when 40 seconds have passed after startup (exhaust passage 4 θ is calculated so that the reflux passage 5 is opened and the reflux passage 5 is completely closed. In addition, equation (2) is based on the catalyst temperature: Tcat, and θ is adjusted so that θ=120° when the catalyst temperature reaches 2Teat or its activation temperature of 500°C.
2 is calculated. In addition, if the catalyst temperature T cat is 5
The rate of temperature increase until it reaches 00'C is approximately constant, as can be seen from FIG.

T cat is approximately proportional to the elapsed time after starting: t. (T, = nXt, where n is a constant) When a predetermined time (t, = 40 seconds) has elapsed after starting, the opening degree of the switching valve 8 is set to θ = 120', the recirculation passage 5 is completely closed, and the exhaust passage 4 is opened. (S8). At this time, catalyst temperature: Tca
l has reached the activation temperature, and the exhaust gas discharged to the outside is purified by the catalyst 3.

Thereafter, when the temperature of the adsorbent 61 in the chamber (adsorbent temperature TX) detected by the adsorbent temperature sensor 72 reaches 400°C, which is the desorption temperature of the adsorbent residue, the opening degree of the switching valve 8 changes to 20°C. seconds (12=20 seconds) and θ=606 as shown in FIG. 3(C). (SIO, 512) As a result, a part of the high-temperature exhaust gas is directed toward the reflux passage 5 side, and the adsorbed gas desorbed from the adsorbent 61 moves along with this exhaust gas within the reflux passage 5 toward the exhaust passage 4 side upstream from the catalyst 3. (the reflux passage 5 or the exhaust passage 4 upstream of the connected catalyst 3)
Because the exhaust gas flows inside the tube at high speed, a pressure difference is created and reflux occurs. Further, the flow in the opposite direction is blocked by the one-way valve 51), and is purified by the catalyst 3 and is wasted.

In addition, for 20 seconds when the opening degree of the switching valve 8 is set to θ=60°, the adsorbent temperature/TX is kept at 400° as shown in FIG. 4(B).
Control to maintain the temperature at 400°C (TX400°C control: 511) is performed. That is, when the adsorbent temperature Tx reaches 400°C or higher, the on-off valve 91 of the introduction pipe 9 is opened to introduce secondary air into the chamber 6, and the adsorbent temperature Tx reaches 400°C.
If the condition is below, the on-off valve 91 is closed and the introduction of secondary air is stopped. As a result, the adsorbent 61
The adsorbed gas can be quickly and efficiently desorbed from the gas.

The connection or branching configuration between the exhaust passage 4 and the recirculation passage 5 is as follows: -
The present invention is not limited to the embodiments described in . For example, catalyst 3
At the point where the recirculation passage 5 branches from the exhaust passage 4 on the more downstream side, as shown in Figure 6, the exhaust passage 4 or the passage 4' in the discharge direction and the recirculation passage 5 have a gentle angle of 2 degrees, but an equal angle in both directions. If you make it branch,
The flow of exhaust gas toward the recirculation passage 5 side becomes smoother. In this case, it goes without saying that the shape of the switching valve and its operating angle must be changed from those in the first embodiment. or,
The part where the recirculation passage 5 joins the exhaust passage 4 on the upstream side of the catalyst 3 is designed so that when the inner passages 4 and 5 merge, the thickness becomes the sum of both, as shown in Fig. 7 (A). (B
) It would also be effective to construct the inner passages 4.5 so that they meet at the same angle.

Furthermore, the control of the switching valve 8, which causes the exhaust gas to flow into the recirculation passage 5 side so that harmful substances are adsorbed onto the adsorbent 61, is not limited to the cold start, but also during high loads, when many harmful substances are discharged, and the catalyst treatment is performed. You may also do this when your ability is exceeded. In this way, the capacity of the catalyst can be reduced.

[Effects of the Invention] As described above, according to the engine exhaust purification device according to the present invention, harmful substances that are not purified by the catalyst are adsorbed by the adsorbent until the catalyst reaches the activation temperature. , which can prevent emissions.

Furthermore, by flowing high-temperature exhaust gas through the communication passage after the catalyst reaches its activation temperature, harmful substances adsorbed by the adsorbent can be desorbed and refluxed to the catalyst side, where they can be purified by the catalyst.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an engine exhaust purification device according to the present invention, Fig. 2 is an enlarged perspective view of the switching valve, and Fig. 3 is an enlarged view showing the switching state of the switching valve.
0° diagram, (B) is 0-1206 diagram, (C) is 0=6
0° diagram, Figure 4 (A)' Control flow chart, Figure 4
Figure (B) is a control flowchart for maintaining the adsorbent temperature at 400°C, Figure 5 is a graph showing changes in the opening degree of the switching valve 8 with respect to operating time, and Figure 6 is a graph showing the location where the recirculation route branches from the exhaust passage. A diagram showing another embodiment, FIG. 7(A)
, (B) is a diagram showing another embodiment of a portion where a recirculation route joins an exhaust passage. 4 ■...Engine 3...Catalyst 4...Exhaust passage 5...Recirculation passage (communication passage) 7...Control device (control means) 8...Switching valve blower 1...Adsorbent

Claims (2)

[Claims] (1) An upstream side and a downstream side of an exhaust passage in which a catalyst is interposed in the passage, with the catalyst interposed therebetween, are communicated by a communication passage in which an adsorbent is interposed, and the catalyst in the exhaust passage is An exhaust gas for an engine, characterized in that a switching valve is provided at a branch position to the communication path on the downstream side, and a control means is provided for switching the switching valve to the communication path side when the catalyst is at a low temperature. Purification device. (2) An upstream side and a downstream side of an exhaust passage in which a catalyst is interposed in the passage, with the catalyst interposed therebetween, are communicated by a communication passage in which an adsorbent is interposed, and the catalyst in the exhaust passage is A switching valve is provided at a branch position to the communication path on the downstream side, and a control means is provided for switching the switching valve to the communication path side, and the control means switches the switching valve to the communication path side, so that the exhaust gas is It is characterized by being configured such that the harmful substances are adsorbed on the adsorbent, and the adsorbed harmful substances are released from the adsorbent by flowing high-temperature exhaust gas to the communication path side and refluxed to the catalyst side. Engine exhaust purification device.