JPH03233126A - Exhaust gas purifier of engine - Google Patents

Abstract

PURPOSE:To judge an appropriate regeneration timing regardless of engine performance deterioration and so forth, by obtaining an integrated amount of accumulated particulates, based on an output from an air-fuel ratio sensor. CONSTITUTION:Particulates discharge amount DELTAMp per unit time DELTAt is obtained, according to an output VA/F of an exhaust gas air-fuel ratio sensor 56 and to engine speed Ne at that time, by an accumulated amount calculating means 57. The discharge amount DELTAMp provides particulates discharge amount suited to the engine condition of performance degradation with good accuracy. The accumulating amount DELTAMp is integrated by a means 58 every unit time, a judgement means 59 judges whether it is at a regeneration timing or not based on the integrated value Mp, and a control means 60 controls a temperature raising device 54 so that a trap 53 may be regenerated at regeneration timing. As a result, regeneration is not carried out neither at too early timing nor too late timing even if performance degradation occurs on an engine itself or its fuel injection system.

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 the exhaust passage, the exhaust pressure may become excessive due to the accumulation of particulates. rose to
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 Laid-Open No. 58
(Refer to Publication No. 51235, SAE Paper 850015) To explain this with reference to FIG. 8, particulates discharged from the engine 1 are collected by a trap 3 having a heat-resistant filter structure interposed in the exhaust passage 2.

On the other hand, a butterfly-type throttle valve 6 is provided in the suction passage 5 to throttle the intake flow rate, and this throttle valve 6 has one end fixed to the valve shaft of the throttle valve 6 and the other end rotatably attached to a rod 8d. The diaphragm 7 and the cutuator 8 are connected via the attached 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 opening time ratio) of the duty signal is increased to strengthen the negative pressure in the pressure chamber 8b, the diaphragm 8a moves the rod 8d to the right in the figure against the return spring 8C. Therefore, 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 11.
, signals from the intake pressure sensor 14 and the like provided in the intake 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 intake pressure sensor 14 to improve control accuracy. Feedback control is performed so that the intake negative pressure downstream of the valve 6 is approximately constant.

In this way, when the amount of air introduced into the engine 1 is reduced, the exhaust temperature increases, so the particulates collected in the trap 3 are re-burned by the heat of the raised exhaust gas, and the trap 3 is regenerated. Ru.

(Problem to be Solved by the Invention) By the way, with such a device, the regeneration timing is determined based on the mileage and time, so even if the mileage and time are the same, if the trip was in a city area or in a suburb with many accelerations and decelerations. The amount of particulates collected in the trap will vary greatly depending on the operating conditions of the engine, such as whether the engine was driven regularly or on a highway.

For this reason, if the regeneration time is too early, fuel efficiency will deteriorate, or conversely, if the regeneration time is too late, particulate collection 1 will exceed its limit, and when regeneration is performed, the particulates will suddenly burn and the trap will melt. do.

Furthermore, if the performance of the engine itself or the fuel injection system deteriorates over time, the amount of particulates discharged from the engine will vary, which will disrupt the judgment of when to regenerate.

On the other hand, some devices detect the differential pressure across the trap and determine that it is time for regeneration when the detected pressure value exceeds a predetermined value. This method has problems with sensor reliability (heat resistance, etc.), and when the trap carrier absorbs moisture, this results in measurement errors.

This invention was made in view of these conventional problems, and focused on the fact that there is a correlation between the amount of particulate emissions from the engine and the air-fuel ratio, and it is possible to capture particulates based on the air-fuel ratio sensor output. It is an object of the present invention to provide a device that maintains good regeneration timing determination accuracy even if there is deterioration in engine performance by calculating the integrated value of the collected amount.

(Means for Solving the Problems) As shown in FIG. 1, the present invention includes a trap 53 that collects particulates in exhaust gas and re-burns the collected particulates when the temperature reaches a regeneration temperature or higher; 53, a sensor 56 that detects the exhaust air-fuel ratio, and an output of this air-fuel ratio sensor ■Amount of particulates collected per unit time ΔMP according to A/F.
means 57 for calculating the collected amount ΔMP, means 58 for integrating the collected amount ΔMP for each unit time, means 59 for determining whether or not it is time for regeneration based on this integrated value MP; The temperature increasing device 5
Means 60 for controlling 4 is provided.

(Function) When one particulate emission per unit time is determined according to the air-fuel ratio sensor output V A/F at that time, this mp calculates the particulate emission amount according to the engine condition that caused the performance deterioration. Give well.

As a result, even if performance deterioration occurs in the engine itself or the fuel injection system, the regeneration timing will not be too early or too late.

(Embodiment) FIG. 2 is a system diagram of an embodiment of the present invention. In the figure, 6 is a normally open butterfly type throttle valve provided in the intake passage 5, and a diamond 7 ram actuator 8 is connected to this intake throttle valve 6.

A three-way solenoid valve 19 is interposed in a passage that communicates the pressure chamber of the actuator 8 with a negative pressure source (for example, a negative pressure pump), and when this solenoid valve 19 is turned on from OFF, a large A constant negative pressure is introduced instead of atmospheric pressure, and the intake throttle valve 6 is closed to a constant angle. The actuator 8 and the solenoid valve 19 constitute an intake throttle valve driving device.

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

An 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 provided close to the upstream side of the trap 3, and heats the trap 3 upon receiving an energization signal from the control unit 41.

The intake throttle valve 6 and its driving device provided in this way, the exhaust throttle valve 21 and its driving device, the bypass valve 25 and its driving device, and the heater 29 and its energizing device are the temperature raising device 5 of FIG.
4.

31 is an air-fuel ratio sensor that outputs V according to the air-fuel ratio in the exhaust gas.
Turn on A/F. A temperature sensor 32 includes a thermocouple and detects the exhaust gas temperature TEX. 34 is the rotation speed N of engine 1
A sensor (crank angle sensor) 35 detects the accelerator lever opening (engine load) Q, which is composed of a potentiometer, and a sensor 36 detects the cooling water temperature T-.

Signals from these sensors are input to a control unit 41 consisting of a microcomputer, and the control unit 41 turns on three three-way solenoid valves 19, 23, and 27 according to the steps shown in Figures 3 and 4.
, an OFF signal, and an energization signal to the heater 29, respectively.

FIG. 3 shows a routine for determining the reproduction time.

In Sl and S2, the engine speed Ne and the air-fuel ratio sensor output V A/F are read.

In S3, 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 S4. The integration time comes at a constant time interval Δt (unit time).

S4 and 85 are parts that perform the function of the collection amount calculation means 57 in FIG. First, in S4, the unit time Δ from the engine is expressed as the particulate emission amount mp [g/b
] is found by map search. The map characteristics of this 01P are shown in FIG. As shown in Figure 5, the same rotational speed N
If e, mp increases as the air-fuel ratio A/F becomes richer, and nap increases as the rotational speed Ne increases if the air-fuel ratio A/F is the same. On the other hand, air-fuel ratio sensor output V
Since A/F has the characteristics shown in Fig. 6 with respect to the air-fuel ratio A/F, the horizontal axis in Fig. 5 is converted from the air-fuel ratio A/F to the air-fuel ratio sensor output ■A/F to obtain the characteristics of mp. If we redraw it, we get the characteristics shown in Figure 7. The map shown in FIG. 7 is stored in the ROM.

In Figure 7, the reason why the air-fuel ratio sensor output V A/F is used as a parameter instead of the engine load Q is to avoid being affected by performance deterioration that occurs in the fuel injection system such as the fuel injection pump and injection nozzle, or the engine itself. This is to do so. For example, when an injection nozzle becomes clogged over time, the air-fuel ratio shifts to the lean side due to a decrease in the amount of fuel injected, resulting in a decrease in the amount of particulate emissions from the engine.

In other words, if Imp is determined according to the engine load Q, this amount of decrease will occur as an error.

On the other hand, if the air-fuel ratio sensor output V A/F is used, no matter whether the air-fuel ratio shifts to lean or rich due to performance deterioration, the engine will respond to the shifted air-fuel ratio. Since the amount of particulate emissions is determined, there is no need for errors.

In S5, the particulate collection amount ΔMP per unit time is determined using the following equation.

ΔMp=wap×η...Φ where l is the collection coefficient of the trap (a constant value specific to the trap, for example 0.7 to 0.8).

S6, together with S3, functions as the collection amount integrating means 58 shown in FIG. 1, and here, ΔMP is integrated using the following equation.

MP4-MP+ΔMP...■ In other words, ΔMP is added to MP every unit time Δt according to formula (2). As a result, MP represents the amount of particulates deposited in the trap.

S7 is S8, which will be described later. This part, together with S22, functions as the regeneration timing determination means 59 in FIG.
By comparing P with a predetermined reference value (for example, 10g), if MP≧reference value, it is determined that it is time for regeneration, and S8
Proceed to. In S8, the reproduction time 7 lag F is set (F=1). In other words, F=1 means that it is in the regeneration period.

If MP<the reference value in S7, it is determined that there is not enough accumulation to require regeneration, and the process proceeds to S9. In S9,
The exhaust and intake throttle valves 21 and 6, the bypass valve 25, and the heater 29 are kept inactive.

FIG. 4 shows a routine for performing a playback operation.

In S21, read the exhaust temperature TEX and cooling water temperature Tw,
If F=1 in S22, it is determined that the regeneration time has come, and 3.
23 to S27, where instructions are given to the three-way solenoid valves 19, 23, 27 and the heater 29 so that the trap 3 is regenerated. That is, S23 to S27 are the parts that perform the function of the control means 60 in FIG.

In S23, it is checked whether the exhaust gas temperature TEX is equal to or higher than a predetermined value T+ (400° C., which is equal to the regeneration temperature), and if TEX≧T1, the trap 3 is regenerated without doing anything, so the process proceeds to 325.

Conversely, if "rEx<Tl", the process proceeds to S24, and it is checked whether the cooling water temperature Tw is equal to or higher than the predetermined value T2 (for example, 50° C.), and if so, the process proceeds to S26.

In S26, both exhaust and intake are throttled 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 Tw is lower than the predetermined value T2 in S24, the process proceeds to S27, where both throttle valves 21, 6 and bypass valve 25 are all opened.

The reason why both throttle 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 misfires, resulting in poor drivability, and misfires also increase particulates. Moreover, the reason why the bypass valve 25 is opened is to prevent the trap 3 from being too cooled by cold exhaust gas.

At 828, the playback time is counted, and the process advances to S29. S2
9, the counted playback time is set to a predetermined time (for example, 1
0 minutes), and if a predetermined period of time has elapsed, it is determined that the reproduction has ended and the process proceeds to S30.

In S30, the data used for determining the playback timing is erased.

Uni will explain the effect of this example.

Even if the distance and time traveled are the same, if the driving conditions of the vehicle differ during that time, the amount of particulates emitted from the engine will vary greatly.

Therefore, if the amount of particulate emissions per unit time from the engine is calculated according to the engine load Q and the rotational speed Ne, and the regeneration timing is determined from the integrated value, it is possible to regenerate as long as there are no variations in the engine. The timing will be determined in accordance with the usage conditions of the engine.

However, even if the particulate emission amount per unit time is set according to the operating conditions in this way, if performance deterioration occurs in the fuel injection system or the engine itself thereafter, a deviation from the set value will occur.

In other words, even if the playback time is initially determined with high accuracy,
As performance deteriorates, the regeneration timing becomes too early or too late.

On the other hand, in this example, if the particulate emission amount lap per unit time Δt is determined according to the air-fuel ratio sensor output V A/F and the rotational speed Ne at that time, this IIIP is the engine whose performance has deteriorated. To give accurate particulate emission amount according to the condition. As shown in Figure 5, performance deterioration that occurs in the fuel injection system and the ennon itself will eventually shift the air-fuel ratio to the rich or lean side, so as long as the air-fuel ratio is detected, the performance will deteriorate. This is because it is factored into the air-fuel ratio.

As a result, even if performance deterioration occurs in the engine itself or the fuel injection system, the regeneration timing can be appropriately determined, so that the regeneration timing will not be too early and cause fuel consumption to deteriorate.

Furthermore, it is also possible to prevent the trap from being melted and damaged due to sudden combustion of particulates when the regeneration is performed due to too late regeneration and the amount of particulates accumulated exceeds the limit.

Finally, the temperature raising device for the trap 3 is not limited to the one in the embodiment, and any device that can raise the trap temperature may be used, such as one equipped with only an intake throttle, an exhaust throttle, or only a heater. do not have.

(Effects of the Invention) This invention determines the amount of particulates collected per unit time from the air-fuel ratio sensor output, and determines the regeneration timing from the integrated value, which causes performance deterioration in the engine itself and the fuel injection system. However, it is possible to maintain an appropriate regeneration timing even when the trap is heated, thereby improving fuel efficiency and preventing trap erosion.

[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, Figs. 3 and 4 are flowcharts for explaining the control operation of this embodiment, and Fig. 5 is a diagram for explaining the air-fuel ratio. A characteristic diagram of particulate emissions, FIG. 6 is an output characteristic diagram of the air-fuel ratio sensor of the above embodiment, and FIG. 7 is a characteristic diagram of the mp of this embodiment.
FIG. 8 is a system diagram of a conventional example. 2... Exhaust passage, 5... Intake passage, 6... Intake throttle valve, 8... Diaphragm actuator, 11...
・Fuel injection pump, 19... Three-way solenoid valve, 21...
Exhaust throttle valve, 22...Diamond 7"7 actuator, 23...Three-way solenoid valve, 24...Bypass passage, 2
5... Bypass valve, 26... Diaphragm actuator, 27... Three-way solenoid valve, 29... Heater, 3
1... Air-fuel ratio sensor, 32... Exhaust temperature sensor, 3
4...Crank angle sensor (Ennon rotation speed sensor),
35... Accelerator lever opening sensor (ennon load sensor), 41... Control unit, 53...
Trap, 54... Temperature raising device, 56... Air-fuel ratio sensor, 57... Collection amount calculation means, 58... Integration means,
5...Regeneration time determination means, 60...Control means. Figure 8

Claims (1)

[Claims] A trap that collects particulates in the exhaust and re-burns the collected particulates when the temperature exceeds the regeneration temperature, a device that raises the temperature of this trap, a sensor that detects the exhaust air-fuel ratio, and an output from this air-fuel ratio sensor. means for calculating the amount of particulates collected per unit time accordingly, means for integrating this collected amount for each unit time, and means for determining whether it is time for regeneration based on this integrated value;
An exhaust gas purification device for an engine, comprising means for controlling the temperature raising device so that the trap is regenerated when a regeneration time comes.