JPH03199614A - Exhaust gas cleaner for engine - Google Patents

Abstract

PURPOSE:To prevent error in judging the time of regeneration due to trap amount hysteresis by calculating unburnt trap amount immediately after regeneration according to the ratio of front to rear pressure differential and limit pressure differential immediately after regeneration. CONSTITUTION:In the case a trap 3 is judged to be regenerated immediately before, a control unit 41 calculates the ratio of detected front rear pressure differential of the trap 3 from a semiconductor type pressure sensor 31 to a limit pressure differential, and calculates unburnt trap amount from the calculated ratio. Assuming the unburnt trap amount as the initial value of the integrated value of the particulate trap amount. Regeneration time is judged by integrating the particulate trap amount calculated according to detected values of a crank angle sensor 34, and an accelerator lever opening sensor 35 from the initial value. This makes it possible, even if particulate trapped with the trap 3 remains unburnt after regeneration, the time of regeneration is accordingly made earlier.

Description

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

(Prior art) In engines (particularly diesel engines) in which particulates such as carbon contained in exhaust gas are collected in a trap provided in a wandering passage, the exhaust pressure increases due to the accumulation of particulates. rise excessively,
In order to reduce engine and emission performance, a device is provided to regenerate the trap by burning the accumulated particulates at a predetermined time (Japanese Patent Application Laid-open No.
-s, see Publication No. 1235).

To explain this with reference to FIG. 8, particulates discharged from the engine 1 are collected by a trap 31 having a heat-resistant filter structure interposed in the wandering passage 2.

On the other hand, the suction passage 5 is provided with a butterfly-type crest valve 6 that throttles the intake and steam flow rate, and this throttle valve 6 has one end fixed to the valve shaft of the crest valve 6 and the other end connected to a rod 8d. A diamond 7 ram actuator 8 is connected via a freely movably mounted lever 7.

This actuator 8 and the pressure chamber 8 of the actuator 8
A throttle valve drive device is constituted by an electromagnetic valve 9 that can change the control negative pressure guided by the control device 15 in response to a duty signal from the control device 15 and the like. For example, when the duty value (valve open time ratio) of the duty signal is increased to strengthen the negative pressure in the pressure chamber 8b, the diamond 7 ram 8B resists the return spring 8c and moves D7 and 8d to the right in the figure. As the throttle valve 6 moves, the throttle valve 6 closes. 10 is a negative pressure pump.

The control device 15 includes a load sensor 12 and a rotation speed sensor 13 of the engine 1, which are respectively provided in the fuel injection pump 1.
, signals from the suction pressure sensor 14 and the like provided in the air passage 5 downstream of the throttle valve 6 are input, and the control device 15 performs the following control.

When it is determined that it is time to regenerate the trap 3 based on the predetermined travel distance, travel time, etc., the operating conditions determined from the engine load and rotation speed at that time are the operating conditions in which a large amount of surplus air flows into the engine 1. Determine whether it is.

When it is determined that this operating state is present, a duty signal is output so that the throttle valve 6 is closed to a predetermined angle, and a duty signal is output based on the signal from the suction pressure sensor 14 to improve control accuracy. The feed pressure is controlled so that the suction negative pressure downstream of the feed valve 6 is approximately constant.

In this way, when the amount of air introduced into the engine 1 is reduced, the wandering temperature increases, so the particulates collected in the trap 3 are re-burned by the heat of the wandering air whose temperature has increased, and the trap 3 is will be played.

(Problem to be Solved by the Invention) In such a device, a predetermined period of time is spent opening during regeneration, and when the time period ends, the trap is considered to have been completely regenerated.

However, even after the regeneration period has passed, some of the collected amount may remain unburned. Further, the amount of unburned remains varies depending on the operating conditions.

For this reason, if the regeneration timing is determined based on the collected amount history, an error will occur due to the amount of unburnt material.
There may be cases where the timing of regeneration is too late. As a result, when the limit of the amount of collected particles is exceeded and regeneration is performed, the particulates are rapidly burned, resulting in the inconvenience of melting and damage of the particles.

This invention was made by focusing on such conventional problems, and by determining the amount of unburned residue r) collected from the ratio of the differential pressure across the trap immediately after regeneration and the critical differential pressure, It is an object of the present invention to provide a device that does not cause errors in regeneration timing tq due to wind history.

(Means for Solving the Problems) As shown in FIG. 1, the present invention provides a trap that collects particulates wandering around and re-burns the collected particulates when the temperature exceeds the regeneration temperature. 53 and
A device 54 that raises the temperature of this trap 53, and sensors 55, 5 that detect the load Q and rotation speed Ne of the ennon, respectively.
(3, and means 57 for calculating the particulate collection amount ΔPCT per unit time according to these detected values,
Means 5 for adjusting this collection amount ΔPCT by $A at every predetermined time
8, a means 59 for determining whether or not it is the regeneration time based on the integrated value SUM, a means 60 for operating the temperature raising device 54 when the regeneration time comes, and a sensor for detecting the differential pressure ΔP across the trap 53. 61, a means 62 for determining whether the state is immediately after regeneration, and a means 62 for determining whether the state is immediately after regeneration, and a detection value of the differential pressure before and after the pressure difference and a limit differential pressure ΔP when it is determined that the state is immediately after regeneration.
Means 63 for calculating the ratio of max, and means 6 for calculating the amount of unburned residue collected immediately after regeneration Z A N according to this ratio
4, and a means 65 for setting the fin collection amount ZAN as the initial value of the integrated value SUM.

(Function) Immediately after regeneration, differential pressure across the trap ΔP and critical differential pressure ΔPωax
The ratio corresponds to the effectiveness of regeneration, and a large ratio means that a large amount of collected material remains unburned immediately after regeneration. Therefore, if the amount of BN collected remains the same as before, the next regeneration period must be set earlier.

In the present invention, the next regeneration time comes early because the burnt residue ')JI#JJffiZAN is used as the initial value of the integrated value SLIM. The larger the amount of collected material that remains unburned, the earlier the regeneration period will be.

(Embodiment) FIG. 2 is a system diagram of an embodiment of the present invention. In the figure, reference numeral 6 denotes a normally open butterfly-type throttle valve 6 provided in the intake passage 5, and a diaphragm actuator 8 is connected to this intake throttle valve 8.

The pressure chamber of this actuator 8 and the negative pressure source (for example, f1
A three-way solenoid valve 19 is interposed in the passage communicating with the pressure pump), and when this solenoid valve 19 is turned from OFF to ON, constant pressure 11 is introduced into the pressure chamber of the actuator 3 instead of atmospheric pressure. and the intake throttle valve 6 is closed to a certain angle.

The actuator 8 and the electromagnetic valve 19 constitute an intake A throttle valve driving device.

Similarly, a normally open butterfly type bypass valve 21 is provided in the wandering passage 2 upstream of the trap 3, and a normally closed butterfly type bypass is provided in the passage 24 that bypasses this throttle valve 21 and the trap 3 from upstream of the exhaust throttle valve 21. A valve 25 is provided respectively.

The exhaust throttle valve driving device includes a diaphragm actuator 22 and a three-way solenoid valve 23 connected to the exhaust throttle valve 21.
A bypass valve driving device is constituted by a seven-diamond ram actuator 26 connected to the bypass valve 25 and a three-way solenoid valve 27.

A heater 29 is installed close to the upstream side of the trap 3, and heats the trap 3 upon receiving an energization signal from the control unit 41.

31 is a semiconductor pressure sensor, which detects the differential pressure Δ across the trap 3.
Detect P. 32 is a temperature sensor consisting of a thermocouple, which detects the inlet temperature TIN of the trap 3. 34 is a sensor (crank angle sensor) that detects the rotation speed Ne of the engine 1
, 35 is composed of a potentiometer and is connected to the accelerator lever.
A sensor 36 detects the opening degree (engine load) Q, and a sensor 36 detects the cooling water temperature Tw.

Signals from these sensors are input to a control unit 41 consisting of a microcomputer, and the control unit 41 performs the following operations as shown in FIG.
ON and OFF signals are output to the three three-way solenoid valves 19, 23, and 27, and an energization signal is output to the heater 29, respectively.

FIG. 4 is a routine for regenerating the trap.

In Sl, engine rotation speed Net engine load Q.

Cooling water temperature Tub,) Wrap inlet temperature T Ipi-) Wrap air differential pressure ΔP and mileage distance from totalizer KM
Load.

S2 is S7, which will be described later. M when playing back Fig. 1 along with S8
This is a portion that performs the function of tQ determining means 59.

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 the 7-lag F1, and if it is not the reproduction time, F1=0.

S3 is S18, which will be described later. Together with S26, it functions as the immediately after reproduction determining means 62 in FIG. 1! It is 1S minute. , S3
Okay, so it's right after playback, but if you look at it, if it's not right after playback, the process goes to S4. Here, too, the value of 7 lag F2 is used to judge whether it is immediately after playback, and if it is not immediately after playback, F2=
It is 0.

In S4, it is checked whether it is the time to integrate the amount of collected particulates, and if it is the time to integrate, the process advances to S5. In this case, the integration time comes at constant time intervals ΔT+ (for example, several seconds).

S5 is a part that performs the function of the trapped amount calculation means 57 in FIG. 1, and here, the trapped particulate amount ΔPCT per ΔT1 (per unit time) is determined by performing a map search.

In S6, ΔPCT is integrated for each unit time using the following equation.

SUM=SUM+ΔPCT...■ In other words, ΔPCT is added to SUM at each integration time, and SUM represents the integrated value of ΔPCT. These 86 and 84 are portions that perform the function of the collection amount accumulating means 58 shown in FIG.

Note that the initial value of SUM is not zero, but is a value set in S25, which will be described later.

The content of the 8 PCT map is shown in FIG. 4. In the low load, low rotation range, the maximum positive value is I), and in the high load, high rotation range, the value is negative. The reason why the map value is negative is that the region where the map value is negative is the self-regeneration region.In this region, the exhaust temperature is high, and part of the collected ticulate is burned. This is because the amount of collected water must be subtracted from the cumulative value of the collected amount.

Note that as the total mileage increases, ΔPCT increases due to dimensional deterioration of the engine, so in order to take this into consideration, it may be possible to correct the mileage by calculating ΔPCT l: in S5 (1° In S7, by comparing the integrated value SUM with a predetermined base value (-constant value), if SUM≧reference value, it is determined that +! regeneration time has come, and the process proceeds to S8.

In S8, the reproduction time 7 lag F1 is set (F1=1). In other words, F1=1 means that there is one reproduction period.

In S9, the exhaust and intake calibration valves 21 and 6, the exhaust valve 25, and the heater 29 are left in a state where nothing is done.

On the other hand, if F1=1 in S2, it is determined that the regeneration time has come, and the process proceeds to Sho to S18, where the three-way solenoid valves 19, 23t27 and the heater 29 are activated so that the trap is regenerated.
give instructions. In other words, SIO-618 is a portion that performs the function of the actuating means 60 in FIG.

The SIO checks whether the trap inlet temperature (exhaust temperature) TIN is equal to or higher than the regeneration temperature T+ (for example, 400°C), and if TIN≧TI, the trap 3 is regenerated without doing anything, so the process proceeds to 312.

Conversely, if T IN < T l, the process proceeds to Sll, and it is checked whether the cooling water temperature Tw is at least a predetermined value (for example, 50° C.), and if so, the process proceeds to S13.

In S13, both air intake and air intake are turned on, and the heater 29 is turned on. Through these operations, the exhaust gas temperature is raised to the regeneration temperature, and the trap 3 is regenerated.

If Sll is lower than the predetermined value of Twy5', the process proceeds to S14, where both the double-barrel valves 21, 6 and the bypass valve 25 are opened.

The reason why both slit valves 21 and 6 open is that when the water temperature is low before warming up, the exhaust temperature is also lower than after warming up, so the trap cannot be regenerated. This is because at low water temperatures where combustion is inherently unstable, the engine will misfire, resulting in poor drivability, and the misfire will also increase particulates. Moreover, the reason why the bypass valve 25 is opened is to prevent the trap 3 from being excessively cooled by cold exhaust gas.

In S15 and 51f3, the playback time is counted, and the process proceeds to S17. In S17, the counted playback time is counted for a predetermined time (
For example, 10 minutes), if a predetermined period of time has elapsed, it is determined that the reproduction has ended and the process proceeds to S18.

In 318, set 7 lag F2 to indicate immediately after playback (F2=1
), and in S19, the data used for determining the playback timing is erased.

When this 7-lag F2 is reached, the process proceeds from S3 to 820 and thereafter.

In S20, it is determined whether the sampling condition of ΔP is met, and if this condition is met, the process proceeds to S21. In this case, the sample conditions are that the load Q and rotational speed Ne of the ennon are each greater than a predetermined value, and the interval from the previous sample exceeds a predetermined value (for example, 20 seconds).

In S21, ΔP is stored in the memory, and further temperature correction is performed using the following equation.

ΔP=ΔP X K vw·=■ In the formula, KTW is the water temperature correction coefficient. This KT
The map of W is shown in Figure 5. This is because when the engine is cold, the exhaust temperature is low and ΔP is small, so when the temperature is low, ΔP is
This is because it is necessary to keep a sharp eye on the image. With this Δ
The measurement accuracy of P is improved.

Note that instead of the cooling water temperature Tw, it may be corrected according to the exhaust temperature ~1° S22 is a part that performs the functions of the ratio calculation means 63 and the amount of unburnt collection calculation means 64 in FIG. , here we calculate the ratio of ΔP and the limit differential pressure ΔP wax, and this ratio ΔP/ΔP
The remaining ember collection fiZAN immediately after regeneration is obtained from max by performing a map search.

FIG. 7 shows the map characteristics of ZAN. Since it is judged that the larger the ratio is, the more unburnt remains, the larger the ratio is, the larger the ZAN value is. The obtained ZAN is stored in memory.

Note that ΔP max is obtained by searching the map shown in FIG. This is because ΔP 1aax differs depending on the operating conditions.

In S23, it is checked whether the number of ZAN data obtained each time the sample condition in 820 is satisfied has reached a predetermined number (for example, 4), and if so, the process advances to S23.

In S23, statistical processing is performed on the data of a predetermined number of ZANs. The statistical processing in this case is a weighted average, and the first data ZAN+ is stored in a memory with the same name using the following formula.

ZANI=ZANl...■ Next, a weighted average value is calculated from the alarm value ZAN+ stored in this memory and the second data ZAN2 using the following formula, and this is stored in the memory with the same name.

ZAN2=(3ZAN I+ZAN2)/4...■ In the same way, the weighted average value of the upstream is determined one by one using the following formula.

ZAN3=(3ZAN2+ZAN3)/4...■ZA
N4=(3ZAN3+ZAN4)/4... ■The value finally stored in the memory ZAN4 is the value to be found.

S25 is a part that functions as the initial value setting means 65 in FIG. 1, and here the value of ZAN4 is stored as the initial value of SUM.

In 326, erase the 7 lag F2 that indicates immediately after playback (F2 = 0
).

Here, the operation of this example will be explained.

In this example, the efficiency of regeneration is determined from the ratio between the differential pressure across the trap ΔP immediately after regeneration and the limit differential pressure ΔP'wa, and the amount of trapped material ZAN that remains unburned immediately after regeneration is calculated according to this regeneration efficiency. And, this burning collection IZAN is 82W-
As the initial value of the value SUM, the time when the next reproduction should be performed is determined.

Therefore, if the particulates remain burned after the regeneration time has elapsed, the regeneration time will come sooner. Moreover, the more the amount left unburned, the earlier the regeneration period will be.

In other words, the regeneration timing is appropriate regardless of the amount of unburned fuel.

As a result, it is possible to prevent a situation in which the regeneration timing is too late and the amount of trapped particles exceeds the limit during the next regeneration, and when regeneration is performed, the particulates are burned at tWIi and the trap is eroded.

In addition, control is easier than in systems where the regeneration timing is determined based on both pressure and operation history.

(Effect of the invention) This invention calculates the amount of unburned residue collected immediately after regeneration according to the ratio between the differential pressure across the trap and the critical pressure difference immediately after regeneration, so that the particulates collected in the trap are Even if the trap remains unburned immediately after regeneration, the regeneration time can be moved forward by that amount, thereby preventing the trap from being eroded.

[Brief explanation of drawings]

Figure PjS1 is a claim correspondence diagram of this invention, Figure tIS2 is a system diagram of one embodiment, Figure 3 is a flowchart for explaining the control operation of this embodiment, and Figures 4 to 7 are respectively diagrams of this embodiment. ΔP CT , K IwwΔPwax Characteristic diagram of ZAN, FIG. 8 is a system diagram of a conventional example. 2...Exhaust passage, 5...Intake passage, 6...@throttle valve, 8...Diamond 7 ram actuator, 19...
・Three-way solenoid valve, 21...Exhaust throttle valve, 22...Diamond 7 ram actuator, 23...Three-way solenoid valve, 24
...Bypass passage, 25...Bypass valve, 26...
- Diaphragm actuator, 27... Three-way solenoid valve, 29... Heater, 31... Pressure sensor, 32...
- Trap inlet temperature sensor, 34... Crank angle sensor (Ennon rotation speed sensor), 35... Accelerator lever opening sensor (Ennon load sensor), 41... Control unit, 53... Trap, 54 ... Temperature raising device, 55 ... Engine load sensor, 56 ... Engine rotation speed sensor, 57 ... Collection amount calculation means, 58
. . . Collection amount integrating means, 59 . . . Regeneration time determining means,
60... Operating means, 61... Differential pressure sensor, 62...
Immediately after regeneration determination means, 63... Ratio calculation means, 6°4... Unburnt #II collection measurement calculation means 5... Initial value setting means.

Claims (1)

[Claims] A trap that collects particulates in the exhaust while re-burning the collected particulates when the temperature exceeds the regeneration temperature, a device that raises the temperature of this trap, and sensors that respectively detect the load and rotation speed of the engine. Means for calculating the amount of particulates collected per unit time according to these detected values, means for integrating this collected amount at predetermined time intervals, and means for determining whether it is time for regeneration based on this integrated value. and a means for activating the temperature raising device at this regeneration time, a sensor for detecting a differential pressure across the trap, a means for determining whether the trap is immediately after regeneration, and a means for determining that the trap is immediately after regeneration. means for calculating the ratio between the detected value of the differential pressure across the front and rear and the limit differential pressure; means for calculating the amount of unburned residue collected immediately after regeneration according to this ratio; 1. An engine exhaust purification device characterized by comprising: means for setting as an initial value.