JPH03229909A - Exhaust cleaner for engine - Google Patents

Abstract

PURPOSE:To conduct properly the rejuvenation of a trap even at a high land at the trap catching and collecting particulates during exhaust, by correcting respectively according to atmospheric pressure the detected value of its front and rear pressure difference or the set value of the front and rear pressure difference at the time of catching and collection limitation. CONSTITUTION:The rejuvenation time of a trap 53 catching and collecting particulates during exhaust is decided by means of a means 57 by comparing a trap front and rear pressure difference detected by means of a sensor 56 with a trap front and rear pressure difference at the time of catching and collection limitation set by means of a means 55. As a result, when it is decided that it is a rejuvenation time, a device 54 which makes the temperature of the trap 53 rise, is controlled by means of a means 58, and particulates caught and collected by the trap 53 is burned again. At the above device, atomospheric pressure is detected by means of a sensor 59. And the detected value of the trap front and rear pressure difference and the set value of the trap front and rear pressure difference are respectively corrected by means of respective means 60, 61 so that the detected value may become smaller or the set value may become larger as the detected value of atmospheric pressure keeps dropping.

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 Application Laid-Open No. 58-1989-1).
(See Publication No. 51235).

To explain this with reference to FIG. 7, 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, the intake passage 5 is provided with a pattern-type throttle valve 6 that controls the intake air flow rate, and the throttle valve 6 has one end fixed to the valve shaft of the throttle valve 6 and the other end rotated by a rod 8d. A diaphragm actuator 8 is connected via a freely 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 accordance with a duty signal from the control device 15. 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 diaphragm 8a moves the rod 8d to the right in the figure against the return spring 8c. Therefore, the crest 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 for trap 3 to regenerate based on the predetermined travel distance, travel time, etc., the operating conditions determined from 3- engine load and rotation speed at that time are such that a large amount of surplus air flows into engine 1. Determine whether it is in operation. When it is determined that this operating state is in effect, a duty signal is output so that the opening valve 6 is closed to a predetermined angle, and a throttle valve 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) However, in such a device, the regeneration timing is determined based on a certain distance traveled and travel time, so even if the distance traveled and travel time are the same, the air flow is lower in highlands than in lowlands. Since the density becomes thinner, smoke increases due to a rise in exhaust gas temperature due to deterioration of combustion, and the amount of particulates deposited in the trap also increases accordingly.

For this reason, it is conceivable that the regeneration timing is too late and the amount of particulates deposited exceeds the limit, and when regeneration is performed, the particulates are rapidly burned and the trap is eroded.

On the other hand, there are devices that detect the back pressure of the trap or the differential pressure across the trap, and determine that it is time to regenerate when the detected value reaches a predetermined value. In this case, even if the amount of particulates deposited in the trap is constant, at high altitudes, the differential pressure ΔP across the trap increases to ΔP as shown in Figure 8 due to the drop in atmospheric pressure, so the regeneration period is delayed. As a result, the problem of the reproduction timing being too late as described above does not occur.

However, with this method, the regeneration time may be too early depending on the height above sea level.

In other words, even if the amount of particulate deposits in the trap is constant, the differential pressure across the trap Δ
Since P increases, it is determined that it is time for regeneration at high altitudes, even though it is not yet time for regeneration at low altitudes, resulting in poor fuel efficiency.

This invention was made with attention to such conventional problems, and is a device that improves the accuracy of determining the regeneration time by correcting the atmospheric pressure in a device that determines the regeneration time from the differential pressure before and after the trap. The purpose is to provide

(Measures for solving problem W1, > As shown in FIG. 1, this invention includes a trap 53 that collects particulates in the exhaust gas and re-burns the collected particulates when the temperature exceeds the regeneration temperature. , a device 54 for raising the temperature of this trap 53, a means 55 for setting the differential pressure across the trap ΔPIIla at the collection limit, a sensor 56 for detecting the actual differential pressure across the trap ΔP, and a device 54 for setting the differential pressure across the trap ΔP means 57 for determining whether or not the regeneration period is reached by comparing the detected value of and the set value of the differential pressure across the trap ΔP'+a at the trapping limit, and the trap 53 is regenerated at the regeneration period. In an engine exhaust purification device comprising a means 58 for controlling the temperature raising device 54, a sensor 59 detects atmospheric pressure Pa.
Based on the detected value of the atmospheric pressure Pa, the detected value of the differential pressure ΔP across the trap becomes smaller as the atmospheric pressure decreases, or the differential pressure ΔPlI across the trap at the collection limit is set.
Means 60 and 61 are provided for correcting the detected value of the differential pressure across the trap ΔP or the set value of the differential pressure across the trap ΔPn+ax at the collection limit so that the set value of la becomes larger.

(Function) When the detected value of ΔP is made smaller as the atmospheric pressure decreases in the atmospheric pressure correction value Kpa, for example, the increase in ΔP accompanying the decrease in atmospheric pressure is offset by Kpa.

As a result, the differential pressure across the trap after correction is the same at high altitudes as at low altitudes.

(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 provided in the intake passage 5, and a diaphragm actuator 8 is connected to the intake throttle valve 6.

A three-way electromagnetic 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 electromagnetic valve 19 is turned on from OFF, the pressure chamber of the actuator 8 is 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 diaphragm 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, 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 thus provided constitute a temperature raising device 54 in FIG.

31 is a semiconductor pressure sensor, which detects the differential pressure Δ across the trap 3.
Detect P. A temperature sensor 32 includes a thermocouple and detects the exhaust gas temperature TEX. 34 is the rotation speed N of engine 1
35 is a potentiometer that detects the accelerator lever opening (engine load) Q; 36 is a sensor that detects the cooling water temperature Tar; 37 is a sensor that detects the atmospheric pressure Pa. It is a sensor.

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. 3 is a routine for regenerating the trap.

In Sl, engine speed Ne and engine load Q.

Read cooling water temperature Tor=exhaust temperature TEXt atmospheric pressure Pa and differential pressure ΔP across the trap.

S2 is S8, which will be described later. This part, together with S9 and 818, functions as the reproduction timing determining means 57 in FIG. In S2, it is checked whether it is the playback time or not, and if it is determined that it is not the playback time, the process advances to S3. In this case, the reproduction time is determined based on the value of 7 lag F, and if it is not the reproduction time, F=0.

S3 to S6 are portions that perform the function of the detected value correction means 60 shown in FIG.

In S4, an atmospheric pressure correction value Kpa of ΔP is obtained by map search from the atmospheric pressure Pa stored in the memory in S3.

In S6, atmospheric pressure correction is performed on ΔP stored in S5 using the following equation.

ΔP←ΔP X K pa...■ A map of the above Kpa is shown in FIG. From the same figure, Kpa
is given a smaller value as the atmospheric pressure Pa decreases. Note that the atmospheric pressure at low altitudes is 7601 Hg.

S7 is a part that performs the function of the trapping limit time differential pressure setting means 55 shown in FIG.
Find P may by map search. The map characteristics of ΔP max are shown in FIG. Since the value of 8Pmay is varied according to the load Q and the rotational speed Ne, ΔPma is determined according to the operating conditions.

S8 is a part that performs the function of the reproduction time determination means 57 in Figure #1, and here, by comparing ΔP and 8P may, Δ
If P≧ΔP may, it is determined that it is time for regeneration, and S9
Proceed to.

In S9, the reproduction time 7 lag F is set (F=1).

In other words, F=1 means that it is in the regeneration period.

If ΔP<ΔPmax in S8, the process advances to S10.

At 810, the temperature raising device is kept inactive, that is, the exhaust and intake throttle valves 21 and 6, the bypass valve 25, and the heater 29 are kept inactive.

On the other hand, if F=1 in S2, it is determined that the regeneration time has come, and the process proceeds to 811 to S15, where the three-way solenoid valves 19, 23°27 and the heater 29 are activated so that the trap 3 is regenerated.
give instructions. That is, 811 to 815 are parts that perform the function of the control means 58 in FIG.

At 811, 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 813.

Conversely, if TEx<T1, the process proceeds to S12, where 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 S14.

At 814, 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 T11+ is lower than the predetermined value in S12, the process proceeds to S15, where both nine valves 21 and 6 and the 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 trap regeneration cannot be performed. This is because at low water temperatures when combustion is not stable, the engine will misfire, resulting in poor drivability, and the misfire will also increase particulates. Moreover, the reason why the bypass valve is opened is to prevent the trap 3 from being excessively cooled by cold exhaust gas.

In 316, the playback time is counted, and the process advances to S17. S1
7, 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 S18.

At 818, lower the playback period 7 lag F (F=0)
At the same time, the data used to determine the playback time will be deleted.

Here, the operation of this example will be explained.

At high altitudes where atmospheric pressure decreases, the differential pressure across the trap will be larger than at low altitudes, even if only the same amount of particulates is deposited as at low altitudes. In other words, an increase in the differential pressure across the trap due to a decrease in atmospheric pressure occurs as a detection error in the differential pressure across the trap.

On the other hand, in this example, an atmospheric pressure correction value Kpa is introduced, and if the detected value of ΔP is made smaller as the atmospheric pressure decreases using this Kpa, the increase in ΔP due to the decrease in atmospheric pressure will be reduced. This will be offset by Kpa.

As a result, the differential pressure across the trap after correction (ΔP×Kpa)
As shown in Figure 6, is the same in highlands as in lowlands, and Δ
Since the P detection error is eliminated, it is possible to prevent fuel consumption from worsening due to too early regeneration timing.

In the embodiment, the detected value of ΔP is corrected, but
Alternatively, ΔP max can also be corrected. Δ
This is because the detected value of P increases as the atmospheric pressure decreases, so by increasing ΔPma accordingly, the relative magnitude relationship can be kept constant.

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 corrects atmospheric pressure for the detected value of the differential pressure across the trap or the set value of the differential pressure across the trap at the collection limit.
Even at high altitudes, the timing of regeneration is appropriate and fuel efficiency can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of this invention, Fig. 2 is a system diagram of one embodiment, Fig. 3 is a flowchart for explaining the control operation of this embodiment, and Figs. 4 and 5 are respective diagrams of this embodiment. FIG. 6 is a characteristic diagram of ΔP for explaining the operation of this embodiment, FIG. 7 is a system diagram of a conventional example, and FIG. 8 is a pressure characteristic diagram. 2...Exhaust passage, 5...Intake passage, 6...Intake throttle valve, 8...Diamond 7 ram actuator, 19...
・Three-way solenoid valve, 21... Exhaust throttle valve, 22... Diaphragm 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...
- Exhaust temperature sensor, 34... Crank angle sensor (engine speed sensor), 35... Accelerator lever opening sensor (engine load sensor), 37... Atmospheric pressure sensor, 41... Control unit, 53... Trap, 54... Temperature raising device, 55... Collection limit time differential pressure setting means, 56... Differential pressure sensor, 57... Regeneration timing determining means, 58... - Control means, 59... Atmospheric pressure sensor, 60... Detected value correction means, 61... Set value correction means.

Claims (1)

[Claims] a trap that collects particulates in exhaust gas and re-burns the collected particulates when the temperature reaches a regeneration temperature or higher; a device that raises the temperature of this trap; and means for setting a differential pressure across the trap at the collection limit; a sensor for detecting the actual differential pressure across the trap; a means for determining whether or not it is time for regeneration by comparing the detected value of the differential pressure across the trap with a set value of the differential pressure across the trap at the time of the collection limit;
The engine exhaust purification device includes a means for controlling the temperature raising device so that the trap is regenerated when the regeneration period comes, and a sensor that detects atmospheric pressure, and a sensor that detects the atmospheric pressure based on the detected value of the atmospheric pressure. The detected value of the differential pressure across the trap or the set value of the differential pressure across the trap at the trap limit is set such that the detected value of the differential pressure across the trap becomes smaller as the pressure decreases, or the set value of the differential pressure across the trap at the trap limit increases. 1. An engine exhaust gas purification device comprising means for correcting a set value of a differential pressure across a trap.