JPS5925025A - Exhaust gas purging device of diesel engine - Google Patents

Abstract

PURPOSE:To keep a proper air-fuel ratio and perform complete combustion of the fuel even if the fuel supply decreases as a result of the delivery port of a fuel feed nozzle being narrowed, by installing a means for detecting a change in fuel supply amount and a means for controlling air supply amount to a burner device. CONSTITUTION:In operation of a burner device 4, a fuel pressure on the downstream side from an orifice 31 of a fuel supply passage 14 is detected by a pressure detector 32, the result is inputted to a solenoid valve control circuit 37 of a controller 26 to compare it with the set pressure of a reference value memory circuit 38 by means of a comparator 39, and the result is fed to the burner device 4 to detect a change in an actual fuel amount. When a nozzle is brought to narrowed condition and a fuel amount is decreased, below the set value, the fuel pressure exceeds the reference value, and a difference is produced between two pressure signals inputted to the comparator 39. Thereby, an H-level signal is outputted from said comparator 39 to change a solenoid valve 33 into operating condition (in that an air feed passage 16 is throttled), and the air amount for combustion fed to the burner device 4 is decreased for correction corresponding to the fuel amount to keep the air-fuel ratio in a proper range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust purification device for a diesel engine,
In particular, in exhaust systems equipped with a filter member that collects particulates in the exhaust gas and a burner device that eliminates clogging of the filter member, secondary atmosphere due to constriction of the fuel supply nozzle of the burner device Concerning pollution prevention measures.

Traditionally, in diesel engines, in order to prevent particulates such as carbon particles contained in large quantities in the exhaust from being released into the atmosphere,
2. Description of the Related Art Exhaust purification devices are well known in which a porous filter member, such as a honeycomb-shaped porous filter member, is disposed in the exhaust passage of an engine, and particulates in the exhaust gas are collected by the filter member.

However, this method has a problem in that the filter member becomes clogged due to the accumulation of particulates as the engine is operated for a long period of time, causing an increase in the exhaust pressure of the engine and a decrease in its output.

Therefore, conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 49-'71315, a fuel supply nozzle that discharges and supplies fuel and a combustion air are supplied to the exhaust passage upstream of the above-mentioned filter member. It is equipped with an air supply passage and a spark plug, and the fuel from the fuel supply nozzle is brought into contact with the air from the air supply passage. A burner device is provided, and the burner device is operated periodically or when the filter member becomes clogged, and the combustion gas is used to heat and burn the particulates accumulated on the filter member, thereby cleaning the filter member. A device designed to eliminate clogging has been proposed.

By the way, in this proposal, since fuel is frequently discharged and supplied from the fuel supply nozzle of the burner device, the discharge port of the nozzle is always open. (When clearing clogging of parts)
Fuel remains in the nozzle and its edges are poorly cut, and as a result, this residual fuel may carbonize due to the heat of the high-temperature nozzle, narrowing the nozzle nozzle hole and the discharge port at its tip. . Furthermore, when the burner device is not in operation, fine particles in the exhaust gas flowing through the exhaust passage may enter and adhere to the open nozzle outlet, narrowing the outlet. When the discharge port of the nozzle is narrowed and its passage area is reduced in this way, the amount of fuel discharged and supplied from the nozzle decreases, and the ratio between the fuel and the normally supplied combustion air changes. There was a fear that the air-fuel ratio would deviate from the proper air-fuel ratio, and as a result, the fuel would not be completely combusted and a large amount of unburned components (HC) would be generated, leading to secondary air pollution.

In view of this, the present invention detects a change (reduction) in the amount of fuel actually supplied to the burner device when the burner device is operated, and the amount of combustion air to be supplied to the burner device. By correcting and controlling the ratio of the amount of fuel to the actual fuel supply amount to be within an appropriate range, it is possible to ensure complete combustion of the discharged fuel even if the nozzle hole and discharge port of the fuel supply nozzle are narrowed. Therefore, the purpose is to reliably prevent secondary air pollution caused by burner operation over a long period of time.

To achieve this object, the present invention has a configuration in which a filter member for collecting fine particles such as carbon particles in the exhaust gas is disposed in the exhaust passage, and the filter member is prevented from clogging in the exhaust passage upstream of the filter member. In a diesel engine exhaust gas purification device equipped with a burner device that eliminates the problem, the fuel supply amount change detection means detects a change in the amount of fuel supplied to the burner device, and the fuel supply amount change detection means responds to an output of the fuel supply amount change detection means. By providing an air supply amount control means for controlling the amount of combustion air supplied to the burner device so that the ratio of fuel and air is within an appropriate range, the discharge port of the fuel supply nozzle of the burner device is narrowed. Even if the supplied fuel decreases, the air-fuel ratio is always maintained at an appropriate air-fuel ratio to ensure complete combustion of the fuel.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

1 to 4 show a first embodiment, 1 is a diesel engine, 2 is an exhaust passage for discharging exhaust from the engine 1, and an exhaust passage 2 is provided in the middle of the exhaust passage 2. A porous filter member 6 in the form of a comb is disposed to collect fine particles such as carbon particles in the exhaust gas flowing through the exhaust gas.

Further, a burner device 4 is disposed in the exhaust passage 2 on the upstream side of the filter member 6 to eliminate clogging of the filter member 5 due to accumulation of particulates.

As shown in enlarged detail in FIG. 2, the burner device 4 includes a cylindrical casing 5 and a combustion chamber that is fitted into the casing 5 with a certain gap 6 therebetween and that communicates with the exhaust passage 2. 7
and a combustion cylinder 9 in which air supply holes 8°8, .
The fuel supply nozzle 10 is provided in the fuel supply nozzle 10 and has a nozzle hole 10a that penetrates in the axial direction. A pair of electrodes 12 are arranged to face each other with a predetermined interval in front of the discharge port 11.
The spark plug 12 has spark plugs 12a and 12a. The nozzle hole 10a of the fuel supply nozzle 10 is connected to a fuel tank 15 via a fuel supply passage 14 with a fuel pump 1!1 interposed therebetween, and the gap 6 between the casing 5 and the combustion tube 9 is The spark plug 12 is connected to an air pump 17 via an air supply passage 16, and further connected to a battery 19 via an ignition switch 18, and is supplied with fuel in the fuel tank 15 by a fuel pump 15. From the discharge port 11 of the nozzle 10 to the inside of the combustion tube 9 (combustion chamber 7)
The air pump 17 discharges the air into the air supply holes 8, 8.
．． The mixture is mixed with air blown out from the ignition switch 18 and ignited by discharge ignition of the spark plug 12 to generate high-temperature combustion gas, and the combustion gas is passed to the downstream filter member 6. The filter member 5 is unclogged by heating and burning the particulates deposited on the filter member 5 by passing through the filter member 5. Note that 20 is a check valve for keeping the discharge pressure of the fuel cylinder 15 constant, and 21 is a check valve for keeping the discharge pressure of the air pump 17 constant. Further, in FIG. 2, reference numeral 22 denotes a ring-shaped throttle attached to the inner circumference of the combustion tube 9 so as to protrude into the combustion chamber 7, and has air supply holes 8°8, .
- This is to increase the flow velocity of air blown into the combustion chamber 7 from the combustion chamber 7 to improve mixing efficiency with fuel. 2
5 is an auxiliary air passage formed in the fuel supply nozzle 10 so as to surround the nozzle hole 10a, the upstream end of which is in the gap 6 between the casing 5 and the combustion cylinder 9, and the downstream end in the nozzle 1.
0 are opened at the discharge ports 11 at the tip, respectively, and the discharge ports 1
By blowing out air from the nozzle hole 10a, the fuel is atomized and the fuel in the nozzle hole 10a is cooled to prevent its carbonization, thereby preventing the nozzle 10 from clogging.

On the other hand, inside the filter member 6, there is a pair of electrodes 24 facing each other at a constant interval in the axial direction (exhaust flow direction).
．． 24 is buried, and each electrode 24 is made of fine particles (carbon particles) deposited on the filter member 6.
The filter member 6 is connected to a clogging detector 25 which detects the clogging state of the filter member 6 based on a decrease in the resistance value and outputs an H level signal (actuation signal) upon detection. The output of the clogging detector 25 is input to a burner device control circuit 27 that is built into a control device 26 and controls the operation of the burner device 4 . As shown in detail in FIG. 4, the burner device control circuit 27 includes an air pump drive circuit 28 that receives the output of the clogging detector 25 to drive and control the air pump 17, and also controls the output of the clogging detector 25. The fuel pump drive circuit 29 receives the output and controls the fuel pump 15, and the ignition switch drive circuit '50 receives the output from the clogging detector 25 and controls the ignition switch 18. When the device 25 outputs an H level signal, the air pump 17, the ignition switch 18, and the fuel pump 16 are operated to operate the burner device 4.

Furthermore, as shown in detail in FIG. 3, the fuel pump 15
An orifice 51 is formed in the fuel supply passage 14 between the fuel supply nozzle 10 of the burner device 4 and the fuel supply passage 14 downstream of the orifice 61 (on the nozzle 10 side). A pressure detector 52 is provided to detect fuel pressure.

Further, an air supply passage 1 is provided in the middle of the air supply passage 16.
A normally open solenoid valve 9-65 that throttles and closes the valve 6 is provided. The solenoid valve 56 includes a conical valve body 55 that controls the increase or decrease of the opening area of the valve seat 54 provided in the air supply passage 16, and an actuator 66 made of a solenoid connected to the valve body 55. '5 Valve body according to the power signal input to B! +5
The air supply passage 16 is narrowed by moving the air supply passage 16, and the amount of air flowing through the passage 16 is controlled to be reduced.

Then, the output of the pressure detector 52 is transmitted to the control device 2.
6, the solenoid valve 55 is connected to the actuator 6.
Solenoid valve control circuit that controls the drive via 6! +7 is input. The solenoid valve control circuit 57 has a fourth
As shown in detail in the figure, - a reference value storage circuit 68 that stores a value that is a predetermined value smaller than the fuel pressure in the fuel supply passage 14 between the fuel pump 15 and the orifice 51 set by the check valve 20; , a comparator 59 for comparing the reference pressure signal from the reference value storage circuit 58 and the pressure signal from the pressure detector '52, and an actuator 56 for the solenoid valve '5'5 in response to the output of the comparator 59 and a solenoid valve drive circuit 40 for driving and controlling the pressure detector '5.
When the pressure signal from 2 is larger than the reference pressure signal from the reference value storage circuit 68, the comparator 69 outputs an H level signal to throttle the solenoid valve 5'5 and the air supply passage 16 to reduce its passage area. The operation is controlled in two stages so that the - Here, the reference value of the reference value storage circuit 58 is the pressure in the fuel supply passage 14 downstream of the orifice 51 in an initial state, that is, a normal state in which the fuel supply nozzle 10 is not clogged. is of value equal to .

Therefore, the orifice 61, the pressure detector 62, the reference value storage circuit 58 of the solenoid valve control circuit '57, and the comparator 59 detect changes in the actual amount of fuel being supplied to the burner device 4. A fuel supply amount change detecting means 41 is constructed, and also includes a drive circuit 40 of the solenoid valve control circuit '57 and the solenoid valve 6.
! Depending on the output of the fuel supply amount change detection means 41 according to 7-35)
The air supply amount control means 42 is configured to control the amount of air supplied in a decreasing direction so that the amount of air supplied is reduced.

Next, to explain the operation of the above embodiment, fine particles such as carbon particles in the exhaust gas flowing through the exhaust passage 2 as the engine 1 operates are collected by the filter member B, and the exhaust gas is purified and released into the atmosphere. be done.

After a certain period of time has elapsed, when the filter member 6 becomes clogged due to the accumulation of fine particles, the clogging detector 25 detects this and outputs an activation signal. The control circuit 27 operates to operate the air pump 17, ignition switch 18, and fuel pump 15, thereby supplying fuel to the burner device 4 through the fuel supply passage 14 and combustion air through the air supply passage 16. respectively supplied with said burner device 4
is activated. Due to the operation of the burner device 4, high-temperature combustion gas generated in the combustion tube 9 (combustion chamber 7) flows to the filter member 6 on the downstream side, heating and burning the particulates deposited on the filter member 5. Thus, the filter member 6 is unclogged.

In that case, the fuel pressure downstream of the orifice 51 of the fuel supply passage 14 is detected by the pressure detector '52, and this pressure signal is transmitted to the solenoid valve control circuit 57 of the control device 26.
The comparator 69 compares the reference fuel pressure from the reference value storage circuit 58 with the set pressure in the fuel supply passage 14 downstream of the orifice 61, thereby reducing the actual pressure being supplied to the burner device 4. A change in fuel amount is detected. That is, the fuel supply nozzle 1 of the burner device 4
When the nozzle hole 10a and the discharge port 11 of No. 0 are not clogged at all and fuel is being discharged and supplied from the nozzle 10 to the combustion chamber 7 as originally set, the fuel supply passage 1
Since the fuel pressure on the downstream side of the orifice 51 of No. 4 is equal to the reference value of the reference value storage circuit 68, the comparator! An L level signal is output from +9 and the solenoid valve! I! 1 is kept inactive (fully open). As a result, the amount of air supplied to the burner device 4 is maintained at an appropriate value corresponding to the above fuel supply amount (an amount corresponding to an air-fuel ratio of 17 to 35).

On the other hand, due to long-term use of the burner device 4, the fuel remaining in the fuel supply nozzle 10 when the burner device 4 is not in operation may be carbonized by the high temperature nozzle heat, or the particulates in the exhaust gas may enter the discharge port 11 of the nozzle 10 when the burner device 4 is not in operation. The nozzle hole 10a of the nozzle 10 and the discharge port 11 may be
When the fuel supply passage 1 is in a constricted state and the amount of fuel discharged from the nozzle 10 is less than the set value, the fuel supply passage 1
The fuel pressure on the downstream side of the orifice 51 of No. 4 is higher than the reference value, and a difference occurs in the measured pressure signal input to the comparator 39, so an H level signal is output from the comparator 59 and the solenoid valve 55 is in operation (air supply passage 1
6). As a result, burner device 4
The amount of combustion air supplied to the engine is corrected to decrease in accordance with the reduced amount of fuel, thereby still maintaining the air-fuel ratio within the appropriate range (17 to 35).

Therefore, even if the fuel supply nozzle 10 of the burner device 4 becomes constricted and the amount of fuel discharged decreases, the air-fuel ratio can always be maintained within an appropriate range and the discharged fuel can be completely combusted, so that the burner By suppressing the generation of IC due to operation, secondary air pollution can be prevented for a long period of time.

Note that when the clogging of the filter member 6 is cleared after a predetermined period of time has elapsed from the operating diameter of the burner device 4, the clogging detector 25 stops operating and the burner device control circuit 27 stops operating, and the fuel pump 16, The ignition switch 18 and the air pump 17 are deactivated, thereby deactivating the burner device 4 and completing the clogging removal operation.

In the above embodiment, the solenoid valve 6'5 is operated in only two stages: fully open and the air supply passage 16 is closed. The operation may be controlled continuously so that the amount of air supplied is proportionally reduced in response to a decrease in the amount of fuel supplied to the device (reduction in the amount of fuel supplied to the device), which has the advantage that the air-fuel ratio can be controlled more precisely. have

FIG. 5 shows a second embodiment (the same parts as in FIGS. 1 to 3 are given the same reference numerals and detailed explanation thereof is omitted). Control is not performed electrically as in the first embodiment, but mechanically.

That is, in FIG. 5, reference numeral 45 denotes a relief passage that communicates the discharge side and suction side of the air pump 17 to relieve a portion of the air discharged from the air pump 17, and there is a relief passage in the middle of the relief passage 45. A relief valve 44 is provided to control the opening and closing of the valve 4'5. The relief valve 4
4 is a valve body 45 that opens and closes the relief passage 45, and a diaphragm 47 connected to the valve body 45 via a rod 46.
and a pressure chamber 48 defined by the diaphragm 47.
and an atmospheric pressure chamber 49, and a spring 50 compressed into the atmospheric pressure chamber 49 and urging the valve body 45 in the valve closing direction. When the pressure on the downstream side of the orifice 61 of the fuel supply passage 14 increases, this pressure biases the diaphragm 47 to the left in the figure against the biasing force of the spring 50, and the valve body 45 is opened,
It is configured to open the relief passage 45.

Therefore, in this embodiment, when the fuel supply nozzle 10 of the burner device 4 becomes constricted and its fuel discharge amount decreases, the pressure downstream of the orifice 51 of the fuel supply passage 14 increases, and this pressure increase causes the relief valve to open. 44 is opened, the relief passage 4'5 is opened, and air IJ-F is performed. As a result, the amount of air supplied to the burner device 4 is corrected to be reduced by a portion of the air IJ. As a result, the ratio of air and fuel supplied to the burner device 4, that is, the air-fuel ratio, is maintained within an appropriate range (17 to 35), thereby completely burning the fuel and preventing secondary air pollution caused by burner operation for a long period of time. can be prevented.

In each of the above embodiments, the clogging of the filter member 6 is detected by the clogging detector 25 and the burner device 4 is activated. The burner device may be operated periodically when the value is reached, and the same effects as in the above embodiment can be achieved.

As explained above, according to the present invention, there is provided an exhaust purification device for a diesel engine that includes a filter member that collects particulates in exhaust gas flowing through an exhaust passage, and a burner device that eliminates clogging of the filter member. , detecting a change in the amount of fuel actually supplied to the burner device, and adjusting the amount of air supplied to the burner device in response to the detected change in the amount of fuel supplied so that the ratio of air to fuel is within an appropriate range. By performing correction control in this manner, even if the fuel supply nozzle of the burner device becomes constricted due to carbonization of residual fuel or intrusion of particulates in exhaust gas, the ratio of fuel discharged from the nozzle to combustion air can be maintained. Since the fuel can be kept properly at all times and the fuel can be reliably completely combusted, secondary air pollution caused by burner operation can be stably prevented over a long period of time.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and are shown in Figure 1 to Figure 4.
The figure shows the first embodiment.
The figure is an enlarged vertical sectional view of the burner device, and Figure 3 is an explanatory diagram of the main parts.
FIG. 4 is an explanatory diagram showing the control system, and FIG. 5 is an overall schematic explanatory diagram showing the second embodiment. DESCRIPTION OF SYMBOLS 1... Engine, 2... Exhaust passage, 6... Filter member, 4... Burner device, 10... Fuel supply nozzle, 10a
...Nozzle hole, 11..Discharge port, 13..Fuel pump,
14... Fuel supply passage, 16... Air supply passage, 17...
・Air pump, 18...Ignition switch, 20°...Check valve, 25...Clogging detector, 26.26'...Control device, 27...Burner device control circuit 1.51..., l
-IJ filter, 52...Pressure detector, '5'5...Solenoid valve, 67...Solenoid valve control circuit, 41.41
'...Fuel supply amount change detection means, 42.42'...Air supply amount control means, 44...+7 Leaf valve. = 19 −

Claims (1)

[Claims] +1) A diesel engine in which a filter member for collecting fine particles such as carbon particles in the exhaust gas is disposed in the exhaust passage, and a burner device for eliminating clogging of the filter member is disposed in the exhaust passage upstream of the filter member. In the exhaust purification device, there is provided a fuel supply amount change detection means for detecting a change in the amount of fuel supplied to the burner device, and an amount of combustion air to be supplied to the burner device according to an output of the fuel supply amount change detection means. 1. An exhaust gas purification device for a diesel engine, comprising air supply amount control means for controlling the ratio of fuel and air to a proper range.