JPH03286120A - Exhaust fine particle purge device for diesel engine - Google Patents

Abstract

PURPOSE:To perform reuse of a filter without reducing a regeneration efficiency under an operation condition in a wide range by providing a flow control valve at the upstream side of an exhaust system branched into two passages each provided with a filter, an exhaust throttle valve, and a combustion support means. CONSTITUTION:An exhaust system 2 of an engine 1 is composed of branched passages 6, 7 branched into two via an upstream passage 4 connected to an exhaust gas mainhold 3 and a branched part 5 and a downstream passage 8. At the branched part 5, a branch valve 12 is provided. At the time of reusing a filter 9a of one of branched passages 6, a passage area at the downstream of the filter 9a is throttled by an exhaust throttle valve 10, and much exhaust gas is supplied to the branch passages 6 by the operation of the branch valve 12. Since exhaust gas temperature and oxygen concentration are increased, a proper regeneration effect is secured. Since exhaust gas is partially discharged through the branch passage 7, a working condition of the regeneration of filters 9a, 9b is remarkably moderated and decrease in the temperature of the filter 9b is prevented.

Description

[Detailed Description of the Invention] This invention provides an exhaust particulate purification device for a diesel engine,
In particular, the present invention relates to a device that collects and burns off combustible particulates contained in exhaust gas.

(Prior art) The exhaust gas of diesel engines contains combustible particulates (particulates) such as carbon in winter.
The exhaust system of this type of diesel engine is equipped with the above-mentioned particulate filter, which collects the above-mentioned particulates and prevents them from being discharged to the outside.

By the way, in the above particulate filter,
There is a problem in that the collected particulates accumulate and cause clogging, creating exhaust resistance and deteriorating the output performance of the engine.

For such problems, for example, Japanese Patent Application Laid-Open No. 57-658
As shown in Publication No. 11, an exhaust throttle valve that adjusts the passage area is provided downstream of a particulate filter installed in the exhaust passage, and the exhaust throttle valve is operated when clogging of the filter is detected. There is a filter that regenerates the filter by increasing the back pressure by closing the filter, thereby raising the temperature of the exhaust gas, and using that heat to burn the combustible particulates deposited on the filter. According to this,
There is an advantage that combustible particulates deposited on the filter are quickly burned and removed.

Furthermore, for example, in Japanese Patent Application Laid-open No. 55-19934, an engine exhaust system is branched into two routes, a particulate filter is installed in each branch route, and a particulate filter is installed in each branch route at the branch point to the re-branch route. A switching valve is installed to switch the inflow of exhaust gas, and when one filter is regenerated, the switching valve is operated to allow the exhaust gas to flow into the other branch path and be discharged, while also being generated by a combustion means such as a burner. Some devices use heat to burn combustible particles that have accumulated on the filter on the regeneration side.

According to this, the exhaust gas discharged from the engine is discharged through the branch path on the non-regeneration side, so that the particulate filter can be regenerated regardless of the operating state of the engine.

(Problem to be Solved by the Invention) However, in the former regeneration method, the exhaust passage is constricted, resulting in large exhaust resistance, making it impossible to operate under particularly high load conditions, and limiting operating conditions. There is.

On the other hand, according to the latter regeneration method, when regenerating the filter in one branch route, the exhaust gas exhausted from the engine is exhausted through the other branch route, which causes the above-mentioned inconvenience. However, since the filter is regenerated only with heat from a combustion means such as a burner, there is another problem that the regeneration efficiency is low.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to realize an exhaust particulate purification device in a diesel engine equipped with a particulate filter in the exhaust system, which is capable of regenerating the filter over a wide range of engine operating conditions without impairing the regeneration efficiency. With the goal.

(Means for Solving the Problems) That is, the diesel engine exhaust particulate purification device according to the present invention has a configuration in which the exhaust system is provided with a particulate filter that collects combustible particulates, and the exhaust system has two paths. The filter is branched, and each branch path is provided with the filter, an exhaust throttle valve that changes the passage area on the downstream side of the filter, and combustion assisting means for the particulate matter collected by the filter, and A flow control valve is provided at the upstream portion of each branch path to supply exhaust gas to the branch path to which one filter belongs when regenerating the filter, and to also allow a portion of the exhaust gas to flow into the other branch path. shall be.

(Function) According to the above configuration, when the filter in one branch path is regenerated, the passage area on the downstream side of the filter is throttled by the exhaust throttle valve, and a large amount of exhaust gas is released by the operation of the flow rate control valve. Since the gas is supplied to the branch route, the adiabatic compression effect causes the exhaust gas temperature to rise and the oxygen concentration to rise as well, resulting in good regeneration efficiency.

Furthermore, the heat generated by the combustion auxiliary means further increases the exhaust gas temperature, so that the regeneration efficiency is further improved.

Moreover, since a portion of the exhaust gas is discharged through the other branch path, deterioration of the engine operating condition is avoided and the operating conditions for filter regeneration are significantly eased, and the temperature of the filter on the non-regeneration side is As a result, when the filter is regenerated, the regeneration is completed quickly.

(Example) Examples of the present invention will be described below.

As shown in FIG. 1, the exhaust system 2 of the engine 1 includes an upstream path 4 that is continuous with the exhaust manifold 3, and a first path that branches into two parts via a branch 5 on the downstream side of this upstream path 4. It is constituted by a second branch route 6.7 and a downstream route 8 where the downstream sides of each branch route 6, 7 are gathered.

The first and second branch paths 6 and 7 include first and second particulate filters (hereinafter referred to as filters) 9a and 9b having the same configuration, and a downstream passage area of each filter 9a and 9b. First and second exhaust throttle valves 10.
11, and each branch route 6.7 is provided at the branch part 5 from the upstream route 4 to both branch routes 6.7.
A branch valve 12 is provided to adjust the amount of exhaust gas flowing into the exhaust gas.

Here, to explain the structure of both the filters 9a and 9b, for example, the first filter 9a has partition walls 14...14 provided inside the casing 13, as shown in FIG.
Four divided sections 15...15 are provided, and each divided section 15...15 has a filter element 17...17 supported by an inkram mat 16...16. Decorated. As is well known, each filter element 17 alternately opens and closes both ends of a large number of holes formed in a honeycomb shape using a porous material, so that the exhaust gas flowing into the hole having an open upstream end passes through the partition wall of the adjacent hole. The exhaust gas is made to flow into a hole with an open downstream end, so that when the exhaust gas passes through the partition wall, fine particles in the gas are collected.

In addition, downstream of the filter elements 17...17 in each of the divided portions 15...15, there are outlet temperature sensors 18 and 18 for detecting the temperature of the exhaust gas after passing through the elements 17...17. ...18 are installed respectively, and also the above-mentioned element 17...
Exhaust heaters 19 . . . 19 are installed on the upstream side of the heaters 17 to raise the temperature of the exhaust gas. and,
An inlet temperature sensor 20 for detecting the temperature of the exhaust gas flowing through the branch section 5 is installed on the upstream side of each of the divided sections 15...15 in the filter 9a. A pressure sensor 21 is installed to detect the pressure of exhaust gas. Note that the second branch route 7 also has a similar configuration, so a description thereof will be omitted.

Further, in this engine 1, negative pressure is applied to first and second actuators 22.23 that operate the first and second exhaust throttle valves 10.11, respectively, and a third actuator 24 that operates the branch valve 12. Vacuum pump 2 that supplies
5, and negative pressure passages 26a, 2 leading from the vacuum pump 25 to the first and second actuators 22.23.
6b includes first and second passages that connect and disconnect the passages 26a and 26b.
Solenoid valves 27 and 28 are provided respectively, and the negative pressure passage 26c leading to the third actuator 24 is also provided with a duty solenoid valve 29 that opens and closes the passage 26c in a continuously variable manner. .

This engine 1 includes opening/closing control of the first and second exhaust throttle valves 10 and 11, and a branch valve 1 of the branch section 5.
2 direction control and exhaust heaters 19...19 of each divided portion 15...15 in the first and second filters 9a, 9b.
A control unit 30 is provided to perform energization control. This control unit 30 receives a water temperature signal from a water temperature sensor 31 provided in the engine 1 and the first
, the inlet temperature signals from the respective inlet temperature sensors 20, 20 in the second branch paths 6 and 7, and the respective dividing portions 15...
・Input the outlet temperature signals from the outlet temperature sensors 18...18 in 15 and the pressure signals from each pressure sensor 21, 21 in the first and second branch paths 6.7, and based on these signals The first and second solenoid valves 27
．． 28, an opening/closing control signal for operating the first and second actuators 22.23 for driving the first and second exhaust throttle valves 1.0.11, and the duty solenoid valve 29. , outputs a duty control signal for operating the third actuator 24 for driving the branch valve 12, and an energization control signal for each of the exhaust heaters 19, . . . , 19, respectively.

Next, the operation of this embodiment will be explained according to the flowchart of filter regeneration control shown in FIG.

Specifically, the control unit 30 first maintains the branch valve 12 in the neutral state as shown in FIG. 1 by adjusting the interval of the duty control signal output to the duty solenoid valve 29 in step S1. . As a result, the exhaust gas discharged from the engine 1 flows into the first and second branch paths 67 via the upstream meridian 4 and the branch part 5 in approximately equal amounts, and the The first and second filters 9a9b are warmed up.

Next, in step S2, the control unit 30 determines whether or not the engine water temperature tw has risen above a predetermined warm-up completion water temperature twO. Part 15...15
Calculate the temperature difference ΔTIJ for each time. Here, eight pieces of data corresponding to the respective division parts 15...15 are calculated as ΔTl.

Then, the control unit 30 performs the following step S.
4, 8 data of the above temperature difference △TIJ〈△T 11+
ΔT 12+..., ΔT24>, the largest one is selected as the representative temperature difference ΔT, and in step S5 it is determined whether the representative temperature difference ΔT exceeds a predetermined value To. do. That is, for example, the temperature difference △T, □
When is the largest, this value is set as ΔT, and the temperature difference Δc is compared with a predetermined value T.

The representative temperature difference △T is below the specified value. If it is not above, it is presumed that no transient clogging has occurred in each of the filter elements 17...17 in the first and second filters 9a, 9b, so the control unit 30 controls the representative temperature difference 6. Step S until it is determined that the value To has reached the predetermined value To.

While executing the loop processing of ~S5, the above predetermined value △T
When the time point o is reached, the loop process is exited, the exhaust heater 19 of the divided section 15 is energized, and the first exhaust throttle valve 10 of the first branch path 6 to which the divided section 15 belongs is turned on.
After closing (the state indicated by the chain line in FIG. 1), a built-in timer (not shown) set in advance to a predetermined time is started (steps 86 to Ss). As a result, the dividing section 1
Regeneration of the filter element 17 at step 5 is started.

Next, the control unit 30 determines that the upstream pressure P of the first branch path 6 detected by the pressure sensor 21 in step S9 is a predetermined pressure P. The pressure P is determined by determining whether it is smaller than the pressure P. If it is smaller, step SIO is executed to move the branch valve 12 from the neutral position indicated by the chain line to the non-regeneration side as indicated by the solid line in FIG.

At this time, the opening to the non-regeneration side, that is, the second branch path 7, is not completely blocked but is left partially open. Therefore, most of the exhaust gas discharged from the engine 1 flows into the first branch path 6, and a portion thereof also flows into the second branch path 7. As a result, a large amount of exhaust gas is supplied to the first branch path 6, so that the exhaust gas temperature further increases due to the adiabatic compression effect, and the oxygen concentration also increases, resulting in good regeneration efficiency. Furthermore, since a portion of the exhaust gas is discharged through the second branch path 7, the temperature of the second filter 9b belonging to the branch path 7 is prevented from decreasing.

Then, in step S1□, the control unit 30 determines whether or not the timer has timed up. If it is determined that the timer has timed up, the control unit 30 proceeds to step S13 to open the first exhaust throttle valve 10, and to exhaust the air and to The energization is stopped and the process returns to step S3. Then, the filter elements 17...17 of the respective division parts 15...15 in the first and second filters 9a9b are sequentially regenerated.

Here, for example, the first filter 9 in the first branch path 6
When performing the regeneration of a, the upstream pressure P is the predetermined pressure P in step S9.

When it exceeds, the control unit 3o moves to step Sll and moves the branch valve 12 to the first branch path 6 side as shown in FIG. As a result, most of the exhaust gas is discharged through the second branch path 7 with less exhaust resistance, and the operating condition of the engine 1 is maintained in a good condition.

In addition, in this embodiment, the first and second branch routes 6.7
The temperature sensors provided at the upstream portions of the first and second filters 9a and 9b are common, but the divided portions 15...1
A temperature sensor may be provided for every 5.

(Effects of the Invention) As described above, according to the present invention, when regenerating the filter in one branch path, the passage area on the downstream side of the filter is throttled by the exhaust throttle valve, and the flow rate control valve operates to reduce the flow rate. Since the exhaust gas is supplied to the branch path, the temperature of the exhaust gas rises due to the adiabatic compression effect, and the oxygen concentration also rises, thereby achieving good regeneration efficiency. Furthermore, the heat generated by the combustion auxiliary means further increases the exhaust gas temperature, so that the regeneration efficiency is further improved.

In addition, since a portion of the exhaust gas is discharged through the other branch path, deterioration of the engine operating condition is avoided and the operating conditions for filter regeneration are significantly eased, and the temperature of the filter on the non-regeneration side is This also means that when the filter is regenerated, the regeneration can be completed quickly.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. FIG. 1 is a diagram of an engine control system, FIG. 2 is an enlarged sectional view of FIG. FIG. 4 is a schematic sectional view showing the operation of the branch valve during filter regeneration, and FIG. 5 is a schematic sectional view showing the operation of the branch valve when back pressure increases during filter regeneration. 2... Exhaust system, 6... First branch route, 7... Second
Branch path, 9a...first filter, 9b...second filter, 10...first exhaust throttle valve, 11...second exhaust throttle valve, 19...exhaust heater (combustion auxiliary means) ,1
2... Branch valve (flow control valve).

Claims (1)

[Claims] (1) An exhaust particulate purification device for a diesel engine equipped with a particulate filter for collecting combustible particulates in the exhaust system, wherein the exhaust system is branched into two routes, and each branch route has the above-mentioned filter and particulate filter. , an exhaust throttle valve that changes the passage area on the downstream side of the filter, and combustion assisting means for the particulate matter collected in the filter, and one Exhaust particulate purification for a diesel engine, characterized in that it is equipped with a flow control valve that supplies exhaust gas to a branch path to which the filter belongs when the filter is regenerated, and also allows a part of the exhaust gas to flow into the other branch path. Device.