JPS5872611A - Exhaust gas purifier of diesel engine - Google Patents

Abstract

PURPOSE:To completely burn a collected component in a filter member further prevent deterioration of an exhaust system part, caused from excessively unnecessary consumption of burner fuel, by variably supplying a fuel quantity to a burner device. CONSTITUTION:A control circuit 23, in which the higher the speed of an engine, the larger the flow of exhaust is decided to change an opening signal S3 of a fuel regulating valve 20 to the direction of larger valve opening, further the lwoer the exhaust temperature, to the larger opening direction the valve opening signal S3 is changed by an exhaust temperature signal S4 from a temperature sensor 25, is provided. Then a fuel quantity, supplied to a burner device 8, is constituted variable. For instance, if an opening of the regulating valve 20 is increased, a level of negative pressure, applied to chambers 16c, 17c in a diaphragm device 16, is increased, and needles 16b, 17b are more retracted. As a result, opening area of orifices 14, 15 is increased, then quantities of fuel air and fuel can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust 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. By burning the collected components using a Parnall device, the clogging of the filter member was eliminated. This invention relates to an exhaust gas purification device.

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

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,
Clogging of the filter member is eliminated.

The heating temperature of the scavenging and collecting components naturally depends on the intensity of combustion in the burner device, that is, the amount of fuel supplied to the burner device, but in conventional devices, this amount of fuel was fixed, so the amount of fuel If the burner device is activated when the exhaust gas temperature is low or the exhaust gas flow rate is high, the captured components may not be sufficiently heated and therefore 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 components, there is no problem if the collected components are heated more than necessary, but this causes burner fuel to be consumed more than necessary, which is extremely uneconomical and also prevents the filter from clogging. Exhaust system parts such as certain parts may become hot and deteriorate.

The present invention has been made in view of the above circumstances, and it is possible to completely burn out all of the collected components of the filter member, and also to prevent the burner fuel from being consumed more than necessary and causing deterioration of the exhaust system parts. The purpose is to provide a complete exhaust purification device for diesel engines.

The exhaust purification device for a diesel engine according to the present invention includes the above-mentioned exhaust purification device, that is, a filter member for collecting all fine particles such as carbon particles in the exhaust gas, which is disposed in the exhaust passage, and a filter member upstream of the filter member. In an exhaust purification system for a diesel engine that is equipped with a burner device in the exhaust passage to eliminate clogging of filter components, there is an exhaust flow rate detection device that generates a full output corresponding to the exhaust flow rate, and an exhaust temperature detection device that detects the exhaust temperature. A sensor, an actuator and an eater that control the amount of fuel for the burner, a burner combustion air supply device that supplies safe burner combustion air according to the amount of fuel for the burner, and the exhaust flow rate detection device and the exhaust temperature sensor. According to the output, the burner [and a control device that calculates a safe fuel amount and controls the operation of the actuator are provided.

In the diesel engine exhaust purification device of the present invention having the above structure, the toner device heats the collected components to the lowest temperature, taking into account the exhaust temperature and exhaust flow rate, and removes the minimum amount necessary for complete combustion. Since a limited amount of burner fuel can be supplied, the collected components will not remain unburned, and consumption of excess burner fuel can also be suppressed.

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.

A honeycomb-shaped non-conductive filter member 3 is disposed in an exhaust passage 2 of a diesel engine 1 without a throttle half. Filter member 3, porous partition wall 3a
A large number of pores 3b are formed by this. The ends of every other pore 3b are changed, and one end of each is closed with a blind plug 3c, and the upstream end is open.
The exhaust gas flowing into the chamber passes through the porous partition wall 3ai and flows out into the pore 3b having an open downstream end. Exhaust is from partition wall 3a
During the entire passage, fine particles such as carbon particles contained in the exhaust gas are collected by the partition wall 3a. The filter member 3Vc has a pair of electrodes 4,
5 has been inserted. These electrodes 4 and 5 are fixed to the peripheral wall of the filter member 30 via insulating members 6 and 7, respectively, and are inserted into each partition wall 38 tightly, that is, without forming a gap between them and the partition wall 3a. ing. A bar 8 is disposed in the exhaust passage 2 upstream of the filter member 3. This burner 8 consists of a primary air nozzle 8a, a secondary air nozzle 8b, a fuel nozzle 8c, and an ignition heater 8d. Both the primary air nozzle 8a and the secondary air nozzle 8b are connected to an air pipe 1o drawn from the discharge LPJO of an air pump 9 that supplies combustion air. On the other hand, the fuel nozzle 8c is connected to a fuel tank 13 that stores fuel F through a fuel pipe 12 in which a fuel pump 11 is installed. An orifice 14.15 is provided in each of the air pipe 1o and fuel pipe 12, and each orifice 14.15 has a substantially conical knee fixed to a diaphragm 16a, 17a of a diaphragm device 16.17, respectively. The diaphragm devices 16b and 17b are inserted through the diaphragm devices 16b and 17b.
．． The 17 diaphragm chambers 16c and 17c are connected to the piping 18a.
, 18b, and the control air piping 18 where these pipings are merged.
It is connected to the reserve tank 19 via. A control valve 20 whose opening degree can be adjusted is provided in the control air pipe 18, and the suction side of a vacuum pump 21 is connected to the surge tank 19.

The aforementioned electrode 4.5 is connected to a clogging detection circuit 22, and the output of this clogging detection circuit 22 is input to a control circuit 23. Further, the diesel engine 1 is provided with, for example, a pulse generation type rotation sensor 24 and a temperature sensor 25 in the exhaust passage 2, and the outputs of these rotation sensor 24 and temperature sensor 25 are also input to the control circuit. It has become so.

The operation of the exhaust gas purification device of this embodiment having the above structure will be explained below.

The electrical resistance between the pair of electrodes 4.5 described above has a characteristic that when fine particles such as carbon particles adhere to the partition wall 3a of the filter member 3, the electric resistance decreases as the amount of the adhered fine particles increases.

Therefore, for example, if one electrode 4 (5) is connected to the anode of a battery through a resistor, while the cathode of the battery is connected to ground, and the other electrode 5 (4) is connected to ground, both ends of the resistor The voltage difference increases as the amount of particles attached to the partition wall 3a increases. Therefore, here, a reference voltage generation circuit is provided which generates the same reference voltage as the voltage difference mentioned above when fine particles are attached to the extent necessary to unclog the filter member 3 by burning the burner 8. 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 clogging detection circuit 22 is configured as described above, and when the filter member 30 becomes clogged to the extent that burner operation is required,
A clogging detection signal S1 is sent to the control circuit 23.

When the clogging detection signal S1 is input, the control circuit 23 outputs an ignition signal S2 that energizes the ignition heater 8d, which is an electric heater, and then outputs a pulp opening signal S3 that opens the regulating pulp 20. When the regulating pulp 20 is opened by the pulp opening signal S3, the diaphragm device 16
．． The 17 diaphragm chambers 16c and 17c are communicated with the surge tank 19 maintained at negative pressure by the vacuum pump 21, and the diaphragm chambers 16a and 17a are
is pulled to the right in the figure against the return springs 16d and 17d. Therefore, the needles 16 b and 17 b fixed to the diaphragms 16 a and 117 a exit to the right from the orifices 14.15 in which they had been fitted, open the air pipe 10 and the fuel pipe 12, respectively, and supply the burners 8 with the needles 16 b and 17 b, respectively. Supply air and fuel F for combustion.

Here, the above-mentioned pulp opening signal S3 is not a constant signal, but can be varied depending on the exhaust temperature signal S4 from the temperature sensor 25 and the rotation speed signals S5 and 1 from the rotation sensor 24.

Since the diesel engine 1 of this embodiment does not have a throttle valve, the rotation speed of the engine 1 corresponds to the exhaust flow rate. Therefore, the control circuit 23 uses this rotational speed signal S5.
is used as a signal representing the exhaust flow rate, and it is determined that the higher the engine speed is, the larger the exhaust flow rate is, and the pulp opening signal S3 is
is changed in the direction of larger valve opening. Also, this control circuit 2
3 changes the pulp opening signal S3 toward a larger pulp opening degree as the exhaust gas temperature becomes lower, based on the exhaust gas temperature signal S4 from the temperature sensor 25. The greater the opening degree of the regulating pulp 20, the greater the amount of negative pressure applied to the diaphragm chambers 16c, 17c, and the greater the withdrawal amount of the needles 16b, -17b. Therefore, the opening area of the orifice 14.1.5 is increased, and the amount of combustion air and fuel are increased.

Here, in the air supply system such as the air pump 9 and the diaphragm device 16, and the fuel supply system such as the fuel pump 11 and the diaphragm device 17, the amount of combustion air is 1.5% by weight relative to the amount of fuel.
It is set to be about 2 to 2.5 times. 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. The amount of fuel is determined by the burner 8 heating the particulates collected in the filter member 3 to a predetermined temperature, e.g. 600°C, at a given exhaust temperature and exhaust flow rate to ensure complete combustion. What to do: Set to generate the minimum amount of heat necessary. Therefore, no matter how the exhaust temperature and exhaust flow rate fluctuate, the collected particulates will be completely burned out, and the fuel will not be wasted to the extent that the burner generates more heat than it needs.

The above-mentioned pulp open signal S3 is generated after the ignition signal S2 is sent to the ignition heater 8d.
If the burner 8 is emitted after detecting that it has been heated to a temperature sufficient to ignite, for example, about 900° C., secondary contamination due to unburned gas released from the burner 8 can be prevented.

Also, when the burner 8 stops operating, the pulp
-l・-Jinko S--fu^C no-" and then, +j
After the fuel supply is cut off, the ignition signal 8
By cutting off 2f, similar secondary contamination can be prevented.

Further, since the burner 8 does not need to be removed immediately after the clogging detection circuit 22 detects the clogging, the rotation sensor 24 detects the shear link state and Preferably, the burner 8 is activated under the drink. Since the exhaust flow rate is stable under idle link, there is an advantage that burner control is easy. Furthermore, clogging of the filter member 30 can be detected by a method other than the method of detecting from the change in inter-electrode resistance as described above, such as a method of detecting from a change in the pressure difference between the upstream side and the downstream side of the filter member 3. It may be done.

In the embodiment described above, since the diesel engine is not provided with a throttle valve, the engine rotational speed signal is used as it is as a signal representing the exhaust flow rate. As shown in FIG. 2, in the installed diesel engine, the throttle opening signal S6f is inputted from the throttle opening detection means 32 to the control circuit 31, and the valve opening signal S3'l S3''k is corrected by the throttle opening. Further, as shown in FIG. 2, the flow rate control of the fuel F or combustion air may be directly controlled by the control valve 2σ without using the diaphragm device 17i of the embodiment shown in FIG. This control valve 20
Alternatively, the control valve 20 of the embodiment shown in FIG. 1 may control the flow rate by fully adjusting the opening degree, or may control the flow rate by fully changing the opening time. In this Figure 2, the same components as those in the device in Figure 1 are omitted, and even in the illustrated configuration, the numbers and symbols in Figure 1 are used for parts and signals that are equivalent to those in Figure 1. The same thing as ``fc'' is attached, and the redundant fc explanation is omitted.

Note that oxygen that has not been used for combustion in the engine remains in the exhaust gas, and this residual oxygen can be used for burner combustion when the burner is combusted. Therefore, when it is necessary to strictly control the ratio between the amount of fuel and the amount of combustion air, it is preferable to perform control that also takes this residual oxygen into consideration. The embodiment shown in Fig. 3 is an example of an exhaust purification device that controls the supply amount of combustion air by taking into consideration the amount of residual oxygen in the exhaust gas. What is the signal flow when controlling the entire exhaust purification system by computer? FIG. In this Fig. 3, some of the same configurations as those already explained are omitted, and parts and signals equivalent to those in Fig. 1 or 2 are given the same numbers and symbols, and explanations are redundant. Omit. In the exhaust passage 2 upstream of the burner 8,
For example, an α sensor 40 is provided to measure the total oxygen concentration in the exhaust gas.

The oxygen concentration signal S7 from this 04 segisa 40 is
The combustion air control section 42 of the control circuit 41 is operated manually. In addition to this combustion air control section 42, the control circuit 41 also includes a fuel control section 4.
3. Consists of a heater control section 44. Clogging detection circuit 22
The clogging detection signal S1 from the heater control section 44
The heater control section 44 outputs an ignition signal S2. The fuel control unit 43 receives the clogging detection signal S.
xi, the control valve 2σ in the fuel pipe 12 is opened and the fuel control unit 4 outputs an open signal S3'i.
3 calculates the required amount of fuel from the rotation speed signal S5 from the rotation sensor 24 and the exhaust temperature signal S4 from the temperature sensor 25, and determines the valve opening signal 83'f so that this required amount of fuel is obtained. Valve opening signal 8 that determines the amount of fuel
3' is also input to the combustion air control section 42, and from this combustion air control section 42, a valve opening signal is sent to operate the valve 20 so that the optimum amount of combustion air is supplied to the valve 20. 33+1 is output. Here, as mentioned above, this combustion air control section 42 has the above-mentioned no.
The oxygen concentration signal S7 from the second sensor 40 is input, and the valve open signal 5311 is set to a value that is supplied to all burners 8 with a corrected air amount obtained by correcting the safe air amount directly calculated from the fuel amount using the oxygen concentration. . In other words, when residual oxygen is contained in the exhaust gas, this residual oxygen is used for combustion in the burner 8, so the amount of combustion air supplied to the burner 8 by the air pump 9 is lower than the safe air amount calculated from the amount of fuel. Less is enough. Of course, the higher the residual oxygen concentration in the exhaust gas, the less combustion air is sent from the air pump 9 to the burner 8. Therefore, the combustion air control section 42 adjusts the valve opening signal 5311 in accordance with the residual oxygen concentration. The amount of correction can be changed.

Furthermore, the exhaust purification device of the present invention extracts a signal indicating the supercharging state from the supercharger even in a diesel engine where supercharging is performed, and uses this signal to appropriately correct the valve opening signal, thereby adjusting the actual exhaust flow rate. It is possible to perform accurate burner fuel amount control according to the Also,
In the above embodiment, a configuration is shown in which air and fuel are each supplied independently to the burner, but a configuration may be adopted in which the amount of air-fuel mixture is controlled according to the total exhaust flow rate and exhaust temperature, such as in a carburetor system.

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 Since it can be controlled to generate a limited amount of heat, wasteful consumption of burner fuel is suppressed and it is extremely economical.It also does not cause deterioration of exhaust system parts due to high temperatures, and at the same time prevents particulates from burning. There will be no leftovers, and its actual value is enormous.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, Fig. 2 is a system diagram showing a different embodiment of the invention, Fig. 3 is a system diagram showing still another embodiment of the invention, Fig. 4 3 is a flowchart showing the flow of control in the embodiment of FIG. 3. FIG. l...Diesel engine 2...
Exhaust passage 3...Filter part
8...Bass 10...Air piping 12...Fuel piping 14, 15...Orifice 16.17...Diaphragm device 20.
20'...Adjustment valve 23, 31.41...Control circuit 24...Rotation sensor 25...Temperature sensor Sa, S'3', 83''...Valve open signal F・・・・・・Fuel
′−−−□−−−” Hesuna N(J ~

Claims (1)

[Claims] 1) A filter member that collects fine particles such as carbon particles in the exhaust gas is disposed in the exhaust passage, and the filter member is installed in the exhaust passage upstream of the filter member to prevent clogging of the filter member. An exhaust gas purification device for a diesel engine equipped with a burner □ device that eliminates the problem, includes an exhaust flow rate detection device that generates an output corresponding to the exhaust flow rate, and an exhaust temperature sensor that detects the exhaust temperature. An actuator that controls the amount of fuel for the burner, a burner combustion air supply device that supplies necessary burner combustion air according to the amount of fuel for the burner, and an output from the exhaust flow rate detection device and the exhaust temperature sensor to control the burner device. Required fuel f1
1. An exhaust purification device for a diesel engine, comprising: a control device that calculates and controls the operation of the actuator; 2) The exhaust gas purification device for a diesel engine according to claim 1, wherein the exhaust flow rate detection device includes a rotation sensor that detects the rotation speed of the engine.