JPH04358714A - Exhaust purifying device for engine - Google Patents

Abstract

PURPOSE:To regenerate certainly a filter for collecting particles in exhaust, in the exhaust purifying device of an engine. CONSTITUTION:In a range where the temperature rising device 33 of a filter 32 is operated, a bypass valve 35 is closed only for a prescribed period at the time of acceleration to lead exhaust to the filter 32, and the bypass valve 35 is opened in the case where an exhaust temperature is lower than the temperature of the filter 32 after lapse of the prescribed time so as to prevent cooling of the filter 32.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust purification device.

0002

2. Description of the Related 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 atmosphere. This requires the filter to be regenerated by periodically burning off the accumulated particulates.

Therefore, according to Japanese Patent Laid-Open No. 59-85417 and Japanese Patent Laid-open No. 59-20515, a bypass valve is provided in the passage that bypasses the filter, and the inlet temperature of the filter is adjusted to the particulate reburning temperature ( For example 4
bypass so that the temperature at the outlet of the filter is higher than 00℃) and lower than the temperature that will not damage the filter (e.g. 600℃), and only a certain amount of exhaust gas is guided to the filter regardless of the operating conditions at that time. The valve is opened, thereby regenerating the filter.

[0004] When the time considered necessary for filter regeneration has elapsed, it is determined that the filter regeneration has been completed, 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 bypass valve is closed when the regeneration of the filter is completed.

[0005]

[Problem to be Solved by the Invention] Incidentally, in such a device, the exhaust gas is basically bypassed and allowed to flow during filter regeneration, so that the filter is regenerated sufficiently. However, it took a lot of time to play. 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 that exhaust gas to the filter, opening the bypass valve while the filter is being regenerated can reduce the high temperature exhaust gas. There were times when the system was bypassed unnecessarily.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a device for reliably regenerating a filter.

[0007]

[Means for Solving the Problems] As shown in FIG. 1, the present invention includes a filter 32 which is interposed in an exhaust passage 31 and collects particulates in the exhaust gas, and a device (for example, (one or both of an intake throttle device and an exhaust throttle device) 33, a passage 34 that bypasses this filter 32, a bypass valve 35 that opens and closes this passage 34, a drive device 36 for this bypass valve 35, and an operating range of the engine. means 37 for dividing the filter 32 into a self-renewable region and at least two other regions according to the exhaust temperature, sensors 38 and 39 for detecting the engine load and rotation speed, respectively, and the detection value determined from these detected values. means 40 for determining whether the operating conditions are in a region other than the self-renewable region; means 41 for determining whether it is time for regeneration of the filter 32; When the operating conditions are in a region other than the self-renewable region, the temperature increasing device 33
means 42 for activating the regeneration of the filter 32;
a means 43 for determining whether or not the engine is being accelerated from the detected value of the engine load; a means 44 for measuring an elapsed time TimerC from the time of acceleration determination; a sensor 46 for detecting the exhaust temperature Tex upstream of the branch point of the bypass passage 34;
a sensor 47 for detecting the temperature of the filter 32 (for example, internal temperature Tcnt or outlet temperature); means 48 for determining whether the exhaust temperature Tex is higher or lower than the filter temperature Tcnt based on these detected values; The bypass valve 35 is closed while the temperature raising device 33 is in operation while the elapsed time TimerC does not exceed the predetermined time TimeD, while the elapsed time TimerC from the acceleration determination exceeds the predetermined time TimeD and the When the exhaust gas temperature Tex is higher than the filter temperature Tcnt, the bypass valve 35 is closed while the temperature raising device 33 is in operation, and conversely, when the exhaust gas temperature Tex is lower than the filter temperature Tcnt, the bypass valve 35 is closed. Means 49 are provided for respectively operating the bypass valve drive device 36 so that the bypass valve 35 is opened during operation of the temperature raising device 33.

[0008]

[Operation] When the determining means 40 and 41 determine that it is time for regeneration and the operating conditions are outside the range in which the filter 32 can self-regenerate, the regeneration starting means 42 activates the temperature raising device 33. Regeneration of the filter 32 is started.

During acceleration, the bypass valve 34 is forcibly closed. During acceleration, which requires large output, it is predicted that exhaust gas with a temperature higher than the filter temperature will be exhausted.
If the bypass valve 35 is closed from the stage of acceleration, the high-temperature exhaust gas at the time of acceleration is guided to the filter 32 without response delay, and the temperature of the filter 32 is increased.

As a result, the internal temperature of the filter 32 rises due to the heat generated by the regeneration reaction of the filter 32 immediately after acceleration, but after a predetermined time period TimeD has elapsed after acceleration, the exhaust gas temperature T upstream of the branch point of the bypass passage 34 increases.
ex and filter temperature Tcnt are compared. Exhaust temperature T
When ex is higher, the bypass valve 35 is closed and the high temperature exhaust gas is guided to the filter 32. As a result, the filter temperature is increased more than when the temperature raising device 33 is operated only.

On the other hand, when the exhaust gas temperature Tex becomes lower, the bypass valve 35 is opened and the filter 32 is not cooled by the low-temperature exhaust gas.

0012

Embodiment FIG. 2 is a system diagram of one embodiment of the present invention. In the figure, 3 is a filter that collects particulates discharged from the engine 1. Although the figure shows a so-called wall-through type of particulates, which has a particularly high carbon-collecting efficiency, it may also be an adhesion-collecting type formed into a three-dimensional network.

A butterfly-type throttle valve 6 is provided in the intake passage 5, and a diaphragm 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 on from OFF, a constant pressure is applied to the pressure chamber of the actuator 8 instead of atmospheric pressure. Negative pressure is introduced,
The intake throttle valve 6 is closed to a certain opening degree. Note that the intake throttle valve 6 is of a normally open type.

Similarly, the exhaust passage 2 upstream of the filter 3
A bypass valve 15 is provided in a passage 14 that bypasses the filter 3 from upstream of the exhaust throttle valve 11, and these valves 11 and 15 are also operated by diaphragm actuators 12 and 16 and three-way solenoid valves 13 and 17. Driven. However, the throttle valve 11 is normally open, and the bypass valve 1
5 is a normally closed type, and these also take two positions (the throttle valve 11 has a position closed to a certain degree of opening and a fully open position, and the bypass valve 15 has a fully closed position and a fully open position).

The intake throttle valve 6 and its driving device (8, 9) provided in this manner serve as an intake throttle device and an exhaust throttle valve 1.
1 and its driving device (12, 13) constitute an exhaust throttling device, which together with a temperature raising auxiliary device (consisting of a heater 19 and its energizing device) to be described later, work as each temperature raising device of the filter.

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, and filter 3
The differential pressure ΔP before and after is detected. Temperature sensors 22 and 23 are thermocouples that detect the exhaust gas temperature Tex and the filter internal temperature Tcnt upstream of the branching position of the bypass passage 14, respectively. 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. It is a sensor.

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

FIGS. 3, 4, and 5 show routines for regenerating the filter 3 at predetermined intervals (for example, every 10 m).
sec).

1. Determining when to play

In S1, the engine speed Ne, accelerator opening Q, exhaust temperature Tex, filter internal temperature Tcnt, cooling water temperature Tw, and differential pressure ΔP across the filter 3 are read.

[0023] In S2, it is checked whether it is playback time or not.
If it is determined that it is time for regeneration, the process advances to S3. In this case, the reproduction time is determined by the flag, and if it is the reproduction time, the flag is set.

[0024] Furthermore, this flag indicates the difference between the actual differential pressure across the filter ΔP and the differential pressure across the filter ΔP at the predetermined collection limit.
By comparison with Pmax, if ΔP≧ΔPmax, it is determined that it is time for regeneration, and a flag is set. The determination of the regeneration timing is not limited to this, and may be based on the collected amount history, travel distance, and travel time.

2. Determination of operating area

In S3 and S9, it is determined in which region the operating condition determined from the accelerator opening degree Q and engine rotational speed Ne at that time falls. Here, the driving area is
As shown in FIG. 4, it is roughly divided into three categories depending on the exhaust temperature.

Among these, A is such that the exhaust gas temperature becomes higher than the reaction temperature of SOF (organic soluble component, consisting of unburned fuel component and oil component) without operating each temperature raising device, and the reaction of SOF by the catalyst occurs. This is a region where particulates are re-burned due to the re-burning of particulates (so-called self-regeneration region of the filter 3). 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 unless the temperature raising device is operated (B is by exhaust throttle and heater operation, and C is by exhaust throttle and heater operation). (areas in which the temperature can be raised above the reaction temperature of SOF by controlling the intake air in addition to heater operation).

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

3. Filter regeneration operation

The filter 3 is regenerated by selectively operating the temperature raising devices of the intake throttle device, the exhaust throttle device, and the heater 19 according to the three divided regions.

(i) Area A

In this case, in S4 to S6, the power supply to the heater 19 is cut off, 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 becomes equal to or higher than the reaction temperature of the SOF even if no temperature raising effect is expected by the heater 19, 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) Area B

In this case, S8, S15, S16, S
18. In S19, the heater 19 is activated, and
The exhaust throttle valve 11 is closed to a certain opening degree. This is because in region B, the temperature can be raised to a temperature higher than the reaction temperature of the SOF by operating the exhaust throttle and the heater 19.

Note that in region B and region C, which will be described later, the operation of the heater 19 is applied to the exhaust throttle and intake throttle in order to ensure that the temperature rises above the reaction temperature of the SOF. This is because relying only on the engine may make combustion unstable and worsen exhaust emissions and fuel efficiency. That is, the heater 19 is energized in order to minimize the deterioration of exhaust emissions by reducing the amount of throttle of the exhaust and intake air in regions B and C.

In S14, it is checked whether the exhaust gas temperature Tex is higher than the filter internal temperature Tcnt, and Tex≧Tc is determined.
nt, the bypass valve 15 is closed in S17. In this case, since the filter temperature can be further increased, regeneration is ensured by actively guiding high temperature exhaust gas to the filter 3.

On the other hand, if Tex<Tcnt, the bypass valve 15 is opened in S20. This is because when the load fluctuates during filter 3 regeneration, the exhaust temperature Tex also changes moment by moment, whereas the filter internal temperature Tcnt does not change suddenly because the filter has a certain amount of heat capacity. Therefore, there is an operating condition in which the exhaust gas temperature Tex becomes lower than the filter internal temperature Tcnt due to a slight load reduction within the B region. In this case, if a large amount of exhaust gas with a temperature lower than its internal temperature is allowed to flow through the filter 3, the filter 3 will be cooled down, so in order to prevent this, the exhaust gas is passed through the filter 3 in a bypass manner to keep the filter 3 warm.

[0040] In S10, it is checked whether it is during acceleration or not.
Even during acceleration, the bypass valve 15 is closed in S16. This is because during acceleration, high-temperature exhaust gas is discharged during operation, and by taking this into account and closing the bypass valve 15, the high-temperature exhaust gas is guided to the filter 3 with a good response.

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.

At this time, in S11, a timer value TimerC that measures the elapsed time from the time of acceleration determination is cleared, and after acceleration, this timer value TimerC is incremented in S12, and in S13, timer values TimerC and TimeD (exhaust bypass is cleared after acceleration) are cleared. A comparison is made between the following periods:

[0043] Here, the timer value TimerC is
If it is determined that the temperature is D or higher, the process proceeds to S14 and the exhaust temperature T
Check whether ex is higher than filter internal temperature Tcnt, and if Tex≧Tcnt, bypass valve 1 is activated in S17.
Close 5. In this case, since the filter temperature can be further increased, regeneration is ensured by actively guiding high temperature exhaust gas to the filter 3.

On the other hand, if Tex<Tcnt, S2
0, the bypass valve 15 is opened. This is because when the load fluctuates even during regeneration of the filter 3, the exhaust temperature Tex also changes moment by moment, whereas the filter internal temperature Tcnt does not change rapidly because the filter 3 has a certain amount of heat capacity. Therefore, there is an operating condition in which the exhaust gas temperature Tex becomes lower than the filter internal temperature Tcnt due to a slight load reduction within the B region. In this case, if a large amount of exhaust gas with a temperature lower than its internal temperature is allowed to flow through the filter 3, the filter 3 will be cooled down, so in order to prevent this, the exhaust gas is passed through the filter 3 in a bypass manner to keep the filter 3 warm.

(iii) C area

This case is almost the same as the case in region B; the difference is that in addition to the exhaust throttle and heater operation, an intake throttle is added in S26 to raise the temperature above the SOF reaction temperature. The only point is that there is.

However, when Tex<Tcnt, the bypass valve 15 is opened, and accordingly, the intake throttle valve 6 is opened in S18 to stop the intake throttle. this is,
If the intake air is throttled, the composition of the exhaust gas will deteriorate due to unstable combustion, so this is to prevent such exhaust gas from being directly discharged from the bypass passage 14.

4. Judgment of end of playback

At S29, the timer value TimerA is incremented. In this case, the timer value TimerA represents the time since the playback operation was started.

In S30, this timer value TimerA is compared with a predetermined value TimeB, and if TimerA≧TimeB, it is determined that the regeneration of the filter 3 has been completed, the timer value TimerA is cleared in S31, and the end of regeneration is set in S32. do. In other words, until the end of playback is set in S32, it is determined that it is time to play, so the above playback operation continues. When the reproduction end is set, it is assumed that the reproduction time has come and the process proceeds from S2 to S33 and thereafter.

5. Post-processing

[0052] In S33 to S38, post-processing is performed and the particulates are returned to a state where they can be collected by the filter 3 (in S33 to S36, the operation of all temperature raising devices is stopped and the entire amount of exhaust gas is guided to the filter 3, In S37 and S38, the reproduction end is reset and the timer value TimerA is cleared).

This concludes the explanation of the filter regeneration operation. In correspondence with FIG. 1, S2 is the reproduction timing determination means 41, S
3 or S9 is the area determination means 40, S15, S16, S
18, S19 or S26, S27, S18, S19 is the reproduction start means 42, S10 or S21 is the acceleration determining means 43, S11, S12 or S22, S23 is the elapsed time measuring means 44, 13 or S24 is the elapsed time determining means 4
5, S14 or S25 is the temperature determination means 48, S17,
S20 or S20 and S28 fulfill the respective functions of the actuating means 49.

The operation of this example will now be explained.

[0055] When it is determined that the regeneration time has come and the operating conditions are in regions B and C, the temperature raising device is activated and regeneration of the filter 3 is started.

[0056] During acceleration during operation of the temperature raising device, the bypass valve 15 is closed regardless of the exhaust gas temperature Tex. During acceleration, which requires a large engine output, it is expected that high-temperature exhaust gas higher than Tcnt will be exhausted. Therefore, by closing the bypass valve 15 from the acceleration stage, the high-temperature exhaust gas will flow to the filter 3 without leaking. be guided. Temperature sensor 22
If the bypass valve 15 is closed by feeding back the actual exhaust gas temperature Tex detected in , it is inevitable that a delay will occur during a transient period such as during acceleration, so this problem is to be improved.

[0057] The elapsed time after acceleration TimerC is Time
During steady operation exceeding D, the exhaust gas temperature Tex upstream of the branch point of the bypass passage 14 and the internal temperature Tcnt of the filter 3 are compared, and the exhaust gas temperature Tex is equal to the filter internal temperature Tcnt.
If the temperature is higher than that, 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.

On the other hand, when the exhaust gas temperature Tex becomes lower than the filter internal temperature Tcnt, the bypass valve 15 is opened and the filter 3 is prevented from being cooled by the low-temperature exhaust gas. The generated regeneration reaction is inhibited by a subsequent change in load conditions (for example, if the amount of heat removed from the filter 3 by the exhaust flow accompanying an increase in load becomes greater than the amount of heat generated by the reaction in the filter 3, (The regeneration reaction in the filter 3 would end prematurely.)

In this way, by actively guiding the high-temperature exhaust gas as much as possible to raise the temperature of the filter 3 above its current temperature while preventing the filter 3 from being cooled, the filter 3 that has started regeneration can reach a high temperature that can be regenerated. maintained at temperature, filter 3
regeneration is ensured. As a result, the time required to regenerate the filter 3 can be shortened, and when the regeneration time is shortened, the time for energizing the heater 15 and the time for restricting the intake air and exhaust gas are also shortened, which improves fuel efficiency and drivability during regeneration operation. The deterioration of this can also be kept to a minimum.

On the other hand, in the conventional example, the bypass valve is opened so that the temperature of the filter itself is maintained within the regenerator range, so unless the temperature of the filter itself is within the regenerator range, the exhaust gas on the upstream side of the filter No matter how high the temperature was, it was not guided to the filter.

In addition, in the embodiment, in order to maintain the filter 3 in a high temperature state, even though the exhaust gas is bypassed when Tex<Tcnt in the C region, the intake throttle is stopped and the exhaust gas composition is deteriorated. Therefore, the exhaust gas discharged from the bypass passage 14 has almost no adverse effect on the environment. In this sense, since a large amount of particulates may be discharged to area A (for example, under high load), if the bypass passage 14 is opened,
Particulates are released into the atmosphere, which poses a problem. According to this example, in region A, by closing the bypass valve 15 and guiding the entire amount of exhaust gas to the filter 3, particulates can be released even during regeneration operation. is prevented from being released.

[0062]

[Effects of the Invention] As explained above, the present invention forcibly closes the bypass valve and guides the exhaust gas to the filter for a predetermined period from when an acceleration state is detected in the region where the temperature raising device is activated. The temperature of the filter is increased, and after a predetermined period of time, the exhaust temperature upstream of the bypass passage branch point is compared with the filter temperature. If the exhaust temperature is lower, the exhaust air is released into the bypass passage to prevent the filter from cooling. , it is possible to increase the temperature raising effect of the filter, shorten the regeneration time, and suppress deterioration of engine fuel efficiency.

[Brief explanation of drawings]

FIG. 1 is a claim correspondence diagram of each invention.

FIG. 2 is a system diagram of one embodiment.

FIG. 3 is a flow chart for explaining the control operation of this embodiment.

FIG. 4 is a flow chart for explaining the control operation of this embodiment.

FIG. 5 is a flow chart for explaining the control operation of this embodiment.

FIG. 6 is an operating range diagram of this embodiment.

[Explanation of symbols]

1 Engine 2 Exhaust passage 3 Filter 5 Intake passage 6 Intake throttle valve 8 Diaphragm actuator 9 Three-way solenoid valve 11 Exhaust throttle valve 12 Diaphragm actuator 13 Three-way solenoid valve 14 Bypass passage 15 Bypass valve 16 Diaphragm actuator 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) 2
6 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 Region division means 38 Engine load sensor 39 Engine speed sensor 40 Region determination means 41 Regeneration time determination means 42 Regeneration Starting means 43 Acceleration determining means 44 Elapsed time measuring means 45 Elapsed time determining means 46 Exhaust temperature sensor 47 Filter temperature sensor 48 Temperature determining means 49 Operating means

Claims (1)

[Claims] 1. A filter interposed in an exhaust passage to collect particulates in the exhaust gas, a device for raising the temperature of this filter, a passage that bypasses this filter, a bypass valve that opens and closes this passage, and A bypass valve driving device and at least two other operating ranges, one for the self-regeneration of the filter and the other, depending on the exhaust temperature.
a sensor for detecting the load and rotation speed of the engine, a means for determining whether the operating conditions determined from these detected values are in a region other than the self-renewable region; means for determining whether or not it is time for regeneration; and based on these determination results, when it is time for regeneration and operating conditions are in a range other than the self-renewable range, the temperature raising device is operated to regenerate the filter. means for starting the engine; means for determining from the detected value of the engine load whether or not acceleration is occurring; means for measuring the elapsed time from the time of acceleration determination; and whether or not the measured elapsed time reaches a predetermined time. a sensor for detecting the exhaust temperature upstream of the branch point of the bypass passage; a sensor for detecting the temperature of the filter; and determining whether the exhaust temperature is higher or lower than the filter temperature based on these detected values. means for closing the bypass valve while the heating device is in operation while the elapsed time from the time of acceleration determination does not exceed a predetermined time; If the exhaust gas temperature is higher than the filter temperature, the bypass valve is closed while the temperature raising device is in operation, and conversely, if the exhaust gas temperature is lower than the filter temperature, the temperature raising device is closed. An exhaust gas purification device for an engine, comprising means for operating each of the bypass valve driving devices so that the bypass valve is opened during operation of the device.