JP3250645B2 - Exhaust gas purification equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for purifying exhaust gas emitted from an engine, particularly a diesel engine.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, a catalytic converter containing an oxidation catalyst is provided in an exhaust pipe of an engine, and a bypass pipe is connected to the exhaust pipe so as to bypass the catalytic converter. And the first valve adjusts the respective flow rates to the bypass pipe, and the controller controls the first valve based on the detection output of the temperature sensor that detects the exhaust gas temperature on the exhaust gas upstream side of the catalytic converter. An exhaust gas treatment device is disclosed (Japanese Utility Model Laid-Open No. 4-75124). In this apparatus, shut off temperature within a predetermined activation temperature range in which the temperature sensor is obtained an exhaust gas purifying effect by the oxidation catalyst, that is, detects the higher exhaust gas temperature than the temperature T _1, the flow of exhaust gas into the bypass pipe exhaust To a catalytic converter, and the exhaust gas is purified by an oxidation catalyst contained in the converter. Also, when the temperature sensor is, for example, at the time of light load operation of the engine,
Temperature deviating from a predetermined activation temperature range obtained an exhaust gas purifying effect by the oxidation catalyst, that is, to detect the temperature T ₁ of the following exhaust gas temperature, so as to lead to the bypass pipe to block the flow of exhaust gas into the catalytic converter ing.

[0003] On the other hand, there is known a particulate removal device provided with a particulate collector in which a particulate filter is accommodated in an exhaust pipe in order to remove particulates in exhaust gas of an engine. In this device, when particulates accumulate on the filter and the filter is clogged, the filter is regenerated by burning the particulates collected by an electric heater, a burner or the like.

[0004]

[SUMMARY OF THE INVENTION However, the above-mentioned conventional exhaust gas treatment apparatus, when the exhaust gas temperature is low temperature T ₁ of less of the exhaust gas purifying effect by the oxidation catalyst is directly through the bypass pipe without purifying exhaust gas There was a problem that the exhaust gas was discharged to the atmosphere and the exhaust gas could not be sufficiently purified. Further, the above-mentioned conventional exhaust gas treatment device, the exhaust gas temperature becomes extremely high exceeding the temperature T _1, the sulfur content in the exhaust gas there is a problem that is oxidized sulfate is generated. Also,
The above-mentioned conventional particulate removal apparatus requires an electric heater and a burner for regenerating the filter when the particulate filter is clogged, and the structure of the particulate collection amount detection unit is complicated, which reduces manufacturing costs. There was a problem to raise. Further, in the above-mentioned conventional particulate removal apparatus, there is a problem that the reliability of the trapping amount detection unit is low.

An object of the present invention is to provide an exhaust gas purifying apparatus capable of oxidizing and removing particulates deposited on a particulate filter with a relatively simple structure without using an electric heater, a burner or the like. Another object of the present invention is to
When the exhaust gas temperature is extremely high, the exhaust gas can be guided to the bypass pipe to prevent the formation of sulfate by the oxidation catalyst,
An object of the present invention is to provide an exhaust gas purifying apparatus capable of oxidizing and removing particulates deposited on a particulate filter even during light load operation of an engine having a low exhaust gas temperature.

[0006]

A configuration of the present invention for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The present invention provides a catalytic converter 14 provided in an exhaust pipe 13 of an engine 11 and containing an oxidation catalyst 16, a bypass pipe 17 connected to the exhaust pipe 13 so as to bypass the catalytic converter 14, and a catalytic converter 14 for exhaust gas. A first valve 21 capable of adjusting the respective flow rates to the bypass pipe 17, a temperature sensor 26 for detecting an exhaust gas temperature on the exhaust gas upstream side from the catalytic converter 14, and a temperature sensor 26.
And a controller 28 for controlling the first valve 21 based on the detection output of the exhaust gas purifying apparatus. The characteristic configuration includes a particulate collector 23 provided in the exhaust pipe 13 on the exhaust gas downstream side of the catalytic converter 14 and the bypass pipe 17 and containing the particulate filter 24, and an exhaust gas downstream side from the particulate collector 23. And a second valve 22 provided in the exhaust pipe 13 for adjusting the flow rate of exhaust gas flowing through the exhaust pipe 13. The controller 28 operates the engine 11 in a light load operation based on the detection output of the temperature sensor 26. When it is determined that the state is the state, the first valve 21 is controlled and the bypass pipe 17 is closed to guide the exhaust gas to the catalytic converter 14 and the second valve 2
By controlling the first valve 21 and closing the bypass pipe 17 when it is determined that the engine 11 is in the medium load operation state based on the detection output of the temperature sensor 26 , the throttle valve 2 is closed. > The exhaust gas is guided to the catalytic converter 14 and the second valve 2
2, the first valve 21 is controlled to open the bypass pipe 17 when it is determined that the engine 11 is in the high load operation state based on the detection output of the temperature sensor 26.
More specifically, the exhaust gas is introduced into the particulate collector 23 via the bypass pipe 17 and the second valve 22 is fully opened.

[0007]

When the engine 11 is operating at a light load, the controller 28 detects a relatively low exhaust gas temperature.
Based on the detected output, the first valve 21 is controlled to close the bypass pipe 17 to guide the exhaust gas to the catalytic converter 14. At the same time, the second valve 22 is throttled to increase the exhaust resistance, thereby increasing the exhaust gas temperature. As a result, the engine 11
Even during a light load operation, the oxidation catalyst 16 is activated, so that nitrogen monoxide in the exhaust gas is converted into nitrogen dioxide by the oxidation catalyst, and the nitrogen dioxide is collected by the particulate filter 24. Is oxidized and removed.

When the engine 11 is operating at a medium load, the controller 28 opens the second valve 22 fully since the exhaust gas is within a predetermined temperature range. As a result, the oxidation catalyst 16
, Nitrogen oxides are generated, and the particulates deposited on the particulate filter 24 are oxidized and removed by the nitrogen dioxide. Further, at the time of high load operation of the engine 11, the controller 28 controls the first valve 21 based on the detection output of the temperature sensor 26 that has detected an extremely high exhaust gas temperature, and bypasses the exhaust gas to the catalytic converter 14, that is, connects the bypass pipe 17. Through the particulate collector 23 via This is to prevent the generation of mist-like sulfate generated by the oxidation catalyst 16 by introducing high-temperature exhaust gas into the catalytic converter 23.

[0009]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG.
One end of an exhaust pipe 13 is connected to one exhaust manifold 12, and a catalytic converter 14 is provided in the middle of the exhaust pipe 13. The catalytic converter 14 accommodates an oxidation catalyst 16. In this example, the oxidation catalyst 16 is formed by dispersing and supporting a noble metal such as platinum or palladium on a porous alumina ceramic carrier formed in a honeycomb shape or a pellet shape.

[0010] A bypass pipe 17 is connected to the exhaust pipe 13 so as to bypass the catalytic converter 14. That is, the bypass pipe 17 is arranged in parallel with the main pipe 13a of the exhaust pipe 13 which is located between the branch portion 18 to which the exhaust gas upstream end of the bypass pipe 17 is connected and the junction 19 to which the exhaust gas downstream end of the bypass pipe 17 is connected. Connected. A first valve 21 capable of adjusting the flow rate of the exhaust gas to the main pipe 13 a and the bypass pipe 17 is provided at the branch portion 18 of the exhaust pipe 13. The valve 21 has a first valve main body 21a for opening and closing the main pipe 13a and the bypass pipe 17, and a first driving unit 21b for driving the first valve main body 21a. The first valve body 21a has a neutral position indicated by a solid line at which exhaust gas can be simultaneously introduced into both the main pipe 13a and the bypass pipe 17 by the first driving means 21b, the main pipe 13a is opened, and the bypass pipe 1 is opened.
7 is closed by a dashed line, and the main pipe 13 is closed.
a is closed and the bypass pipe 17 is opened.

An exhaust pipe 13 downstream of the catalytic converter 14 and the bypass pipe 17 on the exhaust gas side, that is, an exhaust pipe 13 downstream of the junction 19 on the exhaust gas side, has a particulate collector 23.
And a particulate filter 24 is accommodated in the collector 23. In this example, the filter 24 is a honeycomb filter formed of a porous heat-resistant ceramic material. A plurality of exhaust gas passages 24c having a substantially rectangular cross section formed by the partition walls 24b;
An outlet-side plug 24d for plugging every other outlet of 4c,
Exhaust gas passage 2 not sealed by outlet-side plug 24d
And an inlet-side plug 24e that seals the inlet of 4c. Particulates in the exhaust gas are collected when passing through the partition wall 24b. A second valve 22 capable of adjusting the flow rate of the exhaust gas flowing through the exhaust pipe 13 is provided in the exhaust pipe 13 on the exhaust gas downstream side of the particulate collector 23. This valve 22 has a second valve body 22a.
And a second driving means 22b for driving the second valve body 22a. The second valve body 22a is connected to the exhaust pipe 13
Are rotatable to two positions: a fully open position indicated by a solid line that fully opens the switch, and a half open position indicated by a broken line that opens the exhaust pipe 13 halfway.

The exhaust pipe 13 upstream of the exhaust gas from the branch 18
Are provided with a temperature sensor 26 for detecting an exhaust gas temperature on the exhaust gas upstream side of the catalytic converter 14 and a pressure sensor 27 for detecting an exhaust gas pressure on the exhaust gas upstream side from the branch portion. Each detection output of the temperature sensor 26 and the pressure sensor 27 is connected to a control input of a controller 28, and the control output of the controller 28 is connected to the first and second driving units 21b and 22b.
Connected to. The controller 28 is provided with a memory 29, and the memory 29 has first and second valves 21, 21.
A predetermined temperature and a predetermined pressure as conditions for switching 2 are stored. The predetermined temperature is 550 ° C. and 300 in this example.
° C, and the predetermined pressure is 200 mmHg in this example. As shown in FIG. 2, when the exhaust gas temperature T is 300 ° C. or lower, the conversion rate of nitrogen monoxide to nitrogen dioxide is low. When the exhaust gas temperature T is 300 ° C. to 550 ° C., the conversion rate sharply increases, and the exhaust gas temperature T It is known that the above conversion becomes substantially constant when the temperature exceeds 550 ° C.

The operation of the exhaust gas purifying apparatus thus configured will be described with reference to FIGS. Immediately after the start of the engine 11 or during light load operation, the exhaust gas temperature is relatively low, and the temperature sensor 26 detects an exhaust gas temperature T of less than 550 ° C.
The controller 28 drives the first driving means 21b based on the detection output of the temperature sensor 26,
1a is rotated to the main pipe open position indicated by the dashed line in FIG. Also, immediately after the start of the engine 11 or during light load operation, a predetermined amount or more of particulates accumulates on the particulate filter 24, and the pressure sensor 27 detects the exhaust gas pressure P =
Upon detecting 200 mmHg or more, the controller 28 drives the second drive means 22b based on the detection output of the pressure sensor 27, brings the second valve body 22a to the half-open position shown by the broken line, and increases the exhaust resistance to reduce the exhaust gas temperature. To raise. When the temperature sensor 26 detects that the exhaust gas temperature T exceeds 300 ° C., the controller 28 moves the second valve main body 22a to the fully open position indicated by the solid line via the second driving means 22b. When the exhaust gas temperature exceeds 300 ° C., the oxidation catalyst 16 is activated as shown in FIG. 2 to convert harmful gases such as carbon monoxide and hydrocarbons to harmless substances such as carbon dioxide and water, To nitrogen dioxide. The converted nitrogen dioxide is collected in the particulate trap 2
3, and oxidizes and removes the particulates collected by the particulate filter 24. As a result,
The particulates accumulated on the filter 24 can be removed even immediately after the start of the engine 11 or during light-load operation.

When the engine 11 is operated under a medium load,
Since the exhaust gas temperature is in the range of 300 to 550 ° C,
As described above, the particulates accumulated on the particulate filter 24 are oxidized and removed by the nitrogen dioxide generated by the oxidation catalyst 16, and the filter 24 does not become clogged due to the accumulation of the particulates. The engine 11 is operated at a high load, and the temperature sensor 26 detects the exhaust gas temperature T = 55.
When 0 ° C. or higher is detected, the controller 28 drives the first drive means 21b to rotate the first valve body 21a to the bypass pipe open position shown by the broken line in FIG. It is introduced into the collector 23. This is to avoid that when high-temperature exhaust gas is introduced into the catalytic converter 16, the sulfur content of the exhaust gas stream is oxidized by the oxidation catalyst 16 to form mist-like sulfate. During the high load operation, the particulates accumulated on the filter 24 are oxidized and removed only by the heat of the exhaust gas.

In the above embodiment, the first valve is controlled in three stages of a neutral position, a main tube open position and a bypass tube open position, and the second valve is controlled in two stages of a fully open position and a half open position. The valve may be controlled in two or four or more stages of the main tube open position and the bypass tube open position, and the second valve may be controlled in three or more stages. In this case, finer optimization is possible. Further, in the above embodiment, the detection outputs of the temperature sensor and the pressure sensor were connected to the control input of the controller. However, if the particulates accumulated on the particulate filter could be completely oxidized and removed by nitrogen dioxide, the temperature could be reduced without using a pressure sensor. Only the sensors may be connected to the control input of the controller. In this case, the controller controls the first and second valves based on the detection output of the temperature sensor. Furthermore, the numerical values of the exhaust gas temperature and the exhaust gas pressure described in the above embodiment are merely examples, and are not limited to these numerical values.

[0016]

As described above, according to the present invention, the particulate collector is provided in the catalytic converter and the exhaust pipe downstream of the bypass pipe bypassing the converter, and the controller detects the exhaust gas temperature. A first valve that adjusts the amount of exhaust gas flowing into the catalytic converter and the bypass pipe based on the detection output of the temperature sensor, and a second valve that adjusts the exhaust gas flow rate from the particulate collector to the exhaust pipe downstream of the exhaust gas. Since the exhaust gas is configured to control two valves, the conventional exhaust gas is discharged to the atmosphere via a bypass pipe without purifying the exhaust gas when the temperature of the exhaust gas is lower than the low temperature at which the exhaust gas is purified by the oxidation catalyst. Compared with the gas treatment device, in the present invention, even when the engine having a low exhaust gas temperature is operated at a light load, the exhaust gas accumulates on the particulate filter. Particulates can remove oxidation.

Further, when the temperature of the exhaust gas is extremely high, the exhaust gas of the present invention is compared with a conventional exhaust gas treatment apparatus which oxidizes the sulfur content in the exhaust gas to produce sulfate, and when the temperature of the exhaust gas is extremely high, the exhaust gas is bypassed. , The formation of sulfate at the oxidation catalyst can be prevented. Furthermore, a conventional particulate removal device requires an electric heater or a burner to regenerate the filter when the particulate filter is clogged, and has a complicated structure of a particulate collection amount detection unit, which raises manufacturing costs. In comparison with the present invention, the particulate matter deposited on the particulate filter can be oxidized and removed with a simple structure that does not use an electric heater, a burner, or the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust gas purifying apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conversion rate of NO to NO ₂ with respect to a change in exhaust gas temperature.

FIG. 3 is a flowchart showing the operation of the device.

[Explanation of symbols]

 11 Diesel engine 13 Exhaust pipe 14 Catalytic converter 16 Oxidation catalyst 17 Bypass pipe 21 First valve 22 Second valve 23 Particulate collector 24 Particulate filter 26 Temperature sensor 28 Controller

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F01N 3/24 ZAB F01N 3/24 ZABE F02D 9/04 F02D 9/04 E (56) References JP-A-5-44436 (JP) JP-A-6-264719 (JP, A) JP-A-5-65817 (JP, A) JP-A-3-8612 (JP, U) JP-A-4-75124 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) F01N 3/02 F01N 3/20 F01N 3/24 F02D 9/04

Claims (1)

(57) [Claims] A catalyst converter (14) provided in an exhaust pipe (13) of an engine (11) and accommodating an oxidation catalyst (16), and the exhaust pipe (13) is arranged to bypass the catalytic converter (14). ), A first valve (21) capable of adjusting respective flow rates of exhaust gas to the catalytic converter (14) and the bypass pipe (17), and the catalytic converter (14). Temperature sensor for detecting exhaust gas temperature on the upstream side of exhaust gas (26)
Based on the detection output of the temperature sensor (26).
An exhaust gas purifying apparatus comprising a controller (28) for controlling a valve (21), a particulate filter provided in the exhaust pipe (13) on the exhaust gas downstream side of the catalytic converter (14) and the bypass pipe (17). (24) contained particulate collector (2
3), a second valve (22) provided in the exhaust pipe (13) on the exhaust gas downstream side of the particulate collector (23) and capable of adjusting the flow rate of exhaust gas flowing through the exhaust pipe (13). The controller (28) controls the engine based on a detection output of the temperature sensor (26).
When it is determined that ( 11 ) is in the light load operation state, the first
Controlling the valve (21) and closing the bypass pipe (17);
The exhaust gas is guided to the catalytic converter (14), and the second valve (22) is throttled. Based on the detection output of the temperature sensor (26), the engine
When it is determined that ( 11 ) is in the medium load operation state, the first
Controlling the valve (21) and closing the bypass pipe (17);
The exhaust gas is guided to the catalytic converter (14) and the second valve (22) is fully opened, and the engine is operated based on the detection output of the temperature sensor (26).
When it is determined that ( 11 ) is in a high load operation state, the first
Opening the bypass pipe (17) by controlling the valve (21);
To introduce the exhaust gas into the particulate collector (23) through the bypass pipe (17), and the second valve (2
An exhaust gas purifying apparatus characterized in that 2) is fully opened.