JPH06137130A - Exhaust gas after-treatment device for diesel engine - Google Patents

Abstract

PURPOSE:To raise the temperature of exhaust gas supplied to a collecting member without remarkably changing combustion condition of an engine so as to surely perform regeneration of the collecting member, in an exhaust gas after-treatment device provided into the exhaust system of a diesel engine. CONSTITUTION:This exhaust gas after-treatment device is provided with detecting means 11b, 11c to detect regeneration timing of collecting members 5a, 5b inserted between in the exhaust system 4 of a diesel engine, a regeneration means to receive the detected signals from the detecting means and supply hot temperature gas containing oxygen to the collecting members 5a, 5b, and the regeneration means is provided with an intake air throttling mechanism and a fuel injection advancing mechanism, so as to raise the temperature of exhaust gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas aftertreatment device attached to an exhaust system of a diesel engine.
The present invention relates to an exhaust gas aftertreatment device for a diesel engine, which is suitable for a large vehicle (for example, a truck).

[0002]

2. Description of the Related Art Conventionally, in an exhaust system of a heavy-duty diesel engine, a collection member (filter) for collecting particulates which are combustible and fine carbonized compounds discharged from a combustion chamber of a diesel engine. Is provided,
This allows the diesel particulates to be collected without being discharged from the exhaust port. Then, the diesel particulates accumulated on the collecting member are subjected to high temperature (for example, 400 ° C. or higher) exhaust gas discharged during high load operation of the vehicle and the like, and spontaneously combust (hereinafter referred to as “self-combustion”). Therefore, in the case where self-combustion does not occur, a regeneration device such as a regeneration device for raising the exhaust gas temperature is additionally provided in order to perform combustion of diesel particulates (hereinafter referred to as “regeneration”).

[0003]

However, in the conventional exhaust gas aftertreatment device for a diesel engine, when the engine is continuously operated in a medium-low load state where the load is not high, the amount of diesel particulates deposited on the collecting member is reduced. There is a problem that it increases and causes clogging. In order to prevent this clogging, drive the playback device,
Even if the engine is in a low load state, it is regenerated,
No suitable regenerating means has been proposed, and one that raises the exhaust gas temperature during the regenerating period without significantly changing the combustion state of the engine from the normal combustion state is demanded.

When the intake throttle mechanism is used as the regenerating means, as shown in FIG. 7, the maximum output torque curve is moved from a to b by greatly reducing the intake air, and If the fuel injection timing is retarded in the state, the combustion speed in a state with less air decreases, so combustion does not occur due to the decrease in pressure, HC in the exhaust increases, and the combustion state deteriorates significantly. There is a problem of doing. The present invention is intended to solve such a problem, and it is possible to raise the temperature of the exhaust gas supplied to the trapping member without significantly changing the combustion state of the engine. An object is to provide a processing device.

[0005]

Therefore, the exhaust gas aftertreatment device for a diesel engine according to the present invention is for trapping particulate matter which is inserted into the exhaust system of a diesel engine and is discharged from the combustion chamber. A collecting member, and a regeneration time detecting means for detecting a time when the collecting member should be regenerated; and a high temperature gas containing oxygen supplied to the collecting member in response to a regeneration time detection signal from the reproducing time detecting means. And a refueling means capable of regenerating the engine, the regenerating means restricting the intake air supplied to the engine according to the operating state of the engine to raise the temperature of the exhaust gas, and a standard fuel injection timing of the engine. It is characterized by being configured with a fuel injection advance mechanism for advancing from the fuel injection timing.

[0006]

In the above exhaust gas aftertreatment device for a diesel engine of the present invention, the regenerating means receives the regeneration timing detection signal from the regeneration timing detecting means and supplies the high temperature gas containing oxygen to the trapping member. The throttle mechanism is operated to throttle the intake air, thereby raising the temperature of the exhaust gas supplied to the collecting member, and operating the fuel injection advance mechanism to advance the engine from the optimum standard fuel injection timing. , This allows
The temperature of the exhaust gas supplied to the collecting member is further increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 8 show an exhaust gas aftertreatment device for a diesel engine as one embodiment of the present invention. As shown in FIG. 2, an air cleaner 3 and an intake valve 15 are provided in order from the upstream side in an air supply passage 2a in an air supply system 2 of a truck diesel engine 1 as a large vehicle.

Also, the exhaust system 4 of the diesel engine 1
Is a common exhaust passage 4a for feeding exhaust gas from the combustion chamber 1a formed at the top of the piston 13 and the first and first connecting portions 6 connected to the connecting portion 6 at the downstream end of the common exhaust passage 4a. It has two branch exhaust passages 4b and 4c and a common exhaust passage 4d connected to the connecting portion 6 at the downstream end of the first and second branch exhaust passages 4b and 4c.

An exhaust valve 16 is provided in the common exhaust passage 4a, and a temperature sensor 11f for detecting the exhaust temperature T _EX is provided in the common exhaust passage 4a. An on-off valve 8 that can close the two branch passages 4c is provided. The on-off valve 8 is always biased to the neutral position 8A, and receives the driving force of an actuator 9 described later, so as to receive a high temperature control position (second branch exhaust passage closed position).
8B [or a low temperature control position (first branch exhaust passage closed position) 8C].

A catalyst for high temperature is provided in the first branch exhaust passage 4b.
A ceramic diesel particulate trap 5a as a trapping member (for example, perovskite) is inserted, and the pressure sensor 11b is used to detect the upstream pressure P _I1 and the downstream pressure P ₀₁ of the diesel particulate trap 5a. To the pressure detection passages 19a and 19b. A ceramic diesel particulate trap 5b as a trapping member with a low temperature catalyst (for example, platinum) is inserted in the second branch exhaust passage 4c, and the upstream pressure P _{I2 of the} diesel particulate trap 5b is inserted. And a pressure sensor 11 to detect the downstream pressure P _02.
The pressure detection passages 19c and 19d are connected from c.

A muffler 7 is inserted in the common exhaust passage 4d. Further, the engine 1 is provided with a fuel injection pump 12 for pumping the fuel by receiving the rotational driving force from the crankshaft 20, and receiving the pressurized fuel from the fuel injection pump 12, the combustion chamber 1a. A fuel injection device (injector) 14 for injecting the fuel is provided. Furthermore, FIG.
As shown in, a control means (ECU) for receiving a detection signal from the sensor group 11 and outputting a control signal to the reproducing means 17 etc.
10 is provided, and this control means 10 is connected to a memory (ROM) 18 having a map according to the engine operating state.

The sensor group 11 is, as shown in FIGS.
Which operating area Z _{A of the} diesel engine 1 is the operating area Z _A
In order to determine whether ~Z is _E, and an output torque detecting means (load sensor) 11e for detecting an output torque T of the engine speed sensor 11d and diesel engine 1 to detect an engine rotational speed N of the diesel engine 1 The differential pressure ΔP [(= P _I1 −P ₀₁ ) between the operating region sensor 11a and the upstream detection pressures P _I1 , P _I2 and the downstream detection pressures P ₀₁ , P ₀₂ of the catalyst-attached diesel particulate traps 5a, 5b or (= P _I2 −P ₀₂ )], the pressure sensors 11b and 11c constituting the regeneration timing detection means, the above-described engine speed sensor 11d, and the ratio of the fuel injection amount or the air amount to the engine speed. The output torque detecting means 11e for obtaining the output torque based on the above, and the combustion chamber 1a inserted in the common exhaust passage 4a.
Exhaust temperature sensor 11f for detecting the temperature of exhaust gas from the rack and rack position sensor 11 for detecting the rack position of the fuel injection pump 12
It is configured with g and.

The control means 10 controls the normal fuel injection amount and the fuel injection timing (at this time, the fuel injection timing is the standard fuel injection timing).
(See reference numeral C _{1 in} FIG. 7)], and is configured to include first to sixth control units 10a to 10f. The first control unit 10a includes a temperature sensor 11f. Is for outputting a control signal to the actuator 9 to move the on-off valve 8 to the high temperature position 8B when the exhaust temperature T _EX of the exhaust gas becomes equal to or higher than the predetermined temperature T _0. High temperature exhaust gas is not sent to the trap 5b. The second control section 10b is configured as a regeneration timing starting means, and detects the detection signals from the pressure sensors 11b and 11c and the particulates (Pc) in the diesel particulate traps 5a and 5b from the memory 18.
t) Comparing with the filter pressure loss signal [see FIG. 5] at the time of limit accumulation, if ΔP> Pl, the regeneration means 17 is operated.

The third control section 10c is configured as a regeneration timing ending means, and detects the detection signals from the pressure sensors 11b and 11c during regeneration and the filters in the diesel particulate traps 5a and 5b from the memory 18 during regeneration. Compared with the initial pressure drop signal [see FIG. 4], if ΔP ≦ P ₀ ,
All the reproducing means 17 are stopped. In addition, the fourth control unit 10d
The engine 1 based on the detection signal from the operating area sensor 11a
When the operation area Z is determined to be a first reproduction (intake throttle control) region Z _B, in which actuating the intake throttle mechanism 11a. Further, the fifth control unit 10e causes the operating region Z of the engine 1 to perform the second regeneration [simultaneous control of the intake throttle and the timing retard (or timing advance)] region Z _C based on the detection signal from the operating region sensor 11a. The intake throttle mechanism 11a and the fuel injection timing retarding mechanism 17c
(Or the fuel injection timing advance mechanism 17d) is operated at the same time.

Next, the sixth control unit 10f causes the operating region Z of the engine 1 to perform the third regeneration [intake throttle and timing retard (or timing advance) and exhaust throttle] based on the detection signal from the operating region sensor 11a. when an area Z _D, is intended for actuating the intake throttle mechanism 11a and the fuel injection timing retard mechanism 17c (or fuel injection timing advance mechanism 17d) and the exhaust throttle mechanism 17b and at the same time. The reproducing means 17 is shown in FIG.
As shown in FIG. 3, the intake valve 15 is throttled to restrict the cool air sent into the combustion chamber 1a to raise the exhaust temperature, and the exhaust valve 16 is throttled to increase the engine load and fuel injection. An exhaust throttle mechanism 17b for increasing the amount and a fuel injection timing retarding mechanism for retarding the fuel injection timing injected from the fuel injection device 14 into the combustion chamber 1a.
(Timing retard mechanism, symbol C _{2 in} FIGS. 6 and 8)
A reference) 17c, the fuel injection timing advance mechanism for advancing the fuel injection timing (timing advance mechanism, and is configured to include a code C ₃ reference) 17d in FIG.

The fuel injection timing retarding mechanism 17c and the fuel injection timing advancing mechanism 17d are provided in the fuel injection timing control device 17e.
Are configured. Further, the actuator 9 for driving the on-off valve
Is the first and second opening / closing valves 8 arranged in the connecting portion 6.
From the neutral position 8A where both the branch exhaust passages 4b, 4c communicate with the common exhaust passage 4a to the high temperature position (second branch exhaust passage closed position) 8B where only the first branch exhaust passage 4b communicates with the common exhaust passage 4a. A low temperature position (first position) for driving or for communicating only the second branch exhaust passage 4c with the common exhaust passage 4a
8C of the branch exhaust passage of the actuator, and the actuator 9 is a fluid pressure actuator or electromagnetic solenoid driven by receiving compressed air or pressure oil from a compressed air supply source through an electromagnetic valve. A driven electromagnetic actuator is used.

The actuators of the intake valve 15 and the exhaust valve 16 are not shown. Since the exhaust gas aftertreatment device for a diesel engine as the embodiment of the present invention is configured as described above, as shown in FIG. 3, the control means 10 controls the fuel injection amount and the fuel injection timing. Then, while inputting the detection signals from the respective sensors 11a to 11g (step b1), the first controller 10a
In steps b2 and b3, the opening / closing valve 8 is opened / closed, and high-temperature exhaust gas is not supplied to the diesel particulate trap 5b with a catalyst for low temperature. Therefore, SO ₃ is not generated, so that H ₂ SO ₄ is generated. It can also be prevented from occurring. When the second controller 10b detects the start of the regeneration time (step b4), the third controller 10c
Until the end of the regeneration time is detected by (step b
5) The regeneration promotion state is maintained.

In the regeneration promoting state, the third control unit 10
By c, the intake throttle is performed (step b6). As a result, if the operating region is within the first regeneration region Z _B , regeneration is started (step b7), and the first throttle with only this intake throttle is performed.
Next playback is performed. Even if this intake throttle is performed, if the exhaust temperature T _EX does not rise and regeneration does not occur, the intake air throttle and the timing retard (or timing advance) are controlled by the fourth control unit 10d in step b8 through step b8. Is performed (step b8), and if the operating region is within the second regeneration region Zc, the regeneration is started (step b9), and the secondary operation is performed by the intake throttle and the timing retard (or timing advance). Playback is performed.

Even if the intake throttle and timing retard are performed, if the exhaust temperature T _EX does not rise and regeneration does not occur, in step b11 through step b10, the fifth controller 10e controls the intake throttle and timing. Retardation (or timing advance) and exhaust throttling are performed (step b11), and the fuel injection amount is also increased (step b12), so that the operating region is within the third regeneration region Z _D. For example, the regeneration is started, and the third regeneration is performed by the intake throttle, the timing retard and the exhaust throttle. Also, after each regeneration step, it is confirmed whether or not the filter pressure loss ΔP has returned to the initial pressure loss P ₀ , and if the regeneration is completed, all regeneration devices are released.
(Steps b5 and b13). If the pressure loss ΔP corresponding to the accumulation amount of diesel particulates is greater than or equal to the pressure loss Pl corresponding to the limit accumulation amount, the current operating condition is maintained (step b12).

Further, a step for detecting that the operating region Z is the self-combustion region Z _A may be inserted between step b5 and step b6, and the temperature on the downstream side of each diesel particulate trap 5a, 5b may be adjusted. It may be configured to detect and detect that the reproduction is being performed. Also, timing advance may be used instead of the timing retard in step b8. That is, when the intake throttle is performed, the maximum torque curve for the same intake throttle amount decreases as shown in FIG. In such a state where the intake throttle is performed, the amount of air is small, and the combustion speed is reduced. However, if the timing retard is performed in such a state, the pressure is reduced and combustion does not occur, or the HC
Is increased, and an operating range Z _E occurs in which combustion is extremely deteriorated.

Therefore, in this operating region Z _E , as shown in FIG. 8, with respect to the optimum standard fuel injection timing characteristic C ₁ ,
Without using the retarded fuel injection timing retarding characteristic C ₂ ,
The advanced fuel injection timing advance characteristic C ₃ is used. As a result, it is possible to improve the combustion state of the engine within the operating region Z _E , and it is possible to achieve a reliable increase in exhaust gas temperature. Furthermore, the timing advance and the timing retard may be used in an appropriate combination.

According to this embodiment, the following effects and advantages can be obtained. (1) Even when a regeneration catalyst is used for the diesel particulate traps 5a, 5b, the diesel particulate traps 5a, 5b can be switched and used according to the exhaust temperature, and adapted to a wide operating range of the engine. be able to. (2) Since the supply of high-temperature exhaust gas to the diesel particulate trap 5b with a low temperature catalyst can be prohibited, the generation of diesel particulates can be reduced. (3) As shown in FIG. 6, the exhaust gas temperature T indicated by the symbols L _{1 to} L ₃
Exhaust temperature can be made higher than the regeneration limit temperature at the upper right of the isothermal boundary line where _EX is the regeneration limit temperature Tl. This allows regeneration to be appropriately performed and is appropriate according to the engine operating state. It can be controlled to switch to. (4) Due to the timing advance, the exhaust temperature can be raised by adjusting the fuel injection timing even when the output is reduced due to the intake throttle, so that the regeneration can be reliably performed. (5) Even in the middle and low load range of the engine where the exhaust temperature is low and the diesel particulates in the collection member are difficult to burn,
Combustion of diesel particulates in the collection member can be promoted, and thereby, regeneration can be reliably performed during operation of the regeneration device.

In the above embodiment, it is possible to provide only one of the first and second branch exhaust passages 4b and 4c without providing them. In this case, the connecting portions 6 and 6'are abolished, and the opening / closing valve 8 and its actuator 9 arranged in the connecting portion 6 are omitted. Further, the first controller 10a is also omitted.

[0024]

As described in detail above, according to the exhaust gas aftertreatment device for a diesel engine of the present invention, the H
While suppressing the increase of C, there is an advantage that the temperature of the exhaust gas supplied to the collecting member can be increased without significantly changing the combustion state of the engine from the normal combustion state. The member can be surely regenerated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control system of an exhaust gas aftertreatment device for a diesel engine as one embodiment of the present invention.

FIG. 2 is a schematic diagram showing the overall configuration of the device.

FIG. 3 is a flowchart for explaining a control procedure of the above device.

FIG. 4 is a graph showing the relationship between engine rotation speed and torque during operation of the above-described device.

FIG. 5 is a graph showing the relationship between engine rotation speed and torque during operation of the above device.

FIG. 6 is a graph showing the relationship between engine rotation speed and torque during operation of the above device.

FIG. 7 is a graph showing the relationship between engine rotation speed and torque during operation of the above device.

FIG. 8 is a graph showing a relationship between an engine speed and a fuel injection advance amount when the above device is in operation.

[Explanation of symbols]

1 Diesel engine 1a Combustion chamber 2 Air supply system 2a Air supply passage 3 Air cleaner 4 Exhaust system 4a, 4d Common exhaust passage 4b First branch exhaust passage 4c Second branch exhaust passage 5a Diesel as a trapping member for high temperature catalyst Particulate trap 5b Diesel particulate trap as a trapping member with low temperature catalyst 6,6 'Connection part 7 Muffler 8 Open / close valve 9 Actuator 10 Control means (ECU) 10a to 10f First to sixth control part 11 Sensor group 11a Operating area sensor 11b, 11c Pressure sensor constituting regeneration timing detection means 11d Engine speed sensor 11e Output torque detection means (load sensor) 11f Exhaust temperature sensor 11g Rack position sensor 12 Fuel injection pump 13 Piston 14 Fuel injection device (injector) ) 15 Intake valve 16 Exhaust valve 17 Regeneration means 17a Intake throttle mechanism 17b Exhaust throttle mechanism 17c Fuel injection timing retard Organization (timing retard mechanism) 17d the fuel injection timing advance mechanism (timing advance mechanism) 17e fuel injection timing control device 18 memory 19a~19d pressure detection passage 20 crankshaft

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F02D 41/40 D 8011-3G

Claims (1)

[Claims] 1. A regeneration timing, which includes a trapping member for trapping particulates discharged from a combustion chamber by being inserted in an exhaust system of a diesel engine, and which detects a timing at which the trapping member should be regenerated. A detection means and a regeneration means capable of supplying a high temperature gas containing oxygen to the collection member in response to a regeneration time detection signal from the regeneration time detection means,
The regeneration means throttles the intake air supplied to the engine according to the operating state of the engine, and an intake throttle mechanism that raises the temperature of the exhaust gas, and a fuel that advances the fuel injection timing of the engine from the standard fuel injection timing. An exhaust gas post-treatment device for a diesel engine, which is configured with an injection advance mechanism.