JPH0763043A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To realize the saving of power and the shortening of a span of regenerating time by installing a control means for commanding the operation of an air charging means and the current-carrying to an electric heating means and also a cooling suspension means suspending any cooling operation in time of specified occasion, respectively. CONSTITUTION:An exhaust pressure detecting pressure sensor 7, a temperature sensor 6, a heater 11, a filter 2 and a filter downstream pressure detecting pressure sensor 17 are all set up in a filter storage case 1 in due order from the upstream to the downstream. A motor M for the heater 11 and a blower 13 is driven and controlled by a controller 8 which performs the operation of an air charging means as cooling operation along with a start of regeneration, and subsequently, commands the operation of this air charging means and current-carrying to the electric heating means as heating operation. In addition, this controller 8 is provided with a cooling suspension means which suspends any cooling operation in the case where an estimated filter temperature in time of regeneration starting is less than the specified level. Thus, the saving of power and the shortening of a span of regeneration time are realizable in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for collecting and regenerating particulate matter (particulates) contained in the exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 4-66717 energizes a heater (electric heating means) disposed in the vicinity of a filter in order to burn the particulates collected in the filter to regenerate the filter. Then, the filter and the particulates are heated to burn the particulates.

[0003]

However, immediately after the engine is stopped, the filter is heated to 300 ° C. or higher by the exhaust gas, while it is below freezing after the engine has been stopped for a long time in winter. When the heaters of various temperatures are energized with a uniform electric power, the maximum temperature of the filter varies, and as a result, there is a possibility that the filter may be damaged or defective regeneration may occur.

In view of these circumstances, the inventors of the present invention only supply air to the filter in a state where the power supply to the heater is cut off in advance, thereby cooling the filter to a constant temperature range (called cooling), and then heating the heater. It was considered to energize, to ignite particulates, and to burn. However, such uniform cooling is a waste of electric power when the temperature of the filter is sufficiently low, and the regeneration time is extended.

The present invention has been made in view of the above problems, and it is an object to be solved to provide an exhaust gas purifying apparatus capable of preventing variations in filter temperature while avoiding power saving and extension of regeneration time. I am trying.

[0006]

An exhaust gas purifying apparatus of the present invention is a filter which is disposed in an exhaust path of a diesel engine and collects particulates discharged from the diesel engine, and the filter. An electric heating means disposed in the vicinity of the above for burning the particulate by energization, an air supply means for supplying air to the filter at the time of regeneration of the filter, and an operation of the air supply means as a cooling operation at the start of regeneration. Then, as a heating operation, a control means for instructing the operation of the air supply means and energization of the electric heating means, a filter temperature detection means for detecting a state quantity related to the temperature of the filter, and the estimated filter at the start of regeneration. It is characterized by further comprising a cooling release stopping means for stopping the cooling operation when the temperature is below a predetermined level.

[0007]

With the start of regeneration, first, the air supply means is operated as a cooling operation and the heater energization is cut off.
After that, as the heating operation, the air supply means is operated to energize the heater. However, when the filter temperature at the start of regeneration is estimated to be equal to or lower than a predetermined level due to the detected state quantity related to the temperature of the filter, the cooling operation is stopped.

In this way, when it is estimated that the temperature of the filter is sufficiently low, the cooling is stopped to save power and shorten the regeneration time.

[0009]

FIG. 1 shows an embodiment of an exhaust gas purifying apparatus according to the present invention.
Shown in. This exhaust gas purifying apparatus has a filter housing case 1 whose both ends are hermetically sealed, and an upstream side pressure sensor 7, a temperature sensor 6, a heater (main body) for detecting exhaust pressure are arranged in the filter housing case 1 from the upstream side to the downstream side. Electric heating means in the invention) 1
1, the filter 2, and the downstream pressure sensor 17 for detecting the downstream pressure of the filter are sequentially arranged. The exhaust pipe 3 of the diesel engine 20 is arranged on the upstream end wall of the filter housing case 1.
Is branched. The air supply pipe 10 is connected to an outlet of a blower 13 for supplying air through a solenoid valve 14.

On the other hand, the heater M and the motor M of the blower 13 are driven and controlled by a controller (control means) 8, and a rotation speed sensor 18 mounted on the diesel engine 20 and a water temperature sensor 19 for detecting the cooling water temperature. The output signal is output to the controller 8. The controller 8 has a microcomputer (not shown) with a built-in A / D converter, processes various data, and relays the switch 5
The heater 11 and the blower 13 are controlled by controlling the opening and closing of the heaters 5 and 56, and the abnormality alarm lamp 9 is turned on when an abnormality occurs (an abnormality signal is output). Reference numeral 58 is a voltage dividing circuit that divides the voltage applied to the heater 11 and outputs it to the controller 8. Reference numeral 59 is a current sensor that detects the current flowing to the heater 11. The controller 8 calculates the product of these voltages and currents. The amount of heat generated by the heater 11 is monitored.

Reference numeral 5 denotes a power feeding device, which includes a plug 51 connected to a commercial ground power source (not shown), a step-down transformer 52,
The full-wave rectifier 53 is provided, and the DC voltage output from the full-wave rectifier 53 is applied to the high end of each of the heater 11 and the blower drive motor M, and the low end of the heater 11 is grounded through the switch 56 so that the blower drive motor M has a low voltage. The lower end is grounded through the switch 55.

The filter 2 is a honeycomb ceramic filter (manufactured by Nippon Insulator kk, diameter 5.66 inches × length 6 inches), which is fired into a cylindrical shape using cordierite as a raw material. The filter 2 has a large number of vent holes penetrating both end faces thereof, one of the adjacent vent holes is plugged at the upstream end, and the other is plugged at the downstream end. The exhaust gas passes through the porous partition wall between the adjacent vent holes, and only the particulates are trapped in the vent holes. Both end faces of the filter 2 face the both end faces of the case 1 with a predetermined distance.

The heater 11 is composed of an electrothermal resistor made of nichrome wire, and is arranged close to the end surface of the filter 2 which is on the upstream side during regeneration. The operation of this device will be described below. (Particulate collection operation) Diesel engine 20
The exhaust gas discharged from the exhaust gas is introduced into the case 1 through the exhaust pipe 3, particulates in the exhaust gas are collected by the filter 2, and the purified exhaust gas is discharged from the tail pipe 4 to the outside.

(Filter Regenerating Operation) Next, the regenerating operation of the filter 2 will be described with reference to the flowchart of FIG. It should be noted that in this device, the filter regeneration operation is started by receiving power from an external power source while the engine is stopped and starting it by a manual operation. The solenoid valve 14 is opened immediately before the start of reproduction.

First, FIG. 2 shows a filter regeneration routine consisting of a filter regeneration determination routine (steps 100 to 111) executed during engine operation and a filter regeneration execution routine (steps 112 to 116) executed during engine stop. . First, the filter regeneration determination routine is started when the engine 20 is started, and step 1
00, the exhaust pressure P detected by the pressure sensors 7 and 17
1, P2, the engine speed n detected by the speed sensor 18, and the exhaust gas temperature T detected by the temperature sensor 6, the particulate trapping amount is calculated based on a memory map.

Next, in step 108, it is checked whether or not the searched particulate collection amount G exceeds a predetermined threshold value Gt. If it does not exceed, the process returns to step 100, and if it exceeds, the process returns to step 111. move on. In step 111, the lamp 91 for instructing filter regeneration is turned on, and the routine ends.

After that, when the driver visually recognizes that the lamp 91 for instructing the filter regeneration is turned on and turns on the regeneration switch (not shown) while the engine is stopped, the filter regeneration execution routine is started. In this routine, first, the blower 13 is activated in step 112, then the built-in timer is activated (114), the timer control subroutine is executed to perform the reproduction operation (116), and the reproduction is ended. In addition to the playback command, the relay switch 55,
56 is open / close controlled at a predetermined duty ratio and a predetermined timing to drive and control the blower motor M and the heater 11, so that the supply air flow rate and the energized power are controlled to have a predetermined pattern.

This timer control subroutine will be described with reference to FIG. This timer control subroutine is for actually driving the heater 11 and the blower 13 to execute regeneration. First, the cooling down subroutine 30 is executed to cool the filter 2 to approximately room temperature, and then the preheating subroutine 40. Is performed for a predetermined time to raise the temperature of the filter 2 to a predetermined temperature lower than the ignition temperature. This preheating subroutine is performed by the heater 1 at a temperature rising rate that does not adversely affect the filter 2.
1 is energized, the blower 13 is ignited, and the blower 13 is operated at a lower supply air flow rate to raise the temperature of the filter 2 uniformly and rapidly.

Next, the ignition combustion subroutine 50 is executed to burn the particulates. First, while increasing the supply air flow rate, the heater 11 is energized for a predetermined time to further raise the temperature of the filter 2 to ignite and burn the particulates. It should be noted that the ignition / combustion subroutine may be ended after a certain time has elapsed from the start thereof, or the ignition temperature (for example, 600
(° C) may be reached after a certain period of time. It is also possible to store the filter temperature change characteristic from the start to the end of the ignition / combustion subroutine 50 and control the energization power and the supply air flow rate so that the detected filter temperature follows this characteristic. When the termination of the ignition / combustion subroutine 50 is decided or before, the power supply to the heater 11 is cut off.

Next, the cooling subroutine 60 is executed to cool the filter 2. This cooling subroutine 60 is provided for the blower 1 for a predetermined time after the ignition and combustion subroutine 50 is completed.
3 is operated, whereby the filter 2 is cooled to a suitable temperature. Next, the cool down subroutine 30 will be described with reference to FIG.

This embodiment is carried out at the start of regeneration, and it is first checked whether or not a cooling flag, which will be described later, is set (whether cooling is commanded) (300),
If it is not standing, it is judged that the filter 2 is sufficiently cooled and cooling is unnecessary and returns to the main routine.
Proceed to the next preheat subroutine 40. When the cooling flag is set (when cooling is commanded), the blower 13 is operated to cool the filter (302) and the timer is started (304). Next, the timer is 2 minutes (cooling time)
Wait until (306), and then blower 1
Cancel 3 and return to the main routine. Although the blower 13 is once stopped in this embodiment, the blower stop 308 can be omitted because the blower 13 is operated in the next preheating subroutine 40.

Next, referring to the flow chart of FIG. 5, the cooling release execution sub-routine for the cooling flag will be described. It should be noted that this subroutine is an interrupt routine and is executed at predetermined intervals. First, it is checked whether the engine 20 is turned off (whether an ignition key (not shown) is turned off) (70
0), if not turned off, return to the main routine. If it is off, it is checked whether the timer is currently counting (701). If it is counting, the process jumps to step 704, and if it is not counting, the timer is started (702). In step 704, it is checked whether or not the timer is counting for 5 minutes or more. If it has not elapsed, the filter 2 is set to a high temperature and a cooling flag for a cooling command is set (706). The cooling flag is set down as it has been sufficiently cooled (708).

As a result, the filter 2 is always heated from the predetermined temperature, and variations in the maximum temperature of the filter 2 are reduced. (Embodiment 2) Another embodiment will be described with reference to FIG. This embodiment is a modification of the cooling execution determination subroutine relating to the cooling flag of FIG. 5, and estimates the temperature of the filter 2 from the cooling water temperature of the engine 20. This subroutine is executed at the beginning of the cool down subroutine 30.

First, the output signal from the water temperature sensor 19 is read to detect the cooling water temperature Tw (710), and if the detected cooling water temperature Tw exceeds a threshold water temperature Tc (40 ° C. here) stored in advance, the filter is filtered. 2 is set to a high temperature, a cooling flag for cooling command is set (706), and the cooling water temperature Tw
Is less than the threshold water temperature Tc stored in advance, the filter 2 is considered to be sufficiently cooled and the cooling flag is set (7).
08).

As a result, the filter 2 is always heated from the predetermined temperature, and variations in the maximum temperature of the filter 2 are reduced. That is, steps 700 to 704
And 710 to 712 detect the state quantity related to the temperature of the filter, and constitute the filter temperature estimating means in the present invention. Further, since step 708 substantially cancels the cooling operation, it constitutes the cooling stopping means in the present invention.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an exhaust gas purification device of the present invention,

FIG. 2 is a flowchart showing the reproducing operation,

3 is a flowchart showing a timer control subroutine of FIG. 2,

FIG. 4 is a flowchart showing a cooling subroutine of FIG.

FIG. 5 is a flowchart showing a sub-routine for determining whether to perform cooling.

FIG. 6 is a flowchart showing a cooling execution determination subroutine.

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor, 7 and 17 are pressure sensors, 8 is a controller (filter temperature estimating means, cooling stop means, control means), 11 is a heater (electric heating means).

Claims (1)

[Claims] 1. A filter disposed in an exhaust path of a diesel engine to collect particulates discharged from the diesel engine; and a particulate filter disposed near the filter and energized to energize the particulates. An electric heating means for burning the air, an air supply means for supplying air to the filter at the time of regeneration of the filter, an operation of the air supply means as a cooling operation at the start of regeneration, and an operation of the air supply means as a heating operation, and Control means for instructing energization to the electric heating means, filter temperature detecting means for detecting a state quantity related to the temperature of the filter, and the cooling operation when the estimated filter temperature at the start of regeneration is below a predetermined level An exhaust gas purifying apparatus comprising: a cooling release stopping unit for stopping the cooling.