JPH0763044A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To minimize the extent of air charging means driving power and regenerative time by installing a cooling shutdown means which terminates a filter cooling period in stopping any operation of an air charging means in the case where a gas temperature is less than the specified level. CONSTITUTION:A pressure sensor 7, a temperature sensor 6, a heater 11, a temperature sensor 19, and a 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 are driven and controlled by a controller 8 which is provided with a cooling period termination time judging means which judges whether a gas temperature is less than the specified level in a filter cooling period or not. In addition, it is also provided with a cooling shutdown means which terminates the filter cooling period in stopping any operation of an air charging means in the case where the gas temperature is less than the specified level. Thus, an increase in air charging means driving power and an extension of regenerative time both can be minimized 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. And heating the filter and particulates to burn the particulates, thereby regenerating the filter.

[0003]

Immediately after the above filter regeneration, the temperature of the filter is 600 ° C. or higher. If the exhaust gas exhausted from the engine is immediately dedusted in this state, the filter and its surroundings are treated. Is exposed to thermal shock due to a temperature difference of several hundreds of degrees Celsius, which accelerates deterioration of each part of the exhaust gas purification device and shortens its life.

Therefore, the present inventors consider that immediately after the filter regeneration, only the air supply means is operated for a predetermined time (for example, about 10 minutes) to cool the filter to an appropriate temperature (which can avoid the above problem). It was However, such setting of the filter cooling period has a problem that the time required for regeneration is extended, that is, engine starting is prohibited, and the driving power for air supply means is increased. In particular, the filter temperature has a variation immediately after regeneration, and also varies with the gas (air) temperature when the filter is cooled, and also with the variation of the voltage applied to the air supply means. Due to these variations, it is necessary to cool the filter. Time can vary,
It became clear as a result of various experiments. Therefore, the filter cooling period had to be set to the time required for cooling under the worst conditions.

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 rapidly cooling a filter after regeneration 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 which is disposed in the vicinity of and burns the particulate by energization,
Air supply means for supplying air to the filter when the filter is regenerated, temperature detection means for detecting gas temperature on the downstream side of the filter, operation of the air supply means and energization of the electric heating means, and the filter In the filter cooling period after the regeneration of the, the control means for cooling the filter by instructing the operation of the air supply means and the stop of energization to the electric heating means, and the control means, the filter cooling period. A cooling period end timing determining means for determining whether the gas temperature is below a predetermined level, and a cooling stop for stopping the operation of the air supply means and ending the filter cooling period when the gas temperature is below a predetermined level. And means.

[0007]

When the regeneration is completed, the heater energization is cut off as the filter cooling operation, and the air supply means is operated. After that, the temperature of the gas (air) discharged from the filter is detected on the downstream side of the filter, and when this gas temperature falls below a predetermined threshold level, the filter is considered to be sufficiently cooled and the operation of the air supply means is stopped. To do.

In this way, the temperature of the filter and its surroundings can be promptly lowered after regeneration, the life of each part can be extended, and the operation of the air supply means is stopped immediately after confirming a sufficient drop of the filter temperature. Therefore, there is an excellent effect that the increase of driving power for the air supply means and the extension of the reproduction time are minimized.

[0009]

FIG. 1 shows an embodiment of an exhaust gas purifying apparatus according to the present invention.
Shown in. This exhaust gas purifying device has a filter housing case 1 whose both ends are sealed, and a pressure sensor 7 for detecting pressure on the upstream side of the filter and a temperature sensor 6 on the upstream side of the filter are disposed in the filter housing case 1 from the upstream side to the downstream side. A heater (electric heating means in the present invention) 11, a filter 2, a temperature sensor on the downstream side of the filter (temperature detecting means in the present invention) 19, and a pressure sensor 17 for detecting the pressure on the downstream side of the filter are arranged in this order. The exhaust pipe 3 of the diesel engine 20 is arranged on the upstream end wall of the filter housing case 1, and the air supply pipe 10 is branched from the middle of the exhaust pipe 3. The air supply pipe 10 is connected to an outlet of a blower (air supply means in the present invention) 13 for air supply through a solenoid valve 14.

On the other hand, the heater M and the motor M of the blower 13 are drive-controlled by a controller (cooling period end timing determining means, cooling stopping means, control means in the present invention) 8 and mounted on the diesel engine 20. The output signal of the rotation speed sensor 18 is output to the controller 8. The controller 8 includes a microcomputer (not shown) with a built-in A / D converter, and relay switches 55, 5
The heater 6 and the blower 13 are controlled by opening / closing 6 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 detects the partial pressure of the voltage applied to the heater 11 and outputs it to the controller 8. Reference numeral 59 is a current sensor that detects the energizing current to the heater 11, and the controller 8 controls the current and voltage. The calorific value of the heater 11 is monitored by the product of

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 relay switch 56. The lower end of the relay is grounded through the relay 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, based on a memory map, the particulate collection amount G.
To calculate.

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,
The blower motor M and the heater 11 are controlled to be opened / closed at a predetermined duty ratio and a predetermined timing to drive and control the blower motor M and the supplied electric power so as to have a predetermined pattern.

The above timer control subroutine will be described with reference to FIG. This timer control subroutine actually drives the heater 11 and the blower 13 to execute the regeneration. First, the cooling air subroutine 30 is executed to cool the filter 2. The cooling sub-routine 30 drives the blower 13 to cool the filter 2 without energizing the heater 11, and is executed for a predetermined time, for example, 2 minutes.

Next, the preheat subroutine 40 is executed for a predetermined time to raise the temperature of the filter 2 to a predetermined temperature lower than the ignition temperature. In this preheating subroutine, the heater 11 is energized at a heating rate that does not adversely affect the filter 2 and the blower 13
After the ignition, the filter 2 is operated at a lower supply flow rate to uniformly and rapidly raise the temperature. Next, the ignition combustion subroutine 50 is executed to burn the particulates.

First, while increasing the flow rate of supply air, the heater 11 is energized for a predetermined time to further raise the temperature of the filter 2 to ignite and burn the particulates. The ignition / combustion subroutine may be terminated after a certain period of time from the start of the subroutine, or after a certain period of time after the ignition temperature (for example, 600 ° C.) is reached. Also, the ignition combustion subroutine 50
It is also possible to store the filter temperature change characteristic from the start to the end 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, and this timer control subroutine is ended. The cooling subroutine 60 described above will be described with reference to FIG. First, with the blower 13 kept on, the heater 11 is turned off (600), and external air is introduced into the filter 2 at a predetermined flow rate to cool the filter 2.

Next, the output signal of the temperature sensor 19 is read to detect the air temperature T emitted from the filter 2 (60
2) Wait until the air temperature T falls below 400 ° C (6
04), when the air temperature T becomes lower than Tc = 400 ° C., the blower 13 is turned off, and the cooling subroutine 60 ends (606). As described above, in this embodiment, the air temperature T downstream of the filter 2 is monitored during cooling after the regeneration of the filter 2 is completed. The temperature Tc at which the adverse effect on the filter 2 due to the start of operation of the engine 20 can be avoided
The blower 13 is continuously operated until the temperature of the filter 2 drops to this temperature Tc, and the blower 13 is immediately turned off to prevent further extension of the regeneration time and prevent further increase in power consumption.

[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,

4 is a flowchart showing the cooling subroutine of FIG. 3,

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor, 7 and 17 are pressure sensors, 8 is a controller (cooling period end timing determination means, cooling stop means, control means), 11 is a heater (electric heating means),
19 is a temperature sensor (temperature detection means).

Claims (1)

[Claims] 1. A filter disposed in an exhaust path of a diesel engine for collecting particulates discharged from the diesel engine; and a filter disposed near the filter for energizing to provide particulates. Electric heating means for burning, air supply means for supplying air to the filter during regeneration of the filter, temperature detection means for detecting gas temperature on the downstream side of the filter, operation of the air supply means, and energization of the electric heating means And a control means for cooling the filter by instructing the operation of the air supply means and the stoppage of energization to the electric heating means during the filter cooling period after the filter is regenerated. Is a cooling period end timing determining means for determining whether the gas temperature is below a predetermined level during the filter cooling period, and when the gas temperature is below a predetermined level, Exhaust gas purifying device, characterized in that it comprises a cooling stop means to stop the operation of the air unit to terminate the filter cooling period.