JPS5874818A - Exhaust gas purifying device of diesel engine - Google Patents

Abstract

PURPOSE:To prevent wasteful consumption of a fuel by controlling a burner so that the burner generates the heat of necessary minimum quantity under consideration of the exhaust gas temperature and the exhaust gas flow quantity despite the operational state of an EGR, upon burning minute particles captured by a filter member. CONSTITUTION:When the loading of the filter member 9 arresting minute particles such as carbon particles and the like within exhaust gas proceeds, the electric resistance between a pair of electrodes 10 and 11 gradually decreases and the voltage difference exceeds the reference value. At that time, a signal S1 is generated from a loading detection circuit 28. Then, a current is supplied to an ignition heater 14d by this signal S1 through a control circuit 29, and adjusting valves 26a and 26b are opened and an air pipeline 16 and a fuel pipeline 18 to fire a burner 14 through diaphragm devices 22 and 23. Upon this occasion, in accordance with the output of a throttle valve opening degree senser 8, an engine rotational speed sensor 30 and an exhaust air temperature senser 31, the opening degree of each of valves 26a and 26b is controlled, and the burner fuel quantity is maintained at an optimum quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification device for a diesel engine in which an exhaust passage is provided with a filter member that collects particulate components such as carbon particles in the exhaust gas of a diesel engine, and more particularly, The present invention relates to an exhaust purification device used in a diesel engine, which eliminates clogging of a filter member by burning the collected components using a burner device.

The exhaust gas of a diesel engine contains many particulate components such as carbon particles, and it has been considered essential to remove these particulate components when purifying the exhaust gas of a diesel engine. Conventionally, as shown in Japanese Patent Laid-Open No. 49-71315, a conventional exhaust gas purification device for this purpose has a filter member disposed in the exhaust passage to collect the above-mentioned particulate components, and the collected components are The burner device is placed upstream of the filter member and burns it as appropriate to eliminate clogging of the filter member.
Things are known.

In the exhaust purification device as described above, the burner device is operated periodically or as appropriate when clogging of the filter member is detected by the clogging detection means. The above-mentioned scavenging component is generally heated at 580 to 600°C.
When heated to a certain degree, it burns out in a short period of about tens of seconds,
Clear the clogging of the filter part.

The heating temperature of the collected components naturally depends on the combustion strength of the burner device,
In other words, it depends on the amount of fuel supplied to the burner device, but in conventional devices, this fuel amount was fixed constant, so if the fuel amount is set low, the exhaust temperature will be low or If the burner device is activated and operated at high exhaust flow rates, it may occur that the captured components are not heated sufficiently and therefore are not completely burnt out. On the other hand, if the burner device is operated when the exhaust gas temperature is high or the exhaust gas flow rate is low, the collected components may become hotter than necessary. From the standpoint of eliminating clogging of the filter member, there is no problem if the collected components are heated more than necessary, but this causes more burner fuel to be consumed than necessary, which is extremely uneconomical. At the same time, exhaust system parts such as filter members are heated up and their lifespans are shortened.

Therefore the burner fuel quantity is above the exhaust flow rate.

If you control the amount to the optimum amount in response to the exhaust temperature,
An exhaust gas purification device that is economical and does not deteriorate exhaust system components can now be provided.

The above exhaust flow rate is for a general diesel engine.
It can be calculated by knowing the engine speed. On the other hand, today K is used to prevent knocking and reduce combustion noise.
Diesel engines that perform EGR (air recirculation) are also being considered, and the EAR rate is 20 to 3 at idling if the main purpose is to prevent knocking.
It is approximately 0%, but when the purpose is to reduce combustion noise, it can reach 80 to 90% under idle link conditions.

If the EGR rate is set at such a high level, it becomes completely impossible to know the correct exhaust flow rate based on the engine rotation speed, and it becomes impossible to correctly control the amount of burner fuel as described above.

The present invention has been made in view of the above circumstances, and is an EGR
In a diesel engine in which burner fuel is consumed, it is economical to completely burn out the trapped components of the filter member, and to control the amount of fuel discharged correctly so that burner fuel is not consumed more than necessary. The purpose of the present invention is to provide an exhaust gas purification device that provides excellent exhaust gas purification.

The exhaust gas purification device for a diesel engine of the present invention is provided with an exhaust gas recirculation passage for EGR. A filter member for collecting fine particles such as particles is provided, and a burner device for unclogging the filter member is provided in an exhaust passage upstream of the filter member and downstream of the opening. In an exhaust purification system for a diesel engine, there is an actuator that controls the amount of fuel for the burner, an exhaust recirculation amount detection device that generates an output corresponding to the amount of exhaust recirculation, and outputs from the engine speed sensor and exhaust temperature sensor. The present invention is characterized by comprising a control device that calculates the amount of fuel required for the burner device and controls the actuator, and also corrects the actuator control output based on the output from the exhaust gas recirculation amount detection device during exhaust gas recirculation. be.

In addition to the diesel engine exhaust purification device of the present invention having the above structure, the burner device is designed to heat the collected components to the required temperature and to burn the minimum amount necessary for complete combustion, taking into account the exhaust temperature and exhaust flow rate. Since burner fuel can now be supplied, the scavenging components will not remain unburned, and the deterioration of exhaust system parts will not be accelerated.

Moreover, consumption of excess burner fuel can also be suppressed. The exhaust flow rate is detected from the engine rotation speed, but when EGR is being performed, the burner fuel amount is corrected based on the exhaust recirculation amount detected by the exhaust recirculation amount detection device. Therefore, accurate burner fuel amount control can always be performed in accordance with the actual exhaust flow rate.

If a high rate of EQR is desired, the desired high EGR rate cannot be obtained by simply opening the exhaust gas recirculation passage wide, so a throttle valve is generally provided upstream of the exhaust gas recirculation passage opening in the intake passage to control air intake. By operating this throttle valve in the throttle direction, a higher EGR rate can be obtained. Therefore, the opening degree of this throttle valve corresponds to the EGR rate.

Therefore, the exhaust gas recirculation amount may be indirectly changed by detecting the opening degree of the throttle valve.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an exhaust purification device for a diesel engine according to one embodiment of the present invention.

An exhaust passage 2 and an intake passage 3 of the diesel engine 1 are connected by an exhaust recirculation passage 5 provided with a recirculation valve 4. The recirculation valve 4 is controlled by the F)OR control circuit 6, and is set to be fully closed when 1iGR is not required, but is opened when EGR is performed. A throttle valve 7 is provided in the intake passage 3 upstream of the opening of the exhaust gas recirculation passage. When the throttle valve 7 is operated in the throttle direction, the amount of air newly sucked into the intake passage 3 becomes smaller, so the EGR
rate will be higher. A throttle valve opening sensor 8 is connected to the throttle valve 7 to detect the opening of the throttle valve 7.

A honeycomb-shaped non-conductive filter member 9 is provided in the exhaust passage 2 at a position downstream of the opening of the exhaust gas recirculation passage 5.
is installed.

The member 9 of the film j has a large number of pores 9b formed by porous partition walls 98. One end of every other pore 9b is closed with a blind plug 9C, and the upstream end is open, and the exhaust gas flowing into the pore 9b passes through the porous partition wall 9a. and flows out into the pore 9b, which has an open downstream end. When the exhaust gas passes through the partition wall 9a,
Fine particles such as carbon particles contained in this exhaust gas are collected by the partition walls 9al/i. A pair of electrodes 10.11 are inserted into the filter member 9 in a direction perpendicular to its axis. It is fixed to the peripheral wall of the exhaust gas recirculation passage 5 on the upstream side of the filter member 9 and inserted into each partition wall 9a tightly, that is, without forming a gap between the partition wall 9a and the partition wall 9a. A burner 14 is disposed in the exhaust passage 2 on the downstream side of the opening.The burner 14 includes a primary air nozzle 14a, a secondary air nozzle 14b, a fuel nozzle 14C, and an ignition heater 14d. Air nozzles 14a and 2
Both of the secondary air nozzles 14b are connected to an air pipe 16 drawn from a discharge port of an air pump 15 that supplies combustion air. On the other hand, the fuel nozzle 14c is connected to the fuel pump 1.
It is connected to a fuel tank 19 that stores fuel F by a fuel pipe 18 with a fuel pipe 7 interposed therebetween. An orifice 20.21 is provided in each of the air pipe 16 and fuel pipe 18, and each orifice 20.21 includes a substantially conical needle 22b fixed to a diaphragm 22a, 23a of a diaphragm device 22.23, respectively. 23b is inserted. The diaphragm chambers 22C and 23C of these diaphragm devices 22 and 23 are connected to a main pipe 24 and a control air pipe 24a branched from the main pipe 24.
, 24b to the surge tank 25.

Control pulps 26a and 26b whose opening degrees can be adjusted are provided in the control air pipes 24a and 24b, respectively, and the suction side of a vacuum pump 27 is connected to the surge tank 25.

The aforementioned electrodes 10.11 are connected to a clogging detection circuit 28, and the output of this clogging detection circuit 28 is sent to a control circuit 29.
It is now entered into Also for diesel engine 1.

For example, a pulse generation type rotation sensor 30 and a temperature sensor 31 are provided in the exhaust passage 2, and the outputs of the rotation sensor 30, the temperature sensor 31, and the throttle valve opening sensor 8 are also controlled as described above. The signal is input to the circuit 29.

Hereinafter, the operation of the exhaust gas purification device of this embodiment having the above structure will be described.First, the recirculation valve 4 is closed and EQ)1 is performed.
Let's explain the case.

The electrical resistance between the pair of electrodes 10, 11 described above has a characteristic that when fine particles such as carbon particles adhere to the partition wall 9a of the filter member 9, the electric resistance decreases as the amount of the adhered fine particles increases. Therefore, for example, one electrode 10 (1
1) is connected to the anode of the battery through a resistor, while the cathode of the battery is connected to ground, and the other electrode 11 (1) is connected to the anode of the battery through a resistor.
0) is connected to ground, the voltage difference across the resistor increases in accordance with the increase in the amount of particles attached to the partition wall 9a. Therefore, here, a reference voltage generation circuit is provided which generates the same reference voltage as the voltage difference when fine particles are attached to a degree necessary to unclog the filter member 9 by burning the burner 14. If the reference voltage and the voltage difference are compared and an electric signal is generated when the voltage difference exceeds the reference voltage, the burner operation can be automatically started using this electric signal.

The i/clogging/clogging detection circuit 28 is configured as described above, and the filter member 9 is not activated to the extent that the burner operation is necessary.
When clogging progresses, a clogging detection signal S1 is sent to the control circuit 29.

When the clogging detection signal S1 is input, the control circuit 29
outputs an ignition signal S2 that energizes an immersion heater 14d consisting of an electric heater, and then outputs an ignition signal S2 that energizes an immersion heater 14d consisting of an electric heater, and then
Pulp opening signals S3 and S3/ are output. When the regulating pulps 26a and 26b are opened by the pulp opening signal S3.83', the diaphragm chambers 22C and 23C of the diaphragm device 22 and the chamber 3 are communicated with the surge tank 25 maintained at negative pressure by the vacuum pump 27. , each diaphragm A22a, 23a is connected to the return spring 2.
2d and 23d and is pulled to the right in the figure. Therefore, the needles 22b and 23b fixed to these diaphragms 22a and 23a exit to the right from the orifice 20.21 in which they had been fitted, open the air pipe 16 and the fuel pipe 18, respectively, and open the air pipe 16 and fuel pipe 18, respectively. The combustion air and fuel F are supplied to the combustion chambers 14 and 14, respectively.

Here, the above-mentioned pulp opening signals S3 and S31 are not constant signals, but are changed depending on the exhaust temperature signal S4 from the temperature sensor 31 and the rotation speed signal S5 from the rotation sensor 30.

When EGR is not being performed, the rotational speed of the engine 1 corresponds to the exhaust flow rate. Therefore, the control circuit 29 uses this rotational speed signal S5 as a signal representing the exhaust flow rate, determines that the higher the engine rotational speed is, the larger the exhaust flow rate is, and changes the pulp opening signal S3.83' to increase the pulp opening degree. Further, this control circuit 29 receives the exhaust gas temperature signal S4 from the temperature sensor 31, and changes the pulp opening signal S3.83' toward a larger valve opening as the exhaust gas temperature becomes lower. The larger the opening degree of the regulating pulps 26a, 26b, the larger the amount of negative pressure applied to the diaphragm chambers 22c, 23C, and the larger the exit amount of the needles 22b, 23b. Therefore, the opening area of the orifice 20.21 increases. and combustion air amount,
The amount of fuel is increased.

Here, in the air supply system such as the pulp open signal S3, air pump 15, and diaphragm device 22, and in the fuel supply system such as the pulp open signal 83', fuel pump 17, and diaphragm device 23, the amount of combustion air is the weight relative to the amount of fuel. 1.2 to 2.5 in ratio
It is set to be approximately double that. By setting in this way, it is possible to prevent generation of unburned gas due to insufficient combustion air or non-ignition due to excess combustion air. And the amount of fuel is determined by the burner 14 under the given exhaust temperature and exhaust flow rate.
is set to heat the particulates collected in the filter member 9 to a predetermined temperature at which they are completely burned out, for example 600°C, and to generate the minimum amount of heat necessary to completely burn them out. Ru. Therefore, the exhaust temperature is 1. No matter how the exhaust flow rate varies, the trapped particulates are completely burned out, and no fuel is wasted to the extent that the burner generates more heat than necessary.

When the recirculation valve 4 is opened by the EGR control circuit 6 and EGR is performed, the exhaust flow rate will be lower than when EGR is not performed.
Naturally, it decreases under the same engine speed. therefore,
When the throttle valve 7 is operated to perform EGR, the throttle valve opening signal S6 output from the throttle valve opening sensor 8 is input to the control circuit 29, and the throttle valve opening signal S6 generates a pulp opening signal S3.83. ' is corrected in the direction of decreasing pulp opening.

Here, the degree of decrease in the exhaust flow rate compared to the case where EGR is not performed is, of course, remarkable when the EGR rate is high. This EGR rate is increased by operating the throttle valve 7 in the throttle direction. Therefore, using this throttle valve opening signal S6, when the throttle valve opening is /J%, that is, when the EGR rate is high, the above correction amount is increased, and when the throttle valve opening is large, that is, when the EGR rate is low, the above correction amount is increased. Control is performed to reduce the By performing such a correction when performing EGR, accurate burner fuel amount control can always be performed in accordance with the actual exhaust flow rate.

The above-mentioned pulp open signal S3.83' is the ignition signal S
2 is sent to the ignition heater 14d, then the ignition heater 14d
If it is made to emit after detecting that the fuel F has been heated enough to ignite, for example, about 9000C, then
Secondary pollution due to unburned gas released from the burner 14 can be prevented. Also, when the burner 14 stops operating, if the pulp open signal S3.83' is changed to a fully closed signal and the supply of combustion air and fuel is cut off, then the ignition signal S2 is cut off. Contamination is prevented.

Further, since the clogging by the burner 14 does not need to be carried out immediately after the clogging is detected by the clogging detection circuit 28, the rotation sensor 30 detects the idling state and the idling state is detected by the rotation sensor 30. Burner 14
It is preferable to operate. Since the exhaust flow rate is stable under idle link, there is an advantage that burner control is easy. In addition, clogging of the filter member 9 can be detected by methods other than the above-mentioned method of observing changes in interelectrode resistance.
For example, this may be carried out by observing changes in the pressure difference between the upstream side and the downstream side of the filter member 9.

FIG. 2 is a flowchart showing the flow of signals when the apparatus described above is controlled by a computer. As generally indicated in the flowchart of FIG.
In addition to detecting the opening degree of the throttle valve 7 as in the above embodiment, the GR amount can also be detected using various outputs of a device that controls EGR.

The flow rate control of the fuel F and the combustion air can be carried out using various known devices other than the device shown in FIG. Needless to say, the fuel amount may be controlled by using a device for adjusting the amount of fuel, or the amount of fuel may be directly controlled by a regulating pulp 26c disposed in the fuel pipe 18, as shown in FIG. 3, for example.

The regulating pulp 26C, the regulating pulps 26a, 26b, etc. used in the embodiment shown in FIG. It may also be something that controls. In this Fig. 3, some parts that are the same as those in the device shown in Fig. 1 are omitted, and the numbers and symbols in Fig. 1 are used for parts and signals that are equivalent to those in Fig. 1 even in the illustrated structure. However, duplicate explanations will be omitted. In addition, in this FIG. 3, the structure of the control circuit 29 is shown in detail. That is, the control circuit 29 includes a clogging determination section 40 and a heater control section 4.
1. Consists of an exhaust flow rate correction section 42, a fuel control section 43, and a combustion air control section 44, such as an EGR control section such as a throttle valve in an intake passage.
The EGR amount signal 86' from the control device 45 is input to the exhaust flow rate correction section 42, and the rotation speed signal S5 from the rotation sensor 30 is corrected to correspond to the actual exhaust flow rate under EGR execution. Since this corrected signal is now input to the fuel control unit 43, the pulp open signals S3 and Sa
' is corrected as described above.

As explained in detail above, in the diesel engine exhaust purification device of the present invention, when the burner device burns the particulates collected on the filter member, the burner device always maintains the exhaust gas temperature regardless of whether EGR is performed or not. Since the exhaust flow rate can be controlled to generate the minimum necessary amount of heat, wasteful consumption of burner fuel can be suppressed and it is extremely economical. It does not cause deterioration of parts, and on the other hand, it does not leave particulates unburned (its practical value is extremely high).

[Brief explanation of drawings]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing one embodiment of the present invention.
FIG. 3 is a flowchart showing the flow of control in the embodiment shown in the figure. FIG. 3 is a system diagram showing a different embodiment of the present invention. 1...Diesel engine 2...Exhaust passage 5...
・Exhaust recirculation passage 7... Throttle valve 8... Throttle valve opening sensor 9... Filter member 14... Burner 16... Air pipe 18... Fuel pipe
20, 21... Orifice 22, 23... Diaphragm device 26a, 26b, 26c --- Adjustment Harz 2
9... Control circuit 30... Rotation sensor 31...
Temperature sensor 45...EGR control device S3.83
'... Pulp open signal S6... Throttle valve opening signal S
6'...EGR amount signal

Claims (1)

[Scope of Claims] l) A filter member for collecting fine particles such as carbon particles in the exhaust gas is disposed in the exhaust passage downstream of the opening of the exhaust gas recirculation passage of a diesel engine provided with the exhaust gas recirculation passage. In the exhaust purification device for a diesel engine, the exhaust gas purification device for a diesel engine is provided with a burner device for eliminating clogging of the filter member in an exhaust passage upstream of the filter member and downstream of the opening. an actuator that controls the exhaust gas recirculation amount, an exhaust gas recirculation amount detection device that generates an output corresponding to the amount of exhaust gas recirculation, and the amount of fuel required for the burner device is calculated based on outputs from the engine rotation speed sensor and the exhaust temperature sensor to control the actuator. An exhaust gas purification device for a diesel engine, comprising: a control device that corrects the output of the actuator control according to the output from the exhaust gas recirculation amount detection device when the exhaust gas is recirculated. 2) The diesel engine according to claim 1, wherein the exhaust gas recirculation amount detection device is constituted by a throttle valve opening sensor that detects the opening of a throttle valve provided in an intake passage. Engine exhaust purification device.