JPH11294138A - Exhaust purification device for diesel engine and flow switching valve for the device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When regenerating a particulate trap for a diesel engine by a method of burning particulates collected by a trap using oxygen in exhaust gas,
The purpose is to allow the amount of exhaust gas flowing into the trap to be switched according to the operating condition of the engine. SOLUTION: A discharge port and a leak port are provided in a flow path switching valve 1, and these ports are selectively opened and closed by a first valve body and a second valve body. A first orifice is provided in the first valve body, and a second orifice is provided in the second flow path 24 from the leak port. When the discharge port is closed to regenerate the trap 23, the first orifice is throttled. The exhaust gas is caused to flow from both the first flow path and the second flow path via the second orifice. When the second flow path 24 connected to the leak port is opened and closed by the gate valve 25 according to the operating condition of the engine, the amount of exhaust gas passing through the trap 23 is reduced by the gate valve 25.
Hirakiji is Q ₁ + Q _2, the gate valve 25 is closed is changed in two steps becomes Q _1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for a diesel engine which collects particulates in exhaust gas by a trap and burns the collected particulates using oxygen in the exhaust gas. And a flow path switching valve used in the purification device.

[0002]

2. Description of the Related Art Diesel engine exhaust gas contains
It contains various components that cause air pollution. One of the components is flammable fine particles mainly composed of carbon. The fine particles are particulate matter (hereinafter P
M). Of course, improvement of the engine has been promoted to remove this PM, but as a more reliable removal method, a trap (diesel particulate filter) is installed in the exhaust system to purify the PM by trapping it. An apparatus is conceivable (JP-A-58-512).
No. 35), some of which have already been put to practical use.

[0003] In this apparatus, it is necessary to regenerate the trap by burning the collected PM periodically. The combustion regeneration is conditionally difficult when exhaust gas is being introduced from the engine, and it is not possible to stop the engine halfway, so the exhaust path is branched into multiple sections and trapped in each branch path. A method is adopted in which a plurality of traps are used to alternately collect and burn PM.

When this method is adopted, the branch path on the side where combustion and regeneration is performed is shut off by a valve to guide exhaust gas to the branch path on the side where PM is collected, but when the branch path on the regeneration side is completely closed, When the collected PM is heated by a heater and burned, the amount of oxygen becomes insufficient and the combustion becomes incomplete. For this reason, Japanese Patent Application Laid-Open
No. 6-92318 proposes a device in which an orifice hole is made in a flap valve closing a regeneration-side branch, and a part of exhaust gas flows through the regeneration-side branch. Also, Japanese Patent Application Laid-Open No. 7-224
No. 633 proposes forcing air from outside into the regeneration side branch.

[0005]

Problems to be Solved by the Invention
The apparatus disclosed in Japanese Patent Publication No. 3 requires an air pump, a valve for opening / closing an introduction path, and control means for them, and is complicated and expensive.

On the other hand, the apparatus disclosed in Japanese Patent Application Laid-Open No. 56-92318 promotes combustion by using oxygen in exhaust gas, so that the apparatus can be simplified and the cost can be reduced. Since the orifice hole is simply formed, the amount of exhaust gas introduced cannot be controlled according to the operating condition of the engine. That is, the amount of gas passing through the orifice is determined by the differential pressure across the orifice. Therefore, as the engine speed increases, the amount of exhaust gas introduced into the regeneration trap increases. Further, the oxygen concentration in the exhaust gas tends to increase when the load on the engine is small. For this reason, the amount of oxygen required for PM combustion may be too small or too large, and the combustion becomes unstable and the trap regeneration efficiency deteriorates.

Therefore, the present invention relates to an exhaust gas purifying apparatus and an exhaust purifying apparatus capable of switching the amount of exhaust gas introduced into a regenerating trap into two stages according to the operating condition of an engine so as to optimize oxygen supply. It is an object to provide a flow path switching valve for use.

[0008]

SUMMARY OF THE INVENTION An exhaust gas purifying apparatus of the present invention has a first flow path and a first flow path upstream or downstream of a trap so that the amount of exhaust gas introduced into the trap can be switched in two stages. Two flow paths are provided, and a flow path switching valve having an orifice is disposed at a branch of the first flow path and the second flow path, and a gate valve is disposed in the second flow path. The passage switching valve restricts the passage of the exhaust gas in the first flow passage and allows the exhaust gas to flow to the second flow passage at the same time.

A flow path switching valve used in this device includes a valve body having an exhaust introduction port, an exhaust port, a leak port, and a valve chamber communicating the ports, and an exhaust port opening / closing valve provided in the valve chamber. A first valve body and a second valve body for opening and closing the leak port, an input shaft for applying a displacement force to the first and second valve bodies, a first orifice provided in the first valve body, and a second flow from the leak port. A second orifice for restricting a passage, wherein a discharge port and a leak port are selectively opened and closed by rotation of the input shaft, and when the discharge port is closed, exhaust gas passes through a first flow path restricted by the first orifice. The gas flows from the chamber to the discharge port, and further flows from the valve chamber to the second flow path via the second orifice.

[0010] The second orifice of the switching valve is preferably provided with a detachable separate component, and provided on the separate component. It is also preferable to attach a nipple to the plug joint for connecting the second flow path and provide a second orifice in the nipple.

In the exhaust gas purifying apparatus of the present invention, a trap for collecting particulates in exhaust gas and a switching valve with a leak port as described above are provided in each of the branch paths of the engine, and a branch valve is provided in each branch path. If the second flow paths connected to the leak ports of the switching valves are merged into one, and the merged second flow path is provided with a gate valve for opening and closing the second flow path, the size can be reduced. In this case, the first flow path, the second flow path, and the flow path switching valve need to be arranged on the downstream side of the trap.
It is also possible to arrange a gate valve in each of the second flow paths and provide these elements upstream of the trap.

[0012]

Assuming that the gas amount passing through the first orifice is Q ₁ and the gas amount passing through the second orifice is Q ₂ , the gas flow rate when the discharge port is closed is Q = Q ₁ + Q ₂ . Further, it the second flow path is closed by the gate valve Q = Q ₁ becomes, can be switched in two steps passing flow at opening and closing of the gate valve.

By this switching, the amount of oxygen supplied to the regeneration trap can be made closer to the ideal value to stabilize the PM combustion and the trap regeneration efficiency can be improved.

If the second orifice is provided on another detachable part, it is possible to replace the part to cope with a change in the orifice diameter according to the specifications and operating conditions of the engine. Further, providing the second orifice in the nipple described above requires only a small part cost, which is economically advantageous.

Further, the exhaust gas purifying apparatus in which the second flow path from each flow path switching valve is integrated and the second flow path is opened / closed by one gate valve is provided. The device can be reduced in size and weight, and it is also economical.

[0016]

FIG. 1 shows an embodiment of a flow path switching valve used in an exhaust gas purification apparatus of the present invention. The flow path switching valve 1 is provided with a first valve body 3, a second valve body 4, and a support arm 5 for both valve bodies in a valve body 2.

The valve body 2 has an exhaust inlet port 6, a valve chamber 7, a discharge port 8 connected to the inlet port 6 through the valve chamber 7, and a direction different from the discharge port 8 from the valve chamber 7 (approximately 90 in the figure). (A different direction, but not limited to 90 °) is provided. The first valve body 3 is provided with a first orifice 10, and the leak port 9 is provided with a second orifice 11. The diameters of the orifices 10 and 11 are appropriately determined in consideration of the specifications of the engine and the like.

The support arm 5 is installed in the valve chamber 7 and supports an input shaft 12 serving as a center of rotation by the valve body 2.
One end of the input shaft 12 is outside the valve body 2, and a rotational force is applied thereto from an actuator (not shown) such as an air cylinder to rotate the support arm 5 forward and reverse.
The flow path is switched.

The first valve element 3 is provided on one side of the support arm 5.
The second valve body 4 is brought into spherical contact with the other surface side of the arm, and a gap (play) is formed between the center support shaft 13 and the arm 5 to allow the support shaft 13 to be tilted. It is mounted so that it has a degree of freedom of inclination. These valve bodies 3, 4
Is made of a material having excellent heat resistance and corrosion resistance (such as a ceramic or a metal having increased corrosion resistance), and makes the flat sealing surfaces 3a, 4a face-to-face with the corresponding flat valve seats 14, 15. In order to ensure that the sealing by the surface contact is performed without being restricted by the support arm 5, each of the valve bodies 3, 4
Is given a degree of freedom of inclination so that the sealing pressure is evenly applied to each part of the sealing surface.

The valve body used is preferably one having an exemplary structure which is excellent in sealability and durability and can be used safely even in a high-temperature corrosive environment. It is not an essential requirement that the valve element has a degree of freedom of inclination. For example, instead of a flap valve having a first orifice formed at a position off the leak port 9, the discharge port 8 may be selectively closed on one side of the flap valve and the leak port 9 may be selectively closed on the other side. The object of the invention is achieved.

As shown in FIG. 2, reference numeral 16 denotes a part which has a mating surface sealed with a packing 17 and which is removably bolted to the valve body 2. The part 16 includes a leak port 9 and a second port. An orifice 11 and a valve seat 15 are provided. Therefore, the request for changing the diameter of the second orifice can be dealt with by exchanging the component 16, but the second orifice 11 may be integrally formed with the valve body 2. Also,
A joint (not shown) may be provided at the joint with a joint (not shown) in the middle of the pipe 18 serving as the second flow path, or as shown in FIG.
Nipple 20 which is detachably screwed into the hole of plug joint 19
May be added to the nipple 20, and in this case also, the orifice diameter can be changed by replacing parts.
The structure shown in FIG. 3 can be replaced with a small and inexpensive nipple, so that the economic burden is small.

Next, FIG. 4 shows an embodiment of an exhaust gas purifying apparatus of the present invention employing the flow path switching valve of FIG.

As shown in the figure, the main exhaust pipe 21 of the diesel engine is branched into a plurality of parts on the way, and each branch path 22a,
The trap 23 and the flow path switching valve 1 are respectively assembled in series in 2b... 22n. The trap 23 has a filter and a PM combustion heater (both not shown) in the trap container.
Which may be a known one. Various types of traps have been proposed, such as a porous metal body having excellent heat resistance and corrosion resistance (for example, Celmet (trade name) or metal nonwoven fabric manufactured by Sumitomo Electric) or a filter and heater made of a porous ceramic body. And you can use such.

The flow path switching valve 1 is disposed downstream of the trap 23 as shown in the figure. Further, the second flow paths 24 from the respective switching valves are merged into one and connected to the downstream main exhaust pipe 21. A gate valve 25 for opening and closing the flow path 24 is inserted in the middle of the second flow path 24 that has been merged into one.

As the gate valve 25, the first orifice 10 of the valve shown in FIG. 1 is omitted, and a blind plug is screwed into the component 16 to kill the leak port 9. Any structure can be used as long as it can be opened and closed, and another structure can be used.

In the exhaust gas purifying apparatus configured as described above, for example, the switching valve 1 of the branch passage 22n is set to close the discharge port and open the leak port, and the switching valves 1 of the other branch passages are set to close the leak port and open the discharge port. While trapping PM in a trap in another branch while trapping PM in a branch 22n.
Regeneration by PM combustion of No. 3 can be performed.

At this time, the amount Q of exhaust gas flowing through the trap during regeneration is changed by opening and closing the gate valve 25 so that the gate valve is opened: Q = Q ₁ + Q ₂ , and the gate valve is closed Q
= It can be changed in two stages of Q _1. Q ₁ is the first
Gas flow through orifice 10 (see FIG. 1), Q ₂ is second
This is the amount of gas passing through the orifice 11 (see FIG. 1).

Note that a plurality of traps 23 can be reproduced at the same time.

Further, the exhaust gas purifying apparatus of the present invention may be configured such that the flow path switching valve 1 is disposed upstream of the trap 23 as shown in FIG. In this case, the second flow path 2
4 cannot be merged into one, so a gate valve 25 is provided in each second flow path 24. Also in this structure, the flow rate of the exhaust gas introduced into the trap being regenerated by opening and closing the gate valve 25 can be switched in two stages.

(Embodiment) As an exhaust gas purifying apparatus used in a route bus (4 cycle, direct injection type diesel engine, displacement: 11.149 liters), an apparatus having a structure shown in FIG. 4 in which four traps are incorporated in an exhaust system. Was prototyped.

As the trap 23, a combination of a porous metal filter and a 1.5 kW regeneration heater was used. The switching valve 1 used was one in which the diameter of the first orifice 10 and the diameter of the second orifice 11 were each set to 2.0 mm.

With this apparatus, regeneration of a trap having a trapped PM amount of 12 g was carried out under the following conditions.

Engine rotation speed = 1,000 rpm Load = 34 kgf · m Regeneration trap number = 1 (PM trap number = 3) Heater energization time = 15 minutes As a result of the above experiment, the leak port 9 was closed with a plug. In the device of the comparative example in which the exhaust gas was discharged only from the first orifice, the trap regeneration rate was 62%, whereas the first orifice (first flow path) and the second orifice (second flow path) In the apparatus of the present invention in which the exhaust gas was discharged from both of them, the trap regeneration rate was increased to 86%.

The regeneration rate referred to here is obtained by the formula of PM amount incinerated / PM amount collected before combustion.

In the apparatus of the comparative example, when the trap regeneration rate under the above conditions is increased by increasing the first orifice diameter, the amount of exhaust gas introduced into the regeneration trap when the engine speed increases is increased. However, since the apparatus of the present invention can close the second flow path 24 with the gate valve 25, the problem does not occur.

The opening and closing of the gate valve 25 is performed at an appropriate time. As the method, for example, (1) When the engine speed is a threshold (for example, 1000 rpm)
If it is less than or equal to the threshold value, the second flow path is opened.

(2) As shown in FIG. 6, hysteresis is provided for opening and closing, and when the engine speed drops to n ₁ or less, the second flow path is opened, and n ₂ (n ₁ <n ₂ ) is reduced. When it exceeds, the second flow path is closed.

(3) The load (torque) of the engine is detected. If the load is equal to or greater than the threshold, the second flow path is opened.
Close the channel.

In the method (2), since there is a width between n ₁ and n ₂ , the chattering of opening and closing which can be considered in the method (1) can be prevented, and the durability is improved. In the methods (1) and (2), the second flow path can be opened only at the time of idling. However, it is necessary to perform more advanced control by combining these methods and the method of (3). Is also possible.

[0040]

As described above, the exhaust gas purifying apparatus and the flow path switching valve according to the present invention switch the amount of exhaust gas introduced into the regeneration trap into two stages according to the operating condition of the engine to optimize the amount of oxygen supply. And an effect such as improvement of trap regeneration efficiency can be obtained.

Further, in the case where the opening and closing of the second flow passage of each switching valve is performed by one gate valve, the size and weight of the purifying device can be reduced, which is advantageous in terms of cost.

In addition, in the case where the second orifice is provided as a separate part, the part can be changed by responding to a request for changing the diameter of the second orifice. The nipple formed with the second orifice in the joint has an advantage that the cost required for changing the orifice diameter can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a switching valve used in the present invention.

FIG. 2 is an enlarged sectional view of a second orifice installation portion of the valve of the above.

FIG. 3 is a sectional view showing an example in which a second orifice is provided in a nipple.

FIG. 4 is a diagram showing an embodiment of the exhaust gas purification apparatus of the present invention.

FIG. 5 is a diagram showing an embodiment of an exhaust gas purification device in which a flow path switching valve is installed upstream of a trap.

FIG. 6 is a timing chart showing an example of opening and closing the second flow path;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow-path switching valve 2 Valve body 3 First valve body 3a Seal surface 4 Second valve body 4a Seal surface 5 Support arm 6 Introducing port 7 Valve chamber 8 Discharge port 9 Leak port 10 First orifice 11 Second orifice 12 Input shaft DESCRIPTION OF SYMBOLS 13 Support shaft 14, 15 Valve seat 16 Parts 17 Packing 18 Piping 19 Plug joint 20 Nipple 21 Main exhaust pipe 22a to 22n Branch path 23 Trap 24 Second flow path 25 Gate valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Yagi 3- 25-1, Tonomachi, Kawasaki-ku, Kawasaki City Inside Isuzu Motors Kawasaki Plant (72) Inventor Jiro Saito 3-25-1, Tonomachi, Kawasaki-ku, Kawasaki City Isuzu Motors Corporation Kawasaki Plant (72) Inventor Takao Fujisaki 8 Fujisawa City Tsuranabe Isuzu Motors Ltd. Fujisawa Plant (72) Inventor Noriyuki Suzuki 3- 25-1, Tonomachi, Kawasaki-ku, Kawasaki City Isuzu Motors Limited Inside the Kawasaki Plant (72) Inventor Ryo Kagiya 3-25-1, Tonomachi, Kawasaki-ku, Kawasaki City Isuzu Motors Corporation Kawasaki Plant

Claims (6)

[Claims] An exhaust purification device for burning particulates collected by a trap using oxygen in exhaust gas passing through the trap, wherein the first flow path and a second flow path are provided upstream or downstream of the trap. A flow path is provided, a flow path switching valve having an orifice is disposed at a branch of the first flow path and the second flow path, and a gate valve is disposed in the second flow path. An exhaust gas purification apparatus for a diesel engine, wherein a passage switching valve restricts passage of exhaust gas in a first passage and allows exhaust gas to flow in a second passage. 2. A flow path switching valve used in the exhaust gas purification apparatus according to claim 1, wherein the valve body includes an exhaust introduction port, an exhaust port, a leak port, and a valve chamber communicating the ports. A first valve body for opening and closing an exhaust port and a second valve body for opening and closing a leak port provided in a valve chamber;
An input shaft for applying a displacement force to the first and second valve bodies, a first orifice provided in the first valve body, and a second orifice for narrowing a second flow path from the leak port, and the rotation of the input shaft The exhaust port and the leak port are selectively opened and closed by the exhaust gas, and when the exhaust port is closed, the exhaust gas flows from the valve chamber to the exhaust port through the first flow path narrowed by the first orifice.
A flow path switching valve configured to flow from the valve chamber to the second flow path via the second orifice. 3. The flow path switching valve according to claim 2, wherein a part to be removably mounted is provided in the valve body or in the middle of the second flow path, and the second orifice is provided in the part. 4. A plug joint according to claim 2, wherein a plug joint for connecting the pipe for the second flow passage to the valve body and a nipple which is removably screwed into a hole of the plug joint are provided, and the nipple is provided with a second orifice. Flow path switching valve. 5. A trap for branching an exhaust path of an engine into a plurality of parts and collecting particulates in exhaust gas in each branch path, and a flow path switching valve according to claim 2, 3 or 4. It is provided so as to be on the downstream side of the branch path from the trap, and further, a second flow path connected to a leak port of each switching valve is merged into one, and the gate valve is arranged in the merged second flow path. The exhaust purification device for a diesel engine according to claim 1. 6. A trap for branching an exhaust path of an engine into a plurality of parts and collecting particulates in exhaust gas in each branch path and a flow path switching valve according to claim 2, 3 or 4. It is provided so as to be on the upstream side of the branch path from the trap, and further, the second flow path connected to the leak port of each flow path switching valve is merged with the original branch path on the upstream side of the trap to form a second flow path. 2. The exhaust gas purifying apparatus for a diesel engine according to claim 1, wherein said gate valve is disposed in each of said gate valves.