JPH04101013A - Exhaust emission control device for engine - Google Patents

Abstract

PURPOSE:To prevent cooling of a filter so as to surely perform the regeneration by raising temperature of the filter while guiding exhaust gas to the filter, or escaping exhaust gas to a by-pass passage, based on the result of comparison between the exhaust gas temperature at a part up branch point in the by-pass passage and the filter temperature. CONSTITUTION:The operation range of an engine (a) is divided into a self- reproducible range of a filter 32 by a means 37 and the load of the engine, and engine speed is detected by respective sensors 38, 39. Whether an operating condition belongs to the range other than the self-reproducible range or not is judged by a means 40. The regenerative time of the filter 32 is judged by a means 41, so that the regeneration of the filter 32 is started to operate a temperature rising device 33 by a means 42. The exhaust gas temperature at a part up the branch point in a by-pass pipe 34 is detected by a sensor 43 while the temperature of the filter 32 by a sensor 44, respectively, and whether the temperature of exhaust gas is higher than that of the filter 32 or not is detected by a means 45. Furthermore, if the temperature of the exhaust gas is higher for example, a by-pass valve driving device 36 is operated by a means 46 to close a by-pass valve 35 during operation of the temperature rising device 33.

Description

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

(Prior Art) Some diesel engines use a filter provided in the exhaust passage to collect particulates such as carbon contained in the exhaust gas so as not to release them into the exhaust gas. This requires the filter to be regenerated by periodically burning off the accumulated particulates.

Therefore, JP-A-59-85417 and JP-A-59-2
According to Publication No. 0515, a bypass valve is provided in a passage that bypasses the filter, and the inlet temperature of the filter is equal to or higher than the reburning temperature of particulates (for example, 400°C), and the outlet temperature of the filter does not melt the filter. The bypass valve is opened so that the temperature is below (for example, 600° C.) and only a certain amount of exhaust gas is guided to the filter regardless of the operating conditions at that time, thereby regenerating the filter.

Then, when the time considered necessary for filter regeneration has elapsed, it is determined that the filter regeneration has finished, or the flame has reached the rear end of the filter because the filter outlet temperature has exceeded a predetermined value (in other words, the flame has reached the rear end of the filter). Once the regeneration has finished, the bypass valve is closed.

(5Ns to be solved by the invention) By the way, in such a device, during filter regeneration,
Basically, #IFdt is used to bypass the exhaust gas, so it cannot be said that the filter is regenerated sufficiently, and regeneration takes a lot of time. for example,
Even if the exhaust gas temperature on the upstream side of the filter is higher than the filter temperature and the temperature of the filter could be further increased by guiding the exhaust gas to the filter, opening the bypass valve while the filter is regenerating will waste high-temperature space. In some cases, the system was bypassed.

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 reliably regenerates a filter.

(Means for Solving the Problems) Ml's invention, as shown in FIG. 1(A),
1, a device 33 for raising the temperature of this filter 32 (for example, one or both of an intake throttle device and an exhaust throttle device), and a passage that bypasses this filter 32. 34
, a bypass valve 35 that opens and closes this passage 34 , a drive device 36 for this bypass valve 35 , and an engine operating region that is divided into at least two regions, a self-renewable region of the filter 32 and the other regions, in accordance with the exhaust temperature. means 37 for detecting the engine load and a sensor 38 for detecting the engine load and rotation speed, respectively.
39, means 40 for determining whether the operating conditions determined from these detected values are in a region other than the self-renewable region, and means 41 for determining whether the filter 32 is in the regeneration period; means 42 for activating the temperature raising device 33 to start regeneration of the filter 32 when it is time for regeneration based on the determination result and the operating conditions are in a region other than the self-renewable region; and a branching of the bypass passage 34. A sensor 43 detects the exhaust gas temperature TeX upstream of the point, a sensor 44 detects the temperature of the filter 32 (for example, the internal temperature Tent or the outlet temperature), and the sensor 44 detects whether the exhaust temperature Tex is higher or lower than the filter temperature based on these detected values. and a means 45 for determining whether the exhaust temperature Tex is higher than the temperature Tex such that the bypass valve 35 is closed while the temperature raising device 33 is in operation when 4#×temperature Tex is higher than the determination result. If the temperature is lower than that of the bypass valve 3 while the temperature raising device 33 is in operation,
5 are opened, respectively, the bypass valve drive device 3
Means 46 for actuating 6 is provided.

The second invention, as shown in FIG. 1(B),
1, a device (for example, one or both of an intake throttle device and an exhaust throttle device) 33 that raises the temperature of this filter 32, and a passage that bypasses this filter 32. 34
, a bypass valve 35 that opens and closes this passage 34 , a drive device 36 for this bypass valve 35 , and an engine operating region that is divided into at least two regions, a self-renewable region of the filter 32 and the other regions, in accordance with the exhaust temperature. means 37 for detecting the engine load, and a sensor 38 for detecting the engine load and number of times.
39, means 40 for determining whether the operating conditions determined from these detected values are in a region other than the self-renewable region, means 41 for determining whether it is time for the filter 32 to be regenerated; means 42 for activating the temperature raising device 33 to start regeneration of the filter 32 when it is time for regeneration based on the determination result and the operating conditions are in a region other than the self-regeneration possible region; and a detected value of the engine load. means 47 for determining whether or not the current state is being accelerated; and means 47 for operating the bypass valve driving device 36 so that the bypass valve 35 is closed during acceleration and when the temperature raising device 33 is in operation based on the result of this determination; 48
and has been established.

(Operation) In the first invention, when the determination means 40.41 determines that the regeneration time has come and the operating conditions are in a region other than the region in which the filter 32 can self-regenerate, the regeneration start means 40.
2, the temperature raising device 33 is activated and regeneration of the filter 32 is started.

At this time, the exhaust gas temperature T upstream of the branch point of the bypass passage 34
ex and the filter temperature are compared, and if the exhaust gas temperature Tex is higher, the bypass valve 35 is closed and the high temperature wandering x is guided to the filter 32. As a result, the temperature increasing device 33
The filter temperature is raised more than if it were only activated by the filter.

Conversely, when the exhaust gas temperature Tex becomes lower, the bypass valve 35 is opened to prevent the filter from being cooled by the low-temperature exhaust gas.

In the second invention, the bypass valve 35 is closed during acceleration even when the temperature raising device is in operation. During acceleration, when a large output is required, it is expected that high-temperature exhaust gas higher than the filter temperature will be discharged.If the bypass valve 35 is closed from the stage of acceleration, the high-temperature exhaust gas during acceleration will be discharged to the filter 32 without delay in response. The temperature of the filter 32 is raised.

(Embodiment) FIG. 2 is a system diagram of an embodiment of the present invention. In the figure, 3 is a filter that collects particulates discharged from the engine 1.

In the figure, a so-called all-through type particulate material is shown, which has a high collection efficiency for VFI carbon, but an adhesion collection type particulate formed in a three-dimensional mesh shape may also be used.

A butterfly-type throttle valve 6 is provided in the intake passage 5, and a seven-diamond ram actuator 8 is connected to the intake throttle valve 6. A three-way solenoid valve 9 is interposed in the passage that communicates the pressure chamber of the actuator 8 with the negative pressure source, and when this solenoid valve 9 is turned from OFF to ON, the pressure chamber of the 7-mouth 2-actuator 8 is supplied with atmospheric pressure instead of atmospheric pressure. = Constant negative pressure is introduced, and the intake throttle valve 6
is closed to a certain opening. Note that the intake throttle valve 6 is of a normally open type.

Similarly, a throttle valve 11 is installed in the wandering passage 2 upstream of the filter 3.
However, a bypass valve 15 C is provided in a passage 14 that bypasses the filter 3 from upstream of this exhaust throttle valve 11, and these valves 11 and 15 are also equipped with a diamond 7 ram actuator 12.16 and a three-way solenoid valve 13.17. Driven by.

However, the throttle valve 11 is a normally open type, and the bypass valve 15 is a closed type, and these also have two positions (the throttle valve 11 has a closed position to a certain opening degree, a fully open position, and a closed position for the bypass valve 15).
For this, take the fully closed position and the fully open position.

The intake throttle valve 6 provided in this way and its driving device (8,
9) constitutes the intake throttle device, and the exhaust throttle 9 valve 11 and its drive device (12, 13) constitute the 41 throttle device, which together with the temperature raising auxiliary device (consisting of the heater 19 and its energizing device) to be described later. , each filter temperature increasing device works as a chair.

A heater 19 is provided on the front surface of the filter 3, and heats the filter 3 upon receiving an energization signal from the control unit 27.

21 is a semiconductor pressure sensor, which detects the differential pressure Δ across the filter 3.
Detect P. Temperature sensors 22 and 23 are thermocouples that respectively detect the exhaust gas temperature Tex and the filter internal temperature Tent upstream of the branching position of the bypass passage 14. The filter outlet temperature can also be used instead of this filter internal temperature.

24 is a sensor (crank angle sensor) that detects the rotation speed Ne of the engine 1; 25 is a sensor composed of a potentiometer that detects the accelerator opening (equivalent to engine load) Q; and 26 is a sensor that detects the cooling water temperature Tw. .

Signals from these sensors are input to a control unit 27 consisting of a microcomputer, which controls three three-way solenoid valves (9, 13, 17).
ON and OFF signals are output to the heater 19, and an energization signal is output to the heater 19, respectively.

FIG. 3 shows a routine for regenerating the filter 3, which is calculated at predetermined time intervals (for example, every 1011 Sees).

1. Determining the regeneration period In SL, engine speed N e t accelerator opening Q.

Read the exhaust gas temperature T ex, filter internal temperature Tant, cooling water temperature Tw, and differential pressure ΔP across the filter 3.

In S2, it is checked whether it is time for regeneration or not, and if it is determined that it is time for regeneration, the process proceeds to S3. In this case, the reproduction time is determined by the flag, and if it is the reproduction time, the flag is set.

This flag is set by comparing the actual pressure difference ΔP before and after the filter with the predetermined filter @rear pressure ΔP max at the collection limit, and if ΔP≧ΔP wax, it is determined that it is time for regeneration, and the flag is set. is set. The determination of the regeneration timing is not limited to this, but may also be based on the collection 1 history, travel distance, and travel time.

2. Determining the driving range In S3 and 89, it is determined in which range the driving condition determined by the accelerator opening Q and the engine speed Ne at that time is in. Here, as shown in FIG. 4, the operating range is roughly divided into three depending on the exhaust temperature.

Of these, A is caused by the fact that the exhaust gas temperature exceeds the reaction temperature of 5OF (organic soluble component, consisting of unburned fuel component and oil component) without operating each temperature raising device, and is induced by the reaction of SOF by the catalyst. This is the region where particulates are re-burned (the so-called self-regeneration region of the filter). Note that the reaction temperature of the SOF using the catalyst here is, for example, about 200° C. or higher, and the reburning temperature of the particulates using the catalyst is about 400° C. or higher.

On the other hand, B and C are regions in which the filter temperature cannot be raised to the regeneration temperature without activating the temperature raising device (B is by exhaust throttling and heater activation, and C is by exhaust throttling and heater activation). In addition to this, by restricting the intake air, the temperature can be raised above the reaction temperature of the SOF).

These divided areas are set in advance using, for example, a map.

3. Filter regeneration operation Depending on these three divided areas, the intake throttle device,
The filter is regenerated by selectively operating the temperature raising devices of the exhaust throttle I) device and the heater.

b) Region A In this case, the heater 19 is turned off in steps 84 to 6, and both the exhaust throttle valve 11 and the intake throttle valve 6 are opened. This is because in region A, the exhaust gas temperature reaches or exceeds the reaction temperature of the SOF, even if no temperature raising effect is expected by the heater, intake throttle, or exhaust throttle.

However, the bypass valve 15 is closed in S7. This is because bypassing exhaust gas in region A may worsen emissions.

(ii) B11 area In this case, S8. S14. S15. S1
? , 318, the heater is activated and the # thread valve is closed to a certain leap degree. This is because in the BtlI region, the temperature can be raised to 1. or higher than the SOF reaction temperature by exhaust throttling and heater operation.

In addition, in the B region and the CII region described later, the heater operation is added to the exhaust throttle and intake throttle to ensure that the temperature rises above the SOF reaction temperature, and if you rely only on the exhaust throttle and intake throttle, This is because combustion may become unstable and exhaust emissions and fuel efficiency may deteriorate. That is, the heater is energized in order to minimize the deterioration of exhaust emissions by reducing the amount of air flow and intake throttling in the B and C@ regions.

In S12, the exhaust temperature Tex is equal to the filter internal temperature Tant.
If Tex≧Tent, the bypass valve is closed in step 816. In this case, since the filter temperature can be further increased, regeneration is ensured by actively guiding high temperature waste to the filter.

On the other hand, if Tex<Tent, the bypass valve is opened in S19. This is because if the load fluctuates even during filter regeneration,
While the exhaust gas temperature Tex also changes from moment to moment, the filter internal temperature Tcnt does not change rapidly because the filter has a certain amount of heat capacity.
Due to a slight load drop within the B11I region, the exhaust temperature Te
There are operating conditions in which x is lower than the filter internal temperature T ant. In this case, if a stream with a temperature lower than its internal temperature is passed through the filter, it will cool the filter, so to prevent this, the exhaust air is bypassed and passed to keep the filter warm.

Further, in S10, it is checked whether the vehicle is accelerating or not, and even if the vehicle is accelerating, the bypass valve is closed at 31G.

This is because during acceleration, high-temperature exhaust gas is discharged, and by closing the bypass valve, the high-temperature exhaust gas is guided to the filter in a responsive manner.

Note that whether or not the vehicle is being accelerated may be determined by comparing the amount of change in the accelerator opening per certain period of time with a predetermined value.

(iii) C1i region This case is almost the same as the case in region B; the difference is that an intake throttle is added to the exhaust throttle and heater operation to raise the temperature above the SOF reaction temperature. The only point is that there is.

However, if Tex<Tent, the bypass valve is opened, so in response to this, the intake throttle valve is opened in S17 and the intake throttle is stopped. This means that when you throttle the intake air,
This is to prevent such soot from being directly discharged from the bypass passage, since the composition of soot deteriorates due to combustion instability.

4. In determination S23 of the end of reproduction, the timer value T i+*erA is incremented. In this case, the timer value T'imerA represents the time since the playback operation was started.

In S24, this timer value TimerA and the predetermined value Time
If TimerA≧TimeB, it is determined that the filter regeneration has been completed, and the timer value T is
imerA is cleared and the end of playback is set in S26. In other words, until the end of playback is indicated in step 526, it is determined that it is time to play, so the above playback operation continues. When the end of playback is indicated, it is assumed that the time for playback has come and gone, and the process advances from B2 to 327 onwards.

5. Post-processing In steps 527-S32, post-processing is performed and the particulates are returned to a state where they can be collected by a filter (827-S3
0, all temperature raising devices are stopped, the entire amount of exhaust gas is guided to the filter, and S31. In S32, the end of playback is reset and the timer value TimerA is cleared).

This concludes the explanation of the filter regeneration operation. Figure 1 (A
), in correspondence with FIG. 1(B), B2 is the reproduction time determining means 41, B3 or B9 is the area determining means 40, S14.
S15,517=S18 or S20, S21. S17
．． S18 is the reproduction start means 42, S12 or S13 is the determination means 45, S16. S19 or S22. S19 is the actuation means 46, and S10 or Sll is the acceleration determination means 47.
．． 316 or S22 fulfills each function of the actuating means 48.

Here, the operation of this example will be explained.

When it is determined that the regeneration period is reached and the operating conditions are in the B and C@ ranges, the temperature raising device is activated and the filter 3
starts playing.

At this time, the exhaust gas temperature T upstream of the branch point of the bypass passage 14
ex and the internal temperature T cnt of the filter 3 are compared, and if the exhaust gas temperature Tex is higher than the filter internal temperature T cnt, the bypass valve 15 is closed and the high temperature exhaust gas is guided to the filter 3 . This causes the filter temperature to be higher than if only due to activation of the temperature raising device.

Conversely, the exhaust temperature Tex is equal to the filter internal temperature Tc n
When the temperature drops below t, the bypass valve 15 is opened to prevent the filter from being cooled by the cold exhaust gas, so that the regeneration reaction induced by the operation of the heating device is inhibited by subsequent changes in load conditions. That (
For example, if the amount of heat removed from the filter by the exhaust flow accompanying an increase in load becomes greater than the amount of heat generated by the reaction in the filter, the regeneration reaction in the filter will end prematurely.

In this way, by actively guiding the high-temperature exhaust air as much as possible to raise the temperature of the filter above its current temperature while preventing the filter from cooling, the filter that has started regeneration is maintained at a high temperature at which it can be regenerated. The regeneration will be carried out reliably. As a result, the time required for filter regeneration can be shortened, and when the regeneration time is shortened, the time for energizing the heater and the time for intake and exhaust throttling are also shortened.
Deterioration of fuel efficiency and drivability during regenerative operation can also be minimized.

On the other hand, according to this example, the bypass valve 15 is closed not only when Tex≧T ant, but also during acceleration. During acceleration, which requires a large engine output, it is expected that exhaust gas with a temperature higher than that of the Tent will be discharged as a result, so if the bypass valve 15 is closed from the stage of acceleration, the high temperature exhaust gas will be filtered without leaking. Leads to 3.

If the bypass valve is closed by feeding back the actual exhaust gas temperature Tex detected by the temperature sensor 22, a delay will inevitably occur during transient times such as during acceleration.
We are trying to improve this point as much as possible.

In contrast, in the conventional example, the bypass valve is opened so that the temperature of the filter itself is maintained within the regeneration range.
As long as the temperature of the filter itself was not within the regeneration range, no matter how high the exhaust gas temperature upstream of the filter was, it would not be guided to the filter.

In addition, in the example, in order to maintain the filter in a high temperature state, even though the exhaust gas is bypassed when Tex<Tent in region C, intake throttling is stopped to prevent the wandering x composition from worsening. Therefore, the exhaust gas emitted from the bypass passage has little negative impact on the environment. In this sense, many particulates may be discharged to area A (for example, under high load), so
If the bypass passage is open, particulates will be released into the large current, causing a problem, but according to this example,
In the All region, the bypass valve is closed and the entire amount of exhaust gas is guided to the filter to prevent particulates from being released even during regeneration operation.

(Effects of the Invention) In the first invention, in the region where the temperature raising device is activated, based on the comparison result of the exhaust temperature upstream of the bypass passage branch and α and the filter temperature, if the exhaust temperature is higher, the filter is regenerated. Even if the exhaust gas is inside, the exhaust gas is guided to the filter to raise the temperature of the filter, and conversely, when the exhaust temperature is lower, the exhaust gas is released to the bypass passage to prevent the filter from cooling down, ensuring that the filter can be regenerated. It is done.

In the vLJ2 invention, the bypass valve is closed during acceleration in the area where the temperature raising device is activated, so that the high temperature exhaust gas during acceleration does not leak (it is led to the filter, which reduces the temperature raising effect of the filter). can be increased.

[Brief explanation of drawings]

1(A) and 1(B) are claims correspondence diagrams of each invention, FIG. 2 is a system diagram of one embodiment, FIG. 3 is a flowchart for explaining the control operation of this embodiment, and FIG. FIG. 4 is an operating range diagram of this embodiment. DESCRIPTION OF SYMBOLS 1... Engine, 2... Exhaust passage, 3... Filter, 5... Intake passage, 6... Intake throttle valve, 8...
・Dia 7 ram actuator, 9... three-way solenoid valve,
11... Exhaust throttle valve, 12... Gui 77 ram actuator, 13... Three-way solenoid valve, 14... Bypass passage, 15... Bypass valve, 16... Dia 7 ram actuator eta, 17... Three-way solenoid valve, 19... Heater 21... Pressure sensor, 22... Exhaust temperature sensor, 23... Filter internal temperature sensor, 24...
Crank angle sensor, 25...Accelerator opening sensor (engine load sensor), 26...Water temperature sensor, 27...
・Control unit, 31...Exhaust passage, 32・
...filter, 33...temperature raising device, 34...bypass passage, 35...bypass valve, 36...bypass valve driving device, 37...area division means, 38...
Engine load sensor, 39... Engine rotation speed sensor, 40... Region determining means, 41... Regeneration timing determining means, 42... Regeneration start means, 43... Wandering x temperature sensor, 44... - Filter temperature sensor, 45...M leg means, 46...operation means, 47...acceleration determination means,
48... Actuation means. Figure 1 (A) Figure 1 (B)

Claims (2)

[Claims] 1. A filter that is installed in an exhaust passage and collects particulates in the exhaust, a device that raises the temperature of this filter, a passage that bypasses this filter, a bypass valve that opens and closes this passage, and a drive device for this bypass valve. and,
Means for dividing the operating range of the engine into at least two regions, a self-regenerating range for the filter and the other regions according to the exhaust temperature, a sensor for detecting the engine load and rotation speed, and an operation determined from these detected values. means for determining whether the conditions are in an area other than the self-renewable area; means for determining whether it is time for the filter to regenerate; means for activating the temperature raising device to start regeneration of the filter when the temperature is in a region other than the self-renewable region; a sensor for detecting the exhaust temperature upstream of the branch point of the bypass passage; and a sensor for detecting the temperature of the filter. a sensor for determining whether the exhaust gas temperature is higher or lower than the filter temperature based on these detected values; and a means for determining whether the exhaust gas temperature is higher or lower than the filter temperature based on the detected values; means for operating the bypass valve drive device so that the bypass valve is closed and, conversely, when the exhaust gas temperature is lower and the bypass valve is opened while the temperature increasing device is operating. Features an engine exhaust purification device. 2. A filter that is installed in an exhaust passage and collects particulates in the exhaust, a device that raises the temperature of this filter, a passage that bypasses this filter, a bypass valve that opens and closes this passage, and a drive device for this bypass valve. and,
Means for dividing the operating range of the engine into at least two regions, a self-regenerating range for the filter and the other regions according to the exhaust temperature, a sensor for detecting the engine load and rotation speed, and an operation determined from these detected values. means for determining whether the conditions are in an area other than the self-renewable area; means for determining whether it is time for the filter to regenerate; means for activating the temperature raising device to start regeneration of the filter when the temperature is in a region other than the self-renewable region; means for determining whether the engine is accelerating from the detected value of the engine load; and based on the determination result. An exhaust purification device for an engine, comprising means for operating the bypass valve driving device so that the bypass valve is closed during acceleration and while the temperature raising device is in operation.