JPH03233119A - Exhaust gas purifier of engine - Google Patents

Abstract

PURPOSE:To prevent a trap from being clogged by enlarging an operating area which introduces exhaust gas into a trap at regeneration timing, and regenerate the trap by a temperature raising device in the operating area. CONSTITUTION:A control unit 21 estimates the accumulating amount of particulates, which are caught by a catalytic trap 3, based on the output of a pressure sensor 15 detecting the difference between upstream pressure and the downstream pressure of the trap 3 and then judges regeneration timing of the trap. When it is judged as regeneration timing, the operating area where a throttling valve 5 is fully opened and a throttling valve 6 is fully closed by throttling valve driving devices 7, 8 is shifted to a low speed and low load side. Besides, an intake air throttling valve 10 and an exhaust gas throttling valve 11 are closed by throttling valve driving devices 12, 13 in the operating area enlarged further. With this constitution, regeneration of the trap 3 can be carried out efficiently even if the area which makes exhaust gas flow into the trap 3 is enlarged. It is thus possible to prevent the trap 3 from being clogged even if the engine has a large amount of discharged carbon.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an engine exhaust purification device.

(Conventional technology) Diesel engines emit particulates, so exhaust gas is purified by collecting them in a trap with a catalyst installed in the exhaust passage. By re-burning the particulates at high speeds and high loads (350 to 400 degrees Celsius) or higher, the traps are unclogged and the ennon is not affected.
(See Publication No. 35).

(Problem to be solved by the invention) By the way, in such a device, if it is not used in a high-speed, high-load range, there is less chance of re-burning the particulates, so the particulates will continue to accumulate and the trouble will increase.・Sometimes it is unavoidable that the knob becomes clogged.

In order to prevent such clogging, as shown in FIG. 8, a trap 3 with a catalyst is used, in which the outlets and inlets of a plurality of channels 3A are alternately sealed, and a catalyst device 4 having a plurality of channels 4A.
We have previously proposed a device in which the exhaust gases are arranged in parallel in the exhaust passage to selectively guide the exhaust gas depending on the operating conditions (Patent Application No.
No. 146580).

This is because particulates are broadly divided into carbon (including sulfate) and organic soluble components (5OF) (unburnt fuel components and oil components), and the operating range where large amounts of each of these two components are emitted is shown in Figure 9. The difference is that in the high-speed, high-load range, the carbon ratio is dominant, while in the low-medium speed load range, the carbon content is less so (SOF is more dominant; this focuses on α). .

For example, in Fig. 10, region I is set as a high-speed, high-load region where the exhaust temperature has sufficiently reached the trap regeneration temperature, and the operating conditions determined from the engine load Q and rotational speed Ne are in this region ■ If the throttle valve 5 on the trap side is fully opened and the throttle valve 6 on the catalyst device side is fully opened to allow the entire amount of exhaust gas to flow into the trap 3, the carbon that is dominant in this region I will flow into the trap 3. Since it is collected and re-burned continuously and quickly, no clogging occurs.

On the other hand, when the operating conditions are in the low-medium speed load range H shown in Fig. 10, the throttle valve 5 on the trap side is fully opened, the throttle valve 6 on the catalyst device side is fully open, and the entire amount of exhaust gas is reduced. is passed through the catalyst device 4 without plugging.

Since the exhaust gas in this region (2) has a temperature sufficient to oxidize the SOF (approximately 200° C. or higher), the SOF that is dominant in this region (2) is oxidized by the catalyst device 4.

In this case, since the catalyst device 4 is not sealed, the exhaust gas flows straight through the flow path 4A, so that carbon is discharged downstream without being captured by the catalyst device 4. Therefore, even if the catalyst is often used in this region (3), the catalyst device 4 will not be clogged with carbon. Note that the absolute amount of carbon released into the atmosphere is small, so it does not pollute the environment.

In this way, it is possible to reduce the amount of ticulate while preventing clogging.

Now, in an engine that emits a large amount of carbon, the carbon is not directly released into the atmosphere (1) In Fig. 10, it is necessary to expand region I to the low and medium speed load range. If it is expanded to the low-medium speed load range, the exhaust temperature will drop accordingly, making it impossible to regenerate the trap, so it cannot be simply expanded.

For this reason, if an engine that emits a large amount of carbon is operated near the boundary with region (1), the tiger knob may not be regenerated sufficiently and may become clogged.

In addition, immediately after the operating conditions jump into region I due to sudden acceleration, even if the exhaust gas temperature has reached a temperature sufficient for regeneration, the trap will not heat up sufficiently due to the trap capacity, so in this case as well. Regeneration is difficult. For this reason,
Repeated acceleration and deceleration may cause the amount of carbon deposited to reach the burnout limit.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a device that prevents trap clogging even with ennon, which discharges a large amount of carbon.

(Means for Solving the Problems) As shown in FIG. 1, the present invention provides an exhaust vent I! A trap 32 is installed in one of the branch passages 31A and has a plurality of flow passages, and a trap 32 is installed in the other branch passage 31B and has a plurality of flow passages.
, a means 34 for switching the introduction of exhaust gas into the two branch passages 31A and 31B, a device 35 for raising the temperature of the trap 32, and a device 35 for changing the operating range to a high speed and high load range with the regeneration temperature of the trap 32 as a boundary. Means 36 for dividing into two areas, I and low-medium speed load range■, and the actual load Q and rotational speed N of the ennon.
sensors 3, 7, and 38 for detecting e, respectively, means 39 for determining which of the two operating ranges I and H the operating conditions determined from these detected values belong to, and high-speed and high-load range I. The exhaust gas introduction switching means 34 is controlled so that the exhaust gas flows to the trap 32 when it is determined that the load is in the low-medium speed load range, and to the catalyst device 33 when it is determined that the load is in the low-medium speed load range. means 40 for determining whether or not the playing card 32 is in a regeneration period; and means 41 for determining whether or not the playing card 32 is at a regeneration time; Means 42 divides the operating range by shifting to 0. Similarly, at regeneration time, means 43 determines whether or not the operating conditions determined from the detected value are in the range expanded by this shift. Temperature raising device 35
means 44 for activating the .

(Operation) When it is determined that it is time to regenerate the trap 32, a regeneration operation is started.

In this case, since the temperature raising device 35 for the trap 32 is provided, the operating range in which the trap 32 reaches the regeneration temperature is expanded. Therefore, during the playback operation, the boundary shift means 4
Even if the region through which exhaust gas flows into the trap is expanded in step 2, the trap can be efficiently regenerated.

(Embodiment) FIG. 2 is a system diagram of an embodiment, and the basic configuration is the same as the previously proposed device. In the figure, exhaust passage 2 is
A trap 3 with a catalyst is installed in one branch passage 2A, and a catalyst device 4 is installed in the other branch passage 2B.

A large number of flow channels 3A are formed in the catalyst trap 3 by a honeycomb-like lattice made of a porous member such as ceramic, and the outlets and inlets of the flow channels 3A are alternately sealed with sealing materials 3B. On the other hand, although the catalyst device 4 also has a large number of upward flow passages 4A formed in a honeycomb-like lattice made of a porous member such as ceramic, all of the flow passages 4A are not sealed.

Butterfly-type throttle valves 5 and 6 are installed downstream of the trap 3 and the catalyst device 4, respectively.
, 6 is a throttle valve drive device 7, which is provided correspondingly.
8.

In this case, the throttle valve drive device 7.8 is composed of, for example, a negative pressure control valve, a diamond 7 ram actuator, or a stevening motor. The corresponding throttle valves 5 and 6 are driven to take two positions.

The throttle valves 5, 6 and their drive devices 7, 8 constitute the exhaust gas introduction switching means 34 shown in FIG.

Note that the throttle valves 5 and 6 may be installed upstream of the trap 3 and the catalyst device 4. The two branch passages 2A and 2B meet downstream of the throttle valve 5.6.

On the other hand, normally open butterfly-type throttle valves 10 and 11 are interposed in the intake passage 9 and the exhaust passage upstream of the branch point, respectively, and these throttle valves 10 and 11 are driven by a throttle valve drive device 12 provided correspondingly. , 13. These throttle valves 1
0 and 11 and their driving devices 12 and 13 constitute the temperature raising device 35 in FIG.

15 is a semiconductor pressure sensor, which detects the differential pressure Δ across the trap 3.
Detect P. A sensor 16 includes a potentiometer and detects the accelerator lever opening (enron load) Q, and a sensor 17 detects the rotational speed Ne of the engine 1 (crank angle sensor).

Signals from these sensors 15 to 17 are input to a control unit 21 consisting of a microcomputer.
The control unit 21 outputs opening/closing signals to the four drive devices 7.8, 12.13 as shown in FIG.

FIG. 4 shows a routine executed by the CPU of the control unit 21.

Before explaining this routine in detail, an outline of the control will be described. For engines with relatively high carbon emissions, the 10th
In the figure, if the operation near the boundary with area (3) is prolonged, the trap will not be regenerated sufficiently and may become clogged. Therefore, in this example, it is determined whether the trap is clogged, that is, whether it is time to regenerate the trap, and when the regeneration time comes, the trap temperature raising device is activated to regenerate the trap.

In this case, if a temperature raising device is used, the operating range in which the trap reaches the regeneration temperature is widened. Therefore, when performing a regeneration operation, as shown in Figure 3, if the flow path switching line is significantly shifted from the dashed line position to the dashed-dotted line position toward the medium-speed load range side, trap regeneration can be efficiently performed. It can be carried out. Note that after the regeneration is completed, the flow path switching line is returned to the original position indicated by the broken line.

Returning to FIG. 4, at Sl, the accelerator lever opening degree Q and rotational speed Ne are read.

S2 is S7-S9. Along with S20, this part determines whether or not it is the reproduction time, and functions as the reproduction time determination means 41 in the tJS1 diagram. In S2, it is checked whether it is the playback time or not, and if it is determined that it is not the playback time, the process advances to S3.

In this case, the reproduction time is determined based on the value of 7 lag F, and if it is not the reproduction time, F=0.

In S3, the flow path switching map A shown in FIG. 5 is read out.

This map A has the same characteristics as in FIG. 10, and the boundary corresponds to the regeneration temperature of the trap. The map in Figure 5 is ROM
This ROM performs the function of means 36 for operating range classification in FIG.

S4, together with S12, is a part that performs the function of the driving range determining means 39 shown in FIG. Here, we check to which region I or II shown in Fig. 5 the operating conditions determined from the engine load Q and rotational speed Ne belong, and if it is in the high-speed, high-load region I, we proceed to S5; If the load is in the fast load range ■, proceed to S6.

S5 and 86 are parts that perform the function of the control means 40 in FIG. First, in S5, the throttle valve 5 on the trap side is fully opened, and the throttle valve 6 on the catalyst device side is fully opened to allow the entire amount of Wandering x to flow into the trap 3.

In S6, the throttle valves 5 and 6 are operated in the opposite direction to allow the entire amount of exhaust gas to flow into the catalyst device 4.

In S7, a map of the differential pressure ΔP wax at the trap collection limit is read out.

In S8, this map is searched based on the rotation and load at that time, and compared with the differential pressure ΔP at the edge. And ΔP≧ΔP m
If it is ax, it is determined that it is time for reproduction, and the process proceeds to S9. S
At 9, a flag is set (F=1).

In S10, the temperature raising device of the trap 3 is kept inactive (the intake throttle valve 10 and the exhaust throttle valve 11 are opened).
.

On the other hand, if it is determined in S2 that it is time for regeneration, S11
Proceed to.

Sll is a portion that performs the function of the boundary shifting means 42 in FIG. 1, and here, instead of the map A in FIG. 5, the channel switching map B in FIG. 6 is read out. In this map B, the boundary between the two regions r' and n' is shifted more toward the medium speed load region than in the case of FIG.

S12 to S14 are similar to S4 to S6.

However, if the operating conditions are in the area ■', S15
Proceed to.

S15 and 316 are parts that perform the function of the enlarged area determining means 43 in FIG. At S15, map C in FIG. 7 is read out. In Figure 7, area 1' in Figure 6 and area ■ in Figure 5 are shown.
The area of difference between the two, that is, the area where the exhaust gas flows into the trap is expanded, is set as b. Note that area a is equal to area I in FIG.

At step 316, it is checked whether the operating conditions determined from the load Q and the rotational speed Ne of the ennon belong to the range shown in FIG. 7. If the operating conditions are within the range shown in FIG.

S17 is a part that performs the function of the actuating means 44 in FIG.
Here, both intake and exhaust are throttled. Through these operations, the exhaust gas temperature is raised to the regeneration temperature of the trap, and the trap 3 is regenerated.

In step 318, the playback time is counted, and the process advances to step S19. S1
9, the counted playback time is set to a predetermined time (for example, 10
If a predetermined period of time has elapsed, it is determined that the playback has ended and the process proceeds to S20. In S20, lower the 7 lag F.

Here, the operation of this example will be explained.

When it is determined from the differential pressure across the trap 3 that it is time to regenerate the trap 3, a regeneration operation is started.

In this case, since a trap temperature raising device is provided,
The operating range in which Trap 7 reaches the regeneration temperature is expanded. Therefore, even if the region through which exhaust gas flows into the trap 7 is expanded as shown in FIG. 3 during the regeneration operation, the trap can be regenerated efficiently. Therefore, even if Ennon, which emits a large amount of carbon, is continuously operated near area H, the trap will be regenerated sufficiently using the temperature raising device when it comes time for regeneration operation. , never get stuck.

Although regeneration operations using the heating device are required, the traps are efficiently regenerated, so the frequency of use is extremely small, and therefore the negative impact on engine performance due to operating the heating device is minimal. It is kept to a minimum.

In the embodiment, the regeneration timing is determined based on the differential pressure across the trap, but it may also be determined based on the known driving history (integrated value of engine rotational speed, immediate departure from running, etc.).

The temperature raising device for the trap is not limited to that of the embodiment, and any device that increases the trap temperature may be used, such as only an intake throttle, an exhaust throttle, or a heater provided at the trap inlet. Furthermore, the flow path can be switched using a single throttle valve provided at a branch point of the exhaust path.

(Effects of the Invention) This invention expands the operating range in which wandering is introduced into the trap at the time of regeneration, and in this expanded range, the trap is regenerated using a temperature raising device. Even if the engine has a large amount of emissions, the trap will not become clogged.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of this invention, Fig. 2 is a system diagram of one embodiment, Fig. 3 is a region diagram showing changes in the flow path switching line in this embodiment, and Fig. 4 is a diagram of this embodiment. Flowcharts for explaining control operations, and FIGS. 5 to 7 are area diagrams showing the contents of the map used in FIG. 4. FIG. 8 is a system diagram of the previously proposed device, FIG. 9 is a characteristic diagram of the particulate emission amount with respect to ennon load of the previously proposed device, and FIG. 10 is an operating range diagram of the previously proposed device. 1... Engine, 2... Exhaust passage, 2 A, 2 B
... Branch passage, 3... Trap with sealed catalyst, 4... Catalyst device, 5, 6... Throttle valve, 7, 8...
... Throttle 9 valve drive device, 10... Intake throttle valve, 11...
・Exhaust throttle valve, 12.13... Throttle valve drive device, 15
... Pressure sensor, 16... Accelerator lever opening sensor (engine load sensor), 17... Engine speed sensor, 21... Control unit, 31...
1 exhaust, 31A. 31B... Branch passage, 32... Sealed trap, 33... Catalyst device, 34... Exhaust introduction switching means,
35... Temperature raising device, 36... Operating range classification is means, 3
7... Engine load sensor, 38... Engine rotation speed sensor, 39... Operating range determining means, 40... Control means, 41... Regeneration timing determining means, 42... Boundary shift means, 43... Expansion area determination means, 44... Actuation means.

Claims (1)

[Claims] a trap that is interposed in one of the two branched exhaust passages and alternately seals the outlets and inlets of the plurality of flow passages; a catalyst device that is interposed in the other branched passage and has the plurality of flow passages; means for switching the introduction of exhaust gas into two branch passages, a device for raising the temperature of the trap, and a regeneration temperature of the trap that divides the operating range into two, a high-speed, high-load range and a low-medium-speed load range. a sensor for detecting the actual engine load and rotational speed, a means for determining which of the two operating ranges the operating conditions determined from these detected values belong to, and a high-speed, high-load range. means for controlling the exhaust gas introduction switching means so that the exhaust gas flows into the trap when it is determined that the speed is in the low-medium speed load region, and to the catalyst device when it is determined that the speed is in the low-medium speed load region; means for determining whether or not the trap is in a regeneration period; and a means for determining whether or not the trap is in a regeneration period, and shifting the boundary to a medium speed load area to expand the operation range so that the operation range where exhaust gas flows to the side of the trap expands at the time of regeneration. means for classifying, means for determining whether the operating conditions determined from the detected value are in a region expanded by this shift at the regeneration time, and means for operating the temperature raising device in this expanded region. An engine exhaust purification device characterized by being provided with an engine exhaust purification device.