JP2605826Y2 - Engine exhaust gas purifier - Google Patents

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 an engine provided with a particulate trap for collecting exhaust particulates in the middle of an exhaust pipe, and particularly to a backwash means for regenerating the particulate trap. The present invention relates to an exhaust gas purification device for an engine, comprising:

[0002]

2. Description of the Related Art In diesel engines, particulates in exhaust gas (mainly particulates such as soot)
In order to collect the dust, a trap (filter) having a honeycomb structure is stored in a trap container formed to constitute a part of the exhaust pipe, and the trap collects the particulates. Also in this type of device,
In order to regenerate the filter, high heat is supplied directly to the trap and the particulates are burned by this heat to regenerate it. In which the particulates trapped in the trap are removed from the trap and regenerated by the backwash air flow (Japanese Patent Laid-Open No. Sho 62
-26312, JP-A-64-77715, JP-A-1-159408, etc.).

[0003] In particular, the latter (1) does not require direct supply of high heat for regeneration to the trap, does not damage the trap due to thermal stress, and (2) has no ash accumulation in the trap.
It has features in terms of durability and reliability that it does not cause trap clogging, and is considered promising as a particulate trap device.

[0004]

However, even with the backwashing type particulate trap device having the above-mentioned advantages, there is no possibility that the trap will be damaged by heat or cracked by heat. Self-regeneration of the trap, which occurs separately from the regular regeneration, can cause melting of the trap,
Thermal cracks may occur. Self-regeneration is when the exhaust temperature in the trap rises above the soot ignition temperature.
A phenomenon in which soot collected in a trap ignites spontaneously. This self-regeneration has a soot ignition temperature of 550 ° C to 600 ° C.
Considering that the exhaust gas temperature of the engine reaches about 700 ° C. at full load at high speed, this phenomenon can occur relatively frequently.

[0005] Strict melting of the trap and thermal cracks occur strictly when soot is rapidly burned due to a change in engine operating conditions immediately after self-regeneration. The explosive burning of soot
Specifically, immediately after the soot in the trap is ignited, when the engine load decreases and the engine speed decreases,
In other words, when the oxygen concentration in the exhaust gas increases and the exhaust gas flow rate decreases, the explosive combustion of soot exceeds the melting limit of the trap in the trap.
In some cases, the temperature may reach 900 ° C or higher.

Accordingly, the present invention detects the occurrence of self-regeneration in a particulate trap apparatus of the type in which the trap is regenerated by a backwash air flow in order to prevent such breakage, melting damage and cracking of the trap. An object of the present invention is to prevent the temperature from being excessively increased by performing a backwashing process when the cleaning is performed.

[0007] It is to be noted that in the related art, in order to protect the trap, an "exhaust gas purification apparatus for an engine" (actually opened) is configured to intentionally adjust the injection amount of a fuel injection nozzle to lower the temperature of exhaust gas. No. 57-95414), but even with this proposal, an abnormal rise in temperature due to self-regeneration of the trap cannot be avoided.

[0008]

In order to achieve the above-mentioned object, the present invention provides a particulate trap provided in an exhaust pipe, and a high-pressure particulate matter generated in a direction opposite to an exhaust flow in order to regenerate the particulate trap. Backwashing means for supplying gas, detecting means for monitoring a change in the state of the trap and detecting self-renewal thereof, and periodically operating the backwashing means at a predetermined time.
And self-regeneration is detected by the detection means.
Activates the backwashing means for longer than the specified time
And control means for causing the

[0009]

[Function] The particulate trap in the exhaust pipe uses exhaust traps (particulates) due to traps inside the trap.
And exhaust only the clean exhaust gas from the exhaust pipe. When there is an input of self-regeneration by the detecting means, the control means operates the backwashing means for a longer time than the normal backwashing time. Therefore, due to the pressure wave of the high-pressure air injected from the downstream side of the trap toward the trap, all the exhaust particulates adhering to the trap are removed from the trap. Therefore, the temperature rise in the trap is suppressed to a minimum, and breakage, melting, and cracking of the trap are prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a system of an exhaust gas purifying apparatus for an engine according to the present invention.

The particulate trap 1 is connected to one end of a trap container 2 and an exhaust pipe 3 on the engine side.
It has an exhaust gas inlet 6a for introducing the exhaust gas of the engine E, and the other end is connected to the exhaust pipe 5 on the silencer side to exhaust the exhaust gas in the trap container 2 to the outside. It has a gas outlet 6b, and has a heater chamber 7 at the lower part of the trap container 2 for receiving exhausted particulates (particulates) removed from the trap 4 and incinerating them.

More specifically, the trap container 2 is formed in a substantially box shape which is long in the flow direction of the exhaust gas, and a porous ceramic material having good air permeability is used for the inner surface constituting the side plate of the trap container 2. Trap 4 formed in a honeycomb shape
Is horizontally extended. In other words, trap 4
Is provided so as to partition the inside of the trap container 2 into an upper exhaust gas introduction chamber 8 and a lower heater chamber 7. An electric heater 10 is attached to a portion of the trap container 2 that divides the heater chamber 7 in order to incinerate the exhaust fine particles removed from the trap 4. An outlet 11 is formed to allow the exhaust fine particles to be extracted to the outside.

A cell 12 for efficiently collecting the exhaust particulates and separating the collected exhaust particulates from the trap 4 and dropping them into the heater chamber 7 below is provided with a chamber 8 for introducing an exhaust gas. It is vertically elongated in a direction connecting the lower heater chamber 7. That is, the cell 12 constitutes a collecting surface for attaching and collecting the exhaust particulates, and also functions as a guide surface for dropping the exhaust particulates attached thereto downward. Note that the cell 12 is not specified as a honeycomb cross section in view of these functions.

Backwashing means 13 for regenerating trap 4
Is a nozzle portion 14 attached to the exhaust pipe 5 so as to face the exhaust downstream surface of the trap 4, and an air tank (high-pressure air supply source) for supplying high-pressure air to the nozzle portion 14.
15, a high-pressure air supply pipe 16 that connects the air tank 15 and the nozzle section 14 in communication with each other, and an electromagnetic on-off valve 17 that is provided in the middle of the high-pressure air supply pipe 16 and opens and closes the high-pressure air supply pipe 16. And particulate trap 1
Detecting means 18 for detecting the self-regeneration of the trap 4 by detecting the state of the trap, and opening the solenoid on-off valve 17 at the time of normal trap regeneration and at the time of self-regeneration of the trap 4 by the input of the detection means 18; And a controller 19 (control means) electrically configured to close the shutter 17.

The detecting means 18 detects the exhaust gas temperature at the exhaust gas inlet 4 and detects the exhaust gas inlet 4 and the ambient temperature in the trap container individually, in addition to the temperature sensor 18a for inputting the result to the controller 19. A temperature sensor for inputting the result to the controller 19, a brightness detection sensor for optically or electromagnetically detecting the surface brightness of the exhaust gas inlet 4 and inputting the result to the controller 19, O ₂ or CO _2.
O which detects the density and inputs the result to the controller 19
Either ₂ or CO ₂ sensors are used. The control circuit of the controller 19 is electrically configured to execute the control shown in the flowchart of FIG.

Normal trap regeneration control: When the controller 19 is started simultaneously with the start of the engine E, the controller 19 integrates the operation time of the engine E using the internal timer of the controller 19,
When the engine integrated operation time exceeds a predetermined operation integrated value, the backwashing means 13 is operated to execute normal trap regeneration control. That is, the electromagnetic on-off valve 17 is turned on (open) for 50 msec to supply the high-pressure air in the air tank 15 to the nozzle unit 14 via the high-pressure air supply pipe 16, and the pressure wave of the high-pressure air collects the cells 12. Exfoliated particles adhered to the surface are peeled and dropped. Simultaneously with the completion of the trap regeneration, the accumulated engine operation time is reset to "0", and the operation time is newly accumulated for the next regeneration. Thereafter, the controller 19 operates the electric heater 10 at an appropriate time to incinerate the exhaust particulates accumulated in the heater chamber 7.

Trap protection control This trap protection control is executed when the exhaust gas temperature exceeds 500 ° C. That is, the controller 1
Reference numeral 9 denotes that when the detected value of the temperature sensor 18a (detection means 18) provided at the exhaust gas inlet 6a exceeds 500 ° C. during the above-described normal trap regeneration control, that is, when the temperature of the exhaust gas is reduced to If the temperature is exceeded, it is determined that there is a risk that self-regeneration may occur in the trap 4, and the back-washing means 13 is back-washed to perform trap regeneration completely independent of normal trap regeneration control. That is, when the temperature of the exhaust gas is 500 ° C. or higher, the exhaust fine particles adhering and accumulating on the trap 4 are burned at once, and are melted and damaged in the trap 4.
To prevent that the thermal cracking is arising. The protection control of the trap 4 is performed by setting the electromagnetic on-off valve 17 to 1.1 to 3 times the opening time of the electromagnetic on-off valve 17 in the normal trap regeneration control.
ON for 55 times ( 55 to 150 msec), the high pressure air in the air tank 15 is supplied to the nozzle portion 14 through the high pressure air supply pipe 16, and the pressure wave of the high pressure air causes
Exhaust fine particles adhering to the collecting surface of the trap 4 are separated and dropped.

As described above, in the trap regeneration control of the present invention, the backwashing time in the trap protection control is set to be 1.1 to 3 times the backwashing time in the normal trap regeneration control for the following reason. .

That is, the air that actually produces the working air is generally an air compressor that uses the engine E as a power source, and maintains the air pressure of the air tank at an air pressure that can sufficiently operate various pneumatic components of the vehicle. To keep
The fact that a large amount of air is consumed for trap regeneration is not preferable in itself. However, if the rise in the exhaust gas temperature of the engine E is viewed from another viewpoint,
The trap protection control is performed when the air supply capacity of the air compressor is high and the air recovery capacity of the air tank is high enough to operate at a high speed and a high load. Can be made longer than the trap regeneration time of normal trap regeneration control. Therefore, if all the particulates trapped in the trap 4 are removed during the high-speed and high-load operation, melting and thermal cracking due to self-ignition of the trap 4 are avoided, and the trap is dependent on normal trap regeneration control. The degree can be reduced conversely.

According to the present invention, for the above reasons, the backwashing time during the trap protection control is set to be 1.1 to 3 times the backwashing time during the normal trap regeneration control. The purpose of the present invention is to reduce the temperature, prevent erosion and thermal cracks due to self-ignition, and maintain the performance of the trap 4 for a long time.

In the case where temperature sensors are individually provided as the detecting means 18 so that the temperature of the exhaust gas at the exhaust gas inlet 6a and the ambient temperature in the trap container can be individually detected, the controller 19 controls these temperatures. The difference between the input values of the sensors is compared, and when the ambient temperature in the trap container exceeds approximately 20 ° C. from the exhaust gas temperature at the exhaust gas inlet 4, it is determined that self-regeneration has occurred reliably, and the backwashing means 13 is determined.
Backwash operation.

The temperature of the trap container 2 is set to 500 ° C. or more.
The state in which the ambient temperature exceeds approximately 20 ° C. from the exhaust gas temperature at the exhaust gas inlet 6a for a predetermined time (for example, about 3 ° C.).
0 sec) The self-regeneration may be determined based on whether or not it is continuous, and the accuracy of the self-regeneration determination by the temperature sensor 18a may be improved.

When a brightness detection sensor for detecting the brightness of the surface of the exhaust gas inlet 6a is provided as the detection means 18, the backwash means 13 is backwashed when the temperature of the exhaust gas is 500 ° C. or more. When operating and providing an O ₂ sensor or CO ₂ at each of the exhaust gas inlet 6 a and the exhaust gas outlet 6 b as the detection means 18, the controller 19 calculates the difference between the O ₂ concentration or the CO ₂ concentration in the exhaust gas. When the difference in concentration between the exhaust gas inlet 6a and the exhaust gas outlet 6b becomes equal to or higher than a predetermined value of 500 ° C. or more, the backwash means 13 is operated.

Therefore, the melting and cracking of the trap 4 during high-speed and high-load operation, which has been a problem in the past, can be reliably prevented.

[0026]

[Effects of the Invention] As is apparent from the above description, the present invention provides the following excellent effects.

(1) During trap self-regeneration, the trapped exhaust fine particles can be washed off with a minimum of high-pressure air, thereby preventing melting and thermal cracking of the trap.

(2) Exhaust gas can be stably purified.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a preferred embodiment of an exhaust gas purifying apparatus for an engine according to the present invention.

FIG. 2 is a flowchart showing control contents of a controller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Particulate trap 4 Trap 13 Backwashing means 18 Detection means 19 Controller (control means)

Claims (1)

(57) [Scope of request for utility model registration] 1. A particulate trap interposed in an exhaust pipe, backwashing means for supplying high-pressure gas to the trap from a direction opposite to an exhaust flow to regenerate the trap, and monitoring a change in the state of the trap. Detecting means for detecting the self-regeneration, and periodically operating the backwashing means for a predetermined time, and
When the self-regeneration is detected by the detection means,
Control means for operating the means for a longer time than the predetermined time .